JPS634959A - Ceramic ink jet head and its preparation - Google Patents

Abstract

PURPOSE:To obtain an ink jet head excellent in the uniformity of a jet characteristic, by a method wherein, a plurality of electrodes each constituted by laminating at least three layers at a definite interval are provided in the wall of a pressure chamber and electrode terminal parts constituted so that mutual odd-number-th electrodes and mutual even-number-th electrodes can be electrically connected through through- holes formed in the lamination direction of the electrodes are provided. CONSTITUTION:The electrode pattern of a first layer and that of a third layer counted from the side near to an ink chamber have lead-out electrodes 108, 109 electrically connecting drive electrodes 107 and further connecting the same to an external drive circuit and the electrode patterns of second and fourth layers have such a shape that lead-out electrodes 110 for connecting the drive electrodes 107 to the external drive circuit indivisually extend from the drive electrodes 107. Two electrode patterns are alternately laminated in an up-and-down direction and through-holes 113 piercing through ceramic layers are formed to the central parts of the electrode terminal parts 111, 112 provided to the leading ends of the lead-out electrodes 109, 110 and filled with a conductive paste before and after the laminate of the ceramic layers is sintered to respectively connect the electrodes of odd-number and even-number layers.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an inkjet head used in various printers and facsimile machines and a method of manufacturing the same. The present invention relates to a drop-on demant type inkjet head that performs ink jetting and a method of manufacturing the same.

(Prior Art) A diaphragm method is widely known as a method for applying pulse pressure to ink in an on-day inkjet. That is, a diaphragm is formed by pasting a rectangular or circular plate-like electromechanical transducer element on a plate made of metal, glass, or the like that constitutes the wall of an ink chamber in an inkjet head. When the electromechanical transducer is contracted and deformed in the plane direction by applying a voltage in the thickness direction, the wall of the ink chamber forming the diaphragm is curved toward the ink chamber. As a result, the pulse pressure acts and the ink inside the ink chamber is pushed out of the ink chamber.

(Problems to be Solved by the Invention) In the pulse pressure generating means described above, it is important to affix the electromechanical transducer to a predetermined position on the wall of the ink chamber with sufficient adhesive strength to ensure precision. However, since the electromechanical transducer is fixed outside the wall of the ink chamber,
It has been difficult to accurately fix the electromechanical transducer at a position corresponding to the ink chamber inside the wall. In addition, strict process control is carried out to always reproduce the thickness and adhesive strength of the adhesive layer at the adhesive part within the specified range, but it is still difficult to suppress variations in ink jetting characteristics due to variations in the adhesive state. It has been strongly desired to eliminate such an adhesion process.

Further, the pressure applied to the ink by the pulse pressure generating means and the volume of ink ejected from the nozzle depend on the voltage value applied to the electromechanical transducer. In the conventional on-day cloak-type inkjet head, the voltage value of the applied pulse is 50 V in order to apply a sufficient amount of pressure to the ink and eject the necessary volume of ink from the nozzle.
It was necessary to set the voltage to a high value such as 300v. However, from the viewpoint of increasing the reliability or reducing the cost of the drive circuit, there has been a strong desire to reduce the voltage to 50 V or less.

A so-called laminated actuator, in which a large number of thin electromechanical transducer elements are laminated in the thickness direction with electrode spacing in the thickness direction, is known as a device that achieves the above-mentioned voltage reduction. By adhering this laminated actuator to the outside of the wall of the ink chamber, it is expected that a drop-on demant type inkjet head that can be driven at low voltage will be realized. Problems such as the difficulty of always accurately fixing the laminated actuator in position and the variation in ink ejection characteristics depending on the adhesion state remained unsolved.

(Means for Solving the Problems) According to the first invention of the present application, an ink flow path is formed inside the ink supply port, passes through the pressure chamber, and communicates with the nozzle, and is made of a ceramic material having electromechanical conversion characteristics. The pressure chamber has a plurality of electrodes laminated in at least three layers at regular intervals inside the wall of the pressure chamber, and among the plurality of electrodes, odd-numbered comrades and even-numbered comrades are An inkjet head characterized in that it has an electrode terminal portion configured to be electrically connected through a through hole formed in the stacking direction of the electrodes.

