JP2000225702A - Fabrication of piezoelectric element and ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress fluctuation in the area of inner electrodes of a piezoelectric element by setting the width of an inner electrode narrower at the central part than at the end part when the inner electrodes are screen printed on a green sheet. SOLUTION: When inner electrodes 72, 73 composed of a paste metal material are screen printed on a green sheet 61, the inner electrodes 72, 73 are recessed in the center of the sides 72a, 73a not to be connected with outer electrodes and printing is performed while setting the width L2 at the central part shorter than the width L1 at the end part. When the printed inner electrodes 72, 73 are pressure laminated and fired, they have substantially linear sides 72a, 73a. More specifically, the inner electrodes 72, 73 are substantially rectangular under pressure laminated state. Since fluctuation in the area of inner electrodes of each piezoelectric element is suppressed when a laminated piezoelectric element is split by slit machining, fluctuation of ink drop ejection characteristics is suppressed among channels resulting in a high image quality.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a piezoelectric element and an ink jet head.

[0002]

2. Description of the Related Art In an ink jet recording apparatus used as an image forming apparatus such as a printer, a facsimile, a copying apparatus, etc., a plurality of nozzles for discharging ink droplets, an ink liquid chamber communicating with each nozzle, and ink in each ink liquid chamber are formed. A piezo actuator type inkjet head equipped with an electromechanical conversion element such as a piezoelectric element that generates energy for discharging ink droplets from a nozzle by applying pressure is mounted, and the piezoelectric element of the head is driven according to print data. There is an ink jet recording apparatus that discharges ink droplets from required nozzles to record an image on paper.

There is a piezo actuator type ink jet head using a piezoelectric element. As shown in FIGS. 8 and 9, a general piezoelectric element has a piezoelectric material 101, a plus-side internal electrode 102, and a ground-side internal electrode 103 that are alternately laminated, and the plus-side internal electrode 102 is drawn out to one end face. Connected to the end face electrode (external electrode) 104 and the ground (GND) side internal electrode 1
Reference numeral 03 denotes an end face electrode (external electrode) 10 which is drawn out to the other end face.
5 (for example, Japanese Patent Laid-Open No. 8-332725).

However, if the plus side internal electrode and the GND side internal electrode are exposed in an overlapping manner in the laminating direction on the end face of the piezoelectric element where the end face electrode is not formed, as in this piezoelectric element, the piezoelectric element is During the polarization process, a short circuit may be caused by gripping or hitting the end face with tweezers. Therefore, as shown in FIGS. 10 and 11, it is conceivable that the internal electrodes 102 and 103 are retracted from the end faces where the end face electrodes 104 and 105 are not formed so as not to be exposed.

[0005]

The above-described piezoelectric element has an internal electrode (paste-like metal) on a green sheet.
Is applied by screen printing, and it is alternately laminated and fired. When this is used as an actuator of an ink jet head, it is cut to about 100 μm with a dicing saw or the like.

However, in an ink jet head in which a plurality of piezoelectric elements are arranged in a row, the displacement (d31 mode) or the generated force (d33) varies between channels in the piezoelectric elements, even though they are manufactured in the same process. Found that the flying characteristics of the ink varied.

[0007] When the cause was investigated, the central portion of the internal electrode swelled and the area of the central portion was larger than the end portion. There is a variation in the internal area between the element and the element, and such a variation in the area of the internal electrode is the final shape when the internal electrode is applied to the green sheet as shown in FIG.
Alternatively, the side not connected to the external electrode is printed in a straight shape as shown in FIG. 10, but when the green sheets are overlapped and pressed against each other, the central part of the internal electrode swells and protrudes as shown in FIG. It was confirmed that this was due to the shape.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a method of manufacturing a piezoelectric element for reducing variations in the area of internal electrodes, and provides an ink jet head capable of obtaining stable ink droplet ejection quality. The purpose is to:

[0009]

According to a first aspect of the present invention, there is provided a method of manufacturing a piezoelectric element comprising a piezoelectric material and internal electrodes alternately laminated, wherein the piezoelectric element has When printing the electrode on the green sheet by screen printing, the width of the central portion of the internal electrode is smaller than the width of the end portion, and printing is performed.

