JP5112094B2 - Electrostatic actuator, droplet discharge head, image forming apparatus, and manufacturing method of electrostatic actuator - Google Patents

Description

  The present invention relates to an electrostatic actuator, a droplet discharge head, an image forming apparatus, and a method for manufacturing the electrostatic actuator.

  2. Description of the Related Art In printers and facsimile machines linked to personal computers, an image forming apparatus having a droplet discharge head called an ink jet head is often used for forming characters and images. Among droplet discharge heads, there is an electrostatic actuator using electrostatic force as an actuator for droplet discharge. In a droplet discharge head using an electrostatic actuator, the dimension (gap length) accuracy of the gap (gap) between the diaphragm and the electrode greatly affects its discharge characteristics. If the variation in the discharge characteristics of each actuator is large, the printing accuracy and the reproducibility of the image quality will be significantly reduced. In order to reduce the operating voltage, the gap interval must be about 0.1 to 0.5 μm, and higher dimensional accuracy is required.

  In an electrostatic actuator, in order to eliminate the differential pressure between the pressure in the air gap and the atmospheric pressure, to prevent wetting in the air gap and to maintain the reliability of the actuator, air and gas are introduced into the air gap. A communication path that communicates with each gap may be provided. For example, as disclosed in Patent Document 1, in order to form a hydrophobic film inside the vibration chamber (gap) between the diaphragm and the fixed electrode, a communication path is provided for communicating the outside of the actuator with each vibration chamber. An electrostatic actuator having a structure in which a raw material gas for forming a hydrophobic film is introduced into a vibration chamber through this communication path to form a hydrophobic film, and then the communication path is sealed with a sealing material is known.

  Further, as disclosed in Patent Document 2, in order to perform the hydrophobization process in the vibration chamber (gap) in a short time and reduce the variation in the processing conditions for each vibration chamber, a plurality of electrodes each serving as the vibration chamber 2. Description of the Related Art An electrostatic actuator is known in which a concave portion for use is communicated with one treatment agent injection hole and a groove portion, and individual actuator units are arranged symmetrically about the treatment agent injection hole as a center of symmetry. .

  Further, as disclosed in Patent Document 3, in an electrostatic actuator in which a void is formed with high accuracy using a sacrificial layer process, in order to efficiently introduce a gas for forming a hydrophobic film into a vibration chamber, Forming a portion for arranging the common communication path when patterning the electrode forming layer of each actuator unit, forming an opening in the insulating film where the common communication path of the insulating film on the electrode forming layer is formed, A common communication path forming portion is formed in the sacrificial layer deposited thereon. An electrostatic actuator that forms a common communication path that is higher in height (wider in cross-sectional area) than the air gap by removing the common communication path formation portion formed by the electrode formation layer and the sacrificial layer by sacrificial layer etching. Are known.

  Further, as disclosed in Patent Document 4, when the air opening hole of the communication path of the gap is sealed with the sealant, the sealant reaches the inside of the gap through the communication path by capillary action, and is normal. In order to prevent the operation from being disabled, there is known an electrostatic actuator in which a meandering passage is formed which serves as a resistance against the inflow of the sealing agent for sealing the air opening hole into the common communication passage.

When the electrostatic actuator is used as the operating pressure generating means of the droplet discharge head as in the examples shown in Patent Document 3 and Patent Document 4, the elution of the vibration plate component into the discharge liquid and the vibration plate and the discharge liquid are prevented. In many cases, a protective film (also referred to as a liquid contact film) is formed on the surface of the diaphragm. There are various kinds of wetted films and film forming techniques. One of the most prominent ones is a method of forming a resin film such as polyimide or polybenzoxazole by a coating method. In terms of material, it has a high durability and wettability with respect to the discharged liquid, but since it is a resin film, it has a low Young's modulus and can be formed relatively thickly. If there are some irregularities on the surface or extremely small particles, there is an advantage that no pinholes are generated. (If a film having a large Young's modulus is formed thickly, the vibration plate becomes too rigid and cannot be driven at a low voltage.) As a film forming method, a coating method can be formed at low cost. There is a merit that it is possible.
Japanese Patent Laid-Open No. 11-263012 JP 2007-035853 A JP 2006-115624 A JP 2007-077784 A

  As in the electrostatic actuators disclosed in Patent Documents 1 and 2, when two substrates are bonded together to form a gap, the completed electrostatic actuator is usually removed by bonding under reduced pressure or at a high temperature. When returned to the environment, the pressure in the gap is reduced. Thus, when the gap internal pressure is different from the external pressure (atmospheric pressure), the diaphragm is bent toward the gap due to the pressure difference between the inside and outside. If a protective film or the like is applied to the surface of the diaphragm while the diaphragm is bent, the wetted film thickness tends to be non-uniform. After that, even if the air gap is communicated with the outside world and the inside of the air gap is the same as the external pressure (atmospheric pressure), the deflection of the diaphragm is completely restored due to the non-uniformity of the wetted film thickness and the film stress Often not. In principle, the height of the gap may be set in advance in consideration of the amount of bending, but in practice, this situation must be avoided because the variation increases.

