JP2003311983A - Ink jet recording head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the trouble that characteristics of an ink jet recording head decrease because a solder flows out to discrete electrodes of the ink jet recording head when the ink jet recording head and a power supply terminal for impressing a voltage to the ink jet recording head are joined by the solder. <P>SOLUTION: Discrete electrodes are formed of gold at positions opposite to ink chambers of the ink jet recording head. At the same time, a base layer is formed of a metal with a poor wettability to the solder at an end part of the discrete electrode. An electrode lead-out layer formed of gold is set on the base layer via an interval to the discrete electrode. The electrode lead-out layer and the power supply terminal are electrically connected by the solder. <P>COPYRIGHT: (C)2004,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording head that prints characters and images by discharging ink by utilizing the bending displacement of a piezoelectric ceramic. 2. Description of the Related Art In recent years, a recording head used in a recording apparatus for printing characters and images has been changed from an impact type such as a wire dot printer to an ink jet type due to advantages such as high image quality and low noise. Are coming. Among such ink jet systems, an ink jet recording head utilizing the bending displacement of a piezoelectric ceramic has rapidly become widespread because it can be downsized and a printing speed can be increased. FIGS. 2 and 3 show a conventional ink jet recording head. In the figure, (a) is a sectional view of the ink jet recording head, and (b) is a front view of (a). FIG. 3 is a YY cross section of FIG. [0004] The ink jet recording head 20 includes a partition 7.
An actuator 15 is formed on the back surface of the flow path member 7 having a plurality of ink chambers 7a partitioned by b, ink supply holes (not shown) communicating with the ink chambers 7a, and ink discharge holes 8. That is, the actuators 15 are arranged in a plurality of rows and columns. The actuator 15 includes a piezoelectric ceramic plate 11, a common electrode 13, and an individual electrode 12, and the piezoelectric ceramic plate 11, the common electrode 13 and the common electrode 13 are formed in the opening of the ink chamber 7a. Of the piezoelectric ceramic plate 11 and the common electrode 13 so as to face the respective ink chambers 7a.
2 are formed. The individual electrode 12 is provided in the ink chamber 7.
A connection portion 14 is drawn out of a region outside the region opposing a. The connection portion 14 is connected to the power supply terminal 6 shown in FIG. When a voltage is applied from the power supply terminal 6 and a voltage is applied, the piezoelectric ceramic plate 11 of one layer sandwiched between the individual electrode 12 and the common electrode 13 contracts due to dimensional displacement, but does not contribute to dimensional displacement. Of the piezoelectric ceramic plate 11 and the common electrode 13 are bent toward the ink chamber 7a, pressurize the ink in the ink chamber 7a, and discharge the ink droplets from the ink discharge holes 8. It has become. At this time, if the rigidity of the individual electrode 12 is high, the amount of deflection of the piezoelectric ceramic plate 11 becomes small, so that the thickness of the individual electrode 12 is preferably made as small as possible. However, when the electrode is thinned, the resistance value increases, the response decreases,
Since problems such as heat generation occur, gold having high conductivity is preferably used for the individual electrodes 12. Accordingly, in the solder joining between the connecting portion 14 and the power supply terminal 6, the connecting portion 14 is made of a metal having high wettability with solder in order to obtain sufficient connection strength between the connecting portion 14 and the solder. Are preferably used. However, with the recent increase in the density of the ink jet recording head 20, it is necessary to arrange the actuators 15 arranged in a plurality of rows and columns in close proximity to each other. A space for joining between the power supply terminal 14 and the power supply terminal 6 was not obtained, and the joining operation was difficult. [0009] As shown in FIG.
