JP2002225269A - Ink-jet printer head and its piezoelectric element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink-jet printer head which solves a problem caused by thickness of a piezoelectric sheet and an electrode, obtains an excellent jet performance by bringing out well a piezoelectric characteristic of the piezoelectric sheet and obtaining full displacement of an active part, and prevents occurrence of defects such as an electrode cut, a laminated layer release and the like, and also to provide its piezoelectric element. SOLUTION: Film thickness of one layer of the piezoelectric sheets 40a to 40f and ceramic layers 71a to 71c is constructed so as to be 5 μm to 40 μm, preferably 15 μm to 30 μm. Film thickness of one layer of common electrodes 42 and individual electrodes 44a to 44c is also constructed so as to be 0.7 μm to 5 μm, preferably 1 μm to 3 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a piezoelectric ink jet printer head and a piezoelectric element used therein.

[0002]

2. Description of the Related Art In an ink jet printer head used for an ink jet printer, a piezoelectric ink jet printer head is known in which a piezoelectric element is provided adjacent to an ink chamber of a cavity plate and ink is ejected from the ink chamber to perform printing. I have.

In this piezoelectric ink jet printer head, a piezoelectric element is formed by alternately laminating a ceramic piezoelectric sheet and an electrode, pressing and firing, and a cavity plate in which an ink chamber is separately formed; Are bonded using an adhesive or the like, and a deformation restricting material is further bonded onto the piezoelectric element. Then, by applying a voltage to the electrodes, the active portion of the piezoelectric sheet sandwiched between the electrodes is displaced, and pressure is applied to the ink in the ink chamber.

[0004]

However, according to the conventional piezoelectric element, when the piezoelectric sheet is thin, the metal of the electrode may be excessively diffused at the time of the sintering, thereby deteriorating the piezoelectric characteristics of the piezoelectric sheet. there were. Conversely, if the piezoelectric sheet is thick, there is a problem that the restraint effect of the inactive portion around the active portion sandwiched between the electrodes becomes strong, and sufficient displacement of the active portion cannot be obtained.

Further, if the electrode is thin, there is a problem that the electrode becomes too thin or cut due to diffusion during firing. Further, when the electrodes are thick, the difference in the thickness of the piezoelectric element after lamination due to the difference between the part where the electrodes are present and the part where the electrodes are not present becomes large, and the problem that the lamination interface in the part where the electrodes do not exist becomes easy to peel off. there were.

The present invention has been made in view of the above problems, and solves a problem based on the thickness of a piezoelectric sheet and an electrode.
Inkjet printer heads and piezoelectric elements that exhibit good piezoelectric properties of piezoelectric sheets, obtain sufficient displacement of active sites to obtain excellent jetting performance, and do not cause problems such as electrode cutout or delamination. provide.

[0007]

In order to solve the above-mentioned problems, the present invention provides a cavity plate having a plurality of ink ejection orifices and a plurality of ink chambers communicating with the respective orifices; A plurality of piezoelectric sheets having a plurality of electrodes formed at positions corresponding to a plurality of piezoelectric sheets, a plate-type piezoelectric element integrally formed by laminating and sintering, the piezoelectric element, the cavity plate, the cavity plate, the The plurality of piezoelectric sheets are attached so as to cover a plurality of ink chambers, and each of the plurality of piezoelectric sheets has a thickness of 5 μm to 40 μm.
Is set to

According to this, each piezoelectric sheet has a thickness of 5 μm.
With the above, the metal of the electrode is not excessively diffused during firing, and good piezoelectric characteristics are maintained. Further, by setting the thickness to 40 μm or less, the influence of the constraint of the inactive portion around the active site is not too strong, and a sufficient displacement of the active site can be obtained. Therefore, by applying a voltage to the electrodes, the deformation characteristics of the piezoelectric sheet in the portion corresponding to each ink chamber become uniform and stable, and stable ejection characteristics can be obtained for each ink chamber.

Preferably, each of the plurality of piezoelectric sheets has a thickness of 15 μm to 30 μm. As a result, the degradation of the piezoelectric properties due to the diffusion of the metal in the electrode layer during firing is extremely well prevented, the influence of the constraint of the inactive part around the active part is suppressed very well, and the sufficient displacement of the active part is suppressed. can get.

Preferably, the electrode has a thickness of 0.7.
It is set to μm to 5 μm. More preferably, in this case, the electrodes include a plurality of individual electrodes formed at positions facing the respective ink chambers, and a common electrode formed over the plurality of ink chambers, and each of the individual electrodes has a width of 5
It is set to 0 μm to 500 μm.

