JPH05220956A - Ink jet reocrding head - Google Patents

Abstract

PURPOSE:To obtain an ink jet head having small fluctuation and stable delivery characteristics and reliability. CONSTITUTION:After an integral laminated piezoelectric element is bonded to a support substrate 2, this is cut into a plurality of piezoelectric elements 1. Then, a piezoelectric element device is formed with an end face flatness. Furthermore, the piezoelectric element device and a fixing plate 3 for fixing this device are cured at the order of an ordinary temperature for the good flatness of the top ends of the fixing plate 3 and the piezoelectric element 1. In the bonding to a pressure wall 5a, said top ends can be bonded without applying an excess stress to the pressure wall 5a. In addition, by using a temporarily bonding means at the time of bonding, an assembling jig holding time is shortened for a higher mass productivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure and manufacture of an ink jet recording head for recording by ejecting droplets.

[0002]

2. Description of the Related Art An ink jet recording head which utilizes displacement in a longitudinal direction of a piezoelectric element to displace a pressure wall in the displacement direction to pressurize ink in a pressure chamber and eject ink droplets from a nozzle communicating with the pressure chamber. , Japanese Patent Publication No. 2-52625. FIG. 7 is a diagram showing the outline of the structure. As shown in FIG. 7, the pressure wall 1 is attached to the flow path substrate 103 to which the nozzle plate 102 having the ink ejection port 101 is joined.
The pressure plates forming 04 are joined, and the viscoelastic member 107 connects the leg portion 106 arranged at the tip of the piezoelectric element 105 in the longitudinal direction to the portion located in each pressure chamber. Figure 8
7 is a partially enlarged cross-sectional view of a leg portion 106 and a viscoelastic member 107. FIG. The piezoelectric elements 105 are positioned and joined one by one by a fixing plate 108, and electrical wiring is made by a circuit board 109 thereon.

However, in the above-mentioned structure, firstly, since the piezoelectric elements 105 are fixed one by one, there is a problem that it takes a lot of time to join them. Secondly, the pressure applied to the pressure wall 104 also varies due to the variation in the joining pressure at the time of joining, and thus the stress and the amount of deflection applied to the pressure wall 104 also vary, which affects the ejection characteristics of the head. become. Thirdly, the piezoelectric element 105
Since the leg portion 106 is provided between the pressure wall 104 and the pressure wall 104, the leg portion 1
Since it takes time and effort to bond the piezoelectric element 105 with the piezoelectric element 105 and the volume of the leg portion 106 does not interfere with the adjacent leg portion 106, the arrangement interval of the piezoelectric elements 105 cannot be made very small and the head size is limited. There is a problem that occurs. Fourth
In order to reduce the size of the head, for example, when the nozzle array is made small and the displacement of the piezoelectric element 105 is made large, the stress generated in the pressure wall 104 becomes large. Further, if extra stress is applied to the piezoelectric element 105 by assembling pressure on the pressure wall 104, the pressure wall 1
There is a problem that the stress limit of 04 may be exceeded.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to make the coupling between the pressure wall and the piezoelectric element easy and mass-producible, and to realize high density. An object of the present invention is to provide an inkjet head that is stable in nozzle arrangement, has a small variation, and has stable ejection characteristics and reliability.

[0005]

In view of the above, according to the present invention, an integral piezoelectric element is bonded to a holding substrate made of ceramic or the like and then cut to form a flat piezoelectric element while maintaining the initial flatness of the piezoelectric element.
The piezoelectric element unit is attached to the fixing plate so that each piezoelectric element has a vibrator shape, so that the piezoelectric elements do not have to be joined one by one. Further, the leg portion is not provided, and the protrusion is formed integrally with the pressure wall and has a shape smaller than that of the piezoelectric element.

In terms of manufacturing, the fixing plate and the piezoelectric element unit are bonded with an adhesive that can be cured at room temperature to suppress the difference in thermal expansion due to the difference in material, and to maintain the flatness of the fixing plate and the upper end surface of the piezoelectric element. , Make sure that extra child pressure is not applied when joining the pressure wall. In addition, when a room temperature curing adhesive is used for bonding, a quick-curing temporary fixing adhesive is also used to shorten the holding time of the jig during manufacturing and improve mass productivity.

[0007]

FIG. 2 is a sectional view showing a schematic structure of an ink jet recording head for explaining an embodiment of the present invention. 3 is a sectional view taken along the line AA ′ of FIG. 2, and FIG. 4 is a sectional view of FIG. 2B.
It is a -B 'sectional view. The configuration will be described below with reference to FIGS.