Further, the internal pressure of the air gap may be different from the external pressure (atmospheric pressure) during the manufacturing process of the electrostatic actuator. For example, in the electrostatic actuator manufacturing methods shown in Patent Documents 3 and 4, the gap is formed by a sacrificial layer process, and then the sacrificial layer removal hole is sealed with a sealing film formed by CVD or the like. In the state, the inside of the gap is decompressed. (Of course, when the film is formed by a reduced pressure process, the pressure is reduced when the film is formed by a high temperature process even if it is a normal pressure process.)
Therefore, as disclosed in Patent Document 4, a liquid contact film is formed in a state where an air opening hole communicating with the air gap is opened, the air pressure in the air gap is the same as the external pressure (atmospheric pressure), and the diaphragm is not bent. It is desirable to apply. It is also possible to seal the air opening hole with the liquid contact film simultaneously with the liquid contact film formation. However, the wetted film material is selected with the focus on preventing the elution of the diaphragm into the discharge liquid and ensuring the wettability with the discharge liquid. Therefore, the sealing property may not be sufficiently obtained by such a method. Further, the material (solvent) of the liquid contact film is sealed in the gap, which may cause the inhibition of hydrophobicity or the generation of foreign matter.

  On the other hand, the problem can be avoided by forming the wetted film after previously sealing with another sealing agent before forming the wetted film as in another method disclosed in Patent Document 4. However, when the sealant is formed so as to rise from the substrate surface, it causes non-uniformity in the coating film thickness when the wetted film is applied. In addition, since the liquid contact film is formed after the inside of the gap is hydrophobized, there are restrictions on the combination of the liquid contact film, the hydrophobic agent, and the sealing material. For example, when the above-described polyimide or polybenzoxazole is formed by a coating method, it is necessary to polymerize the precursor by applying the precursor and then baking at a temperature of 300 ° C. or higher, so that it can withstand that temperature. There is a restriction that it must be a hydrophobic agent or a sealing material.

  The case where the electrostatic actuator is used as the discharge pressure generating means of the droplet discharge head and the liquid contact film is formed on the surface of the vibration plate has been described. However, even when the electrostatic actuator is used for other purposes, vibration Similar problems occur when a coating film, which is a protective film, is formed on the plate surface.

  As described above, it is not easy to provide an electrostatic actuator that forms a uniform protective film on the surface of the diaphragm and exhibits a predetermined operation capability with respect to a predetermined applied voltage.

  In view of the above-described problems, the present invention provides an electrostatic actuator that has a uniform protective film on the surface of the diaphragm and has excellent operating characteristics, a liquid droplet ejection head including the electrostatic actuator, an image forming apparatus, It is another object of the present invention to provide a method for manufacturing an electrostatic actuator.

The present invention includes a vibrating plate forming a protective film on the surface includes a diaphragm electrode, a fixed electrode that are opposed to each other through a gap the diaphragm, provided with a communication passage communicating with the air gap, the protective layer The diaphragm including includes a first opening hole and a second opening hole that open the communication path to the atmosphere, and the second opening hole is formed to penetrate to the protective film, and The sealing material that is formed closer to the gap than the first opening hole and hermetically seals the second opening hole shuts off the communication portion with the second opening hole of the communication path, and An electrostatic actuator , wherein the protective film is a thermosetting protective film precursor heat-cured resin film, and the gap includes a hydrophobic film that desorbs or decomposes at a curing temperature of the protective film It is.

A preferred aspect of the present invention is an electrostatic actuator comprising a plurality of the electrostatic actuators , wherein the communication paths of the electrostatic actuators communicate with each other .

In a preferred aspect of the present invention, the electrostatic actuator is characterized in that the first opening hole is sealed with the protective film.

In a preferred aspect of the present invention, the electrostatic actuator is characterized in that the sealing material is an epoxy resin .

  The present invention is a droplet discharge head including the electrostatic actuator of the present invention, and discharging a droplet from a nozzle by operating the electrostatic actuator.

  The present invention is an image forming apparatus in which the droplet discharge head of the present invention is mounted and an image is formed by ejecting droplets onto a recording material by the droplet discharge head.

In the present invention, a fixed electrode, a sacrificial layer, and a diaphragm including a diaphragm electrode are laminated on a substrate, and then the sacrificial layer is removed by introducing an etching agent into the sacrificial layer, and communicated with the gap and the gap. and the electrostatic actuator structure formation step of forming a communicating path that, in the diaphragm, a first opening hole forming step of said communication passage providing a first vent hole that communicates to the atmosphere, the surface of the diaphragm A protective film forming step in which a thermosetting protective film precursor is applied and cured by heating to form a protective film, and the communication path is communicated with the atmosphere on the surface of the diaphragm on which the protective film is formed . a second opening hole forming step of providing a second vent hole, from the second open hole, the hydrophobic agent introducing step for introducing a hydrophobic agent into the gap through the communicating passage, said second opening hole and characterized in that it comprises a second opening hole sealing step of sealing with a sealing material, a That is a manufacturing method of the electrostatic actuator.

In a preferred aspect of the present invention, the protective film forming step includes a discharge fluid through hole forming step of forming a discharge fluid through hole through which the discharge fluid flows.

