JP3218793B2 - Inkjet head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention
The present invention relates to an ink jet head for performing printing on paper or the like.

[0002]

2. Description of the Related Art Conventionally, a structure of a substrate for fixing a piezoelectric element is disclosed in, for example, Japanese Patent Application Laid-Open No. 3-73347. This is shown in FIG. A conventional technique will be described with reference to FIG.

In FIG. 6, a piezoelectric element 101 is bonded on a base plate 102. The base plate 102 is made of an insulating member such as silicon, ceramic, glass, and synthetic resin. The electrode 103A and the common electrode 103B are patterned on the base plate. The electrode 103A is integral with the piezoelectric element 1 before the piezoelectric element 101 is divided.
It is processed at the same time as the division processing of No. 01. Drive IC
104 is also designed to be mounted on the electrode 103A that has been processed at the same time.

This conventional example is an ink jet head in which the piezoelectric elements 101 are stacked or a single layer and the displacement in the electric field direction, that is, the d33 direction is used for discharging the ink droplets, but the d31 direction orthogonal to the electric field direction is used. A similar configuration could be obtained for the device.

[0005]

However, the above-mentioned prior art could not solve the problems described below.

First, when driving the piezoelectric elements 101, it is difficult to eliminate a so-called crosstalk factor that mutually affects the piezoelectric elements 101. The piezoelectric element 101 is deformed according to a signal from the driving IC 104. In the case of the conventional example shown in FIG. 6, the piezoelectric element 101 is deformed in the thickness direction, that is, in the direction d33. With this deformation,
That is, the ink pressure is increased to discharge the ink droplets.

The selection and non-selection of the piezoelectric elements 101 are determined by the drive IC 104. However, the problem is that the number of selected piezoelectric elements 101 is much larger than the number of unselected piezoelectric elements 101. This is often the case. In such a case, the reaction force of the deformation of the selected piezoelectric element 101 causes the substrate 10
2 is displaced in a direction opposite to the displacement of the piezoelectric element 101. That is,
The displacement of the piezoelectric element 101 is offset, and the speed and the amount of the ink droplet are reduced.

Further, when the substrate 102 is displaced, the unselected piezoelectric elements 101 are also displaced at the same time. The unselected piezoelectric element 101 is displaced out of phase with the selected piezoelectric element 101, causing unnecessary vibration in the connected ink chamber and deteriorating the flight characteristics of the ink droplet. In a remarkable case, the ink droplets are ejected from the ink chamber to which the non-selected piezoelectric element 101 is connected at an unexpected timing, and the image quality on the recording paper is significantly deteriorated.

In order to prevent these, it is necessary to make the inertial weight of the substrate 102 sufficiently larger than that of the piezoelectric element 101 and to increase the rigidity. The conventional substrate 102 is made of silicon,
Ceramics, glass, synthetic resins, and the like have low specific gravities, making it difficult to secure a sufficient weight, and low rigidity, so that the cause of crosstalk could not be eradicated.

In order to eliminate the cause of the crosstalk, the most suitable material of the substrate 102 is a metal material having a large specific gravity and a high rigidity such as iron or an iron-based alloy. Such a conductive material could not be used as the substrate 102.

This is because the electrodes 103 are directly provided on the substrate 102.
This is because A does not have a function as an individual electrode. Further, it is difficult to process a highly ductile material such as a metal at the same time as a brittle material such as the piezoelectric element 101.

Second, it is necessary to match the arrangement density of the piezoelectric elements 101 with the terminal pitch of the drive IC 104. This is a restriction on at least one of the arrangement density and the terminal pitch, and is not a versatile technology.

Further, it has been necessary to separately prepare means such as wire bonding for connection from the substrate 102 to the power supply circuit.

[0014]

According to the present invention, there is provided an ink jet printer.
The pressure generator is composed of a base plate, a synthetic resin layer formed on the base plate, and a thin film formed on the synthetic resin layer .
Although it is fixed via the electrode layer which is an individual electrode, a configuration without the electrode layer may be used. The end face of the base plate is a pressure generator
Closer to the non-fixed area of the pressure generator than the end face where
A configuration that is located may be used . A polyimide resin is suitable as the synthetic resin. The electrode layer may be patterned before the pressure generator is divided.

