JP2000127380A - Ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet head having invariable dimensional accuracy error or displacement characteristics of piezoelectric element and exhibiting a good ink ejection performance. SOLUTION: First, second, third and fourth sheet-like piezoelectric layers 21, 22, 23 and 24 are laminated while screen printing individual electrodes 25 and common electrodes 26 between respective layers and a first thin metal film 27 is formed on the uppermost layer while a second thin metal film 28 is formed on the lowermost layer thus constituting a piezoelectric element 20. The first thin metal film 27 has a thin chromium layer on the side being bonded to the first piezoelectric 21 and a thin gold layer is formed on the thin chromium layer. The second thin metal film 28 has a thin chromium layer on the side being bonded to the fourth piezoelectric 24 and a thin gold layer is formed on the thin chromium layer. The thin gold layer is bonded firmly to a cavity plate 10 made of a silicon material through eutectic reaction. First and second thin metal films 27, 28 are employed as electrodes for repolarization processing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of an ink jet head device used for an ink jet printer or the like.

[0002]

2. Description of the Related Art For example, an ink jet printer head used in an ink jet printer includes a cavity plate having a plurality of ink pressure chambers and an ink reservoir for storing ink, and a plurality of positively or negatively charged electrodes. And a nozzle plate having a nozzle hole communicating with the ink pressure chamber of the cavity plate. When printing is performed, an electric field is applied to the piezoelectric element to displace the piezoelectric element, thereby generating a pressure wave in the ink in the ink pressure chamber and discharging the ink droplet from a nozzle hole communicating with the ink pressure chamber. In such an ink jet printer head, it is important from the point of print quality that the ejection characteristics are uniform.

To further explain the structure of the ink jet printer head, the piezoelectric element is formed in a plate shape, and the ink pressure chamber is formed with a plurality of ink grooves on the surface of the cavity plate. A piezoelectric element composed of a plate-shaped piezoelectric body and an electrode is joined to the surface of the substrate, and an ink groove is covered with the piezoelectric element. For joining the piezoelectric element and the cavity plate, a joining method using a resin adhesive is suitably used as a low-cost and simple method. Joining by this method has the advantage that it is less affected by the roughness of the adherend surface due to the fluidity of the adhesive. Therefore, even if the surface of the members constituting the ink jet printer, such as the cavity plate and the piezoelectric element, is rough, the members can be joined to each other by using, for example, an epoxy adhesive. That is, an epoxy-based adhesive is applied to the surface of the member, and each member is temporarily fixed to a predetermined position, and then heated at about 100 to 200 ° C. for about 1 hour to cure the adhesive. Thereby, each member can be joined, and an ink jet printer head can be manufactured.

[0004]

However, since a resin adhesive is used for joining the members constituting the ink jet printer head, the thickness and amount of the adhesive layer are reduced when joining to a fine portion. There is a problem that it is necessary to control the thickness accurately and it is difficult to control the thickness and amount of the adhesive layer.

[0005] If the amount of the adhesive is insufficient, the dimensional accuracy is negatively deviated or the bonding is poor. If the amount of the adhesive is excessive, the dimensional accuracy is deviated positively or the adhesive is protruded. Occurs. For example, if the amount of the adhesive is insufficient, poor adhesion causes crosstalk of the ink pressure wave generated by the piezoelectric element between the ink pressure chambers of the cavity plate, which should be separated and independent by the partition walls. In some cases, printing of a portion, that is, printing failure may occur. On the other hand, if the amount of the adhesive is excessive, the protrusion of the adhesive causes deformation of the ink flow path, which may cause uneven printing due to an increase in flow path resistance.

When the ink is used at a high temperature of about 100 ° C., the adhesive may be deteriorated depending on the kind of the adhesive. For example, if the quality of the adhesive changes at the joint between the cavity plate and the piezoelectric element, the mechanical properties of the adhesive change, and the displacement characteristics of the piezoelectric element when an electric field is applied change. In the worst case, there is a problem that nozzle clogging occurs due to partial breakage of the adhesive layer, resulting in poor printing and a reduction in the yield of the inkjet printer head.

[0007] The displacement characteristics of the piezoelectric element change with the lapse of time since the polarization process was performed. That is,
Polarization treatment is a process in which the molecular structure of a piezoelectric element is forcibly distorted by high temperature and high pressure.Therefore, the distortion of the molecular structure is eliminated over time, and the displacement characteristics of the piezoelectric element deteriorate. is there.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been made in consideration of the dimensional accuracy error due to an excessive amount or an insufficient amount of an adhesive, or the change in displacement characteristics of a piezoelectric element due to the deterioration of an adhesive.
It is another object of the present invention to provide an ink jet head device capable of reliably preventing a drop in ink ejection performance due to a deterioration in displacement characteristics of a piezoelectric element due to a temporal change from the time of performing a polarization process.

[0009]

According to a first aspect of the present invention, there is provided an ink jet head device, wherein ink is stored in an ink pressure chamber provided at a predetermined interval in a cavity plate, and the ink is stored in a piezoelectric device. An ink jet head device for ejecting the ink from a nozzle by applying pressure fluctuation by an element, wherein the metal thin film is formed on both surfaces of the piezoelectric element and has a surface layer made of at least gold, and the metal thin film for repolarization processing. And a silicon cavity plate joined by using a eutectic reaction to a surface layer film made of gold.