When soldering is performed in a small space in the vicinity, since the solder and gold have good wettability, the solder 5 passes over the connection portion 14 to cause electrode cracking. As a result, the individual electrodes 12 on the ink chamber 7a And the dimensional displacement of the piezoelectric ceramic plate 11 is hindered. On the other hand, if the amount of solder is reduced to solve the problem, the joint strength between the connecting portion 14 and the power supply terminal 6 is reduced, and a problem has arisen in that the power supply terminal 6 is disconnected due to peeling. An object of the present invention is to provide a solder joint between a connection electrode and a power supply terminal of an ink jet recording head without lowering the bonding strength between the connection electrode and the solder and reducing the amount of flexural displacement of the piezoelectric ceramic plate. An object of the present invention is to provide an ink jet recording head capable of preventing solder from flowing out. In view of the above problems, the present invention has been made in consideration of the above problems, and has a flow path member having a plurality of ink chambers partitioned by a plurality of partition walls; An actuator for pressurizing the ink in the ink chamber; and an ink ejection hole communicating with each of the ink chambers. The actuator includes a piezoelectric ceramic plate, a common electrode embedded in the piezoelectric ceramic plate, and the piezoelectric ceramic plate. An individual electrode made of gold formed at a position facing each of the ink chambers above, and an end portion of the individual electrode having an underlayer made of a metal having poor wettability with solder; An electrode extraction layer made of gold is provided on the upper surface at a distance from the individual electrode, and the electrode extraction layer and the power supply terminal are connected by solder. Embodiments of the present invention will be described below. Note that components having the same configuration as the conventional technology are denoted by the same reference numerals. FIG. 1 is a view showing an example of the ink jet recording head of the present invention. (A) is a cross-sectional view of the inkjet recording head, (b) is a front view of (a), and (c) is a cross-sectional view taken along line XX of (b). The ink jet recording head 10 has a partition 7b.
An actuator 16 is formed on the back surface of the flow path member 7 having a plurality of ink chambers 7a partitioned by the above, an ink supply hole (not shown) communicating with the ink chambers 7a, and ink discharge holes 8. That is, the actuator 16 includes the piezoelectric ceramic plate 1, the common electrode 3, the individual electrode 2, and the connection electrode 4,
A laminate of the piezoelectric ceramic plate 1 and the common electrode 3 is joined to the opening of the ink chamber 7a, and individual electrodes 2 are provided on the laminate of the piezoelectric ceramic plate 1 and the common electrode 3 so as to correspond to each ink chamber 7a. A connection electrode 4 is connected to an end of the individual electrode 2. The connection electrode 4 has an underlayer 4b made of a metal having poor wettability with solder and an electrode extraction layer 4a formed on the underlayer 4b. The electrode extraction layer 4a is located at a position deviating from the drive region of the actuator 16. The individual electrode 2
It is formed at a position separated from Thus, when the electrode extraction layer 4a and the power supply terminal 6 are joined by soldering, it is possible to prevent the solder 5 from flowing out at a portion where the underlayer 4b made of metal having poor wettability with the solder 5 is exposed. Thus, the flow of the solder 5 to the individual electrodes 2 on the ink chamber 7a can be prevented, and the ink jet recording head 10 can be driven satisfactorily. Here, if the separation size between the electrode extraction layer 4a and the individual electrode 2 is too small, the molten solder 5 at the time of solder connection flows over the underlayer 4b of the connection electrode 4 and flows onto the individual electrode 2, so that the electrode It is better that the separation dimension between the extraction layer 4a and the individual electrode 2 is large, specifically, 50 μm.
