JP3595129B2 - Inkjet head - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an inkjet head, and more particularly, to an inkjet head that ejects ink droplets using displacement of an electromechanical transducer in a direction d33.
[0002]
[Prior art]
Generally, as an ink jet head used in an ink jet recording apparatus used as an image forming apparatus such as a printer, a facsimile, a copying apparatus, etc., a plurality of nozzles for discharging ink droplets, an ink liquid chamber to which each nozzle communicates, and an ink in each ink liquid chamber And an electromechanical conversion element such as a piezoelectric element that generates energy for ejecting ink droplets from the nozzles by pressing the ink droplets. Is ejected to record an image.
[0003]
In such an ink jet head, for example, in the case of a head using a multilayer piezoelectric element as an electromechanical transducer and utilizing the displacement of the multilayer piezoelectric element in the d33 direction (see JP-A-3-73347), As the degree of integration increases, it is required that the electrical connection between the end face electrode of the piezoelectric element and the driving IC for driving the piezoelectric element be made reliably.
[0004]
Therefore, as described in, for example, JP-A-8-318625, electrodes are formed on a substrate on which a plurality of piezoelectric elements are joined, and end electrodes of the piezoelectric elements (electrodes formed on a surface parallel to the laminating direction). ) And an electrode on the substrate are connected by a conductive adhesive such as silver paste, and a flexible printed cable (FPC) is connected to the electrode on the substrate to electrically connect the piezoelectric element to the driving IC. I have to.
[0005]
[Problems to be solved by the invention]
However, when the end face electrode of the piezoelectric element and the electrode on the substrate are connected by a conductive adhesive, it is necessary to form an electrode surface on the substrate, apply the conductive adhesive, and the like. When the method of slitting the piezoelectric element and dividing the piezoelectric element into a plurality of piezoelectric elements and electrodes is adopted, the conductive adhesive may peel off.
[0006]
SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to provide an ink jet head which is inexpensive to manufacture and has high electrical reliability.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the inkjet head according to claim 1 is configured such that the electromechanical transducer is joined to a holding portion wider than the electromechanical transducer, and a member having a convex cross-sectional shape is formed. An end face electrode serving as an individual electrode and / or an end face electrode serving as a common electrode of the electromechanical transducer is formed thereon, and a flexible printed cable is directly connected to the end face electrode on the holding portion .
[0008]
In the ink jet head according to the second aspect, a holding portion made of an electromechanical transducer element material wider than the electromechanical transducer element is formed integrally with the electromechanical transducer element to form a member having a convex cross section. An end face electrode serving as an individual electrode of the electromechanical transducer and / or an end face electrode serving as a common electrode are also formed on the portion, and a flexible printed cable is directly connected to the end face electrode on the holding portion .
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is an exploded perspective view showing an example of an ink jet head according to the present invention, FIG. 2 is an enlarged cross-sectional view of a main part in a direction orthogonal to a channel direction (nozzle arrangement direction) of the head, and FIG. It is a principal part expanded sectional view.
[0010]
This ink jet head includes a drive unit 1, a liquid chamber unit 2, and a head cover 3.
The drive unit 1 has two rows of energy generating means 12 for generating energy for discharging ink droplets on a ceramic substrate, for example, an insulating substrate 11 such as barium titanate, alumina, or forsterite. The frame members 13 made of resin, ceramic, etc., surrounding the energy generating means 12 in each row are joined by an adhesive 14.
[0011]
The plurality of energy generating means 12 includes a driving unit to which a driving pulse for making the ink droplets fly is provided, and a liquid chamber unit which is located between the two driving units and is not supplied with the driving pulse. The non-driving portion serving as a liquid chamber support member for fixing the second member 2 to the substrate 11 is formed alternately.
[0012]
Here, as shown in FIG. 4, the energy generating means 12 holds the laminated piezoelectric element 17 which is a laminated electromechanical transducer by bonding it to a holding portion 18 having a wider width, and has a sectional shape as a whole. It has a convex shape. As the piezoelectric element 17, a laminated piezoelectric element having ten or more layers is used. For example, as shown in FIG. 2, this laminated piezoelectric element is made of lead zirconate titanate (PZT) 20 having a thickness of 10 to 50 μm / 1 layer and silver / paradium (AgPd) having a thickness of several μm / 1 layer. The internal electrodes 21 are alternately laminated, but the material used for the piezoelectric element is not limited to the above, and other materials and other electromechanical conversion elements can be used.
