JP6685736B2 - Inkjet head - Google Patents

Description

  The embodiment of the present invention relates to an inkjet head that changes the volume of a pressure chamber filled with ink and ejects ink droplets from an ink meniscus of a nozzle provided in the pressure chamber.

  2. Description of the Related Art Inkjet printers that eject ink drops onto a medium such as paper to form images and characters have been known. This type of inkjet printer has, for example, an inkjet head including a plurality of pressure chambers filled with ink and a plurality of actuators. The actuator causes ink droplets to be ejected from the nozzles of the pressure chamber by changing the volume of the pressure chamber and causing pressure oscillation in the ink in the pressure chamber.

  In this type of inkjet head, the ink in each pressure chamber decreases due to the ejection of ink droplets, so it is necessary to replenish each pressure chamber with ink. In addition, the ejection of the ink droplets may cause the ink meniscus of the nozzle to be greatly depressed and bubbles to enter the pressure chamber. These bubbles cause ink droplet ejection to become unstable and cause variations in dot size. Therefore, it is necessary to circulate the ink in each pressure chamber to remove bubbles.

  However, the supply port for supplying ink to each pressure chamber and the discharge port for discharging ink eject the ink in the pressure chamber when the actuator is driven to cause pressure vibration in the ink in the pressure chamber. As a result, the pressure of the ink in the pressure chamber is reduced. There is known an inkjet head in which the supply port and the discharge port of each pressure chamber are sufficiently small in order to suppress such a pressure loss and generate a sufficient ejection pressure that contributes to the ejection of ink droplets.

JP, 2014-172323, A

  However, if the supply port and the discharge port of each pressure chamber are made small, it is necessary to make the ink have a relatively high pressure in order to supply and circulate the ink, which causes problems such as an increase in the size of the pump and an increase in power consumption.

  Therefore, there is a demand for the development of an inkjet head that is small in size, consumes less power, and can stably eject ink droplets.

The inkjet head according to the embodiment has a plurality of pressure chambers filled with ink, ejection holes for ejecting ink from the pressure chambers, and fluid communication with the pressure chambers in opposition to the pressure chambers . a plurality of individual supply channels individually supplying ink, and a plurality of individual discharge passage for individually discharging ink from each of the pressure chambers in fluid communication with opposite each pressure chamber, the pressure chamber in accordance with an electric signal And an actuator that causes the ink inside the pressure chamber to generate pressure vibration and ejects ink droplets from the ink meniscus formed in the ejection hole. Sectional area of the cross-sectional area and the individual discharge paths of the individual supply channel is approximately the same length and the length of the individual discharge paths of the individual supply passage Ri substantially equal der, the length of the discharge hole and L1 [m], The opening area of the discharge hole is S1 [m ² ], the lengths of the individual supply path and the individual discharge path are L2 [m], and the sum of the opening areas of the individual supply path and the individual discharge path is S2 [m ² ]. In that case, L2 / S2> = L1 / S1 / 3 holds .
The ink jet head according to the embodiment has a pressure chamber filled with ink, and a discharge hole for changing the volume of the pressure chamber according to an electric signal to generate pressure vibration in the ink and discharging the ink in the pressure chamber. An actuator substrate having a plurality of actuators, a plurality of individual supply passages and a plurality of individual discharge passages that face each of the pressure chambers and are in fluid communication with each other are formed, and the flow is joined to the joint surface of the actuator substrate opposite to the actuator. And a road substrate. On the joint surface, the distance between the outer edge of the individual supply passage and the farthest portion from the individual discharge passage and the distance between the individual supply passage and the outermost portion of the individual discharge passage is greater than the inner diameter of the pressure chamber.
The ink jet head according to the embodiment has a pressure chamber filled with ink, and a discharge hole for changing the volume of the pressure chamber according to an electric signal to generate pressure vibration in the ink and discharging the ink in the pressure chamber. An actuator substrate having a plurality of actuators, a plurality of individual supply passages and a plurality of individual discharge passages that face each of the pressure chambers and are in fluid communication with each other are formed, and the flow is joined to the joint surface of the actuator substrate opposite to the actuator. And a road substrate. The length of the discharge hole is L1 [m], the opening area of the discharge hole is S1 [m ² ], the lengths of the individual supply path and the individual discharge path are L2 [m], and the individual supply path and the individual discharge path are respectively defined. When the sum of the opening areas of the above is S2 [m ² ], L2 / S2> = L1 / S1 / 3 is established.

FIG. 1 is a perspective view showing an inkjet head according to an embodiment. FIG. 2 is a plan view showing an actuator substrate of the inkjet head of FIG. FIG. 3 is a partially enlarged plan view in which a part of the actuator substrate of FIG. 2 is enlarged. FIG. 4 is a partially enlarged cross-sectional view taken along the line IV-IV of FIG. FIG. 5 is a partially enlarged sectional view taken along line VV of FIG. FIG. 6 is a bottom view of the flow path substrate of the inkjet head of FIG. 1 viewed from the ink supply member side. FIG. 7 is a partially enlarged bottom view in which the bottom surface of the flow path substrate of FIG. 6 is partially enlarged. FIG. 8 is a plan view of the ink supply member of the inkjet head of FIG. 1 viewed from the flow path substrate side.

