JPH03264360A - Ink jet record head - Google Patents

Abstract

PURPOSE:To provide a record head which is small in size, operated with a low voltage, and easy to manufacture, by constituting each piezoelectric actuator of electrodes and piezoelectric bodies laminated alternately, and utilizing the piezoelectric lateral displacement effect which occurs in a direction parallel to the faces of the electrodes when a voltage is charged. CONSTITUTION:A piezoelectric actuator 23, which is a laminated piezoelectric lateral displacement effect element utilizing the piezoelectric effect, has an integral constitution constituted of boardlike electric conductor layers and piezoelectric body layers laminat ed alternately and is manufactured in the shape of a comb having two grooves. When a drive circuit charges each signal electrodes 33a, 33b, 33c of the piezoelectric actuator 23 with signal voltage, the piezoelectric body layers contract due to the piezoelectric lateral displacement effect in a direction parallel to the surfaces of electrodes. At this time, ink flows in from an ink supply port, and an original length of the piezoelec tric actuator 23 is restored when the voltage is discharged. Consequently, teeth 23a, 23b, 23c previously constituting an inner wall of ink chambers 30a, 30b, 30c in an ink chamber block 24 are displaced to compress the ink chambers 30a, 30b, and 30c. As a result, pressure are generated in the ink chambers 30a, 30b, and 30c and injected through nozzles 29a, 29b, 29c communicating with each of the ink chambers for print ing.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an inkjet recording head.

[Prior Art] Printers are used as output devices for electronic devices such as word processors and personal computers, and an inkjet recording head is known as one of the heads used in these printers.

FIG. 9 shows a cross-sectional view of a conventional inkjet recording head.

In the figure, a base portion of a single-layer piezoelectric material 12 is attached to a support portion 11a of a support base 11. As shown in FIG. This piezoelectric body 12
Electrodes 13 and 14 are provided on the upper and lower surfaces, respectively, and a piezoelectric actuator 15 is constituted by the piezoelectric body 12 and the electrodes 13 and 14.

An ink chamber block 17 having an ink chamber 16 inside is provided on the support stand 11, and inside the ink chamber 16,
The tip 15a of the piezoelectric actuator 15 is inserted.

An orifice plate 19 having a nozzle 18 communicating with the ink chamber 16 is provided on the side surface of the ink chamber block 17, and an inkjet recording head is thus configured.

When a voltage is applied between the electrodes 13 and 14 from an external drive circuit (not shown), the piezoelectric body 12 contracts laterally, and then restores itself when the voltage is removed. As a result, the tip portion 15a of the piezoelectric actuator 15 reduces the volume of the ink chamber 16. The ink inside the ink chamber 16 is ejected from the nozzle 18 under the compression pressure, and printing is performed on paper or the like.

[Problems to be Solved by the Invention] In the conventional inkjet recording head described above, the piezoelectric body 12 is a single layer. Therefore, in order to obtain a predetermined amount of displacement and mechanical strength, it is necessary to make the piezoelectric body thick and long, and to apply a high voltage.

Furthermore, when manufacturing a multi-nozzle type recording head using this type of recording head, multiple piezoelectric actuators 1
5 must be individually inserted onto the support stand 11 and into the ink chamber 16 of the ink chamber block 17, and even if only the nozzle sections are integrated at high density, it becomes difficult to attach the piezoelectric elements as the number of nozzles increases. , the entire recording head becomes larger,
The process becomes complicated.

It is therefore an object of the invention to be compact, operate at low voltages,
Another object of the present invention is to provide an inkjet recording head that is easy to manufacture.

[Means for Solving the Problems] According to the present invention, the above-mentioned object includes a plurality of nozzles, a plurality of ink chambers each communicating with the nozzles, and a plurality of piezoelectric actuators capable of compressing each ink chamber. In the inkjet recording head, each piezoelectric actuator is composed of alternating layers of electrodes and piezoelectric bodies,
This is achieved by utilizing the piezoelectric lateral displacement effect, which causes displacement in a direction parallel to the electrode surface when a voltage is applied.

[Operation] When a voltage is applied to the piezoelectric actuators that are stacked alternately with electrodes in the thickness direction, the piezoelectric body is displaced in a direction parallel to the electrode surface due to the piezoelectric lateral displacement effect. It is restored when the voltage applied to the piezoelectric actuator is removed. As a result, the ink chamber is compressed and pressure is generated within the ink chamber, and ink is ejected through the nozzle to print on paper or the like.

[Examples] The inkjet recording head of the present invention will be described in detail below with reference to Examples.

FIG. 1 is a perspective view showing an embodiment of the inkjet recording head of the present invention.

In the figure, the base of a piezoelectric actuator 23 is attached to a support portion 22 of a support base 21, and an ink chamber block 24 is attached to the front portion of the support base 21.

