JP2020082548A - Inkjet head - Google Patents

Abstract

To provide an inkjet head having high reliability.SOLUTION: An inkjet head 100 includes: a piezoelectric element 5; a diaphragm 8; and an adhesive layer 9 arranged between the piezoelectric element 5 and the diaphragm 8 to join the piezoelectric element 5 to the diaphragm 8. The adhesive layer 9 contains a bead 11 having hardness that is higher than the diaphragm 8. The adhesive layer 9 has a film thickness 91 that is smaller than a grain diameter of the bead 11.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to an inkjet head.

2. Description of the Related Art Among manufacturing processes of electronic devices and optical devices, a process of forming a fine pattern on a substrate by printing is often used. In printing a fine pattern, it is necessary to downsize and increase the density of a series of flow paths, a piezoelectric element, a vibration plate, etc. that are involved in ejecting an inked material. Further, conventionally, a technique for reducing the size and increasing the density of a piezoelectric element has been disclosed (for example, see Patent Document 1).

In Patent Document 1, in the lead-out wiring for driving the piezoelectric element, by narrowing the width of the adhesion layer for adhering the conductive layer, short-circuiting between the lead-out wirings adjacent to each other is suppressed even if the piezoelectric elements are arranged at high density. A possible liquid ejecting head is disclosed.

JP, 2018-027711, A JP, 10-34919, A

By the way, in ejecting ink using an inkjet head, the vibration plate and the piezoelectric element must be reliably joined. For example, when the reliability of such bonding is low, the diaphragm may be peeled off from the piezoelectric element, which may cause a problem that the designed ink ejection accuracy cannot be maintained.

Then, this indication aims at providing a highly reliable inkjet head.

One aspect of an inkjet head according to the present disclosure includes a piezoelectric element, a vibration plate, and an adhesive layer that is disposed between the piezoelectric element and the vibration plate and that bonds the piezoelectric element and the vibration plate. The adhesive layer contains beads having a hardness higher than that of the diaphragm, and the thickness of the adhesive layer is smaller than the particle diameter of the beads.

According to one aspect of the present disclosure, a highly reliable inkjet head is provided.

FIG. 1 is an enlarged sectional view of a conventional inkjet head. FIG. 2 is a sectional view of the inkjet head according to the first embodiment. FIG. 3 is a sectional view of the inkjet head according to the second embodiment. FIG. 4 is an enlarged cross-sectional view of the inkjet head according to the third embodiment. FIG. 5 is an enlarged cross-sectional view of the inkjet head according to the fourth embodiment.

(Knowledge that became the basis of disclosure)
As a method for forming a fine pattern at low cost, a printing method in which a material having a desired pattern is made into ink and printing is performed on a substrate, particularly an inkjet method which does not require a printing plate has been attracting attention. However, in recent years, the pitch between the nozzles in the nozzle row has become smaller in accordance with the demand for finer patterns formed by the inkjet method, and the area of the joint portion of each member constituting the inkjet head has become smaller accordingly.

As a result, the joint strength of the joint portion of each member is apt to be reduced, and in the ink jet head using the piezoelectric element, the piezoelectric element that drives to generate pressure in the ink chamber and the displacement of the drive as vibration cause the ink chamber to vibrate. The joint portion with the vibration plate that transmits to the element vibrates at high speed in accordance with the driving of the piezoelectric element. Therefore, there is a problem that the joint strength between the piezoelectric element and the vibrating plate is particularly lowered, and the piezoelectric element and the vibrating plate are likely to be peeled off from each other, resulting in low reliability.

The following prior art has been published for this problem and will be described with reference to FIG. FIG. 1 is an enlarged cross-sectional view of a joint portion between a piezoelectric element and a vibration plate in a conventional inkjet head 100a.

In Patent Document 2, as shown in FIG. 1, a technique is disclosed in which the joint surface of the joint portion 82a of the diaphragm 8a and the piezoelectric element 5a is roughened. In this technique, the adhesive material enters the roughened surface (joint surface) and is hardened by roughening the surface of the joint portion 82a to form the adhesive layer 9a. It is said that it can be increased. However, the roughening process is complicated because it is performed by chemical or electrochemical treatment after forming the vibration plate 8a. Further, since the vibration plate 8a is an extremely thin member having a thickness of several μm to several tens of μm, the process margin of the roughening processing amount becomes narrow, and it is difficult to control the process. In other words, if there are variations in the process, the joint surface of the joint portion 82a with the piezoelectric element 5a is excessively roughened and the film thickness is too thin, pinholes are generated, or roughening is insufficient, resulting in sufficient joint strength. There is a problem that it may not be obtained.

The present disclosure solves the above-described problems in the conventional technology, and provides a highly reliable inkjet head that enhances the bonding strength between a diaphragm and a piezoelectric element at low cost without additional steps such as a roughening step. The purpose is to do.

