JP2014043075A - Ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shearing mode type ink jet head in which a front end face of a partition wall comprising a piezoelectric material is joined to a nozzle plate and which enables improvement of liquid droplet speed and stable operation at high speed by suppressing an effect of vibration energy during deformation operation that concentrates on the front end face of the partition wall.SOLUTION: An ink jet head 1 includes: a head chip 10 in which a plurality of channels 12 and a plurality of partition walls 13 at least partially including piezoelectric materials are juxtaposed alternately and which applies pressure for discharge to ink within the channels 12 by deformation operation of the partition walls 13 based on the drive voltage; and a nozzle plate 20 joined to a front end face of the head chip 10 via an adhesive. The front faces of the partition walls 13 and the nozzle plate 20 are arranged opposite to each other via the adhesive. The nozzle plate 20 includes air groove portions 23 that are located at positions opposite to the front end faces of the partition walls 13 on the joined face to the head chip 10 and are recessed from the joined face.

Description

  The present invention relates to an inkjet head, and more specifically, a shear mode type in which a channel and an end face of a partition made of a piezoelectric material are alternately arranged in parallel on a front end face of a head chip, and a nozzle plate is joined to the front end face of the head chip. The present invention relates to an inkjet head.

  An ink jet head that records and forms an ink jet image by discharging fine droplets from nozzles and landing on various recording materials is required to have a performance that can be stably driven at a higher speed.

  In an inkjet head, channels and partition walls made of a piezoelectric material are alternately arranged in parallel, and a drive voltage is applied to an electrode formed on the partition surface facing the channel so that the partition walls are cut based on the drive voltage. There is known a shear mode type inkjet head that is deformed into a letter shape and discharges ink in a channel from a nozzle, and the present inventor can stably drive at higher speed even in such a shear mode type inkjet head. Therefore, paying attention to the deformation operation of the partition during discharge, the factors that hinder the smooth deformation operation were studied.

  In general, in a shear mode type ink jet head in which channels and partition walls made of a piezoelectric material are alternately arranged, one end of a channel 101 is opened on a front end surface 100a of a head chip 100, and this front end surface is shown in FIG. When the head chip 100 is viewed from 100a, the opening 101a of the channel 101 and the front end face 102a of the partition wall 102 are alternately arranged. A nozzle plate 200 having a nozzle 201 formed at a position corresponding to the channel 101 is bonded to the front end surface 100 a of the head chip 100 via an adhesive 300.

  FIG. 12 is a view of the head chip 100 shown in FIG. 11 as viewed from the front end face 100a side. When a predetermined drive voltage is applied to electrodes (not shown) formed on both surfaces of the partition wall 102, the partition wall 102 is deformed from a neutral state indicated by a broken line to a square shape as indicated by a solid line based on the drive voltage. It operates to apply pressure for ejecting from the nozzle 201 to the ink in the channel 101. Since the deformation operation of the partition wall 102 is actually performed in a very short time, it can be regarded as vibration of the partition wall 102.

  Here, the front end surface 102a side of the partition wall 102 to be joined to the nozzle plate 200 is in a state of being completely fixed to the nozzle plate 200 by the adhesive 300 in order to prevent ink leakage between the channels 101. The vibration energy at the time of the deformation operation of the partition wall 102 is concentrated on this fixing portion. Since the vibration energy concentrated on the fixed portion has no escape, it propagates in reverse from the front end face 102a toward the central portion of the partition wall 102, affecting the deformation operation when the same partition wall 102 performs the next discharge operation. End up. As a result, the smooth deformation operation of the partition wall 102 is hindered, leading to a drop in the droplet velocity, and there is a problem that it is difficult to drive stably particularly when high frequency driving is performed.

  The nozzle plate material is made of synthetic resin such as polyimide, metal such as Ni, Cu, Si, glass, etc., as long as it adheres to the front end face of the partition and adheres to the front end face However, the harder the nozzle plate, the harder it is to absorb the vibration energy concentrated on the front end face of the partition wall, so it is generally harder than the nozzle plate made of synthetic resin. The problem is particularly noticeable when the nozzle plate is made of a metal, Si, or glass.