In a preferred aspect of the present invention, the protective film forming step includes a first open hole sealing step of sealing the first open hole .

  According to the present invention, an electrostatic actuator having a uniform protective film on the vibration plate surface and having excellent operating characteristics, a droplet discharge head including the electrostatic actuator, an image forming apparatus, and an electrostatic actuator The manufacturing method of can be provided.

  An electrostatic actuator according to the present invention includes a diaphragm including a diaphragm electrode, and a fixed electrode disposed opposite to the diaphragm via a gap, and the diaphragm is disposed on a surface that transmits vibration pressure. A protective film is formed. A communication passage communicating with the gap is formed, and the communication passage includes a first opening hole and a second opening hole, and the first opening hole is sealed by the first sealing member. The second open hole is sealed with a second sealing member made of a material different from that of the first sealing member. Note that the first open hole is formed so that the communication path is opened to the atmosphere when not sealed by the first sealing member.

  FIG. 1 shows a partial cross-sectional view of the electrostatic actuator of the present invention. The electrostatic actuator of the present invention will be described with reference to FIG. The electrostatic actuator 2 of the present invention is formed on an electrostatic actuator substrate 10, and a fixed electrode 12, a gap 14 a, a diaphragm electrode 22, A diaphragm including the tensile stress film and the 24 protective film 26 is formed. This part functions as an electrostatic actuator. In order to form the gap 14a, spacers 14b (also referred to as sacrificial layers) are disposed between the fixed electrode 12 and the diaphragm electrode 22 on both sides of the gap 14a. A communication passage 56 is formed in the spacer 14b.

  When there are a plurality of pairs of fixed electrodes 12 and diaphragm electrodes 22 (this pair is referred to as an electrostatic actuator element) opposed to each other across the gap 14a on the substrate 10, the communication path 56 is an electrostatic type of these. The air gaps 14a in the actuator element communicate with each other. Further, the communication path 56 communicates with the first opening hole 55a and the second opening hole 55b. However, in the electrostatic actuator 2 as a finished product, the first opening hole 55a and the second opening hole 55b are sealed by the first sealing member 58a and the second sealing member 58b, respectively. . In particular, the second sealing member 58b also blocks the communication path 56. The first opening hole 55a is disposed at a position farther from the gap 14a than the position at which the second opening hole 55b is disposed on the communication path 56. That is, the communication path 56 connecting the first open hole 55a and the gap 14a is blocked by the second sealing member 58b.

  In such a configuration, if the second sealing member 58b is formed of a highly airtight material, the airtightness of the gap 14a is sufficiently maintained regardless of the airtightness of the first open hole 55a. Be drunk. For this reason, the first sealing member 58a can be simultaneously formed in the step of applying the protective film 26 to the diaphragm.

  Next, the electrostatic actuator of the present invention having a plurality of electrostatic actuator elements will be described with reference to FIG. FIG. 2 shows a plurality of electrostatic actuator elements 3 each having a diaphragm and a fixed electrode that are disposed opposite to each other with a gap on the substrate 10, and the gaps of the respective electrostatic actuator elements 3 are connected to the communication path. FIG. 6 is a schematic view close to a plan view showing the electrostatic actuator 2 of the present invention communicated by 56;

  The electrostatic actuator 2 is an electrostatic actuator including a plurality of electrostatic actuator elements, and the plurality of electrostatic actuator elements 3 are arranged in parallel on the actuator substrate 10. The gaps 14a of the respective electrostatic actuator elements 3 (in FIG. 2, the electrostatic actuator elements 3 and the gaps 14a are connected to the communication paths 56 arranged so as to be orthogonal to the rows of the electrostatic actuator elements 3. The ends of the two are communicating. The first open hole 55a and the second open hole 55b are arranged in this order from the end side of the communication path 56 in the communication path 56 extending to the end on the actuator substrate 10.

  When the electrostatic actuator 2 is manufactured, the first opening hole 55a and the second opening hole 55b adjust the atmospheric pressure by introducing air into the gap 14a, or introduce a water-repellent material. It is not necessary to form it for each electrostatic actuator element 3 and should be sealed after the electrostatic actuator 2 is manufactured. Preferably there is.

  If the first sealing member 58a is formed of the same material as the protective film 26, the manufacturing process of the electrostatic actuator 2 is facilitated.

  Further, if the second opening hole 55b is formed between the communication part between the first opening hole 55a and the gap 14a in the communication passage 56, the first sealing member 58a and the second sealing member 58b are connected to each other. The range of selection is widened, and the manufacturing method of the electrostatic actuator 2 is facilitated.

(Embodiment 1)
Embodiment 1 is a droplet discharge head according to the present invention, which uses an electrostatic actuator according to the present invention as pressure generating means. FIG. 3 shows an exploded perspective view of the droplet discharge head according to the first embodiment. FIG. 4 shows a plan view of a part of the droplet discharge head. However, this plan view is shown through the inside. 5 to 8 are cross-sectional views taken along lines XX ′, Y1-Y1 ′, Y2-Y2 ′, and Y3-Y3 ′ in FIG. 4, respectively. The droplet discharge head 1 of Embodiment 1 and the electrostatic actuator of the present invention incorporated therein will be described with reference to FIGS.