It is desirable to take the above. When a voltage is applied from the power supply terminal 6 and a voltage is applied, the piezoelectric ceramic plate 1 sandwiched between the individual electrode 2 and the common electrode 3 shrinks due to dimensional displacement. Because the board 1 is restrained,
The laminate of the piezoelectric ceramic plate 1 and the common electrode 3 is the ink chamber 7
It is deformed so as to bend toward the a side. As the piezoelectric ceramic plate 1, a piezoelectric material mainly composed of lead zirconate titanate, lead titanate, barium titanate or the like, particularly a material having a large piezoelectric constant and large deformation called a soft material is used. The thickness of the individual electrodes 2 is not more than 1 μm, preferably not more than 0.1 μm, so that the characteristics of the piezoelectric ceramic plate 1 are not affected by heat treatment at the time of formation and the dimensional displacement of the piezoelectric ceramic plate 1 is not hindered. The thickness needs to be 1 to 0.5 μm, and gold which can provide sufficient conductivity even when the thickness is reduced is used. As the underlayer 4b, a material which does not affect the characteristics of the piezoelectric ceramic plate 1 due to heat treatment at the time of formation and has conductivity and poor wettability with solder is used. For the extraction layer 4a, gold having good wettability with solder is used. The thickness of the underlayer 4b is generally about 1 to 5 μm so as not to cause so-called “electrode cracking” that diffuses into the solder 5 during solder bonding. Further, the thickness of the electrode extraction layer 4a may be any thickness as long as sufficient conductivity can be obtained. However, since it is cost-effective to form the electrode extraction layer 4a in the same process as the individual electrode 2, the thickness is the same as that of the individual electrode 2. That is common. Here, the poor wettability of the solder 5 means that the solder melted at the time of joining is hardly adapted to the electrode material, and palladium, platinum, copper, nickel, Aluminum, chromium and their alloys are available. Further, silver itself has better solder wettability than gold, but easily forms an oxide film or a sulfide film under a certain environment, and the surface on which the film is formed has lower solder wettability than gold. It is known that this is the case, and the present invention is not limited to this, and an oxide film may be formed on a metal having good solder wettability to deteriorate wettability. As the material of the common electrode 3, silver-palladium, silver-platinum alloy, or the like is used because the common electrode 3 is fired integrally with the piezoelectric ceramic 1. Since the thickness of the common electrode 3 has little effect on the dimensional displacement of the piezoelectric ceramic plate 1, it is generally about 1 to 5 μm. For the flow path member 7, ceramics such as zirconia and alumina and metals such as stainless steel are generally used. Next, a method of manufacturing the ink jet recording head 10 shown in FIG. 1 will be described. First, a tape made of a piezoelectric ceramic material and an organic composition is formed by a general tape forming method such as a roll coater method or a doctor blade method. Next, if necessary, the common electrode 3 is formed on the tape by a printing method or the like, laminated, pressed and adhered to form a laminate, and then the organic composition in the tape is heated at 300 to 800 ° C. Burn off, 900 to 15 in lead atmosphere
The piezoelectric ceramic plate 1 is fired at 00 ° C., and the piezoelectric ceramic plate 1 is sintered simultaneously with the firing of the common electrode 3 to obtain a piezoelectric ceramic laminate.
Next, an underlayer 4b is formed on the piezoelectric ceramic laminate by a printing method or the like and baked, and then the individual electrodes 2 and the electrode extraction layer 4a are formed and baked by a printing method or the like. next,
Using ceramics such as zirconia, a green sheet having holes serving as ink ejection holes 8 and a green sheet having holes serving as ink chambers 7a are laminated, pressed, and then integrally fired to produce a flow path member 7. The piezoelectric ceramic laminate obtained by baking the individual electrode 2, the underlayer 4b, and the electrode extraction layer 4a is joined to the obtained flow path member 7 with an adhesive or the like to obtain an ink jet recording head 10. After that, it is connected to the power supply terminal 6 for applying a voltage by the solder 5. Here, an ink jet recording head of the present invention and a conventional ink jet recording head were prepared and connected to a power supply terminal by soldering. In order to evaluate the ink jet recording head, a voltage is applied from a power supply terminal to apply a voltage to polarize the piezoelectric ceramic plate, and then the ink is filled in the ink chamber, a voltage is applied using the power supply terminal, and the ink droplet is applied. The ink droplets were ejected, and the ejection speed of ink droplets was measured using a high-speed camera, and comparison was made. EXAMPLE First, a lead zirconate titanate-based piezoelectric ceramic material and an aqueous acrylic solution were mixed to form a slurry, and a 30 μm-thick tape was formed using a roll coater. Next, using a 70:30 silver-palladium electrode paste, a common electrode having a thickness of 5 μm was formed on the tape by a printing method or the like, and the tape having no electrodes formed thereon was laminated on upper and lower layers to form a 120 kgf electrode. / Cm ² to form a laminated body, then burn off the acrylic component in the tape at 800 ° C, bake it in a lead atmosphere at 1100 ° C, and bake the common electrode and simultaneously sinter the piezoelectric ceramic plate. went. After firing, the thickness of each layer of the piezoelectric ceramic plate is 20μ.