Hereinafter, embodiments will be described with reference to the drawings.
FIG. 1 is an external perspective view showing the inkjet head 1. The inkjet head 1 has a structure in which an actuator substrate 2, a flow path substrate 3, and an ink supply member 4 are laminated. The inkjet head 1 also includes a driver IC 5.

  The actuator substrate 2, the flow path substrate 3, and the ink supply member 4 are bonded to each other by, for example, an epoxy adhesive. The actuator substrate 2 and the driver IC 5 are electrically connected by an anisotropic conductive film (ACF).

  A large number of actuators 6 are formed in an array on the actuator substrate 2. Each actuator 6 has a nozzle 7 (ejection hole) for ejecting an ink droplet.

  The ink supply member 4 includes an ink supply pipe 8 for supplying ink to the inkjet head 1 and an ink discharge pipe 9 for collecting ink that has not been ejected from the nozzle 7. The ink supply pipe 8 and the ink discharge pipe 9 are connected to tubes (not shown) for feeding liquid.

  The driver IC 5 generates a drive signal for each actuator 6 according to a control signal from the inkjet printer. Each actuator 6 causes an ink droplet to be ejected through the nozzle 7 according to this drive signal.

  The ink supplied to the ink supply member 4 via the ink supply pipe 8 is supplied to the actuator substrate 2 via the flow path substrate 3. Ink droplets are ejected from the nozzle 7 according to the drive signal generated by the driver IC 5. The ink that has not been ejected from the nozzle 7 is collected by the ink supply member 4 via the flow path substrate 3 and is discharged through the ink discharge pipe 9.

  FIG. 2 is a partially enlarged plan view of the actuator substrate 2 viewed from the ink ejection direction. The actuator substrate 2 is provided with a plurality of actuators 6 and a plurality of extraction electrodes 31. The plurality of extraction electrodes 31 are formed of a conductive material, and the mounting pad 10 is provided at one end (lower end in the drawing) of each extraction electrode 31. The plurality of extraction electrodes 31 are formed by connecting a plurality of individual electrodes 11 individually extracted from each actuator 6 and a plurality of (eight in this embodiment) actuators 6 arranged in a straight line. The common electrode 12 is included.

  The individual electrode 11 electrically connects the lower electrode 14 of each actuator 6 described later to the mounting pad 10. The individual electrodes 11 are electrically independent from each other. Further, the common electrode 12 connects upper electrodes 16 of the plurality of actuators 6 described later in series and electrically connects to the mounting pad 10.

  The plurality of mounting pads 10 provided on the plurality of extraction electrodes 31 are electrically connected to the driver IC 5. An anisotropic conductive film (ACF) can be used for the connection between the mounting pad 10 and the driver IC 5. Alternatively, the mounting pad 10 may be connected to the driver IC 5 by a method such as wire bonding.

FIG. 3 is a partially enlarged plan view showing the actuator 6 in a further enlarged manner. FIG. 4 is a sectional view of the actuator substrate 2 taken along the line IV-IV in FIG.
The actuator 6 includes a vibration plate 13, a lower electrode 14, a piezoelectric body 15, an upper electrode 16, an insulating layer 17, a common electrode 12, a protective layer 18, and a liquid repellent layer 19. A nozzle 7 is provided at the center of the actuator 6. The nozzle 7 is a circular ejection hole that penetrates the diaphragm 13. The lower electrode 14, the piezoelectric body 15, and the upper electrode 16 have a substantially annular shape surrounding the nozzle 7.

  The diaphragm 13 is supported by the actuator substrate 2. In the present embodiment, the pressure chamber 20 is formed in the actuator substrate 2 by etching the constituent material of the actuator substrate 2 from the back surface side with the vibration plate 13 laminated on the actuator substrate 2. That is, on the back surface side of the actuator 6, a cylindrical internal space that functions as the pressure chamber 20 is provided. The nozzle 7 provided on the vibrating plate 13 communicates with the internal space of the pressure chamber 20.

  The inner diameter of the nozzle 7 and the inner diameter of the pressure chamber 20 are determined in consideration of desired ink ejection volume, driving frequency, and driving voltage. In this embodiment, the inner diameter of the nozzle 7 is 20 μm and the inner diameter of the pressure chamber 20 is 200 μm. The nozzle 7 and the pressure chamber 20 are arranged concentrically along the central axis C.

  The actuator substrate 2 is formed of single crystal silicon having a thickness of 50 μm. The thickness of the actuator substrate 2 is preferably 1/2 or less of the diameter of the pressure chamber 20. As a result, when the ink that has flown in from the individual ink supply path 21 described below flows out to the individual ink discharge path 22 described below, the entire ink in the pressure chamber 20 flows, and it is easy to discharge the air bubbles in the pressure chamber 20.

