JPH0431053A - Ink jet head and manufacture thereof - Google Patents

Abstract

PURPOSE:To realize a simultaneous space regulation and conduction between a nozzle forming member and a piezoelectric transducer by a method wherein the aforesaid member and transducer are joined together by a joint member obtained by mixing a conduction space regulating member having a specific coefficient of thermal expansion and an adhesive agent having a specific coefficient of thermal expansion. CONSTITUTION:A plurality of piezoelectric transducers 21 arranged parallel to one another and the nozzle forming member 22 corresponding thereto are joined together by a joint member 41. The joint member 41 is made up by mixing a conduction space regulating member 40 having a coefficient alphas of thermal expansion and an adhesive agent 24 having a coefficient alphaa of thermal expansion. At this time, the conduction space regulating member 40 and the adhesive agent 24 are selected to satisfy alphas<alphaa. The piezoelectric transducer 21 and the nozzle forming member 22 are bonded together, pressed under heat and cooled to contract the joint member 41. Since the adhesive agent 24 is greater than the conduction space regulating member 40 in the amount of the contraction taking place during this time, the conduction space regulating member 40 is subjected to a pressing force. The conduction space regulating member 40 adhere to the nozzle forming member 22 and the piezoelectric transducer 21 while regulating spaces uniformly therebetween and, therefore, an accurate conduction is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inkjet head used in printers and the like that ejects ink droplets to form an ink image on a recording medium such as recording paper, and a method for manufacturing the same.

[Conventional technology]

FIG. 5 shows an example of the structure of a conventional inkjet head disclosed in Japanese Patent Publication No. 8953/1983. The above structure includes a nozzle forming member 102 having a plurality of nozzles 103.
and a piezoelectric transducer 101 placed behind it and in direct contact with the recording ink 109. The piezoelectric transducer includes a rod-shaped metal member 105 and a rod-shaped piezoelectric ceramic member 104.
It is attached to the nozzle forming member 102 with a screw 108 via a spacer 107. This structural example has an impact bar piece 106 made of metal to improve the impact characteristics of the piezoelectric transducer. Piezoelectric transducer 1
01 vibrates as if displaced in a direction generally orthogonal to the nozzle forming member 102.

In conventional inkjet head manufacturing methods, the nozzle forming member and the piezoelectric transducer are fixed via a spacer 107 made of a thin metal plate in order to define the distance between them. The fixing methods shown in Figure 5 include fastening with screws, beam welding or ultrasonic welding, metal soldering such as soldering, and conductive adhesive mixed with metal powder. there were. In these methods, the electrode of the piezoelectric transducer 101 on the nozzle forming member 102 side is used as a common electrode, and the piezoelectric transducer 101 is mechanically fixed to the nozzle forming member 102 and electrically connected.

[Problem to be solved by the invention]

However, when the mounting is done with screws and the tightening is fixed, uneven tightening force is unavoidable, making stable fixation difficult. If they are joined by welding, the impact energy during welding may cause deformation of the spacing regulating member, piezoelectric transducer, and nozzle forming member, and in severe cases, may cause destruction. In particular, the piezoelectric bodies constituting piezoelectric transducers are usually very thin and brittle, so it has been difficult to join them together without destroying them.

When bonding with an adhesive or a metal solder, it is difficult to control the thickness of the bonding layer, so it is also difficult to control the gap between the beam portion of the piezoelectric transducer that projects like a beam and the nozzle forming member. That is,
The gap between the nozzle forming member and the movable part of the piezoelectric transducer facing it affects the ink ejection characteristics, so it is necessary to control the minute gap with high precision. The problem was that accuracy could not be obtained.

In metal soldering, the piezoelectric transducer may be destroyed and leakage current may occur due to flux. In order to electrically connect the nozzle forming member and the piezoelectric transducer, metal brazing is required, which complicates the manufacturing process.

When bonding was performed using a conductive adhesive containing dispersed metal powder, the reliability was not fully satisfactory, as sufficient bonding strength could not be obtained and circuit ovens occurred.

Therefore, an object of the present invention is to solve these problems and to propose an inkjet head with stable characteristics and a method for manufacturing the same.

