JPH03190742A - Ink jet head - Google Patents

Abstract

PURPOSE:To suppress the generation of bending in a piezoelectric converter by making the coefficient of thermal expansion of base part approximate to that of the piezoelectric converter. CONSTITUTION:An invar rolled plate or Mo extremely approximate to piezoelectric ceramic in a coefficient of thermal expansion is used as the elastic plate 5 and base part 1 of a piezoelectric converter. By this constitution, the generation of internal stress and bending in the bonded part of the piezoelectric converter and the base part is prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to inkjet print recording,
In particular, the present invention relates to an inkjet recording apparatus that drives a piezoelectric transducer in ink to eject ink from a nozzle opening to form an ink image on a medium such as recording paper.

More specifically, it relates to an inkjet head.

[Prior Art] An inkjet head formed by laminating a nozzle forming substrate having a plurality of nozzle openings and a piezoelectric transducer arranged at a certain interval behind the nozzle forming substrate and directly contacting ink to apply pressure. is disclosed in Japanese Patent Publication No. Sho 60-8953'. An inkjet head with this structure generates pressure by displacing the piezoelectric transducer, which has a cantilevered or double-sided beam structure, in a direction approximately perpendicular to the nozzle forming substrate, and generates pressure between the piezoelectric transducer and the nozzle forming substrate. It is designed to eject a certain type of ink.

[Problems to be Solved by the Invention] However, since the inkjet head using the piezoelectric transducer of the prior art has a laminated structure, internal strain occurs in each part due to temperature changes during manufacturing and use, and deflection due to bimetallic action occurs. occurs. This makes it difficult to ensure dimensional accuracy, and various ink ejection characteristics are unstable. In particular, the gap size between the piezoelectric transducer and the nozzle forming substrate has the greatest effect on various ink ejection characteristics, but since conventional inkjet heads are configured with multiple piezoelectric transducers lined up, This method has a problem in that it is not possible to ensure a very small gap between the piezoelectric transducer and the nozzle forming substrate with high precision.

Therefore, the present invention is intended to solve these problems, and its key objective is to ensure the gap between the piezoelectric transducer and the nozzle forming substrate with high precision and to stabilize various ink ejection characteristics. .

[Means for Solving the Problems] An inkjet head according to the present invention includes a nozzle forming substrate having a plurality of nozzle openings, and one or more nozzle openings.
In an on-demand inkjet head formed by laminating a piezoelectric transducer made of a piezoelectric element and an elastic body arranged in a pair, and a base part to which the piezoelectric transducer is joined, the coefficient of thermal expansion of the base part is the same as that of the piezoelectric element. Converter heat HF/
It is characterized by its approximation to the tensile coefficient.

[Function] According to the above structure of the present invention, since the piezoelectric transducer is stacked on the base portion having a thermal expansion coefficient close to that of the piezoelectric transducer, distortion and distortion due to temperature changes during manufacturing and use are avoided. Deflection is reduced, and minute gaps between the plurality of piezoelectric transducers and the nozzle forming substrate are ensured uniformly and with high precision.

[Embodiment] An embodiment of the present invention will be described based on the drawings using an example of an inkjet head used in an inkjet printer, in which a vibrator has a cantilever structure.

FIGS. 1A and 1B are a perspective view and a front view mainly showing the configuration of the base portion, piezoelectric transducer, and nozzle forming substrate of the inkjet head. Reference numeral 1 denotes a base portion, which is made of a highly rigid member such as metal or ceramics in order to prevent deformation of the drive portion. The upper part of the base part 1 has a °
, an electrode 2 is provided that forms conductivity with a plurality of piezoelectric transducers. 7 is a piezoelectric transducer, which includes a plurality of piezoelectric elements 3 arranged in parallel to each other, electrodes 4 formed on both sides thereof, and an elastic plate 5 of a metal layer arranged on the nozzle opening 6 side of the piezoelectric element 3. It is made up of. A spacer 9 is used to establish electrical conductivity between the piezoelectric transducer 7 and the nozzle forming substrate 8, and to maintain a constant gap between them.

The nozzle forming substrate 8 has a plurality of nozzles 6 facing a plurality of piezoelectric transducers 7. Further, due to the conductivity provided by the spacer 9, it plays a role as a common electrode for the electrodes on the elastic plate 5 side. The driving section is constructed by laminating the above-mentioned members as shown in the drawing.

Then, F transmits an electric signal to the plural piezoelectric transducers 7
The head is configured by connecting the PCIO.