As a result, it is possible to prevent the electrode from becoming too thin or being cut due to diffusion during firing. Further, in the laminated piezoelectric element, the difference in the thickness of the piezoelectric element based on the difference between the part where the electrode exists and the part where the electrode does not exist does not become too large, and the separation of the lamination interface in the part where the electrode does not exist is good. Is prevented. An efficient inkjet head can be made in terms of performance and production.

More preferably, the electrode has a thickness of 1 μm.
m to 3 μm. The electrodes include a plurality of individual electrodes formed at positions facing the respective ink chambers and a common electrode formed over the plurality of ink chambers, and the width of each individual electrode is set to 80 μm to 200 μm. You. As a result, it is possible to more reliably prevent the electrodes from becoming too thin or being cut due to diffusion during firing. Further, in the piezoelectric element after lamination, the difference in the thickness of the piezoelectric element based on the difference between the part where the electrode exists and the part where the electrode does not exist does not become too large, and the lamination interface at the part where the electrode does not exist is further removed. It is surely prevented. It is possible to produce an ink jet head that is more efficient in terms of performance and production.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an ink jet printer head and its piezoelectric element according to the present invention will be described with reference to FIGS.
This will be described in detail with reference to FIG.

FIG. 7 is a diagram showing a main part of the ink jet printer 1. As shown in FIG. The platen 10 is provided horizontally orthogonal to the transport direction of the paper 11. The platen 10 includes a shaft 12 and is rotatably supported by a frame 13.
It is driven by a motor 14 via a drive gear train. An ink jet printer head 15 is provided at a position facing the platen 10.

This ink jet printer head 15
Are arranged on the carriage 18 together with the ink supply device 16. The carriage 18 is provided on the shaft 1 of the platen 10.
Two guide rods 20 arranged parallel to the two axes
a, 20b (hereinafter collectively referred to as guide rods 20)
And a timing belt 24 wound around a pair of driven pulleys 21 and 22. When the drive pulley 22 is driven by the motor 23 and the timing belt 24 is fed in a predetermined direction, the carriage 18 is moved along the guide rod 20 and moves with the inkjet printer head 15 facing the platen 10. Is done.

FIG. 1 shows an ink jet printer head 1.
It is principal part sectional drawing of No. 5. The head 15 includes a cavity plate 30 and the piezoelectric element 3. As shown in FIG. 6, the cavity plate 30 has ink chambers 32a, 32b, and 32c (hereinafter referred to as ink chambers, which are open spaces) inside an ink chamber body 34 formed entirely in a rectangular parallelepiped. 32) is a partition wall 34.
A plurality, three in the figure, are separated by a. Each ink chamber 32 has an internal width of about 250 μm and a height of 60 μm.
It is composed of At the bottom of the ink chamber main body 34, an orifice plate 36 having orifices 37a, 37b, 37c (hereinafter, referred to as the orifice 37 unless otherwise distinguished) for ejecting ink corresponding to each of the ink chambers 32a to 32c has a lid shape. Be placed. Then, the ink chamber main body 34
And the orifice plate 36 are made of an iron-based material,
It is integrated by bonding. It should be noted that it may be integrally formed by firing with ceramics or the like, or may be integrally formed by injection using an alumina-based material or the like.
Each of the ink chambers 32 is supplied with ink from a supply path (not shown) communicated from the ink supply device 16 (see FIG. 7), and is always filled with ink.

The ink stored in the ink chamber 32 is set so that a predetermined negative pressure is applied. Therefore, the ink forms a concave meniscus outward at the orifice 37 due to surface tension. Therefore, usually the orifice 3
Although no ink leaks from the nozzle 7, the ink is ejected from the orifice 37 only when the internal pressure increases. Also, as in the present embodiment, the orifice 3 is directly in the ink chamber 32.
In addition to the ink chamber 32, an orifice 37 is provided by further providing an ink outlet path from the ink chamber 32, and the ejection direction and the like are adjusted, and the orifice 37 is arranged other than at the bottom of the ink chamber 32. Is also good.

The piezoelectric element 3 includes an active layer 38 provided above the cavity plate 30 so as to apply pressure to the ink in the ink chambers 32, and a displacement of the active layer 38 to the side opposite to the cavity plate 30. Layer 70 that restrains
Consists of The active layer 38 includes piezoelectric sheets 40 a and 40 made of a piezoelectric ceramic having an electrode pattern formed on a surface thereof.
b, 40c, 40d, 40e, and 40f (hereinafter, referred to as a piezoelectric sheet 40 unless otherwise specified) are laminated, and the constraining layer 70 is formed of the ceramic layers 71a, 7a.
1b and 71c (hereinafter, referred to as a ceramics layer 71 unless otherwise specified) are laminated. The constraining layer 70 is fired integrally with the active layer 38 as described later, and increases the rigidity of the entire piezoelectric element 3 to prevent crosstalk.