In order to achieve the above object, an inkjet head according to an aspect of the present disclosure includes a piezoelectric element, a vibration plate, and an adhesive layer that is arranged between the piezoelectric element and the vibration plate and that bonds the piezoelectric element and the vibration plate. , And the adhesive layer contains beads having a hardness higher than that of the diaphragm, and the thickness of the adhesive layer is smaller than the particle diameter of the beads.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. It should be noted that each of the embodiments described below shows a comprehensive or specific example. Numerical values, shapes, materials, components, arrangement positions and connection forms of components, steps, order of steps, and the like shown in the following embodiments are examples, and are not intended to limit the present disclosure. Further, among the constituent elements in the following embodiments, constituent elements not described in independent claims are described as arbitrary constituent elements.

Moreover, each drawing used for the description is a schematic view, and is not necessarily strictly illustrated. Further, in each of the drawings, substantially the same configurations are denoted by the same reference numerals, and redundant description may be omitted or simplified.

(Embodiment 1)
First, the first embodiment of the present disclosure will be described using FIG. 2. FIG. 2 shows a cross-sectional view of the inkjet head 100 according to Embodiment 1 of the present disclosure.

<Inkjet head 100>
FIG. 2A is a cross-sectional view of the inkjet head 100 of the present disclosure, and shows a cross section cut along a plane along the arrangement direction of the plurality of nozzles 2 and the ink ejection direction. In addition, both ends of the inkjet head 100 in the arrangement direction of the plurality of nozzles 2 are broken and omitted. The inkjet head 100 according to the present embodiment includes at least the nozzle plate 1, the flow path forming substrate 4, the piezoelectric element 5, the vibrating plate 8, and the base 10.

A plurality of nozzles 2 are formed on the nozzle plate 1. The flow path forming substrate 4 includes a partition wall, and the partition wall defines a pressure generating chamber 3 communicating with the nozzle 2. The piezoelectric element 5 has a drive unit 6 provided in a region corresponding to each pressure generating chamber 3, and a column portion 7 provided in a region corresponding to each partition wall of the flow path forming substrate 4.

The vibrating plate 8 is provided at a position separating the flow path forming substrate 4 and 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.

Further, FIG. 2B is an enlarged view of a portion (a region b shown in the drawing) where the vibration plate 8 and the piezoelectric element 5 of FIG. 2A are joined. As shown in FIG. 2B, the adhesive layer 9 is used for joining the vibration plate 8 and the piezoelectric element 5. The adhesive layer 9 contains beads 11 as shown in the figure.

<Nozzle plate 1 and nozzle 2>
The nozzle plate 1 is formed by forming a plurality of nozzles 2 on a substrate at a desired number and intervals. Examples of methods for forming the plurality of nozzles 2 on the nozzle plate 1 include laser processing, drill processing, press processing, etching method, and electroforming method. Considering the degree of processing freedom of the shape of the nozzle 2 and the ease of shape control, the nozzle 2 is preferably formed by laser processing.

A water-repellent film may be formed on the surface of the nozzle plate 1 facing the object to be coated. Such a water-repellent film has a function of returning, to the inside of the nozzle 2, ink that has slightly exuded due to wetting and spreading on the surface of the nozzle plate 1 in the vicinity of the nozzle 2 during ink ejection. For example, when the ink that oozes out in the vicinity of the nozzle 2 remains, the meniscus on the ink surface collapses and adversely affects the next ink ejection. Therefore, the formation of the water repellent film is effective for maintaining stable ejection. .. As a method of forming the water-repellent film, there are a method of applying a solution of a fluorine-containing alkoxysilane to the nozzle plate 1 and baking the solution, a method of forming the water-repellent film by vapor layer polymerization of a fluorine-containing monomer, and the like. However, it is not limited to these. The material used for the water repellent film is not particularly limited.

As the material of the nozzle plate 1, for example, a thin plate of metal such as stainless steel or ceramic can be used. Here, the nozzle plate 1 is a member that is closest to the print work (that is, the application target) side in the inkjet head 100. Therefore, when the nozzle plate 1 is made of a ceramic thin plate, if the inkjet head 100 comes into contact with the print work due to some trouble, the nozzle plate 1 may be cracked. Therefore, the nozzle plate 1 is made of metal such as stainless steel. It is preferably formed. If there is no possibility of such a trouble in ink ejection, the nozzle plate 1 may be made of any of the above materials.

Further, the number and intervals of the plurality of nozzles 2 formed in the nozzle plate 1 are determined by the pattern shape of the intended use such as an electronic device, an optical device, etc., but in order to improve the performance of the electronic device, the optical device, etc., The pattern shape tends to be miniaturized. Therefore, the number of nozzles 2 required for the inkjet head 100 increases and the interval becomes smaller, so that the nozzles 2 need to be densified. In particular, the distance between the nozzles 2 may be required to be extremely high, for example, about 0.1 mm to 0.2 mm. Further, the nozzle diameter is also reduced in accordance with the pattern shape to be miniaturized, and a very small nozzle 2 such as 10 μm to 20 μm is required.