[Means to solve the problem]

In order to solve the problem, the present invention provides that a conductive spacing regulating member having a coefficient of thermal expansion α■ and an adhesive having a coefficient of thermal expansion α■ are α■< α■, and the conductive spacing regulating member The present invention is characterized in that at least the nozzle forming member and the piezoelectric transducer are bonded using a bonding material in which the adhesive is dispersed and mixed.

〔Example〕

The details of the present invention will be explained below based on examples, but the present invention is not limited thereto.

FIG. 1 is a perspective view of a printer using an inkjet head according to the present invention. In the figure, a recording medium 1 is wound around a platen 4 and is pressed by a feed roller 2.about.3. Guided by the guide shaft 6.7 and parallel to the platen axis 10
An inkjet head 9 is mounted on a carriage 8 that can be moved to
It is composed of the following. The inkjet head 9 has a plurality of nozzle openings that can be independently controlled to eject ink droplets by applying an external driving voltage. The inkjet head 9 is scanned in the platen axis direction 10, selectively ejects ink droplets from nozzle openings, and forms an ink image on the recording medium 1.

The recording medium 1 is placed on a platen 4. By rotation of the feed rollers 2 and 3, the recording medium 1 is conveyed in a sub-scanning direction 5 perpendicular to the scanning direction, and printing is performed on the recording medium 1.

FIG. 2 is a sectional view showing an embodiment of an inkjet head according to the present invention. FIG. 3 is a sectional perspective view of the main part. FIG. 4 is also a sectional view of the main part. However, the present invention is not limited thereto. A piezoelectric transducer 21 and a nozzle forming member 22 are laminated and fixed to the frame 20 with a base material 25 interposed therebetween. Nozzle forming member 2
2 is composed of a thin metal plate having a plurality of nozzles 23. Ink 2 is located near the piezoelectric transducer 21 and nozzle 23.
Filled with 8.

The piezoelectric transducer 21 includes a piezoelectric body 32 such as a piezoelectric ceramic,
It has a laminated structure consisting of an electrode layer 33 made of a thin metal film such as gold provided on the top surface of a piezoelectric body 32, and a metal layer 31 provided on the opposite surface of the electrode layer 33. In this embodiment, the piezoelectric body 32 is made of lead zirconate titanate (PbTiO3-
PbZrO3-based solid solution) thin plates are used, but barium titanate (BaTi03), lithium niobate (LiNb03), and lithium tantalate (LiTa0) are also used.
3) etc. may be used.

The electrode layer 33 is formed using methods such as vapor deposition, sputtering, and plating. The configuration of this embodiment is as follows: 0.1 μm of chromium, 0.1 μm of nickel, and 0.0 μm of gold on the piezoelectric material 32.
．． They were formed by vapor deposition in order of 1 μm. In addition, the metal layer 31
The purpose of using an alloy of iron and nickel (Fe--Ni alloy) is to improve fluctuations caused by temperature changes in the beam portion of the piezoelectric transducer 21. By determining the alloy composition ratio of Fe and Ni so as to match the coefficient of thermal expansion of the piezoelectric body 32, fluctuations due to the bimetal effect can be reduced.

A plurality of piezoelectric transducers 21 arranged in parallel and a nozzle forming member 22 facing the piezoelectric transducers 21 are bonded using a bonding material 41 . The bonding material 41 connects the conductive spacing regulating member 40 with a coefficient of thermal expansion of α■ to an adhesive 24 with a coefficient of thermal expansion of α■.
It is mixed inside.

At this time, the conductive spacing regulating member 40 and adhesive 24 are selected so that α5<α■. The conductive spacing regulating member 40 is one whose particle surface is treated with a metal film such as nickel or gold, or the particle itself is electrically conductive.

An electrode pattern 35 is formed on the surface of the base material 25 so as to correspond to the piezoelectric transducer 21 .

In this example, an electrode pattern 35 was formed by etching after depositing an electrode film on the surface of a base material 25 made of ceramic. In addition, a conductive member such as a metal plate may be subjected to insulation treatment and then electrodes may be formed thereon. A flexible substrate 27 (see FIG. 2) having a corresponding wiring pattern is connected to the base electrode 35.

Next, the manufacturing process of the inkjet head of this embodiment will be explained in the order of the steps of joining the nozzle forming member 22 and the piezoelectric transducer 21, but the invention is not limited thereto.

