CN111216453A

CN111216453A - Ink jet head

Info

Publication number: CN111216453A
Application number: CN201910961761.6A
Authority: CN
Inventors: 入江一伸; 吉田英博; 大塚巨
Original assignee: Panasonic Intellectual Property Management Co Ltd
Current assignee: Panasonic Intellectual Property Management Co Ltd
Priority date: 2018-11-27
Filing date: 2019-10-10
Publication date: 2020-06-02
Anticipated expiration: 2039-10-10
Also published as: JP7203337B2; TWI819087B; CN111216453B; TW202023841A; JP2020082548A

Abstract

The present disclosure provides an ink jet head with high reliability. An inkjet head (100) is provided with: a piezoelectric element (5); a vibrating plate (8); and an adhesive material layer (9) that is disposed between the piezoelectric element (5) and the vibration plate (8) and bonds the piezoelectric element (5) and the vibration plate (8), wherein the adhesive material layer (9) contains beads (11) having a higher hardness than the vibration plate (8), and the thickness (91) of the adhesive material layer (9) is smaller than the particle diameter of the beads (11).

Description

Ink jet head

Technical Field

The present disclosure relates to an inkjet head.

Background

In the manufacturing process of electronic devices and optical devices, a process of forming a fine pattern on a substrate by printing is often used. In printing of fine patterns, a series of channels, piezoelectric elements, diaphragms, and the like, which are involved in the ejection of ink-formed materials, are required to be downsized and densified. Further, a technique for reducing the size and increasing the density of a piezoelectric element has been disclosed (for example, see patent document 1).

Patent document 1 discloses a liquid ejecting head including: in the lead-out wiring for driving the piezoelectric element, the width of the adhesion layer to which the conductive layer is adhered is narrowed, whereby even if the piezoelectric element is disposed at high density, short-circuiting between adjacent lead-out wirings can be suppressed.

Prior art documents

Patent document

Patent document 1: japanese patent laid-open publication No. 2018-027711

Patent document 2: japanese laid-open patent publication No. 10-34919

Disclosure of Invention

Problems to be solved by the invention

However, in the ejection of ink using an inkjet head, it is necessary to reliably join the vibration plate and the piezoelectric element. For example, when the reliability of such bonding is low, the vibration plate is peeled off from the piezoelectric element, and the ink ejection accuracy in design cannot be maintained.

Accordingly, an object of the present disclosure is to provide an inkjet head having high reliability.

Means for solving the problems

One embodiment of an inkjet head according to the present disclosure includes: a piezoelectric element; a vibrating plate; and an adhesive material layer disposed between the piezoelectric element and the vibration plate and joining the piezoelectric element and the vibration plate, wherein the adhesive material layer contains beads having a higher hardness than the vibration plate, and a film thickness of the adhesive material layer is smaller than a particle diameter of the beads.

Effects of the invention

According to one embodiment of the present disclosure, an inkjet head with high reliability can be provided.

Drawings

Fig. 1 is an enlarged cross-sectional view of a conventional ink jet head.

Fig. 2 is a sectional view of the ink jet head according to embodiment 1.

Fig. 3 is a sectional view of the ink jet head according to embodiment 2.

Fig. 4 is an enlarged cross-sectional view of the ink jet head according to embodiment 3.

Fig. 5 is an enlarged cross-sectional view of the ink jet head according to embodiment 4.

Description of the symbols

1: nozzle plate, 2: nozzle, 3: pressure generating chamber, 4: flow path forming substrate, 5a, 5 c: piezoelectric element, 6: drive unit, 7: pillar portion, 8a, 8 b: diaphragm, 9a, 9b, 9c, 9 d: adhesive material layer, 10: base, 11, 12, 13, 14: bead, 51: recessed portion, 81: vibrating portion, 82 a: joint, 83: deformation, 90 b: recess, 91, 92, 94, 95: film thickness, 93: projections, 100a, 100b, 100c, 100 d: an ink jet head.

Detailed Description

(insight underlying the disclosure)

As a method for forming a fine pattern at low cost, a printing method of liquefying a material ink of a desired pattern and printing on a substrate, particularly an ink jet method which does not require a printing plate, has attracted attention. However, in recent years, with the demand for finer patterns formed by an ink jet method, the pitch between nozzles of a nozzle row has become smaller, and the area of the joint portion of each member constituting an ink jet head has become smaller.

As a result, the joint strength of the joint portion of each member is likely to be reduced, and in an ink jet head using a piezoelectric element, the joint portion between the piezoelectric element driven to generate pressure in the ink chamber and the diaphragm that transmits the driving displacement as vibration to the ink chamber vibrates at a high speed in accordance with the driving of the piezoelectric element. Therefore, the joint between the piezoelectric element and the diaphragm is particularly likely to cause a decrease in the joint strength, and further, the piezoelectric element and the diaphragm are likely to be peeled off, which leads to a problem of low reliability.

To solve this problem, the following prior art is disclosed, and the description will be given with reference to fig. 1. Fig. 1 is an enlarged cross-sectional view of a joint position between a piezoelectric element and a diaphragm in a conventional inkjet head 100 a.