  On the other hand, if the thickness of the actuator substrate 2 is made larger than 1/2 of the diameter of the pressure chamber 20, the ink flow becomes poor near the back surface of the vibration plate 13, and it becomes difficult to remove the air bubbles entering from the nozzle 7.

The diaphragm 13 is integrally laminated with the actuator substrate 2 so as to cover the upper surface of the pressure chamber 20. The vibrating plate 13 is made of SiO ₂ and can be formed by heating a silicon wafer that will be the actuator substrate 2 at a high temperature. In this embodiment, the diaphragm 13 has a thickness of 4 μm.

  A lower electrode 14, a piezoelectric body 15, and an upper electrode 16 are formed on the front surface side of the vibration plate 13 in a donut shape centered around the nozzle 7. The inner diameters of the piezoelectric body 15 and the upper electrode 16 were 30 μm, and the outer diameters of the piezoelectric body 15 and the upper electrode 16 were 140 μm. The lower electrode 14 and the upper electrode 16 are made of a conductive material. In this embodiment, Pt is deposited by sputtering to form the lower electrode 14 and the upper electrode 16.

  The piezoelectric body 15 is made of a piezoelectric material. In this example, the piezoelectric body 15 was formed by depositing PZT (lead zirconate titanate) by a sputtering method. The PZT may be formed into a film by a sol-gel method or the like. The material of the piezoelectric body 15 is not limited to PZT, but KNN (potassium sodium niobate) or the like may be used. The thickness of the upper electrode 16 and the lower electrode 14 is 0.1 to 0.2 μm. The thickness of the piezoelectric body 15 was 2 μm.

  When a voltage is applied between the lower electrode 14 and the upper electrode 16, an electric field acts on the piezoelectric body 15 and the piezoelectric body 15 expands in the film thickness direction due to the inverse piezoelectric effect. As a result, the piezoelectric body 15 is orthogonal to the film thickness direction. Shrink in the direction you do. Due to the contraction of the piezoelectric body 15, the upper surface of the vibrating plate 13 contracts, and in the movable region of the actuator 6, that is, in the region where the vibrating plate 13 faces the pressure chamber 20, the actuator 6 is deformed in a direction projecting toward the pressure chamber 20. To do. As a result, the vibrating plate 13 is deformed to cause a pressure fluctuation in the ink in the pressure chamber 20, and an ink droplet is ejected through the nozzle 7.

An insulating layer 17 made of an insulating inorganic material is provided on the surface of the upper electrode 16. The insulating layer 17 can be formed by depositing SiO ₂ by the TEOS-CVD method. In this embodiment, the thickness of the insulating layer 17 is 0.5 μm. The insulating layer 17 is provided between the lower electrode 14 and the common electrode 12 in order to secure insulation between the lower electrode 14 and the common electrode 12 on the outer peripheral portion of the piezoelectric body 15.

  The insulating layer 17 in the movable region of the actuator 6 impedes the operation of the actuator 6. Therefore, it is desirable to minimize the portion of the insulating layer 17 that overlaps the movable region of the actuator 6. Therefore, in this embodiment, the insulating layer 17 is not formed in most of the movable region of the actuator 6.

  The presence of the insulating layer 17 affects the shape when the actuator 6 is deformed. That is, the deformation of the actuator 6 is small in the portion where the insulating layers 17 overlap, and the deformation is large in the other portions. Therefore, when the insulating layer 17 is formed in a shape asymmetric with respect to the center of the nozzle 7 so as to overlap the movable region of the actuator 6, the deformation of the actuator 6 becomes asymmetric with respect to the center of the nozzle 7, and The flight direction of the ejected ink droplet may be inclined. Therefore, the insulating layer 17 needs to be arranged in the movable region of the actuator 6 so as to overlap in a symmetrical shape with respect to the center of the nozzle 7.

  In the present embodiment, as shown in FIG. 3, the insulating layer 17 is arranged between two actuators 6 adjacent to each other along the common electrode 12, and the insulating layer 17 is arranged at a position symmetrical with respect to the center of each actuator 6. Overlaid on each actuator 6. In order to ensure such layout symmetry, for example, a dummy insulating layer 17a that does not flow a current is provided so as to overlap the actuators 6a arranged at the ends of the rows of the actuators 6.

  Further, in the present embodiment, the insulating layer 17 between the two adjacent actuators 6 is continuously formed without a break. As a result, it is possible to reduce the step generated in the common electrode 12 formed on the insulating layer 17, reduce the problem of disconnection of the common electrode 12 at the step portion of the cut of the insulating layer 17, and to improve the ink jet yield with high yield. A head can be provided.

