JP2000117968A - Ink jet head device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet head device which is free from the possibilities that a positive and a negative electrode pattern might be shortcircuited. SOLUTION: A piezoelectric element 17 is formed by (A) laminating a top layer 15a, a first layer 19b, a second layer 19c, a third layer 19d, a fourth layer 19e and a bottom layer 19f. In addition, (B) a common electrode is provided on the top layer 19a and an electrode pattern 18a of negative electrodes is formed on the first layer 19b, the third layer 19d and the bottom layer 19f and (C) an electrode pattern 18b of positive electrodes is formed on the second layer 19c and the fourth layer 19e. Further, the electrode pattern 18b of positive electrodes and the electrode pattern 18a of negative electrodes are arranged in such a way that their respective positions coincide with each other in a direction where piezoelectric bodies are laminated. Besides, the electrode pattern 18b of positive electrodes and the electrode pattern 18a of negative electrodes are arranged in such a manner that these patterns are alternately spaced as specified in the face direction of each of the layers.

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 using a laminated piezoelectric element.

[0002]

2. Description of the Related Art An ink jet head used in a conventional ink jet printer is constituted by a ceramic cavity plate having an ink pressure chamber partitioned by a plurality of partitions, and a piezoelectric element joined to the cavity plate. In addition, pressure fluctuations are generated in the ink pressure chamber by the piezoelectric element, and ink in the ink pressure chamber is discharged from nozzles formed in the cavity plate.

[0003] Various types of piezoelectric elements are used. One example is a laminated piezoelectric element. This laminated type piezoelectric element screen-prints positive and negative electrode patterns alternately arranged with a predetermined interval on a piezoelectric member formed in a sheet shape, and further superimposes the piezoelectric member on this electrode, Thereafter, the piezoelectric member and the electrode are laminated in the same manner, then subjected to a binder removal / sintering process, and then provided with a plurality of cutout recesses so as to make the deformed portions of the piezoelectric element independent from each other.

[0004] With such a configuration, a plurality of displacement portions of the piezoelectric element can be made to correspond to each of the plurality of ink pressure chambers, and good ink ejection can be performed for each ink pressure chamber.

[0005]

However, when the positive and negative electrode patterns are formed on the piezoelectric member by screen printing as in the prior art, since the interval between the electrode patterns is short, for example, about 100 μm, the printing accuracy is low. In some cases, there is a high possibility that the positive electrode pattern and the negative electrode pattern are short-circuited, so that the piezoelectric element cannot be displaced normally.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an ink jet head device in which there is no possibility of a short circuit between positive and negative electrode patterns.

[0007]

According to a first aspect of the present invention, there is provided an ink jet head device for ejecting an ink by applying a pressure change to ink stored in an ink pressure chamber. A head device, comprising: a piezoelectric layer stacked in two or more layers and polarized in a stacking direction; positive and negative electrodes formed between the piezoelectric layers; and a positive electrode on the same surface of the piezoelectric layer. Alternatively, only one of the negative electrodes is arranged at a predetermined interval, and the positive electrode and the negative electrode are alternately formed in the laminating direction so as to have a predetermined interval from each other in the direction of the arrangement, and the positive electrode And deformation by an electric field orthogonal to the direction of the polarization based on the application of a voltage to the negative electrode.

According to the first aspect of the invention, only one of the positive and negative electrodes is arranged at a predetermined interval on the same surface of the piezoelectric layer. Even if accuracy varies,
Does not cause a short circuit between the positive electrode and the negative electrode. Moreover,
When viewed in the lamination direction, the positive electrode and the negative electrode are alternately formed so as to have a predetermined interval from each other in the direction of arrangement of the electrodes in each piezoelectric layer, so that a positive voltage is applied to the positive electrode. By applying a negative voltage to the negative electrode, an electric field is generated in a direction perpendicular to the direction of polarization of the piezoelectric body. As a result, the piezoelectric body is deformed by the shear mode.

According to a second aspect of the present invention, in order to solve the above-mentioned problem, in the inkjet head device according to the first aspect, the surface of the uppermost layer or the lowermost layer of the piezoelectric layer is positive or negative. A negative common electrode is provided.