The piezoelectric sheet 40 constituting the active layer 38
It is formed by forming a piezoelectric ceramic having an electrostrictive effect on a thin sheet. Every other piezoelectric sheet 40
As shown in FIG. 5, on the upper surfaces of the a, 40c, and 40e, an internal negative electrode layer, that is, a common electrode 42 that covers the entirety of the piezoelectric sheet except for the peripheral edge thereof, and this electrode is electrically connected to the outside. Electrode take-out part 43 is formed as described later. Then, the piezoelectric sheets 40a, 40c, 40
e and the piezoelectric sheets 40b, 40d, 40f alternately positioned
Are arranged in parallel to the ink chambers 32a to 32c so as to correspond to the ink chambers 32a to 32c in parallel, and the width of the ink chamber 32 in the width direction is about 120 μm. Individual electrodes 44a, 44b, 44c
Then, electrode extraction portions 45a, 45b, 45c for electrically connecting the electrodes to the outside are formed.

In this embodiment, the common electrode 42 and the individual electrodes 44a to 44c are made of an Ag-Pd metal material and have a thickness of 0.7 μm to 5 μm, preferably 1 μm.
３3 μm.

A plurality of piezoelectric sheets 40 on which these two types of electrode patterns are printed are alternately stacked. Each of the laminated piezoelectric sheets 40 is located between the common electrode 42 and the individual electrodes 44a to 44c as shown in FIG. Further, since the individual electrodes 44a to 44c are formed in a strip shape, the common electrode 42 and the individual electrodes 44a to 44c are formed in each piezoelectric sheet 40 as shown in the upper part of FIG.
44c, the piezoelectric active portions 46a, 46b, and 46c each having a width of about 120 μm, and the piezoelectric inactive portion 48 not sandwiched between the common electrode 42 and the individual electrodes 44a to 44c. In other words, a portion in the piezoelectric sheet 40 where an electric field is generated when a voltage is applied between the common electrode and the individual electrode and is deformed in the vertical direction due to the electrostriction effect, and a portion where the electric field is not generated even when the voltage is applied Can be done. The active layer 38 is fixed to the ink chamber main body 34 such that the piezoelectric active sections 46a to 46c face the ink chambers 32a, 32b, and 32c, and the piezoelectric inactive section 48 faces the partition 34a between the ink chambers. ing.

The constraining layer 70 is composed of the ceramic layers 71a, 71
1b and 71c. The ceramic layer 71
The active layer 38 has the same configuration, material, and size as the piezoelectric sheet 40. Further, the ceramic layer 71 of the constraining layer 70
a, 71c are the piezoelectric sheets 40b, 40 of the active layer 38;
d and 40f are provided with dummy individual electrodes 73a, 73b and 73c having the same configuration as the individual electrodes 44a, 44b and 44c and the electrode extraction portions 45a, 45b and 45c, and the electrode extraction portions 75a, 75b and 75c shown in FIG. The ceramic layer 71b of the constraining layer 70 includes a dummy common electrode 72 having the same configuration as the common electrode 42 and the electrode extraction portion 43 of the piezoelectric sheets 40a, 40c, and 40e of the active layer 38, and FIG.
Are provided. Here, the piezoelectric sheet 40 on which the electrodes and the like are printed as described above, and the green sheets 50 and 51 serving as the ceramic layer 71 can be shared as common components. However, after the piezoelectric element 3 is formed, the location where the piezoelectric element 3 is arranged and the electrical wiring are different as will be described later, and the function is different, so the name is different.

The active layer 38 and the constraining layer 70 are manufactured by the following manufacturing method. First, ferroelectric lead zirconate titanate (PZT (PbTiO ₃ .PbZrO)
₃ )) A mixed solution having a viscosity of 10,000 to 30,000 CPS is prepared by mixing a ceramic powder, a binder, and a solvent of a system, spread on a plastic film such as PET (polyethylene terephthalate), dried, and dried. To form a green sheet. In the present embodiment, the thickness of the green sheet is set to 5 μm to 40 μm, preferably 15 μm to 30 μm.

Further, five of these green sheets 5
0 indicates the individual electrodes 44a, 44b, 44c and the electrode extraction portions 45a, 45b, 45c or the dummy individual electrodes 73a, 73b, 73c and the electrode extraction portion 75 on the sheet.
A metal material is screen-printed on portions to be a, 75b, and 75c. Similarly, on the remaining four green sheets 51, a metal material is printed on portions that become the common electrode 42 and the electrode extraction portion 43 or the dummy common electrode 72 and the electrode extraction portion 74.

