JP2002210957A - Liquid drop discharge head, ink jet recorder and micro actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the trouble that residual charges are reduced insufficiently. SOLUTION: A projecting part 14 which is higher than an electrode 13 and against which a diaphragm 10 butts is set to the side of the electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a droplet discharge head, an ink jet recording apparatus and a microactuator.

[0002]

2. Description of the Related Art In general, as an ink jet head which is one of the droplet discharge heads used in an ink jet recording apparatus used as an image recording apparatus (image forming apparatus) such as a printer, a facsimile, a copying machine, a plotter, etc.
A nozzle for discharging ink droplets, a liquid chamber (also referred to as an ink flow path, a pressure chamber, a discharge chamber, a pressure chamber, a pressurized liquid chamber, and the like) to which the nozzle communicates, and a wall surface of the liquid chamber are formed. The diaphragm has an electrode facing the diaphragm, and the diaphragm is deformed by the electrostatic force generated by applying a voltage between the diaphragm and the electrode to change the pressure / volume in the liquid chamber. There is an electrostatic inkjet head that discharges ink droplets from nozzles by causing the nozzles to eject ink droplets.

In a conventional electrostatic ink jet head, as described in Japanese Patent Application Laid-Open No. 2-256351, a diaphragm comes into contact with an electrode (actually, the diaphragm comes into contact with an insulating film which is a protective film on the electrode surface). There is a contact drive method in which the diaphragm is deformed and displaced until it contacts, and a contact drive method in which the diaphragm is deformed and displaced to a position where the diaphragm does not contact the electrode. Of these, the contact drive method of deforming and displacing the electrode until it comes into contact with the electrode can make the amount of deformation (displacement) of the diaphragm more constant, so that the voltage is reduced and the ink droplet ejection amount is made uniform. It ’s excellent.

When driven by this contact driving method, residual charge is generated on the diaphragm, and the displacement of the diaphragm becomes unstable. Therefore, as described in Japanese Patent Application Laid-Open No. 6133413, the polarity is conventionally known. The remaining charge is erased by alternately applying different drive voltages.

[0005]

However, in order to alternately apply drive voltages having different polarities as in the above-mentioned conventional ink jet head, there is a problem that a special drive system and a power supply of reverse polarity are required. is there.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has a simple configuration, a droplet discharge head capable of obtaining a stable diaphragm displacement, an ink jet recording apparatus equipped with this head, and a stable configuration with a simple configuration. It is an object of the present invention to provide a microactuator capable of obtaining a vibrating plate displacement.

[0007]

In order to solve the above-mentioned problems, a droplet discharge head according to the present invention has a structure in which a convex portion is provided on an electrode side, which is higher than an electrode and in which a diaphragm comes into contact.

Here, it is preferable that the projections are formed of the same material as the electrodes. Further, it is preferable that an insulating film is formed on the surface of the projection. Further, it is preferable that a joint portion between the substrate provided with the diaphragm and the substrate provided with the electrode contains the same material as the electrode. In addition, it is preferable to form irregularities for providing electrodes and projections on the surface of the substrate on which the electrodes are provided on the diaphragm side. Further, it is preferable that the diaphragm and the electrode are arranged in a non-parallel state.

[0009] The ink jet recording apparatus according to the present invention comprises:
The ink jet head is configured to be the droplet discharge head according to the invention.

[0010] The microactuator according to the present invention comprises:
In this configuration, a protruding portion is provided on the electrode side, which is higher than the electrode and in which the diaphragm comes into contact.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view of the electrostatic ink-jet head to which the present invention is applied, taken along the long side of the diaphragm, FIG. 2 is a schematic enlarged cross-sectional view of the head taken along the short side of the diaphragm, and FIG. It is explanatory drawing provided for description of operation | movement.