Reference numeral 1 is a comb-shaped laminated piezoelectric element, and 2 is a holding substrate for holding the piezoelectric element 1. On the holding substrate 2, a signal electrode pattern 2a for driving each piezoelectric element 1 is provided for each piezoelectric element. Conducted to 1. This is to bond an integral laminated piezoelectric element to a substrate material provided with an electrode pattern to be a holding substrate 2 such as a ceramic or glass epoxy substrate with an adhesive or the like,
It is manufactured by cutting a groove with a predetermined width w to a certain depth of the substrate material by dicing or the like.

A common electrode 11 for supplying a driving voltage is provided on the other surface of the piezoelectric element 1. The integrated piezoelectric element 1 and holding substrate 2 are fixed to a fixing plate 3 made of a material such as metal, resin, or ceramic. The ink flow path unit 12 is joined to the tip end side of the piezoelectric element 1 via the joining member 4. The ink unit 12 includes a nozzle plate 7 having a nozzle portion 10, a pressure chamber 8, a communication hole 9 communicating from the pressure chamber 8 to the nozzle 10, an ink supply reservoir 13, a meat portion 6 for forming the portion, and a pressure chamber 8. It is composed of pressure walls 5a and 5b for applying pressure.
The pressure wall 5a is joined to the piezoelectric element 1 by the joining member 4a at the portion receiving the generated force of the piezoelectric element 1, and the portion of the pressure wall 5a is formed in a projection shape thicker than the pressure wall 5b of the surrounding shell portion. The portion of the pressure wall 5b can be bent in the shape of a beam when the piezoelectric element 1 is displaced. The pressure walls 5 a and 5 b are included in the pressure plate 5, and the pressure plate 5 is joined to the fixing plate 3 by the joining member 4. The pressure plate 5 may be manufactured by metal electroforming, metal etching,
It can be manufactured by a combination of a plastic film or metal foil and a photosensitive resin.

FIGS. 5 and 6 show an outline of the integrated structure of the piezoelectric element 1 and the holding substrate 2 and the fixing plate 3. The pressure wall 5b is bent by the displacement of the piezoelectric element 1 and bending stress is applied. As a result, fatigue fracture easily occurs, and it is not allowed to give a flexure during assembly. Therefore, the flatness of the tip 1a of the piezoelectric element 1 and the upper surface 3a of the fixed plate 3 and the flatness of the pressure plate 5 on the ink flow path side are required at the time of assembly.

FIG. 1 is a schematic diagram showing the structure of the present invention.
The joint between the fixed plate 3 and the piezoelectric element 1 and the holding substrate 2 must be surely joined in the gap 21 between the holding substrate 2 and the fixed plate 3 in order to suppress the vibration of the holding substrate 2 due to the displacement of the piezoelectric element 1. Further, in the structure of the present embodiment, the dummy piezoelectric element portion 14 (which does not have a function for ejecting ink and is provided as a part of the structure) shown in FIG. 3 is provided,
It is also effective to bond the dummy piezoelectric element 14 and the fixing plate 3 at the gap 22. For these joining, the joining by the adhesive is sure, and the adhesive can be penetrated into the gaps 21 and 22 by just placing the adhesive of appropriate viscosity on the portions A and B in FIG. 22 is set to an appropriate size. On the contrary, if the adhesive should not be applied, it is possible to prevent the adhesive from penetrating by widening the gaps 21 and 22 or more in advance. In this embodiment, the fixing plate 3
The material used was an epoxy resin, the holding substrate 2 was made of free-cutting ceramics, and the adhesive was a 500 mPas epoxy one-component epoxy adhesive. By the way, the curing time of the above-mentioned epoxy adhesive is 24 to 48 hours at room temperature and 30 minutes to 1 hour at 100 ° C. A bonding jig is used when the fixing plate 3, the piezoelectric element 1 and the holding substrate 2 are bonded, but from the viewpoint of mass productivity, it is desired to shorten the holding time of the jig as much as possible. Therefore, although it is desired to heat-cure at 100 ° C., in the case of heat-curing, the materials and shapes of the piezoelectric element 1, the holding substrate 2 and the fixing plate 3 are different,
There is a problem that the flatness between the tip 1a of the piezoelectric element 1 and the upper surface 3a of the fixed plate 3 is impaired due to the difference in thermal expansion. Therefore, in order to cure at room temperature and shorten the holding time of the jig, a temporary fixing adhesive was used together. 23 shown in FIG.
The part of is a temporary fixing adhesive. In this example, after injecting the above-mentioned epoxy one-component adhesive, an acrylic UV adhesive as a temporary fixing adhesive was placed on the portion 23 and UV irradiation was performed for 30 seconds. Immediately after that, the jig is released, the flatness of the tip 1a of the piezoelectric element 1 and the upper surface 3a of the fixing plate 3 is measured, and the change in the flatness is checked until the epoxy one-component adhesive which is the main adhesive is cured. However, the change is 1μ including the measurement error.
It was within m. Although the epoxy one-component adhesive is used in this embodiment, the same effect can be obtained by using the UV anaerobic adhesive.