  The droplet discharge head 1 includes a nozzle plate 40, a liquid chamber substrate 30, an actuator substrate 10, a frame (not shown), a flexible printed circuit (FPC), and a driver IC. In the assembled state, the nozzle plate 40, the liquid chamber substrate 30, and the actuator substrate 10 are stacked and bonded with an adhesive.

  The nozzle plate 40 is a polyimide film having a water repellent film coated on the surface side (upper surface in FIG. 2), and the nozzle holes 41 are opened by laser processing after the nozzle plate 40 is bonded to the liquid chamber substrate 30. Is.

  As the liquid chamber substrate 30, a silicon substrate having a crystal axis of [110] in X-ray diffraction is used, and a pressurized liquid chamber 33, a low flow resistance portion 32, and a common liquid chamber 31 are formed on the surface opposite to the nozzle plate 40. Has been. Further, a communication pipe 34 for communicating the nozzle hole 41 and the pressurized liquid chamber 33 is formed by penetrating the liquid chamber substrate 30 from the pressurized liquid chamber 33 to the nozzle plate 40 side. By adopting such a configuration, the height of the pressurized liquid chamber can be made lower than the thickness of the liquid chamber substrate 30, and the liquid chamber substrate 30 having a thickness that is easy to handle at the time of manufacture is used. The height of the pressurized liquid chamber 33 can be set so as to obtain optimum discharge characteristics.

  Since a silicon substrate having a crystal axis of [110] is used, as is well known, the pressurized liquid chamber and the like can be processed with high precision by anisotropic etching. In addition, after forming the pressurized liquid chamber 33 and the like, an oxide film is formed on the surface by thermal oxidation to improve the wettability and prevent the silicon of the substrate material from being corroded by the discharge liquid (ink). At this time, although not shown, a dummy pattern is provided on the nozzle bonding surface side of the liquid chamber substrate 30 to prevent the substrate from warping due to internal stress of the oxide film after thermal oxidation.

  The actuator substrate 10 is a silicon substrate having a crystal axis of [100], and is formed with an electrostatic actuator including the diaphragm 20, the gap 14 a, and the fixed electrode 12 so as to correspond to the pressurized liquid chamber 33. . This electrostatic actuator can be formed by highly integrated processing with low power consumption using MEMS processing technology. In addition, the actuator substrate 10 is formed with a communication passage 56 that communicates the gaps with each other in the nozzle arrangement direction. At the ends of the communication passage 56, atmospheric release portions 55 a and 55 b for opening the communication passage to the atmosphere. It is communicated to. The atmosphere opening portions 55a and 55b are sealed with a sealing material after the actuator substrate 10 is formed.

  In this electrostatic actuator, a liquid supply path 57 is formed so as to penetrate the actuator substrate 10 in order to supply the discharge liquid from the outside of the actuator substrate 10 (the side opposite to the liquid chamber substrate).

The diaphragm 20 is formed of a laminated film, and includes the following five layers from the gap 14a side.
Diaphragm side insulating film 21 (silicon oxide film): prevention of short circuit when the diaphragm and the counter electrode are in contact with each other. Diaphragm electrode 22 (arsenic doped polysilicon film): electrostatic force applied with voltage between the counter electrode. Electrode and tensile stress film 24 (silicon nitride film) for generating cracks: By making the diaphragm as a whole a tensile stress, it is made to be in an unbent state and secures a repulsive force during driving and sacrificial layer removal hole sealing Stop film 25 (silicon oxide film): sealing of the sacrificial layer removal hole (also serves to prevent cracking of the tensile stress film 24 (silicon nitride film)).
Diaphragm wetted film 26 (PBO film): Protective film for preventing corrosion of diaphragm by ink (PBO; Polybenzoxazole)
In addition, a silicon oxide film may be provided between the diaphragm electrode 22 and the tensile stress film 24 as a deflection preventing film of the diaphragm 20.

  Phosphorous-doped polysilicon is used for the fixed electrode 12, and a silicon oxide film is formed as an insulating film on the gap side. A silicon oxide film is also formed as the substrate insulating film 11 between the fixed electrode 12 and the actuator substrate 10 to ensure insulation between the fixed electrode 12 and the actuator substrate 10.

  The air gap 14a and the communication path 56 are formed by a sacrificial layer process using polysilicon as a sacrificial layer (the sacrificial layer removal hole and the detailed structure around it are not shown, but as described in Patent Documents 3 and 4). You can refer to these well-known techniques.) As for the communication path 56, the polysilicon of the fixed electrode is also used as the sacrifice layer 14 b for forming the communication path, thereby increasing the conductance of the communication path 56. The diaphragm electrode 22 and the fixed electrode 12 are made of polysilicon like the sacrificial layer 14b. However, as described above, the portion facing the gap (becomes the portion) is provided as an insulating film. By removing the sacrificial layer using an etchant having sufficient selectivity between polysilicon and the silicon oxide film, for example, an aqueous solution of TMAH (Tetramethylammonium hydroxide (tetramethylammonium hydroxide)). Etching is not performed when the sacrificial layer is removed.