[0013]
End electrodes 22 and 23 made of AgPd or the like are formed on both end faces parallel to the laminating direction of the piezoelectric elements 17 (the opposing face sides of the two piezoelectric element rows are end face electrodes 22, and the non-opposing face sides are end face electrodes 23). Are formed, and the internal electrodes 21 of the piezoelectric element 17 are connected to the left and right end face electrodes 22 and 23 every other layer. By applying a drive voltage between these end face electrodes 22 and 23, an electric field is generated in the stacking direction, and a displacement in the stacking direction (displacement in the direction d33) is generated.
[0014]
On the other hand, the liquid chamber unit 2 includes a diaphragm 31 formed of a metal or resin thin film, a liquid chamber partition member 32 having a two-layer structure formed of a photosensitive resin layer formed of a dry film resist (DFR), a metal, a resin, or the like. And a nozzle plate 33 made of the above. With each of these members, one piezoelectric element 12 (driving unit 17), a diaphragm part 34 corresponding to this one piezoelectric element 12, a pressurized liquid chamber 35 pressurized through each diaphragm part 34, Common liquid chambers 36, 36 located on both sides of the pressurized liquid chamber 35 for introducing ink to be supplied to the pressurized liquid chamber 35, and ink supply for communicating the pressurized liquid chamber 35 with the common liquid chambers 36, 36. One channel is formed by the passages 37, 37 and the nozzle 38 communicating with the pressurized liquid chamber 35, and a plurality of channels are provided in two rows.
[0015]
The diaphragm 31 forms the diaphragm portion 34 corresponding to the driving portion 17, the beam 41 joined to the non-driving portion 18, and the base 42 joined to the frame member 13. The diaphragm portion 34 includes an island-shaped convex portion 43 joined to the driving portion 17 and a thinnest portion (diaphragm region) 44 having a thickness of about 3 to 10 μm formed around the convex portion 43.
[0016]
The liquid chamber partition member 32 includes a first photosensitive resin layer 45 having a predetermined liquid chamber pattern formed by previously laminating a dry film resist on the diaphragm 31 side, exposing using a required mask, and developing the same. A dry film resist is preliminarily laminated on the plate 33 side, exposed using a required mask, developed, and bonded to the second photosensitive resin layer 46 formed with a predetermined liquid chamber pattern by thermocompression bonding.
[0017]
The nozzle plate 33 has a large number of nozzles 38, which are fine ejection ports for ejecting ink droplets. The inner shape (inner shape) of the nozzle 38 is formed in a horn shape (may be a substantially columnar shape or a substantially truncated cone shape). The diameter of the nozzle 38 is about 25 to 35 μm in diameter on the ink droplet outlet side.
[0018]
The ink ejection surface (nozzle surface side) of the nozzle plate 33 is a water-repellent surface 47 that has been subjected to a water-repellent surface treatment as shown in FIG. For example, PTFE-Ni eutectoid plating, electrodeposition coating of fluororesin, vapor-deposited coating of evaporable fluororesin (for example, pitch fluoride), baking after solvent application of silicon-based resin or fluorine-based resin, etc. By providing a water-repellent film selected according to the physical properties of the ink, the ink droplet shape and flying characteristics are stabilized, and high-quality image quality can be obtained. The periphery of the nozzle plate 33 is a non-water-repellent surface 48 on which no water-repellent film is formed.
[0019]
After processing and assembling the liquid chamber unit 2 separately from the drive unit 1, the vibration plate 31 of the liquid chamber unit 2 is joined to the piezoelectric element 12 and the frame member 13 of the drive unit 1 with an adhesive 50. And an inkjet head.
[0020]
The substrate 11 is supported and held on a spacer member (head holder) 51 serving as a head support member, and a PCB substrate 52 having a head driving IC and the like disposed in the spacer member 51 and each of the drive unit 1 are provided. The end electrodes 22 and 23 of the piezoelectric element 12 are connected via FPC cables 53 and 53.
[0021]
The nozzle cover (head cover) 3 is formed in a box shape to cover the periphery of the nozzle plate 33 and the side surface of the head, and has an opening corresponding to the water-repellent surface 47 of the nozzle plate 33. The non-water-repellent surface 48 left on the peripheral edge of the plate 33 is adhesively bonded with an adhesive. Further, this ink jet head is provided with ink supply holes 54 to 57 in the spacer member 51, the substrate 11, the frame member 13 and the vibration plate 31, respectively, for supplying ink from an ink cartridge (not shown) to the liquid chamber.