The two kinds of green sheets 5
Nine green sheets 50 are alternately stacked at the bottom of 0 and 51. When the green sheets 50 and 51 are stacked in this manner, the green sheets 50 are arranged so as to be at the upper and lower ends. As a result, as active layers and constraining layers, five green sheets 50 and four green sheets 51 having different names but having exactly the same structure are alternately laminated, that is, nine green sheets 50 in total. At this stage, there is no distinction between the active layer 38 and the constraining layer 70. In this embodiment, the individual electrodes are arranged on the lowermost sheet, but the common electrodes may be arranged on the lowermost sheet.

Next, the nine green sheets 50 and 51 constructed as described above are stacked, and the whole is heated and pressed, degreased, and then sintered, so that the active layer 38 and the constraining layer 70 are integrated. Obtain a block of piezoelectric ceramics.

The case where the block in which the green sheets 50 and 51 are laminated is fired will be described. Piezoelectric element 3
Is composed of the active layer 38 and the constraining layer 70 as described above, but the active layer 38 has a configuration in which an electrode is indispensable. On the other hand, it is not necessary to provide an electrode in the constraining layer 70 functionally. However, when firing the block in which the green sheets 50 and 51 are stacked, the shrinkage ratio when firing is different between the piezoelectric ceramic and the metal material constituting the electrode. If the shrinkage is slightly different, the active layer 38 warps or undulates after firing, thereby impairing its planarity. When the planarity of the active layer 38 is impaired, the degree of adhesion is reduced when the active layer 38 is closely adhered to the cavity plate 30, causing leakage of ink from the ink chamber 30 to cause defective products, or The need for re-polishing increases the man-hours and production costs, and the filling with a filler causes problems such as a decrease in strength.

Therefore, in the piezoelectric element 3, the constraining layer 70 is made of the same piezoelectric ceramic material as the active layer 38 as described above. In addition, the constraining layer 70 includes a common electrode 42, an electrode extraction portion 43, and individual electrodes 44a, 44b, 44c provided on the piezoelectric sheet 40 of the active layer 38.
The same electrode extraction portions 45a, 45b, and 45c (hereinafter, abbreviated as electrodes) are replaced with dummy common electrodes 72, electrode extraction portions 74, dummy individual electrodes 73a, 73b, 73c that do not contribute to the driving deformation of the piezoelectric sheet 70, and electrode extraction. Part 7
5a, 75b and 75c (hereinafter abbreviated as dummy electrodes) are formed. For this reason, since the active layer 38 and the constraining layer 70 have exactly the same configuration, the shrinkage ratio during firing can be the same. Further, in the entirety of the combined active layer 38 and constraining layer 70, the arrangement of the electrodes and the dummy electrodes is
By being symmetrical in the thickness direction (laminating direction), the overall shrinkage ratio is made symmetrical, so that warpage does not occur during firing.

Here, FIG. 2 is a schematic diagram showing the electrical connection of the piezoelectric element 3. On the side surface of the piezoelectric element 3, electrode extraction portions 43 of the piezoelectric sheets 40a, 40c, and 40e;
An external negative electrode 52a made of a conductive metal material for electrically connecting the ceramic layer 71b to the electrode lead-out portion 74 is arranged, and the ceramic layers 71a, 7
An external negative electrode 52b made of a conductive metal plate for electrically connecting each of the electrode extraction portions 75a, 75b, and 75c of 1c is arranged, and the external negative electrode 52a and the external negative electrode 52b are electrically connected. Connected. Therefore, the ceramic layers 71a, 71b, 71c, 40a,
The electrodes 40c and 40e or the dummy electrodes have the same potential.

On the other hand, the piezoelectric sheets 40b, 40d, 40f
An external positive electrode 54a made of a conductive metal material for electrically connecting the respective electrode extraction portions 45a, 45a, 45a is arranged on the side surface of the piezoelectric element 3. Similarly, the external positive electrode 5 made of a conductive metal material for electrically connecting the respective electrode extraction portions 45b, 45b, 45b of the piezoelectric sheets 40b, 40d, 40f.
4b, an external positive electrode 5 made of a conductive metal material for electrically connecting the respective electrode extraction portions 45c, 45c, 45c of the piezoelectric sheets 40b, 40d, 40f.
4c are arranged on the side surfaces of the piezoelectric element 3, respectively. In addition,
These external electrodes are formed by directly printing or applying a metal material on the side surfaces of the active layer 38 and the constraining layer 70.
Separately, electrodes may be formed on a metal plate and connected by abutment, or wires may be connected by soldering,
Various configurations are possible.