(a) The coefficient of thermal expansion is a, = 0. 8 x 10-5
/'C, the thermal expansion coefficient of the cured material is α■ = 5. The adhesive 24 having a temperature of 1 x 10-5/°C is mixed and stirred to be uniformly dispersed to obtain a bonding material 41. The amount of the conductive spacing regulating member 40 mixed is preferably 1 to 10% by weight of the bonding material 41. Further, the shape of the conductive spacing regulating member 40 is preferably spherical, cylindrical, or elongated, and most preferably spherical.

The material of the conductive spacing regulating member 40 is preferably glass or ceramic having high rigidity, but is not limited thereto. In this example (Fig. 3), the diameter is Q, 02 m.
1% by weight of the conductive spacing regulating member 40, which was made of nickel-plated glass fibers having a thermal expansion coefficient of α■=0.8×lO−5/°C, was mixed.

In addition, since the adhesive is cured by heating, the use of resin or resin fibers that soften when cured as the conductive spacing regulating member must be avoided since the intended constant spacing cannot be secured.

In this embodiment, a polyimide adhesive is used as the adhesive 24, but the adhesive is not limited to this, and synthetic resin adhesives such as epoxy, silicone, polyester, acrylic, etc., or ceramic-based inorganic adhesives may be used. A thermosetting adhesive such as adhesive can be used. Moreover, an adhesive that uses both heat curing and ultraviolet curing can also be used.

(b) Precisely apply the bonding material 41 in a predetermined shape to either the surface of the metal layer 31 of the piezoelectric transducer 21 and the surface to be bonded of the nozzle forming member 22, or either one of them. In this example, the coating was performed using a screen printing method, but a transfer printing method or the like may also be used.

(C) The piezoelectric transducer 21 and the nozzle forming member 22 are pasted together and heated and pressed at a predetermined temperature, time, and pressure to harden the bond. The maximum pressure at this time is limited by the destruction of the piezoelectric body 32 and the conductive spacing regulating member 40, the deformation of the nozzle forming member 22, and the like.

On the other hand, the minimum pressure is limited by whether electrical connection is possible between the nozzle forming member 22 and the metal layer 31 of the piezoelectric transducer 21 by the conductive spacing regulating member 40. Therefore, the pressure during bonding is preferably 5 to 70 kg/Cm2. In this example, 41 layers of bonding material were heat-pressed to a thickness of one conductive spacing regulating member 40 at a pressure of 20 kg/cT112.

(d) After heating, when the objects to be joined are cooled, the joining material 41
The adhesive 24 contracts, but the amount of contraction at this time is greater in the adhesive 24 than in the conductive spacing regulating member 40. For this reason, adhesive 24
Due to the difference in the amount of contraction of the conductive spacing regulating member 40, the spacing regulating member 40 receives a pressing force. Then, a conductive spacing regulating member 4 is provided between the nozzle forming member 22 and the piezoelectric transducer 21.
Conductive spacing regulating member 4 while regulating the spacing uniformly by 0
0 is in close contact with each other, ensuring continuity.

In this example, the thickness of the 41 layers of bonding material is 0.0195 mm.
The experimental results were that the variation was small, ±0.0005 mm, and the electrical resistance was 1 to 1.5 Ω/2. Furthermore, as for the fracture strength of the joint, when polyimide resin was used, a shear strength of 3 to 5 kg/mm2 was obtained. In addition, 50% of Ag particles and CU powder particles of about several μm are used.
It has the effect that higher bonding strength can be obtained than the general conductive adhesive mixed in above, and impact resistance is improved. Management of gaps and conductivity is important for the ejection characteristics of ink droplets.
Moreover, it is difficult to manufacture using conventional bonding methods. However, according to this embodiment, by bonding at least the nozzle forming member 22 and the piezoelectric transducer 21 with the bonding material 41, the minute gap can be controlled with high precision and electrical conduction can be reliably obtained. Furthermore, since conduction of the common electrode can be obtained all at once, it has the unique effect of simplifying the manufacturing process.

Although not shown in this embodiment (FIGS. 3 and 4), the electrode pattern 35 and the piezoelectric transducer 21 can also be bonded in the same manner as described above. At this time, the electrode pattern 35
Conductivity can also be ensured between the piezoelectric transducer 21 and the piezoelectric transducer 21. Further, the adhesive layer 34 can maintain constant spacing by the conductive spacing regulating member 40. Therefore, this contributes to further stabilizing the distance between the piezoelectric transducer 21 and the nozzle forming member 22, and it is possible to improve the ink droplet ejection characteristics.