Patent document 2 discloses a technique of roughening a bonding surface of a bonding portion 82a of a diaphragm 8a to a piezoelectric element 5a, as shown in fig. 1. In this technique, since the adhesive material enters the roughened surface (joint surface) and is cured by roughening the surface of the joint portion 82a, the adhesive material layer 9a is formed, and thus the joint strength can be improved by obtaining the anchor effect. However, this roughening step is complicated because it is performed by chemical or electrochemical treatment after the diaphragm 8a is formed. Further, since the vibrating plate 8a is an extremely thin member of several μm to several tens μm, a process margin of the roughening treatment amount becomes narrow, and process control becomes difficult. That is, if there is variation in the process, the bonding surface of the bonding portion 82a to the piezoelectric element 5a is excessively roughened, the film thickness becomes excessively thin, and there is a problem that a pinhole is generated or the roughening is insufficient and sufficient bonding strength cannot be obtained.

The present disclosure has been made to solve the above-described problems of the conventional technique, and an object thereof is to provide an ink jet head having high reliability, which can improve the bonding strength between a diaphragm and a piezoelectric element at low cost without performing an additional step such as a roughening step.

In order to achieve the above object, an inkjet head according to one aspect of the present disclosure includes: a piezoelectric element; a vibrating plate; and an adhesive material layer disposed between the piezoelectric element and the vibration plate, and joining the piezoelectric element and the vibration plate, wherein the adhesive material layer contains beads having a higher hardness than the vibration plate, and a film thickness of the adhesive material layer is smaller than a particle diameter of the beads.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The embodiments described below are all general or specific examples. The numerical values, shapes, materials, constituent elements, arrangement positions and connection manners of the constituent elements, steps, order of the steps, and the like shown in the following embodiments are examples, and are not intended to limit the present disclosure. Further, among the components in the following embodiments, components not recited in the independent claims will be described as arbitrary components.

The drawings used in the description are schematic drawings, and are not necessarily strictly drawings. Note that substantially the same components are denoted by the same reference numerals, and redundant description may be omitted or simplified.

(embodiment mode 1)

First, embodiment 1 in the present disclosure will be described with reference to fig. 2. Fig. 2 shows a cross-sectional view of the inkjet head 100 according to embodiment 1 of the present disclosure.

< ink jet head 100>

Fig. 2 (a) is a cross-sectional view of the inkjet head 100 of the present disclosure, which shows a cross-section cut along a plane along the direction in which the plurality of nozzles 2 are arranged and along the ink ejection direction. In the inkjet head 100, both ends in the arrangement direction of the plurality of nozzles 2 are cut and omitted. The inkjet head 100 of the present embodiment includes at least a nozzle plate 1, a flow path forming substrate 4, a piezoelectric element 5, a vibration plate 8, and a base 10.

Further, a plurality of nozzles 2 are formed in the nozzle plate 1. The flow path forming substrate 4 includes a partition wall, and the pressure generating chamber 3 communicating with the nozzle 2 is defined by the partition wall. The piezoelectric element 5 includes a driving unit 6 provided in a region corresponding to each pressure generation chamber 3, and a pillar 7 provided in a region corresponding to each partition wall of the flow path forming substrate 4.

The vibration plate 8 is provided at a position that separates the flow path forming substrate 4 from the piezoelectric element 5. The inkjet head 100 further includes a housing (not shown) that holds the outer peripheries of these members and has a flow path for supplying ink to the flow path forming substrate 4.

Fig. 2 (a) is an enlarged view of a portion (region b shown in the figure) where the diaphragm 8 and the piezoelectric element 5 are joined together, as shown in fig. 2 (b). As shown in fig. 2 (b), an adhesive material layer 9 is used for bonding the diaphragm 8 and the piezoelectric element 5. In the layer of bonding material 9 beads 11 are contained as shown in the figure.

< nozzle plate 1 and nozzle 2>

The nozzle plate 1 has a plurality of nozzles 2 formed on a substrate at desired number and intervals. As a method of forming the plurality of nozzles 2 in the nozzle plate 1, there are laser processing, drilling processing, press processing, etching, electroforming, and the like. Considering the degree of freedom in processing the shape of the nozzle 2, the ease of shape control, and the like, it is preferable to form the nozzle 2 by laser processing.

Further, a water-repellent film may be formed on the surface of the nozzle plate 1 on the side facing the object to be coated. Such a waterproofing membrane has the following effects: when ink is ejected, ink slightly oozing out due to wetting and spreading is returned to the nozzles 2 in the vicinity of the nozzles 2 on the surface of the nozzle plate 1. For example, if ink seeping out near the nozzle 2 remains, the meniscus on the ink surface is broken, and the subsequent ink ejection is adversely affected, so that the formation of the water repellent film is effective for maintaining stable ejection. Examples of the method for forming the water-repellent film include a method in which a solution of alkoxysilane having fluorine is applied to the nozzle plate 1 and fired, and a method in which a monomer having fluorine is gas-layer polymerized. Further, the material for the waterproof film is also not particularly limited.

The material of the nozzle plate 1 can be, for example, a thin plate of metal such as stainless steel or ceramic. Here, the nozzle plate 1 is a member closest to the side of the workpiece to be printed (i.e., the object to be coated) in the inkjet head 100. Therefore, when the nozzle plate 1 is made of a thin ceramic plate, the nozzle plate 1 may be broken if the ink jet head 100 comes into contact with a workpiece to be printed due to some trouble, and therefore, the nozzle plate 1 is preferably made of a metal such as stainless steel. In addition, in the case where such a failure is not likely to occur in the ink ejection, the nozzle plate 1 may be configured using any of the materials described above.