<Pressure generating chamber 3 and flow path forming substrate 4>
The flow path forming substrate 4 is a member in which partition walls according to the nozzle arrangement are provided on the substrate at equal intervals. The space formed between each partition wall serves as a pressure generating chamber 3, and ink is supplied to the pressure generating chamber 3 from a common channel (not shown) arranged in the front and back direction of the paper surface of FIG. To be done. Similarly, the flow path forming substrate 4 can be formed by a method such as laser processing and etching.

Further, depending on the structure of the flow path forming substrate 4, it may be manufactured by a method of stacking a plurality of substrates processed separately 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 or an adhesive material. When an adhesive is used, the type of the adhesive is not particularly limited, but a thermosetting adhesive, a two-component adhesive, an ultraviolet curable adhesive, an anaerobic adhesive, or an adhesive that is cured by the combined effect of these. Etc. can be used.

The material of the flow path forming substrate 4 may be metal such as stainless steel or ceramics, but when it is bonded to the nozzle plate 1 by using a thermosetting adhesive, in order to prevent deviation or warpage due to a difference in thermal expansion coefficient. The nozzle plate 1 and the flow path forming substrate 4 are preferably made of the same material. Further, it is more preferable that the nozzle plate 1 and the flow path forming substrate 4 are made of a stainless material.

<Piezoelectric element 5>
The piezoelectric element 5 includes 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 in which a piezoelectric body, an internal electrode connected to a front surface electrode, a piezoelectric body, and an internal electrode connected to a back surface electrode are stacked in this order. It Therefore, the internal electrodes connected to the front surface electrode and the back surface electrode respectively form two comb-shaped internal electrodes that mesh with each other, and a piezoelectric body made of lead zirconate titanate or the like is formed between them. It is laminated in an intervening form.

The front surface electrode and the back surface electrode are arranged on a long side surface formed by the stacked piezoelectric layers, and the two kinds of internal electrodes are electrically connected to the same kind of internal electrodes included in each unit element. More specifically, the laminated piezoelectric layer is a rectangular parallelepiped here, and a front surface electrode and a back surface electrode are formed on each of the side surfaces of the rectangular parallelepiped facing each other (front and back surfaces of the paper in FIG. 2). Has been done.

In other words, the two kinds of internal electrodes are formed such that the layers are alternately stacked and the parts are alternately stacked on each layer constituting the laminated unit element, and the two kinds of internal electrodes are alternately arranged on the surface along the longitudinal direction. It is arranged so as to be connected to the electrode and the back electrode.

Since the internal electrodes connected to the front surface electrodes and the internal electrodes connected to the back surface electrodes are alternately arranged in the piezoelectric element 5 along the longitudinal direction, a potential difference is generated between the front surface electrodes and the back surface electrodes. Then, the piezoelectric element 5 expands and contracts in the vertical direction of the paper surface of FIG. 2 according to the potential difference.

Further, the piezoelectric element 5 is provided with a plurality of channels arranged according to the arrangement of the nozzles 2. Grooves exist between the respective channels, and such grooves are formed by integrally forming the piezoelectric element 5 and then performing dicing processing to divide the plurality of channels. The channels are isolated and insulated by the groove. Further, this channel is connected to a flexible cable, is driven according to an input signal, and causes displacement of the channel. The drive unit 6 is disposed below the pressure generating chamber 3 and the partition wall of the flow path forming substrate 4. And a column 7 that supports the flow path forming substrate 4. In addition, the drive part 6 and the pillar part 7 are arrange|positioned by turns. The piezoelectric element 5 is supported by a base 10 which is a base made of ceramic or metal.

<Vibration plate 8>
The vibrating plate 8 vibrates due to the displacement generated in the driving unit 6 of the piezoelectric element 5 and changes the volume inside the pressure generating chamber 3 to generate pressure in the ink filled in the pressure generating chamber 3 and Ink is ejected from 2.

Here, in the present embodiment, diaphragm 8 is made of resin. By forming the vibrating plate 8 with a flexible resin, the tops of the beads kneaded with the adhesive when the vibrating plate 8 and the piezoelectric element 5, which will be described later, are slightly cut into the vibrating plate 8 made of resin. Thereby, the adhesive layer 9 can obtain an anchor effect, and the adhesive strength between the adhesive layer 9 and the diaphragm 8 can be increased.

There is no particular limitation on the material of the resin forming the vibrating plate 8, but since the pressure generating chamber 3 side of the vibrating plate 8 is the surface that contacts the ink, a material having high chemical resistance is preferable. Examples of such materials include polyamide, polyimide, polyamideimide, polyetherimide, polyethersulfone, polyetherketone, polyetheretherketone, and fluororesin. In particular, polyimide is widely used for electronic circuit applications, and a product that can be easily microfabricated by using a photolithography technique such as coating or etching has been developed, and can be suitably used for the application of the present disclosure. Since the most suitable material of the diaphragm 8 changes depending on the solvent used for the ink, the functional material, and the like, the diaphragm 8 can be appropriately selected from various materials that are not limited.