Here, regarding the dummy electrode, the constraining layer 7
Since it does not contribute to the driving deformation of the ceramic layer 71 of 0, there is no need to apply a driving voltage. However, even when the dummy electrode is in an electrically non-polarized insulating state, a potential difference may be generated between the dummy electrode and the common electrode 42 on the uppermost layer of the active layer 38, thereby generating a capacitance. Since this current is small, it does not contribute to the driving deformation of the ceramics layer 71, but causes a power loss, so that there is a disadvantage that the use time is shortened particularly when a battery is used as a power supply. Therefore, in the constraining layer 70, the dummy electrode is electrically connected to the common electrode 42 formed on the active layer 38. Then, the dummy electrode of the constraining layer 70 and the active layer 38
No potential difference is generated between the common electrode 42 and the uppermost layer and unnecessary capacitance can be prevented from being generated.

The block of the piezoelectric element constructed as described above is immersed in an oil bath (not shown) filled with an insulating oil such as silicone oil at about 130 ° C., and its external negative electrode 52 and external positive electrodes 54a to 54c. 2.5k between
An electric field of about v / mm is applied to perform polarization processing on each piezoelectric sheet 40 of the active layer 38. As a result, the piezoelectric active portions 46a, 46b, 46c of each piezoelectric sheet have electrostrictive characteristics as is well known.

Further, as shown in FIG.
a is grounded by a cord (not shown) and is set to the ground potential. The external positive electrode 54a is provided with an open / close switch 62.
A is connected to the positive electrode of the drive power supply 60 via a. Similarly, the external positive electrode 54b is connected to the open / close switch 6
It is connected to the positive electrode of the drive power supply 60 via a cable (not shown) via 2b. The external positive electrode 54c is connected to the positive electrode of the drive power supply 60 via an open / close switch 62c with a cord (not shown). Note that the negative electrode of the driving power supply 63 is set to the ground, that is, the ground potential.

The head 15 is formed by bonding the piezoelectric element 3 thus obtained to the cavity plate 30 as shown in FIG.

Here, a modified example of the piezoelectric element 3 will be described. FIG. 8 shows a piezoelectric element 20 which is a modification of the piezoelectric element 3.
FIG. Note that members having the same configuration as the piezoelectric element 3 are denoted by the same reference numerals, and description thereof will be omitted.
The same applies to the following modifications. Piezoelectric element 203
Is formed from the active layer 238 and the constraining layer 270, as in the piezoelectric element 3. The active layer 238 includes four layers of the piezoelectric sheet 40. In addition, the constraining layer 270 is formed by laminating only five ceramic layers 71 each having a dummy common electrode 72, and each of the dummy common electrodes 72 is grounded to a ground electrode. Active layer 3 of piezoelectric element 3
As shown in FIG. 1, the active layer 238 of the piezoelectric element 203 has four layers.
The difference is that the piezoelectric sheet 40 is composed of layers. As shown in FIG. 5, the constraining layer 70 constituting the piezoelectric element 3 is formed by alternately laminating three green sheets 50 and green sheets 51 and firing. In the layer 270, five green sheets 51 alone are laminated and fired to form a ceramic layer 71 shown in FIG.
And the dummy electrode 72 is formed. As shown in the piezoelectric element 203, the numbers of the piezoelectric sheets 40 and the ceramic layers 71 laminated as the active layer 238 and the constraining layer 270 can be changed according to various conditions. In addition, if the shrinkage ratio of the electrode provided as a dummy electrode during firing is within a certain range for preventing warpage, a part or the entirety of the constraining layer 70 can be constituted only by the green sheet 51. .

Next, another modified example of the piezoelectric element 3 will be described. FIG. 9 is a view showing a piezoelectric element 303 which is another modified example of the piezoelectric element 3. Like the piezoelectric element 203, the piezoelectric element 303 includes the piezoelectric sheet 40 in which the active layer 338 has four layers. Further, the constraining layer 370 is formed by laminating and firing only five green sheets 50 each having the dummy individual electrode 73a, 73b, 73c, and each of them is connected to the ground potential. As in the case of the above-described piezoelectric element 203, if the shrinkage rate of the dummy positive electrode during firing is within a certain range for preventing warpage, the constraining layer 370 is replaced with the green sheet 5.
It is also possible to configure using only 0.