According to a second aspect of the invention, there is provided a method of manufacturing a piezoelectric element according to the first aspect, wherein the shape of the end of the internal electrode which is not connected to the external electrode is printed in a curved line.

According to a third aspect of the present invention, there is provided a method of manufacturing a piezoelectric element according to the first or second aspect, wherein a difference in width between a center portion and an end portion of the internal electrode is 2 to 6%. And

According to a fourth aspect of the present invention, there is provided an ink jet head for ejecting ink droplets using a piezoelectric element, wherein the piezoelectric element is a piezoelectric element manufactured by the manufacturing method according to any one of the first to third aspects. There was a certain configuration.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an exploded perspective view showing an example of an inkjet head to which the present invention is applied, and FIG.
FIG. 3 is an enlarged cross-sectional view of a main part of the head in the inter-row direction, and FIG. 3 is an enlarged cross-sectional view of a main part of the head in the inter-channel direction.

This ink jet head includes a drive unit 1, a liquid chamber unit 2, and a head cover 3. The drive unit 1 includes a plurality of piezoelectric elements 12 arranged in two rows and joined to a substrate 11 made of a barium titanate-based ceramic, and a resin, a ceramic, or the like surrounding the periphery of each of the two rows of piezoelectric elements 12. The frame member 13 is joined by an adhesive. Multiple piezoelectric elements 1
Reference numeral 2 denotes a piezoelectric element to which a driving pulse for causing the ink to be formed into droplets and fly is provided (this is referred to as a “driving unit”).
And a piezoelectric element which is located between the driving units 17 and 17 and serves as a liquid chamber support member for simply fixing the liquid chamber unit 2 to the substrate 11 without applying a driving pulse (this is called a “non-driving unit”).
That. ) Are alternately configured.

Here, as the piezoelectric element 12, a laminated piezoelectric element having ten or more layers is used. As shown in FIG. 2, this laminated piezoelectric element is composed of lead zirconate titanate (PZT) 20 having a thickness of 10 to 50 μm / 1 and a thickness of several μm / 1.
Internal electrode 21 made of silver / palladium (AgPd)
Are alternately laminated.

The internal electrodes 21 of each piezoelectric element 12 are left and right end face electrodes 22 and 23 made of AgPd every other layer (the opposing face sides of the two piezoelectric element rows are end face electrodes 22, and the non-opposing face sides are end face electrodes). 23). On the other hand, as shown in FIG.
Each pattern of the common electrode 24 and the individual electrode 25 is provided by Au plating, AgPt paste printing, AgPd paste printing, or the like.

The opposite end electrodes 22 of the piezoelectric elements 12 in each row are connected to the common electrode 24 via a conductive adhesive 26.
On the other hand, the non-opposing end surface electrodes 23 of the piezoelectric elements 12 in each row are connected to the individual electrodes 25 via the conductive adhesive 26 in the same manner. Thereby, the driving unit 17
When a drive voltage is applied to the drive unit 17, an electric field is generated in the stacking direction, and the driving unit 17 is displaced in the stacking direction (d 33).
Direction displacement) occurs. As shown in FIG. 2, the common electrode 24 has a hole 13a formed in the frame member 13.
By filling the inside with the conductive adhesive 26, the pattern connected to each piezoelectric element is conducted.

On the other hand, the liquid chamber unit 2 includes a diaphragm 31 made of a metal material, a resin, or the like, and a dry film resist (D).
FR), a liquid chamber partition member 32 of a two-layer structure formed of a photosensitive resin layer of FR, and a nozzle plate 33 of a metal material.
Are sequentially laminated and heat-sealed. By each of these members, one piezoelectric element 12 (driving unit 17)
And a diaphragm portion 34 corresponding to the one piezoelectric element 12, a pressurized liquid chamber 35 pressurized through each diaphragm portion 34, and a pressurized liquid chamber located on both sides of the pressurized liquid chamber 35. Common liquid chambers 36, 36 for introducing ink to be supplied to 35
One channel is formed by the ink supply passages 37 and 37 communicating the pressurized liquid chamber 35 and the common liquid chambers 36 and 36, and a nozzle 38 communicating with the pressurized liquid chamber 35. Two rows are provided.