[0015]

FIG. 1 is a sectional perspective view of an ink jet head according to one embodiment of the present invention. FIG. 2 shows an arrow a in FIG.
It is principal part sectional drawing from a direction. According to FIGS. 1 and 2,
The details of the present invention will be described.

In FIG. 1, a substrate 100 includes a base plate 5
0, a synthetic resin layer 51, and an electrode layer 52. The inactive part 42 of the piezoelectric element 40 is joined on the electrode layer 52. The tip of the active part 41 of the piezoelectric element 40 is joined to the pressure plate 31. The pressure plate 31 is integral with the diaphragm 30. The diaphragm 30 is joined to the ink chamber wall 21, and the ink chamber wall 21 is joined to the nozzle forming member 10.

The diaphragm 30, the pressure plate 31, and the ink chamber wall 2
1 and a portion surrounded by the nozzle forming member 10 are the ink chambers 20. The ink chamber 20 is filled with ink. The ink chamber 20 is connected to the common channel 22 by an ink supply channel 23.

As shown in FIG. 2, the piezoelectric element 40 has an individual external electrode 43 and a common external electrode 44. The individual external electrode 43 is joined to the electrode layer 52 and is connected to a drive circuit through the flexible printed board 60. The common external electrodes 44 are connected by a common plate 61, and are also connected to an external drive circuit by a flexible printed circuit board 60.

Next, the operation will be described. The piezoelectric element 40 is charged by the drive circuit, and is directed in the direction of arrow b in the drawing, that is, d.
It shrinks slightly in 31 directions. The pressure plate 31 bonded to the piezoelectric element 40 is displaced, and the volume of the ink chamber 20 increases. This volume of ink is supplied to the ink chamber from the common channel 22.

Thereafter, the voltage of the pressure generator 40 is released. Then, the pressure generator 40 returns to the natural length,
The ink pressure in the ink chamber 21 is increased through the pressure plate 31. The ink with the increased pressure is ejected from the nozzle openings 11 to form an image on a recording medium such as paper.

In the present embodiment, the base plate 50
A stainless steel material having a thickness of 1 mm was used, a polyimide resin having a thickness of 10 μm was used as the synthetic resin layer 51, and a copper foil having a thickness of 18 μm plated with 5 μm nickel was used as the electrode layer 52. In the present embodiment, the number of the piezoelectric elements 40 is 48 in one row, and the dimensions of each part are designed so that the displacement of each piezoelectric element 40 is 1 μm.

The reason why the polyimide resin is selected as the synthetic resin is that it has excellent insulation properties.

In the case where a substrate obtained by applying a thin-film electrode to a free-cutting ceramic material is used as the substrate by using the conventional technique, the above-mentioned crosstalk is severe. That is,
When 47 piezoelectric elements 40 excluding the central one of the 48 piezoelectric elements 40 are driven, at the timing when the length of the piezoelectric element 40 returns, the unselected one becomes 0.4 due to the reaction force.
The displacement was μm in the opposite direction. Due to this vibration, the ink droplets are ejected by the recoil from the nozzle openings 11 corresponding to the non-selected piezoelectric elements 40 slightly after the ink droplets are ejected from the nozzle openings 11 corresponding to the selected piezoelectric element 40. Happened.

For this reason, an attempt was made to change the material of the substrate to an alumina substrate having higher rigidity and to use the same structure. That is, by increasing the rigidity, the deformation of the substrate is suppressed to reduce the crosstalk. As a result, the movement of the unselected piezoelectric element 40 could be reduced to 0.3 μm.
Could not be eliminated.

In view of the above, it has been devised to use a metal as the substrate so that the rigidity is higher and the inertial weight is larger.
However, since the conductive material does not allow the individual external electrodes 43 of the piezoelectric element 40 to be routed by the conventional method, an insulating synthetic resin film provided with an electrode layer 52 is adhered to the surface.