Further, the thickness of the vibration plate 8 can be vibrated by the displacement generated in the drive unit 6 of the piezoelectric element 5, and the volume filled in the pressure generating chamber 3 is changed, whereby the ink filled in the pressure generating chamber 3 is changed. There is no particular limitation as long as it is a film thickness capable of generating pressure. For example, the thickness may be about 1 μm or more and 100 μm or less, and the optimum film thickness can be selected based on the softness of the resin forming the diaphragm 8 and the ink ejection characteristics of the diaphragm 8.

Further, the hardness of the diaphragm 8 is such that beads 11 described below can bite into it. This can be suitably used, for example, if the diaphragm 8 has a Young's modulus of 1 GPa or more and 10 GPa or less. When the Young's modulus of the diaphragm 8 is smaller than 1 GPa, the beads 11 described below are too easy to bite into the diaphragm 8 to make it difficult to control the pressing force when the diaphragm 8 is joined, and it is larger than 10 GPa. In this case, the beads 11 do not fully dig into the diaphragm 8.

<Adhesive layer 9>
The adhesive material layer 9 is a bonding layer having a predetermined film thickness (layer thickness) formed by curing the adhesive material used when bonding the piezoelectric element 5 and the vibration plate 8. Therefore, the adhesive layer 9 is arranged between the piezoelectric element 5 and the vibration plate 8. In the present disclosure, the uncured adhesive and the adhesive layer 9 are referred to as an adhesive, and the adhesive and the adhesive layer 9 after being applied and cured to have a predetermined film thickness are referred to as an adhesive layer 9.

The type of adhesive that can be used for the adhesive layer 9 is a thermosetting adhesive, a two-component adhesive, an ultraviolet curable adhesive, an anaerobic adhesive, or an adhesive that cures due to the combined effect of these. Etc. can be used. In particular, since an epoxy adhesive, which is a kind of thermosetting adhesive, can form the adhesive layer 9 having a relatively high hardness after curing, the displacement of the piezoelectric element 5 can be transmitted to the diaphragm 8 without being attenuated. It can be used suitably. Here, the adhesive layer 9 contains the beads 11 as described above.

<Beads 11>
The beads 11 contained in the adhesive layer 9 are beads having a hardness higher than that of the vibration plate 8, and are used by kneading with the adhesive before curing. As the beads 11 to be kneaded with the adhesive material, ceramic beads such as zirconia, alumina, and silica, glass beads, or metal beads can be used. In particular, beads used as spacer beads for liquid crystal displays have high particle size accuracy and can be used preferably. As an example of such beads, "High Presica (manufactured by Ube Eximo Co., Ltd.)" and the like can be mentioned.

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

Further, the hardness of the beads 11 is a hardness that can be cut into the diaphragm 8 described above. For example, the beads 11 having a Young's modulus of 30 GPa or more can be preferably used. When the Young's modulus of the beads 11 is 30 GPa or less, biting into the diaphragm is insufficient as described later.

<Effect>
The adhesive material obtained by kneading the beads 11 is applied to the piezoelectric element 5 or the diaphragm 8 by screen printing, flexographic printing, gravure printing, or the like. When the adhesive is applied to the piezoelectric element 5 side, the adhesive is applied as a solid film on a flat surface, the piezoelectric element 5 is then pressed against the flat surface, and the adhesive is transferred to the contact surface. Can also be applied.

After that, the piezoelectric element 5 and the diaphragm 8 are aligned and pressed, and then the adhesive material is cured by a curing method suitable for each adhesive material used to bond the piezoelectric element 5 and the diaphragm 8 to each other. The adhesive layer 9 is formed.

Here, as shown in FIG. 2B, at the time of pressing, the top portion of the bead 11 on the side of the diaphragm 8 bites into the diaphragm 8 which is softer than the beads 11 to deform the surface, and The concave portion 90 is formed, and the adhesive material further enters the concave portion 90.

Here, the thickness 91 of the adhesive material layer 9 does not take into consideration the recess 90 in which the beads 11 bite. That is, the film thickness 91 is the distance between the opposing surfaces of the piezoelectric element 5 and the diaphragm 8. Therefore, the film thickness 91 of the adhesive layer 9 becomes smaller than the particle diameter of the beads 11 by the amount that the beads 11 bite.

The cured adhesive material layer 9 can obtain an anchor effect by the adhesive material that has entered the concave portion 90, and the adhesive strength to the diaphragm 8 can be increased. That is, after the applied adhesive is cured, it forms a layer between the opposing surfaces of the piezoelectric element 5 and the diaphragm 8 having a film thickness 91 used for bonding and a portion that enters the recess 90 and obtains the anchor effect. .. Therefore, due to the above anchor effect, the adhesive layer 9 adhered to the piezoelectric element 5 is firmly adhered to the vibration plate 8, so that the bonding strength between the piezoelectric element 5 and the vibration plate 8 is high and the inkjet is highly reliable. The head 100 is realized.

