JPH11227188A - Ink jet head and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a gap through a simple process while suppressing step or protrusion as much as possible by a structure wherein the space of a recess for forming an electrode decreases gradually toward the center thereof. SOLUTION: The ink jet head has a laminate structure of a first substrate 1 of silicon single crystal provided with a diaphragm 3 and an ejection chamber 4, and a second substrate 2 provided with an electrode 5, an air gap 6b and and a part 6c for forming the electrode 5. A voltage is applied to the electrode 5 arranged on the bottom wall of a recess formed in the second substrate 2 in order to deform the diaphragm 3 by electrostatic force. Since the gap between the diaphragm 3 and the electrode 5 can be defined easily and the surface of the electrode 5 can be made concave, short circuit can be prevented between the diaphragm 3 and the electrode 5 resulting in a highly reliable ink jet head. The recess can be made easily by a simpler process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet head using electrostatic force and a method for manufacturing the same.

[0002]

2. Description of the Related Art In the invention of Japanese Patent Application Laid-Open No. Hei 7-214679 (Seiko Epson), an electrostatic ink jet prints by applying a voltage between an electrode and a diaphragm and applying a positive or negative charge to them. The plate is deformed by electrostatic attraction or repulsion, and ink in the pressure chamber is ejected from the nozzle. The structure is such that an insulating layer for preventing a short circuit is interposed between a thinly processed diaphragm and electrodes arranged in close proximity to each other. Japanese Unexamined Patent Publication No. Hei 7 (1995) -14769 discloses that the gap between the diaphragm and the electrode is set to 2 μm or less, and the thickness of the insulating film is limited to the range of 500 to 3000 Å.

[0003]

With a standard voltage used as a printer, it is not possible to obtain a pressure sufficient to discharge or suck ink, so that it is desirable to make the gap extremely small (2 μm or less). It is.
In the formation of the electrodes, a gap is provided on the insulating substrate on the surface facing the diaphragm and the electrode thin film material is formed in a stepped manner in order to make the process as simple as possible. In Japanese Patent Application Laid-Open No. Hei 7-214679, a stable ink ejection can always be obtained with the same configuration, reliability is high without any trouble such as destruction even when used for a long time, and efficient driving at a low driving voltage is possible. The invention for the purpose of providing an ink jet head which performs the above is disclosed.

In an ink jet head, it is desirable to make the gap between the diaphragm and the electrode as small as possible in order to be able to drive at a low driving voltage. However, when the thickness of the insulating film is increased, the electric field strength between the diaphragm and the electrode is reduced. On the contrary, when the thickness is reduced, the coverage of the step is poor and durability becomes a problem.
Furthermore, even if the gap is processed extremely accurately with the current processing accuracy, projections due to foreign matter, dust, etc. are generated, and the diaphragm and a part of the electrode come into contact with each other or the gap interval is further narrowed. Discharge occurs between the electrodes, causing dielectric breakdown and melting the electrodes.

[0005] This phenomenon occurs frequently at the position and the end where the displacement of the diaphragm is maximum on the electrode surface facing the diaphragm. This is because the gap between the electrode and the electrode is the closest due to the displacement of the diaphragm, and the end portion is more likely to have a protrusion than other surfaces due to variations in mask accuracy, process conditions, and the like. Further, when the electrode is formed by a process using a lift-off technique, protrusions of the electrode material often remain, which come into contact with the diaphragm or cause discharge. If a discharge occurs in a part of the head, the head is broken by a short circuit after being successively transferred to surrounding parts having a low withstand voltage.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned drawbacks, and has an arrangement in which steps and protrusions are formed as little as possible, and an ink-jet head capable of forming a gap by a relatively simple process, and a method of manufacturing the same. Is provided.

[0007]

According to a first aspect of the present invention, there is provided a first substrate on which a diaphragm constituting at least a part of a wall of a pressure chamber communicating with a nozzle for discharging ink is formed;
An electrode provided to face the diaphragm with a gap therebetween, and a second substrate having a concave portion formed of a side wall and a bottom wall provided with the electrode are joined, and an electrode is formed between the diaphragm and the electrode. In the ink jet head which deforms the vibration plate by the electrostatic force to discharge ink droplets from the nozzle holes, the concave portion has a shape in which a distance from the vibration plate increases from the side wall toward the center of the bottom wall. An inkjet head.

According to a second aspect of the present invention, in the ink jet head according to the first aspect, the shape in which the distance increases toward the center of the diaphragm is formed on the bottom wall from the side wall toward the center of the diaphragm. An inkjet head having a shape provided with one or more steps.