The number and the interval of the plurality of nozzles 2 formed in the nozzle plate 1 are determined by the pattern shape of an electronic device, an optical device, or the like to be manufactured, but the pattern shape tends to be finer for higher performance of the electronic device, the optical device, or the like. Therefore, the number of nozzles 2 required for the inkjet head 100 is increased and the interval is decreased, and therefore, the nozzles 2 need to be densified. In particular, it may be required that the nozzles 2 are spaced at a very high density, for example on the order of 0.1mm to 0.2 mm. Further, the nozzle diameter is also reduced in accordance with the miniaturized pattern shape, and for example, a very small nozzle 2 of 10 μm to 20 μm is required.

< pressure generating chamber 3 and flow channel Forming substrate 4>

The flow path forming substrate 4 is a member in which partition walls corresponding to the arrangement of the nozzles are provided at equal intervals on the substrate. The spaces formed between the respective partitions become pressure generation chambers 3, and ink is supplied to the pressure generation chambers 3 from a common channel (not shown) disposed in the depth direction of the paper surface of fig. 2. The channel forming substrate 4 can be formed by a method such as laser processing or etching.

Further, depending on the structure of the flow path forming substrate 4, the flow path forming substrate may be manufactured by a method in which a plurality of substrates processed separately are stacked to form one flow path forming substrate 4. The nozzle plate 1 and the flow path forming substrate 4 can be bonded by metal bonding, an adhesive material, or the like. When an adhesive material is used, the type of the adhesive material is not particularly limited, and a thermosetting adhesive material, a two-liquid mixing type adhesive material, an ultraviolet curing type adhesive material, an anaerobic adhesive material, an adhesive material which cures by the combined effect of these materials, or the like can be used.

The material of the flow path forming substrate 4 can be metal such as stainless steel, ceramic, or the like, but when the nozzle plate 1 is bonded using a thermosetting adhesive material, the nozzle plate 1 and the flow path forming substrate 4 are preferably made of the same material in order to prevent displacement and warpage due to a difference in thermal expansion coefficient. The nozzle plate 1 and the flow path forming substrate 4 are preferably formed using a stainless steel material.

< piezoelectric element 5>

The piezoelectric element 5 is composed of a front surface electrode, a back surface electrode, an internal electrode, and a piezoelectric body. More specifically, the piezoelectric element 5 is configured by further stacking a plurality of unit elements, and each unit element is formed by stacking a piezoelectric body, an internal electrode connected to a front surface electrode, a piezoelectric body, and an internal electrode connected to a rear surface electrode in this order. Therefore, the internal electrodes connected to the front surface electrode and the rear surface electrode are formed as two types of comb-teeth-shaped internal electrodes that mesh with each other, and a piezoelectric body made of lead zirconate titanate or the like is laminated so as to be sandwiched therebetween.

The front electrode and the back electrode are disposed on the side surface of the elongated shape formed by the laminated piezoelectric layers, and the same type of internal electrodes included in each unit element are electrically connected to the two types of internal electrodes, respectively. More specifically, the laminated piezoelectric layer is a rectangular parallelepiped, and the front surface electrode and the back surface electrode are formed on surfaces (front and back surfaces on the paper surface in fig. 2) facing away from each other on the side surfaces of the rectangular parallelepiped.

In other words, the two types of internal electrodes are formed so as to overlap and partially overlap each of the layers constituting the stacked unit cell in a staggered manner, and are arranged so as to be alternately connected to the front surface electrode and the rear surface electrode along the longitudinal direction.

In the piezoelectric element 5, since the internal electrodes connected to the front surface electrodes and the internal electrodes connected to the back surface electrodes are alternately arranged along the longitudinal direction, when a potential difference is generated between the front surface electrodes and the back surface electrodes, the piezoelectric element 5 expands and contracts in the vertical direction on the paper surface of fig. 2 in accordance with the potential difference.

Further, a plurality of channels corresponding to the arrangement of the nozzles 2 are arranged in the piezoelectric element 5. Grooves are present between the channels, and such grooves are formed by cutting the piezoelectric element 5 into a single body and then dividing the plurality of channels, and the channels are insulated from each other by the grooves. The channel is connected to a flexible cable, driven in response to an input signal, and includes a driving unit 6 disposed below the pressure generation chamber 3 and generating displacement of the channel, and a column 7 disposed below a partition wall of the flow path forming substrate 4 and supporting the flow path forming substrate 4. The driving portions 6 and the column portions 7 are alternately arranged. The piezoelectric element 5 is supported by a base 10 as a base made of ceramic, metal, or the like.

< vibration plate 8>

The vibration plate 8 vibrates by the displacement generated in the driving portion 6 of the piezoelectric element 5, and varies the volume inside the pressure generation chamber 3, thereby generating pressure in the ink filled inside the pressure generation chamber 3 and ejecting the ink from the nozzle 2.

Here, in the present embodiment, the vibrating plate 8 is made of resin. When the vibration plate 8 is made of a soft resin, the tops of the beads kneaded in the adhesive material slightly sink into the vibration plate 8 made of the resin when the vibration plate 8 is bonded to the piezoelectric element 5 described later. This can provide an anchor effect to the adhesive layer 9, and can improve the adhesion strength between the adhesive layer 9 and the diaphragm 8.