The operation of the piezoelectric element 3 of the piezoelectric ink jet printer head 15 configured as described above will be described with reference to FIGS. In accordance with predetermined print data, the controller operates the open / close switches 62a, 62
When any one of the b and 62c, for example, the open / close switch 62a is closed, the common electrode 42 in the range of the piezoelectric active portion 46a is opened.
A voltage is applied between the electrode and the individual electrode 44a, an electric field is generated in the piezoelectric sheet 40 located in the range, and the piezoelectric material of the piezoelectric active portion 46a expands in the vertical direction in FIG. At this time, the ceramic layer 71 of the constraining layer 70
Since no electric field is generated at a, 71b and 71c, there is no expansion or contraction. Therefore, in the active layer 38, the internal electrodes 4
The piezoelectric active portion 46a sandwiched between the ink chambers 3a and 4a
2a, reducing the volume of the ink chamber 32a. Then, the ink in the ink chamber 32a is ejected as droplets 39 from the orifice 37a. When the open / close switch 62a is opened and the application of the voltage is interrupted and the piezoelectric active portion 46a is returned to the original position, the ink is replenished from the ink supply device 16 with the increase in the volume of the ink chamber 32a.

The deformation of the active layer 38 in the piezoelectric active portion 46a occurs equally up and down if the constraining layer 70 is not provided. On the other hand, the constraining layer 70
Is provided, the deformation generated in the piezoelectric active portion 46a is mainly caused by the ink chamber 3 which is on the opposite side of the constraint layer 70.
2a side is deformed. Therefore, when the deformation amount generated in the piezoelectric active portion 46a is the same, the deformation of the ink chamber 32a side is larger in the piezoelectric element 3 having the constraining layer 70 than in the structure without the constraining layer 70. Can be
The ink ejection amount can be increased. That is, even if the same voltage is applied, the ink ejection amount can be increased by providing the constraining layer 70. In other words, when it is desired to eject a predetermined amount of ink, the applied voltage can be reduced, so that the power consumption can be reduced.

In this embodiment, as described above, the piezoelectric sheets 40 on which the electrodes and the like are printed and the green sheets 50 and 51 serving as the ceramic layers 71 are
Since its thickness is set to 5 μm to 40 μm,
Good piezoelectric characteristics can be obtained, and sufficient displacement can be obtained in the active layer 38. The relationship between the thickness of the green sheet and the piezoelectric characteristics and the displacement of the active layer will be described with reference to FIG.

FIG. 3 shows the thickness of one ceramic layer,
4 is a graph showing a relationship between a piezoelectric constant and a displacement amount. FIG.
As shown in FIG.
In the case of above, the piezoelectric constant _{d 33} is 600 (× 10
⁻¹² m / V) or more, indicating that good characteristics can be obtained.

However, the thickness of one ceramic layer is 5
If it is less than μm, the piezoelectric constant _{d 3 3} is 450 (× 1
^0-12 m / V), which indicates that sufficient characteristics cannot be obtained. It is considered that when the film thickness is less than 5 μm, Ag in the electrode is excessively diffused at the time of firing, so that sufficient piezoelectric characteristics cannot be obtained as described above. Therefore, in the present embodiment, the thickness of one layer of the ceramic layer is set to 5 μm or more, preferably 15 μm or more. Therefore, in the present embodiment, sufficient piezoelectric characteristics can be obtained in active layer 38.

On the other hand, as shown in FIG. 3, when the thickness of one of the ceramic layers is
It can be seen that a displacement of 20 nm or more can be obtained in the above.
The displacement shown in FIG. 3 indicates the displacement when a voltage of 20 V is applied to five ceramic layers of the active layer 38. However, when the thickness of one ceramic layer exceeds 40 μm, the active layer 38
It can be seen that the displacement amount is 3 nm or less, and a sufficient displacement cannot be obtained.

This is because the thickness of one of the ceramic layers is
If the thickness exceeds 40 μm, it is considered that the effect of the constraint of the piezoelectric inactive portion around the piezoelectric active portion becomes large, and a sufficient displacement cannot be obtained in the piezoelectric active portion.

Therefore, in this embodiment, the thickness of one ceramic layer is set to 40 μm or less, preferably,
It was configured to be 30 μm or less. As a result, in the active layer 38 of the present embodiment, a sufficient displacement can be obtained.

In the present embodiment, as described above, the common electrode 42 made of an Ag-Pd-based metal material is used.
And the individual electrodes 44a to 44c have a thickness of 0.7 μm to 5 μm.
m, preferably 1 μm to 3 μm,
There is no problem that the electrode becomes too thin or the electrode breaks, and the difference in the thickness of the piezoelectric element between the part where the internal electrode exists and the part where the internal electrode does not exist is small. Less likely to occur. The relationship between the thickness of the electrode, the thickness of the electrode, and the separation at the lamination interface will be described with reference to FIG.