According to the ink jet head device of the first aspect, the cavity plate and the piezoelectric element are one of the metal thin film formed on both surfaces of the piezoelectric element and the surface layer made of gold and the cavity plate. Since bonding is performed using a eutectic reaction with a silicon material, bonding with high dimensional accuracy is performed. Therefore, the ink jet head device is manufactured with high accuracy as a whole, and the ink ejection characteristics are improved. In addition, the bonding failure is prevented, and the operation failure of the inkjet head device is prevented. For example, since there is no shortage of the adhesive, each ink pressure chamber can be reliably separated by the partition of the cavity plate, and each ink pressure chamber is reliably provided independently. This prevents malfunctions such as crosstalk in the pressure wave of the ink during ink ejection. Also, there is no deformation of the ink flow path due to the protrusion of the adhesive,
Non-uniform printing due to an increase in flow path resistance, a change in the ink ejection direction, and malfunctions due to clogging of nozzle holes are prevented. Moreover, since the metal thin film used for the bonding by such eutectic reaction is used as an electrode for repolarization processing, the subdivision processing can be easily performed without disassembling the ink jet head device, as described above. Good ink ejection performance in an early stage of production is maintained for a long period of time.

According to a second aspect of the present invention, in order to solve the above problem, in the inkjet head device according to the first aspect, the metal thin film for repolarization is formed on both surfaces of the piezoelectric element. A surface layer film made of gold is formed on the chromium thin film thus formed.

According to the ink jet head device of the present invention, the metal thin film for repolarization processing is formed by forming a surface layer film made of gold on a chromium thin film formed on both surfaces of the piezoelectric element. Therefore, the adhesion strength between the chromium thin film and the surface layer film made of gold is improved, and as a result, the metal thin film is firmly bonded to the piezoelectric element. Therefore, the surface layer film made of the metal thin film of gold and the silicon material of the cavity plate are firmly joined by joining using a eutectic reaction, so that the piezoelectric element and the cavity plate are firmly joined.

According to a third aspect of the present invention, there is provided an ink jet head device according to the second aspect, wherein nickel is provided between the chromium thin film and the surface layer film made of gold. A thin film is formed.

According to the third aspect of the present invention, the nickel thin film is formed between the chromium thin film and the surface layer made of gold of the metal thin film.
Stronger bonding between chromium thin film and nickel thin film,
Further, due to the stronger bonding between the nickel thin film and the gold thin film, the piezoelectric element and the gold thin film are more strongly bonded. Accordingly, the gold thin film and the silicon material of the cavity plate are firmly joined by joining using the eutectic reaction, so that the piezoelectric element and the cavity plate are more firmly joined.

According to a fourth aspect of the present invention, there is provided an inkjet head device according to any one of the first to third aspects, wherein the inkjet head device is provided with a silicon cavity plate. The metal thin film on the opposite side to the metal thin film used for bonding also serves as a driving electrode of the piezoelectric element.

According to the ink jet head device of the present invention, the surface layer made of gold of one of the metal thin films provided on both surfaces of the piezoelectric element is bonded to the silicon cavity plate. The other metal thin film on the opposite side is used not only as an electrode during the above-described repolarization process but also as a driving electrode of the piezoelectric element. Accordingly, an electric field acting on the outermost piezoelectric body is generated, and the other metal thin film functions as a constraining layer, so that the outermost layer is deformed in the unimorph mode or the bimorph mode, and the amount of deformation of the piezoelectric element is increased. I do.

According to a fifth aspect of the present invention, there is provided an ink jet head device for storing ink in an ink pressure chamber provided at a predetermined interval in a cavity plate, and applying a pressure fluctuation to the ink by a piezoelectric element. An ink jet head device for ejecting the ink from a nozzle, comprising: a metal thin film for repolarization processing formed on both surfaces of the piezoelectric element and having a surface film made of at least aluminum; and a surface film made of aluminum of the metal thin film. And a glass cavity plate joined using anodic bonding.

According to the ink jet head device of the fifth aspect, the cavity plate and the piezoelectric element are one of the metal thin films formed on both surfaces of the piezoelectric element and the surface layer made of aluminum and the one of the cavity plate. Since bonding is performed using anodic reaction with glass, bonding with high dimensional accuracy is performed. Therefore, the ink jet head device is manufactured with high accuracy as a whole, and the ink ejection characteristics are improved. In addition, the bonding failure is prevented, and the operation failure of the inkjet head device is prevented. For example, since there is no shortage of the adhesive, each ink pressure chamber can be reliably separated by the partition of the cavity plate, and each ink pressure chamber is reliably provided independently. This prevents malfunctions such as crosstalk in the pressure wave of the ink during ink ejection. Also, there is no deformation of the ink flow path due to the protrusion of the adhesive,
Non-uniform printing due to an increase in flow path resistance, a change in the ink ejection direction, and malfunctions due to clogging of nozzle holes are prevented. Moreover, since the metal thin film used for the bonding by such an anodic reaction is used as an electrode for repolarization, the subdivision processing can be easily performed without disassembling the inkjet head device, and Good ink ejection performance in the early stage of manufacturing is maintained for a long period of time.

According to a sixth aspect of the present invention, there is provided an ink jet head device according to the fifth aspect, wherein the metal thin film is opposite to the metal thin film used for bonding to the glass cavity plate. The metal thin film on the side also serves as a driving electrode of the piezoelectric element.

According to the ink jet head device described above, one of the aluminum thin films among the metal thin films provided on both surfaces of the piezoelectric element is used for bonding to the glass cavity plate. However, the other aluminum thin film on the opposite side is used not only as an electrode during the above-described repolarization process but also as a driving electrode of the piezoelectric element. Accordingly, an electric field acting on the outermost piezoelectric body is generated, and the other metal thin film functions as a constraining layer, so that the outermost layer is deformed in the unimorph mode or the bimorph mode, and the amount of deformation of the piezoelectric element is increased. I do.

[0021]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) First, a first embodiment of the present invention will be described with reference to FIGS. For comparison with the present embodiment, the conventional example shown in FIG. 6 is also referred to.