The piezoelectric actuator 23 has a plurality of teeth (three in this embodiment) in front thereof.
is provided. These tooth portions 23a and 23b
.

23c indicates three slots (25a) of the ink chamber block 24.
.

25b, 25c (Fig. 3)) and each ink chamber (3h, 30b, 30c (Fig. 3)).
FIG. 3)) is formed. An orifice plate 26 is joined to the front surface of the support base 21 and the ink chamber block 24, and an ink path 27 is attached to the upper surface of the ink chamber block 24.

One ink injection hole 28 is provided in the ink path 27, and this ink injection hole 28 is connected to the ink chamber block 24.
Three slots 25a s 25b s 25c %, ie, three ink chambers, are connected to each other. The three ink chambers are also connected to the three nozzles 29a129 of the orifice plate 26.
b and 29C, respectively.

The electrodes of each tooth portion of the piezoelectric actuator 23 are connected to an external drive circuit (not shown). Note that the drive circuit may be placed on the piezoelectric actuator 23.

Ink injected from the ink injection hole 28 is stored in each ink chamber. When the piezoelectric actuator 23 is actuated, the three nozzles 291 N 29 of the orifice plate 26
b % Ink is ejected from 29C and printing is performed.

FIG. 2 is a perspective view of the piezoelectric actuator 23 shown in FIG. 1.

As shown in the figure, the piezoelectric actuator 23 has an integrated structure in which plate-shaped conductor layers and piezoelectric layers are laminated alternately and processed into a comb shape with two grooves. This is a type of laminated piezoelectric lateral displacement effect element.

Here, a layered piezoelectric lateral displacement effect element is defined as a stacked piezoelectric lateral displacement effect element that utilizes a piezoelectric lateral displacement effect. The piezoelectric lateral displacement effect means that when a voltage is applied to both sides of a piezoelectric material having a thickness T, it is polarized in the direction of the thickness T as shown by P, and is polarized in the direction parallel to the electrodes as shown by arrows D1 and D2, i.e. It is a displacement in the length direction (Fig. 4).

Two types of conductor layers having different lengths are used, and short conductor layers and long conductor layers are alternately stacked with piezoelectric layers in between. Since the conductor layer is divided together with the piezoelectric layer by the two grooves, the short conductor layer is divided into three independent long pieces, and the long conductor layer is formed in a comb shape. The three independent parts are used as signal electrodes 33g, 33b, 33c, respectively, and the comb-shaped part is used as common electrodes 34g, 34b, 3
4c (for example, a GND (ground) electrode).

Three signal electrodes 33a s 33b s 33c in each layer
are connection layers formed by electroless plating on the front surface of the piezoelectric actuator 23, and have teeth 23a and 23a, respectively.
23b and 23c are commonly connected.

The common electrodes 34a s 34b % 34c of each layer are commonly connected to each other by a connection layer formed by electroless plating at the rear of the piezoelectric actuator 23. These common electrodes 34a s 34b % 34c
and signal electrodes 33a, 33b, and 33c are connected to a drive circuit (not shown).

Note that the front surfaces of the signal electrodes 33a, 33b, and 33c may be coated with resin or the like.

A method of manufacturing such a piezoelectric actuator 23 will be explained.

First, a green sheet made of a piezoelectric ceramic material powder, an organic binder, a plastic material, etc. as a piezoelectric material and two types of conductor layers having different lengths are alternately stacked until the thickness of the piezoelectric actuator 23 is reached. Laminated. PZT (lead zirconium titanate) is preferably used as the material for the piezoelectric ceramic.

The length of the short conductor layer is the tooth portion 23a, 23b, 2
3c, that is, approximately equal to the length of the groove, the tooth portion 23a
, 23b% 23c are stacked so that one end is exposed to the front surface of the piezoelectric actuator 23.

The length of the long conductor layer is approximately slightly shorter than the length of the piezoelectric actuator 23, and the teeth 23a, 23b% 23c
The piezoelectric actuator 23 is laminated so that it is not exposed on the front side of the piezoelectric actuator 23 but exposed on the rear side of the piezoelectric actuator 23 .

This laminate of the green sheet and the conductor layer is cured by firing.

Next, a connection layer is formed on the surface of the cured laminate by electroless plating. This connects each conductor layer.

Next, the laminate whose surface has been electrolessly plated is provided with two grooves using a dicing saw to form a comb shape.

Note that although the laminate is cut with a dicing saw, it may also be processed with a laser, and may be subjected to pressing, injection molding, etc. before firing.

Then, the surface of the comb-shaped laminate is photo-etched to remove the connection layers on both sides, and wiring patterns 35a, 35b, 35c for connecting the drive circuit and each conductor layer are formed on the top and bottom surfaces. .