  A common electrode 12 made of a conductive material is formed on the diaphragm 13, the upper electrode 16, and the insulating layer 17. The mounting pad 10 is provided at one end of the common electrode 12. The common electrode 12 electrically connects the upper electrodes 16 of the plurality of actuators 6 in the same column to the mounting pad 10. The common electrode 12 is electrically insulated from the lower electrode 14 of each actuator 6 via the insulating layer 17.

  On the other hand, the individual electrode 11 having conductivity is formed on the diaphragm 13 and the lower electrode 14. The mounting pad 10 is provided at one end of the individual electrode 11. The individual electrode 11 electrically connects the lower electrode 14 of each actuator 6 to the mounting pad 10. The individual electrodes 11 are electrically insulated from each other.

  In this embodiment, the individual electrode 11 and the common electrode 12 are formed by depositing gold by a sputtering method. The thickness of each of the individual electrode 11 and the common electrode 12 is 0.1 μm to 0.5 μm.

A protective layer 18 made of an insulating inorganic material is provided on the vibrating plate 13, the lower electrode 14, the piezoelectric body 15, the upper electrode 16, the insulating layer 17, the individual electrode 11, and the common electrode 12. The protective layer 18 is provided on the entire surface of the actuator substrate 2 except the region where the mounting pad 10 is formed. The protective layer 18 was formed by depositing SiO ₂ by the TEOS-CVD method. The thickness of the protective layer 18 is preferably 0.1 μm to 1 μm, and in this embodiment, the thickness of the protective layer 18 is 0.5 μm.

Since SiO ₂ is a relatively hard film made of an inorganic material, by covering the lower electrode 14, the piezoelectric body 15, and the upper electrode 16 with the protective layer 18, the stress associated with the driving of the actuator 6 causes these members 14, 15, 16 to move. It is possible to prevent the crystal structure from shifting and cracking. On the other hand, if the protective layer 18 is made too thick, the deforming operation of the actuator 6 is hindered, causing a problem in the ink droplet ejecting operation.

  In addition, the protective layer 18 protects the electrodes 14 and 16 inside the actuator 6 and the piezoelectric body 15 from ink and moisture in the air. However, if the thickness of the protective layer 18 is set to a thickness that does not hinder the operation of the actuator 6, the action of protecting the inside of the actuator 6 from moisture cannot always be sufficiently performed. Therefore, in the present embodiment, the protective layer 18 is thinned, and the resin relatively soft liquid repellent layer 19 is provided on the protective layer 18 so that the protective layer 18 does not absorb water.

As the material of the protective layer 18, in addition to SiO ₂ , an inorganic material such as SiN can be used. Since SiN has lower hygroscopicity than SiO _2, it has a high protective effect against moisture. However, since SiO ₂ has a smaller Young's modulus than SiN, it is less likely that the deformation operation of the actuator 6 will be hindered. Therefore, the material of the protective layer 18 is appropriately selected according to requirements.

  A liquid-repellent layer 19 made of a resin having liquid-repellent property is provided on the entire surface of the protective layer 18. The liquid repellent layer 19 was formed by depositing an amorphous fluororesin by a spin coating method. As the amorphous fluororesin, for example, CYTOP (registered trademark) manufactured by Asahi Glass was used. The contact angle of the liquid repellent layer 19 with water is 90 degrees or more. The thickness of the liquid repellent layer 19 is 0.5 μm to 5 μm. In this embodiment, the thickness of the liquid repellent layer 19 is 1 μm.

  The liquid-repellent layer 19 can prevent ink from adhering to the actuator 6, and can prevent the protective layer 18 from absorbing moisture. In addition, since the liquid repellent layer 19 is made of resin, the Young's modulus is relatively small, and it is difficult to inhibit the deformation operation of the actuator 6. In addition, the liquid repellent layer 19 can prevent ink from adhering to the actuator 6 and prevent a problem that the ink adhering to the surface of the actuator 6 blocks the nozzle 7 and hinders ink ejection.

  FIG. 5 is a cross-sectional view of the actuator substrate 2, the flow path substrate 3, and the ink supply member 4 along the line VV of FIG. FIG. 6 is a bottom view of the flow path substrate 3 viewed from the ink supply member 4 side. FIG. 7 is a partially enlarged bottom view in which the bottom surface of the flow path substrate 3 is partially enlarged. FIG. 8 is a plan view of the ink supply member 4 viewed from the flow path substrate 3 side.

  The flow path substrate 3 has a plurality of sets of individual ink supply paths 21 (supply paths) and a plurality of individual ink discharge paths 22 (discharge paths) respectively corresponding to the plurality of pressure chambers 20 of the actuator substrate 2. The plurality of sets of individual ink supply paths 21 and individual ink discharge paths 22 each have a substantially semicircular cross-sectional shape, and are provided so as to penetrate the flow path substrate 3. Therefore, the plurality of sets of the individual ink supply passages 21 and the individual ink discharge passages 22 are arranged in an array in the same pattern as the plurality of pressure chambers 20.