The ink jet printer head 1 shown in FIG. 1 is mounted on an ink jet printer. Here, a brief description will be given of the vicinity of a driving unit, which is a print recording unit, of the inkjet printer. This part is mainly composed of a rotatable platen that conveys print recording paper, a motor that applies a rotational force to the platen via a gear mechanism, and an ink jet printer head that is installed facing the platen. Be composed. The ink jet printer head is installed on a carriage together with an ink supply device. This carriage is movably supported along two guide rods installed in parallel with the axis of the platen. A timing belt stretched between a pair of pulleys is fixed to the carriage wall, and is configured to be able to transmit the rotational motion of another motor connected to one of the pulleys. With such a configuration, the platen rotates in response to the rotational force of the motor to feed the print recording paper at a predetermined speed in a predetermined direction, and in synchronization with this, the rotational force of another motor is synchronized with the timing belt. The carriage received via moves along the guide rod. At this time, the ink jet printer head installed on the carriage
Since the ink is ejected based on the recording information signal output by the control means, a predetermined image or the like is formed on the print recording paper conveyed by the platen.

Next, the ink jet printer head 1 according to the present embodiment will be described. An ink jet printer head 1 as an ink jet head device according to the present embodiment has a cavity plate 10, a piezoelectric element 20, a head heater 30 as shown in a sectional view of FIG.
And a nozzle member 40.

The cavity plate 10 is formed of a silicon material, and has a smooth joining surface with the piezoelectric element 20. The piezoelectric element 20 of the cavity plate 10
The ink reservoir 11 and the ink pressure chamber 12
Are formed. By bonding the piezoelectric element 20 to the bonding surface of the cavity plate 10 and covering the cavity plate 10 from above, an ink reservoir 11 and a plurality of ink pressure chambers 12 are formed inside the cavity plate 10 as shown in FIG. It is formed. Further, a plurality of through holes 13 are formed at the tip of the cavity plate 10 so as to correspond to the respective ink pressure chambers 12. Further, as shown in FIG. 2 which is a cross-sectional view taken along the line XX ′ of FIG. 1, each ink pressure chamber 12 is separated by a partition wall 14 so as to be an independent pressure chamber.

The piezoelectric element 20 is formed in a plate shape as shown in FIG. Although not shown in FIG. 1, the piezoelectric element 20 includes a first piezoelectric body 2 as shown in FIG.
1, a second piezoelectric body 22, a third piezoelectric body 23, a fourth piezoelectric body 24, and a plurality of individual electrodes 25 sandwiched between the piezoelectric bodies.
And a plurality of common electrodes 26 alternately provided with the individual electrodes 25, and a first metal thin film 27 and a second metal thin film 28 provided so as to sandwich these piezoelectric members and electrodes from above and below.
It is composed of 1st piezoelectric body 21, 2nd piezoelectric body 2
The second, third and fourth piezoelectric bodies 23 and 24, the individual electrodes 25, and the common electrode 26 are each formed in a sheet shape, and the piezoelectric element 20 is formed by stacking these. 1st piezoelectric body 21, 2nd piezoelectric body 2
Each of the second, third and fourth piezoelectric bodies 23 and 24 is made of PZT (lead zircon titanate (Pb (Zr, Ti)).
O ₃ ) or the like. Further, as shown in FIG. 2, each piezoelectric body is polarized in the stacking direction. Each individual electrode 25 is arranged so as to correspond to each ink pressure chamber 12 formed in the cavity plate 10, and is formed in a band shape corresponding to the elongated shape of the ink pressure chamber 12. Each common electrode 26 is arranged so as to correspond to each partition 14 formed on the cavity plate 10, and is formed in a strip shape corresponding to the elongated shape of the partition 14. First metal thin film 27
Is a laminated thin film in which chromium (Cr) is formed on the bonding surface with the first piezoelectric body 21 and gold (Au) is formed on the chromium. The second metal thin film 28 is a laminated thin film in which chromium (Cr) is formed on the joint surface with the fourth piezoelectric body 24 and gold (Au) is formed on the chromium.

The head heater 30 is a heater formed in a flat plate shape, and is joined to the lower surface of the cavity plate 10 in a planar manner. The head heater 30 is provided over the entire lower surface of the cavity plate 10 and heats the ink in the ink reservoir 11 and the ink pressure chamber 12 and also heats the piezoelectric element 20 at the time of repolarization processing described later. .

The nozzle member 40 is formed of a silicon material, and the nozzle member 40 has a concave groove for forming a nozzle chamber 41 and a nozzle hole 42. Further, a bonding thin film 43 made of gold is formed on a bonding surface of the nozzle member 40 with the cavity plate 10. Further, the piezoelectric element 2 is provided on the joint surface between the nozzle member 40 and the piezoelectric element 20.
A bonding thin film 44 made of gold formed on the surface of No. 0 and chromium formed on the gold is formed. By joining the nozzle member 40 with the cavity plate 10 and the piezoelectric element 20 via such joining thin films 43 and 44, a plurality of nozzle chambers 41 are provided inside the nozzle member 40.
And a plurality of nozzle holes 42 are formed. Each nozzle chamber 41
The nozzle holes 42 correspond to the ink pressure chambers 12 formed in the cavity plate 10, respectively. Each of the ink pressure chambers 12 and each of the nozzle chambers 41 are connected via the through-hole 13 as shown in FIG. As a result, the ink reservoir 11, the ink pressure chamber 12, the through hole 13, the nozzle chamber 4
A series of ink flow paths composed of 1 and the nozzle holes 42 are formed.

Next, an example of the control means for controlling the driving of the ink jet printer head 1 of the present embodiment as described above will be described with reference to FIG. As shown in FIG. 3, the control means of the present embodiment includes a CP connected via a bus 50.
U51, ROM 52, RAM 53, heater control unit 54,
It has a drive voltage generator 55 and a polarization voltage generator 56.