As described above, the inkjet head 100 according to the present embodiment is arranged between the piezoelectric element 5, the vibration plate 8, and the piezoelectric element 5 and the vibration plate 8, and bonds the piezoelectric element 5 and the vibration plate 8 to each other. The adhesive layer 9 includes a bead 11 having a hardness higher than that of the diaphragm 8, and the thickness 91 of the adhesive layer 9 is larger than the particle diameter of the bead 11. small.

In the inkjet head 100 having such a configuration, the adhesive layer 9 is firmly adhered to the diaphragm 8 by the anchor effect, so that the diaphragm 8 is prevented from being separated from the adhesive layer 9. Therefore, the bonding strength between the vibration plate 8 and the other piezoelectric element 5 to which the adhesive layer 9 is bonded is increased, and a highly reliable inkjet head is realized.

Further, when the vibration plate 8 is pressed by the beads 11 mixed with the adhesive material, the vibration plate 8 having a hardness lower than that of the beads 11 (easy to be deformed) is deformed to form the concave portion 90, so that the concave portion 90 is formed. The adhesive enters the. Therefore, since the adhesive material including the material that has entered the concave portion 90 is hardened and the adhesive material layer 9 is formed, the vibrating plate 8 does not need to be roughened, and the inkjet head 100 can be easily manufactured. Is.

Further, for example, the diaphragm 8 may be made of resin.

Thereby, the diaphragm 8 made of resin having a hardness lower than that of ceramic, glass, metal or the like which can be suitably used as the beads 11, can be configured, and the beads 11 having a hardness higher than that of the diaphragm 8 can be selected. You can broaden your sexuality.

(Embodiment 2)
Next, a second embodiment of the present disclosure will be described with reference to FIG. FIG. 3 shows an inkjet head 100b according to the second embodiment of the present disclosure.

<Inkjet head 100b>
3A is a cross-sectional view of the inkjet head 100b of the present disclosure, and shows a cross section in the same cross section as FIG. 2A.

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

A plurality of nozzles 2 are formed on the nozzle plate 1. The flow path forming substrate 4 includes a partition wall, and the partition wall defines a pressure generating chamber 3 communicating with the nozzle 2. The piezoelectric element 5 has a drive unit 6 provided in a region corresponding to each pressure generating chamber 3, and a column portion 7 provided in a region corresponding to each partition wall of the flow path forming substrate 4.

The vibrating plate 8b is provided at a position separating the flow path forming substrate 4 and 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.

Although the above is the same configuration as the first embodiment, the present embodiment is different from the first embodiment in the configuration of the diaphragm 8b. More specifically, the vibrating plate 8b is provided with a vibrating portion 81 and a joint portion 82 corresponding to the joint shape with the piezoelectric element 5 and being thicker in a convex shape on the piezoelectric element 5 side than the vibrating portion 81. .. Therefore, the adhesive layer 9b is arranged between the piezoelectric element 5 and the joint portion 82 of the vibration plate 8b, and the joint portion 82 and the piezoelectric element 5 are joined by the adhesive layer 9b.

FIG. 3B is an enlarged view of the joint portion (region b2 shown in the drawing) between the vibration plate 8b and the piezoelectric element 5 of FIG. 3A. The adhesive layer 9b and the beads 11 are used to join the vibration plate 8b and the piezoelectric element 5. As a comparative example, an enlarged view of a portion similar to the area b2 of the inkjet head in the case where the joining portion 82 is not provided (that is, the same configuration as that of the first embodiment) is shown in FIG.

In the first embodiment, the diaphragm 8 has a thickness of, for example, about 1 μm to 100 μm. As described above, at the time of pressing, the top portion of the bead 11 on the side of the vibration plate 8 bites into the vibration plate 8 which is softer than the beads 11 to deform the surface, and the recess 90 is formed in the vibration plate 8. At this time, for example, when the vibration plate 8 is relatively thin, the thickness of the vibration plate 8 that has been bitten in as shown in FIG. 3C is a slight deformation 83 on the surface of the vibration plate 8 on the flow path forming substrate 4 side. Appears as. Therefore, the vibration characteristic of the vibration plate 8, that is, the ejection characteristic of the inkjet head 100 may vary depending on the degree of deformation 83 of each nozzle 2.

The deformation 83 becomes smaller as the thickness of the vibration plate 8 becomes thicker, and variation in ejection characteristics is suppressed. However, if the thickness of the vibration plate 8 is made thicker, the rigidity of the vibration plate 8 increases, so that the displacement of the piezoelectric element 5 is transmitted. It becomes difficult to do.

<Effect>
Therefore, in the present embodiment, as described above, the vibrating plate 8b is more piezoelectric than the vibrating portion 81 in accordance with the vibrating portion 81 and the bonding position and shape with the piezoelectric element 5, as shown in FIG. 3B. A joint portion 82 thickened in a convex shape is provided on the element 5 side. Accordingly, it is possible to suppress the deformation 83 of the surface of the vibrating plate 8b on the side of the flow path forming substrate 4 due to the bite 11 without increasing the thickness of the vibrating portion 81.

