JPH11291487A - Ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance durability of an ink jet head by removing the substantially central part of first and second plates to form electrodeless parts and preventing contact of first and second electrodes thereby eliminating an insulating film. SOLUTION: An insulating space 36 is provided between a common electrode 34 supported on a diaphragm 38 and an individual electrode 40 facing the common electrode 34 and ink is ejected by deforming the diaphragm 38 with electrostatic force acting between the common electrode 34 and the individual electrode 40. In such an ink jet head 10, an electrodeless part 50 is formed in the individual electrode 40 by removing the substantially central part thereof. Consequently, the common electrode 34 and the individual electrode 40 are prevented from coming into contact and require no protective film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrostatic ink jet head.

[0002]

2. Description of the Related Art One of several conventionally proposed ink jet heads is disclosed in Japanese Patent Application Laid-Open No. Hei 8-118626. This inkjet head includes three laminated substrates (a first substrate, a second substrate, and a third substrate). The second substrate is the first substrate
An ink chamber for containing ink, a nozzle for discharging ink, and an ink supply chamber communicating with the ink chamber are provided on the surface facing the substrate. The second substrate also has a common electrode on a surface facing the third substrate. An insulating layer is provided between the second substrate and the third substrate, and the insulating layer
A portion corresponding to the ink chamber is cut away to form an insulating space. The third substrate is provided with an individual electrode at a portion facing the insulating space.

At the time of printing using this ink jet head, a voltage (print signal) is applied between the individual electrodes and the common electrode. As a result, an electrostatic force is generated between the individual electrode and the common electrode, and the portion (diaphragm) constituting the bottom of the ink chamber is deformed toward the third substrate, and the ink is supplied from the ink supply chamber to the ink chamber. Is sucked. Next, when the voltage is released, the deformed portion returns to the original state, and at this time, the ink in the ink chamber is pressurized and discharged from the nozzle.

[0004]

In such an ink jet head, at least one of these electrodes is used to prevent contact between the common electrode and the individual electrodes.
It is covered with an insulating film made of a metal oxide such as silicon oxide. However, during the endurance period of the ink jet head, the diaphragm is deformed a considerable number of times, and is subjected to stress each time the diaphragm is deformed. Therefore, the insulating film is broken until the durability (about 1 × 10 ⁹ to 1 × 10 ¹⁰ or more times of ink ejection) expected of the ink jet head is reached, thereby shorting the common electrode and the individual electrode, There is a problem that a driving circuit electrically connected to these electrodes is damaged.
In addition, the insulating film made of a metal oxide is deteriorated by moisture,
This causes another problem that the life of the inkjet head is shortened.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems.
A member having an ink chamber for accommodating ink, a nozzle communicating with the ink chamber, a thin first plate provided adjacent to the ink chamber, and a space separated by the first plate on the opposite side of the ink chamber. A second plate facing the first plate, a first electrode provided on a surface of the first plate facing the second plate, and a second electrode facing the first plate.
The first plate is deformed by forming an electric field between the second electrode provided on the surface of the first plate and the first electrode and the second electrode, whereby the ink in the ink chamber is pressurized. And a driving unit that discharges from a nozzle. At a substantially central portion of the first plate or the second plate, a part of the first electrode or the second electrode is removed to form an electrodeless portion. Features.

[0006] In another embodiment of the present invention, a part of the first electrode or the part of the second electrode from which a part of the second electrode is removed is substantially the same as the corresponding first or second electrode. Or an island portion having a thickness slightly larger than this. Further, in another embodiment of the present invention, the first plate also serves as the first electrode, and the second plate also serves as the second electrode.

[0007]

According to the ink jet head of the present invention thus constituted, since the substantially central portion of the first plate or the second plate is removed to form an electrodeless portion, the first electrode and the second electrode are formed. Contact can be prevented. Therefore, not only is the insulating film unnecessary, but the life of the inkjet head is not limited by the deterioration of the insulating film. Further, since it is not necessary to protect the electrodes with an insulating film made of a metal oxide such as silicon oxide, there is no problem that the life of the inkjet head is shortened due to the deterioration of the insulating film.

[0008] In the form in which the island portion is formed,
Since the amount of deformation of the first plate is constant, there is an advantage that ink of a fixed size can be ejected.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described with reference to the drawings. As shown in FIGS. 1 and 2, an inkjet head 10 of the present invention includes a first substrate 12,
The substrate 14 and the third substrate 16 are stacked.

[0010] The first substrate 12 is made of, for example, glass. The second substrate 14 is made of, for example, silicon, and a plurality of ink chambers 22 containing ink 20 (see FIG. 2) are formed on the surface 18 facing the first substrate 12 by, for example, etching as shown in FIG. A plurality of nozzles 24 communicating each ink chamber 22 with the atmosphere, an ink supply chamber 26 containing ink 20 to be supplied to each ink chamber 22, and a plurality of inks communicating each ink chamber 20 with the ink supply chamber 26. A supply path 28 is formed.

