JP4185379B2 - Image forming apparatus - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an image forming apparatus including a droplet discharge head having a multilayer electret actuator.
[0002]
[Prior art]
Micro actuators in various micro devices such as inkjet heads and other liquid ejection heads, micro pumps, micro light modulation devices, optical devices such as optical switches, micro switches (micro relays), micro flow meters, pressure sensors, micro motors, etc. Is used.
[0003]
For example, in an inkjet head used in an inkjet recording apparatus used as an image recording apparatus (image forming apparatus) such as a printer, a facsimile, a copying apparatus, or a plotter, a diaphragm is used as an actuator unit that generates energy for pressurizing ink in the ink flow path. A piezoelectric actuator such as a piezoelectric element that deforms the electrode or an electrostatic actuator is used.
[0004]
[Problems to be solved by the invention]
By the way, as an actuator capable of performing mechanical drive, there are a piezoelectric actuator mainly composed of PZT as described above and an electrostatic actuator using an electrostatic force. The former piezoelectric actuator is made of PZT containing lead. The latter electrostatic actuator has a problem that the driving force that can be generated is not so large.
[0005]
The present invention has been made in view of the above problems, and an object thereof is to provide an image forming apparatus having a novel multilayer electret actuator and excellent in droplet discharge characteristics .
[0006]
[Means for Solving the Problems]
In order to solve the above problems, an image forming apparatus according to the present invention provides:
A droplet discharge head having a multilayer electret actuator in which a plurality of inorganic electret layers are provided with electrodes interposed between layers on a diaphragm that forms the wall surface of each pressure chamber through which a plurality of nozzles that discharge droplets communicate with each other;
Driving means for applying a driving waveform to the electrodes of the multilayer electret actuator,
The drive means is configured to apply different drive waveforms to each of the plurality of electret layers.
[0007]
Here, the above inorganic electret layer of the multilayer electret actuator orientation polarization inorganic materials, ionic polarization, Ri electret layer der obtained by electronic polarization, layer electret orientation, the polarity of the polarization is reversed in the plurality of electret layers Can be configured.
[0008]
Further, the plurality of electret layers of the multilayer electret actuator can include different types of electret layers.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
First, a first embodiment of an ink jet head that is a droplet discharge head according to the present invention including a multilayer electret actuator according to the present invention will be described with reference to FIG. This figure is a cross-sectional explanatory view of the main part of the head.
[0013]
This inkjet head has a pressure chamber 5 that communicates with a nozzle 4 for ejecting ink droplets formed on the nozzle member 3 by joining the multilayer electret actuator 1, the partition member 2, and the nozzle member 3 according to the present invention. Is forming.
[0014]
Then, by driving the multilayer electret actuator 1 and pressurizing the ink in the pressure chamber 5, ink droplets (droplets) 6 can be ejected from the nozzles 4.
[0015]
Here, the multilayer electret actuator 1 is formed by laminating inorganic electret layers (inorganic material electrets) 12 and 12 in a two-layer structure on a diaphragm 11 that is a deformable member that forms the wall surface of the pressure chamber 5. By forming it with a metal-based material, it also serves as an electrode member, and by forming electrodes 13 between the inorganic electret layers 12 and 12 and on the surface of the uppermost inorganic electret layer 12, both sides of the inorganic electret layers 12 and 12 are formed. Electrodes (diaphragms) 11, 13, and 13 are formed.
[0016]
In this embodiment, the width of the inorganic electret layer 12 and the electrode 13 is narrower than the width of the pressure chamber 5. The diaphragm 11 also serves as an electrode. However, the diaphragm 11 itself can be formed of an insulating member, and the electrode can be formed on the diaphragm 11.
[0017]
Each inorganic electret layer 12 is formed by subjecting an inorganic material to orientation polarization, ion polarization, and electronic polarization.
[0018]
Inorganic materials are cationic, negative ionic materials, or anodic or negative molecular groups, or ionic elements or atomic groups with different electronegativity are crystallized to give an electric field and orientation polarization. The inorganic electret layer is formed by ion polarization and electron polarization. By applying a rectangular wave or an alternating voltage between the electrodes on both sides of the inorganic electret layer, monomorph vibration or monomorph mechanical drive occurs as a whole.
