JPH10100421A - Manufacture of ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ink jet head in which the performance of a piezoelectric element can be derived sufficiently while suppressing internal stress due to bonding of different kind of material extremely by cutting a groove for separating bulk piezoelectric elements into individual drive elements down to an adhesive layer and the surface of a substrate member on the adhesive layer side thereby separating the piezoelectric element perfectly. SOLUTION: After confirming that the bonding strength of an adhesive is sufficient for operating a piezoelectric element 20 after it is separated perfectly, a groove us cut down to the upper layer of a substrate member 2 and the piezoelectric element 20 is separated perfectly thus removing internal residual stress in the piezoelectric element 20 and the substrate member 2. Subsequently, a reference surface 2a for assembling is formed by grinding the substrate member 2 with reference to the groove cut in the preceding process and a conductor FPC 60 applying a voltage for driving each split piezoelectric element 20 is soldered to the opposite electrodes thereof. An actuator is completed under that state and a head is completed by boding various parts and units furthermore.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a head of an ink jet printer for selectively depositing ink droplets on an image recording medium.

[0002]

2. Description of the Related Art Among non-impact printers whose market is expanding today, the principle is the simplest.
An ink jet printer is suitable for color printing. Among them, a so-called drop-on-demand (DOD) type ink jet printer that discharges ink droplets only at the time of dot formation is in use. As a representative head system in a DOD type ink jet printer, for example, Japanese Patent Publication No. 53-1
Kaiser type disclosed in Japanese Patent No. 2138,
There is a thermal jet type disclosed in Japanese Patent Publication No. 61-59914. Of these, Tokiko 53-1
The Kaiser type ink jet head described in Japanese Patent No. 2138 is difficult to miniaturize, and the Japanese Patent Publication No. 61-59911
The thermal jet head described in Japanese Patent No. 4 has a difficult problem that the ink is scorched because high heat is applied to the ink. As an ink jet head that simultaneously solves the above-mentioned defects, there is a type using a piezoelectric element having a piezoelectric distortion constant d ₃₃ (hereinafter, also referred to as “d ₃₃ mode type”). The d ₃₃ mode type ink jet head, use strips of piezoelectric material (the piezoelectric element), and one surface of the piezoelectric element, to form a respective electrode on opposite sides, between the electrodes of the piezoelectric strain element It has a general structure which gave piezoelectric strain constant d ₃₃ by polarized in the same direction as the direction of electric field. Then, the piezoelectric strain element to generate an electric field between the electrodes, by stretching in the thickness direction (d ₃₃ direction), so as to pressurize the ink pressure chamber. In a conventional actuator unit, a bulk-shaped piezoelectric element is bonded to a substrate member of a different material with a high-temperature curing type adhesive, and then grooves are formed so as to be divided into drive element units. Since the width of the driving element is small, in order to secure physical strength, the bulk piezoelectric element is not completely divided and the non-driving layer below the piezoelectric element is left connected.

[0003]

However, in the above-described structure, distortion occurs due to a difference in linear expansion coefficient between different materials of the piezoelectric element and the substrate member at the time of high-temperature bonding, resulting in a product in which internal stress remains. . If the internal stress remains, it may affect the displacement characteristics, insulation resistance characteristics, and the like of the piezoelectric element, increase the defective rate, and may further impair reliability.

[0004] It is an object of the present invention to solve this problem by adhering dissimilar materials to release residual internal stress.

[0005]

In order to achieve the above-mentioned object, the present invention provides a method of forming a groove for dividing a bulk piezoelectric element into drive element units so that the adhesive layer and the adhesive layer are completely divided. It was decided to cut into the surface layer on the adhesive layer side of the substrate member. Thereby, the internal stress generated by the adhesion between the different materials is almost completely released.

[0006]

Embodiments of the present invention will be described below. FIG. 1 is a sectional view of an ink jet head according to the embodiment. The pressure chamber plate 30 is made of an epoxy-based thermosetting plastic and has a groove-shaped pressure chamber 32. The pressure chamber 32 forms an ink liquid chamber in cooperation with a diaphragm 40 described later.
Reference numeral 20 denotes a piezoelectric element, which is a laminated piezoelectric element that generates a mechanical displacement for discharging ink by applying a voltage to both ends of the electrode. Reference numeral 40 denotes a diaphragm, which is made of nickel electroforming and has a role of forming an ink liquid chamber in cooperation with the liquid chamber plate 10 and transmitting displacement of the piezoelectric element 20 to the liquid chamber. The nozzle plate 10 is made of nickel electrocast, has a surface provided with water-repellent plating containing polytetrafluororetylene, and has a plurality of nozzle holes 12 for discharging ink.
2 is provided vertically on an extension line in the longitudinal direction. The operation of the ink jet head having the above configuration will be briefly described. When a drive voltage is applied to the piezoelectric element 20, the piezoelectric element 20 is displaced,
Pressure is applied to the ink in the pressure chamber 32 via the diaphragm 40. As a result, ink is ejected from the nozzle holes 12, and character symbols and the like are displayed on printing paper.