The second substrate 14 facing the third substrate 16
Of the ink chamber 22 by etching, for example.
The recess 32 is formed in the part opposing to each other.
Each depression 32 is provided with an electrode layer (common electrode 34) of a conductive metal thin film by, for example, sputtering. The thickness of the common electrode 34 is smaller than the depth of the depression 32, whereby the air insulating layer 36 is formed on the common electrode 34. Each common electrode 34 is connected to each other and grounded.

The ink chamber 22 formed as described above
The thickness of the bottom wall (diaphragm 38) is such that it can be easily deformed by electrostatic force, as described later.

The third substrate 16 is made of glass, and has a conductive metal thin film electrode layer (individual electrode 40) in a region facing each ink chamber 22. These individual electrodes 40
For example, after the depression 42 is formed on the corresponding surface of the substrate 16 by etching or the like, the depression 42 is formed by, for example, sputtering a conductive metal. Recess 42 and individual electrode 4
Numerals 0 extend toward one side of the third substrate 16, respectively, and the extension of the individual electrode 40 serves as an electrical connection 44. Each electric connection portion 44 is connected to a driving portion 46, and each individual electrode 40 is connected from the driving portion 46 through each electric connection portion 44.
The print signal 48 can be applied to the printer.

The individual electrode 40 has a substantially central portion cut off in a substantially elliptical shape to form an electrodeless portion 50. The non-electrode portion 50 has a size and shape that can prevent the common electrode 34 from contacting the individual electrode 40 when the diaphragm 38 is displaced toward the third substrate 16 as described later. It is appropriately determined according to the shape of the ink chamber 22 and the like.

The bonding of these three substrates 12, 14 and 16 is not limited to a specific bonding method. However, since the distance between the common electrode 34 and the individual electrode 40 needs to be set to, for example, about 5 μm, it is preferable to use anodic bonding.

In the ink-jet head 10 having the above-described configuration, the driving signal 46 is applied to the individual electrodes 40 by the print signal 48.
Is applied, an electric field is formed between the individual electrode 40 and the common electrode 34 opposed thereto, and an electrostatic force acts between the two. As a result, the common electrode 34 and the diaphragm 38
Is attracted to the individual electrode 40 and displaced. However, since the substantially central portion of the individual electrode 40 is cut off to form the electrodeless portion 50, the displaced common electrode 34 does not come into contact with the individual electrode 40. On the other hand, a negative pressure is generated in the ink chamber 22 due to the displacement of the diaphragm 38, so that the ink supply path 2
The ink 20 is supplied to the ink chamber 22 from the ink supply chamber 26 via the ink supply chamber 8.

Next, when the print signal 48 is turned off, the electrostatic force acting between the individual electrode 40 and the common electrode 34 disappears, and the diaphragm 38 returns to the position before the displacement by its own elastic recovery force. As a result, the ink 20 in the ink chamber 22 is pressurized, and ink droplets are ejected from the nozzle 24.

In the embodiment described above, the individual electrodes 4
The electrodeless portion 50 is formed by cutting off the substantially central portion of the zero, thereby preventing the contact between the common electrode 34 and the individual electrode 40. The means for preventing the contact between the common electrode 34 and the individual electrode 40 is as follows. It is not limited to.

For example, FIG. 5 shows another embodiment of the contact preventing means, in which an island portion 52 is formed at a position corresponding to the electrodeless portion, and the island portion 52 is individually formed toward the diaphragm 38. It protrudes slightly from the surface of the electrode 40. In this embodiment, the diaphragm 38
At the same time, the displaced common electrode 34 comes into contact with the island portion 52 to restrict the movement, and the contact with the individual electrode 40 is prevented. Further, in the present embodiment, since the displacement amount of the diaphragm 38 is constant, an ink droplet having a stable size is ejected every time.

The island portion may be provided on the common electrode 34 side as shown in FIG. In this case, a substantially central portion of the common electrode 34 is cut into a substantially elliptical shape to form an electrodeless portion, and a portion of the diaphragm 38 facing the electrodeless portion protrudes toward the third substrate 16 to form an island portion. 54 are formed. Note that the thickness (height) of these island portions 52 and 54 may be substantially the same as the thickness of the individual electrode 40 as long as the contact between the common electrode 34 and the individual electrode 40 can be prevented.