The diaphragm 31 is formed of a metal material, for example, a Ni plating film by an electroforming method. The diaphragm 34 corresponding to the drive unit 17, the beam 41 and the frame member 13 joined to the non-drive unit 18 are provided. Base 42 to be joined to
And form. The diaphragm section 34 includes the driving section 17
And an outermost thin film portion (diaphragm region) 44 having a thickness of about 3 to 10 μm formed around the convex portion 43.

The liquid chamber partition member 32 is formed by laminating a dry film resist on the diaphragm 31 side in advance, exposing it with a required mask, and developing it to form a first photosensitive resin layer 45 having a predetermined liquid chamber pattern. And a second photosensitive resin layer 46 having a predetermined liquid chamber pattern formed by laminating a dry film resist in advance on the nozzle plate 33 side, exposing using a required mask, and developing the predetermined liquid chamber pattern. Become.

The nozzle plate 33 is formed of a metal material, for example, a Ni plating film by an electroforming method, and has a large number of nozzles 38 which are fine discharge ports for flying ink droplets. The inner shape (inner shape) of the nozzle 38 is formed in a horn shape (may be a substantially columnar shape or a substantially truncated cone shape). The diameter of the nozzle 38 is about 25 to 35 μm on the ink droplet outlet side.

The ink ejection surface (nozzle surface side) of the nozzle plate 33 is a water-repellent layer 47 which has been subjected to a water-repellent surface treatment as shown in FIG. For example, PTF
Ink physical properties such as E-Ni eutectoid plating, electrodeposition coating of fluororesin, vapor-deposited evaporative fluororesin (for example, pitch fluoride), baking after solvent application of silicon resin or fluorine resin The water-repellent treatment film selected according to the above is provided to stabilize the ink droplet shape and the flying characteristics so that high-quality image quality can be obtained.

The substrate 11 of the drive unit 1 and the piezoelectric element 12 and the frame member 13 are assembled by bonding with an adhesive 49, and the liquid chamber unit 2 is processed and assembled separately from the drive unit 1. After that, the vibration plate 31 of the liquid chamber unit 2 and the piezoelectric element 12 and the frame member 13 of the drive unit 1 are joined with an adhesive 50 to form an ink jet head.

The substrate 11 is supported and held on a spacer member (head holder) 51 serving as a head support member.
C and the electrodes 24 and 25 connected to the piezoelectric elements 12 (drive unit 17) of the drive unit 1
They are connected via PC cables 53,53.

The nozzle cover 3 is made of a box-shaped metal material that covers the periphery of the nozzle plate 33 and the side surface of the head, and has an opening corresponding to the water-repellent treatment layer 47 of the nozzle plate 33. The periphery of the nozzle plate 33 is joined with an adhesive. Further, in order to supply ink from an ink cartridge (not shown) to the liquid chamber, a spacer member 51 and a substrate 1
1. The ink supply holes 54 to 57 are provided in the frame member 13 and the vibration plate 31, respectively.

In the ink jet head thus configured, by applying a drive waveform (pulse voltage of 10 to 50 V) to the drive unit 17 according to the recording signal, a displacement in the stacking direction occurs in the drive unit 17, Diaphragm 31
The pressurized liquid chamber 35 is pressurized through the diaphragm section 34 of the above, and the pressure rises, and ink droplets are ejected from the nozzle 38. At this time, ink flows also in the direction of the ink supply passages 37, 37 leading from the pressurized liquid chamber 35 to the common liquid chamber 36. However, by reducing the cross-sectional area of the ink supply passages 37, 37, the fluid resistance portion is reduced. Function to reduce the flow of ink toward the common liquid chambers 36, 36, thereby preventing a drop in ink ejection efficiency.