  In view of this, the present inventor studied to process the nozzle plate in order to suppress the influence of vibration energy during the deformation operation concentrated on the front end face of the partition wall bonded to the nozzle plate.

  Conventionally, as a technique for processing a nozzle plate, Patent Document 1 describes that a plurality of thin pressure fluctuation buffer portions for buffering pressure fluctuations of an ink reservoir are formed on an ink discharge surface of a nozzle plate. ing.

  Patent Document 2 describes that a slit for controlling the deformation of the substrate to prevent the separation of the nozzle plate is formed at the same depth as the nozzle plate on the ink ejection surface of the nozzle plate. Yes.

  Further, in Patent Document 3, a flow path plate, an intermediate plate, and a nozzle plate are laminated, and a vibration plate that vibrates by driving a piezoelectric material on one wall surface located on the side opposite to the nozzle plate in a chamber that is a pressure generating chamber. In the ink jet head described above, it is described that an air trap portion for preventing crosstalk is formed between the chambers of each plate.

  However, the techniques described in Patent Documents 1 to 3 are not concentrated on the front end face of the partition wall that is joined to the nozzle plate in the shear mode type inkjet head, rather than the shear mode type inkjet head that drives the partition wall made of a piezoelectric material. In order to suppress the influence of vibration energy during the deforming operation, a technique for processing the nozzle plate is not disclosed.

Japanese Patent Laid-Open No. 2005-14618 JP 2007-33145 A JP 2011-25657 A

  As a result of earnestly examining the above problems, the present inventor has formed an air groove portion on the joint surface of the nozzle plate with the front end surface of the partition wall, thereby reducing the influence of vibration energy during the deformation operation concentrated on the front end surface of the partition wall. The inventors have found that it can be suppressed, and have reached the present invention.

  That is, according to the present invention, in the shear mode type inkjet head in which the front end face of the partition wall made of a piezoelectric material is joined to the nozzle plate, by suppressing the influence of vibration energy during the deformation operation concentrated on the front end face of the partition wall, It is an object of the present invention to provide an ink jet head capable of improving the droplet speed and stably driving at high speed.

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

  The above problems are solved by the following inventions.

1. A head chip in which a plurality of channels and a plurality of partition walls containing a piezoelectric material at least in part are alternately arranged, and a pressure for discharging is applied to the ink in the channels by a deformation operation of the partition walls based on a driving voltage; An inkjet head having a nozzle plate joined to the front end face of the head chip via an adhesive, wherein the front end face of the partition wall and the nozzle plate are opposed to each other via an adhesive;
The ink jet head, wherein the nozzle plate has an air groove portion recessed from the joint surface at a position facing a front end surface of the partition wall of the joint surface with the head chip.

  2. 2. The ink jet head according to claim 1, wherein the air groove portion is provided along a height direction of the partition wall.

  3. 3. The ink jet head according to 2, wherein the air groove portion is longer than a height dimension of the channel on a front end surface of the head chip.

4). The nozzle plate is provided with a liquid chamber having a larger diameter than the nozzle in communication with the nozzle on the joint surface with the head chip.
4. The ink jet head according to 1, 2, or 3, wherein the depth of the air groove is equal to or shallower than the depth of the liquid chamber.

  5. 5. The ink jet head according to any one of 1 to 4, wherein the nozzle plate and the head chip are bonded in a state where the adhesive partially enters the air groove portion.

  6). The inkjet head according to any one of 1 to 5, wherein the nozzle plate is made of Si, metal, or glass.

  According to the present invention, in the shear mode type inkjet head in which the front end face of the partition made of piezoelectric material is joined to the nozzle plate, it is possible to suppress the influence of vibration energy during the deformation operation concentrated on the front end face of the partition. In addition, it is possible to provide an ink jet head capable of improving the droplet velocity and being stably driven at a high speed.