The island portion is preferably formed by, for example, the etching technique shown in FIG. In the etching technique shown here, first, a resist is applied to the surface of a substrate (for example, when the island portion 50 is formed on the third substrate 16). Next, the resist is covered with a photomask having an opening corresponding to the island portion, and the mask pattern (island pattern) is exposed by irradiating ultraviolet rays. Subsequently, the exposed portion of the resist is removed, and a residual resist layer corresponding to the island portion is formed. Thereafter, SiC particles having a fine particle size (about 2 μm) are sprayed,
A portion excluding a portion covered with the residual resist layer is polished, thereby forming an island portion. Next, an electrode is deposited on the surface of the substrate including the residual resist layer. Finally, the remaining resist layer and the electrode portion on the remaining resist layer are removed.

The ink jet head of the present invention described above can be variously improved. For example, in the first embodiment, the electrodeless portions are provided on the individual electrodes, but the electrodeless portions may be provided on the common electrode.

Further, in the above embodiment, the non-electrode portion of the individual electrode has an elliptical shape. However, the present invention is not limited to this, and the non-electrode portion may be formed so that the individual electrode has a U-shape or a square shape. Alternatively, an elliptical or square-shaped electrode may be partially cut away.

Further, as shown in FIG.
(And / or the common electrode 34) may be covered with a protective film 56 (for example, about 2 μm thick). This protective film 56 is preferably made of SiFH containing fluorine having high water repellency. The protective film is also preferably formed by, for example, known sputtering. The protective film is not only on the electrode,
The entire substrate may be covered.

Further, in the above embodiment, the nozzles 24 are formed on the second substrate 14, but as shown in FIG.
The nozzle 60 may be formed on the first substrate 12.

The materials of the three substrates 12, 14, and 16 are not limited to those described above, but include silicon, glass, ceramics,
Any of metal, resin, photosensitive material and the like may be used.

In the above embodiment, the second substrate 14
Although the diaphragm is integrally formed in this embodiment, the diaphragm may be formed by another member. In this case, the ink chamber of the second substrate penetrates the upper and lower surfaces, and a diaphragm is attached to the surface facing the third substrate.

Further, in the above embodiment, the second substrate 14 is provided with the depression 32 on the opposite side of the ink chamber, whereby the air insulating layer 36 is provided between the common electrode 34 and the individual electrode 40. However, the method of forming the air insulating layer between the common electrode 34 and the individual electrode 40 is not limited to this. For example, on the surface of the third substrate 16 facing the second substrate 14, a depression having a depth substantially equal to the depression 34 is formed in a portion facing the ink chamber 22, whereby the common electrode and the individual electrode are separated. An air insulating layer may be formed therebetween. Alternatively, a separate spacer may be provided between the second and third substrates 14 and 16 to form an air insulating layer between the common electrode and the individual electrodes.

Furthermore, in the above embodiment, the common electrode is provided on the second substrate and the individual electrode is provided on the third substrate. On the contrary, the individual electrode is provided on the second substrate and the individual electrode is provided on the third substrate. A common electrode may be provided.

In the above embodiment, the electrode layer is formed by a metal thin film. However, an element belonging to Group 3 or 5 of the periodic table can be used on the surface of the substrate with boron or phosphorus. May be implanted and diffused with boron, and the boron diffusion layer may be used as an electrode layer. Further, each electrode does not need to be provided independently on the corresponding substrate, and when this substrate is formed of a conductive material, this substrate can be used also as an electrode.

As shown in FIGS. 1 and 2, printing is performed using an ink-jet head of the present invention having an electrode-less portion and a conventional ink-jet head having no electrode-less portion in which individual electrodes are covered with a protective layer of silicon oxide. Tested. as a result,
With the ink jet head of the present invention, there was no change in the printed image even when the ink was ejected 1 × 10 ⁹ times. On the other hand, in the conventional inkjet head, the individual electrode and the common electrode were short-circuited by 1 × 10 ⁷ ink ejections.

FIG. 10 shows a part of a printer 100 in which the ink jet head 10 is incorporated. This printer 10
Reference numeral 0 denotes a bottom plate 102, a pair of support walls 104 extending substantially perpendicularly from the bottom plate 102 and facing each other, and
4 has a front wall 106 connected thereto. Outside the front wall 106, a paper feed tray 108 for storing a sheet (paper) S to be printed by the printer 100 is provided, and the sheet S stored in the paper feed tray 108 is formed on the front wall 106. The printer 1 is connected via a paper feed port (not shown)
00 is supplied inside.

Inside the front wall 106, a pair of support walls 10
4, an upper guide rail 112 parallel to the front wall 106 and a lower guide rail 114 disposed below the upper guide rail 112 are supported. On these guide rails 112 and 114, an ink cartridge 116 is movably supported. Insert the ink cartridge 116 into the guide rails 112 and 114
The scanning mechanism 118 that reciprocates along a pair of the pulleys 120 supports a pair of pulleys 120 supported inside the front wall 106 near the respective support walls 104 and a belt 122 wound around these pulleys 120. And a motor (not shown) for rotating the pulley 120 forward and reverse.
An ink cartridge 11116 is connected to a part of the second cartridge 2.