The ROM 52 stores a printing program for driving the ink jet printer head 1 based on the printing data to perform printing, and a piezoelectric element at least at one of a power-on, a printing start, and a periodic maintenance. Various control programs such as a repolarization processing program for repolarizing 20 are stored. In the RAM 53,
A timer area for setting the timing of performing the repolarization process is formed, and a print data storage area for storing print data is formed. The heater control unit 54 is connected to the head heater 30 in FIGS. 1 and 2, and detects a temperature from a thermistor 31 (not shown in FIGS. 1 and 2) provided in the head heater 30. The head heater 30 is adjusted to a predetermined temperature. The drive voltage generator 55 is connected to the individual electrodes 25 and the common electrode 26 of the piezoelectric element 20 shown in FIGS. 1 and 2, and generates a drive voltage during a printing operation. Further, the polarization voltage generator 56 is connected to the first metal thin film 27 and the second metal thin film 28 shown in FIG.
When a repolarization process is instructed from U51, a polarization voltage for repolarizing the piezoelectric element 20 is generated for the first metal thin film 27 and the second metal thin film. In the printing operation, a ground potential is applied to the first metal thin film 27 and a positive voltage having the same value as that of the individual electrode 25 is applied to the second metal thin film 28.

Here, the ink jet printer head 1
The operation at the time of printing will be described. When printing is performed, ink is supplied from the ink supply device to each of the ink pressure chambers 12 formed in the cavity plate 10. Then, the drive voltage generator 55 of the control means shown in FIG.
When a ground voltage is applied to the common electrode 26 of the piezoelectric element 20 and a positive voltage is applied to the individual electrode 25, the first piezoelectric body 21, the second piezoelectric body 22, the third piezoelectric body 23, and the fourth piezoelectric body 24 However, as shown in FIG. 4, the first piezoelectric member 21 deforms in the shear mode protruding into the ink pressure chamber 12.
Is deformed in a unimorph mode using the first metal thin film 27 as a constraining layer. Due to this deformation, a pressure wave is generated in the ink stored in the ink pressure chamber 12. The pressure wave is transmitted to the nozzle chamber 41 of the nozzle member 40 via the through hole 13 formed in the cavity plate 10. As a result, ink is ejected from the nozzle holes 42. In this case, the ink is ejected in synchronization with the moving speed and direction of the ink jet printer head 1 on the guide rod, or with the conveyance speed of the print recording paper by the platen. Thus, an image or the like based on the information signal is formed. The share mode is
This is a mode of deformation that occurs when a voltage is applied to a polarized piezoelectric body in a direction perpendicular to the direction of polarization, and occurs when the piezoelectric body undergoes a thickness slip in a direction parallel to the polarization direction. This is a deformation mode. In unimorph mode, when a voltage is applied in the same or opposite direction to the polarization direction of a piezoelectric body having an elastic body fixed to one of its surfaces, the piezoelectric body expands and contracts in a direction perpendicular to the polarization direction, This is a mode of bending deformation caused by the elastic body trying to restrain this expansion and contraction.

Next, the joining structure of the cavity plate 10 and the piezoelectric element 20 and the joining structure of the cavity plate 10, the piezoelectric element 20, and the nozzle member 40 according to the present embodiment will be described. The cavity plate 10 is formed of a silicon material as described above,
The surface to be bonded to the zero piezoelectric element 20 is smoothed. Further, the second metal thin film 28 is formed on the fourth piezoelectric body 24 of the piezoelectric element 20.
Is formed of chromium, and is joined to the fourth piezoelectric body 24 with high adhesion strength. In addition, chromium and gold constituting the second metal thin film 28 are mutually diffused by heat compression and strongly bonded to each other. Then, the gold thin film of the second metal thin film 28 and the silicon material of the cavity plate 10 are mutually diffused by the heat and pressure bonding, and are strongly bonded to each other by the eutectic reaction. Thereby, the surface of the second metal thin film 28 and the bonding surface of the cavity plate 10 are firmly bonded in a state of being in close contact.

Similarly, the silicon material of the nozzle member 40 and the gold of the bonding thin film 43 are mutually diffused by heat and pressure, and are strongly bonded to each other by a eutectic reaction. Further, the silicon material of the cavity plate 10 and the gold of the bonding thin film 43 also interdiffuse by heat compression, and are strongly bonded to each other by a eutectic reaction. Further, the chromium of the bonding thin film 44 is bonded to the piezoelectric element 20 with a high adhesion strength, and the chromium of the bonding thin film 44 and the gold of the bonding thin film 44 are mutually diffused by heat compression,
Tightly bind to each other. Then, the gold of the bonding thin film mutually diffuses with the silicon material of the nozzle member 40 by heat compression, and is firmly bonded to each other by a eutectic reaction.

The thickness of each thin film is set with high precision. Specifically, the film thickness is formed to a predetermined value within a range of about 0.1 to 3 μm, for example, 1 μm. However, the thickness of each thin film can be adjusted to be thinner or thicker. Next, the method for manufacturing the inkjet printer 1 according to the present embodiment will be described.

First, a method of manufacturing the piezoelectric element 20 will be described. An individual electrode 25 and a common electrode 26 are formed on the entire surface of a sheet-like first piezoelectric body 21 by screen printing, and a second piezoelectric body 22 is formed thereon. Laminate. Hereinafter, similarly, the second piezoelectric body 22, the third piezoelectric body 23, and the fourth piezoelectric body 24 are laminated while forming the individual electrodes 25 and the common electrode 26. Next, the laminate thus formed is
Vacuum press and bake. Subsequently, these piezoelectric bodies are polarized in the stacking direction from the fourth piezoelectric body 24 to the first piezoelectric body 21.

Next, a method of manufacturing the cavity plate 10 and the nozzle member 40 will be described. The cavity plate 10 and the nozzle member 40 are formed by polishing the surface of a plate-like silicon material so as to be substantially mirror-finished.
The concave grooves for forming the ink reservoir 11 and the ink pressure chamber 12 of the cavity plate 10, the nozzle chamber 41 of the nozzle member 40, and the like are formed by forming a resist mask patterned into the respective shapes on a silicon plate, using hydrofluoric acid or the like. Acids such as a mixture of hydrofluoric acid and nitric acid, or cesium hydroxide,
It is formed by performing chemical etching using an alkali mainly composed of potassium hydroxide, ethylenediamine, or the like. In this case, the groove processing may be performed using ion etching which is a dry process. Moreover, you may process by methods, such as a shot blast.