  Further, either one of the diaphragm electrode 22 and the fixed electrode 12 is an individual electrode separated for each nozzle (channel), and the other is a common electrode common to a plurality of nozzles (channels), for example, all nozzles (channels). Thus, it is possible to select a nozzle (channel) to be discharged. Here, the diaphragm electrode 22 is a common electrode, and the fixed electrode 12 is an individual electrode.

  In the electrostatic actuator of this embodiment, there are a first opening hole 55a and a second opening hole 55b arranged in series near the end of the communication path 56 away from the gap 14a. 55a is sealed with a first sealing material 58a made of the same material as the PBO film, which is a material for forming the diaphragm wetted film 26, and the second opening hole 55b is a second material made of an ultraviolet curable epoxy resin. It is sealed with a sealing material 58b.

(Embodiment 2)
A manufacturing method of the electrostatic actuator of the present invention will be described as a second embodiment. FIG. 9 is a flowchart of the manufacturing method of the electrostatic actuator according to the second embodiment. FIG. 10 is a sectional view showing a manufacturing process of the electrostatic actuator of the present invention. This will be described with reference to FIGS.

Step 1 (FIG. 9 (S1)): Formation of Main Part Using the sacrificial layer process as in the known electrostatic actuator manufacturing method, the fixed electrode 12 is formed on the actuator substrate 10, and the sacrificial layer is formed thereon. The diaphragm 20 (however, the diaphragm wetted film 26 is not laminated) is disposed, and the gap 14a and the communication path 56 are formed to form the main part of the electrostatic actuator. In this case, since the sacrificial layer removal hole is sealed with a silicon oxide film formed by a low pressure CVD method, the inside of the gap 14a is kept at a reduced pressure, and the diaphragm is pushed to the atmospheric pressure in an environment of normal temperature and normal pressure, and the gap 14a side. Is bent.

Step 2 (FIG. 9 (S2)): First opening opening (FIG. 10 (a))
The first opening hole 55a is opened. Thereby, the pressure in the gap 14a can be made the same as the external pressure, and the bending of the diaphragm 20 is eliminated. The first opening hole 55a was opened by photolithography / etching.

Step 3 (FIG. 9 (S3)): diaphragm wetted film formation / first open hole sealing (FIG. 10 (b))
A PBO diaphragm contacting liquid film 26 as a protective film was formed by a coating method. A PBO film can be easily formed only at a desired portion by performing a procedure in the order of (1) to (5) below using a precursor that becomes PBO as a photosensitive material.
(1) A solution containing a precursor to be PBO is applied to the surface of the actuator substrate 10 by spin coating.
(2) Perform soft baking to evaporate the solvent. At this time, for example, after first baking at about 60 ° C./3 min and then increasing the temperature stepwise by 120 ° C./4 min (both on a hot plate), it is generated in the vicinity of the first open hole 55a. It is easy to suppress foaming caused by solvent volatilization.
(3) The PBO unnecessary portion is exposed to the precursor film by mask exposure.
(4) The PBO precursor film portion exposed by immersion in an alkaline solution is removed.
(5) Hard baking is performed at a temperature of about 320 ° C., and the remaining precursor film portion is completely converted to PBO.

  At this time, the first open hole 55a is sealed with the PBO film simultaneously with the formation of the diaphragm wetted film 26. When the first sealing material 58a is formed by such a method, the first sealing material 58a is shown in FIG. 10B depending on the size of the first opening hole 55a and the state of the material in the vicinity of the opening hole. As shown, there are a case where it is formed only on the surface and does not enter the inside, and a case where the inside of the communication path 56 is entered although not shown. Although illustration is omitted, if the communication path 56 has a meandering shape, it is possible to suppress deep entry into the communication path 56.

  The PBO film has air permeability. In particular, as shown in the drawing, when the first sealing material 58a is formed only on the surface, the air permeability is large but the liquid does not permeate. Even if the surface of 10 is exposed to a liquid (for example, a resist solution, an etching solution, a stripping solution, or pure water), the liquid does not enter the communication path 56, the gap 14a, or the like.

Step 4 (FIG. 9 (S4)): Liquid supply path formation / Liquid supply path liquid film formation (FIG. 10 (c))
The electrostatic actuator according to this embodiment includes a liquid supply path 57 that penetrates the actuator substrate 10 and discharges discharge liquid from the actuator substrate 10 side. The liquid supply path 57 was formed by a photolithography / etching process.

  Using the resist in which the liquid supply path 57 is formed as a mask, the oxide film / nitride film laminated film on the surface of the actuator substrate 10 is etched with a normal dry etcher, and the actuator substrate 10 made of silicon is etched with a silicon deep dry etcher. Went. In addition, a method of forming by water laser, sandblasting, or the like may be used.

  The liquid supply path wetted film 61 can be formed into PBO by attaching a solution containing a PBO precursor to the inner wall of the liquid supply path 57 by spray coating from the back side of the actuator substrate 10 and then baking the solution.

Step 5 (FIG. 9 (S5)): Second opening opening (FIG. 10 (d))
The second opening hole 55b is opened at a predetermined position by a laser or the like.