The thickness 92 of the adhesive layer 9b at this time is smaller than the particle diameter of the beads 11. As in the first embodiment, the thickness 92 of the adhesive layer 9b is defined by the distance between the facing surfaces of the piezoelectric element 5 and the diaphragm 8b without considering the recess 90b in which the beads 11 bite. ..

Further, with the above configuration, when the pressing force at the time of joining the piezoelectric element 5 and the vibrating plate 8b varies, the adhesive material is crushed too much, so that the width of the piezoelectric element 5 (the arrangement direction of the nozzles 2). It is conceivable that the protruding portion 93 is generated by protruding beyond the length of the piezoelectric element 5). Further, it is assumed that such a protruding portion 93 is formed even when the application amount of the adhesive material varies. The protruding portion 93 can be designed so as not to come into contact with the vibrating portion 81 due to the height of the joint portion 82 with respect to the vibrating portion 81. Therefore, when the adhesive is cured, it is possible to obtain the effect that it is possible to suppress the operation of the vibrating portion 81 and suppress the variation of the vibration characteristics at the same time.

As a method of manufacturing the resin vibrating plate 8b composed of the vibrating portion 81 and the joint portion 82 as described above, for example, a method of half-etching a resin film by photolithography, a photosensitive polyimide Examples of the method include a method in which the photosensitive resin is patterned by stacking, and a method in which the shape of the bonding portion 82 is transferred from the mold to the resin film by a method such as imprinting or embossing.

As described above, the vibrating plate 8b included in the inkjet head 100b according to the present embodiment includes the vibrating portion 81 and the joint portion 82 that is convexly thicker than the vibrating portion 81 on the piezoelectric element 5 side. The bonding portion 82 and the piezoelectric element 5 are bonded by the adhesive material layer 9b.

(Embodiment 3)
Next, a third embodiment of the present disclosure will be described using FIG. FIG. 4 shows a cross-sectional view of the inkjet head 100c according to the third embodiment of the present disclosure.

<Inkjet head 100c>
4 is an enlarged view of the region b2 in FIG. 3 (that is, the same portion as FIG. 3B), but in comparison with FIG. 3B, in FIG. There is a recess 51 on the joint surface (the surface on the side of the diaphragm 8b) facing 8b. That is, the present embodiment is different from the second embodiment in that the joint surface of the piezoelectric element 5c has (is formed) the recess 51. Such a recess 51 is sized to allow a part of the beads 11 mixed with the adhesive to enter. Therefore, at least a part of the beads 11 is arranged in the recess 51.

Therefore, the beads 11 included in the adhesive material layer 9c are different in that there are the beads 11 located on the surface of the piezoelectric element 5c (a part of the bonding surface excluding the recess 51) and the beads 12 located in the recess 51. ing. As will be described later, the beads 11 located on the surface of the piezoelectric element 5c bite into the vibration plate 8b by the pressing force as in the first and second embodiments.

<Effect>
By appropriately adjusting the shape and arrangement density of the recesses 51 described above, the vibration plate 8b of the beads 11 located on the surface of the piezoelectric element 5c at the time of pressing for joining the piezoelectric element 5c and the vibration plate 8b. The top portion on the side digs into the joint portion 82 of the diaphragm 8 which is softer than the beads 11. The bead 11 biting deforms the surface of the joint portion 82 of the vibration plate 8b, and a concave portion 90b is formed in the vibration plate 8b. On the other hand, the beads 12 located in the recess 51 contact the joint portion 82 of the diaphragm 8 at the top portion on the diaphragm 8b side, but do not bite. In the present embodiment, the adhesive layer 9c having such a structure can be formed.

The thickness 94 of the adhesive layer 9c at this time is smaller than the particle diameter of the beads 11 located on the surface of the piezoelectric element 5c. Further, the film thickness 94 is also small with respect to the particle diameter of the beads 12 located in the depression. In other words, the bead 11 bites into the vibration plate 8b, and the bead 12 has a shape that bites into the piezoelectric element 5c side, and the adhesive also enters the recess 51.

As in the case of the above-described embodiment, the thickness 94 of the adhesive layer 9c does not consider the concave portion 90b in which the beads 11 bite, and does not consider the concave portion 51. The piezoelectric element 5c and the diaphragm 8b face each other. It is defined by the distance between the faces. With the above-described configuration, the adhesive layer 9c that has dented into the recess 90b generated by the beads 11 located on the surface of the piezoelectric element 5c can obtain an anchor effect with respect to the vibration plate 8b, and the adhesive strength. Can be increased. Further, since the adhesive layer 9c also contains the adhesive that has entered the recess 51 and hardened, an anchor effect can be obtained also for the piezoelectric element 5c.