The piezoelectric actuator 23 formed in this way is
A signal voltage ■ is applied from an external control circuit (not shown) to the common electrodes 34a, 34b, 34c and one of the three signal electrodes 33a, 33b, 33c (signal electrode 33a in the figure) via a drive circuit. Tooth portions 23g, 23b, 23c (23a in the figure) of the piezoelectric actuator 23 correspond to when the signal voltage V is applied.
) is displaced in the direction of arrow A in the figure due to the piezoelectric lateral displacement effect, and then returns to its original state when the voltage is released.

Although the number of teeth is three in this embodiment, it is not limited to this, and may be increased or decreased depending on the number of nozzles.

FIG. 3 is an explanatory diagram for explaining the relationship between the ink chamber block 24 and the piezoelectric actuator 23 in FIG. 1.

In the figure, the ink chamber block 24 includes three ink chambers 3Ga% 30bN 3h and an ink chamber block 2.
An ink supply path 31 that communicates with the inside of the ink supply channel 4 is provided.

Three slots 25a s 25b of the ink chamber block 24
525c is the tooth portion 23a of the piezoelectric actuator 23.
The tips of s 23b 523c are inserted respectively, and these teeth 23a % 23b % 23c and slot 25! , 25b, 25C and the orifice plate 26 form ink chambers 30a, 30b, 30c.
is formed.

Note that in this embodiment, the tooth portion 23 of the piezoelectric actuator 23
The ink chamber 3 (l
a, 3 (1b s 30c, but is not limited to this, it is a member that becomes a piston, and the ink chamber 30g
, 30b, , 30c may be formed, and this piston may be pressed by the teeth 23a, 23b-23c.

Further, when the ink chambers 30a, 30b, 30c are provided in the ink chamber block 24 made of a metal plate, it is difficult to perform minute precision machining of shapes other than circular. However, since it is not possible to reduce the distance between the plurality of nozzles, it is formed by etching a photosensitive glass such as silicate glass (for example, HOYA photosensitive glass PEG3).

FIG. 5 is a side view illustrating the assembly of the inkjet recording head shown in FIG. 1.

In the same figure, the teeth 23a, 23b of the piezoelectric actuator 23 attached to the support part 22 of the support base 21,
The tip of 23C is the ink chamber 30 of the ink chamber block 24
It constitutes one inner wall of a130b130C. An ink path 27 is joined on top of the ink chamber block 24,
The ink injection hole 28 is connected to the ink chamber 3Qa s 3[11
+% Connected to 30c. An orifice plate 26 is attached to the front surface of the support portion 22 and ink chamber block 24 configured in this manner. The orifice plate 26 has a tapered nozzle 29a % 29b % 2
9c is provided, and ink chambers 3h, 30b,
It is connected to 30c.

Orifice plate 26 can be formed using electroforming technology.

Electroforming technology is a precision processing technology that uses metal. As shown in the explanatory diagram of electroforming technology in FIG. 6, a resist 32 is applied to the base member, a part that will become a nozzle is left by photolithography, and then the entire area is plated (for example, Ni) to cover the periphery of the resist. ((A) in the same figure). After plating, the resist is washed off and the film is peeled off from the base member ((B) in the same figure). In addition, Si(
A silicon wafer may be used as the orifice plate 26 and etched to form the nozzle 29.

Next, the operation of the inkjet recording head of this embodiment will be explained.

Each signal electrode 33 of the piezoelectric actuator 23 from the drive circuit
When a signal voltage is applied to M, 33b% 33c,
Due to the piezoelectric lateral displacement effect, the piezoelectric layer moves in the direction parallel to the electrode surface (
shrink in the length direction). At this time, ink flows from the ink supply port, and when the voltage is then removed, the piezoelectric actuator 23g returns to its original length. As a result, the ink chambers 3h, 30b, in the ink chamber block 24 are
Tooth portions 23a, 23b, which constitute one inner wall of 30c,
23c is displaced to open the ink chambers 30a and 30b.

Compress 30c.

For this reason, the ink chambers 3h, 3(lb, 3[1c
Pressure is generated in the ink chamber 30a% 30b%
Nozzles 29a, 29b, 29 communicating with 30c
Printing is performed by ejecting from c.

Note that the amount of displacement Δl of the piezoelectric actuator 23 in the lateral direction (in the direction of the arrow in the figure) in FIG. 2 can be determined from Δl.

In this equation (1), if the length L is 10 mm, the layer thickness T is 50 μm, the applied voltage V is 50 V, and the piezoelectric lateral displacement effect constant is d, then Δl = 3 x 1G-6m.

It is assumed that the dimensions of the tooth portion 23+1 of the piezoelectric actuator and the ink chamber 3h are set as shown in FIG.