Step 6 (FIG. 9 (S6)): Hydrophobization treatment A gas to be a hydrophobic film such as HMDS (hexamethyldisilazane) is introduced from the second open hole 55b to the gap 14a through the communication path 56, and the inner surface of the gap 14a. In particular, the hydrophobic treatment is performed on the portions of the diaphragm-side insulating film 22 and the fixed electrode-side insulating film 13 facing the gap 14a. At this time, as a pretreatment (drying) step, moisture adhering to the surface inside the void 14a and diaphragm wetted film formation / first open hole sealing step, the gap 14a enters and a part of It is desirable to remove or reduce as much as possible the solvent etc. that dissolved the PBO precursor adhering to the surface.

  Specific examples of the pretreatment step include a step of leaving the actuator substrate 10 in a treatment tank supplied with dry air and drying, a step of heating the inside of the treatment tank under vacuum, and heating the actuator substrate 10 in vacuum, an actuator A step of alternately switching the inside of the processing tank in which the substrate 10 is disposed to a vacuum atmosphere and a nitrogen atmosphere, and a combination of these steps can be employed.

  In the hydrophobic film forming step, the container containing the actuator substrate 10 and the liquid phase HMDS is placed in a treatment tank and left at room temperature and normal pressure until the HMDS vapor sufficiently penetrates into the gap 14a by diffusion. Alternatively, the actuator substrate 10 is immersed in a container containing liquid phase HMDS in a decompressed treatment tank to introduce the liquid phase HMDS into the gap 14a, and then the actuator substrate 10 is heated in another treatment tank. Then, the liquid phase HMDS may be removed by evaporation from the inside of the gap 14a. At this time, an appropriate HMDS vapor is introduced into the heat treatment tank so that a desired concentration of HMDS vapor remains in the gap 14a.

Step 7 (FIG. 9 (S7)): Second open hole sealing (FIG. 10 (e))
The actuator substrate 10 is taken out from the hydrophobic treatment tank, and the second open hole 55b is quickly hermetically sealed with the sealing material 58b. As the sealing material 58b, an ultraviolet curable epoxy resin was used as described above.

  If the actuator substrate 10 is manufactured by the above manufacturing process, the material (PBO precursor) that becomes the diaphragm wetted film 26 in a state where the diaphragm 20 is not bent in the diaphragm wetted film forming process of Step 3 above. ) Is applied, it is possible to form the diaphragm wetted film 26 having a uniform film thickness using a coating method.

  Further, since the hydrophobizing process is performed after the formation process of the diaphragm wetted film 26 and the liquid supply path wetted film 61, the hydrophobic film and its vapor component (here, HMDS) are hardened by the PBO that becomes the wetted film. They are not desorbed or decomposed by exposure to high temperatures during baking.

  Furthermore, since the sealing material 58b that seals the second open hole 55b can be selected only from the viewpoint of sealing, reliable airtight sealing is possible. At this time, if the second opening hole 55b is formed closer to the gap 14a on the communication path 56 than the first opening hole 55a, the second opening hole 55b can block the communication path 56, Even if the sealing performance of the first open hole 55a is incomplete, the influence of the sealing performance of the gap 14a can be eliminated.

(Embodiments 3 to 6)
Embodiments 3 to 6 of the electrostatic actuator of the present invention are electrostatic actuators including a plurality of electrostatic actuator elements, and include a communication path 56, a first opening hole 55a, and a second opening hole 55b. The arrangements are different from each other. In these electrostatic actuators, a plurality of electrostatic actuator elements 3 are arranged in parallel on the actuator substrate 10, and the ends of the gaps 14 a of the electrostatic actuator elements 3 are static. The electric actuator element 3 communicates with a communication path 56 disposed along the row of electric actuator elements 3 (also a row of gaps 14a).

  As shown in FIG. 2, the electrostatic actuator according to the third embodiment has a first opening hole 55 a from the end of the communication path 56 to the communication path 56 extending to the end on the actuator substrate 10. They are formed side by side in the order of the second opening holes 55b. This embodiment has already been described with reference to FIG.

  In the electrostatic actuator according to the fourth embodiment, as shown in FIG. 11, the electrostatic actuator elements 3 are aligned on the actuator substrate 10 and communicated with the gaps 14 a of the electrostatic actuator elements 3. As described above, the communication path 56 is formed along the row of the electrostatic actuator elements 3 at the end of the actuator substrate 10. A second atmosphere opening hole 55b is provided at both ends of the communication path 56 so that the hydrophobic material precursor gas can be introduced into the gap 14a of each electrostatic actuator element 3 in a shorter time. Here, the first air opening hole 55 a is provided at only one place at one end of the communication path 56. The first atmosphere opening hole 55a is for making the inside of the gap 14a of each electrostatic actuator element 3 equal to the external pressure, and it is sufficient if it is provided at one place of one communication path 56. Two or more locations may be provided at the ends of the communication passages 56 on both sides. At this time, it is preferable to form the second air opening hole 55 b closer to the gap 14 a on the communication path 56 than the first air opening hole 55 a.