[0022]
In the ink jet head configured as described above, by applying a driving waveform (pulse voltage of 10 to 50 V) to the driving unit 17 in accordance with the recording signal, a displacement in the stacking direction occurs in the driving unit 17, and the diaphragm 31 is displaced. The pressurized liquid chamber 35 is pressurized through the diaphragm section 34 of the above, and the pressure is increased, and ink droplets are ejected from the nozzle 38. At this time, an ink flow also occurs in the direction of the ink supply paths 37, 37 communicating from the pressurized liquid chamber 35 to the common liquid chamber 36. However, by reducing the cross-sectional area of the ink supply paths 37, 37, the fluid resistance portion is reduced. And reduces the flow of ink toward the common liquid chambers 36, 36, thereby preventing a drop in ink ejection efficiency.
[0023]
Then, with the end of the ink droplet ejection, the ink pressure in the pressurized liquid chamber 35 is reduced, and a negative pressure is generated in the pressurized liquid chamber 34 due to the inertia of the ink flow and the discharge process of the drive pulse, thereby causing ink filling. Move to the process. At this time, the ink supplied from the ink tank flows into the common liquid chambers 36, 36, and is filled from the common liquid chambers 36, 36 into the pressurized liquid chamber 35 via the ink supply paths 37, 37. Then, when the vibration of the ink meniscus surface near the outlet of the nozzle 38 is attenuated and returned to the vicinity of the outlet of the nozzle 38 (refill) due to surface tension and reaches a stable state, the next ink droplet ejection operation is started.
[0024]
Therefore, the details of the drive unit 1 in the ink jet head will be described with reference to FIGS.
First, as shown in FIG. 5, energy generating means 12, 12 (hereinafter referred to as “energy generating means 61, 61”) before division are arranged side by side in a predetermined direction on a substrate 11 and joined by an adhesive 14. I do. Here, the energy generating means 61 has a convex sectional shape by bonding and bonding the laminated piezoelectric element 17 before splitting to the wide holding portion 18. The holding portion 18 can be formed of a piezoelectric material or a different material different from the piezoelectric material.
[0025]
In this way, by forming the energy generating means 61 (the energy generating means 12 after division) so as to have a convex cross-sectional shape, as shown in FIG. Since the crimping direction of the FPC 53 is on a plane, the workability of the crimping work is extremely good. Note that it is not impossible to press-bond the FPC 53 to the side surface only with the energy generating means 61 as the piezoelectric element 17 as shown in FIG. Further, the energy generating means 12 having a convex shape is not formed by bonding the laminated piezoelectric element 17 and the holding section 18 by bonding, but the holding section 18 is also made of a piezoelectric material when the laminated piezoelectric element 17 is fired. It can also be formed.
[0026]
In addition, the end face electrodes 22 and 23 are formed on the energy generating means 61 by a method such as vapor deposition and plating before bonding to the substrate 11. As a material of the end face electrodes 22 and 23, gold, silver, platinum or the like is preferable. At this time, the end face electrodes 22 and 23 are formed not only on the end face of the piezoelectric element 17 but also on the flat portion of the holding portion 18.
[0027]
Then, as shown in FIG. 8, the energy generating means 61 is slit at a predetermined pitch using a dicing saw or the like to divide the energy generating means 61 into a plurality of energy generating means 12. At this time, the slit grooves 11a can be reliably divided into a plurality of energy generating means 12 by inserting the slit grooves 11a even on the substrate 11.
[0028]
Therefore, as shown in FIG. 9, the FPC 53 is connected to the end face electrode 23 on the individual electrode side of the piezoelectric element 17 formed on the holding portion 18 of the energy generating means 12 by thermocompression bonding. As shown in FIG. 10, the FPC 53 has an electrode surface 53a patterned into an individual electrode shape. As a thermocompression bonding material for thermocompression bonding of the FPC 53, solder or the like is preferable. In this case, as shown in FIG. 11, by fixing a part of the FPC 53 on the substrate 11 with an adhesive or the like, it is possible to prevent the FPC crimping portion from peeling off in handling from the next step.
[0029]
Also, as shown in FIG. 12, the FPC 53 is connected to the end electrode 22 on the common electrode side of the piezoelectric element 17 formed on the holding portion 18 of the energy generating means 12 by thermocompression bonding. The FPC 53 has an electrode surface 53b patterned into a common electrode shape as shown in FIG. 13 together with the above-described individual electrode shape electrode 53a.