  Focusing on the pair of individual ink supply passages 21 and individual ink discharge passages 22 facing each pressure chamber 20, the pair of passages 21 and 22 have a height along the thickness direction of the passage substrate 3 over their entire length. It is partitioned by the partition wall 29 that has. The partition wall 29 is not provided individually facing the plurality of pressure chambers 20, but is continuously arranged in a meandering shape, passing between the channels 21 and 22 of each set. Both ends of the partition wall 29 in the height direction are arranged on both sides of the flow path substrate 3.

  Further, a shared ink supply path 23 communicating with the plurality of individual ink supply paths 21 and a shared ink discharge path 24 communicating with the plurality of individual ink discharge paths 22 are provided on the bottom surface of the flow path substrate 3 on the ink supply member 4 side. It is provided. The shared ink supply path 23 and the shared ink discharge path 24 have a depth that is less than half the thickness of the flow path substrate 3. The shared ink supply passage 23 and the shared ink discharge passage 24 each have a comb-shaped intricate shape, and face each other with a meander-shaped partition wall 29 interposed therebetween.

  The shared ink supply path 23 includes a basic ink supply path 25 extending in the longitudinal direction of the flow path substrate 3. The shared ink discharge path 24 includes a basic ink discharge path 26 extending in the longitudinal direction of the flow path substrate 3.

  Focusing on one pressure chamber 20, the cross-sectional areas of the individual ink supply passage 21 and the individual ink discharge passage 22 are approximately the same as the cross-sectional area of the pressure chamber 20 in total. Further, by making the cross-sectional area of the individual ink supply passage 21 and the cross-sectional area of the individual ink discharge passage 22 the same, the circulation of ink is performed most efficiently. If the cross-sectional area of the individual ink supply passage 21 and the cross-sectional area of the individual ink discharge passage 22 are significantly different, the efficiency of ink circulation is limited to the smaller cross-sectional area. Further, by making the length of the individual ink supply passage 21 and the length of the individual ink discharge passage 22 the same, the circulation of ink is performed most efficiently. If the length of the individual ink supply passage 21 and the length of the individual ink discharge passage 22 are significantly different, the efficiency of ink circulation is limited to the longer one. That is, in the present embodiment, the cross-sectional areas of the individual ink supply passage 21 and the individual ink discharge passage 22 that communicate with each pressure chamber 20 are designed to be sufficiently large so that the ink can easily flow through each pressure chamber 20. Therefore, it is not necessary to upsize a pump (not shown) and power consumption can be suppressed.

  The individual ink supply passage 21 and the individual ink discharge passage 22 have a length of 200 μm to 1000 μm. As a result, inertial resistance can be applied to the ink filling the individual ink supply path 21, and inertial resistance can be applied to the ink filling the individual ink discharge path 22. Therefore, according to the present embodiment, when the actuator 6 causes pressure vibration in the ink inside the pressure chamber 20, this pressure vibration escapes from the pressure chamber 20 via the individual ink supply passage 21 and the individual ink discharge passage 22. This can be suppressed and ink can be easily ejected from the nozzle 7. In this embodiment, the length of each individual ink supply path 21 and each individual ink discharge path 22 is 400 μm.

  In order to give the ink in the individual ink supply path 21 and the individual ink discharge path 22 an inertial resistance, the flow path connecting the individual ink supply path 21, the pressure chamber 20, and the individual ink discharge path 22 must be filled with ink. There is. In this case, the ink may include a small amount of bubbles generated in the pressure chamber 20 due to the ejection of the ink droplets. That is, “the length of the individual ink supply passage 21 (supply passage)” and “the length of the individual ink discharge passage 22 (discharge passage)” in the claims and the detailed description of the invention are “filled with ink”. "Length" means the length.

The length required for the individual ink supply passage 21 or the individual ink discharge passage 22 for giving inertial resistance is obtained by applying the theory disclosed in Japanese Patent No. 5659198 to this embodiment. That is, the length of the nozzle 7 that ejects ink droplets is L1, the opening area of the nozzle 7 is S1, the lengths of the individual ink supply passage 21 and the individual ink discharge passage 22 are L2, and the individual ink supply passage 21 is If the sum of the opening areas of the individual ink discharge paths 22 is S2,
(Formula 1) L2 / S2> = L1 / S1 / 3
The length L2 of the individual ink supply path 21 and the individual ink discharge path 22 and the sum S2 of the opening areas may be set so as to satisfy the above condition.

For example, L1 is set to 5.5 × 10 ⁻⁶ [m], S1 is set to 3.14 × 10 ⁻¹⁰ [m ² ], L2 is set to 4 × 10 ⁻⁴ [m], and S2 is set to 3.14 × 10. ^{When -8} [m ² ] is set, L1 / S1 / 3 is 5.84 × 10 ³ [1 / m], L2 / S2 is 1.27 × 10 ⁴ [1 / m], and the formula 1 is obtained. Meet In this case, the ink in the individual ink supply path 21 and the ink in the individual ink discharge path 22 can have a sufficient inertia resistance, and the ink in the pressure chamber 20 is discharged by the individual ink supply path 21 or the individual ink when ejecting an ink droplet. It is possible to prevent the ink from flowing into the ink discharge path 22 and stabilize the ejection of ink droplets.

