JP6251108B2 - Inkjet printer head - Google Patents

Description

  Embodiments described herein relate generally to an inkjet printer head.

  As an ink jet printer head, for example, a share mode share wall type ink jet printer head having a structure called a side shooter type having a nozzle on a side surface of a pressure chamber is known. The inkjet head includes a substrate, a frame member bonded to the substrate, a nozzle plate bonded to the frame member, a piezoelectric member bonded to the substrate at a position inside the frame member, and a piezoelectric member for driving the piezoelectric member. And an IC for driving the head. And at the time of printing, the piezoelectric member is driven, and the support columns, which are driving elements provided on both sides of each pressure chamber in the piezoelectric member, are curved by performing shear mode deformation, thereby pressurizing the ink in the pressure chamber, Ink droplets are ejected from the nozzles.

JP 2002-321361 A

  In a conventional ink jet printer head, when a soft resin nozzle plate is fixed to a piezoelectric member, a phenomenon occurs in which the nozzle plate is also deformed when each pressure chamber in the piezoelectric member is deformed. Therefore, a part of the driving force of the piezoelectric member may be used for the deformation of the nozzle plate.

  There is also an ink jet printer head having a configuration in which, for example, a highly rigid metal lid member is interposed between a piezoelectric member and a nozzle plate. In this case, it is possible to prevent a part of the driving force of the piezoelectric member from being used for the deformation of the nozzle plate by firmly connecting the fixing portion between the pressure chamber and the lid member, and the ink ejection efficiency. It is conceivable to prevent the deterioration of However, in the conventional ink jet printer head, the vibration of the pressure fluctuation of the ink in the pressure chamber used at the time of one ink ejection is transmitted to the lid member, and the other pressure chamber side that is not used at the time of ink ejection may vibrate. There is. In this case, since there is a possibility that it will be used for the next ink discharge in a state where the other pressure chambers that are not used at the time of ink discharge are vibrated, crosstalk occurs at the next ink discharge, and the ink discharge amount and the discharge Control accuracy such as speed is reduced, and printing stability is reduced.

According to the embodiment, the inkjet head includes a substrate, a frame member, a nozzle plate, a pair of piezoelectric members, a plurality of pressure chambers, and a lid. The frame member is bonded to the substrate. The nozzle plate is bonded to the frame member to form a pair of nozzle rows including a plurality of nozzles. The pair of piezoelectric members is bonded to the substrate at a position inside the frame member. The plurality of pressure chambers are formed in a groove shape on the surface of each piezoelectric member, and correspond to each nozzle of each nozzle row. The lid portion is interposed between the pair of piezoelectric members and the nozzle plate, and has a plurality of communication holes communicating with the plurality of nozzles. The lid unit sets a Young's modulus in 100～200Gpa, the thickness of the first portion covering the pressure chamber and 30 to 60 m, the common liquid chamber and the piezoelectric between each of the pressure chambers of the pair of the piezoelectric member A thin portion having a thickness smaller than that of the first portion is provided in the second portion that covers the common liquid chamber outside the member . The nozzle plate is formed of a resin material having a thickness of 25 to 75 μm.

FIG. 3 is a perspective view showing a partially broken ink jet head according to the first embodiment. Sectional drawing cut | disconnected in the position of F2-F2 line shown in FIG. 2A and 2B illustrate the operation of the inkjet head according to the first embodiment, in which FIG. 1A is a longitudinal sectional view of a main part showing a configuration around a pressure chamber, and FIG. 1B is a main part showing a state in which the pressure chamber is decompressed. FIG. 4C is a longitudinal sectional view of the main part showing a state in which the pressure chamber is pressurized and ink is ejected. FIG. 6 is a characteristic diagram showing experimental results of evaluating discharge voltage and pressure propagation time when the pressure chamber density is 150 dpi when the ink jet head according to the first embodiment is made as a prototype using the combinations shown in Table 1. The characteristic view which shows the experimental result which evaluated the discharge voltage and pressure propagation time in case a pressure chamber density is 300 dpi when the ink jet head of 1st Embodiment is made as an experiment with the combination of Table 1. FIG.