[0019]
An example of the manufacturing process of such an inorganic electret layer is demonstrated with reference to FIG.2 and FIG.3.
First, as shown in FIG. 2, for example, a fine powder (average particle size of 0.5 to 3 μm) of 2MgO · 2Al ₂ O ₃ · 5SiO ₂ composite oxide of cordierite (average particle size of 0.5 to 3 μm) is used. 3 μm) of La ₂ O ₃ mixed with 0.5 to 1 wt% of the material 22 is supplied onto the belt 23 and pressed by the press roller 24 to form a green sheet 21 having a thickness of 50 μm while controlling the layer thickness. A cover sheet 25 is supplied onto the green sheet 21 and is pressed by the pressure roller 26 to obtain a green sheet member as shown in FIG.
[0020]
Then, as shown in FIG. 3 (b), the green sheet 21 is subjected to dehydration treatment, as shown in FIG. 3 (b), primary firing is performed at 400 to 500 ° C., and as shown in FIG. 3 (d), When fired at 850 to 1200 ° C., a material 31 having high rigidity (8000 to 15000 kg / mm ² ) and large crystal distortion can be obtained. This material 31 has a mixed composition of crystalline and amorphous.
[0021]
Thereafter, metal electrodes 32 and 33 are attached to both surfaces of the material 31 as shown in FIG. 5E, and are placed in the atmosphere at 450 ° C. in the atmosphere as shown in FIG. After holding for 1 hour, as shown in (g), it is cooled while applying a DC 300 V electric field and allowed to stand until it reaches room temperature. As a result, as shown in FIG. 6H, orientation and polarization occur, the crystal part is maintained with a large strain, and an inorganic electret layer 20 that is converted into an inorganic electret with a large internal polarization is obtained. .
[0022]
Here, as described above, the basic structure of a device using this inorganic electret is, for example, a deformable member (hereinafter also referred to as “vibrating plate”), and an electrode material coated on the surface of a conductive material or an insulating material. The diaphragm is used as a lower electrode 32, and the inorganic electrode paste or sol-gel is screen printed or metal mask printed on the lower electrode 33 to form an inorganic oxide under sintering conditions. . Then, the upper electrode 33 is formed and sintered by printing a metal paste at the time of metal mask printing or after or before being divided into target elements by dry or wet etching. Under this, voltage application and heating are simultaneously performed on the upper electrodes 32 and 33 to form inorganic electrets.
[0023]
Thus, by including an electret layer obtained by orientation-polarizing, ion-polarizing, and electronically-polarizing an inorganic material, a lead-free novel actuator with high mechanical strength can be obtained.
[0024]
Here, the inorganic material includes a ferroelectric, a dielectric, or a solid electrolyte material, and further includes these particle oriented ceramics. Specific materials include ZrTiO ₄ —SnO ₂ TiO ₂ , Fe ₂ O ₃ —NiO, Zn ₂ TiO ₂ , ZnNiTiO ₄ , ZnFe ₂ O ₄ , K ₂ OAl ₂ O ₃ —SiO ₂ , CaOAl ₂ O ₃ , There are many polarizable inorganic materials such as BaTiO ₃ , Al ₂ O ₃ TiO ₂ , MgOAl ₂ O ₃ .
[0025]
Moreover, ionization and orientation polarization by a polyvalent atomic group are possible by adding a transition metal system. As a crystal structure, a spinel structure, a perovskite structure, or a sintered body is partially crystallized, and a cube, a cuboid, a rhomboid, a rhombohedron, and the like exist.
[0026]
The sintering temperature depends on the combination and composition ratio of the materials, the starting material of the raw material, and the particle dependency of the material. Although it is about 200 ° C. to 1200 ° C., good results are usually obtained at 300 ° C. to 600 ° C. Although polarization inversion occurs due to hygroscopicity or strong electric field due to applied voltage, functional deterioration occurs. Under the atmosphere control conditions in this example, the material is dehydrated and in a high oxide state, and the surface electrode metal film protection ensures reliability. The lifetime is satisfied.