Further, according to the second invention of the present application, the step of forming a molding hole matrix in accordance with the planar shape of the ink flow path that communicates the photosensitive resin sheet from the ink supply port through the pressure chamber to the nozzle; A step of forming a first electrode having an electrode terminal portion having a through hole on a green sheet made of a ceramic material having electromechanical conversion characteristics using a conductive paste, and an electrode terminal having the through hole on the green sheet. a multilayer electrode layer formed by alternately laminating at least three layers of two types of green sheets on which the first and second electrodes are formed; a step of forming a laminate by laminating and press-bonding the hole matrix and the green sheet, and filling the through holes formed in the electrode terminal portion with conductive paste to connect the first electrode and the second electrode, respectively. There is obtained a method for manufacturing a ceramic inkjet head characterized by comprising the steps of electrically connecting the electrodes in the lamination direction, and sintering the laminated body.

(Function) According to the present invention, a large number of ceramic green sheets with electrode patterns formed thereon are laminated in the process of laminating ceramic green sheets and a void matrix to create an inkjet head. It is possible to obtain an inkjet head that integrally incorporates a laminated actuator that can be driven at low voltage. The built-in laminated actuator is integrated with the wall of the ink chamber to form a diaphragm for generating pulse pressure. It has been confirmed that a diaphragm having such a structure is extremely effective for increasing the speed and stabilizing the inkjet operation, since the response is extremely fast and a strong pressure pulse can be obtained. Furthermore, by integrating the laminated actuator, there is almost no need to consider problems such as variations in the bonding state or misalignment of the bonding position, making it possible to obtain an inkjet head with uniform ink ejection characteristics. .

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a perspective view including a partial cross-sectional view of an embodiment of a ceramic inkjet head according to the first invention of the present application. Ink is guided from an external ink reservoir (not shown) to the connection port 105 through a conduit or the like, and is then transferred to the common ink chamber 104.
The ink is then ejected from the nozzle 103 through the ink supply port 101 and the pressure chamber 102. In this embodiment, there are four ink paths from the common ink chamber 104 to the nozzle 103.
Although a four-nozzle head formed in horizontal rows is shown, the number of nozzles may be selected arbitrarily to satisfy the required recording speed. This inkjet head is entirely made of a ceramic material having electromechanical conversion properties, except for the electrode material. In FIG. 1, the head is shown to have a laminated structure of thin ceramic plates, which can be composited using multiple types of ceramic materials having electromechanical transducing properties. If the entire structure is made of the same ceramic material, the boundaries between the ceramic materials of each layer are integrated and cannot be identified. In FIG. 1, the ink chamber 102
The upper wall of is comprised of a plurality of ceramic layers 106. Although this example shows the case of four layers, the number of layers is not limited to this, and the number of layers can be arbitrarily selected depending on the thickness of the layers and the area of the electrodes. An electrode is formed on the upper surface of each ceramic layer 106. These electrodes consist of a drive electrode 107 for deforming the wall of the ink chamber, and an extraction electrode for connecting the drive electrode 107 to a drive circuit (not shown). The drive electrodes 107 are formed in exactly the same pattern on every surface of the ceramic layer 106 and are arranged so as to overlap in the vertical direction. - On the other hand, the extraction electrodes are different from the odd-numbered layers as shown in FIGS. 2(a) and 2(b), respectively. That is, as shown in FIG. 2(a), the electrode patterns of the first and third layers from the side closest to the ink chamber electrically connect each drive electrode 107 and are further connected to an external drive circuit. Sudame extraction electrodes 108 and 109
It has become a thing that has. In addition, Fig. 2(b) shows the second
This figure shows the electrode patterns of the second and fourth layers, and has a shape in which lead-out electrodes 110 for connecting to external drive circuits individually extend from the drive electrodes 107. The two electrode patterns shown in Figure 2 are as shown in Figure 3.
They are stacked alternately in the vertical direction. The electrodes of the odd and even layers are electrically connected at electrode terminal portions 111 and 112 at the tips of lead wires 109 and 110, respectively. In this embodiment, this connection is made in the stacking direction as follows. That is, a through hole 113 that penetrates the ceramic layer is formed in the central portion of the electrode terminal portions 111 and 112, and these holes are electrically conductive into the through hole before or after sintering the ceramic layer stack. Electrical connection is obtained by filling with paste.