According to the ink jet head device of the present invention, since the positive or negative common electrode is provided on the surface of the uppermost layer or the lowermost layer of the piezoelectric layer, it is different from the common electrode. Among the piezoelectric layers provided with polar electrodes, the piezoelectric layer closest to the uppermost layer or the lowermost layer is displaced by an electric field in a direction parallel to the polarization direction formed between the common electrode and the electrode. Since the displacement is further restricted by the common electrode, the piezoelectric body is deformed in a unimorph mode. Therefore, since the deformation in the unimorph mode is performed in addition to the deformation in the shear mode, the deformation amount of the piezoelectric element increases. Thus, the piezoelectric body can be sufficiently deformed while reliably preventing a short circuit between the positive electrode and the negative electrode.

According to a third aspect of the present invention, in order to solve the above problem, in the inkjet head device according to the first or second aspect, the number of electrodes at the position of the ink pressure chamber in the laminating direction is reduced. The number of electrodes is greater than the number of electrodes at a partition wall position that partitions the ink pressure chamber.

According to the third aspect of the present invention, the number of electrodes at the position of the ink pressure chamber in the laminating direction is larger than the number of electrodes at the position of the partition wall that partitions the ink pressure chamber. The force of the electric field in the direction orthogonal to the direction increases, and the amount of deformation of the piezoelectric body increases.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. It should be noted that FIG. 7 showing a conventional example is also referred to for comparison with the present embodiment.

First, an outline of the ink jet head device of the present embodiment will be described with reference to FIG.

FIG. 1 is a perspective view showing a main part of a schematic configuration of a head for a line type ink jet printer. As shown in FIG. 1, in the head for a line type ink jet printer of the present embodiment, a plurality of piezoelectric ink jet heads 2 are arranged in parallel on the surface of a first ink flow path plate 3.

The first ink flow path plate 3 is a plate-like member made of aluminum or magnesium. A heater 4 having a stainless steel pattern sandwiched between polyimide films is attached to a front surface thereof. An outward path 4 for the ink supplied from the tank is formed. The first ink flow path plate 3 is formed with a through hole 7 penetrating from the front surface to the back surface and communicating with the outward path 4, and the ink supplied to the outward path 5 is directed to the front side by the through hole 7. Supplied. Further, the first ink channel plate 3 is bonded to the second ink channel plate 9.

The second ink flow path plate 9 is a plate-like member made of aluminum or magnesium similarly to the first ink flow path plate, and has a return path 8 for discharging ink to the ink tank on the back surface. Are formed.

On the other hand, the piezoelectric ink jet head 2
It comprises a base plate 10, a cavity plate 12, a nozzle plate 16, and a piezoelectric element 17.

The base plate 10 is a plate-like member made of aluminum or magnesium. The base plate 10 penetrates from the front surface to the back surface, and coincides with the through hole 7 formed in the first ink flow path plate 3. A through hole 11 is formed at the position. The base plate 1
Reference numeral 0 indicates that the back surface is bonded to the first ink flow path plate 3 with an adhesive, and the cavity plate 12 is bonded to the front surface with an adhesive.

The cavity plate 12 is a sintered body of ceramic, and has a plurality of ink pressure chambers 13 each having an open upper surface, a partition wall 14 for partitioning each ink pressure chamber 13,
An ink reservoir 15 that communicates with each ink pressure chamber 13 and communicates with the through hole 11 is formed on the back surface.

The nozzle plate 16 is a sheet member made of polyimide, and has a plurality of nozzles 16a penetrating from the front surface to the back surface. The front end side of the ink pressure chamber 13 opposite to the side of the ink reservoir 15 gradually becomes narrower, and an opening is formed in the front end surface.
The nozzle plate 16 is bonded by an adhesive so that the position of the opening and the position of the nozzle 16a coincide with each other on the front end surface.

The piezoelectric element 17 is a laminated piezoelectric element which is mounted so that the upper surface (open surface) of each ink pressure chamber 13 is closed, and is a lead zirconate titanate (PZT) system having a piezoelectric / electrostrictive effect. A plurality of piezoelectric ceramic layers made of the above ceramic material are laminated, and a pattern 18 of a positive electrode and a negative electrode such as silver palladium is formed between the piezoelectric ceramic layers by screen printing.

The electrode pattern 18 is connected to a power supply end (not shown), and the power supply end is connected to a drive IC 21 via a flexible printed circuit board 20. Further, the drive IC is connected via a flexible printed board 20 to a main board provided with a CPU and the like (not shown). Therefore, the drive IC is driven in accordance with the drive signal output from the main board, and the drive voltage is further applied from the drive IC to the electrode pattern 18.
The piezoelectric ceramic layer is displaced, the pressure in the ink pressure chamber 13 of the cavity plate 12 is changed, and ink is ejected from the nozzles 16 a formed in the nozzle plate 16.