[0027]
As a process, it is necessary to form a strain in a part of these crystals, but a film thickness of 1 μm to 300 μm 1 μm, a heating temperature of 300 ° C. to 400 ° C., and an applied voltage of DC 50 V to 500 V are sufficient.
[0028]
Particle oriented ceramic is obtained by first sintering sintered ionic anisotropic fine powder, then giving high-temperature pressure directionality, and secondary pressure sintering crystallization. And become polarized.
[0029]
Here again, the basic structure of the device using this inorganic electret is, for example, that a diaphragm is formed of a conductive material or an insulating material coated with an electrode material, and this is used as a lower electrode. An inorganic material paste or sol-gel is screen printed or metal mask printed, and an inorganic oxide is formed under sintering conditions. Then, after metal mask printing or after dividing into target elements by dry or wet etching, an upper electrode is formed and sintered by printing metal paste. Voltage application and heating are simultaneously performed on the upper and lower electrodes to form inorganic electrets.
[0030]
As described above, since the inorganic material includes a ferroelectric material, a dielectric material, or a solid electrolyte material, since the material itself has a dipole moment and has a polarization orientation, a large amount of displacement can be obtained.
[0031]
In addition, the target metal ions can be selectively implanted into the inorganic material with an ion implantation apparatus to form a composition.
[0032]
In general, many organic materials are caused by corona discharge. As for organic resin materials, defects are generated in the crystal structure by electron implantation or ion implantation on the surface of various blended resins such as fluorine resin, nylon (registered trademark) 11, etc. Polarization is performed.
[0033]
On the other hand, in the case of inorganic materials, the surface thermal oxide film SiO ₂ (crystalline silicon oxide film) of the silicon wafer is irradiated with an electron beam, lattice defects are generated, a charge trap layer is formed, and an electret layer is formed. be able to. However, an inorganic material has little crystal distortion due to electron implantation and almost no effect.
[0034]
Therefore, here, metal ions are implanted under reduced pressure. The manufacturing process of such an electret layer is demonstrated with reference to FIG.
First, when accelerating ions such as B, Sb, P, Ti, Bi, W, and Mn are implanted into the composite oxide 41 as shown in FIG. As shown in c), ions enter from the surface of the composite oxide 41 to about 100 to 3000 kg, but here, only the crystal distortion that is not ionized in a mixed state of metal.
[0035]
Furthermore, as shown to the same figure (d), a metal ion reaches to 0.5-10 micrometers and ionizes by performing a sintering diffusion process (heating diffusion process). Thereby, the phase effect of crystal distortion and an ionic effect can be exhibited. And as shown to the figure (e), the electrodes 32 and 33 are attached and electret-ized and the electret layer 20 is formed. In this case, a large ion polarization, charge polarization, and orientation polarization can be obtained.
[0036]
In this way, by adopting a composition in which the target metal ions are selectively implanted into the inorganic material, the ion orientation and the polarization are increased by increasing the crystal distortion and composing the introduced multivalent ions.
[0037]
In addition, as an inorganic material, a metal oxide (TiO ₂ , NiO, Al ₂ O ₃ , Fe ₂ O ₃ , MnO ₂ , Co ₂ O 3 / CoO, Sn ₂ O ₃ / SnO, ZnO, etc.) or an alkaline earth element compound ZrTiO ₄ —SnO ₂ TiO ₂ , Fe ₂ O ₃ —NiO, Zn ₂ TiO ₂ , and ZnNiTiO containing oxides (BaO, K ₂ O, CaO, MgO, etc.) and ferroelectric, dielectric, or solid electrolyte materials ₄ , a mixed composition of polarizable inorganic materials such as ZnFe ₂ O ₄ , K ₂ OAl ₂ O ₃ —SiO ₂ , CaOAl ₂ O ₃ , BaTiO ₃ , Al ₂ O ₃ TiO ₂ , MgOAl ₂ O _3, etc. Can be used.
[0038]
In particular, a compound of an alkaline earth element is a material whose element ion group functions as a cation, other inorganic materials function as negative ions, has high crystallinity, and high ion orientation. A highly ionic material can be obtained by controlling the redox atmosphere during firing of the composite oxide.