The operation of the inkjet head according to this embodiment is as follows. First, a driving voltage is applied from the outside between the electrode pattern 35 and the metal plate 31 via the flexible substrate (FPC) 27. Since the piezoelectric material 32 contracts but the metal layer 31 does not, a bending moment is generated and the piezoelectric transducer 21 is displaced in the thickness direction. Next, when this driving voltage is released, ink droplets are ejected from the nozzle 23 due to the pressure generated by the elastic restoring force of the piezoelectric transducer 21.

It is clear that the manufacturing method of the present invention is effective not only for the cantilevered beam-shaped piezoelectric transducer as described above, but also for the case of a double-sided beam-shaped piezoelectric transducer whose both ends are fixed.

〔Effect of the invention〕

According to the present invention, since the thermal W tension wheel is bonded with a bonding material obtained by mixing a conductive spacing regulating member having α■ and an adhesive having a coefficient of thermal expansion α■, the nozzle forming member and
It is possible to simultaneously achieve space regulation and conduction between the piezoelectric transducer and the piezoelectric transducer. Therefore, the manufacturing process of the inkjet head can be simplified. Moreover, since α5×α■ is used, the amount of shrinkage at the end of curing is larger for the adhesive than for the conductive spacing regulating member. Therefore, the pressing force generated by the difference in the amount of contraction with the adhesive is applied to the spacing regulating member, and the conductive spacing regulating member is brought into close contact with the nozzle forming member and the piezoelectric transducer, resulting in more reliable conduction. have an effect. Further, the conductive spacing regulating member stabilizes the gap between the nozzle forming member and the piezoelectric transducer, which needs to be controlled with high precision in order to stabilize the ink droplet ejection characteristics of the inkjet head. moreover,
By setting the particle size of the conductive spacing regulating member to a desired arbitrary size, the spacing between the bonding layers can be easily set. Due to the above effects, an inexpensive inkjet head with stable ink droplet ejection characteristics can be provided.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a recording apparatus equipped with an inkjet head of the present invention. FIG. 2 is a sectional view of the inkjet head of this embodiment. FIG. 3 is a sectional perspective view of the main part of the inkjet head of this embodiment. FIG. 4 is a sectional view taken along line A-A in FIG. FIG. 5 is a plan view and a sectional view of a conventional inkjet head. Recording medium platen Inkjet head Piezoelectric transducer Nozzle forming member Nozzle adhesive base material Ink metal layer Piezoelectric electrode layer Conductive spacing regulating member Bonding material Above Ro Ganto Seiko Epson Co., Ltd. Attorney Kizobu Tsuchi Suzuki (and 1 other person) ) 9 Inwaji work 2I-to...,L'' / 1st Figure 20: Frame L-frame 22゜゛niku゛no L-type 1 bere thing■3# Figure 2

Claims (2)

[Claims] (1) A nozzle forming member arranged to face a recording medium and having a plurality of nozzles, and a piezoelectric transducer, and configured such that ink is filled between the nozzle forming member and the piezoelectric transducer. In the inkjet head, the conductive spacing regulating member having a coefficient of thermal expansion α_■ and the adhesive having a coefficient of thermal expansion α_■ satisfy α_■<α_■, and the conductive spacing regulating member is dispersed and mixed into the adhesive. An inkjet head, characterized in that at least the nozzle forming member and the piezoelectric transducer are bonded using a bonding material. (2) A nozzle forming member arranged to face the recording medium and having a plurality of nozzles, and a piezoelectric transducer, and configured such that ink is filled between the nozzle forming member and the piezoelectric transducer. A method for manufacturing an inkjet head, wherein a conductive spacing regulating member having a coefficient of thermal expansion α_■ and an adhesive having a coefficient of thermal expansion α_■ satisfy α_■<α_■, and the conductive spacing regulating member is a step of dispersing and mixing in an adhesive to form a bonding material; at least the nozzle forming member and the piezoelectric transducer;
A method for manufacturing an inkjet head, comprising the step of bonding the two with the bonding material.