At this time, what is used as the synthetic resin film is generally used as a flexible printed circuit board.
A 5 μm copper foil was bonded with a 30 μm adhesive. The synthetic resin film and the base plate 50 were joined with an adhesive having a thickness of 30 μ.

However, with such a configuration, the amount of displacement of the piezoelectric element 40 was not able to secure the designed value of 1 μm in the first place. This is because the total thickness of the synthetic resin film and its adhesive layer is large, the rigidity is low,
This is because the displacement of the piezoelectric element 40 is absorbed.

Finally, by manufacturing the synthetic resin layer 51 as thin as possible, the design value of the displacement can be secured while
It has been found that crosstalk is reduced. In particular,
With the synthetic resin layer 51 having a thickness of 10 μm or less, the displacement of the non-selected piezoelectric element 40 was less than 0.05 μm, and the maximum effect was obtained. However, even in the range of 30 μm or less in thickness, it was possible to eliminate the ejection of ink droplets from the nozzle openings 11 corresponding to the non-selected piezoelectric elements 40, and a sufficient effect was obtained.

Such a thin synthetic resin layer 51 can be formed by applying a solvent obtained by diluting a synthetic resin material before curing to the base plate 50 by a known coating method such as roll coating or dipping, and then curing the film. It can be realized by a method of forming a synthetic resin material in a shape by heating and pressing.

The electrode layer 52 can be formed by applying heat and pressure at the same time as applying the synthetic resin material, curing the synthetic resin material to form the synthetic resin layer 51, and then patterning it by a known photolithography technique. Or synthetic resin layer 5
After the formation of No. 1, it is also possible to perform patterning by an electroless plating technique.

In any case, the electrode layer 52 having good ductility is used.
Conversely, processing the piezoelectric element 40, which is a brittle material, at the same time is difficult because it is difficult to select a cutting tool to be used. However, in the present invention, it is easy to divide the electrode layer 52 into the width of the piezoelectric element 40 in advance by using the existing technology. By doing so, the cutting tool used is the piezoelectric element 4
The most suitable for machining No. 0 could be adopted, and workability could be improved.

The piezoelectric element 40 bonded on the electrode layer 52 divided in advance is cut by a dicer or the like aiming at the gap between the electrode layers 52. At this time, the synthetic resin layer 5
The sum of 1 and the thickness of the electrode layer 52 secures a gap for the blade of the dicer not to contact the base plate 50.

FIG. 3 is a main sectional view of another embodiment of the present invention. The configuration is almost the same as that of FIG. 1, but has no electrode layer 52 in FIG. This is the piezoelectric element 4
0 is bonded to the base plate 50 by the synthetic resin layer 51 which is an insulating adhesive.

Therefore, the working process of the present embodiment is one process of bonding the piezoelectric element 40 and the base plate 50, and is greatly simplified as compared with the first embodiment. That is, the number of manufacturing steps in the first embodiment shown in FIG.
In the present embodiment shown in FIG. 3, the base plate 5
5 of outer processing, bonding of piezoelectric element 40, division of piezoelectric element 40, mounting of common board 61, mounting of flexible printed board 60
The process is shortened.

It is effective to mix a gap material in order to increase the insulating property of the synthetic resin layer 51. The gap material refers to a small diameter glass bead or a finely cut glass fiber.

In the case of a configuration without such an electrode layer 52,
The flexible printed circuit board 60 is directly soldered to the piezoelectric element 40 in order to establish conduction from the piezoelectric element 40 to the drive circuit.

FIG. 4 is a main sectional view of another embodiment of the present invention. In this embodiment, the position of the end face of the base plate 50 is changed in order to increase the rigidity of the base plate 50.

The location where the reaction force generated by the piezoelectric element 40 most affects the vicinity of the end face of the electrode layer 52 to which the piezoelectric element 40 is fixed. Therefore, the crosstalk of the piezoelectric element 40 can be reduced by separating the end face of the base plate 50 from the end face of the electrode layer 52.

That is, the end face of the base plate 50 is
It is assumed that it is at the position indicated by 00. At this time, the piezoelectric element 40
Is displaced, the inertia weight causes the base plate 50 to be deformed by the force causing the deformation of the arrow c in the figure. This is one of the causes of crosstalk. Virtual end face 200
It is a feature of the present embodiment to increase the rigidity by increasing the thickness.