  The partition 29 separates the individual ink supply path 21 and the individual ink discharge path 22, and the sum of the opening area of the individual ink supply path 21 and the opening area of the individual ink discharge path 22 is defined as the cross-sectional area of the pressure chamber 20. In order to make them substantially the same, the opening diameter D (FIG. 7) of the substantially circular hole in which the individual ink supply passage 21 and the individual ink discharge passage 22 are combined is larger than the inner diameter of the pressure chamber 20. The partition wall 29 is formed so as to pass through the center of a substantially circular shape where the individual ink supply passage 21 and the individual ink discharge passage 22 are combined. In this embodiment, the inner diameter of the pressure chamber 20 is 200 μm, while the substantially circular opening diameter D of the individual ink supply passage 21 and the individual ink discharge passage 22 is 220 μm. That is, in this case, the width of the partition 29 is 20 μm.

  As a result, a positional deviation of up to 10 μm can be allowed along the joint surface between the actuator substrate 2 and the flow path substrate 3, the change in the opening area of the pressure chamber 20 can be suppressed, and the ink due to the change in the opening area can be suppressed. It is possible to suppress variations in ejection characteristics and prevent deterioration of print quality.

  Further, as in the present embodiment, the plurality of individual ink supply paths 21 are connected by the shared ink supply path 23, the plurality of individual ink discharge paths 22 are connected by the shared ink discharge path 24, and the basic ink supply of the shared ink supply path 23 is performed. The passage 25 and the ink supply groove 27 of the ink supply member 4 are opposed to each other, and the basic ink discharge passage 26 of the shared ink discharge passage 24 and the ink discharge groove 28 of the ink supply member 4 are opposed to each other. Even when the joint surface between the ink supply member 4 and the ink supply member 4 is displaced, the flow rate of the ink flowing through each individual ink supply passage 21 and each individual ink discharge passage 22 can be made constant. As a result, variations in the flow rate of ink flowing through the individual ink supply passage 21 and the individual ink discharge passage 22 can be suppressed, variations in ink ejection characteristics can be suppressed, and deterioration of print quality can be prevented.

  As shown in FIG. 8, an ink supply groove 27 and an ink discharge groove 28 are provided on the surface of the ink supply member 4 on the flow path substrate 3 side. The ink supply groove 27 and the ink discharge groove 28 extend along the longitudinal direction of the ink supply member 4. The ink supply groove 27 and the ink discharge groove 28 are fluidly connected to the basic ink supply path 25 and the basic ink discharge path 26 of the flow path substrate 3 in a state where the flow path substrate 3 and the ink supply member 4 are joined. . The ink supply pipe 8 is fluidly connected to one end of the ink supply groove 27, and the ink discharge pipe 9 is fluidly connected to one end of the ink discharge groove 28.

  In this embodiment, the basic ink supply path 25 and the basic ink discharge path 26 are provided in the flow path substrate 3, and the ink supply groove 27 and the ink discharge groove 28 are provided in the ink supply member 4. The supply passage 25 and the main ink discharge passage 26, or the ink supply groove 27 and the ink discharge groove 28 of the ink supply member 4 may be omitted. For example, the ink supply groove 27 and the ink discharge groove 28 of the ink supply member 4 may be eliminated, the ink supply pipe 8 may be connected to the basic ink supply path 25, and the ink discharge pipe 9 may be connected to the basic ink discharge path 26. .

Next, the operation of the inkjet head 1 of this embodiment will be described.
When the ink is injected from the ink supply pipe 8, the pressure chamber 20 is filled with the ink via the ink supply groove 27, the basic ink supply passage 25, the shared ink supply passage 23, and the individual ink supply passage 21. Further, ink is discharged from the ink discharge pipe 9 through the individual ink discharge path 22, the shared ink discharge path 24, the basic ink discharge path 26, and the ink discharge groove 28.

  By setting the pressure of the ink flowing through the ink supply pipe 8 to be higher than the pressure of the ink flowing through the ink discharge pipe 9 and adjusting the average value of both pressures lower than atmospheric pressure by about 1000 Pa, the ink meniscus inside the nozzle 7 is reduced. Is formed. In this state, the ink is not leaked from the nozzle 7 or the outside air is sucked through the nozzle 7 (while the shape of the ink meniscus is stabilized), and the ink supply pipe 8 reaches the ink discharge pipe 9 as described above. Ink can be stably circulated through the flow path.

