JPH0796301B2 - Ceramic inkjet head and method of manufacturing the same - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet head used in various printers and facsimile machines and a method for manufacturing the same, and more particularly, to a pulse pressure applied to ink using an electromechanical conversion material. The present invention relates to a drop-on-demand type ink jet head that is caused to act and eject ink, and a manufacturing method thereof.

(Prior Art) A diaphragm method is widely known as a method of applying pulse pressure to ink in an on-demand type inkjet. That is, a flat plate-shaped electromechanical conversion element formed in a rectangular shape or a circular shape is attached to a plate such as metal or glass forming the wall of the ink chamber in the inkjet head to form a diaphragm. When the electromechanical conversion element is contracted and deformed in the surface direction by applying a voltage in the thickness direction, the wall of the ink chamber forming the diaphragm bends toward the ink chamber. As a result, the pulse pressure acts and the ink in the ink chamber is pushed out of the ink chamber.

(Problems to be Solved by the Invention) In the pulse pressure generating means, it is important to attach the electromechanical conversion element to a predetermined position of the ink chamber wall precisely and with sufficient adhesive strength. However, since the electromechanical conversion element is fixed to the outside of the ink chamber wall,
It was difficult to accurately fix the electromechanical conversion element at a position corresponding to the ink chamber inside the wall. Further, strict process control is carried out in order to always reproduce the thickness and adhesive strength of the adhesive layer of the adhesive portion within the specified range, but it is still difficult to suppress the variation in the ink ejection characteristics due to the variation in the adhesive state, It has been strongly desired to remove such an adhesion process.

Further, the pressure acting on the ink by the pulse pressure generating means and the volume of the ink ejected from the nozzle depend on the voltage value applied to the electromechanical conversion element. In the conventional on-demand type inkjet head, the voltage value of the applied pulse needs to be as high as 50V to 300V in order to apply a sufficiently large pressure to the ink and eject the required ink volume from the nozzle. . But,
From the viewpoint of high reliability or low price of the drive circuit
It was strongly desired to reduce the voltage to 50 V or less.

As a means for realizing the low voltage, a so-called laminated actuator is known in which a large number of electromechanical conversion elements having a small thickness and a narrow electrode interval in the thickness direction are laminated in the thickness direction. By adhering this laminated actuator to the outside of the wall of the ink chamber, it is expected to realize a drop-on-demand type ink jet head that can be driven at a low voltage. The problems such as the difficulty of always fixing the laminated actuator with high accuracy and the variation in the ink ejection characteristics depending on the bonding state remain unsolved.

(Means for Solving the Problems) According to the first invention of the present application, an ink flow path is formed which is made of a ceramic material having electromechanical conversion characteristics and which communicates with the nozzle from the ink supply port through the pressure chamber. Of a plurality of ink flow paths, each ink flow path being parallel to the ink flow path and arranged at regular intervals in the thickness direction of the ceramic body forming the wall of the pressure chamber. A first electrode group having one shaped electrode on the outer surface of the ceramic body as an outer electrode and at least two inner electrodes on the inside, and comprising an outer electrode and an even numbered inner electrode counted from the outer surface side. Through the electrode terminal portion into the first through hole, and into the second electrode group (where the electrode is 1
(Including the case of one sheet) is connected to the second through hole through the electrode terminal portion, and either one of the first or second electrode group has a shape in which electrodes existing in the same plane are connected by the extraction electrode. A ceramic ink jet head is obtained which is characterized in that the ceramic bodies which are made of the above electrodes and which are adjacent to each other with the electrodes sandwiched therebetween are polarized by 180 ° opposite to each other in the thickness direction.

According to the second invention of the present application, a step of forming a photosensitive resin sheet in accordance with a planar shape of an ink flow path communicating from an ink supply port to a nozzle through a pressure chamber to form a hole master block, Forming a first electrode having a lead electrode having an electrode terminal portion using a conductive paste on a green sheet made of a ceramic material having electromechanical conversion characteristics to form a first electrode green sheet; Forming a second electrode having a lead-out electrode having an electrode terminal portion on the second electrode using a conductive paste to form a second electrode green sheet; and the two types of electrode terminal portions of the first and second electrode green sheets. Forming the first and second through holes at the center of and the position corresponding to the center,
The hole matrix on at least one green sheet,
At least 3 of the first and second electrode green sheets are alternately arranged so that a surface having no electrode on the hole master is in contact with the hole master and the electrode is arranged at a position where the pressure chamber is formed.
A step of stacking more than one layer and press-bonding to form a stacked body; filling the first and second through holes formed in the electrode terminal portion with a conductive paste; A step of connecting the hole and the second electrode to a second through hole; and a step of sintering the laminated body in an oxidizing atmosphere to decompose and eliminate the hole matrix to form a hole. A voltage is applied between the electrodes formed in the through hole so that the ceramic material between the first and second electrodes is directed from one of the first and second electrodes to the other perpendicular to the electrodes. The method for manufacturing a ceramic ink jet head is characterized by comprising the steps of:

(Operation) According to the present invention, low voltage driving is possible by stacking a large number of ceramic green sheets having electrode patterns in the process of forming an inkjet head by stacking ceramic green sheets and hole masters. It is possible to obtain an ink jet head integrally incorporating such a laminated actuator. The built-in laminated actuator is
A diaphragm for generating pulse pressure is formed integrally with the wall of the ink chamber. The diaphragm with such a structure
It has been confirmed that the response is extremely fast and the pressure pulse is strong, which is extremely effective for speeding up and stabilizing the inkjet operation. further,
By incorporating the laminated actuator integrally, it is almost unnecessary to consider the problems such as the variation of the adhesion state and the deviation of the adhesion position, and it becomes possible to obtain an inkjet head having uniform ink ejection characteristics.

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

FIG. 1 is a perspective view including a partial sectional view of an embodiment of a ceramic ink jet 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 by a conduit or the like, and is ejected from the nozzle 103 through the common ink chamber 104, the ink supply port 101 and the pressure chamber 102. In this embodiment, the common ink chamber 104
Although a four-nozzle head in which four ink paths reaching the nozzles 103 are formed in parallel is shown, the number of nozzles is arbitrarily selected so as to satisfy the required recording speed. Except for the electrode material, the inkjet head is entirely made of a ceramic material having electromechanical conversion characteristics.
In FIG. 1, the head is shown to have a laminated structure of thin ceramic plates, and can be composited using a plurality of types of ceramic materials having electromechanical conversion characteristics. When the whole is made of the same ceramic material, the boundaries between the ceramic materials between the layers cannot be integrally identified. In FIG. 1, the upper wall of the pressure chamber 102 comprises a plurality of ceramic layers 106. Although this embodiment shows the case of four layers, the present invention is not limited to this.
The number of stacked layers is arbitrarily selected according to the thickness of the layers and the electrode area. Electrodes are formed on the upper surface of each ceramic layer 106. These electrodes are composed of a drive electrode 107 for deforming the wall of the pressure chamber 102 and an extraction electrode for connecting the drive electrode 107 to a drive circuit (not shown). The drive electrodes 107 are formed in the same pattern on the surface of any ceramic layer 106, and are arranged so as to overlap in the vertical direction. On the other hand, the lead-out electrodes are different from the odd-numbered layers as shown in FIGS. 2 (a) and 2 (b). That is, the electrode patterns of the first layer and the third layer counted from the side close to the pressure chamber member 102 electrically connect the drive electrodes 107 as shown in FIG. It has lead-out electrodes 108 and 109 for connecting to. Also, the second
FIG. 2B shows the electrode patterns of the second layer and the fourth layer, and the lead electrodes 110 for connecting to the external drive circuit are individually extended from the drive electrodes 107. The two electrode patterns shown in FIG. 2 are alternately stacked vertically as shown in FIG. The electrodes of the odd-numbered layers and the electrodes of the even-numbered layers are electrically connected at the electrode terminal portions 111 and 112 at the tips of the lead lines 109 and 110, respectively. This connection is made in the stacking direction as follows in this embodiment. That is, in the electrode terminal portions 111 and 112, a through hole 113 penetrating the ceramic layer is formed in the central portion.
Is formed, and the through holes are filled with a conductive paste before or after sintering the laminated body of the ceramic layers to obtain an electrical connection.

In order for the electrode laminated portion to function as a laminated actuator, it is necessary to pre-polarize the ceramic layer between the electrodes. This polarization is performed according to a method similar to that of the conventional laminated actuator, but in the present embodiment, it is performed by applying a predetermined high voltage for a short time between the two electrode terminal portions 111 and 112. . As a result, the portion of the ceramic layer sandwiched by the drive electrodes 107 is polarized in the direction perpendicular to the electrodes, and the direction of polarization is opposite in each layer.

The inkjet head can be driven by applying a voltage pulse between the electrode terminal portions 111 and 112.