In order to make the electrode laminated portion function as a laminated actuator, it is necessary to polarize the ceramic layer between the electrodes in advance. This polarization is performed according to the same method as in the case of conventional laminated actuators, but in the case of this embodiment, it is performed by applying a predetermined high voltage for a short time between the two electrode terminal parts 111 and 112. . As a result, the portion of the ceramic layer sandwiched between the drive electrodes 107 is polarized in a direction perpendicular to the electrodes, and the direction of polarization is reversed for each layer.

Next, a method for manufacturing an inkjet head according to the second invention of the present application will be described in detail with reference to the drawings.

FIGS. 4(a), (b), (c), (d), and (e) show an example of the manufacturing method according to the present invention, from the formation of a cavity matrix to the shape of the flow path to sintering. It is a process diagram for explaining the process up to. The formation of the vacancy matrix begins with the fourth step.
As shown in Figure (a), a photosensitive resin sheet 116 made by uniformly applying a photosensitive resin 115 to a predetermined thickness on a carrier film 114 such as a polyester film is placed on a photosensitive resin sheet 116 that has the same shape as the flow path. A photomask 117 with a pattern formed thereon is placed on top of the photomask 117, and light is irradiated to perform exposure. next,
As shown in FIG. 4(b), a development process is performed to form a predetermined void matrix 118.

In the next lamination step shown in FIG. 4(e), ceramic green sheets are laminated so that the cavity matrix 118 is sandwiched therein. The ceramic green sheets used here are made into a slurry by mixing and dispersing ceramic powder with organic binders, plasticizers, solvents, etc. according to general methods, and are produced using widely known methods such as doctor blade method and casting method. It is prepared by applying a plastic film to a predetermined thickness onto a substrate such as a glass plate or a metal sheet using a coating method described above and drying it. After drying, the ceramic green sheet peeled from the substrate is punched or cut into a predetermined size and shape, and if necessary, through holes are formed by punching or surface electrodes are formed by printing with conductive paste. Let's do it. In this embodiment, the different electrode patterns 119a and 1 shown previously in FIGS. 2(a) and 2(b) are used.
Two types of green sea with 19b formed on the surface) 12
Two sheets of each of 0a and 120b are alternately stacked. These green sheets having electrodes on their surfaces further have a through hole 113 formed at a position corresponding to the center of the electrode terminal portions 111 and 112, as shown in FIG. 3 (11).

In FIG. 4(e), the green sheet 121 has no surface electrodes or through holes, but is made to have the same external dimensions as the green sheets 120a and 120b.

These green sheets 120a, 120b and 1
21 are laminated in a predetermined order in a press mold together with the hollow matrix mold 118 peeled from the carrier film, and further pressure is applied to integrate them as shown in FIG. 4(d). In this compression process p, heat is applied along with pressure as necessary. Due to this pressure bonding, the green sheet locally flows and deforms so as to completely envelop the pore matrix, resulting in the shape shown in FIG. 4(e).

The thus produced laminate 122 is cut into predetermined dimensions as required, and then subjected to binder removal treatment. That is, by slowly heating in an oxidizing atmosphere,
It decomposes and eliminates the resin that forms the pore matrix and the organic matter in the ceramic green sheet. Normally, these organic substances are completely decomposed and oxidized at a temperature of 500°C to 600°C, but if the temperature is suddenly increased, the laminate will be damaged. Therefore, by suppressing the temperature increase rate to 256 C/hour or less and maintaining the temperature at 500°C to 600°C for a sufficiently long time, the organic substances are completely disappeared. As a result,
The void matrix 118 inside the laminate 122 disappears, leaving behind voids to form ink channels.

The laminate 122 that has been subjected to the binder removal process is then fired at a predetermined temperature to become porcelain, and then cut into predetermined external dimensions as necessary, and the nozzle end face is polished to form an inkjet head. can get.

The ceramic powder that makes up the green sheet is P
A piezoelectric material based on bTiO3-PbZrO3 was used. As the electrode material, a conductive paste with an Ag/Pd ratio of 70/30 (weight ratio) was used. An acrylic photocurable resin was used as the photosensitive resin for the pore matrix, and after exposure to ultraviolet light, development was performed using methyl ethyl ketone.

The pressure bonding between the ceramic green sheet and the void matrix is 11
The heating was carried out by applying a pressure of 250 kg/cm2 for 30 minutes at a heating temperature of 0°C.

The binder removal treatment was carried out by heating in air at a temperature increase rate of 5°C I hours and then holding at 500°C for 3 hours.