  When the driver IC 5 generates a drive signal in this state, the voltage between the individual electrode 11 and the common electrode 12 changes. Thereby, the voltage between the lower electrode 14 and the upper electrode 16 changes, and the actuator 6 is displaced. When the actuator 6 is displaced, pressure vibration is generated in the ink inside the pressure chamber 20, and an ink droplet is ejected from the nozzle 7. At that time, since the ink in the individual ink supply path 21 and the individual ink discharge path 22 has an inertial resistance, it is possible to suppress the ink from flowing out of the pressure chamber 20 due to the pressure vibration, and to eject the ink droplets from the nozzle 7. Can be discharged efficiently.

  Bubbles may enter the pressure chamber 20 from the nozzle 7 during the ink ejection operation. When bubbles enter the pressure chamber 20, even if the actuator 6 is displaced, sufficient pressure vibration cannot be applied to the ink, and the ink cannot be ejected from the nozzle 7. However, since the ink inside the inkjet head 1 is constantly flowing, the bubbles that have entered the pressure chamber 20 are discharged to the shared ink discharge path 24 via the individual ink discharge path 22.

  The bubbles discharged to the shared ink discharge path 24 are discharged to the outside of the inkjet head 1 through the basic ink discharge path 26, the ink discharge groove 28, and the ink discharge pipe 9. That is, the bubbles that have entered one pressure chamber 20 are discharged to the outside of the inkjet head 1 without entering the other pressure chamber 20. As described above, the inkjet head 1 of the present embodiment can automatically and effectively discharge the bubbles that have entered the pressure chamber 20, and thus the inkjet head 1 having high reliability can be provided.

Then, the effect of this embodiment is explained.
According to the inkjet head 1 of the present embodiment, the flow path substrate 3 provided between the actuator substrate 2 and the ink supply member 4 has the individual ink supply path 21 and the individual ink discharge path 22 connected to each pressure chamber 20. The individual ink supply path 21 and the individual ink discharge path 22 filled with ink have inertial resistance.

  That is, according to the present embodiment, the cross-sectional area of the individual ink supply passage 21 and the individual ink discharge passage 22 is approximately the same as the cross-sectional area of the pressure chamber 20 in total. The individual ink supply passage 21 and the individual ink discharge passage 22 have a length of 300 μm to 1000 μm. As a result, a sufficiently large inertial resistance is imparted to the ink filling the insides of the individual ink supply passage 21 and the individual ink discharge passage 22.

  Therefore, when the actuator 6 causes pressure vibration in the ink inside the pressure chamber 20, the ink inside the pressure chamber 20 is prevented from flowing to the individual ink supply passage 21 and the individual ink discharge passage 22 based on this pressure vibration. Therefore, the ink droplets can be easily ejected from the nozzle 7. Further, since the cross-sectional areas of the individual ink supply passage 21 and the individual ink discharge passage 22 may be approximately the same as the cross-sectional area of the pressure chamber 20 in total, it is necessary to greatly reduce the opening area of the passage through which the ink flows. The pressure difference between the ink supply pipe 8 and the ink discharge pipe 9 for causing the ink to constantly flow in the pressure chamber 20 can be reduced, the pump for generating the pressure difference can be downsized, and the power consumption can be reduced. It can be reduced.

  According to the inkjet head 1 of the above-described embodiment, since the ink in the individual ink supply path 21 and the individual ink discharge path 22 connected to each pressure chamber 20 is given a sufficient inertia resistance, the ink droplets are ejected. At this time, the pressure drop in the pressure chamber 20 can be suppressed, and the ink droplets can be stably ejected. Further, according to the present embodiment, the cross-sectional areas of the individual ink supply passage 21 and the individual ink discharge passage 22 connected to each pressure chamber 20 can be made sufficiently large, the flow path resistance can be made small, and the size and power consumption can be reduced. A small number of inkjet heads can be provided.

The embodiments described above are presented as examples, and are not intended to limit the scope of the invention. The embodiment described above can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. The above-described embodiments and modifications thereof are included in the invention described in the claims and equivalents thereof, as well as included in the scope and the gist of the invention.
Hereinafter, the inventions described in the claims at the initial application of the present application will be additionally described.
[1]
A pressure chamber filled with ink,
A discharge hole for discharging ink from this pressure chamber,
A supply path that fluidly communicates with each of the pressure chambers and supplies ink to the pressure chambers,
A discharge path that fluidly communicates with each of the pressure chambers and discharges ink from the pressure chambers,
An actuator that changes the volume of the pressure chamber according to an electric signal to generate pressure oscillation in the ink in the pressure chamber and ejects an ink droplet from an ink meniscus formed in the ejection hole,
The cross-sectional area of the supply passage and the cross-sectional area of the discharge passage are substantially the same, and the length of the supply passage and the length of the discharge passage are substantially the same.
Inkjet head.
[2]
A pressure chamber filled with ink; and an actuator having a discharge hole that discharges ink in the pressure chamber while changing the volume of the pressure chamber according to an electric signal to generate pressure vibration in the ink. An actuator substrate,
A supply channel and a discharge channel that are in fluid communication with each of the pressure chambers are formed, and a flow path substrate bonded to a bonding surface of the actuator substrate opposite to the actuator,
An ink supply port that is fluidly connected to the supply path and is supplied with the ink;
An ink discharge port that is fluidly connected to the discharge path and discharges the ink;
An inkjet head having a.
[3]
The cross-sectional area of the supply passage and the cross-sectional area of the discharge passage are substantially the same, and the length of the supply passage and the length of the discharge passage are substantially the same.
The inkjet head of [2].
[4]
In the joint surface, a distance between outer edges of the supply passage and the discharge passage is larger than a distance between outer edges of the pressure chamber,
The inkjet head according to [2] or [3].
[5]
The length of the discharge hole is L1 [m], the opening area of the discharge hole is S1 [m2], the lengths of the supply path and the discharge path are L2 [m], and the supply path and the discharge are the same. When the sum of the opening areas of the road is S2 [m2],
L2 / S2> = L1 / S1 / 3
Holds,
The inkjet head according to any one of [1] to [4].