FIG. 4 is a graph showing the relationship between the thickness of the internal electrode, the capacitance, and the separation at the lamination interface. As shown in FIG. 4, when the thickness of the internal electrode is 1 μm or more,
It can be seen that a capacitance of 1600 pF was obtained and an electrode having a sufficient thickness was formed. However, when the film thickness of the internal electrode is less than 0.
When it is less than 7 μm, the capacitance is less than 1500 pF, and it can be seen that the electrode is thin. Further, when the thickness of the internal electrode is 0.5 μm or less, the capacitance is 5
It is less than 00 pF, and it can be seen that electrode breakage occurs.
This is because when the thickness of the internal electrode is less than 0.7 μm,
It is considered that since the Ag in the electrode diffuses during firing, the electrode becomes too thin or the electrode breaks. Therefore, in the present embodiment, the thickness of the internal electrode is configured to be 0.7 μm or more, preferably 1 μm or more. Therefore, in the present embodiment, an electrode having a sufficient thickness can be formed by the common electrode 42 and the individual electrodes 44a to 44c.

On the other hand, as shown in FIG. 4, when the thickness of the internal electrode exceeds 5 μm, it can be seen that peeling frequently occurs at the lamination interface at a portion where the internal electrode does not exist. This is because when the thickness of the internal electrode exceeds 5 μm, the difference in thickness of the piezoelectric element 3 between the portion where the internal electrode exists and the portion where the internal electrode does not exist becomes too large. Can be Therefore, in the present embodiment, the thickness of the internal electrode is configured to be 5 μm or less, preferably 3 μm or less. As a result, separation at the lamination interface can be prevented.

Further, the width of the individual electrodes 44a to 44c formed on the piezoelectric sheet is affected by the pitch between adjacent ink chambers, and is determined by the width of the ink chamber. It is desirable that the width of the individual electrode is 40% to 70% of the width of the ink chamber. If it is smaller than 40%, a sufficient pressure change with respect to the volume of the ink chamber cannot be obtained, and the ejection state of the ink droplets tends to vary. Conversely, 7
If it is larger than 0%, the distance between the ink chambers and the partition wall 34a becomes narrow, and the displacement of the piezoelectric ceramics is restrained.
Not only do not contribute to the increase in pressure, but in some cases,
There is a possibility that a change in pressure of an adjacent ink chamber is affected (crosstalk).

Further, from the viewpoint of head design, the pitch between adjacent ink chambers (head resolution) is 85 μm (300 dpi) in view of the balance between high integration and productivity.
８847 μm (30 dpi), preferably 169 μm
(150 dpi) to 508 μm (50 dpi). At a narrow pitch of 85 μm or less, the width of the partition wall 34a becomes about 10 to 20 μm, and it becomes impossible to secure a sufficient bonding portion with the piezoelectric element in production. Conversely, 8
At a wide pitch of 47 μm or more, the number of scans to obtain the required print quality becomes large, and the performance as a printing device cannot be secured.

Based on the head resolution, the width of the partition wall 34a between the ink chambers, the pressure generation efficiency, and the like are taken into consideration.
When designing an efficient head for performance and production,
The width of the individual electrode is 50 μm to 500 μm, preferably 8 μm.
It needs to be 0 μm to 200 μm. in addition,
When an electrode (in this case, an Ag-Pd-based metal material) is formed on a piezoelectric sheet, it is usually formed by kneading the metal material with a binder or a solvent to form a paste, and using a method such as screen printing. However, in such a printing method, it is extremely difficult to stably form a sheet with a width of 50 μm or less, and it is desirable to design the sheet with a width of 80 μm or more.

As described above, in the present embodiment,
Since the thickness of one layer of the ceramic layer is configured to be 5 μm to 40 μm, preferably 15 μm to 30 μm, good piezoelectric characteristics and displacement can be obtained in the active layer 38 and the ejection characteristics in each ink chamber are also stable. Thus, it is possible to prevent a variation in the ejection characteristics of each ink chamber. Further, the thickness of the internal electrode is set to 0.7 μm to 5 μm.
m, preferably 1 μm to 3 μm, it is possible to prevent physical defects caused by the electrode layer and obtain the original piezoelectric material characteristics.

In the above-described embodiment, an example has been described in which the present invention is applied to a piezoelectric element that operates in the extension mode. However, the present invention is not limited to such a configuration, and the present invention is not limited to such a configuration. The present invention can be applied to a piezoelectric element in either the mode or the share mode.

[0053]

As described above, according to the present invention, the thickness of each piezoelectric sheet constituting a plurality of laminated sintered bodies is set to 5 μm to 40 μm, preferably 15 μm to 30 μm. In addition, during firing, the metal of the electrode is not excessively diffused, and good piezoelectric characteristics are maintained. In addition, the influence of the constraint of the piezoelectric inactive portion around the active site is not too strong, sufficient displacement of the active site can be obtained, and excellent ink droplet ejection performance can be exhibited.