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

FIGS. 4 (a), (b), (c), (d) and (e) show, as an embodiment of the manufacturing method according to the present invention, from the formation of the hole master mold according to the shape of the flow path to the sintering. FIG. 6 is a process chart for explaining a process up to and including FIG. The fourth step is the formation of the hole matrix.
As shown in FIG. (A), the same flow path shape is formed on a photosensitive resin sheet 116 which is prepared by uniformly coating a photosensitive resin 115 with a predetermined thickness on a carrier film 114 such as a polyester film. Photomask 117 with the pattern of
And irradiate with light to perform exposure. Next, as shown in FIG. 4B, a developing process is performed to form a predetermined hole master 118.

In the next laminating step shown in FIG. 4 (c), the ceramic green sheets are laminated so that the hole master 118 is sandwiched inside. The ceramic green sheet used here is a mixture of ceramic powder and an organic binder, a plasticizer, a solvent, etc. mixed and dispersed according to a general method, and is widely known by a doctor blade method, a casting method or the like. It is prepared by applying a predetermined thickness on a substrate such as a plastic film glass plate or a metal sheet by the applied method and drying. After drying, the ceramic green sheet peeled from the substrate is punched or cut into a desired size and shape, and if necessary, through holes are formed by punching or surface electrodes are formed by printing with a conductive paste. To do. In this embodiment, two kinds of green sheets 120a and 120b having different electrode patterns 119a and 119b shown in FIGS. 2 (a) and 2 (b) are formed on the surface.
Are alternately stacked in pairs of two. The green sheet having electrodes on the surface thereof further has through holes 113 formed at positions corresponding to the centers of the electrode terminal portions 111 and 112, as shown in FIG.

In FIG. 4 (c), the green sheet 121 does not have surface electrodes or through holes, but the outer dimensions are the same as those of the green sheets 120a and 120b. These green sheets 120a, 120b and 121 are laminated in a predetermined order in a die for pressure bonding together with the hole mother die 118 peeled from the carrier film, and further pressure is applied, as shown in FIG. Integrate as shown. In this pressure bonding step, heat is applied together with pressure as necessary. By this pressure bonding, the green sheet locally flows and is deformed so as to completely enclose the hole matrix, and the shape becomes as shown in FIG. 4 (e).

The laminated body 122 thus produced is cut into a predetermined size if necessary, and then subjected to a binder removal treatment. That is, by slowly heating in an oxidizing atmosphere, the resin forming the pore master mold and the organic substances in the ceramic green sheet are decomposed and disappeared. Usually these organics
It decomposes completely and oxidizes at temperatures of 500 ° C to 600 ° C, but if the temperature rises rapidly, the laminate will be damaged. For this reason,
Temperature rising rate is kept below 25 ℃ / hour, and further 500 ℃
By keeping the temperature at 600 to 600 ° C for a long time, organic substances are completely eliminated. As a result, the hole matrix 1 inside the laminate 122 is
18 disappears, and the trace becomes a hole to form an ink flow path.

The laminated body 122 that has been subjected to the binder removal treatment is subsequently fired at a predetermined temperature to be porcelain, and then cut to have a predetermined outer dimension as necessary, and an inkjet head is provided by polishing the end face of the nozzle. can get.

As the ceramic powder that makes up the green sheet, Pb
Using piezoelectric materials TiO ₃ -PbZrO ₃ series. As the electrode material, a conductive paste having an Ab / Pd ratio of 70/30 (weight ratio) was used. An acrylic photocurable resin was used as the photosensitive resin for the hole matrix, and after exposure with ultraviolet rays, development was performed using methyl ethyl ketone.

Crimping between the ceramic green sheet and the hole matrix is 110
Under a heating temperature of ° C, a pressure of 250 kg / cm ² was applied for 30 minutes.

The binder removal treatment was performed by heating in air at a temperature rising rate of 5 ° C./hour and then holding at 500 ° C. for 3 hours. Sintering following this treatment was carried out in air at 1150 ° C. for 2 hours.

The thickness of the green sheet and the photosensitive resin are both about 10
The one with 0 μm was used. After sintering, the nozzle size is about 80μ
The angle is m square, and the height of the flow path inside the sintered body is about 80 μm.
Became. As a result of trial manufacture of the head having the structure shown in FIG. 1 under the above conditions, stable ink ejection operation was obtained. Also, 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 uniform, the variation in the voltage value is within the range of 34V to 37V, and the uniformity of the ejection characteristics between each nozzle is extremely high. It was confirmed to be good for

For comparison, as a result of trial production of an ink jet head having the number of laminated electrodes half that of the embodiment of FIG. 1, that is, two layers,
The applied voltage required to carry out stable and uniform ink ejection was large from 55V to 70V, and the range of variation was widened.