(A) is a perspective view showing an example of a shear mode type ink jet head according to the present invention in a partial cross-section, and (b) is a longitudinal cross-sectional view thereof. The figure which looked at the ink jet head concerning the present invention from the nozzle side The figure which expands and partially shows the cross section which follows the (iii)-(iii) line | wire in FIG. The figure which shows the other aspect of an air groove part (A)-(d) is a figure explaining an example of the manufacturing method of the nozzle plate of the inkjet head which concerns on this invention. (A)-(e) is a figure explaining an example of the manufacturing method of the nozzle plate of the inkjet head which concerns on this invention. The figure which looked at the inkjet head which concerns on other embodiment of this invention from the nozzle surface. The figure which looked at the inkjet head which concerns on other embodiment of this invention from the nozzle surface. The figure which looked at the inkjet head which concerns on other embodiment of this invention from the nozzle surface. A diagram explaining a comparative example Partial sectional view of a conventional shear mode type inkjet head The figure explaining the deformation | transformation operation | movement of a partition using the conventional shear mode type inkjet head

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

  1A and 1B show an example of a shear mode type ink jet head, in which FIG. 1A is a perspective view showing a part of the ink jet head, and FIG. 1B is a cross-sectional view thereof.

  In the ink jet head 1, reference numeral 11 denotes a channel substrate. On the channel substrate 11, a plurality of narrow groove-like channels 12 and a plurality of partition walls 13 are arranged in parallel so as to be alternately arranged. On the upper surface of the channel substrate 11, a cover substrate 14 is provided so as to cover all the channels 12, thereby forming the head chip 10.

  The nozzle plate 20 is bonded to the front end surface 10a of the head chip 10 (the end surface facing the ink ejection direction in the head chip 10) via an adhesive. One end of each channel 12 communicates with the outside via a nozzle 21 formed in the nozzle plate 20. In this nozzle plate 20, the surface of the nozzle plate 20 facing the direction in which ink is ejected from the nozzles 21 is the nozzle surface, and the opposite surface is the bonding surface 20 a with the head chip 10.

  The front end surface 13 a of each partition wall 13 in the head chip 10 is arranged flush with the front end surface 10 a of the head chip 10. Therefore, the front end surface 13a of each partition wall 13 and the joint surface 20a of the nozzle plate 20 are opposed to each other via the adhesive.

  The other end of each channel 12 gradually becomes a shallow groove with respect to the channel substrate 11, and communicates with a common flow path 15 common to each channel 12 formed in the cover substrate 14. The common flow path 15 is further closed by a plate 16, and ink is supplied from an ink supply pipe 18 into the common flow path 15 and each channel 12 through an ink supply port 17 formed in the plate 16.

  Each partition wall 13 is formed of a piezoelectric material such as PZT which is an electrical / mechanical conversion means. Here, the upper wall portion 131 and the lower wall portion 132 are both made of a piezoelectric material that is polarized, and the upper wall portion 131 and the lower wall portion 132 have the polarization directions opposite to each other. The portion formed by the piezoelectric material subjected to the polarization treatment may be, for example, only the portion denoted by reference numeral 131 and may be included in at least a part of the partition wall 13. The partition walls 13 are arranged alternately with the channels 12. Accordingly, one partition wall 13 is shared by the adjacent channels 12 and 12.

  In each channel 12, drive electrodes (not shown) are formed from the wall surfaces of both partition walls 13, 13 to the bottom surface of the channel 12, and a predetermined drive is applied to the drive electrodes on both surfaces sandwiching the partition wall 13. When a voltage is applied, the partition wall 13 is deformed into a letter shape with the joint surface between the upper wall portion 131 and the lower wall portion 132 as a boundary based on this driving voltage. Due to the deformation operation of the partition wall 13, a pressure wave is generated in the channel 12, and pressure for ejecting from the nozzle 21 is applied to the ink in the channel 12.

  Next, the nozzle plate 20 will be further described with reference to FIGS. 2 is a view of the inkjet head 1 as seen from the nozzle surface side, and FIG. 3 is a cross-sectional view taken along line (iii)-(iii) in FIG.