The electrostatic ink jet head includes a diaphragm substrate 1, an electrode substrate 2 joined to a lower surface of the diaphragm substrate 1, and a nozzle plate 3 joined to an upper surface of the diaphragm substrate 1, and includes a droplet. A nozzle 5 for discharging ink droplets, a liquid chamber 6 communicating with the nozzle 5, a common liquid chamber 8 for supplying ink to the liquid chamber 6 via a fluid resistance part 7, and the like are formed.

The diaphragm substrate 1 has a liquid chamber 6 and the liquid chamber 6.
And a recess forming the fluid resistance portion 7 and a common liquid chamber 8 are formed. The diaphragm substrate 1 can be formed using an SOI substrate in which a silicon substrate is bonded via an oxide film. In this case, the concave portion serving as the liquid chamber 6 is etched using an etching solution such as a KOH aqueous solution, so that the diaphragm 10 can be formed with high accuracy using the active layer as an etch stop layer. Also, the diaphragm 10 can be formed with high precision by forming a high-concentration P-type impurity, for example, a boron diffusion layer on a silicon substrate, and performing etch stop using the boron diffusion layer as an etching stop layer.

An oxide film layer (insulating film layer) 2a is formed on the electrode substrate 2 by a thermal oxidation method or the like using a silicon substrate, and a recess 11 is formed in the oxide film layer 2a.
An electrode 13 facing the diaphragm 10 with a gap therebetween and a convex portion 14 higher than the electrode 13 and contacting the diaphragm 10 are provided on the bottom surface of 1. The vibrating plate 10 and the electrodes 13 constitute a microactuator that deforms and displaces the vibrating plate 10 by electrostatic force.

Here, on the bottom surface of the concave portion 11 of the electrode substrate 2, there are provided a convex portion 15a having a non-parallel bottom surface with respect to the diaphragm 10 for forming the electrode 13, and concave portions 15b and 15c having a parallel bottom surface. , These recesses 15a, 15b, 1
5c, each of which has a top surface parallel to the diaphragm 10 for providing the protrusions 14a.
16 having a top surface in parallel with the diaphragm 10
b is formed. Note that the number of uneven portions provided on the bottom surface of the concave portion 11 is not limited to this example.

The electrode portions 13a, 13b, 13c forming the electrodes 13 are formed on the bottom surfaces of the recesses 15a, 15b, 15c.
Are provided, and the protrusions 14a and 14b are provided on the upper surfaces of the protrusions 16a and 16b, respectively. These electrodes 13 (13a to 13c) and convex portions 14 (14a, 14a)
b) is the same material, for example, gold, or Al, C which is generally used in a process for forming a semiconductor element.
It is made of a metal material such as r or Ni, or a high melting point metal such as Ti, TiN or W.

In this case, the electrode portion 13a formed in the concave portion 15a non-parallel (inclined) to the diaphragm 10 becomes non-parallel to the diaphragm 10 and the concave portion 15b parallel to the diaphragm 10 , 15c formed on the electrode part 13
b and 13c are parallel to the diaphragm 10.

The electrodes 13 (13a to 13a)
c) and SiO _{2 on} the surfaces of the projections 14 (14 a, 14 b) to prevent damage due to contact with the diaphragm 16.
A protective film (insulating film) 17 made of an oxide insulating film such as a film and a nitride insulating film such as a Si ₃ N ₄ film is formed.

The nozzle plate 3 has a nozzle 5 formed of a metal layer or a laminated member in which a metal layer and a polymer layer are directly joined, a resin member, nickel electroforming, or the like. (Surface: ejection surface), a water-repellent film is formed by a known method such as a plating film or a water-repellent coating in order to ensure water repellency with the ink. In addition, an ink supply hole 18 for supplying ink to the common liquid chamber 8 from outside is formed in the nozzle plate 3.

In the ink-jet head thus configured, the diaphragm 10 is used as a common electrode and the electrode 13 is used as an individual electrode. The diaphragm 10 is deformed and displaced toward the electrode 13 due to an electrostatic force generated between the electrode 13 and the diaphragm 10. By returning the electric charge between the diaphragm 10 and the electrode 13 from this state, the diaphragm 10 is returned and deformed.
When the internal volume (volume) / pressure of the liquid chamber 6 changes, ink droplets are ejected from the nozzles 5.