The piezoelectric transducer 7 is composed of a vibrator 11, which is a freely displaceable vibrating part, and a fixed part 12. When a voltage is applied and discharged between the double-sided electrodes 4 of the piezoelectric element 3, the piezoelectric element 3 contracts and expands due to the piezoelectric effect, and this longitudinal vibration causes the elastic plate 5 to move the free end of the vibrator 11 toward the nozzle opening 6. and is displaced 13 in an approximately right angle direction. This displacement increases the pressure of the ink near the nozzle opening 6, and ink droplets are ejected from the nozzle 6. Therefore, by selectively applying and discharging a voltage, the free end of the vibrator 11 is deformed and displaced, and the ink in the vicinity is ejected from the nozzle 6 to perform printing. In order to prevent the piezoelectric element 3 from being damaged due to the vibrator 11 coming into contact with the nozzle forming substrate 8 during driving, the elastic plate 5 is arranged on the nozzle substrate 8 side in FIG. 1, but it is arranged on the opposite side. Similar displacement can be obtained even if

The electrode 2 is patterned on the base portion 1 in parallel with a plurality of piezoelectric transducers 7, and an FPCIO is connected to this to transmit an electric signal to the piezoelectric transducer 7. Electrode 2
The conductivity between the electrode 4 of the piezoelectric transducer and the electrode 4 of the piezoelectric transducer can be obtained by using a thermosetting adhesive containing metal particles or fine resin particles whose surfaces are treated with metal, or by brazing.

A thin metal plate is used as a spacer 9 that ensures conductivity between the nozzle forming substrate 8 and the piezoelectric transducer 7 and forms a gap between them. Alternatively, as described above, by limiting the particle size of metal particles or metal-treated fine resin particles, it is possible to create the necessary gap size and provide conductivity.

Next, the manufacturing process of this example will be explained using FIG. 2. First, in order to form an independent electrode pattern 2 on the base portion 1, a thin film 14 is made of polyimide, and an electrode of Ag or Cu is formed on the thin film 14 by etching. Next, a piezoelectric transducer 7, to which a piezoelectric ceramic 3 and an elastic plate 5 have been previously bonded, is bonded to the top of the piezoelectric transducer 7 using polyimide in which Ni-plated fine particles of particle size are dispersed and mixed. Similarly, the nozzle forming substrate 8 is bonded using polyimide in which Ni-plated fine particles of resin having a particle size necessary for the gap between the piezoelectric transducer 7 and the nozzle forming substrate 8 are dispersed.

In the laminated structure described above, since the adhesive is thermosetting, there is a temperature difference between the time of manufacture and use, and there is a difference in the thermal expansion coefficient between each component, which causes deflection. Occur. In particular, the two members of the piezoelectric transducer 7 are closely joined, and the base part 1 is also closely joined to stabilize the vibration characteristics, so the difference in thermal expansion coefficient between each member may be small. The structure is susceptible to deflection.

Therefore, in this embodiment, the elastic plate 5 and the base part 1 of the piezoelectric transducer are made of piezoelectric ceramic with a coefficient of thermal expansion (α=4.5).
X10-6) is an invar rolled plate (α=2
．． 8xlo-6) or Mo (α=4.9X10-
6) was used to prevent the occurrence of internal strain and deflection between the piezoelectric transducer and the base joint.

By approximating the coefficient of thermal expansion in this way, the effect of preventing deflection was obtained, but the effect is also due to the joining method in which the joining part is made elastic by joining with polyimide.

In this way, by approximating the thermal expansion coefficients of the piezoelectric transducer 7 and the base part 1, it is possible to prevent internal distortion due to the temperature difference between manufacturing and use and deflection of the piezoelectric transducer due to the bimetal effect. The gap size between the container 7 and the nozzle forming substrate 8 was ensured with high precision. Furthermore, since the internal strain could be suppressed to a minimum, it was possible to prevent the destruction of the piezoelectric element 3, which had been a concern about its strength, and improve reliability.

[Effects of the Invention] As explained above, according to the present invention, since the thermal expansion coefficients of the piezoelectric transducer and the base portion are approximated, it is possible to suppress the occurrence of deflection of the piezoelectric transducer, and moreover, the environmental temperature during use can be suppressed. Internal strain changes can be minimized during changes. Therefore, the gap between the piezoelectric transducer and the nozzle forming substrate can be managed and ensured with high precision, and a highly reliable inkjet head with excellent print quality and excellent characteristics such as ink droplet ejection speed, ejection mode, and ejection amount can be created. The effect is that it can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1(a) and 1(b) are a partial perspective view and a front view of a driving section in an embodiment of an inkjet head according to the present invention. FIG. 2 is an explanatory diagram showing a method of manufacturing the same drive section. 1...Base portion 3...Piezoelectric element 5...Elastic plate 6...Nozzle 7...Piezoelectric transducer 8...Nozzle forming substrate 10 . . . FPC or more

Claims (1)

[Claims] A nozzle forming substrate having a plurality of nozzle openings, a piezoelectric transducer made of a piezoelectric element and an elastic body arranged one-to-one with the nozzle openings, and a base portion to which the piezoelectric transducer is bonded are laminated. An on-demand inkjet head characterized in that the base portion has a coefficient of thermal expansion that is close to a coefficient of thermal expansion of the piezoelectric transducer.