This treatment was followed by sintering at 1150°C for 2 hours in air.

The thickness of the green sheet and photosensitive resin is approximately 1
A 100p one was used. After sintering, the nozzle dimensions are approximately 8
0 pm square, and the height of the flow path inside the sintered body is approximately 8
It became 0pm. Under the above conditions, a head having the structure shown in FIG. 1 was manufactured as a prototype, and as a result, a stable ink ejecting operation was obtained. In addition, as a result of adjusting the pulse voltage so that the volume and flight speed of the ink droplets ejected from each of the four nozzles are the same, the variation in voltage value is within the range of 34V to 37V, and the ejection characteristics between each nozzle are extremely uniform. It was confirmed that it is good for

For comparison, we also prototyped an inkjet head with half the number of laminated electrodes as in the embodiment shown in Figure 1, that is, two layers.
The applied voltage required to perform stable ink jetting with uniform characteristics is large, ranging from 55 V to 70 V, and the range of fluctuation has also widened.

(Effects of the Invention) As described above, according to the manufacturing method of the invention, a ceramic inkjet head that integrally incorporates a laminated actuator in which a large number of electromechanical transducers are laminated in the thickness direction was obtained. Compared to the conventional method in which laminated actuators are assembled as individual parts, the positional accuracy of the laminated actuators can be improved, and an inkjet head with excellent uniformity of jetting characteristics can be obtained. Moreover, it does not require any skill in terms of manufacturing technology, is easy to manufacture, and has excellent mass productivity. This has made it possible to significantly reduce device costs. Furthermore, by using a laminated actuator, the drive voltage can be significantly reduced, the drive circuit becomes simpler and reliability is improved, and the cost of the -layer can be reduced.

[Brief explanation of the drawing]

(Includes Fig. 1 is a perspective view including a partial sectional view of an embodiment of the ceramic inkjet head according to the invention in Box 1, and Fig. 2 is an odd-numbered layer and an even-numbered layer of the laminated electrode layer of the inkjet head according to the invention in Box 1. 3 is a perspective view showing an example of the laminated state of electrodes in an inkjet head according to the invention in Box 1, and FIG. 4 is a manufacturing method according to the invention in Box 2. It is a process diagram showing an example of the manufacturing process of 101... Ink supply port, 102... Pressure chamber, 10
3... Nozzle, 104... Common ink chamber, 105...
...Connection port, 106...Ceramic layer, 107...
Drive electrodes, 108, 109 and 110... Extraction electrodes, 111 and 112...- Electrode terminal portion, 113.
...Through hole, 114...Carrier film, 1
15... Photosensitive resin, 116... Photosensitive resin sheet, 117... Photomask, 118... Hole matrix mold,
119a and 119b --- electrode pattern, 120a
and 120b... green sheet, 121... green sheet, 122-... laminate,

Claims (1)

[Scope of Claims] 1) A flat ceramic body made of a ceramic material having electromechanical conversion characteristics and in which an ink flow path communicating from an ink supply port through a pressure chamber to a nozzle is formed; At least 3 at regular intervals inside the walls of the chamber
An electrode having a plurality of electrodes laminated in more than one layer, and configured such that odd-numbered electrodes and even-numbered electrodes among the plurality of electrodes can be electrically connected through through holes formed in the stacking direction of the electrodes. An inkjet head characterized by having a terminal portion. 2) The process of forming a photosensitive resin sheet to match the planar shape of the ink flow path that communicates from the ink supply port through the pressure chamber to the nozzle to create a cavity matrix, and the process of molding the photosensitive resin sheet from a ceramic material with electromechanical conversion characteristics. forming a first electrode having an electrode terminal portion having a through hole on a green sheet using a conductive paste; and forming a second electrode having an electrode terminal portion having a through hole on the green sheet using a conductive paste. A step of forming using a conductive paste, and applying the void matrix and the green to a multilayer electrode layer formed by alternately laminating at least three or more layers of two types of green sheets on which the first and second electrodes are formed. A step of forming a laminate by laminating and press-bonding the sheets, and filling the through holes formed in the electrode terminal portions with conductive paste to electrically connect the first electrodes and the second electrodes in the stacking direction. A method for manufacturing a ceramic inkjet head, comprising the steps of: connecting the laminate to the laminate; and sintering the laminate.