The material of the resin constituting the diaphragm 8 is not particularly limited, but a material having high chemical resistance is preferable because the pressure generation chamber 3 side of the diaphragm 8 is a surface that contacts ink. Examples of such a material include polyamide, polyimide, polyamideimide, polyetherimide, polyethersulfone, polyetherketone, polyetheretherketone, and fluororesin. In particular, polyimide is widely used in electronic circuit applications, and products that can be easily microfabricated using photolithography techniques such as coating and etching have been developed and can be suitably used for the applications of the present disclosure. Since the material of the vibrating plate 8 which is most suitable varies depending on the solvent, functional material, and the like used in the ink, the vibrating plate 8 can be configured by appropriately selecting from various materials which are not limited.

The thickness of the vibrating plate 8 is not particularly limited as long as it is a thickness that can vibrate by the displacement generated by the driving portion 6 of the piezoelectric element 5 and can generate pressure on the ink filled in the pressure generation chamber 3 by changing the volume inside the pressure generation chamber 3. For example, as long as the film is about 1 μm or more and 100 μm or less, the film thickness can be optimally selected according to the softness of the resin constituting the vibration plate 8 and the ink ejection characteristics of the vibration plate 8.

The hardness of the vibrating plate 8 is a hardness that allows the beads 11 described later to sink. This can be suitably used as long as the vibrating plate 8 has a young's modulus of 1GPa or more and 10GPa or less, for example. When the young's modulus of the vibration plate 8 is less than 1GPa, the beads 11 described later are too likely to sink into the vibration plate 8, and control of the pressing force at the time of bonding the vibration plate 8 is difficult, and when the young's modulus is more than 10GPa, the beads 11 cannot sufficiently sink into the vibration plate 8.

< adhesive Material layer 9>

The adhesive material layer 9 is a bonding layer having a predetermined film thickness (layer thickness) formed by curing an adhesive material used when the piezoelectric element 5 and the diaphragm 8 are bonded. Therefore, the adhesive material layer 9 is disposed between the piezoelectric element 5 and the diaphragm 8. In the present disclosure, the adhesive and the adhesive material layer 9 are referred to as an adhesive material when uncured, and are referred to as an adhesive material layer 9 when applied and cured to a predetermined film thickness.

As the type of adhesive material that can be used for the adhesive material layer 9, a thermosetting adhesive material, a two-liquid mixing type adhesive material, an ultraviolet curing type adhesive material, an anaerobic adhesive material, an adhesive material that cures by the effect of a combination of these materials, or the like can be used. In particular, since the epoxy adhesive material, which is one of thermosetting adhesive materials, can form the adhesive material layer 9 having relatively high hardness after curing, the displacement of the piezoelectric element 5 can be transmitted to the diaphragm 8 without being attenuated, and thus the epoxy adhesive material can be suitably used. Here, the adhesive material layer 9 contains the beads 11 as described above.

< beads 11>

The beads 11 contained in the adhesive material layer 9 are beads having a hardness higher than that of the vibrating plate 8, and are used by kneading the adhesive material before curing. As the beads 11 to be kneaded in the binder, ceramic beads such as zirconia, alumina, and silica, glass beads, metal beads, or the like can be used. In particular, beads used as spacer beads for liquid crystal displays have high accuracy of particle diameter and can be suitably used. Examples of such beads include "HIPRESICA (UBE EXSYMO co., LTD.)".

The particle diameter of the beads 11 is determined by the thickness (film thickness 91) of the adhesive material layer 9 to be formed, and for example, a particle diameter of several μm or more and several tens μm or less can be used. In the relationship between the film thickness 91 of the adhesive material layer 9 and the particle diameter of the beads 11, the film thickness 91 of the adhesive material layer 9 is smaller than the particle diameter of the beads 11.

The hardness of the beads 11 is a hardness capable of being trapped in the vibration plate 8. This can be suitably used, for example, as long as the beads 11 have a Young's modulus of 30GPa or more. When the young's modulus of the beads 11 is 30GPa or less, the indentation into the vibrating plate is insufficient as described later.

< effects >

The adhesive material mixed with the beads 11 is applied to the piezoelectric element 5 or the vibrating plate 8 by screen printing, flexography, gravure, or the like. In the case of applying the adhesive material on the piezoelectric element 5 side, the adhesive material may be applied as a full coat film on a flat surface, and then the piezoelectric element 5 may be pressed against the flat surface, and the adhesive material may be transferred to the surface to be contacted.

After that, the piezoelectric element 5 and the diaphragm 8 are aligned, and after pressing, the adhesive is cured by a curing method suitable for each adhesive used, thereby forming the adhesive layer 9 for bonding the piezoelectric element 5 and the diaphragm 8.

Here, as shown in fig. 2 (b), when pressed, the tops of the beads 11 on the diaphragm 8 side sink into the diaphragm 8, which is softer than the beads 11, deforming the surface, forming recesses 90 in the diaphragm 8, and the adhesive enters the recesses 90.