m, and the thickness of the common electrode was 2 μm. Next, using a platinum electrode paste, a base layer of the connection electrode is formed by a printing method and baked at 950 ° C., and then, using an organic gold paste, the individual electrodes connected to the base layer and the individual electrodes are formed. Each electrode extraction layer was formed by a printing method so as not to be directly connected, and baked at 800 ° C. The thickness of the underlayer after baking was 2 μm, and the thickness of the electrode extraction layer of the individual electrode and the connection electrode was 0.3 μm. Next, using stainless steel, a flow path member in which a plate material having a hole serving as an ink ejection hole and a plate material having a hole serving as an ink chamber are formed,
The piezoelectric ceramic laminate having the individual electrodes, the underlayer, and the electrode extraction layer baked thereon was joined to the obtained flow path member, and the ink jet recording head No. 1 was formed. 1 was obtained. (Comparative Example) An ink jet recording head No. 1 was formed in the same manner as in the example except that a connection portion from which an individual electrode was drawn was formed without forming a base layer and an electrode extraction layer. 2 was obtained. As a result of evaluating the ink ejection from the 50 ink ejection holes for each ink jet recording head, the ink jet recording head No. 1 of the present invention was evaluated. The ink jet head ejected from No. 1 was good, with a small variation of 6 to 8 m / s, and the ink jet head no. 2, the speed of the ink under ejection was large, ranging from 2 to 8 m / s, and the ink ejection speed was low. After the ink ejection speed was evaluated, the power supply terminal was peeled off, and the ink jet recording head was observed. When the ink ejection speed of the conventional ink jet recording head was low, the solder flowed out and applied to the individual electrodes. Was observed. As described above, according to the present invention, an ink jet recording head that discharges ink using the bending displacement of a piezoelectric ceramic has a plurality of ink chambers partitioned by a plurality of partition walls. A flow path member, an actuator joined to the flow path member and configured to pressurize ink in each of the ink chambers, and an ink discharge hole communicating with each of the ink chambers; the actuator includes a piezoelectric ceramic plate; It has a common electrode buried in a ceramic plate, and an individual electrode made of gold formed at a position facing each ink chamber on the piezoelectric ceramic plate, and the end of the individual electrode has wettability with solder. An undercoat layer made of a metal having an inferior quality, and forming an electrode extraction layer made of gold on the underlayer at a distance from the individual electrodes, so that ink jet recording is possible. When the recording head and the power supply terminal are connected by solder, it is possible to prevent an outflow of the solder and obtain an ink jet recording head capable of excellent driving.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing an example of an ink jet recording head according to the present invention, (a) is a cross-sectional view, (b) is a front view,
(C) is a diagram showing a solder joint between the electrode extraction layer and the power supply terminal. FIGS. 2A and 2B are views showing an example of a conventional inkjet recording head, wherein FIG. 2A is a sectional view thereof, and FIG. 2B is a front view of FIG. FIG. 3 is a view showing a solder joint between a connection electrode and a power supply terminal of a conventional ink jet recording head. [Description of Signs] 1: Piezoelectric ceramic plate 2: Individual electrode 3: Common electrode 4: Connection electrode 4a: Electrode extraction layer 4b: Base layer 5: Solder 6: Power supply terminal 7: Flow path member 7a: Ink chamber 7b: Partition wall 8: Ink ejection hole 10: Ink jet recording head 16: Actuator

Claims (1)

Claims: 1. A flow path member having a plurality of ink chambers partitioned by a plurality of partition walls, an actuator joined to the flow path member and pressurizing ink in each of the ink chambers, The actuator has an ink ejection hole communicating with each ink chamber, and the actuator is formed at a position opposed to each ink chamber on the piezoelectric ceramic plate, a common electrode embedded in the piezoelectric ceramic plate, and the piezoelectric ceramic plate. And an underlayer made of a metal having poor wettability with solder at the end of the individual electrode. The underlayer is formed on the underlayer at a distance from the individual electrode. An ink jet recording head, comprising: an electrode extraction layer comprising: an electrode extraction layer; and a power supply terminal connected to the electrode extraction layer by soldering.