Thereafter, as the ink droplet ejection ends, the ink pressure in the pressurized liquid chamber 35 decreases, and a negative pressure is generated in the pressurized liquid chamber 34 due to the inertia of the ink flow and the discharge process of the drive pulse. To the ink filling process. At this time, the ink supplied from the ink tank flows into the common liquid chambers 36, 36, and from the common liquid chambers 36, 36 to the ink supply paths 37, 3.
After that, it is filled into the pressurized liquid chamber 35. Then, the vibration of the ink meniscus surface near the outlet of the nozzle 38 is attenuated,
When the ink is returned to the vicinity of the outlet of the nozzle 38 due to surface tension (refill) and reaches a stable state, the operation shifts to the next ink droplet ejection operation.

Next, a method of manufacturing the piezoelectric element 12 in the ink jet head will be described with reference to FIGS. As described above, the plurality of piezoelectric elements 12 used in the inkjet head are divided into a plurality of pieces by slit processing. Before the slit processing, as shown in FIG. Piezoelectric material 61 such as lead zirconate titanate (PZT) and a thickness of several μm / 1
An electrode material serving as an internal electrode such as silver / palladium (AgPd) of the layer (also referred to as “internal electrode”) 62, 63
Are alternately laminated to form a sheet-shaped or plate-shaped laminated piezoelectric element 60. On the laminated piezoelectric element 60, end surface electrodes 64 and 65 which become the end surface electrodes 22 and 23 after slitting are formed. I have.

A first embodiment in which the present invention is applied to the laminated piezoelectric element 60 will be described with reference to FIG. In this embodiment, a green sheet (piezoelectric material) 61 is used.
When the internal electrodes 62 and 63 made of a paste-like metal material are screen-printed, the width L2 of the central portion is reduced by recessing the central portions of the sides 62a and 63a that are not connected to the external electrodes of the internal electrodes 62 and 63. Printing is performed with the width smaller than the width L1 of the end portion. The internal electrodes 62 and 63 in this printing state
The sides 62a and 63a which are not connected to the external electrodes have a shape in which the center and the end are connected by a straight line.

As described above, when the width of the central portion L2 of the internal electrodes 62 and 63 is smaller than the width L1 of the end portion and the layers are pressed and laminated, and fired, the internal electrodes are drawn as indicated by phantom lines in FIG. The shape of the electrodes 62 and 63 is the side 62 not connected to the external electrode.
a, 63a have a substantially linear shape. That is, the internal electrodes 62 and 63 have a substantially rectangular shape in the state of being stacked and pressed.

Thus, when the laminated piezoelectric element 60 is divided by slitting, the variation in the area of the internal electrode 21 of each piezoelectric element 12 is reduced, and the variation in the ink droplet ejection characteristics between channels is reduced. , High image quality can be obtained.

Next, a second embodiment of the manufacturing method according to the present invention will be described with reference to FIG. In this embodiment,
Sides 62a of the internal electrodes 62, 63 which are not connected to the external electrodes,
63a has a curved shape. By making such a curved shape, when compared with the polygonal line shape of the first embodiment, the shape becomes closer to a straight line in the state of lamination pressure welding.

Next, a third embodiment of the manufacturing method according to the present invention will be described with reference to FIG. In this embodiment,
A side 62a of the internal electrodes 62 and 63 that is not connected to the external electrode;
63a has a shape that forms a part (arc) of a circle passing through points A, B, and C. Then, the position of the center point B is set to a position that is shorter than the end points A and C by about 2 to 6%, that is,
By setting (L1−L2) / L1 × 100 = 2 to 6 (%), the shape becomes closer to a straight line in the state of lamination pressing.