Here, the thickness 91 of the adhesive material layer 9 is set without taking into consideration the recessed portion 90 in which the bead 11 is recessed. That is, the film thickness 91 is a distance separating the facing surfaces of the piezoelectric element 5 and the diaphragm 8 from each other. Therefore, the film thickness 91 of the adhesive material layer 9 is smaller than the particle diameter of the beads 11 by the amount of the beads 11 being trapped.

By the adhesive material entering the recess 90, the cured adhesive material layer 9 can obtain an anchor effect, and the adhesive strength to the diaphragm 8 can be improved. That is, after the applied adhesive material is cured, a layer between the facing surfaces of the piezoelectric element 5 and the diaphragm 8 having the film thickness 91 used for bonding and a portion entering the recess 90 to obtain an anchor effect are formed. Therefore, the adhesive layer 9 adhered to the piezoelectric element 5 and the diaphragm 8 are firmly adhered by the anchor effect, and thus the ink jet head 100 having high bonding strength and high reliability between the piezoelectric element 5 and the diaphragm 8 can be realized.

As described above, the ink jet head 100 according to the present embodiment includes the piezoelectric element 5, the vibration plate 8, and the adhesive layer 9 disposed between the piezoelectric element 5 and the vibration plate 8 to bond the piezoelectric element 5 and the vibration plate 8, wherein the adhesive layer 9 contains the beads 11 having a higher hardness than the vibration plate 8, and the thickness 91 of the adhesive layer 9 is smaller than the particle diameter of the beads 11.

In the ink jet head 100 having such a configuration, since the adhesive layer 9 is strongly adhered to the diaphragm 8 by the anchor effect, the diaphragm 8 can be prevented from being peeled off from the adhesive layer 9. Therefore, the bonding strength between the other piezoelectric element 5 and the diaphragm 8 to which the adhesive layer 9 is bonded is increased, and a highly reliable inkjet head can be realized.

When the vibrating plate 8 is pressed by the beads 11 kneaded in the adhesive, the vibrating plate 8 having a hardness lower than that of the beads 11 (which is easily deformed) is deformed to form the recess 90, and thus the adhesive enters the recess 90. Therefore, since the adhesive material is cured to form the adhesive material layer 9 including the material entering the recess 90, the roughening process of the diaphragm 8 is not required, and the production of the inkjet head 100 can be easily realized.

For example, the vibrating plate 8 may be made of resin.

This makes it possible to form the diaphragm 8 made of resin having a lower hardness than ceramics, glass, metal, or the like that can be suitably used as the beads 11, and to increase the possibility of selecting beads 11 having a higher hardness than the diaphragm 8.

(embodiment mode 2)

Next, embodiment 2 in the present disclosure will be described with reference to fig. 3. Fig. 3 shows an ink jet head 100b according to embodiment 2 of the present disclosure.

< inkjet head 100b >

Fig. 3 (a) is a cross-sectional view of the inkjet head 100b of the present disclosure, showing the same cross-sectional view as fig. 2 (a).

The inkjet head 100b of the present embodiment includes at least a nozzle plate 1, a flow path forming substrate 4, a piezoelectric element 5, a vibration plate 8b, and a base 10.

Further, a plurality of nozzles 2 are formed in the nozzle plate 1. The flow path forming substrate 4 includes a partition wall, and the pressure generating chamber 3 communicating with the nozzle 2 is partitioned by the partition wall. The piezoelectric element 5 includes a driving unit 6 provided in a region corresponding to each pressure generation chamber 3, and a pillar 7 provided in a region corresponding to each partition wall of the flow path forming substrate 4.

The vibration plate 8b is provided at a position that separates the flow path forming substrate 4 from the piezoelectric element 5. The inkjet head 100 further includes a housing (not shown) that holds the outer peripheries of these members and has a flow path for supplying ink to the flow path forming substrate 4.

The above is the same configuration as embodiment 1, but the present embodiment differs from embodiment 1 in the configuration of the diaphragm 8 b. More specifically, the diaphragm 8b includes a vibrating portion 81 and a joint portion 82, and the joint portion 82 is thicker in a convex shape on the piezoelectric element 5 side than the vibrating portion 81 in accordance with the joint shape of the piezoelectric element 5. Therefore, the adhesive material layer 9b is disposed between the piezoelectric element 5 and the joint portion 82 of the diaphragm 8b, and the joint portion 82 and the piezoelectric element 5 are joined by the adhesive material layer 9 b.

Fig. 3 (b) is an enlarged view of a joint (an area b2 shown in the figure) between the diaphragm 8b and the piezoelectric element 5 in fig. 3 (a). The adhesive material layer 9b and the beads 11 are used for bonding the vibration plate 8b and the piezoelectric element 5. As a comparative example, an enlarged view of a portion similar to the region b2 of the inkjet head in the case where the joint 82 is not provided (that is, the same configuration as that of embodiment 1) is shown in fig. 3 (c).

In embodiment 1, the thickness of the vibrating plate 8 is, for example, about 1 μm to 100 μm. As described above, when pressed, the tops of the beads 11 on the vibrating plate 8 side sink into the vibrating plate 8, which is softer than the beads 11, and deform the surface, thereby forming the recesses 90 in the vibrating plate 8. At this time, for example, when the diaphragm 8 is relatively thin, the thickness of the diaphragm 8 corresponding to the amount of sinking exhibits a slight deformation 83 on the surface of the diaphragm 8 on the flow path forming substrate 4 side, as shown in fig. 3 (c). Therefore, the vibration characteristics of the vibrating plate 8, that is, the ejection characteristics of the inkjet head 100 may vary depending on the degree of deformation 83 of each nozzle 2.