According to a third aspect of the present invention, in the ink jet head according to the first or second aspect, the electrode is embedded in the concave portion, the upper surface of the end is flat with the concave portion, and the bottom of the concave portion is directed toward the center. This is an inkjet head that is arranged with an inclination in the wall direction.

According to a fourth aspect of the present invention, there is provided the method of manufacturing the second substrate of the ink-jet head according to any one of the first to third aspects, wherein a photoresist pattern is formed on the second substrate, and etching is performed. A method of manufacturing a second substrate of an ink jet head in which a concave portion is formed by using the method, and an electrode made of a film of an electrode material is formed in the concave portion.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In an ink jet head of the present invention, when a voltage is applied to an electrode, an attractive force acts between the electrode and a diaphragm arranged opposite to the electrode, whereby an attractive force is generated. In this way, the vibration plate is deformed to discharge ink droplets from the nozzle holes. Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an enlarged sectional view showing a configuration of a main part for describing an embodiment of an ink jet head according to the present invention. In the drawing, reference numeral 1 denotes a first substrate made of a silicon single crystal on which a vibration plate 3 and a discharge chamber 4 are formed, and 2 in FIG. 1 denotes an electrode 5, a gap 6b serving as a gap, and an electrode forming portion for forming the electrode 5. 6c,
6D is a second substrate having 6d. In FIG. 1, the inkjet head has a laminated structure in which a first substrate and a second substrate are overlapped and joined. The silicon single crystal of the first substrate is subjected to anisotropic etching using an alkali solution using photolithography or the like, which has been cultivated in the IC manufacturing technology, so that the diaphragm 3, the discharge chamber 4, and the like are accurately formed. Well formed. Note that the method for manufacturing the first substrate is not directly related to the present invention, and thus is omitted here.

FIG. 2 is a view showing a process of manufacturing the second substrate of the present invention. The second substrate 2 bonded to the lower surface of the first substrate 1 is made of borosilicate glass having a coefficient of thermal expansion substantially equal to the coefficient of thermal expansion of silicon, and a concave portion 6 for mounting the electrode 5 on this substrate is etched. It is formed in a desired gap. Next, a method of forming the concave portion 6 will be described with reference to FIG.
As shown in FIG. 2, a photoresist 8a having an opening O is formed on the outermost surface of the glass at the electrode formation location.
As shown in FIG. 2 (F), the opening 6b in the portion adjacent to the diaphragm 3 is made the widest, and the concave portion 6 is formed so that the opening 6d becomes narrower toward the bottom wall where the electrode 5 is provided.
Here, first, the opening 6d is formed by etching by wet etching, then the pattern is formed by the photoresist 8b, and the etching 6c is formed again. Further, a pattern of the photoresist 8c is formed, and 6b is formed again by etching, so that the concave portion 6 having a desired plurality of steps is formed in the exposed portion of the glass substrate. At this time, a hydrofluoric acid-based etchant is used. In forming such a plurality of steps, it is necessary that the electrode 5 to be formed later be formed flat so as not to travel to the diaphragm 3 side from the recess 6. By forming an electrode in the concave portion by forming the concave portion in such a shape, the electrode 5 has a structure in which the end portion of the electrode 5 is flat, and the concave portion of the electrode 5 is inclined at the center of the electrode. Is obtained. The electrode is formed into such a shape by making the opposing electrode surface having a maximum displacement concave when the diaphragm 3 is attracted to the electrode 5 side by electrostatic force and the diaphragm 3 is displaced in a parabolic shape. This is because discharge and short circuit between the diaphragm 3 and the electrode 5 can be prevented.

Next, after the above-described concave portion 6 is formed, as shown in FIG. 2G, the electrode material 5a is formed on the entire surface to form the electrode 5 inside the concave portion 6 having a plurality of steps. After forming a film, a pattern of a photoresist 8d is formed as shown in FIG. 2H, and an electrode 5 is formed with an acetic acid-based etchant. Further, after forming the insulating film shown in FIG. 2I, patterning is performed to form an insulating film 7 on the electrode 5. In this example, a concave portion 6 having a step was formed with an etching solution BHF using a borosilicate glass (# 7740) substrate 2 having a thickness of 1 mm and having a mirror-polished surface.
The gap (between the bottom surface of the diaphragm and the upper surface of the insulating film) is formed at a depth of 1.0 μm. Electrode (Ni) 5, protective film (Si
O ₂ ) 7 is formed to a thickness of 0.1 μm each, and then the first substrate and the second substrate are joined by anodic bonding, thereby completing the ink jet head having the essential configuration shown in FIG.
In this embodiment, the recess 6 can be formed in the order of 6b, 6c, and 6d.