  FIG. 12 shows the electrostatic actuator of the fourth embodiment. The difference from the electrostatic actuator of the third embodiment is that there are communication paths 56 at both ends of the gap 14a of each electrostatic actuator element 3. Both end portions of the gap 14 a communicate with the respective communication paths 56. And the 2nd air release hole 55b is arrange | positioned at the both ends of the two communicating paths 56, respectively. In this way, the hydrophobic precursor gas can be introduced into the gap 14a of each electrostatic actuator element 3 in a shorter time. As in the arrangement example of the third embodiment, the first atmosphere opening hole 55a is provided at only one place in the communication path 56, but it may be arranged at two or more places. At this time, as described above, it is preferable to form the second air opening hole 55b closer to the gap 14a than the first air opening hole 55a.

  FIG. 13 shows the electrostatic actuator of the fifth embodiment. The difference from the electrostatic actuator of the fourth embodiment is that the ends of the two communication paths 56 in the fourth embodiment communicate with each other. The second atmosphere opening hole 55 b and the first atmosphere opening hole 55 a are arranged on the communication path 56 so as to extend. In this embodiment, the number of second air opening holes 55b is reduced by using the air opening holes in common on both communication paths 56. In this embodiment, the introduction time of the hydrophobic agent can be shortened, and the second atmosphere opening hole 55b, which is a place that needs to be sealed, is reduced compared to the electrostatic actuator of the fourth embodiment. It is possible to reduce the time required for sealing. Here, the first air opening hole 55a is arranged only on one side, but may be arranged on both sides.

  Furthermore, as another arrangement form, each gap 14a is grouped into a predetermined number, and a sub-common communication path is branched into the communication path 56 for each gap group, and the second air opening hole 55b is formed in the sub-common communication path. It is also possible to introduce the hydrophobic agent precursor gas into each gap 14a uniformly and quickly.

(Embodiment 7)
Embodiment 7 is an image forming apparatus equipped with a droplet discharge head using the above-described electrostatic actuator according to the present invention as discharge pressure generation means for discharge liquid. FIG. 14 is a perspective view of the sixth embodiment, and FIG. 15 is an explanatory side view for explaining a mechanism portion of the image forming apparatus. An image forming apparatus according to the sixth embodiment will be described with reference to FIGS. Usually, this image forming apparatus is also called an ink jet recording apparatus or an ink jet printer. This inkjet recording apparatus supplies a recording liquid to the recording head 95, which includes a carriage 93 that can move in the main scanning direction inside the recording apparatus main body 81, a droplet discharge head of the present invention mounted on the carriage 93, and the recording head 95. A printing mechanism 82 composed of a liquid cartridge is stored. A paper feed cassette (or a paper feed tray) 84 on which a large number of sheets 83 can be stacked from the front side can be removably mounted on the lower part of the apparatus main body 81, and the sheets 83 can be manually inserted. The manual feed tray 85 for feeding paper can be turned over. The paper 83 fed from the paper feed cassette 84 or the manual feed tray 85 is taken in, and after a required image is recorded by the printing mechanism unit 82, the paper is discharged to a paper discharge tray 86 mounted on the rear side.

  In such an image forming apparatus, the performance and reliability of the recording head 95 are directly connected to the performance and reliability of the image forming apparatus. In this image forming apparatus, a low-power consumption, high image quality, high-power is achieved by using a low-power consumption, high-precision, high-reliability electrostatic actuator of the present invention as a low-pressure power generation means. A reliable image forming apparatus can be provided.

  As mentioned above, although this invention was demonstrated centering on embodiment, this invention is not limited to said embodiment. The present invention may be modified or modified based on the spirit of the present invention and the technical common knowledge of those skilled in the art.

  An electrostatic actuator according to the present invention includes a communication path communicating with a gap, a first opening hole and a second opening hole arranged in series near the end of the communication path. When the protective film is formed on the surface of the electrostatic actuator (vibration plate surface), the two open holes are sealed with different materials. Since it is easy and it is possible to ensure the optimal hydrophobic treatment in the gap and the airtightness of the gap, it is possible to obtain a highly accurate and highly reliable electrostatic actuator.

  In the electrostatic actuator of the present invention, the material for sealing the first open hole is made the same as the material formed on the surface of the diaphragm, so that the manufacturing process can be simplified and the static cost can be reduced. An electric actuator can be obtained.

  According to the manufacturing method of the electrostatic actuator of the present invention, the functional film such as the diaphragm protective film is formed on the diaphragm surface after opening the first opening hole, so that the diaphragm is not bent. Thus, a functional film such as a diaphragm protective film can be formed on the surface of the diaphragm. For this reason, it becomes possible to form a protective film uniformly by a coating method or the like. After that, the second open hole is opened, and the hydrophobic material precursor gas is introduced into the gap from there, and then the first Since the two open holes are sealed, it is possible to ensure an optimal hydrophobization treatment in the gap and to ensure airtightness of the gap, and to obtain a highly accurate and highly reliable electrostatic actuator.

  The droplet discharge head of the present invention uses the electrostatic actuator of the present invention as the droplet discharge pressure generating means, so that a highly accurate and highly reliable electrostatic droplet discharge head can be obtained.