In the present embodiment, the end face of the base plate 50 is sufficiently separated from the end face of the electrode layer 52, so that the amount of displacement of the unselected piezoelectric element 40 due to crosstalk is further compared with the first embodiment. 20% reduction was achieved.

FIG. 5 is a main sectional view of another embodiment of the present invention. In this embodiment, the synthetic resin layer 51 and the electrode layer 5
2 project from the base plate 50.

The overhanging synthetic resin layer 51 and the electrode layer 52
Has a configuration similar to that of a well-known flexible printed circuit board, and enables fine patterning in exactly the same manner.

In this embodiment, by mounting the driving IC 80 here, the process is simplified and the device is downsized.

The pattern of the electrode layer 52 protruding from the base plate 50 can be formed in any shape without being restricted by the processing pitch of the piezoelectric element 40. Because, when processing the piezoelectric element 40, so as not to interfere with the processing blade,
This is because it is easy to bend and miss.

Although several embodiments using the vertical laminated piezoelectric element 40 have been described above, the present invention may also be applied to a horizontal type piezoelectric element 40 as shown in FIG. This is also effective for the laminated piezoelectric element 101.
Further, the present invention can be easily applied to a single-layer piezoelectric element or a piezoelectric element utilizing flexural vibration.

[0046]

As described above, according to the present invention, the number of piezoelectric elements 40 selected for ejection is reduced by the number of non-selected piezoelectric elements 40.
When the number is overwhelmingly large, the substrate 100 is displaced by the displacing reaction force of the selected piezoelectric element 40,
Defective ejection that occurs due to displacement of the unselected piezoelectric element 40 can be completely eliminated. As a result, the image quality finally formed on the recording medium was improved, and an ink jet head capable of performing good recording could be obtained.

[0047]

[Brief description of the drawings]

FIG. 1 is a perspective view of a main cross section of an ink jet head according to an embodiment of the present invention.

FIG. 2 is a main sectional view of the embodiment of the present invention shown in FIG. 1 as viewed from an arrow a.

FIG. 3 is a main sectional view of another embodiment of the present invention.

FIG. 4 is a main sectional view of another embodiment of the present invention.

FIG. 5 is a main sectional view of another embodiment of the present invention.

FIG. 6 is a perspective view of a main section of a conventional inkjet head.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 nozzle forming member 11 nozzle opening 20 ink chamber wall 21 ink chamber 22 common flow path 23 ink supply port 30 diaphragm 31 pressure plate 40 vertical laminated piezoelectric element 41 active part of piezoelectric element 40 inactive part of piezoelectric element 43 External individual electrode of piezoelectric element 40 44 External common electrode of piezoelectric element 40 50 Base plate 51 Insulating synthetic resin layer 52 Electrode layer 60 Flexible printed board 61 Common electrode 200 Virtual end face of base plate 50

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B41J 2/045 B41J 2/055

Claims (5)

(57) [Claims] A pressure generator fixed to a base plate and a substrate made of a synthetic resin layer; a diaphragm separating the ink chamber from the pressure generator; and an ink chamber wall separating the ink chambers on the diaphragm. An ink jet head having a nozzle forming member disposed on the ink chamber wall and having a nozzle opening, and a drive circuit for driving the pressure generator, wherein the pressure generator is mounted on a base plate made of metal. Synthetic resin layer
An ink jet head, which is fixed via an ink jet head. 2. The semiconductor device according to claim 1, wherein the substrate includes the base plate, the synthetic resin layer formed on the base plate, and an electrode layer that is a thin-film individual electrode formed on the synthetic resin layer. The inkjet head according to claim 1, wherein 3. An ink jet head according to claim 1, wherein an end face of said base plate is located closer to a non-fixed area of the pressure generator than an end face fixing said pressure generator. 4. The ink jet head according to claim 1, wherein said synthetic resin layer is made of a polyimide resin. Wherein said electrode layer is, according to the width of the pressure generator, characterized in that it is pre-patterned 請
The inkjet head according to claim 2 .