[0012]

As described above, in the ink jet recording head according to the present invention, the holding substrate for holding the laminated piezoelectric element and the fixing plate for fixing the holding substrate are bonded with an adhesive, so that the holding substrate The entire surface necessary for fixing can be securely joined, and the adhesive is cured at room temperature to improve the flatness between the upper surface of the piezoelectric element and the upper surface of the fixing plate, and prevent the occurrence of extra stress on the pressure wall and stabilize it. A head having ejection characteristics can be supplied. Also, by using a temporary adhesive such as a UV adhesive, the holding time of the jig can be shortened even with this adhesive, which has a long room temperature curing time, so it is possible to mass-produce with a small number of jigs and reduce manufacturing costs. Also leads to Further, since the piezoelectric element is processed after joining the holding substrate, the flatness of the end surface of the piezoelectric element is improved and the number of steps for assembling the piezoelectric element to the fixing plate is reduced. Further, by directly bonding the piezoelectric element and the pressure wall with a bonding material, it is possible to cope with high density of the head. As described above, according to the present invention, it is possible to provide a piezoelectric element structure capable of bonding a pressure wall and a piezoelectric element, which is stable, has a small variation, and is highly reliable even for a head having a densified shape. it can. This naturally provides a stable inkjet characteristic and a reliable inkjet head.

[Brief description of drawings]

FIG. 1 is a diagram showing a driving portion of an inkjet recording head of the present invention.

FIG. 2 is a sectional view showing the overall configuration of a head according to an embodiment of the present invention.

FIG. 3 is a sectional view taken along the line A-A ′ in FIG.

FIG. 4 is a sectional view taken along the line B-B ′ in FIG.

FIG. 5 is a diagram illustrating the assembly of a fixed plate and a piezoelectric element.

FIG. 6 is a diagram illustrating the assembly of a fixed plate and a piezoelectric element.

FIG. 7 is a diagram illustrating a structure of a conventional inkjet head.

FIG. 8 is a partial cross-sectional view illustrating the structure of a conventional inkjet head.

[Explanation of symbols]

1 ......... Multilayer piezoelectric element 1a .................. Upper end surface of multilayer piezoelectric element 2 ........ Retaining substrate 2a ........ Signal electrode pattern 3 ・・ ・ ・ ・ ・ ・ Fixing plate 3 ・ ・ ・ ・ ・ ・ ・ ・ ・ Upper surface of fixing plate 4 ・ ・ ・ ・ ・ ・ ・ Joining member between fixing plate and pressure plate 4a ・ ・ ・ ・ ・ ・ ・ Pressure chamber and pressure wall Joining member 5 ···· Pressure plate 5a, 5b ···· Pressure wall 6 ···· Flow path wall 7 ··· Nozzle plate 8 · ··· Pressure chamber 9 ··· Communication hole 10 ···· Nozzle 11 ···· Common electrode pattern 12 ···· Ink flow channel unit 13 ···· Ink supply reservoir 14 ··· Dummy piezoelectric element 21 ···· Gap between holding substrate and fixed plate 2 ....... gap between the dummy piezoelectric element and the fixing plate 23 ....... temporary fixing adhesive portion

Claims (5)

[Claims] 1. A displacement of a piezoelectric element is used to displace a pressure wall of a pressure chamber arranged in the displacement direction to pressurize ink in the pressure chamber, and an ink droplet is ejected by a nozzle communicating with the pressure chamber. In an inkjet recording head for ejecting, a piezoelectric element unit including the piezoelectric element and a holding substrate holding the piezoelectric element, and an ink flow path substrate including the piezoelectric element and the holding substrate and including one or more pressure chambers. An ink jet recording head, comprising: a fixing plate bonded to the piezoelectric element unit and the fixing plate bonded with an adhesive. 2. The ink jet recording head according to claim 1, wherein an adhesive agent for joining the piezoelectric element unit and the fixing plate is cured in a range of 10 ° C. to 40 ° C. 3. The ink jet recording head according to claim 1, wherein this adhesive and a temporary fixing adhesive for temporary fixing are used together as an adhesive for joining the piezoelectric element unit and the fixing plate. .. 4. The piezoelectric element unit is processed so that each vibrator is formed one by one after the holding substrate and the piezoelectric ceramic are bonded and each vibrator is integrally held. The inkjet recording head according to claim 1. 5. The pressure wall is composed of a receiving portion that receives the displacement of the piezoelectric element and a shell portion that is deflected by the displacement, and the receiving portion has a projecting shape that is formed thicker than the shell portion, and the receiving portion. The ink jet recording head according to claim 1, wherein the ink jet recording head and the piezoelectric element tip end portion are directly joined by a joining material.