Furthermore, the presence of the beads 12 located in the recess 51 facilitates the control of the film thickness 94 in the pressing for joining the piezoelectric element 5c and the vibration plate 8b. More specifically, the film thickness 94 is set gradually smaller by applying a pressing force for joining the piezoelectric element 5c and the vibration plate 8b. However, the film thickness 94 is set at the top of the bead 12 on the vibration plate 8b side. At the position, the stress against the applied pressure changes. That is, the fact that the setting of the film thickness 94 has reached the position of the top of the bead 12 can be easily confirmed by torque management or the like, and the film thickness 94 can be easily controlled.

Such ease of control of the film thickness 94 suppresses the problem that the adhesive material is crushed too much by the pressing force for joining the piezoelectric element 5c and the vibration plate 8b and is expanded more than the width of the piezoelectric element 5c. To be able to do.

Since the piezoelectric element 5c is not a material having a smooth surface such as a resin forming the diaphragm 8b but a ceramic sintered body, it has an uneven structure originally, and can be joined by grinding the uneven structure. Has been processed smoothly. For this reason, a smooth surface (surface) suitable for bonding is formed on the piezoelectric element 5c, and at the same time, a recessed portion 51 is formed on the piezoelectric element 5c only by optimizing the degree of smoothing processing by grinding (remaining the uneven structure). It is possible to do (remain). Therefore, in forming the recessed portion 51, an additional step for forming the recessed portion 51 is not particularly required, and it is also conceivable to shorten the processing time by partially omitting the grinding.

Note that the diaphragm 8 of FIG. 4 illustrates a case where there is a joint 82 as in FIG. 3B, but in the present embodiment, there is no joint 82 and the piezoelectric element 5c and the diaphragm are joined. It may be configured to be.

As described above, the piezoelectric element 5c included in the inkjet head 100c in the present embodiment has the recessed portion 51 on the joint surface facing the vibration plate 8b, and at least a part of the beads 11 and 12 (the beads 12). ) Is arranged in the recess 51.

As a result, the adhesive material that has entered the recessed portion 51 is cured, so that the adhesive material layer 9c can obtain an anchor effect with respect to the piezoelectric element 5c, and the adhesive strength with the piezoelectric element 5c can be increased. Further, the bead 12 that has entered the recess 51 can easily control the film thickness 94 at the position where the surface of the bonding portion 82 of the vibration plate 8b on the piezoelectric element 5c side is in contact.

(Embodiment 4)
Further, a fourth embodiment of the present disclosure will be described below with reference to FIG. FIG. 5 shows an inkjet head 100d according to Embodiment 4 of the present disclosure.

<Inkjet head 100d>
5 is an enlarged view of the region b2 in FIG. 3 (that is, FIG. 3B) and a cross-sectional view showing the same portion as FIG. In FIG. 5, the beads 11 shown in FIG. 3(b) do not have a structure having a single particle size, but have a particle size distribution, or a plurality of beads 11 having a single particle size are mixed. It shows a portion where the vibrating plate 8b and the piezoelectric element 5 are joined in the case where a thing or the like is used.

That is, the beads used in the present embodiment include at least the first beads 13 and the second beads 14 having different particle sizes. This point is different from the other embodiments described above.

The adhesive material obtained by kneading the first beads 13 having the largest particle diameter among the beads having a plurality of particle diameters and the second beads 14 having the smaller particle diameter than the first beads 13 is shown in FIG. Similarly to the above, in the configuration including the piezoelectric element 5 or the joint portion 82, it is applied to either of the joint portions 82. After that, the piezoelectric element 5 and the diaphragm 8b are aligned and further pressed, and then the adhesive material is cured by a curing method suitable for each adhesive material used, and the piezoelectric element 5 and the diaphragm 8b are bonded together. To join.

Note that the diaphragm 8b in FIG. 5 is illustrated in the case where there is the joint 82 as in FIG. 3B, but the present embodiment does not have the joint 82, and the piezoelectric element 5c and the diaphragm are not formed. The structure may be joined.

<Effect>
By appropriately adjusting the concentration of the first beads 13 and the second beads 14 (the concentration of the number of beads), when the piezoelectric element 5 and the vibrating plate 8b are pressed together, the vibrating plate 8b side of the first bead 13 is pressed. The top of the bite digs into the diaphragm 8b, which is softer than the first beads 13, and forms a recess 90b on the surface of the diaphragm 8b. On the other hand, the second beads 14 contact the diaphragm 8b at the top of the diaphragm 8b side, but do not bite.

That is, the relationship of the film thickness 95 of the first beads 13, the second beads 14, and the adhesive layer 9 d is larger than that of the first beads 13 which is larger than that of the second beads 14. The film thickness 95 is small. In the present embodiment, it becomes possible to form the adhesive layer 9d having such a configuration.

The film thickness 95 of the adhesive layer 9d at this time is smaller than the particle size of the first beads 13. The film thickness 95 substantially matches the particle size of the second beads 14. That is, the first beads 13 bite into the vibrating plate 8b, and the second beads 14 are sandwiched between the surface of the piezoelectric element 5 and the surface of the joint portion 82 where the recess 90b is not formed.