[0039]
The concept of this form is shown in FIG. The example in the figure is an example of polarization due to the negative degree of ion groups, and orientation and polarization easily occur. Actually, a composite salt material such as Mg ₂ Al ₂ O ₄ , K ₂ SiO ₃ , or BaFe ₂ O ₄ is polarized at a high temperature and an electric field.
[0040]
In this manner, by setting the inorganic material to include a metal oxide or an alkaline earth metal oxide, ion and charge polarization can be increased.
[0041]
Furthermore, ZrTiO ₄ —SnO ₂ TiO ₂ , Fe ₂ O ₃ —NiO, Zn ₂ TiO ₂ , ZnNiTiO ₄ , ZnFe ₂ O ₄ , K ₂ OAl ₂ O ₃ —SiO ₂ , CaOAl ₂ O ₃ , BaTiO ₃ , Al ₂ O ₃ TiO ₂ , MgOAl ₂ O _{3 and} other polar inorganic materials and non-metallic elements SiO ₂ , B ₂ O ₃ , P ₂ O ₅ , Sb ₂ O ₅ , Bi ₂ O ₃ ) (V ₂ O ₅ , Cr ₂ O ₃ , CuO, Y ₂ O ₃ , Zr ₂ O ₃ , Nb ₂ O ₃ , Mo ₂ O ₃ , PD ₂ O ₃ , La ₂ O _3, etc., hybridized Oxides can be used, and valence control is easy depending on the firing state and atmosphere of the composite oxide containing this transition element, which consequently controls the magnitude of crystal distortion. Can.
[0042]
A conceptual diagram of this form is shown in FIG. Mixed oxides of inorganic dielectrics, polyvalent non-metallic elements, and transition elements are easily baked, especially because polyvalent atoms and transition elements have a low second ionization potential. , Orientation polarization occurs.
[0043]
As described above, by adopting a structure in which the inorganic material is a composite oxide including a transition metal oxide, unbound ions can be held in the crystal of the polyvalent element, and a large ionic polarization can be obtained.
[0044]
Next, the film formation of the inorganic material in the inorganic electret layer will be described.
For example, a vapor deposition method can be used. In this case, as shown in FIG. 7, for example, as shown in FIG. 7, a plasma CVD apparatus is used. In a chamber 52 that holds a substrate 51 that constitutes a base electrode by decompressing and heating an organic metal or chloride with high sublimability of an inorganic material. And is brought into contact with plasma or an oxidation reaction gas to cause vapor phase growth. In the figure, 53 is a nozzle, 54 is an anode, 55 is a cathode, 56 is a motor, 57 is a heater, and 58 is a sliding contact. An outline of the parallel plate electrode type plasma CVD apparatus is shown in FIG.
[0045]
Alternatively, a vapor deposition method can be used. In this case, the target inorganic material or metal is heated and sublimated, an oxidizing gas is introduced into the chamber, and a film is formed by vapor deposition.
Further, in sputtering, the metal material is subjected to discharge sputtering with a DC power source and a sputtering gas (Ar, He, N2 and further O ₂ added), and the non-conductive inorganic material is subjected to the same sputtering gas using a high frequency power source. RF sputtering can be performed.
[0046]
The CVD apparatus and the sputtering apparatus are suitable for forming a thin film, and the film growth is about 10 to 300 cm / min. In addition, the film can be easily formed while the crystal is grown by heating the substrate.
[0047]
When forming a film using any of these methods, a single layer or multiple layers are formed according to the purpose, and substrate heating and reaction gas are introduced at the time of film formation to form oxides or nitrides by plasma reaction. And control the crystallinity and amorphousness.
[0048]
In this case, since the thin film to be formed is flat, the upper electrode is then formed by a vapor deposition method or a photolithography method to form an inorganic electret layer by heating and an electric field.
[0049]
In addition, since the polarization effect is large due to the thin film, when the elements are made multi-layered as an actuator, the upper electrode is only individualized, and the mutual interference between the elements is small without dividing the elements, and the conventional dividing process is unnecessary. And fine division is possible.
[0050]
In this way, an inorganic material is deposited on a substrate by vapor deposition or vapor deposition, and the substrate is heated and a reaction gas is introduced at the time of film formation to form an oxide or nitride to form a crystal. By forming the electret layer by controlling the property or the amorphous property, the crystallinity or the amorphous property can be easily controlled.