Next, a method of joining the cavity plate 10 and the piezoelectric element 20 will be described. First, the surfaces of the first piezoelectric body 21 and the fourth piezoelectric body 24 of the piezoelectric element 20 are etched to roughen the surfaces. In the etching solution,
Acids such as hydrofluoric acid, borofluoric acid, nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, and perchloric acid are preferably used. You may use the etching liquid which mixed these two or more types.

Next, the first piezoelectric body 2 roughened by etching
Chromium is thinned on the surfaces of the first and fourth piezoelectric bodies 24 by sputtering or vapor deposition to form a chromium thin film. Then, the surface of the chromium thin film is polished and mirror-finished.

Next, on the mirror-finished chromium thin film, gold is thinned by sputtering or vapor deposition to form a first metal thin film 27 and a second metal thin film 28. First metal thin film 2
7, the thickness of the second metal thin film 28 and the thickness of the bonding thin film 44 are, for example, about 1 μm. Since the underlying chromium thin film is mirror-finished, the first metal thin film 27 and the second metal thin film 28 are also formed on the mirror surface.

Next, the piezoelectric element 20 on which the first metal thin film 27 and the second metal thin film 28 are formed and the cavity plate 10 made of a silicon material are arranged while being aligned with each other. The surface of the two-metal thin film 28 and the surface of the cavity plate 10 are brought into contact with each other, and heated and pressed. Eutectic temperature of silicon-gold binary alloy is about 363
° C, the temperature of the thermocompression bonding is reduced to a temperature around 40 ° C.
Set between 0 ° C and 600 ° C. As a result, silicon and gold diffuse into each other, and the two are firmly adhered to each other.

As described above, the piezoelectric element 20 and the cavity plate 10 are firmly joined with the dimensional accuracy via the second metal thin film 28.

Next, a method of joining the nozzle member 40 to the piezoelectric element 20 and the cavity plate 10 will be described.

First, on the bonding surface of the piezoelectric element 20 with the nozzle member 40, chromium is thinned by sputtering or vapor deposition in the same manner as described above to form a chromium thin film, and then gold is thinned by sputtering or vapor deposition. ,
A bonding thin film 44 is formed. Next, cavity plate 1
On the bonding surface of the nozzle member 40 of No. 0, gold is thinned by sputtering or vapor deposition so as to have the same thickness as the bonding thin film 44, and the bonding thin film 43 is formed.

The piezoelectric element 20 and the cavity plate 10 on which the bonding thin films 44 and 43 are formed
And the nozzle member 40 formed of a silicon material are arranged while being aligned, and the surface of the bonding thin film 44 on the piezoelectric element 20 side, the surface of the bonding thin film 43 on the cavity plate 10 side, and the surface of the nozzle member 40 are aligned. They are brought into contact with each other and are heat-pressed. Eutectic temperature of silicon-gold binary alloy is about 363
° C, the temperature of thermocompression bonding is set
Set between 0 ° C and 600 ° C. As a result, silicon and gold diffuse into each other, and the two are firmly adhered to each other.

As described above, the piezoelectric element 20, the cavity plate 10, and the nozzle member 40 are firmly joined with good dimensional accuracy via the joining thin films 44 and 43.

Finally, the head heater 30 is bonded to the lower surface of the cavity plate 10 using a resin adhesive or the like, and the ink jet printer head 1 is completed.

As described above, the thickness of the metal thin film used for bonding the piezoelectric element 20, the cavity plate 10, and the nozzle member 40 and the thickness of the plating layer of the bonding thin film can be set with high dimensional accuracy. Thereby, the joining of the piezoelectric element 20 and the cavity plate 10 and the joining of the piezoelectric element 20 and the cavity plate 10 to the nozzle member 40 can be performed with high dimensional accuracy. Therefore, the inkjet printer head 1 can be manufactured with high accuracy as a whole, and the ink ejection characteristics of the inkjet printer head 1 can be improved. In addition, poor joining can be prevented, and malfunction of the inkjet printer head 1 can be prevented.

Further, by joining the piezoelectric element 20 and the cavity plate 10 with a chromium layer, each ink pressure chamber 12 can be reliably separated by the partition wall 14, and each ink pressure chamber 12 can be reliably made independent. Thereby, it is possible to prevent malfunctions such as crosstalk occurring in the pressure wave of the ink at the time of ink ejection. In addition, due to poor contact of the nozzle member 40, the through-hole 13, the nozzle hole 42, etc.
Deformation of the ink flow path can prevent non-uniform printing due to an increase in flow path resistance, a change in ink ejection direction, and a malfunction due to clogging of the nozzle hole 42 and the like.

The chrome layer enables the piezoelectric element 20, the cavity plate 10, and the nozzle member 40 to be joined with high dimensional accuracy.
Even if the sizes of the nozzles 0 and the nozzle members 40 are greatly reduced, the sizes of the cavity plate 10 and the nozzle members can be reduced, and the ultra-small inkjet printer head 1 can be realized.

Further, the chromium layer has excellent durability in a high-temperature environment as compared with the adhesive. Thus, for example, 1
Even when the inkjet printer head 1 is used in a high temperature environment of 00 ° C. or more, the bonding state of the cavity plate 10 and the nozzle member 40 is stable, a strong bonding force is maintained, and deformation can be prevented. Thus, the ejection characteristics and the like of the ink ejected from the nozzle holes 42 can be maintained with high accuracy.

The extremely excellent effect of the ink jet printer head 1 according to the present embodiment as described above becomes clearer by comparing with the conventional ink jet printer head 1 shown in FIG.