This ink ejection operation is performed simultaneously by each of the piezoelectric ink jet heads 2 and
The entire head of the line type ink jet printer configured as described above swings in the direction of arrow A by a swing mechanism (not shown), so that high-speed printing is performed on the recording paper P in line units.

Next, the structure of the piezoelectric element 17 in the above-described piezoelectric ink jet head 2 of the present embodiment will be described in more detail with reference to FIGS.

FIG. 2A is a longitudinal sectional view of the piezoelectric ink-jet head 2 of the present embodiment cut in a direction parallel to the recording paper P of FIG. 1, and FIG. FIG. 2 is a plan view showing a pattern of a negative electrode on the layer and the third layer, FIG.
(C) is a plan view showing the pattern of the positive electrode on the second and fourth layers of the piezoelectric ceramic layer.

As shown in FIG. 2A, the piezoelectric element 17
Is a piezoelectric ceramic layer made of a lead zirconate titanate (PZT) -based ceramic material.
a, the first layer 19b, the second layer 19c, the third layer 19d, the fourth
The layers 19e and the bottom layer 19f are stacked in this order.

The top layer 19a is a layer that functions as a constraining layer, and a negative electrode pattern 18a is formed on the entire upper surface of the top layer 19a.

The first layer 19b, the third layer 19d, and the bottom layer 19f are provided at positions corresponding to the respective partition walls 14 as shown in FIG.
As shown in (B), a negative electrode pattern 18a extending in the longitudinal direction of the partition wall 14 and having an interval corresponding to the width of the ink pressure chamber 13 is formed between adjacent electrode patterns.

The second layer 19c and the fourth layer 19e have the structure shown in FIG.
2A, extends in the longitudinal direction of the ink pressure chamber 13 at a position corresponding to the center of each ink pressure chamber 13 in a cross-sectional view shown in FIG. A positive electrode pattern 18b having an interval corresponding to the interval between the central portions of the ink pressure chambers 13 is formed.

As described above, in the piezoelectric ink jet head 2 of this embodiment, only one of the electrode patterns of the negative electrode and the positive electrode is formed on each piezoelectric ceramic layer, and the electrode of the negative electrode is formed. There is no short circuit between the pattern and the positive electrode pattern.

The electrode patterns are laminated so as to overlap each other in the laminating direction of the piezoelectric ceramic layers, and each piezoelectric ceramic layer is polarized in the laminating direction as shown in FIG.

The electrode pattern of each positive electrode is connected to a driver IC 21 via a flexible substrate 20 shown in FIG. 1 and responds to a drive signal from a main substrate (not shown) connected via a flexible substrate 22. Thus, a positive voltage is applied from the driver IC 21.

The electrode pattern of each negative electrode is connected to a driver IC 21 via a flexible substrate 20 shown in FIG. 1, and a supply ground potential is applied to a main substrate (not shown) connected via a flexible substrate 22. You.

Next, the operation of the piezoelectric ink jet head 2 according to the present embodiment having the above configuration will be described.

When a controller (not shown) provided on the main board outputs a drive signal based on predetermined print data via the flexible board 22, the drive IC 21 causes the second layer 19c of the piezoelectric ceramic layer and the drive IC 21 to output the drive signal. A predetermined positive voltage is applied to the positive electrode pattern 18b on the fourth layer 19e. At this time, the ground potential is applied to the electrode patterns of the negative electrode formed on the top layer 19a, the first layer 19b, and the third layer 19d.

As a result, an electric field is generated between the positive electrode electrode pattern 18b and the negative electrode electrode pattern 18a (an electric field substantially perpendicular to the polarization direction of the piezoelectric ceramic layer indicated by an arrow in FIG. 2A). Thereby, the first layer 19b and the second layer 1
9c, the third layer 19d, and the fourth layer 19e are
Based on the electrostriction effect, it is deformed so as to be convex toward the ink pressure chamber 13 in the share mode. Further, an electric field in a direction parallel to the polarization direction is generated between the electrode pattern of the negative electrode on the top layer 19a and the electrode pattern 18b of the positive electrode on the second layer 19c, and the first layer 19b has a thickness of As the top layer 19a acts as a constraining layer, the first layer 19b is deformed in a unimorph mode so as to be convex toward the ink pressure chamber 13 side.