In the present embodiment, the ink cartridge 116 includes one or a plurality of the above-described ink jet heads 10 on the lower surface. Ink cartridge 116
A sheet guide 124 is provided below and at a distance from the inkjet head 10. This seat guide 1
24, a sheet feeding roller 128 for conveying the sheet S fed into the printer 100 through the sheet feeding port of the front wall 106 in the direction of arrow 126 (conveying direction).
Are arranged in a direction perpendicular to the paper feeding direction, and are rotatably supported by the opposing support wall 104. Further, on the downstream side of the ink cartridge 116 with respect to the sheet feeding direction, a pressing roller 130 for pressing the sheet S against the sheet guide 124 is arranged in a direction orthogonal to the sheet feeding direction.

The paper feed roller 128 has a gear 134 fixed to a shaft 132 and a support wall 10 near the gear 134.
4 is connected to a motor 138 via a gear 136 rotatably supported by the motor 4, and the sheet feed roller 128 rotates based on the rotation of the motor 138 to convey the sheet S in the direction of arrow 126. It is.

At the time of printing by the printer 100 having the above-described configuration, the sheet S sent from the paper feed tray 108 is printed.
Is fed into the printer 100 through the paper feed port of the front wall 106. Next, the sheet S is conveyed in the direction of arrow 126 along the sheet guide 124 by the sheet feeding roller 128 that rotates based on the driving of the motor 138. Further, the sheet S moving on the sheet guide 124 is pressed against the sheet guide 124 by the pressing roller 130,
Thereby, the interval between the sheet S and the ink head 10 is kept constant.

In synchronization with the movement of the sheet S, the ink cartridge 116 reciprocates along the guide rails 112 and 114 by the rotation of the belt 122, and the sheet guide 1
The ink is ejected from the ink jet head 10 to the portion of the sheet S that moves on the top 24 and printing is performed. The printed sheet S is discharged onto a discharge tray (not shown).

[Brief description of the drawings]

FIG. 1 is an enlarged exploded perspective view of an inkjet head according to a first embodiment.

FIG. 2 is an enlarged sectional view of the ink jet head shown in FIG.

FIG. 3 is an enlarged partial plan view of a second substrate used in the inkjet head shown in FIG.

FIG. 4 is an enlarged partial plan view of an individual electrode used in the inkjet head shown in FIG.

FIG. 5 is a cross-sectional view of an inkjet head in which an island portion is provided in an electrodeless portion of an individual electrode.

FIG. 6 is a cross-sectional view of an inkjet head in which an island portion is provided in a non-electrode portion of a common electrode.

FIG. 7 is a diagram showing a process of an etching technique for forming an island portion on a substrate.

FIG. 8 is a cross-sectional view of an inkjet head in which individual electrodes are protected by an oxide film.

FIG. 9 is a cross-sectional view of an inkjet head in which a nozzle is formed on a first substrate.

FIG. 10 is a partial perspective view of a printer incorporating the inkjet head of the present invention.

[Explanation of symbols]

10: inkjet head, 12: first substrate, 14
... 2nd substrate, 16 ... 3rd substrate, 20 ... ink, 22
... Ink chamber, 24 ... Nozzle, 34 ... Common electrode, 36 ... Air insulating layer, 38 ... Diaphragm, 40 ... Individual electrode, 46
…Drive part.

Claims (4)

[Claims] A member having an ink chamber for accommodating ink, a nozzle communicating with the ink chamber, a thin first plate provided adjacent to the ink chamber, and a first plate on an opposite side of the ink chamber.
A second plate facing the first plate with a space therebetween, a first electrode provided on the surface of the first plate facing the second plate, and a surface of the second plate facing the first plate A second electrode provided in
The first plate is deformed by forming an electric field between the first electrode and the second electrode, thereby forming a driving unit that pressurizes the ink in the ink chamber and discharges it from the nozzle. An ink-jet head, wherein an electrodeless portion is formed by removing a portion of the first electrode or the second electrode at a substantially central portion of the second plate. 2. A part from which a part of the first electrode or a part of the second electrode is removed has a corresponding first electrode or second electrode.
2. The ink jet head according to claim 1, wherein an island portion having substantially the same thickness as or a slightly larger thickness than the electrode is formed. 3. The ink jet head according to claim 1, wherein the first plate also serves as the first electrode. 4. The ink jet head according to claim 1, wherein the second plate also serves as the second electrode.