  In the present invention, a material generally used as a nozzle plate can be used for the nozzle plate 20, and examples thereof include those made of synthetic resin, Si, metal, or glass. Particularly preferred is a nozzle plate made of Si, metal or glass. Since these are harder than the nozzle plate made of synthetic resin, the vibration energy concentrated on the fixing portion between the partition wall 13 and the nozzle plate 20 is difficult to escape during the deformation operation of the partition wall 13, and the vibration concentrated on this fixing portion. Energy has a great influence on the next deformation operation of the partition wall 13. Therefore, in the present invention, when the nozzle plate 20 is made of Si, metal, or glass, a vibration energy buffering effect during the deformation operation of the partition wall 13 to be described later can be remarkably obtained.

  Examples of the metal nozzle plate include Ni, Ni / Co alloy, Cu, and stainless steel. When these metal nozzle plates are used, processing of a liquid chamber, an air groove, and the like described later can be performed in addition to the nozzle 21 by electroforming. In the case of a glass nozzle plate, the nozzle 21, liquid chamber, air groove and the like can be processed by sandblasting. In the case of a nozzle plate made of synthetic resin such as polyimide, a laser processing method can be mainly used.

  In this embodiment, an example in which a nozzle plate 20 made of Si is used is shown. Since the nozzle plate 20 made of Si can be manufactured using a semiconductor manufacturing process, highly accurate processing is possible, and the highly accurate nozzle plate 20 can be easily manufactured.

  In the nozzle plate 20, air groove portions 23 are respectively recessed at a predetermined depth from the joint surface 20 a at positions facing the front end surface 13 a of the partition wall 13 on the joint surface 20 a with the head chip 10.

  The air grooves 23 are located between the adjacent channels 12 so as to correspond to the front end surfaces 13 a of the partition walls 13 joined to the nozzle plate 20 via the adhesive 30. Each air groove part 23 is independent from each other air groove part 23. Each air groove portion 23 is formed in a narrow groove shape extending along the height direction of the partition wall 13 (the direction along the nozzle surface and perpendicular to the arrangement direction of the channels 12 and the vertical direction in FIG. 2). The nozzle surface does not penetrate. Each air groove portion 23 is blocked by the front end surface 10a of the head chip 10 including the front end surface 13a of the partition wall 13 with the adhesive 30 interposed therebetween, thereby forming an air chamber in which air is enclosed.

  In this way, an air groove portion that forms an air chamber in which air is enclosed by bonding with the head chip 10 at a portion where the front end surface 13a of each partition wall 13 is bonded via the adhesive 30 on the bonding surface 20a of the nozzle plate 20. 23 is provided, when vibration energy at the time of the deformation operation of the partition wall 13 is concentrated on the fixing portion between the front end surface 13a of the partition wall 13 and the nozzle plate 20, the vibration is caused by the air enclosed in the air groove portion 23. Energy is absorbed and buffered. As a result, the vibration energy concentrated on the fixing portion between the front end surface 13a of the partition wall 13 and the nozzle plate 20 is prevented from being reflected toward the center of the partition wall 13, and the partition wall 13 is deformed for the next discharge. It is possible to reduce the influence on the operation.

  Further, since it is possible to suppress the vibration energy due to the deformation operation of the partition wall 13 from affecting the deformation operation for the next discharge of the partition wall 13, the behavior of the ink meniscus in the nozzle 21 is stabilized, and the time until the next discharge is performed. Can be shortened. As a result, high-frequency driving can be performed stably.

  The condition of the width of the air groove 23 is that it is formed to be narrower than the width of the partition wall 13 (thickness along the arrangement direction of the channels 12). Since there is a possibility that the effect is not sufficiently exhibited, the thickness is preferably 5 μm or more.