As in the above-described embodiment, the thickness 94 of the adhesive layer 9c is defined by the distance between the opposing surfaces of the piezoelectric element 5 and the diaphragm 8b without considering the recess 90b in which the beads 11 bite. To be done.

The presence of the second beads 14 makes it easier to control the film thickness 95 than in the case of a single particle size. More specifically, the film thickness 95 is gradually set small by applying a pressing force for joining the piezoelectric element 5 and the vibration plate 8b. However, the film thickness 95 is set at the position of the particle size of the second beads 14. , The stress with respect to the applied pressure changes. That is, the fact that the film thickness 95 has reached the particle size of the second beads 14 can be easily confirmed by torque management or the like, and the film thickness 95 can be easily controlled.

The controllability of the film thickness 95 is such that the adhesive material is crushed too much by the pressure that joins the piezoelectric element 5 and the vibration plate 8b, so that the adhesive material spreads wider than the width of the piezoelectric element 5 and is cured. Can be suppressed. Therefore, it is possible to suppress the problem that the adhesive material that sticks out and hardens inhibits the vibration of the diaphragm 8b. The second beads 14 may further include beads having a plurality of particle sizes. That is, the film thickness 95 can be determined depending on the largest particle size of the second beads 14, and it is sufficient that the second beads 14 have a predetermined particle size or less to be used as the film thickness 95. In other words, compared to the first beads 13, the particle size of the second beads 14 is easy to manage, and thus inexpensive beads (coarse particle size management) can be used.

Further, when the second beads 14 having a plurality of particle sizes as described above are used, which particle size of the second beads 14 is to be set, the film thickness 95 is set in multiple stages depending on the applied pressure. It can also be controlled.

As described above, the beads 11 included in the inkjet head 100d according to the present embodiment include the first beads 13 and the second beads 14 having different particle sizes, and the first beads are larger than the particle size of the second beads 14. The film thickness 95 is smaller than the particle size of 13.

Accordingly, since the film thickness 95 can be easily controlled without having the recessed portion 51 in the piezoelectric element 5, the inkjet head having desired ejection characteristics while ensuring the bonding reliability between the piezoelectric element 5 and the diaphragm 8b. Can be easily realized.

(Other embodiments)
Although the embodiments have been described above, the present disclosure is not limited to the above embodiments.

Further, although the constituent elements of the inkjet head have been illustrated in the above-described embodiments, each function of the constituent elements of the inkjet head may be distributed to a plurality of parts of the inkjet head.

In addition, it is realized by making various modifications to those embodiments by those skilled in the art, or by arbitrarily combining the components and functions of the embodiments without departing from the spirit of the present disclosure. The present disclosure also includes the forms.

For example, in the present disclosure, an example in which the vibrating plates 8 and 8b are made of resin is shown, but the vibrating plate may be made of any material having a hardness lower than that of the beads 11 and 13. Good.

Further, for example, the diaphragm 8b is composed of 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) that can be ignored with respect to the thickness of the diaphragm, such a joint portion 82 may not be provided. Alternatively, a piezoelectric element having a displacement characteristic capable of vibrating a diaphragm having a sufficient thickness such that the deformation 83 can be ignored may be provided.

Further, a highly reliable inkjet head may be realized by arbitrarily combining a plurality of modes among the first to fourth embodiments.

Since the present disclosure provides a highly reliable inkjet head, it is useful because a pattern of an electronic device or an optical device can be formed at low cost.

DESCRIPTION OF SYMBOLS 1 Nozzle plate 2 Nozzle 3 Pressure generating chamber 4 Flow path forming substrates 5, 5a, 5c Piezoelectric element 6 Driving section 7 Column sections 8, 8a, 8b Vibration plate 9, 9a, 9b, 9c, 9d Adhesive material layer 10 Base 11 , 12, 13, 14 beads 51 recessed portion 81 vibrating portion 82, 82a joint portion 83 deformation 90, 90b recessed portion 91, 92, 94, 95 film thickness 93 protruding portion 100, 100a, 100b, 100c, 100d inkjet head

Claims (5)

An inkjet head,
A piezoelectric element,
A diaphragm,
An adhesive layer disposed between the piezoelectric element and the vibration plate, for bonding the piezoelectric element and the vibration plate,
An inkjet head in which the adhesive layer contains beads having a hardness higher than that of the diaphragm, and the film thickness of the adhesive layer is smaller than the particle diameter of the beads. The inkjet head according to claim 1, wherein the diaphragm is made of resin. The diaphragm is
Vibrating part,
A joint portion that is thicker in a convex shape on the piezoelectric element side than the vibrating portion,
The ink jet head according to claim 1, wherein the bonding portion and the piezoelectric element are bonded by the adhesive layer. The piezoelectric element has a recessed portion on a joint surface facing the diaphragm,
The inkjet head according to claim 1, wherein at least a part of the beads is arranged in the recess. The beads include first beads and second beads having different particle sizes,
The inkjet head according to claim 1, wherein the film thickness is smaller than the particle diameter of the first beads that is larger than the particle diameter of the second beads.

Images