The thickness of the electrode is 0.7 μm to 5 μm.
m, the width is 50 μm to 500 μm, more preferably the thickness is 1 μm to 3 μm, and the width is 80 μm to 200 μm, so that the difference in the thickness of the piezoelectric element based on the difference in the presence or absence of the electrodes can be too large. Without, it is possible to reliably prevent peeling of the lamination interface at a portion where no electrode is present,
Further, an efficient ink jet head can be manufactured in terms of performance and production.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a piezoelectric ink jet printer head according to an embodiment of the present invention.

FIG. 2 is a diagram showing an electrical connection of a piezoelectric element in the piezoelectric ink jet printer head of FIG.

3 is a diagram showing a relationship between the thickness of one ceramic layer in a piezoelectric element in the piezoelectric ink jet printer head of FIG. 1, and a piezoelectric constant and a displacement amount.

FIG. 4 is a diagram showing the relationship between the film thickness of an internal electrode in a piezoelectric element in the piezoelectric ink jet printer head of FIG. 1, the capacitance, and the separation at the lamination interface.

FIG. 5 is an exploded perspective view showing a structure of an active layer and a constraining layer in a piezoelectric element in the piezoelectric ink jet printer head of FIG.

FIG. 6 is an exploded perspective view showing a main part of the piezoelectric inkjet printer head of FIG. 1;

FIG. 7 is a perspective view showing a main part of an ink jet printer using the piezoelectric ink jet printer head of FIG. 1;

FIG. 8 is a sectional view showing a modification of the piezoelectric element in the piezoelectric ink jet printer head of FIG.

FIG. 9 is a sectional view showing another modification of the piezoelectric element in the piezoelectric ink jet printer head of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ink-jet printer 3, 203, 303 Piezoelectric element 30 Cavity plate 32, 32a, 32b, 32c Ink chamber 34 Ink chamber main body 36 Orifice plate 37, 37a, 37b, 37c Orifice 38 Active layer 40 Piezoelectric sheet 42 Electrode 44, 44a, 44b , 44c Individual electrodes 46, 46a, 46b, 46c Piezoelectric active part 48 Piezoelectric inactive part 50, 51 Green sheet 70 Constraining layer 71, 71a, 71b, 71c Ceramic layer

Claims (10)

[Claims] A cavity plate having a plurality of ink ejection orifices and a plurality of ink chambers communicating with the respective orifices; and a piezoelectric sheet having a plurality of electrodes formed at positions corresponding to the plurality of ink chambers. A plurality of sheets, a plate-type piezoelectric element integrally formed by sintering and laminating, and the piezoelectric element is attached to the cavity plate so as to cover the plurality of ink chambers; , Each thickness is 5 μm ~
An ink jet printer head, which is set to 40 μm. 2. The ink jet printer head according to claim 1, wherein each of the plurality of piezoelectric sheets has a thickness of 15 μm to 30 μm. 3. The ink jet printer head according to claim 1, wherein said electrode has a thickness of 0.7 μm to 5 μm. 4. The electrode comprises a plurality of individual electrodes formed at positions facing the respective ink chambers, and a common electrode formed over the plurality of ink chambers, wherein the width of each individual electrode is 50 μm. 4. The ink jet printer head according to claim 3, wherein the thickness is set to about 500 [mu] m. 5. The ink jet printer head according to claim 3, wherein said electrode has a thickness of 1 μm to 3 μm. 6. The electrode comprises a plurality of individual electrodes formed at positions facing the respective ink chambers, and a common electrode formed over the plurality of ink chambers, wherein the width of each of the individual electrodes is 80 μm. The ink jet printer head according to claim 5, wherein the thickness is set to ~ 200 m. 7. A plate-type piezoelectric element mounted on a cavity plate having a plurality of orifices and a plurality of ink chambers communicating with the respective orifices so as to cover the plurality of ink chambers. A plurality of piezoelectric sheets having a plurality of individual electrodes at opposing positions and a plurality of piezoelectric sheets having a common electrode formed over the plurality of ink chambers are alternately stacked and sintered to be integrally formed, The thickness of each piezoelectric sheet is 5 μm to 4 μm.
A piezoelectric element characterized by being set to 0 μm. 8. The piezoelectric element according to claim 7, wherein the thickness of each of the plurality of piezoelectric sheets is set to 15 μm to 30 μm. 9. The piezoelectric element according to claim 7, wherein the thickness of the electrode is set to 0.7 μm to 5 μm. 10. The piezoelectric element according to claim 9, wherein said electrode has a thickness of 1 μm or more and 3 μm or less.