  The length L of the air groove 23 is preferably longer than the height dimension H of the channel 12 on the front end face 10a of the head chip 10 (dimension in the direction along the nozzle surface and perpendicular to the arrangement direction of the channels 12). . By making it longer than the height dimension H of the channel 12, vibration energy over the entire height direction of the partition wall 13 can be effectively absorbed and buffered.

  Further, the depth of the air groove portion 23 is required to be shallower than the thickness of the nozzle plate 20, but if it is formed too deep, the strength of the nozzle plate 20 is reduced. Although the specific depth varies depending on the nozzle plate material, in the case of the nozzle plate 20 made of Si, the depth is preferably 90% or less of the thickness.

  As shown in FIG. 3, when a liquid chamber 22 that communicates with the nozzle 21 and has a larger diameter than the nozzle 21 is formed on the joint surface 20 a of the nozzle plate 20 with the head chip 10, From the viewpoint of maintaining durability, it is preferable that the depth of the air groove portion 23 is equal to or shallower than the depth of the liquid chamber 22 within a range that satisfies the above conditions.

  In the present embodiment, the liquid chamber 22 is formed in a rectangular shape slightly smaller than the opening shape of the channel 12, but the specific shape of the liquid chamber 22 is not particularly limited. In addition, the liquid chamber 22 is not essential in the present invention, but it is preferable to provide the liquid chamber 22 when the thickness of the nozzle plate 20 is increased from the viewpoint of securing the depth of the air groove 23.

  Usually, the width of the front end surface 13a of the partition wall 13 is extremely narrow, and it is difficult to arrange a plurality of air groove portions 23 side by side. Therefore, if there is one air groove portion 23 facing the front end surface 13a of one partition wall 13, Good. Further, as shown in FIG. 4, the air groove portion 23 corresponding to one partition wall 13 can be constituted by a plurality of air groove portions 23 a divided along the height direction of the partition wall 13. However, from the viewpoint of efficiently buffering vibration energy, it is preferable to form one air groove portion 23 as shown in FIG.

  The head chip 10 and the nozzle plate 20 are joined by being bonded via an adhesive 30 therebetween. At this time, as shown in a partially enlarged view in FIG. 3, it is preferable that the adhesive 30 is bonded in a state where a part of the adhesive 30 enters the air groove 23. Thereby, the excess adhesive 30 can be accommodated in the air groove part 23, the inflow of the excess adhesive to the channel 12 or the nozzle 21 can be prevented, and the adhesiveness is also improved.

  In order to allow the adhesive 30 to enter the air groove 23, the head chip 10 and the nozzle plate 20 are heated and then bonded. When the head chip 10 and the nozzle plate 20 return to room temperature, the air in the air groove 23 contracts, so that a part of the adhesive 30 can enter the air groove 23. By housing the surplus adhesive 30 in the air groove 23, the adhesion area is increased and an improvement in adhesion can be expected.

  As shown in FIG. 3, the adhesive 30 is slightly inserted from the opening side of the air groove 23, and the entire inside of the air groove 23 is not filled with the adhesive 30, but the adhesive is contained in the air groove 23. As a part of 30 enters, the amount of air in the air groove 23 is slightly reduced. However, since the epoxy adhesive generally used as the adhesive 30 has a lower elastic modulus than the nozzle plate material (Si, metal, glass) preferably used in the present invention, it has a buffering effect on the vibration energy of the partition wall 13. There is no significant damage.

  Next, an example of a manufacturing method of the nozzle plate 20 having such an air groove 23 will be described with reference to FIGS.

  An Si substrate 40 (thickness: 725 μm) that is sufficiently thicker than the nozzle plate 20 that is the final product is prepared, and a resist mask 50 is formed on the entire surface of one side (FIG. 5A). The resist mask 50 at the part to be formed is removed to form openings 51 respectively (FIG. 5B).

  Thereafter, etching is performed from the surface of the resist mask 50 to form the recesses 41 having a predetermined depth in the openings 51 (FIG. 5C). Here, the recesses 41 each having a depth of 30 μm were formed. Next, a support substrate 60 made of a glass substrate having a thickness of 200 μm for reinforcing the Si substrate 40 is attached to the surface where the recess 41 is formed from above the resist mask 50 (FIG. 5D).