FIG. 3 is a front view of an actuator unit in which a conventional piezoelectric element 20 and a substrate member 2 are combined. In this state, the internal stress expressed by the warpage remains. FIG. 2 shows an actuator unit in which the piezoelectric element 20 of the present invention is completely divided. In this state, the warpage seen in FIG. 3 is eliminated, and the internal stress is almost completely released. Since there is little physical stress, the displacement characteristics, insulation resistance characteristics, and the like of the piezoelectric element are not easily reduced.

Next, the manufacturing process of the actuator unit according to the present invention will be described. FIG. 4 shows a process of bonding the substrate member 2 and the bulk piezoelectric element 20. First, a high-temperature curing type epoxy-based adhesive is applied on the substrate member 2 having a flatness of several μm or less by a screen printing method in an area equivalent to the bonding surface of the piezoelectric element 20. Next, the substrate member 2 and the piezoelectric element 20 having a flatness of the bonding surface of several μm or less are fixed with a jig capable of determining a positional relationship and applying a load for bonding the two without any gap. Place in oven at constant temperature for a time to completely cure the adhesive. Then, the substrate member 2 and the piezoelectric element 2
During 0, warpage occurs due to a difference in linear expansion coefficient due to a difference in material. In this state, the internal stresses of tension and compression remain in both. This is a problem to be solved by the present invention. Next, FIG. 5 shows a groove processing step using a wire saw. The bulk piezoelectric element 2 is formed by machining the groove.
0 is divided into a plurality of drive element units. At this time, in the conventional non-driving layer under the piezoelectric element 20, there is a concern that the divided piezoelectric element 20 in the unit of the driving element is separated from the adhesive layer because of its small width, or is broken from the vicinity of the adhesive layer. Although the grooves were stopped and physically connected, the remaining internal stress would remain as it is. The present invention confirms that the adhesive force of the adhesive can withstand use even if the piezoelectric element 20 is completely separated, and then processes the groove up to the upper layer of the substrate member to completely divide and separate the piezoelectric element 20 to obtain a piezoelectric element. Element 20
And a structure for removing internal stress remaining in the substrate member 2. In the subsequent steps, as shown in FIG. 6, a reference surface 2a for assembly is formed by grinding the substrate member 2 on the basis of the groove processed in the previous step, and the driving elements for driving the piezoelectric elements 20 are divided. FPC 60 to which a voltage for applying a voltage is applied is soldered to both electrodes of piezoelectric element 20. In this state, the actuator unit is completed. In order to further form a head, the parts and units are adhered by the configuration shown in FIG. 7 to complete the head.

[0009]

According to the present invention, the actuator unit of the present invention has a completely separated structure of the driving elements so that the internal stress due to the adhesion of different kinds of materials is extremely small, in other words, an actuator unit which can sufficiently bring out the performance of the piezoelectric element. It becomes possible to do.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment of an ink jet head according to the present invention.

FIG. 2 shows a basic structure of an actuator unit according to the present invention.

FIG. 3 shows a basic structure of a conventional actuator unit.

FIG. 4 is a view showing a bonding step between a piezoelectric element and a substrate material according to the present invention.

FIG. 5 is a view showing groove processing by a wire saw.

FIG. 6 is a diagram showing an assembly reference plane processing and an FPC soldering process.

FIG. 7 is a diagram showing a configuration of a head according to the present invention.

[Explanation of symbols]

 2 Substrate member 10 Nozzle plate 12 Nozzle hole 20 Piezoelectric element 30 Pressure chamber plate 32 Pressure chamber 40 Diaphragm 50 Frame 60 FPC

Claims (1)

[Claims] 1. A method for manufacturing an ink jet head comprising an actuator unit having a plurality of driving elements and a flow path unit which is coupled to the actuator unit and selectively discharges ink droplets, wherein a bulk piezoelectric element is formed on a substrate member. After bonding with a high-temperature curing type epoxy-based adhesive, when processing and dividing into grooves for each drive element, grooves are formed up to the adhesive layer and the surface layer on the adhesive layer side of the board member, and the piezoelectric element is A method for manufacturing an ink jet head, which is completely divided and separated into units.