That is, when a pulse voltage is applied to the electrode 13 serving as an individual electrode, a potential difference occurs between the electrode 10 and the diaphragm 10 serving as a common electrode, and an electrostatic force is generated between the individual electrode 13 and the diaphragm 10. As a result, the diaphragm 10 is displaced according to the magnitude of the applied voltage. After that, the applied pulse voltage falls, whereby the displacement of the diaphragm 10 is restored, and the restoring force increases the pressure in the liquid chamber 6 and the ink droplets are ejected from the nozzles 5.

In this case, the diaphragm 10 and the electrode portion 13a are in a non-parallel state, and the electrostatic force becomes larger as the gap length between the diaphragm and the electrode becomes shorter, so that the diaphragm 10 faces the electrode portion 13a. Since the deformation is started from the side where the vibration is performed, and the gap length is reduced in accordance with the deformation of the diaphragm 10, the diaphragm 10 can be deformed and displaced at a low voltage, and low voltage driving can be achieved.

When a driving waveform is applied between the diaphragm 10 and the electrode 13 so that the diaphragm 10 can be displaced such that the diaphragm 10 contacts the electrode 13, as shown in FIG.
Is deformed and displaced toward the electrode 13, so that the vibration plate 13 comes into contact with the convex portion 14 (the upper surface of the insulating film 17) on the electrode substrate 2 side, and further deformation of the vibration plate 10 is limited.

Therefore, the surface of the vibration plate 10 does not come into contact with the electrode 13, and the residual charge due to the contact between the vibration plate 10 and the electrode 13 is hardly generated. The diaphragm 10
Since the convex portion 14 in contact with the convex portion 1 is electrically independent of the adjacent electrode 13 and no voltage is applied, the convex portion 1
No residual charge is generated in No. 4.

As described above, by providing the projection 14 on the electrode substrate 2 side to which the vibration plate 10 abuts higher than the electrode 13, the contact between the vibration plate 10 and the electrode 13 can be prevented, and the residual charge can be reduced. Generation can be reduced, and stable displacement characteristics of the diaphragm can be obtained.

Next, a process for forming the electrode substrate 2 will be described with reference to FIG.
A description will be given also with reference to FIG. First, using a support substrate (Si substrate) 21 as the electrode substrate 2, a thermal oxide film (oxide film) 21a is formed on the Si substrate 21 as shown in FIG. Then, as shown in FIG.
A concave portion 11 for forming an electrode 13 is formed in 1a by etching. At this time, a non-parallel bottom surface 22a non-parallel to the diaphragm and a parallel bottom surface 22b parallel to the diaphragm are formed on the bottom surface of the concave portion 11.

Next, as shown in FIG.
1 is coated with a resist to form a resist pattern in which portions corresponding to the concave portions 15a to 15c are opened, and the resist is etched to form the concave portion 15 on the non-parallel bottom surface 22a.
a, the recesses 15b and 15c are respectively formed in the parallel bottom surface 22b. At this time, the non-parallel bottom surface 22a and the parallel bottom surface 2a
Protrusions 16a and 16b are formed in the remaining portion of 2b.

Next, as shown in FIG. 5A, a TiN film 23 is formed by sputtering, for example, TiN as an electrode material on the entire upper surface of the electrode substrate 2, and a resist is applied on the TiN film 23. Electrode portions 13a to 13 and projections 14a,
By forming a resist pattern in which a portion corresponding to 14b is opened, and patterning the TiN film 23 by dry etching to remove the resist, the TiN is formed on the concave portions 15a to 15c from the TiN as shown in FIG. The electrode portions 13a to 13c are formed, and the convex portions 14a and 14b made of TiN are formed on the convex portions 16a and 16b, respectively.