[0051]
Next, a second embodiment of an ink jet head that is a droplet discharge head according to the present invention including a multilayer electret actuator according to the present invention will be described with reference to FIG. This figure is a cross-sectional explanatory view of the main part of the head.
In this embodiment, the drive region (part) of the multilayer electret actuator 1 is restricted by the electrode 13 by making the width (region) of the electrode 13 serving as the drive electrode smaller than the width of the pressure chamber 5. That is, the region where the electrode 13 is formed becomes a vibration region.
[0052]
When configured in this manner, mutual interference is reduced, and a multi-driving element can be easily obtained by providing independent electrodes 13 corresponding to each pressure chamber 5 without dividing the inorganic electret layer 12 into each channel. Can do.
[0053]
Next, a third embodiment of an ink jet head that is a liquid droplet ejection head according to the present invention including a multilayer electret actuator according to the present invention will be described with reference to FIG. This figure is a cross-sectional explanatory view of the main part of the head.
This ink jet head has a pressure chamber 5 communicating with a nozzle 4 for discharging ink droplets formed on the nozzle member 3 by joining the multilayer electret actuator 61 according to the present invention, the partition member 2 and the nozzle member 3. Is forming.
[0054]
Ink droplets (droplets) 6 can be ejected from the nozzles 4 by driving the multilayer electret actuator 61 to pressurize the ink in the pressure chamber 5.
[0055]
Here, the multi-layer electret actuator 61 includes an inorganic electret layer (inorganic material electret) 12 n layers (n> 2, n = 6 layers here) on the diaphragm 11 which is a deformable member forming the wall surface of the pressure chamber 5. In the laminated structure, the diaphragm 11 is made of a metal material so that it also serves as an electrode member, and an electrode is formed between the inorganic electret layers 12 and 12 and on the surface of the uppermost inorganic electret layer 12. By forming 13, electrodes (vibrating plates) 11, 13, 13 are formed on both surfaces of the inorganic electret layers 12, 12. Other configurations are the same as those in the first embodiment.
[0056]
The multilayer electret actuator 61 of this embodiment has a higher rigidity and a higher resonance frequency by increasing the number of layers compared to the multilayer electret actuator 1 of the first and second embodiments that performs bimorph drive. Thus, high frequency driving is possible and a large driving force can be obtained.
[0057]
The manufacturing process of the multilayer electret actuator 61 is the same as that described in the first embodiment. That is, in the method described in the first embodiment, the same inorganic material electret layer is made into a multilayer, and the manufacturing method is patterned on the diaphragm by a general inorganic material sol-gel or a primary firing material thin film screen printing method. And crystallization by firing. In addition, it is possible to produce a crystal growth and lamination in a vacuum space by a dry method such as lamination and firing crystallization of a known thin film green sheet or CVD.
[0058]
In particular, the dry vacuum deposition method has the following parameters, and the ratio of crystals and amorphous can be controlled by selecting and selecting the factors for forming the inorganic electret material. In other words, bias is applied to the substrate heating temperature and RF (radio frequency) plasma, and ion species selection and ion species implantation into the substrate synergize crystallinity control and rigidity improvement in bonding and impact migration, and natural vibration. The number is high, and high frequency driving becomes possible. This is particularly effective when the high-viscosity ink or actuator drive displacement is increased and high-frequency drive is required.
[0059]
Next, a fourth embodiment of an ink jet head that is a liquid droplet ejection head according to the present invention including a multilayer electret actuator according to the present invention will be described with reference to FIG. This figure is a cross-sectional explanatory view of the main part of the head.
[0060]
In the third embodiment, the driving region (part) of the multilayer electret actuator 61 is reduced in the third embodiment by making the width (region) of the electrode 13 smaller than the width of the pressure chamber 5 as in the second embodiment. It is restricted by the electrode 13. That is, the region where the electrode 13 is formed becomes a vibration region. Thereby, the operation and effect of the second and third embodiments can be obtained.
[0061]
Next, an embodiment of an image forming apparatus including a drive device for a multilayer electret actuator according to the present invention will be described with reference to FIG. This figure is a cross-sectional explanatory view of the main part of the head.