FIG. 3 shows a second embodiment of the present invention and is a view for explaining a manufacturing process of the second substrate. First, as in the case of the first embodiment, the mirror-polished surface of the borosilicate glass substrate 2 having a thickness of 1 mm is formed by photolithography and etching up to the concave portion 6 shown in FIG. Next, a pattern 8e to be the electrode 5 is formed by the resist shown in FIG. 3G, and Pt55a / Ti5
5b film is laminated. Thereafter, as shown in FIG. 3H, an electrode 5 composed of 5a and 5b is formed by lift-off using acetone + ultrasonic waves. Then, as in the first embodiment, the protective film 7 is formed.
Is formed, the first substrate and the second substrate are anodically bonded to complete an ink jet head having a main configuration shown in FIG.

Table 1 shows that a second substrate was manufactured by the process used in the embodiment shown in FIG.
The results of evaluation by applying the voltage shown in FIG. In the present embodiment, the concave portion 6c is set to 0.1 μm, and the concave portion 6d is set to 0.03 to 0.03 μm.
One hundred heads were formed in the range of 0.12 micrometer, and the ratio of the occurrence of discharge and short-circuit and the suitable liquid particle size of the head provided with the recess 6d were evaluated with respect to the head not provided with the recess 6d. According to Table 1, the effect of the concave portion 6d is as follows.
It can be seen that the effect is obtained at a height of 03 micrometer or more. Preferably, it is 0.05 micrometer or more, more preferably 0.07 micrometer or more. However, if the concave portion 6d is dug by 0.1 μm or more, the liquid suitable particle size is inferior, which is not preferable. This is presumably because when the thickness is 0.1 μm or more, the diaphragm 3 cannot be sufficiently displaced, and a required ink ejection pressure cannot be secured. Therefore, the depth of the concave portion 6d is 0.03 or more.
Preferred experimental results were obtained in the 0.07 micrometer range.

[0016]

[Table 1]

[0017]

According to the present invention, a voltage is applied to an electrode disposed on the bottom wall of the recess formed in the second substrate.
In an inkjet head having a mechanism for deforming the diaphragm by electrostatic force, the space of the concave portion forming the electrode is configured to be narrower toward the center, so that the gap between the diaphragm and the electrode can be easily defined, and Since the electrode surface can be easily formed in a concave shape by forming the concave portion in this manner, a short-circuit between the diaphragm and the electrode does not occur, and a highly reliable inkjet head can be obtained. Further, the concave portion can be easily manufactured by a simple manufacturing process.

According to a third aspect of the present invention, since the electrode is embedded in the concave portion and the electrode is inclined toward the center, the step of the electrode is eliminated, and the coverage of the insulating film is improved. Discharge and short circuit with the electrode can be prevented with higher reliability.

According to the fourth aspect, the second substrate of the ink jet head can be easily manufactured by a simple process.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a main part for describing an ink jet head of the present invention.

FIG. 2 is a diagram for explaining a manufacturing process of the embodiment of the second substrate of the inkjet head.

FIG. 3 is a diagram for explaining a manufacturing process of another embodiment of the second substrate of the inkjet head.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... 1st board | substrate, 2 ... 2nd board | substrate, 3 ... diaphragm, 4 ... discharge chamber, 5 ... electrode, 6 ... void, 7 ... insulating film, 8a, 8b, 8
c, 8d: photoresist, 8e: pattern.

Claims (4)

[Claims] 1. A first substrate on which a diaphragm constituting at least a part of a wall of a pressure chamber communicating with a nozzle for discharging ink is formed, and a first substrate is provided to face the diaphragm via a gap. An electrode and a second substrate having a recess formed by a side wall and a bottom wall provided with the electrode are joined, and the diaphragm is deformed by an electrostatic force generated between the diaphragm and the electrode to form an ink liquid. In the ink jet head for discharging a droplet from a nozzle hole, the concave portion has a shape in which a distance from the vibration plate increases from the side wall toward a center of the bottom wall. 2. The ink jet head according to claim 1, wherein the shape in which the distance increases toward the center of the diaphragm includes one or more steps on the bottom wall from the side wall toward the center of the diaphragm. An ink jet head characterized by having a shape provided with. 3. The ink jet head according to claim 1, wherein the electrode is embedded in the recess, and an upper surface of the end is flat with the recess, and is inclined toward the center of the recess bottom wall toward the center. An inkjet head characterized by being held and held. 4. The method for manufacturing the second substrate of the ink jet head according to claim 1, wherein a pattern of a photoresist is formed on the second substrate, and a concave portion is formed by etching. Forming an electrode made of a film of an electrode material in the concave portion.