  After polishing the Si substrate 40 to a thickness of 200 μm from the opposite side of the Si substrate 40 to which the support substrate 60 is attached (FIG. 6A), the Si substrate 40 was polished. A resist mask 70 is formed on the surface (FIG. 6B).

  Next, after removing the resist mask 70 at the position where the liquid chamber 22 and the air groove 23 are to be formed to form the liquid chamber opening 71 and the air groove opening 72, respectively (FIG. 6C), the resist By etching from the surface of the mask 70, the Si substrate 40 facing the liquid chamber opening 71 and the air groove opening 72 is respectively recessed (FIG. 6D).

  By recessing the Si substrate 40 from the liquid chamber opening 71, the nozzle 21 and the liquid chamber 22 including the recess 41 are formed in communication with the recess 41. On the other hand, by recessing the Si substrate 40 from the air groove opening 72, the air groove 23 is formed between the liquid chambers 22. At this time, the etching from the liquid chamber opening 71 and the air groove opening 72 is simultaneously performed, but the air groove opening 72 is narrower than the liquid chamber opening 71 and has an opening area. Therefore, the etching rate from the air groove opening 72 is lower, and as a result, the depth of the air groove 23 is shallower than the depth of the liquid chamber 22. Thereby, the air groove 23 shallower than the liquid chamber 22 can be easily formed.

  Thereafter, the Si substrate 40 is diced into the size of the nozzle plate 20 to cut out a plurality of nozzle plates 20, and the support substrate 60 and the resist masks 50 and 70 are removed, so that the nozzle plate 20 having the air grooves 23 is formed. It is produced (FIG. 6 (e)).

  In the ink jet head 1 described above, all the channels 12 are ink channels that discharge ink, and the nozzle 21 and the liquid chamber 22 are provided corresponding to each channel 12, but as shown in FIG. In addition, a so-called independent drive type in which ink channels 121 that eject ink and dummy channels 122 that do not eject ink are alternately arranged may be used. Also in this aspect, since each partition wall 13 is deformed for discharging ink from the ink channel 121, the air groove portion 23 is formed on the joint surface of the nozzle plate 20 at a position corresponding to the front end surface 13a of each partition wall 13. The

  In this aspect, the nozzle 21 and the liquid chamber 22 are not formed at a portion corresponding to the dummy channel 122 of the nozzle plate 20.

  Moreover, although the inkjet head 1 demonstrated above is a case where a channel row | line is 1 row | line | column, as shown in FIG. 8, you may have a several channel row | line | column used as 2 or more rows. In this case, as in FIG. 7, an independent drive type in which the ink channels 121 and the dummy channels 122 are alternately arranged may be used.

  Further, the air groove portions 23 described above are formed independently of the other air groove portions 23, but each air groove portion 23 is formed at a position facing the front end face 13 a of each partition wall 13 of the head chip 10. As long as shown in FIG. 9, the air groove portions 23 may be connected to each other. 9A shows a mode in which the air groove portions 23 are connected when the channel row is one row, and FIG. 9B shows a mode in which the air groove portions 23 are connected when the channel row is two rows. ing. Since the air grooves 23 are connected to each other, the amount of air enclosed inside by joining with the head chip 10 also increases, so that the buffering effect of vibration energy by air can be further improved.

  The effects of the present invention are illustrated below by examples.

Example 1
PZT that has been polarized is used as a partition wall material, and an inkjet head having a single channel column having a partition wall having an upper wall portion and a lower wall portion so that the polarization direction is opposite to the height direction of the partition wall did. The head chip structure and nozzle plate structure are as follows.