[First Embodiment]
(Constitution)
1 to 5 show a first embodiment of the present invention. The ink jet head 11 of the present embodiment is a so-called share mode share wall type ink circulation type ink jet head and has a structure called a side shooter type. As shown in FIGS. 1 and 2, the inkjet head 11 includes a substrate 12, a frame member 13 bonded to the substrate 12, a nozzle plate 14 bonded to the frame member 13, and a position inside the frame member 13. A piezoelectric member 15 bonded to the substrate 12 and a head driving IC 16 for driving the piezoelectric member 15 are provided.

  The nozzle plate 14 is formed of a resin material having a thickness of 25 to 75 μm, for example, a rectangular polyimide film. The nozzle plate 14 has a pair of nozzle rows 21. Each nozzle row 21 includes a plurality of nozzles 22.

  The piezoelectric member 15 is formed, for example, by bonding two piezoelectric plates 23 made of PZT (lead zirconate titanate) so that their polarization directions are opposed to each other. The piezoelectric member 15 has a trapezoidal cross section and is formed in a rod shape. The piezoelectric member 15 includes a plurality of pressure chambers 24 that are cut and formed in a groove shape on the surface, a column portion 25 that is a drive element provided on both sides of each pressure chamber 24, a side surface of each column portion 25, and a pressure chamber 24. And an electrode 26 formed on the bottom of the substrate.

  The nozzle plate 14 is joined to the column portion 25 of the piezoelectric member 15 via a lid portion 27 made of a highly rigid material such as metal or ceramics. Here, the piezoelectric member 15 is bonded to the substrate 12 so as to correspond to the nozzle row 21 on the nozzle plate 14. The pressure chamber 24 and the column part 25 are formed corresponding to the nozzle 22.

  The lid portion 27 is formed with a communication hole 28 that communicates with each pressure chamber 24. In the present embodiment, the lid portion 27 has a Young's modulus set to 100 to 200 Gpa. Further, the lid portion 27 of the present embodiment has a first portion 27 a that covers the pressure chamber 24 and a second portion 27 b that covers the common liquid chamber 41 between the pressure chambers 24. The thickness of the 1st part 27a shall be 30-60 micrometers, and the 2nd part 27b is provided with the thin part 27b2 smaller in thickness than the 1st part 27a. In the present embodiment, the thin portion 27b2 of the second portion 27b is set to ½ of the thickness of the first portion 27a.

  The nozzles 22 of the nozzle plate 14 are opened so as to communicate with the respective communication holes 28. A plurality of electrical wirings 29 are provided on the substrate 12. Each electrical wiring 29 is connected to the electrode 26 at one end and to the head driving IC 16 at the other end.

  The substrate 12 is formed in a square plate shape using ceramics such as alumina. The substrate 12 has a supply port 31 and a discharge port 32 each formed by a hole. The supply port 31 is connected to an ink tank of a printer (not shown), and the discharge port 32 is connected to an ink tank (not shown). During operation of the inkjet head 11, ink is supplied through the supply port 31, and ink that has flowed out of the ink tank is filled into the pressure chamber 24 through the supply port 31. Ink that has not been used in the pressure chamber 24 is collected in the ink tank by the discharge port 32. The ink jet head 11 according to the present embodiment is a circulation type head having a feature that the ink in the pressure chamber 24 is circulated to automatically remove mixed bubbles and the like.

  3A to 3C are diagrams illustrating the operation of the inkjet head 11. Here, FIG. 3A is a longitudinal sectional view of the main part showing the configuration around the pressure chamber 24, and FIG. 3B shows a state where the pressure chamber 24 is depressurized (a state where the pressure chamber 24 is expanded). FIG. 5C is a longitudinal sectional view of the main part showing a state in which the pressure chamber 24 is pressurized and ink is ejected (the pressure chamber 24 is contracted). When the user instructs printing to the printer, the control unit of the printer outputs a print signal to the inkjet head 11 to the head driving IC 16. Upon receiving the print signal, the head driving IC 16 applies a driving pulse voltage to the column portion 25 via the electric wiring 29. As a result, the pair of left and right pillars 25 are first separated so as to be deformed (curved) into a “<” shape by performing shear mode deformation. At this time, the pressure chamber 24 is depressurized (the pressure chamber 24 is enlarged) as shown in FIG. Next, as shown in FIG. 3C, these are returned to the initial positions to increase the pressure in the pressure chamber 24 (the pressure chamber 24 is contracted). As a result, the ink in the pressure chamber 24 is supplied to the nozzle 22 of the nozzle plate 14 through the communication hole 28 of the lid portion 27, and ink droplets are ejected vigorously from the nozzle 22.