Next, for example, S over the entire upper surface of the electrode substrate 2
An iO ₂ film is formed, a resist is applied on the SiO ₂ film to form a resist pattern having openings wider than the electrode portions 15a to 15c and the convex portions 16a and 16b, and the resist is removed by etching. As a result, as shown in FIG. 3C, an insulating film 17 made of a SiO ₂ film is formed on the entire surface of the electrode portions 15a to 15c and the convex portions 16a and 16b to obtain the electrode substrate 2.

As described above, the concave portions 15a to 15c and the convex portions 16a and 16b are formed in one step on the bottom surface of the concave portion 11 on the electrode substrate side, and the electrode 13 is formed in the concave portions 15a to 15c, and the convex portions 16a and 16b are formed in the convex portions 16a and 16b. By forming the portions 14a and 14 collectively, the gap A can be formed between the electrode 13 and the convex portion 14 with high precision, and the diaphragm 10 can be reliably prevented from contacting the electrode 13. it can.

Next, another embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. FIG. 3 is a schematic enlarged cross-sectional explanatory view of the diaphragm in the short side direction of the embodiment. In this embodiment, the convex portions 14 are formed in the concave portions 11 of the electrode substrate 1 by the oxide film layer 2.
a. Then, as shown in FIG.
The protrusion 14 is formed higher than the electrode 13 provided on the bottom of the recess 12 formed in FIG.

Thus, when a drive waveform is applied between the diaphragm 10 and the electrode 13 such that the diaphragm 10 is displaced toward the electrode 13, the diaphragm 10 is deformed toward the electrode 13. As a result, the diaphragm 10 comes into contact with the projection 14 (the upper surface of the insulating film 17) on the electrode substrate 2 side, so that further deformation of the diaphragm 10 is limited.

Therefore, the surface of the diaphragm 10 does not come into contact with the electrode 13, and the residual charge due to the contact between the diaphragm 10 and the electrode 13 is hardly generated. The diaphragm 10
Since the convex portion 14 in contact with the convex portion 1 is electrically independent of the adjacent electrode 13 and no voltage is applied, the convex portion 1
No residual charge is generated in No. 4.

Next, still another embodiment of the present invention will be described with reference to FIGS. FIG. 7 is a schematic enlarged cross-sectional explanatory view of the diaphragm in the short side direction of the same embodiment, and FIG. 8 is an operation explanatory diagram of the same embodiment. In this embodiment, a bonding portion 25 between a diaphragm substrate 1 provided with a diaphragm 10 and an electrode substrate 2 provided with an electrode 13 is connected to the electrode 1.
3 and the same electrode material 26 and insulating film material 2 as the insulating film 17
7.

By forming the joining portion 25 between the diaphragm substrate 1 and the electrode substrate 2 using the same material as the electrode 13 and the insulating film 17, the joining portion 25 is formed in the step of forming the electrode 13 and the insulating film 17. Since it can be formed, the gap B (air gap) between the diaphragm 10 and the projection 14 can be formed with high precision.

That is, in the embodiment shown in FIG. 1, the gap B has a dimensional margin with respect to the step (gap A) between the electrode 13 and the convex portion 14, but the etching, the electrode film, and the insulating film Since the gap B is formed in three steps of formation, the gap B is formed by digging the concave portion 11 (from the substrate surface to the concave portion 11).
(Depth to the bottom surface) plus the thickness of the electrode film and the insulating film. On the other hand, if the bonding portion 15 is formed of an electrode film and an insulating film in the same manner as the protrusion 14 (electrode 13), the variation of the gap B depends on the thickness of the electrode film and the insulating film. Variations are reduced and accuracy is improved.

Next, an ink jet recording apparatus according to the present invention will be briefly described with reference to FIGS.
FIG. 9 is a schematic perspective view of the mechanism of the recording apparatus, and FIG. 10 is a side view of the mechanism.