The larger the thickness of the diaphragm 8, the smaller the deformation 83, and the more suppressed the variation in the ejection characteristics, but the larger the thickness of the diaphragm 8, the more rigid the diaphragm 8 is, and therefore the displacement of the piezoelectric element 5 is difficult to transmit.

< effects >

Therefore, in the present embodiment, as described above, the diaphragm 8b includes the vibrating portion 81 and the joint portion 82, and the joint portion 82 is formed to be convex and thick on the piezoelectric element 5 side of the vibrating portion 81 in accordance with the joint position and shape with the piezoelectric element 5, as shown in fig. 3 (b). This can suppress the deformation 83 of the surface of the vibrating plate 8b on the flow path forming substrate 4 side due to the trapping of the beads 11 without increasing the thickness of the vibrating portion 81.

The thickness 92 of the adhesive material layer 9b at this time is smaller than the particle diameter of the beads 11. In addition, as in embodiment 1, the thickness 92 of the adhesive material layer 9b is defined by the distance separating the facing surfaces of the piezoelectric element 5 and the diaphragm 8b, without considering the depression of the bead 11 into the recess 90 b.

Further, with the above configuration, when the pressing force at the time of bonding the piezoelectric element 5 and the diaphragm 8b varies, it is considered that the adhesive material is excessively compressed and protrudes wider than the width of the piezoelectric element 5 (the length of the piezoelectric element 5 in the array direction of the nozzles 2), and the protruding portion 93 is generated. It is also conceivable that such a protrusion 93 is formed due to a fluctuation in the amount of adhesive material applied. The protruding portion 93 can be designed not to contact the vibrating portion 81 by the height of the engaging portion 82 with respect to the vibrating portion 81. Therefore, the effect of suppressing the occurrence of variations in the vibration characteristics due to the inhibition of the operation of the vibration portion 81 when the adhesive material is cured can be obtained at the same time.

As a method for producing the resin diaphragm 8b composed of the vibrating portion 81 and the joint portion 82 as described above, for example, a method for producing a resin film by half etching by photolithography, a method for producing a laminated photosensitive resin such as photosensitive polyimide by patterning, a method for producing a resin film by transferring the shape of the joint portion 82 from a mold by a method such as embossing or embossing, or the like can be cited.

As described above, the vibration plate 8b included in the ink jet head 100b in the present embodiment includes the vibration portion 81 and the joint portion 82 that is convex and thick on the piezoelectric element 5 side with respect to the vibration portion 81, and the joint portion 82 and the piezoelectric element 5 are joined by the adhesive material layer 9 b.

(embodiment mode 3)

Next, embodiment 3 in the present disclosure will be described with reference to fig. 4. Fig. 4 shows a cross-sectional view of an inkjet head 100c according to embodiment 3 of the present disclosure.

< ink jet head 100c >

Fig. 4 is an enlarged view of the region b2 in fig. 3 (i.e., the same position as in fig. 3 b), but in fig. 4, the piezoelectric element 5c has a recess 51 on the bonding surface (the surface on the side of the diaphragm 8 b) facing the diaphragm 8b, as compared with fig. 3 b. That is, the present embodiment differs from embodiment 2 in that the bonding surface of the piezoelectric element 5c has (is formed with) the concave portion 51. Such a recessed portion 51 has a size that allows a part of the bead 11 kneaded in the adhesive to enter. Therefore, at least a part of the beads 11 is disposed in the recess 51.

Therefore, the beads 11 included in the adhesive material layer 9c are different in that they include the beads 11 located on the surface (the portion other than the recessed portion 51 in the bonding surface) of the piezoelectric element 5c and the beads 12 located in the recessed portion 51. As described later, the beads 11 located on the surface of the piezoelectric element 5c sink into the diaphragm 8b by a pressing force in the same manner as in

embodiments

1 and 2.

< effects >

By appropriately adjusting the shape and arrangement density of the recessed portions 51 described above, when the piezoelectric element 5c and the diaphragm 8b are pressed to be joined, the tops of the beads 11 on the surface of the piezoelectric element 5c on the diaphragm 8b side sink into the joining portions 82 of the diaphragm 8 that are softer than the beads 11. The sinking of the beads 11 deforms the surface of the joint 82 of the vibrating plate 8b, forming a recess 90b in the vibrating plate 8 b. On the other hand, the bead 12 located in the recess 51 is not recessed but comes into contact with the joint 82 of the vibration plate 8 at the top of the vibration plate 8b side. In the present embodiment, the adhesive material layer 9c having such a structure can be formed.

The thickness 94 of the adhesive material layer 9c at this time is smaller than the particle diameter of the beads 11 on the surface of the piezoelectric element 5 c. The film thickness 94 is also small relative to the particle diameter of the beads 12 located in the recessed portion. That is, the adhesive also enters the recess 51 so that the beads 11 sink into the diaphragm 8b and the beads 12 sink into the piezoelectric element 5 c.