  In such an ink jet head 11, the lid 27 constitutes one wall surface of the pressure chamber 24, and thus affects the rigidity of the pressure chamber 24. Since the rigidity of the pressure chamber 24 increases as the rigidity of the lid portion 27 increases (the harder and thicker the cover 27 is, the pressure generated by the piezoelectric member 15 is efficiently used for ink ejection, and the pressure propagation speed in the ink is increased. Can be driven at high speed. Here, since it is necessary to provide the lid 27 with the opening of the communication hole 28 communicating with the nozzle 22, if the lid 27 is too thick, the fluid resistance to the nozzle 22 increases and the discharge efficiency decreases. On the contrary, if the opening of the communication hole 28 of the lid portion 27 is increased so that the discharge efficiency does not decrease, the rigidity of the pressure chamber 24 decreases and the pressure chamber 24 also increases, so the pressure propagation speed decreases. Therefore, it is conceivable that there are optimum values for the thickness of the lid portion 27 and the size of the hole of the communication hole 28.

  In the inkjet head 11 of the present embodiment, the discharge voltage of the ink discharged from the nozzle 22 and the length in the direction along the longitudinal direction of the pressure chamber 24 in the communication hole 28 of the lid portion 27 (see L6 in FIG. 2) The length ratio (minimum value X1 in FIG. 4 (A2) and the minimum value in FIG. 5 (B2) at which the relationship with the length ratio of the pressure chamber 24 in the longitudinal direction (see L3 in FIG. 2) is minimized. It is set to a range of 10 to 25% around the center of Y1).

(Prototype of inkjet head 11)
An ink-jet head 11 was made by trial using the combinations shown in Table 1 below.

  The heads 11 are roughly classified into two types, and two typical types of pressure chamber densities of 150 dpi and 300 dpi have been prototyped. In Table 1, sample no. 1 to 60, the pitch (L1) of the pressure chambers 24 is 169 μm, the width (L2) is 80 μm, the length (L3) is 2000 μm, and the depth (L4) is 300 μm. Sample No. 61-120, the pitch (L1) of the pressure chambers 24 is 84.5 μm, the width (L2) is 40 μm, the length (L3) is 1500 μm, and the depth (L4) is 150 μm. In the lid portion 27, Young's modulus (Gpa), thickness (L5), and opening length (L6) of the communication hole 28 are set as shown in Table 1, respectively. Here, PZT having a Young's modulus of about 50 GPa, Ni—Fe alloy (42 Alloy) of about 150 GPa, and 92 alumina of about 250 GPa are used as the material of the lid 27, and the width of the communication hole 28 of the lid 27 is The width (L2) of the pressure chamber 24 was made substantially equal.

(test)
Sample No. above. For each of the inkjet heads 1 to 120, the ejection voltage (the voltage necessary for ejecting a fixed amount of ink droplets at a predetermined driving speed), the pressure propagation time (the pressure propagation speed is the time during which the pressure propagates through the pressure chamber). (Inverse proportion) was evaluated. The test results are shown in Table 2 below.

  Moreover, the result totaled for every parameter of the cover part 27 is shown to the following FIG. FIG. 4 is a characteristic diagram showing experimental results of evaluating the discharge voltage V1 (V) and the pressure propagation time T1 (μsec) when the pressure chamber density is 150 dpi. Here, FIG. 4A1 shows T1, the length (L6) in the direction along the longitudinal direction of the pressure chamber 24 in the communication hole 28 of the lid portion 27, and the length (L3) in the longitudinal direction of the pressure chamber 24. It is a characteristic view which shows the relationship with length ratio X (%). FIG. 4A2 is a characteristic diagram showing the relationship between the ejection voltage V1 and X. In FIG. FIG. 4A3 is a characteristic diagram showing the relationship between T1 and the thickness L5 of the lid 27. FIG. 4A4 is a characteristic diagram showing the relationship between the ejection voltage V1 and L5. FIG. 4 (A5) is a characteristic diagram showing the relationship between T1 and the Young's modulus of the lid 27. FIG. FIG. 4A6 is a characteristic diagram showing the relationship between the ejection voltage V1 and the Young's modulus of the lid 27.