The figure shows the vicinity of the ink chamber. Nozzle pitch 3
00μm1 If the displacement of the tooth portion 23a is △l, then the ink chamber 3
The volume displacement △V of 0a is 500 μm x 200 μm x
It becomes △l. If the displacement Δl of the tooth portion 23g is 2×10 −6 m, then the ink chamber 30! The volumetric displacement △V is 2×10-13
m3.

For example, the volume of an ink sphere with a radius of 20 μm is 3.2 × 10
- It is possible to spray droplets sufficiently large compared to 14 m3. In other words, if the above dimensions are taken, the nozzle pitch is 1 m compared to the conventional one.
It is also possible to set the thickness to 300 μm or less, which is sufficiently smaller than m, and it is possible to increase the density of printing.

Furthermore, the tooth portion 23a of the piezoelectric actuator 23 % 23
The length of b 523c can also be shortened.

FIG. 8 is a comparative diagram of a piezoelectric lateral displacement effect and a piezoelectric longitudinal displacement effect for explaining the piezoelectric lateral displacement effect in the present invention.

In the figure, it is assumed that a voltage V is applied to a piezoelectric body having a thickness T and having electrodes provided on both sides. In this case, it is displaced in a direction perpendicular to the electrode surface, that is, in the vertical direction, and also in a direction parallel to the electrode, that is, in the lateral direction.

When the transverse effect constant is d31, the displacement amount △l in the horizontal direction is obtained from equation (1), and when the longitudinal effect constant is d33, the displacement amount △t in the vertical direction is calculated as follows: △t=d33×V... ...(2) Therefore, if you want to increase the dimensional displacement, in the case of a piezoelectric vertical displacement effect element that utilizes the piezoelectric vertical displacement effect, the only way is to increase the voltage ■ or to stack piezoelectric materials. In the case of a piezoelectric lateral displacement effect element, there is an advantage that dimensional displacement can be increased by increasing the length L and decreasing the thickness T of the piezoelectric element.

In this way, by using a piezoelectric actuator in which piezoelectric layers are laminated using the piezoelectric lateral displacement effect, the piezoelectric actuator can be made smaller, a predetermined amount of displacement and mechanical strength can be obtained, and it is possible to individually It saves the manufacturing process and can operate at low voltage. Furthermore, since the ink chambers are individually pressed by the piezoelectric layer actuators, crosstalk can also be avoided.

[Effects of the Invention] As described in detail above, according to the present invention, there is provided an inkjet including a plurality of nozzles, a plurality of ink chambers each communicating with the nozzles, and a plurality of piezoelectric actuators capable of compressing each ink chamber. In the recording head, each piezoelectric actuator is composed of alternating layers of electrodes and piezoelectric layers, and utilizes the piezoelectric lateral displacement effect of displacing in a direction parallel to the electrode surface when a voltage is applied. As a result, it is possible to manufacture an inkjet recording head that can obtain a predetermined amount of displacement and mechanical strength, is small in size, requires a small number of assembly steps, and can be operated at low voltage.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the inkjet recording head of the present invention, FIG. 2 is a perspective view of the piezoelectric actuator shown in FIG. 1, and FIG. 3 is a perspective view of the ink chamber block and piezoelectric actuator shown in FIG. FIG. 4 is an explanatory diagram for explaining the piezoelectric lateral displacement effect, FIG. 5 is a side view for explaining the assembly of the same recording head shown in FIG. 1, and FIG. is an explanatory diagram of electroforming technology,
FIG. 7 is a diagram showing the vicinity of the ink chamber, FIG. 8 is a comparative illustration of the piezoelectric lateral displacement effect and the piezoelectric longitudinal displacement effect to explain the piezoelectric lateral displacement effect in the present invention, and FIG. 9 is a diagram of the inkjet recording head. FIG. 2 is a sectional view showing a conventional example. 21...Support stand, 22...Support part, 2
3. Old... Piezoelectric actuator, 23a s 23b
s 23c... Teeth, 24... Ink chamber block, 2r'a % 25b % 25c...
... Slot, 26 ... Orifice plate, 2
7... Ink path, 29... Nozzle,
30a, 30b, 30c...Ink chamber, 33g, 33b, 33cm---Signal electrode, 34a, 34b, 34C...Common electrode, 35a s 35b s 35c...・Wiring slam.

Claims (1)

[Claims] An inkjet recording head comprising a plurality of nozzles, a plurality of ink chambers respectively communicating with the nozzles, and a plurality of piezoelectric actuators capable of compressing the ink chambers, each piezoelectric actuator comprising an electrode and a piezoelectric body. An inkjet recording head characterized in that the inkjet recording head is constructed by alternately laminating layers, and utilizes a piezoelectric lateral displacement effect that causes displacement in a direction parallel to the electrode surface when a voltage is applied.