Therefore, at the position corresponding to the ink pressure chamber 13, the piezoelectric ceramic layer undergoes large displacement in the shear mode and the unimorph mode, and the ink pressure chamber 2
Since the volume of the ink cartridge 1 is reduced, the ink in the ink pressure chamber 13 is ejected from the nozzle 16a toward the printing paper to print characters and the like.

As described above, according to the piezoelectric ink jet head 2 of the present embodiment, by forming only the negative electrode or positive electrode pattern on each piezoelectric ceramic layer, the negative electrode electrode pattern and the positive electrode A large displacement can be obtained by deformation of the composite type in the shear mode and the unimorph mode while reliably preventing a short circuit at the time of manufacturing with the electrode pattern.

The excellent effects of the piezoelectric ink jet head 2 of the present embodiment are shown in FIGS. 4A and 4B.
By comparing with the conventional inkjet head shown in FIG. In this conventional ink jet head, as shown in FIG. 4A, both a negative electrode pattern 18a and a positive electrode pattern 18b are formed on each piezoelectric ceramic layer. As shown in FIG. 4B, they are alternately arranged with a small gap. Therefore, when an electrode pattern having such a shape and arrangement is formed on the piezoelectric ceramic layer by silver palladium or the like by a screen printing technique, an electrode forming material such as silver palladium flows out on the piezoelectric ceramic layer and the electrode of the negative electrode is formed. A short circuit sometimes occurred between the pattern and the electrode pattern of the positive electrode.

On the other hand, according to the piezoelectric ink jet head 2 of the present embodiment, even if an electrode forming material such as silver palladium flows out on each piezoelectric ceramic layer, the distance between adjacent electrode patterns is smaller than that of the conventional one. Sufficiently secured, and since only electrode patterns of the same polarity are formed on the same piezoelectric ceramic layer, short-circuiting between the negative electrode electrode pattern and the positive electrode electrode pattern as in the past is reliably prevented. can do.

Further, according to the piezoelectric ink jet head 2 of the present embodiment, there is no danger of short-circuit, so that the interval between the electrode pattern of the negative electrode and the electrode pattern of the positive electrode can be made shorter than before. It is possible to provide a high-resolution inkjet head having a short nozzle pitch.

As can be seen by comparing FIGS. 2A and 4A, the density of the electrode patterns in the laminating direction of the piezoelectric ceramic layers is smaller in the present embodiment than in the prior art. The displacement of the piezoelectric element decreases. However, as a result of the analysis, it was confirmed that the reduction rate of the displacement was only 6 to 7%, and there was no problem in practical use.

In the above example, the second layer 19c and the fourth
Since the positive electrode pattern 18b is formed on the layer 19e, two positive electrode patterns 18b are provided at the positions of the ink pressure chambers 13.
The positive electrode pattern 18b constructed as shown in FIG.
Can be increased.

The piezoelectric ink jet head 2 shown in FIG.
Forms a positive electrode pattern 18b as shown in FIG. 3B on the first layer 19b, the third layer 19d, and the bottom layer 19f, and forms 3 (C) on the second layer 19c and the fourth layer 19e. The electrode pattern 18a of the negative electrode as shown in FIG. As a result, as shown in FIG. 3A, the number of the electrode patterns 18b of the positive electrode at the position of the ink pressure chamber 13 becomes three.
Can be increased more than in the case of Therefore, the displacement of the piezoelectric element 17 can be increased, and the ink can be discharged more favorably.

Further, in the present embodiment, the ink jet head of the pushing type has been described, but the present invention is not limited to this. If the relationship of the polarization direction of the multilayer piezoelectric body 23 is reversed, the relationship is reversed. The piezoelectric ceramic layer can be deformed in the opposite direction, that is, the direction in which the volume of the ink pressure chamber 13 is increased, thereby making it possible to form a drawing-type inkjet head.

In this embodiment, a composite piezoelectric element of the shear mode and the unimorph mode is used. However, the present invention is not limited to this, and the composite piezoelectric element of the shear mode and the bimorph mode is used. Is also applicable.