As in the above-described embodiment, the thickness 94 of the adhesive material layer 9c is defined by the distance separating the facing surfaces of the piezoelectric element 5c and the diaphragm 8b, without considering the recess 90b into which the bead 11 is recessed and the recess 51. With the above configuration, the adhesive layer 9c that is sunk into the recesses 90b formed by the beads 11 on the surface of the piezoelectric element 5c can obtain an anchoring effect with respect to the diaphragm 8b, and the adhesive strength can be improved. Furthermore, since the adhesive material layer 9c further contains an adhesive material that enters the recessed portion 51 and is cured, an anchor effect can be obtained also for the piezoelectric element 5 c.

Further, the presence of the beads 12 located in the recess 51 facilitates control of the film thickness 94 during pressing for joining the piezoelectric element 5c and the diaphragm 8 b. More specifically, although the film thickness 94 is set to be gradually reduced by applying a pressing force for joining the piezoelectric element 5c and the vibrating plate 8b, the stress with respect to the applied pressure changes at the position of the top of the bead 12 on the vibrating plate 8b side, which is set to the film thickness 94. That is, it can be easily confirmed by torque management or the like that the film thickness 94 has been set to the position of the top of the bead 12, and control of the film thickness 94 becomes easy.

Such ease of controlling the film thickness 94 can suppress a problem that the adhesive material is excessively compressed by the pressing force for bonding the piezoelectric element 5c and the diaphragm 8b and is widened from the width of the piezoelectric element 5 c.

Since the piezoelectric element 5c is not a material having a smooth surface, such as a resin constituting the diaphragm 8b, but is a sintered body of ceramic, it originally has a concave-convex structure, and is smoothly processed by grinding of the concave-convex structure until bonding can be performed. Therefore, by merely optimizing the degree of processing by smoothing by grinding (leaving the uneven structure), the piezoelectric element 5c can be formed with a smooth surface (surface) suitable for bonding and also with the (remaining) recessed portion 51 formed in a part thereof. Therefore, in the formation of the recessed portion 51, an additional step for forming the recessed portion 51 is not required, and it is also possible to assume a reduction in processing time by omitting a part of grinding.

In addition, although the diaphragm 8 of fig. 4 has the joint 82 as in fig. 3 (b), the piezoelectric element 5c may be joined to the diaphragm without the joint 82 in the present embodiment.

As described above, the piezoelectric element 5c included in the inkjet head 100c according to the present embodiment has the recessed portion 51 on the bonding surface facing the diaphragm 8b, and at least a part of the beads 11 and 12 (the beads 12) is disposed in the recessed portion 51.

As a result, the adhesive material entering the recessed portion 51 is cured, and the adhesive material layer 9c can obtain an anchor effect with respect to the piezoelectric element 5c, and can improve the adhesive strength with respect to the piezoelectric element 5 c. Further, the film thickness 94 can be easily controlled at the position where the bead 12 entering the recess 51 contacts the piezoelectric element 5 c-side surface of the joint portion 82 of the vibration plate 8 b.

(embodiment mode 4)

Further, embodiment 4 of the present disclosure will be described below with reference to fig. 5. Fig. 5 shows an inkjet head 100d according to embodiment 4 of the present disclosure.

< inkjet head 100d >

Fig. 5 is an enlarged view of the region b2 in fig. 3 (i.e., fig. 3 (b)) and a sectional view of the same position as in fig. 4. Fig. 5 shows a portion where the vibrating plate 8b is joined to the piezoelectric element 5 when the beads 11 shown in fig. 3 (b) are not beads having a single particle diameter but beads having a particle diameter distribution, beads in which a plurality of beads 11 having a single particle diameter are mixed, or the like.

That is, the beads used in the present embodiment include at least the 1 st beads 13 and the 2 nd beads 14 having different particle diameters. This is different from the other embodiments described above.

The adhesive material obtained by kneading the 1 st bead 13 having the largest particle diameter and the 2 nd bead 14 having a smaller particle diameter than the 1 st bead 13 among the plurality of beads is applied to any one of the bonding portions 82 in the structure including the piezoelectric element 5 and the bonding portions 82, similarly to fig. 2 (b). Then, the piezoelectric element 5 and the diaphragm 8b are aligned, and after pressing, the adhesive is cured by a curing method suitable for the adhesive used, respectively, to bond the piezoelectric element 5 and the diaphragm 8 b.

In addition, the diaphragm 8b in fig. 5 is drawn in the case where the joint 82 is present, as in fig. 3 (b), but the piezoelectric element 5c may be joined to the diaphragm without the joint 82 in the present embodiment.

< effects >

By appropriately adjusting the concentration (bead number concentration) of the 1 st bead 13 and the 2 nd bead 14, when the piezoelectric element 5 is pressed to be bonded to the vibrating plate 8b, the top of the 1 st bead 13 on the vibrating plate 8b side is recessed into the vibrating plate 8b which is softer than the 1 st bead 13, and a recess 90b is formed in the surface of the vibrating plate 8 b. On the other hand, the 2 nd bead 14 is not sunk but is in contact with the vibrating plate 8b at the top of the vibrating plate 8b side.

That is, the relation of the film thickness 95 of the 1 st bead 13, the 2 nd bead 14 and the adhesive material layer 9d is such that the film thickness 95 of the adhesive material layer 9d is smaller than the particle diameter of the 1 st bead 13 which is larger than the particle diameter of the 2 nd bead 14. In the present embodiment, the adhesive material layer 9d having such a structure can be formed.