This ink jet recording apparatus includes a carriage movable in the main scanning direction inside a recording apparatus main body 31,
A print head 32 including an ink jet head, which is a droplet discharge head according to the present invention, mounted on a carriage, a printing mechanism 32 including an ink cartridge for supplying ink to the print head, and the like are housed below the apparatus main body 31. A paper feed cassette (or a paper feed tray) 34 capable of loading a large number of papers 33 from the front side can be attached to the unit so that it can be freely inserted and removed. The manual feed tray 35 can be opened,
The paper 33 fed from the paper feed cassette 34 or the manual feed tray 35 is taken in, a required image is recorded by the printing mechanism unit 32, and then the paper discharge tray 36 mounted on the rear side.
Paper.

The printing mechanism 32 holds a carriage 43 slidably in the main scanning direction by a main guide rod 41 and a sub guide rod 42 which are guide members which are laterally mounted on left and right side plates (not shown). Include yellow (Y), cyan (C), magenta (M), and black (B
k) a head 44 composed of an inkjet head which is a droplet discharge head according to the present invention which discharges ink droplets of each color of k)
Are mounted so that the ink droplet ejection direction is directed downward, and an ink tank (ink cartridge) 45 for supplying ink of each color to the head 44 is exchangeably mounted on the upper side of the carriage 43. The ink is supplied from the ink cartridge 45 into the head 44 through the ink supply hole 18.

Here, the carriage 43 is slidably fitted on the main guide rod 41 on the rear side (downstream side in the paper conveyance direction), and the front side (upstream side in the paper conveyance direction) of the slave guide rod 4.
2 slidably mounted. In order to move and scan the carriage 43 in the main scanning direction, the main scanning motor 4
A timing belt 50 is stretched between a driving pulley 48 and a driven pulley 49 which are driven to rotate by 7, and the timing belt 50 is fixed to a carriage 53. Further, although the heads 44 of each color are used as the recording heads here, a single head having nozzles for ejecting ink droplets of each color may be used.

On the other hand, in order to transport the paper 33 set in the paper feed cassette 34 to the lower side of the head 44, a paper feed roller 51 and a friction pad 52 for separating and feeding the paper 33 from the paper feed cassette 34; , A conveying roller 54 that reverses and conveys the fed paper 33, a conveying roller 55 pressed against the peripheral surface of the conveying roller 54, and a feed angle of the paper 33 from the conveying roller 54. A prescribed tip roller 56 is provided. The transport roller 54 is driven to rotate by a sub-scanning motor 57 via a gear train.

Further, there is provided a printing receiving member 59 which is a paper guide member for guiding the paper 33 sent from the transport roller 54 below the recording head 44 in accordance with the moving range of the carriage 43 in the main scanning direction. I have. On the downstream side of the printing receiving member 59 in the paper transport direction, a transport roller 61 and a spur 62 that are driven to rotate to transport the paper 33 in the paper discharge direction are provided. Rollers 63 and spurs 64 and guide members 65 and 66 forming a paper discharge path are provided.

A reliability maintenance / recovery mechanism (hereinafter referred to as a “subsystem”) 67 for maintaining and recovering the reliability of the head 44 is disposed on the right end side in the moving direction of the carriage 43. The carriage 43 is moved to the subsystem 67 side during the standby for printing, and the head 44 is capped by the capping means or the like.

In each of the above embodiments, an example in which the droplet discharge head and the microactuator according to the present invention are applied to an electrostatic ink jet head has been described. However, the present invention is not limited to this. The present invention can be applied to a droplet discharge head that discharges a droplet, for example, a liquid resist for patterning, or can be applied to an actuator portion of a micromotor as a microactuator.

Further, the droplet discharge head has been described as a side shooter system in which the diaphragm displacement direction and the nozzle droplet discharge direction are the same, but a side shooter system in which the diaphragm displacement direction and the nozzle droplet discharge direction are orthogonal to each other. You can also.

[0046]

As described above, according to the droplet discharge head according to the present invention, since the convex portion on which the diaphragm abuts higher than the electrode is provided on the electrode side, the residual charge is reduced and the liquid droplet discharge head is stabilized. The displacement of the diaphragm is obtained.