(Effects of the Invention) As described above, according to the manufacturing method of the present invention, the ceramic ink jet head integrally including the laminated actuator in which a large number of electromechanical transducers are laminated in the thickness direction is obtained. As compared with the case of assembling the laminated actuator as an individual component in the conventional method, the positional accuracy of the laminated actuator can be further increased, and an inkjet head excellent in uniformity of ejection characteristics was obtained. In addition, the manufacturing technique does not require any skill, can be easily manufactured, and is excellent in mass productivity. Therefore, the device cost can be greatly reduced. Further, by using the laminated actuator, the driving voltage can be widened, the driving circuit is simplified, the reliability is improved, and the cost can be further reduced.

[Brief description of drawings]

FIG. 1 is a perspective view including a partial sectional view of an embodiment of a ceramic inkjet head according to the first invention of the present application, and FIG. 2 is an electrode pattern in odd layers and even layers between laminated electrodes of an inkjet head according to the first invention of the present application. FIG. 3 is a perspective view showing one embodiment of a laminated state of electrodes in an inkjet head according to the first invention of the present application, and FIG. 4 is a manufacturing process of a manufacturing method according to the second invention of the present application. 10 ... Ink supply port, 102 ... Pressure chamber, 103 ... 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 part, 113 ...
Through-hole, 114 ... Carrier film, 115 ... Photosensitive resin, 116 ... Photosensitive resin sheet, 117 ... Photomask, 118 ... Hole master, 119a and 119b ... Electrode pattern, 120a and 120b ... ... green sheet, 121 ... green sheet, 122 ... laminated body.

Claims (2)

[Claims] 1. A ceramic ink jet head, which is made of an integrally sintered ceramic material having electromechanical conversion characteristics, and in which an ink flow path communicating with a nozzle from an ink supply port through a pressure chamber is formed. , A plurality of ink channels, each ink channel being parallel to the ink channel and having planar electrodes arranged at regular intervals in the thickness direction of the ceramic body forming the wall of the pressure chamber The first electrode group, which has one external electrode on the outer surface and at least two internal electrodes on the inside, and which is composed of the external electrodes and the even numbered internal electrodes counted from the outer surface side, is connected via the electrode terminal portion. A second electrode group (including the case where the number of electrodes is one) composed of odd-numbered internal electrodes counted from the outer surface side is connected to the second through hole through the first through hole. Either one of the first or second electrode group is composed of electrodes in a shape in which electrodes existing in the same plane are connected by extraction electrodes, and adjacent ceramic bodies sandwiching the electrodes are 180 ° opposite to each other in the thickness direction. A ceramic ink jet head characterized by being polarized. 2. A process of forming a hole master by molding a photosensitive resin sheet in accordance with the planar shape of an ink flow path communicating with a nozzle from an ink supply port through a pressure chamber, and having electromechanical conversion characteristics. Forming a first electrode having a lead electrode having an electrode terminal portion on a green sheet made of a ceramic material with a conductive paste to form a first electrode green sheet; and having an electrode terminal portion on the green sheet. Forming a second electrode having a lead electrode using a conductive paste to form a second electrode green sheet, and a step of forming a second electrode green sheet at the center and the center of the two types of electrode terminal portions of the first and second electrode green sheets. First and second in corresponding positions
Forming a through hole, and forming the hole master on at least one green sheet, the surface without electrodes being in contact with the hole master on the hole master, and forming a pressure chamber. A step of alternately stacking at least three layers of the first and second electrode green sheets so that the electrodes are arranged at positions and press-bonding to form a laminated body; and the first electrode formed on the electrode terminal portion. And a step of filling the second through hole with a conductive paste and connecting the first electrode to the first through hole and the second electrode to the second through hole, respectively, and the laminated body in an oxidizing atmosphere. A step of decomposing and eliminating the hole matrix by sintering to form holes, and applying a voltage between the electrodes formed in the through hole to the ceramic between the first and second electrodes. The material is one of the first and second electrodes Method for producing a ceramic ink jet head is characterized in that towards the other consisting of a step of decomposing in a direction perpendicular to the electrode.