[0030]
As described above, in this ink jet head, since the FPC is directly connected to the individual electrodes of the piezoelectric element and each end face electrode serving as a common electrode, there is no step of applying a conductive adhesive using a dispenser or the like, and the electrode connection method is simplified. As a result, the reliability of the electrical connection is improved, and the variation in the resistance value between the channels is reduced as compared with the case where a conductive adhesive is used.
[0031]
That is, as described above, when the electrode formed on the substrate and the end face electrode of the piezoelectric element are connected in advance with a conductive adhesive (silver paste or the like), and then the piezoelectric element is slit and divided into a plurality of piezoelectric elements. When the silver paste may cause peeling failure, resulting in disconnection failure, and when the specific resistance value of the silver paste material varies within a production lot, silver paste materials of different production lots may be transferred to the same head. In this case, the resistance value varies. On the other hand, in the present invention, since the conductive adhesive is not used, disconnection failure and variation in resistance value are reduced.
[0032]
It should be noted that the function and effect of the present invention can be obtained as long as the FPC is directly connected to only one of the individual electrodes of the piezoelectric element and one of the end face electrodes serving as the common electrode.
[0033]
【The invention's effect】
As described above, according to the inkjet head of the present invention, the holding portion made of the electromechanical transducer element wider than the electromechanical transducer element is formed integrally with the electromechanical transducer element so that the cross-sectional shape is convex. Or a member having a cross-sectional shape that is formed integrally with the electromechanical conversion element and a holding portion made of an electromechanical conversion element material wider than the electromechanical conversion element is formed, An end face electrode serving as an individual electrode of the electromechanical transducer and / or an end face electrode serving as a common electrode are also formed on the holding portion, and the flexible printed cable is directly connected to the end face electrode on the holding portion, so that the flexible portion is flexible. The printed cable can be crimped from a direction parallel to the end face of the electromechanical transducer, thereby reducing manufacturing costs and improving reliability.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing an example of an ink jet head according to the present invention. FIG. 2 is an enlarged cross-sectional view of a main part in a direction orthogonal to a channel direction (nozzle arrangement direction) of the head. FIG. FIG. 4 is a perspective view of the energy generating means of the head. FIG. 5 is a perspective view illustrating a state before the piezoelectric element is divided. FIG. 6 is a view showing a process of manufacturing the energy generating means of FIG. FIG. 7 is a front view illustrating an example of energy generating means. FIG. 8 is a perspective view illustrating a state after a piezoelectric element is divided. FIG. 9 is an end face electrode on an individual electrode side of a piezoelectric element, an FPC, and the like. FIG. 10 is a schematic plan view of a main part of an FPC. FIG. 11 is an explanatory view illustrating a state after connection between an electrode of a piezoelectric element and an FPC. FIG. 12 is a common electrode side end face of the piezoelectric element. Explain the connection between electrodes and FPC Akirazu 13 principal part schematic plan view of the FPC EXPLANATION OF REFERENCE NUMERALS
1 ... driving unit, 2 ... liquid chamber unit, 12 ... energy generating means, 17 ... piezoelectric element, 18 ... holding portion, 22 ... common electrode side edge electrode, 2 3 ... individual electrode end surface electrode, 53 ... FPC, 53a, 53b ... electrode.

Claims (2)

In an ink jet head for ejecting ink droplets using displacement of the electromechanical transducer in the direction d33, a member having a convex cross-sectional shape formed by joining the electromechanical transducer to a holding portion wider than the electromechanical transducer. Are also formed on the holding portion, and an end surface electrode serving as an individual electrode of the electromechanical transducer and / or an end surface electrode serving as a common electrode are formed on the holding portion, and a flexible printed cable is directly connected to the end surface electrode on the holding portion. An ink jet head characterized by being performed . In an ink jet head that ejects ink droplets using displacement of the electromechanical transducer in the d33 direction, a holding portion made of an electromechanical transducer element wider than the electromechanical transducer element is formed integrally with the electromechanical transducer element. A member having a convex cross-sectional shape is formed, and an end face electrode serving as an individual electrode and / or an end face electrode serving as a common electrode of the electromechanical transducer is formed also on the holding portion. An ink jet head, wherein a flexible printed cable is directly connected to an end electrode .

Images