The thickness 95 of the adhesive material layer 9d at this time is smaller than the particle diameter of the 1 st bead 13. The film thickness 95 is substantially uniform with respect to the particle diameter of the 2 nd bead 14. That is, the 1 st bead 13 sinks into the vibration plate 8b, and the 2 nd bead 14 is sandwiched between the surface of the piezoelectric element 5 and the surface of the bonding portion 82 where the recess 90b is not formed.

As in the above-described embodiment, the thickness 94 of the adhesive material layer 9c is defined by the distance separating the facing surfaces of the piezoelectric element 5 and the diaphragm 8b, without taking into account the recess 90b into which the bead 11 is recessed.

Due to the presence of the 2 nd beads 14, the control of the film thickness 95 is easier than in the case of a single particle diameter. More specifically, although the film thickness 95 is set to be gradually reduced by applying a pressing force for bonding the piezoelectric element 5 and the vibration plate 8b, the stress with respect to the applied pressure changes at the position where the particle diameter of the 2 nd bead 14 is set in the film thickness 95. That is, it can be easily confirmed by torque control or the like that the film thickness 95 reaches the particle diameter of the 2 nd bead 14, and control of the film thickness 95 becomes easy.

Such ease of controlling the film thickness 95 can suppress the adhesive material from being excessively compressed by the pressing for bonding the piezoelectric element 5 and the diaphragm 8b and from being bonded and cured wider than the width of the piezoelectric element 5. Therefore, the protruding and cured adhesive can be prevented from inhibiting the vibration of the diaphragm 8 b. In addition, the 2 nd beads 14 may also contain beads of a plurality of particle sizes. That is, the film thickness 95 can be determined depending on the maximum particle diameter of the 2 nd beads 14, and the 2 nd beads 14 having a predetermined particle diameter or less to be used as the film thickness 95 may be used. In other words, since the particle size of the 2 nd beads 14 is easier to control than that of the 1 st beads 13, inexpensive (rough particle size control) beads can be used.

In addition, in the case of using the 2 nd bead 14 having a plurality of particle diameters as described above, the film thickness 95 corresponding to which particle diameter of the 2 nd bead 14 is to be controlled in more stages by the applied pressure.

As described above, the beads 11 included in the inkjet head 100d according to the present embodiment include the 1 st beads 13 and the 2 nd beads 14 having different particle diameters, and the film thickness 95 is smaller than the particle diameter of the 1 st beads 13 larger than the particle diameter of the 2 nd beads 14.

Accordingly, since the piezoelectric element 5 does not have the recess 51 and the film thickness 95 can be easily controlled, the reliability of bonding between the piezoelectric element 5 and the diaphragm 8b can be ensured, and an ink jet head having desired ejection characteristics can be easily realized.

(other embodiments)

The embodiments have been described above, but the present disclosure is not limited to the embodiments.

In the above-described embodiment, the structural elements constituting the inkjet head are exemplified, but the functions of the structural elements included in the inkjet head may be arbitrarily distributed to a plurality of portions constituting the inkjet head.

The present disclosure also includes embodiments obtained by implementing various modifications that can be conceived by those skilled in the art to each embodiment, or embodiments obtained by arbitrarily combining the components and functions in each embodiment without departing from the scope of the present disclosure.

For example, although the present disclosure shows an example in which the

vibration plates

8 and 8b are made of resin, any material may be used as long as it has a lower hardness than the

beads

11 and 13.

For example, the diaphragm 8b is configured by the vibrating portion 81 and the joint portion 82, but the joint portion 82 may not be provided. For example, when the deformation 83 has a size (thickness) negligible with respect to the thickness of the vibrating plate, the joint 82 may not be provided. Alternatively, a piezoelectric element having a displacement characteristic capable of vibrating a diaphragm having a sufficient thickness to ignore the deformation 83 may be provided.

In addition, a plurality of embodiments 1 to 4 may be combined as desired to realize an ink jet head having high reliability.

Industrial applicability

According to the present disclosure, since an ink jet head with high reliability can be provided, it is useful to form a pattern of an electronic device or an optical device at low cost.

Claims

1. An ink jet head includes:

a piezoelectric element;

a vibrating plate; and

an adhesive material layer disposed between the piezoelectric element and the vibration plate to bond the piezoelectric element and the vibration plate,

the adhesive material layer contains beads having a higher hardness than the vibration plate, and the thickness of the adhesive material layer is smaller than the particle diameter of the beads.

2. An ink jet head according to claim 1,

the vibration plate is made of resin.

3. An ink jet head according to claim 1 or 2,

the vibrating plate is provided with:

a vibrating section; and

a joint portion that is convex and thick on the piezoelectric element side of the vibrating portion,

the bonding portion and the piezoelectric element are bonded through the adhesive material layer.

4. An ink jet head according to any of claims 1 to 3,

the piezoelectric element has a recess portion on a bonding surface facing the diaphragm,

at least a portion of the beads are disposed in the recess.

5. An ink jet head according to any of claims 1 to 3,

the beads include 1 st beads and 2 nd beads having different particle diameters,

the film thickness is smaller than the particle diameter of the 1 st bead which is larger than the particle diameter of the 2 nd bead.