In this image forming apparatus, the vibration plate 11 that also serves as an electrode of the multilayer electret actuator 61 that is an actuator section and the driving unit 71 that applies a driving waveform capable of adjusting driving parameters such as duty, driving voltage, and pulse width to each electrode 13 are provided. I have.
[0062]
That is, when a multi-nozzle inkjet head is configured, if the pixel size for each channel is different, it is necessary to adjust the ink ejection droplet amount. In this case, the ink droplet amount can be changed by adjusting or changing the duty of the drive waveform (drive pulse).
[0063]
Therefore, by using the multilayer electret actuator 61 according to the present invention for the actuator section, the control range is increased, and the polarity of the drive pulse with respect to the drive electrode of each actuator section is changed as necessary, or the number of layers to be driven The drive displacement of each actuator unit is adjusted by increasing / decreasing the value, changing the duty of the drive waveform, or changing the drive voltage.
[0064]
As a result, the size of the ink droplets can be controlled to change the pixel dot size, so that variations in droplets between channels can be reduced, or gradation can be expressed by changing the dot size. become.
[0065]
For example, in FIG. 12, with respect to three layers of electrodes 13, the upper layer, the middle layer, and the lower layer electrode 13 are electrode EL1, EL2, EL3, and vibration plate 11 is electrode EL4, respectively, and driving for each electrode EL1, EL2, EL3, EL4 is performed. For example, when the waveform is changed as shown in patterns (1) to (6) as shown in FIG. 13, the displacement amount of the multilayer electret actuator 61 is changed to patterns (1) to (6) as shown in FIG. Will change accordingly.
[0066]
Here, assuming that the potential (absolute value) of the driving waveform is Vh, Vm, Vl (Vh>Vm> Vl), the pattern {circle around (1)} is set to each electrode EL1 = + Vh, EL2 = + Vm, EL3 = + Vl, EL4 = 0. Example, pattern (2) is an example in which each electrode EL1 = −Vh, EL2 = −Vm, EL3 = −Vl, EL4 = 0, and pattern (3) is each electrode EL1 = −Vm, EL2 = −Vl, EL3 = 0, EL4 = + Vl, pattern {circle over (4)} is each electrode EL1 = + Vl, EL2 = 0, EL3 = + Vl, EL4 = 0, pattern {circle over (5)} is each electrode EL1 = 0, EL2 = + Vl, An example in which EL3 = 0 and EL4 = + Vl, pattern {circle around (6)} is each electrode EL1 = + Vh, EL2 = + Vm, EL3 = + Vl, EL4 = 0, and the pulse width Pw is changed to patterns {circle around (1)} to {circle around (5)}. Compared to twice It is.
[0067]
As a result, pattern (1) is pull-push, (2) is push, (3) is push, (4) is pull-push, (5) is push, and (6) is pull-push. In the patterns (1) to (3), substantially the same amount of displacement can be obtained,
[0068]
Next, a fifth embodiment of an ink jet head which is a liquid droplet ejection head according to the present invention including a multilayer electret actuator according to the present invention will be described with reference to FIG. This figure is a cross-sectional explanatory view of the main part of the head.
[0069]
In the multilayer electret actuator 81 of this embodiment, inorganic electret layers 15 and 16 of different inorganic materials are laminated on the diaphragm 11, and the drive region is defined by the width of the electrode 13.
[0070]
In this case, the dissimilar inorganic material electret layers are formed in two layers, and the strain rate of the two different materials is changed. For example, a combination of a material having a large amount of strain and a material having a small amount of strain can increase the amount of displacement. The target displacement amount can be adjusted. Further, by making the material having different rigidity into two layers and reducing the rigidity of the strained material on the barrier layer (partition wall) side between the adjacent channels, the mutual interference of the drive displacement to the adjacent channels can be reduced.
[0071]
Here, the inorganic electret layer 15 of the partition wall member 2 is laminated with a low rigidity and the inorganic electret layer 16 is laminated with a high rigidity so that vibration during driving is attenuated and mutual interference is reduced. .
[0072]
Next, with reference to FIG. 16, a sixth embodiment of an ink jet head which is a droplet discharge head according to the present invention including a multilayer electret actuator according to the present invention will be described. This figure is a cross-sectional explanatory view of the main part of the head.