A conventional ink jet printer head 1 shown in FIG.
Further, a nozzle member (not shown) is joined using an adhesive 60 made of resin.

Therefore, it is difficult to accurately control the thickness and amount of the adhesive layer when bonding to a fine portion. If the amount of the adhesive is insufficient, the dimensional accuracy may be negatively deviated. Adhesion failure occurs. Conversely, if the amount of the adhesive is excessive, a positive deviation in dimensional accuracy occurs or the adhesive protrudes. For example, if the amount of the adhesive is insufficient, poor adhesion causes crosstalk of the ink pressure wave generated by the piezoelectric element between the ink pressure chambers of the cavity plate, which should be separated and independent by the partition walls. In some cases, printing of a portion, that is, printing failure may occur. On the other hand, if the amount of the adhesive is excessive, the protrusion of the adhesive causes deformation of the ink flow path, which may cause uneven printing due to an increase in flow path resistance.

When the ink is used at a high temperature of about 100 ° C., the adhesive may deteriorate depending on the type of the adhesive. For example, if the quality of the adhesive changes at the joint between the cavity plate and the piezoelectric element, the mechanical properties of the adhesive change, and the displacement characteristics of the piezoelectric element when an electric field is applied change. In the worst case, there is a problem that nozzle clogging occurs due to partial breakage of the adhesive layer, resulting in poor printing and a reduction in the yield of the inkjet printer head.

On the other hand, the ink jet printer head 1 of the present embodiment can perform a good ink discharge operation without a printing defect unlike the related art.

Moreover, since the ink-jet printer head 1 of the present embodiment uses the metal thin film used for the eutectic bonding as the electrode for the repolarization process as described above, a long time has elapsed since the execution of the polarization process. Even in this case, the molecular structure of the piezoelectric element can be maintained in a distorted state, and deterioration of the displacement characteristics of the piezoelectric element can be reliably prevented.

On the other hand, in the conventional ink jet printer head, as shown in FIG.
Since only 1 is provided, the operation of removing the piezoelectric element 20 from the cavity plate 10 is required to perform the repolarization process, which is very difficult.

However, in the ink jet printer head 1 of the present embodiment, since the first metal thin film 27 and the second metal thin film 28 are used as they are as the electrodes for the repolarization process, the conventional disassembling operation is unnecessary. The repolarization process can be easily performed.

Hereinafter, the repolarization processing in the present embodiment will be described with reference to the flowchart of FIG.

First, when the power of the ink jet printer is turned on (step S1), as one of the initial settings of the ink jet printer, set time data indicating the time at which the repolarization process is performed after a predetermined time has elapsed from the current time. Is stored in the timer area, and the polarization temperature data is sent from the CPU 51 to the heater control unit 54. Then, the heater control unit 54 to which the temperature data is input heats the piezoelectric element 20 by raising the temperature of the head heater 30 to a temperature equal to or higher than the polarization temperature (for example, 130 ° C.) used for the polarization processing of the piezoelectric element 20 (step S
2).

When the piezoelectric element 20 reaches the polarization temperature, C
When the repolarization instruction data is transmitted from the PU 51 to the polarization voltage generation unit 56, the polarization voltage (for example, 80 V) used for the polarization processing is generated by the polarization voltage generation unit 56. Specifically, the first metal thin film 27
Is applied with a ground voltage, and a positive polarization voltage is applied to the second metal thin film 28. As a result, the piezoelectric element 20 is re-polarized, and the displacement characteristics at the time of manufacturing the ink jet printer are restored (step S4).

When the repolarization process is completed as described above,
Normal temperature data is sent from the CPU 51 to the heater control unit 54 so that the inkjet printer operates in a normal state, and the head heater 30 is set to a temperature slightly higher than the melting temperature of the hot melt ink (for example, 105
C), the hot melt ink is melted. At the same time, the time data of the timer built in the CPU 51 is compared with the set time data of the timer area formed in the RAM 53, and it is determined whether a predetermined period has elapsed (step S4).

If it is determined that the time data has become equal to or greater than the set time data and the predetermined period has elapsed (step S4; YES), the process is re-executed from step S2, and the repolarization process is performed. become. On the other hand, if it is determined that the predetermined period has not elapsed (step S4; NO), it is determined whether a print command has been input from an information processing device (not shown) via an interface (not shown) (step S5). If it is determined that the print command has not been input (step S5; NO), the above-described step S4 is re-executed, and steps S4 and S5 are repeatedly executed to enter a standby state.

On the other hand, if it is determined that a print command has been input (step S5; YES), the above-described step S5 is executed.
As in the operations of Step 2 and Step S3, initialization (Step S6) and repolarization processing (Step S7) are performed.
After the piezoelectric element 20 is restored to the displacement characteristics at the time of manufacturing the inkjet printer 1, a printing operation is performed.

As described above, according to the present embodiment, before starting printing, when the power of the ink jet printer is turned on, and by periodically performing the repolarization process, the ink can be used even after aging of the ink jet printer. Can be discharged at a desired discharge amount, and the image quality can be maintained in a good state.

In this embodiment, an example has been described in which the repolarization process is performed before printing, when the power of the inkjet printer is turned on, and periodically, but the present invention is not limited to this. It is sufficient that the repolarization process is performed on at least one of the occasions.

In this embodiment, the head heater 30 is heated to a temperature higher than the polarization temperature when the repolarization process is performed. The hot melt ink may be melted while generating heat. In this case, since the piezoelectric element 20 can always be maintained at the polarization temperature, the polarization voltage is only applied to the piezoelectric element 20 by the polarization voltage generating unit 56, and the repolarization processing of the piezoelectric element 20 is performed. Can be implemented. Accordingly, the time required for the head heater 30 to be heated for the repolarization process can be omitted, so that the repolarization process can be completed in a short time.