  1 ... Inkjet head, 2 ... Actuator substrate, 3 ... Flow path substrate, 4 ... Ink supply member, 5 ... Driver IC, 6 ... Actuator, 7 ... Nozzle, 8 ... Ink supply pipe, 9 ... Ink discharge pipe, 10 ... Mounting Pads, 11 ... Individual electrodes, 12 ... Common electrodes, 13 ... Vibrating plate, 14 ... Lower electrodes, 15 ... Piezoelectric body, 16 ... Upper electrodes, 17 ... Insulating layer, 18 ... Protective layer, 19 ... Liquid repellent layer, 20 ... Pressure chamber, 21 ... Individual ink supply path, 22 ... Individual ink discharge path, 23 ... Shared ink supply path, 24 ... Shared ink discharge path, 25 ... Core ink supply path, 26 ... Core ink discharge path, 27 ... Ink supply groove , 28 ... Ink discharge groove, 29 ... Partition wall, 31 ... Extraction electrode.

Claims (5)

A plurality of pressure chambers filled with ink,
A discharge hole for discharging ink from this pressure chamber,
The individual supply channel of a plurality individual supply ink to each of the pressure chambers in fluid communication with opposite each of said pressure chambers,
A plurality of individual discharge passage for individually discharging ink from each of the pressure chambers in fluid communication with opposite each of said pressure chambers,
An actuator that changes the volume of the pressure chamber according to an electric signal to generate pressure oscillation in the ink in the pressure chamber and ejects an ink droplet from an ink meniscus formed in the ejection hole,
The cross-sectional area of the cross-sectional area of the individual supply channels the individual discharge channel is substantially the same, Ri substantially equal der length of the individual lengths of the supply passage and the individual discharge channel,
The length of the discharge hole is L1 [m], the opening area of the discharge hole is S1 [m ² ], the lengths of the individual supply path and the individual discharge path are L2 [m], and the individual supply When the sum of the opening areas of the passage and the individual discharge passage is S2 [m ² ],
L2 / S2> = L1 / S1 / 3
Holds,
Inkjet head. A plurality of pressure chambers filled with ink, and a plurality of actuators that change the volume of the pressure chambers according to an electric signal to generate pressure vibration in the ink and have an ejection hole for ejecting ink in the pressure chamber. An actuator substrate having
Individual supply channels and the individual discharge passage in fluid communication with and opposed to each of the pressure chamber is formed with a plurality of the actuator substrate, anda channel substrate that is joined to the joint surface opposite to the actuator ,
In the joint surface, the distance between the outer edge of the individual supply path and the farthest portion of the individual supply path and the outer edge of the individual supply path and the farthest portion of the individual discharge path is larger than the inner diameter of the pressure chamber,
Lee ink jet head.   A plurality of pressure chambers filled with ink, and a plurality of actuators that change the volume of the pressure chambers according to an electric signal to generate pressure vibration in the ink and have an ejection hole for ejecting ink in the pressure chamber. An actuator substrate having
  A plurality of individual supply passages and individual discharge passages that are in fluid communication with each of the pressure chambers are formed, and a flow path substrate bonded to a bonding surface of the actuator substrate opposite to the actuator. ,
  The length of the discharge hole is L1 [m], and the opening area of the discharge hole is S1 [m]. ^Two ], The lengths of the individual supply path and the individual discharge path are L2 [m], and the sum of the opening areas of the individual supply path and the individual discharge path is S2 [m]. ^Two ],
      L2 / S2> = L1 / S1 / 3
  Holds,
  Inkjet head. The cross-sectional area of the individual supply passage and the cross-sectional area of the individual discharge passage are substantially the same, and the length of the individual supply passage and the length of the individual discharge passage are substantially the same.
The inkjet head according to claim 2 or 3 .   The thickness of the actuator substrate is ½ or less of the diameter of the pressure chamber,
  The inkjet head according to claim 2.