  Since the image forming apparatus of the present invention uses the liquid droplet ejection head of the present invention in the image forming unit, an image forming apparatus with high image quality and high reliability can be obtained.

Sectional view of the electrostatic actuator of the present invention Schematic diagram of an electrostatic actuator with multiple electrostatic actuator elements FIG. 3 is an exploded perspective view of the droplet discharge head of the present invention. Partial plan perspective view of the droplet discharge head of the present invention XX 'sectional view in FIG. Y1-Y1 'sectional view in FIG. Y2-Y2 'sectional view in FIG. Y3-Y3 'sectional view in FIG. Manufacturing process flowchart of electrostatic actuator of the present invention Manufacturing process diagram of electrostatic actuator of the present invention Example of arrangement of open holes in electrostatic actuator of the present invention (2) Example of arrangement of open holes in electrostatic actuator of the present invention (3) Example of arrangement of open holes in electrostatic actuator of the present invention (4) The perspective view of the image forming apparatus of this invention Side view of the image forming apparatus of the present invention

Explanation of symbols

1: Droplet discharge head 2: Electrostatic actuator 3: Electrostatic actuator element 10: Substrate (actuator substrate)
11: Substrate insulating film 12: Fixed electrode 12b: Fixed electrode (leading portion)
12c: Fixed electrode dummy (spacer)
13: Fixed electrode side insulating film 14a: Air gap
14b: Residual sacrificial layer (spacer)
20: Diaphragm (laminated diaphragm)
21: Diaphragm-side insulating film 22: Diaphragm electrode 22b: Diaphragm electrode (leading portion)
22c: Diaphragm electrode dummy (spacer)
24: tensile stress film 25: sacrificial layer removal hole sealing film 26: diaphragm wetted film (protective film)
30: Liquid chamber substrate 31: Common liquid chamber 32: Fluid resistance portion 33: Pressurized liquid chamber 34: Communication pipe 35: Flow path substrate wetted film 40: Nozzle plate 41: Nozzle hole 52: Electrode-wiring connection hole 53a: Fixed electrode wiring 53b: Diaphragm electrode wiring 54: Electrical connection 55a to the outside: First air opening hole 55b: Second air opening hole (HMDS introduction hole)
56: Communication path 57: Liquid supply path 58a: First sealing member 58b: Second sealing member (sealing material)
60: Adhesive material layer 61: Discharge liquid flow hole 61: Discharge liquid supply path wetted film 81: Image forming apparatus (apparatus body)
82: Printing mechanism 83: Paper 84: Paper feed cassette 85: Manual feed tray 86: Paper discharge tray 93: Carriage 95: Recording head

Claims (9)

A diaphragm including a diaphragm electrode and having a protective film formed on a surface thereof; a fixed electrode disposed opposite to the diaphragm via a gap ;
A communication path communicating with the gap ,
The diaphragm including the protective film is formed with a first opening hole and a second opening hole that open the communication path to the atmosphere.
The second opening hole is formed so as to penetrate to the protective film, and is formed closer to the gap than the first opening hole ,
The sealing material for hermetically sealing the second opening hole blocks a communication portion with the second opening hole of the communication path,
The protective film is a resin film obtained by heat-curing a thermosetting protective film precursor,
The electrostatic actuator , wherein the gap includes a hydrophobic film that is desorbed or decomposed at a curing temperature of the protective film . An electrostatic actuator comprising a plurality of electrostatic actuators according to claim 1, wherein communication paths of the electrostatic actuators communicate with each other . The electrostatic actuator according to claim 1, wherein the first opening hole is sealed with the protective film. The encapsulant electrostatic actuator according to claim 1, characterized in that an epoxy resin.   A droplet discharge head comprising the electrostatic actuator according to claim 1, wherein the droplet is discharged from a nozzle by operating the electrostatic actuator.   An image forming apparatus comprising the droplet discharge head according to claim 5, wherein the droplet discharge head ejects droplets onto a recording material to form an image. After laminating a fixed electrode, a sacrificial layer, and a diaphragm including a diaphragm electrode on the substrate in order, an etching agent is introduced into the sacrificial layer to remove the sacrificial layer and communicate with the gap and the gap Forming an electrostatic actuator structure for forming
A first opening hole forming step in which the diaphragm is provided with a first opening hole that allows the communication path to communicate with the atmosphere;
Applying a thermosetting protective film precursor to the surface of the diaphragm , heat-curing a protective film forming step of forming a protective film,
A second opening hole forming step of providing a second opening hole for communicating the communication path with the atmosphere on the surface of the diaphragm on which the protective film is formed ;
From the second open hole, the hydrophobic agent introducing step for introducing a hydrophobic agent into said gap through said communication passage,
A second opening hole sealing step of sealing the second opening hole with a sealing material;
A method for manufacturing an electrostatic actuator, comprising: The method for manufacturing an electrostatic actuator according to claim 7, wherein the protective film forming step includes a liquid supply path forming step for forming a liquid supply path through which the discharged fluid flows. 9. The method of manufacturing an electrostatic actuator according to claim 7 , wherein the protective film forming step includes a first open hole sealing step for sealing the first open hole .

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