Further, in the present embodiment, the case where the polarization characteristics are restored to the same as those at the time of the initial polarization by repolarizing with the polarization voltage and the polarization temperature used for the initial polarization has been described. However, the present invention is not limited to this. That is, while keeping the temperature of the piezoelectric element 20 equal to or higher than the ambient temperature and lower than the Curie temperature, the piezoelectric element 20 is reheated by applying a voltage to the first metal thin film 27 and the second metal thin film 28 provided on the piezoelectric element 20. Any configuration may be used as long as it is polarized. Furthermore, in the present embodiment, an example in which the present invention is applied to an inkjet printer head that performs printing with hot melt ink has been described, but the present invention is not limited to this, and a method of printing using a piezoelectric element is used. If so, the present invention can be applied to an ink jet printer head that performs printing with liquid ink.

As described above, according to this embodiment, the eutectic reaction is used for joining the piezoelectric element 20 and the cavity plate 10 and joining the piezoelectric element 20 and the cavity plate 10 to the nozzle member 40. Since the joining is performed by the joining method, the dimensional accuracy of the joining can be kept extremely high in the manufacturing stage of the ink jet printer head 1, and the increase in the flow path resistance due to the deformation of the ink flow path is reliably prevented. Therefore, good ink ejection performance can be exhibited. In addition, since the first metal thin film 27 and the second metal thin film 28 used for the joining by the eutectic reaction are also used as electrodes for repolarization processing, the cavity plate 10 and the piezoelectric element 20 are not disassembled. The repolarization process can be performed at an appropriate timing, and good ink ejection characteristics in the manufacturing stage can be maintained for a long time.

Although the first metal thin film 27, the second metal thin film 28, and the bonding thin film 44 have a structure in which a gold thin film layer is provided on a chromium thin film layer, the present invention is not limited to this. No, a nickel thin film layer is provided on a chromium thin film layer,
Further, a metal thin film may be formed by laminating a gold thin film on a nickel thin film layer.

Further, a metal thin film may be formed by a plating method as well as a method such as sputtering or vapor deposition.

In the case where the repolarization process is performed periodically, the repolarization process may be performed not only at a fixed time but also at a certain number of drive times or at a certain number of recording paper outputs.

(Second Embodiment) Next, a second embodiment of the present invention will be described. Note that the description refers to FIGS. 1 and 2 as in the first embodiment.

In this embodiment, the cavity plate 10 is formed of soda glass having a thermal expansion coefficient close to that of aluminum, and aluminum is formed as the first metal thin film 27 and the second metal thin film 28 of the piezoelectric element 20 by vapor deposition. .

Then, such a cavity plate 1
0 and the piezoelectric element 20 without using an adhesive,
It is joined by a joining method utilizing electrostatic force called anodic joining.

To manufacture such an ink jet printer head 1, first, the first piezoelectric element 2 of the piezoelectric element 20 is formed.
An aluminum layer is formed on the surfaces of the first and fourth piezoelectric bodies 24 by vapor deposition. Then, this aluminum layer is mirror-finished by etching, and finished to a surface roughness of about 0.1 μm.

Next, ink grooves for forming the ink pressure chambers 12 and the ink reservoirs 11 are formed in the cavity plate 10 made of soda glass using a photo-etching technique, and the piezoelectric element 20 and the cavity plate 10 are formed. Are overlapped, sandwiched between electrodes for anodic bonding, and heated until the entire temperature reaches about 400 ° C.
The electrode on the 0 side has a positive potential and the electrode on the cavity plate 10 has a negative potential.
A voltage of 000 V is applied. The current mostly flows initially and decreases after a few minutes, completing the anodic bonding.

According to such a joining method, the cavity plate 10 and the piezoelectric element 2 can be used without using an adhesive.
0 can be firmly joined, and in the manufacturing stage of the inkjet printer head 1, the dimensional accuracy of the joining can be kept extremely high, and the flow path resistance caused by the deformation of the ink flow path can be reduced. Since the increase can be reliably prevented, good ink ejection performance can be exhibited. Moreover, since the first metal thin film 27 and the second metal thin film 28 used for the joining by the eutectic reaction are also used as electrodes for the repolarization process, the cavity plate 10 and the piezoelectric element 20 can be appropriately disassembled without being disassembled. The re-polarization process can be performed at the timing described above, and good ink ejection characteristics in the manufacturing stage can be maintained for a long time.

The metal thin film formed on the piezoelectric element 20 can be made of a metal such as iron or copper in addition to the aluminum film described above. In this case, the cavity plate 10 may be formed of soda glass having a thermal expansion coefficient close to that of iron or copper.

When the cavity plate 10 is made of borosilicate glass, a low-expansion alloy of iron and nickel-silicon (for example, Kovar or Fani) can be used.

In each of the embodiments described above, an example is described in which the piezoelectric element is deformed by a combination of the unimorph mode and the shear mode. However, the present invention is not limited to this. It may be configured to be deformed in combination, or to be deformed in combination of the bimorph mode and the expansion / contraction mode.

Here, the expansion / contraction mode is a mode of deformation that occurs in a polarized piezoelectric material when an electric field is applied in parallel to the polarization direction of the piezoelectric material. This is a mode of deformation caused by expansion and contraction of the piezoelectric body itself.

In the bimorph mode, an electric field is applied to one of the two piezoelectric layers polarized in the same direction in the thickness direction in the direction opposite to the polarization direction. When an electric field is applied to the
The piezoelectric body of the layer bends (the piezoelectric body to which the electric field is applied in the same direction as the polarization direction is deformed so as to contract in the plane direction, and the piezoelectric body to which the electric field is applied in the opposite direction to the polarization direction is in the plane direction). This is a mode of deformation caused by causing deformation caused by deformation such that it is elongated.