  FIG. 5 is a characteristic diagram showing experimental results of evaluating the discharge voltage V2 (V) and the pressure propagation time T2 (μsec) when the pressure chamber density is 300 dpi. Here, FIG. 5B1 shows T2, the length (L6) in the direction along the longitudinal direction of the pressure chamber 24 in the communication hole 28 of the lid portion 27, and the length (L3) in the longitudinal direction of the pressure chamber 24. It is a characteristic view which shows the relationship with the length ratio Y (%). FIG. 5B2 is a characteristic diagram showing the relationship between the ejection voltage V2 and Y. FIG. 5 (B3) is a characteristic diagram showing the relationship between T2 and the thickness L5 of the lid 27. FIG. 5 (B4) is a characteristic diagram showing the relationship between the ejection voltage V2 and L5. FIG. 5 (B5) is a characteristic diagram showing the relationship between T2 and the Young's modulus of the lid 27. FIG. 5 (B6) is a characteristic diagram showing the relationship between the ejection voltage V2 and the Young's modulus of the lid 27.

(Action / Effect)
4 and 5, the parameter that most affects the characteristics is the length (L6) in the direction along the longitudinal direction of the pressure chamber 24 in the communication hole 28 of the lid 27. Yes, it was found that both the two types of inkjet heads 11 are suitably used when the length ratio X and Y of the pressure chamber 24 are in the range of 10 to 25%.

  The thickness (L5) of the lid portion 27 is preferably as thin as possible, but since the influence is less than the length (L6) of the communication hole 28, it may be selected as appropriate from the viewpoint of handling, manufacturability, cost, etc. . As the Young's modulus of the lid part 27 is larger (harder), it is more suitable. However, if it is too hard in manufacturing, processing becomes difficult, so about 150 GPa is sufficient.

  Furthermore, since various inks are used in the inkjet head 11, the lid portion 27 is bonded with a thermosetting adhesive in consideration of ink resistance. Therefore, it is desirable that the thermal expansion coefficient of the lid portion 27 is closer to the piezoelectric member 15 because the warp of the head 11 is smaller. Even if it can be bonded with a normal temperature curing adhesive, it is conceivable that the temperature of the head 11 rises during use, and thus the ink having a low viscosity is discharged at a high temperature. Therefore, it is desirable that the coefficient of thermal expansion is close to that of the piezoelectric member 15, and therefore, 42 Alloy, Invar, Kovar, etc. are preferable.

In the case of these conductive lids 27, an insulating thin film such as SiO ₂ is formed on the bonding surface in order to contact the electrode 26 of the pressure chamber 24 via an adhesive.

  Therefore, the above configuration has the following effects. In other words, in the inkjet head 11 of the present embodiment, the opening length of the communication hole 28 in each parameter of the thickness of the lid 27 (L5), the Young's modulus, and the opening length (L6) of the communication hole 28. It has been found that the size of (L6) has the greatest influence on the characteristics of the inkjet head 11. In the inkjet head 11 of the present embodiment, the discharge voltage of the ink discharged from the nozzle 22 and the length in the direction along the longitudinal direction of the pressure chamber 24 in the communication hole 28 of the lid portion 27 (see L6 in FIG. 2) The length ratio (see X1 in FIG. 4 (A2) and Y1 in FIG. 5 (B2)) that minimizes the relationship between the length of the pressure chamber 24 in the longitudinal direction (see L3 in FIG. 2) and the length ratio. The center is set to a range of 10 to 25% before and after the center. Thereby, by optimizing the size of the opening length (L6) of the communication hole 28, it is possible to improve the ink ejection efficiency, reduce the drive voltage, and increase the drive frequency.

  Moreover, in this Embodiment, the cover part 27 has set the Young's modulus to 100-200 Gpa. Further, the lid portion 27 of the present embodiment has a first portion 27 a that covers the pressure chamber 24 and a second portion 27 b that covers the common liquid chamber 41 between the pressure chambers 24. The thickness of the 1st part 27a shall be 30-60 micrometers, and the 2nd part 27b is provided with the thin part 27b2 smaller in thickness than the 1st part 27a. Here, the lid portion 27 is provided with a groove-shaped cutout portion 27b1 at a portion corresponding to the second portion 27b on the surface side, for example, so that a thin portion 27b2 is formed. As a result, the lid portion 27 is less rigid in the second portion 27b than in the first portion 27a. In this case, residual vibration due to ink pressure fluctuation in the pressure chamber 24 used at the time of one ink discharge can be suppressed, and a damper effect can be obtained in the common liquid chamber 41 between the pressure chambers 24. Therefore, the vibration of the pressure fluctuation of the ink in the pressure chamber 24 used at the time of one ink discharge is transmitted to the lid 27, and the other pressure chamber 24 that is not used at the time of ink discharge is prevented from vibrating. Can do. Therefore, it can be prevented from being used for the next ink discharge in a state where the other pressure chamber 24 that is not used at the time of ink discharge is vibrated, so that the crosstalk can be suppressed at the next ink discharge and the printing can be stably performed. Can increase the sex.