[0048]

According to the ink jet head device of the first aspect, the positive and negative electrodes formed on the piezoelectric layer laminated in two or more layers and polarized in the laminating direction are formed on the same surface of the piezoelectric layer. Since only one of the positive or negative electrodes is arranged at a predetermined interval, and the positive electrode and the negative electrode are alternately formed in the laminating direction so as to have a predetermined interval from each other in the direction of the arrangement, Even if there is a variation in the accuracy at the time of electrode formation, a short circuit between the positive electrode and the negative electrode can be reliably prevented. Moreover, the positive electrode and the negative electrode are alternately formed so as to have a predetermined interval in the direction of arrangement of the electrodes in each piezoelectric layer when viewed in the laminating direction, so that a positive voltage is applied to the positive electrode. By applying a negative voltage to the negative electrode, an electric field is generated in a direction orthogonal to the direction of polarization of the piezoelectric body, and the piezoelectric body can be deformed in the shear mode. Further, since there is no danger of a short circuit between the positive electrode and the negative electrode, the pitch between the positive electrode and the negative electrode can be reduced, and a high-resolution inkjet head device with a short nozzle pitch can be provided. it can.

According to the ink jet head device of the present invention, a positive or negative common electrode is provided on the surface of the uppermost layer or the lowermost layer of the piezoelectric layer. Thus, the piezoelectric element can be deformed in the unimorph mode, and the amount of deformation of the piezoelectric body can be increased.

According to the ink jet head device of the third aspect, the number of electrodes at the position of the ink pressure chamber in the lamination direction of the piezoelectric bodies is larger than the number of electrodes at the partition wall position that divides the ink pressure chamber. The force of the electric field in the direction perpendicular to the polarization direction of the body can be increased, and the amount of deformation of the piezoelectric body can be increased.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a schematic configuration of a head for a line-type inkjet printer according to an embodiment of the present invention.

2A is a cross-sectional view illustrating a configuration of an inkjet head device used in the head of the line-type inkjet printer illustrated in FIG. 1, and FIG. 2B is formed on a piezoelectric ceramic layer of the inkjet head device of FIG. FIG. 2B is a plan view showing an electrode pattern of a negative electrode, and FIG. 2B is a plan view showing an electrode pattern of a positive electrode formed on a piezoelectric ceramic layer of the ink jet head device of FIG.

3A is a cross-sectional view illustrating the configuration of another example of the inkjet head device used in the head of the line-type inkjet printer illustrated in FIG. 1, and FIG. 3B is a piezoelectric ceramic layer of the inkjet head device illustrated in FIG. FIG. 2B is a plan view showing an electrode pattern of a positive electrode formed in FIG. 2B, and FIG. 2B is a plan view showing an electrode pattern of a negative electrode formed on a piezoelectric ceramic layer of the ink jet head device of FIG.

FIG. 4A is a cross-sectional view showing a configuration of an ink jet head device used in a conventional ink jet printer head, and FIG. 4B is a cross sectional view showing a positive electrode and a negative electrode formed on a piezoelectric ceramic layer of the ink jet head device of FIG. It is a top view showing the electrode pattern of an electrode.

[Explanation of symbols]

 2 Piezoelectric ink jet head 12 Cavity plate 13 Ink pressure chamber 14 Partition wall 17 Piezoelectric element 18a Negative electrode electrode pattern 18b Positive electrode electrode pattern 19a Top layer 19b First layer 19c Second Layer 19d: Third layer 19e: Fourth layer 19f: Bottom layer

Claims (3)

[Claims] 1. An ink jet head device for discharging ink by applying pressure fluctuation to ink stored in an ink pressure chamber, comprising: a piezoelectric layer laminated in two or more layers and polarized in a laminating direction; A positive electrode and a negative electrode formed between the piezoelectric layers, and only one of the positive and negative electrodes is arranged at a predetermined interval on the same surface of the piezoelectric layer; The electrodes and the negative electrodes are alternately formed so as to have a predetermined interval from each other in the direction of the arrangement, and are deformed by an electric field orthogonal to the direction of the polarization based on the application of a voltage to the positive electrode and the negative electrode. An inkjet head device characterized by the above-mentioned. 2. The ink jet head device according to claim 1, wherein a positive or negative common electrode is provided on a surface of an uppermost layer or a lowermost layer of the piezoelectric layer. 3. The method according to claim 1, wherein the number of electrodes at the position of the ink pressure chamber in the stacking direction is larger than the number of electrodes at a partition wall position that partitions the ink pressure chamber. Ink jet head device.