[0084]

As described above, according to the ink jet head device of the first aspect, the metal thin film for repolarization processing, which is formed on both surfaces of the piezoelectric element and has at least a surface layer made of gold, Since it has a silicon cavity plate bonded using a metal thin film and a eutectic reaction, bonding with good dimensional accuracy is performed, and the inkjet head device is manufactured with high accuracy overall to improve the ink ejection characteristics. Can be improved. In addition, it is possible to prevent defective bonding and prevent defective operation of the inkjet head device. For example, since there is no shortage of the adhesive, each ink pressure chamber can be reliably separated by the partition of the cavity plate, and malfunctions such as occurrence of crosstalk in ink pressure waves at the time of ink ejection can be prevented. Also, there is no deformation of the ink flow path due to the protrusion of the adhesive, non-uniform printing due to an increase in flow path resistance, a change in the ink ejection direction,
It is possible to prevent operation failure due to clogging of the nozzle hole. Moreover, since the metal thin film used for the bonding by such eutectic reaction is used as an electrode for repolarization processing, it is possible to easily perform the subdivision processing without disassembling the inkjet head device. Such good ink ejection performance in the initial stage of manufacturing can be maintained for a long period of time.

According to the ink jet head device of the second aspect, the gold thin film for repolarization treatment is formed by laminating a gold surface layer film on a chromium thin film formed on both sides of the piezoelectric element. Since it is formed, the adhesion strength between the chromium thin film and the surface layer film made of gold can be improved, and the piezoelectric element and the cavity plate can be firmly joined.

According to the third aspect of the present invention, since the nickel thin film layer is formed between the chromium thin film and the surface layer film made of gold, the piezoelectric element and the cavity plate are further increased. Can be firmly joined.

According to the fourth aspect of the present invention, the metal thin film on the opposite side to the metal thin film used for bonding to the silicon cavity plate is also used as a driving electrode of the piezoelectric element. Therefore, the outermost layer of the piezoelectric element can be deformed in the unimorph mode or the bimorph mode, and the amount of deformation of the piezoelectric element can be increased.

According to the ink jet head device of the fifth aspect, a metal thin film for repolarization treatment, which is formed on both surfaces of the piezoelectric element and has a surface layer made of at least aluminum, and a surface layer made of aluminum of the metal thin film Since it has a glass cavity plate bonded using an anodic reaction, it is possible to perform bonding with good dimensional accuracy and to manufacture the inkjet head device with high accuracy as a whole to improve the ink ejection characteristics. Can be. In addition, it is possible to prevent defective bonding and prevent defective operation of the inkjet head device. For example, since there is no shortage of the adhesive, each ink pressure chamber can be reliably separated by the partition of the cavity plate, and malfunctions such as occurrence of crosstalk in ink pressure waves at the time of ink ejection can be prevented. Further, there is no deformation of the ink flow path due to the protrusion of the adhesive, and it is possible to prevent non-uniform printing due to an increase in flow path resistance, a change in the ink ejection direction, and a malfunction due to a clogged nozzle hole. Moreover, since the aluminum thin film used for the bonding by the anodic reaction is used as an electrode for the repolarization process, the subdivision process can be easily performed without disassembling the inkjet head device. Such good ink ejection performance in the initial stage of manufacturing can be maintained for a long period of time.

According to the ink jet head device of the present invention, the metal thin film having the surface layer made of aluminum and used for bonding to the glass cavity plate, and the metal thin film on the opposite side are formed as follows. Since the piezoelectric element is also used as a driving electrode of the piezoelectric element, the outermost layer of the piezoelectric element can be deformed in the unimorph mode or the bimorph mode, and the amount of deformation of the piezoelectric element can be increased.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an inkjet printer head according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line X-X 'in FIG.

FIG. 3 is a block diagram illustrating a configuration of a control unit used for drive control of the inkjet printer head of FIG. 1;

FIG. 4 is a sectional view showing an operation state of the ink jet printer head of FIG. 2;

FIG. 5 is a flowchart of a repolarization process in the ink jet printer head of FIG. 1;

FIG. 6 is a cross-sectional view illustrating a conventional inkjet head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inkjet printer head 10 Cavity plate 11 Ink reservoir 12 Ink pressure chamber 20 Piezoelectric element 21 First piezoelectric body 22 Second piezoelectric body 23 Third piezoelectric body 24 Fourth piezoelectric body 25 Individual electrode 26 Common electrode 27 First metal thin film 28 2 Metal thin film 30 Head heater 40 Nozzle member

Claims (6)

[Claims] 1. An ink-jet head device for storing ink in an ink pressure chamber provided at a predetermined interval in a cavity plate, and applying a pressure change to the ink by a piezoelectric element to discharge the ink from a nozzle, A metal thin film for repolarization treatment, which is formed on both surfaces of the element and has at least a surface layer made of gold, and a silicon cavity plate bonded to the surface layer made of gold of the metal thin film by using a eutectic reaction. An ink jet head device comprising: 2. The metal thin film for repolarization treatment according to claim 1, wherein a surface layer made of gold is formed on a chromium thin film formed on both surfaces of the piezoelectric element. Ink jet head device. 3. The ink jet head device according to claim 2, wherein a nickel thin film is formed between the chromium thin film and the surface layer film made of gold. 4. The method according to claim 1, wherein the metal thin film on the opposite side to the metal thin film used for bonding to the silicon cavity plate also serves as a driving electrode of the piezoelectric element. Item 4. The inkjet head device according to any one of items 3. 5. An ink jet head device for storing ink in an ink pressure chamber provided at a predetermined interval in a cavity plate, and applying a pressure change to the ink by a piezoelectric element to discharge the ink from a nozzle, A metal thin film for repolarization treatment, which is formed on both surfaces of the element and has a surface film made of at least aluminum, and a glass cavity plate bonded to the surface film made of aluminum of the metal thin film using anodic bonding. An ink jet head device characterized by the above. 6. The device according to claim 5, wherein the metal thin film opposite to the metal thin film used for bonding to the glass cavity plate also serves as a driving electrode of the piezoelectric element. Inkjet head device.