  In the present embodiment, the lid portion 27 can be formed of a single plate, so that the lid portion 27 can be easily manufactured, and when the inkjet head 11 is assembled, it is easy to assemble with other components. Can be

  Furthermore, the ink flow path can be constructed by forming the nozzle plate 14 after joining the lid portion 27 of the pressure chamber 24.

  According to the embodiment, it is possible to provide an ink jet printer head that can eject ink efficiently and at high speed.

  Further, a structure in which up to half of the electrodes 26 are provided without stacking the piezoelectric members 15 may be used.

Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.
Hereinafter, the invention described in the scope of claims of the present application will be appended.
[1] A plurality of pressure chambers formed in a groove shape in piezoelectric members having opposite polarization directions, and a nozzle plate disposed on a side surface of the pressure chamber via a lid having high rigidity, are formed on the nozzle plate. In the ink jet printer head in which a plurality of communication holes communicating with the plurality of nozzles are formed in the lid portion, the lid portion has a Young's modulus set to 100 to 200 Gpa and a first portion that covers the pressure chamber. A thickness of 30 to 60 μm is provided, and a thin portion having a thickness smaller than that of the first portion is provided in a second portion that covers the common liquid chamber between the pressure chambers, and the nozzle plate is a resin material having a thickness of 25 to 75 μm. An ink jet printer head, characterized by being formed by
[2] The inkjet printer head according to [1], wherein the thin portion of the second portion is half the thickness of the first portion.
[3] The inkjet printer head according to [1] or [2], wherein the lid portion is a low thermal expansion metal.
[4] The inkjet printer head according to any one of [1] to [3], wherein the inkjet printer head is a side shooter type share mode share wall system.
[5] The inkjet printer head according to any one of [1] to [4], wherein the piezoelectric member is a laminate of two PZTs having opposite polarization directions.

    DESCRIPTION OF SYMBOLS 11 ... Inkjet head, 12 ... Board | substrate, 13 ... Frame member, 14 ... Nozzle plate, 15 ... Piezoelectric member, 16 ... IC for head drive, 21 ... Nozzle row, 22 ... Nozzle, 23 ... Piezoelectric plate, 24 ... Pressure chamber 25 ... pillar part, 26 ... electrode, 27 ... lid part, 27a ... first part, 27b ... second part, 27b2 ... thin part, 28 ... communication hole, 29 ... electric wiring, 41 ... common liquid chamber.

Claims (5)

A substrate,
A frame member bonded to the substrate;
A nozzle plate bonded to the frame member and formed with a pair of nozzle rows including a plurality of nozzles;
A pair of piezoelectric members that adhere to the substrate at a position inside the frame member;
A plurality of pressure chambers formed in a groove shape on the surface of each piezoelectric member, corresponding to each nozzle of each nozzle row;
A lid portion interposed between the pair of piezoelectric members and the nozzle plate and having a plurality of communication holes communicating with the plurality of nozzles;
The lid portion has a Young's modulus set to 100 to 200 Gpa, a thickness of a first portion covering the pressure chamber is set to 30 to 60 μm, and a common liquid chamber between the pressure chambers of the pair of piezoelectric members and the piezoelectric member And providing a thin portion with a thickness smaller than that of the first portion in the second portion covering the common liquid chamber outside
The nozzle plate is formed of a resin material having a thickness of 25 to 75 μm.   2. The ink jet printer head according to claim 1, wherein the thin portion of the second portion is half the thickness of the first portion. The inkjet printer head according to claim 1, wherein the lid portion is any one of 42 Alloy, Invar, and Kovar .   4. The ink jet printer head according to claim 1, wherein the ink jet printer head is a side shooter type share mode share wall system.   5. The ink jet printer head according to claim 1, wherein the piezoelectric member is a laminate of two PZTs having opposite polarization directions.