Here, since the protrusions are formed of the same material as the electrodes, good accuracy can be ensured and reliability is improved. In addition, since the insulating film is formed on the surface of the projection, the residual charge is reduced more reliably, and stable displacement of the diaphragm can be obtained.

Further, since the joint between the substrate provided with the diaphragm and the substrate provided with the electrodes contains the same material as the electrodes, good accuracy can be ensured, and variation in displacement of the diaphragm can be suppressed.

Further, since the surface on the diaphragm side of the substrate on which the electrodes are provided is formed with irregularities on which the electrodes and projections are formed, good accuracy can be secured, residual charges are reduced, and stable displacement of the diaphragm is obtained. Can be Further, since the diaphragm and the electrodes are arranged in a non-parallel state, low voltage driving can be achieved.

According to the ink-jet head recording apparatus of the present invention, since the ink-jet head for discharging ink droplets is configured to be the liquid-droplet discharge head of the present invention, variations in the liquid-drop discharge characteristics are small, and image quality and image quality can be improved. Reliability is improved.

According to the microactuator according to the present invention, since the convex portion on which the diaphragm abuts higher than the electrode is provided on the electrode side, a microactuator capable of improving the reliability and driving stably by reducing the residual charge is provided. Obtainable.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional explanatory view of an electrostatic inkjet head to which the present invention is applied, in the direction of a long side of a diaphragm.

FIG. 2 is a schematic enlarged cross-sectional explanatory view of the head in a direction of a short side of a diaphragm.

FIG. 3 is an explanatory diagram for explaining the operation of the head.

FIG. 4 is an explanatory diagram for explaining a process of forming an electrode substrate of the head.

FIG. 5 is an explanatory view which is used to continue a step of forming an electrode substrate of the head.

FIG. 6 is a schematic cross-sectional explanatory view illustrating a droplet discharge head according to another embodiment of the present invention along the direction of the short side of the diaphragm.

FIG. 7 is a schematic cross-sectional explanatory view illustrating a droplet discharge head according to still another embodiment of the present invention, taken along a short side direction of a diaphragm.

FIG. 8 is an operation explanatory view of the embodiment.

FIG. 9 is a schematic perspective explanatory view of a mechanism section of the inkjet recording apparatus according to the present invention.

FIG. 10 is an explanatory side view of the mechanism.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... diaphragm board, 2 ... electrode board, 5 ... nozzle, 6 ... liquid chamber, 8 ... common liquid chamber, 10 ... diaphragm, 11 ... recessed part, 13 ...
Electrode, 14 ... convex part, 25 ... joint part.

Claims (8)

[Claims] 1. A diaphragm forming a wall surface of a liquid chamber communicating with a nozzle for discharging droplets, an electrode opposed to the diaphragm, and the diaphragm being deformed and displaced by electrostatic force from the nozzle. A droplet discharge head for discharging droplets, wherein a convex portion, which is higher than the electrode and is in contact with the diaphragm, is provided on the electrode side. 2. The droplet discharge head according to claim 1, wherein the protrusion is formed of the same material as the electrode. 3. The droplet discharge head according to claim 1, wherein an insulating film is formed on the surface of the projection. 4. The droplet discharge head according to claim 1, wherein a joint portion between the substrate provided with the vibration plate and the substrate provided with the electrode includes the same material as the electrode. Characteristic droplet discharge head. 5. The droplet discharge head according to claim 1, wherein a surface of the substrate provided with the electrodes on the side of the diaphragm is provided with irregularities for providing the electrodes and the projections. Droplet discharge head. 6. The droplet discharge head according to claim 1, wherein the diaphragm and the electrode are arranged in a non-parallel state. 7. An ink jet recording apparatus equipped with an ink jet head for discharging ink droplets, wherein the ink jet head is the liquid drop discharging head according to any one of claims 1 to 6. 8. A microactuator comprising a diaphragm and an electrode opposed to the diaphragm, wherein the microactuator deforms and displaces the diaphragm by electrostatic force, wherein the convex portion on the electrode side is in contact with the diaphragm higher than the electrode. A microactuator characterized by having a part.