Head chip structure Number of channels: 256 channels Channel height H: 200 μm
Channel width: 82 μm
Partition width: 62 μm

Nozzle plate structure material: Si
Thickness: 200 μm
Liquid chamber depth: 170 μm
Nozzle diameter: 30 μm

In the nozzle plate, one air groove portion extending along the height direction of the partition wall is provided in a recessed manner at a position corresponding to the front end surface of each partition wall of the head chip, as in FIGS.
Air groove depth: 160 μm
Air groove width: 20 μm
Air groove length L: 300 μm

  The above nozzle plate was bonded to the front end surface of the head chip using an epoxy adhesive to produce an ink jet head. With respect to the obtained ink jet head, ink was continuously ejected at a driving voltage of 16.6 V and a driving frequency of 24.7 kHz and 12.3 kHz, and attention was paid to one nozzle at that time, and the droplet velocity from the nozzle was determined. Based on the following criteria, the evaluation was made. The droplet velocity was measured by imaging the ejected ink droplet and subjecting the ink droplet image to image processing. The results are shown in Table 1.

◎: 10 m / s or more ○: 9 m / s or more and less than 10 m / s △: 8 m / s or more and less than 9 m / s ▲: 6 m / s or more and less than 8 m / s

(Example 2)
Ink was ejected in exactly the same manner as in Example 1 except that the length L of each air groove 2 was 180 μm and shorter than the channel height H, and the droplet velocity was evaluated. The results are shown in Table 1.

(Comparative Example 1)
Ink was ejected in the same manner as in Example 1 except that no air groove was formed on the nozzle plate, and the droplet velocity was evaluated. The results are shown in Table 1.

(Comparative Example 2)
As shown in FIG. 10, the air groove portion of the nozzle plate was formed in a portion parallel to the nozzle row direction and corresponding to the outside of the channel. The depth and width of the air groove were the same as in Example 1, and the length along the nozzle row direction was 50 μm. Ink was ejected from this inkjet head under exactly the same driving conditions as in Example 1, and the droplet velocity was evaluated. The results are shown in Table 1.

  As described above, by forming the air groove portion at a position facing the front end face of the partition wall as in the present invention, the droplet velocity is improved and stable ejection can be achieved even during high frequency driving. In particular, by forming an air groove longer than the channel height as in Example 1, a higher effect than in Example 2 could be obtained.

1: Inkjet head 10: Head chip 10a: Front end surface of head chip 11: Channel substrate 12: Channel 121: Ink channel 122: Dummy channel 13: Partition wall 13a: Front end surface 131: Upper wall portion 132: Lower wall portion 14: Cover Substrate 15: Common flow path 16: Plate 17: Ink supply port 18: Ink supply pipe 20: Nozzle plate 20a: Bonding surface 21: Nozzle 22: Liquid chamber 23: Air groove 30: Adhesive 40: Si substrate 41: Recess 50 : Resist mask 51: opening 60: support substrate 70: resist mask 71: liquid chamber opening 72: air groove opening

Claims (6)

A head chip in which a plurality of channels and a plurality of partition walls containing a piezoelectric material at least in part are alternately arranged, and a pressure for discharging is applied to the ink in the channels by a deformation operation of the partition walls based on a driving voltage; An inkjet head having a nozzle plate joined to the front end face of the head chip via an adhesive, wherein the front end face of the partition wall and the nozzle plate are opposed to each other via an adhesive;
The ink jet head, wherein the nozzle plate has an air groove portion recessed from the joint surface at a position facing a front end surface of the partition wall of the joint surface with the head chip.   The inkjet head according to claim 1, wherein the air groove portion is provided along a height direction of the partition wall.   The inkjet head according to claim 2, wherein the air groove portion is longer than a height dimension of the channel on a front end surface of the head chip. The nozzle plate is provided with a liquid chamber having a larger diameter than the nozzle in communication with the nozzle on the joint surface with the head chip.
4. An ink jet head according to claim 1, wherein a depth of the air groove is equal to or shallower than a depth of the liquid chamber.   The inkjet head according to any one of claims 1 to 4, wherein the nozzle plate and the head chip are bonded in a state where the adhesive partially enters the air groove portion. The inkjet head according to claim 1, wherein the nozzle plate is made of Si, metal, or glass.

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