In the above-described embodiment, the present invention has been mainly described as an example in which the present invention is applied to a laminated piezoelectric element composed of about 10 piezoelectric material layers and internal electrodes. The electrode can be applied to all piezoelectric elements having one or more layers. In the above embodiment, the description has been given of the piezoelectric element applied to the ink jet head. However, the present invention can be similarly applied to piezoelectric elements used as other actuator elements.

[0035]

As described above, according to the method of manufacturing a piezoelectric element according to the first aspect, when the internal electrodes of the piezoelectric element are printed on the green sheet by screen printing, the width of the central portion of the internal electrodes is reduced. Since the printing is made smaller than the width of the portion, the variation in the area of the internal electrodes can be reduced.

According to the method for manufacturing a piezoelectric element of the second aspect,
In the method of manufacturing a piezoelectric element according to the first aspect, the configuration is such that the shape of the end of the internal electrode that is not connected to the external electrode is printed in a curved line, so that the variation in the area of the internal electrode can be further reduced.

According to the method of manufacturing a piezoelectric element of claim 3,
In the method for manufacturing a piezoelectric element according to claim 1 or 2, the difference in width between the central portion and the end portion of the internal electrode is 2 to 6%, so that the variation in the area of the internal electrode can be further reduced. Can be.

According to the ink jet head of the fourth aspect, in the ink jet head for ejecting ink droplets using the piezoelectric element, the piezoelectric element is the piezoelectric element manufactured by the manufacturing method of any one of the first to third aspects. With the configuration, the variation in the ink droplet ejection characteristics between the channels is reduced, and the image quality can be improved.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing an example of an inkjet head to which the present invention is applied.

FIG. 2 is an enlarged sectional view of a main part of the head in a direction between rows.

FIG. 3 is an enlarged sectional view of a main part of the head in a direction between channels.

FIG. 4 is a perspective view showing an example of a laminated piezoelectric element.

FIG. 5 is an explanatory view of a coating pattern of an internal electrode of the laminated piezoelectric element for explaining the first embodiment of the present invention.

FIG. 6 is an explanatory view of a coating pattern of an internal electrode of a laminated piezoelectric element for explaining a second embodiment of the present invention.

FIG. 7 is an explanatory view of a coating pattern of an internal electrode of a laminated piezoelectric element for explaining a third embodiment of the present invention.

FIG. 8 is an explanatory view of an internal electrode pattern and a coating pattern of a general laminated piezoelectric element.

FIG. 9 is an explanatory view of opposed end faces of the laminated piezoelectric element.

FIG. 10 is an explanatory diagram of another example of the internal electrode pattern of the multilayer piezoelectric element and its application pattern.

FIG. 11 is an explanatory view of opposed end faces of the laminated piezoelectric element.

FIG. 12 is an explanatory diagram of an actual internal electrode pattern when applied with the application pattern of FIG. 8;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Drive unit, 2 ... Liquid chamber unit, 11 ... Substrate, 1
2 Piezoelectric element, 20 Piezoelectric material, 21 Internal electrode, 2
2, 23, 64, 65 ... end face electrode, 60 ... laminated piezoelectric element, 61 ... piezoelectric material (green sheet), 62, 63 ...
Internal electrode (electrode material).

Claims (4)

[Claims] In a method of manufacturing a piezoelectric element in which a piezoelectric material and internal electrodes are alternately laminated, when the internal electrodes of the piezoelectric element are printed on a green sheet by screen printing, the width of the central portion of the internal electrode is set to an end. A method for manufacturing a piezoelectric element, wherein printing is performed with a width smaller than a width of a portion. 2. The method for manufacturing a piezoelectric element according to claim 1, wherein the shape of the end of the internal electrode that is not connected to an external electrode is printed in a curved line. 3. The method for manufacturing a piezoelectric element according to claim 1, wherein a difference in width between a center part and an end part of the internal electrode is 2 to 6%. Method. 4. An ink jet head for ejecting ink droplets using a piezoelectric element, wherein the piezoelectric element is a piezoelectric element manufactured by the method according to claim 1. .