In this embodiment, as the inorganic electret layers 92 to 95 constituting the multilayer electret actuator 91, the electret materials are different, or the electret orientation and the polarity of polarization are not all forward but part are reverse. Here, the inorganic electret layers 92 and 95 are in the forward direction, and the inorganic electret layers 93 and 94 are in the reverse direction.
[0073]
By including layers with different electret orientation and polarization polarity in the multilayer inorganic electret layer in this way, ink droplets can be controlled by matching with the pulse pattern at the time of driving. It can be optimized.
[0074]
FIGS. 17 and 18 show different examples of the multi-nozzle inkjet head using the multilayer electret actuator as described above. FIG. 17 shows an example of multi-practice in the first embodiment, and FIG. 18 shows an example of multi-ply in the second embodiment. Note that the present invention can be applied not only to ink but also to a droplet discharge head that discharges liquid.
[0075]
【The invention's effect】
As described above, according to the image forming apparatus of the present invention , a plurality of inorganic electret layers are arranged between the electrodes on the diaphragm that forms the wall surface of each pressure chamber through which a plurality of nozzles that discharge droplets communicate. A droplet discharge head having a multi-layer electret actuator provided with a drive means, and a drive means for applying a drive waveform to the electrodes of the multi-layer electret actuator, and the drive means is provided for each of the plurality of electret layers. Since different driving waveforms are applied, an image forming apparatus having a novel multilayer electret actuator and excellent in droplet ejection characteristics can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional explanatory view of a principal part of a first embodiment of an ink jet head which is a droplet discharge head according to the present invention including a multilayer electret actuator according to the present invention. FIG. 2 is a process for manufacturing an inorganic electret layer of the multilayer electret actuator. FIG. 3 is an explanatory diagram for explaining an example of the process. FIG. 3 is an explanatory sectional view for explaining the process following FIG. 2. FIG. 4 is an explanatory sectional view for explaining another manufacturing process of the inorganic electret layer. FIG. 6 is a conceptual diagram for explaining another inorganic electret layer. FIG. 7 is a schematic diagram of a CVD apparatus for explaining another manufacturing process of the inorganic electret layer. FIG. 8 is a schematic explanatory view of another example of the CVD apparatus. FIG. 9 is a cross-sectional view of a principal part of the second embodiment of the inkjet head. FIG. 10 is a cross-sectional explanatory view of the main part of the third embodiment of the inkjet head. FIG. 11 is a cross-sectional explanatory view of the main part of the fourth embodiment of the ink-jet head. FIG. 13 is an explanatory diagram for explaining an example of different driving waveforms for electrodes of a multilayer electret actuator. FIG. 14 is an explanatory diagram for explaining a displacement amount in each pattern of FIG. 15 is a cross-sectional explanatory view of the main part of the fifth embodiment of the inkjet head. FIG. 16 is an explanatory cross-sectional view of the main part of the sixth embodiment of the ink-jet head. 18] Explanatory drawing explaining another example of a multi-nozzle head [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1, 61, 81, 91 ... Multi-layer electret actuator, 2 ... Partition member, 3 ... Nozzle plate, 4 ... Nozzle, 11 ... Vibration plate, 12 ... Inorganic electret layer, 15, 16, 92-95, 13 ... Electrode,

Claims (3)

A droplet discharge head having a multilayer electret actuator in which a plurality of inorganic electret layers are provided with electrodes interposed between layers on a diaphragm that forms the wall surface of each pressure chamber through which a plurality of nozzles that discharge droplets communicate with each other;
Driving means for applying a driving waveform to the electrodes of the multilayer electret actuator,
The image forming apparatus, wherein the driving unit applies different driving waveforms to each of the plurality of electret layers. The image forming apparatus according to claim 1, wherein the inorganic electret layer orientation polarization inorganic material of the multilayer electret actuator, ionic polarization, Electronically polarized electret layer der allowed, said in a plurality of electret layers electret orientation An image forming apparatus comprising a layer having a reversed polarity of polarization. The image forming apparatus according to claim 1, wherein the plurality of electret layers of the multilayer electret actuator include different kinds of electret layers.

Images