JP4557667B2 - Electrostatic actuator, method for manufacturing electrostatic actuator, droplet discharge head, liquid cartridge, image forming apparatus, micropump, and optical device - Google Patents

Description

  The present invention relates to an electrostatic actuator, a manufacturing method of an electrostatic actuator, a droplet discharge head, a liquid cartridge, an image forming apparatus, a micropump, and an optical device.

  For example, a droplet discharge head used in an ink jet recording apparatus used as an image forming apparatus such as a printer, a facsimile, a copying apparatus, or a plotter includes a nozzle that discharges a droplet and a liquid chamber (discharge chamber, pressure chamber) that communicates with the nozzle. Pressure chambers and ink flow paths) and actuator means for generating energy for pressurizing the ink in the liquid chamber, and generating pressure to the recording liquid in the liquid chamber by generating energy. To discharge droplets from the nozzle.

  Droplet discharge heads that use piezoelectric actuators such as electromechanical transducers, those that use thermal actuators that use film boiling as electrothermal transducers, and electrostatic forces between the diaphragm and electrodes Some of them use electrostatic actuators. Among them, droplet discharge heads using electrostatic actuators are superior to other types of heads in terms of miniaturization, high speed, high density, and power saving. As a result, development is actively underway.

  In such 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 characteristics. In this case, if the variation in the 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 voltage, the gap interval must be about 0.1 to 0.5 μm, and higher dimensional accuracy is required.

By the way, as described in Patent Document 1, a conventional ink jet head is formed with a substrate (cavity plate) on which a pressurized liquid chamber and a vibration plate are formed, and a recess and a segment electrode that form a gap (vibration chamber). It is formed by bonding to the substrate (glass substrate).
Japanese Patent Laid-Open No. 11-263012

  However, in such a head that joins two substrates to form a gap between the diaphragm and the electrode, due to dimensional variations during processing in many processes such as recess formation, electrode formation, and bonding. As a result, it is difficult to obtain an actuator having high accuracy and high reliability.

Therefore, as described in Patent Document 2, sacrificial layer etching is performed on the first substrate to form an individual electrode and a diaphragm facing the individual electrode via a gap formed by sacrificial layer etching, It is known that a gap portion for a pressure chamber is formed by forming a groove for a pressure chamber on a second substrate and bonding the second substrate on the first substrate to constitute an ink jet head. It has been.
JP 2001-18383 A

  By the way, in an electrostatic actuator, in order to eliminate the differential pressure between the internal pressure of the air gap and the atmospheric pressure, or to improve the reliability of the actuator, a communication path that communicates each air gap may be provided to introduce gas into the air gap. Has been done.

  For example, as disclosed in Patent Document 1, in order to form a hydrophobic film inside a vibration chamber (gap) between a diaphragm and an electrode, a communication path communicating with the outside of the actuator is communicated with each vibration chamber. Then, after introducing the gas which becomes a hydrophobic film into the vibration chamber through the communication path, the communication path is sealed with a sealing material.

In this case, in order to efficiently introduce the gas forming the hydrophobic film into the vibration chamber, it is necessary to increase the cross-sectional area of the communication path. It is known to form a communication path having a large cross-sectional area by digging an electrode substrate on which an electrode is formed.
JP 2003-72070 A

  In the electrostatic actuator in which a gap is formed by sacrificial layer etching described in Patent Document 2 described above, the gap between the diaphragm and the electrode can be determined by the height of the sacrificial layer. Although a high gap can be obtained, on the other hand, when trying to form a communication path as described in Patent Documents 1 and 2, the height of the communication path is limited by the height of the sacrificial layer for forming the gap. Therefore, there is a problem that it is difficult to form a communication path having a large cross-sectional area.

  As described above, in the conventional electrostatic actuator and the liquid droplet ejection head using the same, the dimensional variation of the air gap is suppressed, and a communication path having a large cross-sectional area cannot be formed, and the reliability is high. There was a problem that it was not enough.

  The present invention has been made in view of the above problems, and an electrostatic actuator that can obtain high reliability, a droplet discharge head including the electrostatic actuator, and a liquid cartridge in which the droplet discharge head is integrated. An object of the present invention is to provide an image forming apparatus equipped with the droplet discharge head or the liquid cartridge, and a micropump and an optical device using the electrostatic actuator.

In order to solve the above problems, an electrostatic actuator according to the present invention is:
In an electrostatic actuator comprising a deformable diaphragm and an electrode facing the diaphragm through a gap formed by sacrificial layer etching, and deforming the diaphragm with an electrostatic force,
The plurality of gaps communicate with each other through a common communication path,
The common communication path is formed by removing a sacrificial layer that forms the gap, and a first portion that is formed by removing the electrode forming layer that communicates with the first portion and forms the electrode. Two parts,
The length of the short side cross section of the second portion is longer than the length of the short side cross section of the first portion of the common communication path .

Here, the common communication path may be configured to communicate with the outside or the buffer chamber. The common communication path may be branched.

  The manufacturing method of the electrostatic actuator according to the present invention is a method of manufacturing the electrostatic actuator according to the present invention, wherein the common communication path is formed at the same time when the gap is formed by sacrificial layer etching. It is.

  The droplet discharge head according to the present invention includes the electrostatic actuator according to the present invention.

  The liquid cartridge according to the present invention is obtained by integrating the liquid droplet ejection head according to the present invention and a liquid tank that supplies liquid to the liquid droplet ejection head.

  An image forming apparatus according to the present invention is equipped with a liquid droplet ejection head according to the present invention for ejecting liquid droplets or a liquid cartridge according to the present invention.

  The micropump according to the present invention includes the electrostatic actuator according to the present invention for transporting a liquid.

  The optical device according to the present invention includes the electrostatic actuator according to the present invention that changes the reflection direction of light.

According to the electrostatic actuator according to the present invention, the plurality of gaps communicate with each other through the common communication path, and the common communication path includes the first portion formed by removing the sacrificial layer that forms the gap, And a second portion formed by removing an electrode forming layer that forms an electrode, and having a shorter side of the second portion than the length of the short-side cross section of the first portion of the common communication path Since the length of the side cross section is long , a communication path having a large cross sectional area can be obtained, and the reliability is improved.

  According to the method for manufacturing an electrostatic actuator according to the present invention, the gap and the common communication path are simultaneously formed by sacrificial layer etching, which shortens the manufacturing process and reduces manufacturing defects and costs. Can be planned.

  According to the droplet discharge head according to the present invention, since the electrostatic actuator according to the present invention is provided, variation in droplet discharge characteristics is reduced, and reliability can be improved.

  According to the liquid cartridge according to the present invention, since the liquid droplet ejection head according to the present invention and the liquid tank that supplies the liquid to the liquid droplet ejection head are integrated, there is little variation in the liquid droplet ejection characteristics and the liquid is highly reliable. A liquid cartridge (liquid tank integrated head) integrated with a droplet discharge head can be obtained at low cost.

  The image forming apparatus according to the present invention includes the droplet discharge head or the liquid cartridge according to the present invention, so that a high-quality image can be formed.

  According to the micropump according to the present invention, since the electrostatic actuator according to the present invention is provided, a small-sized and low power consumption micropump can be obtained.

  According to the optical device according to the present invention, since the electrostatic actuator according to the present invention is provided, a small-sized and low power consumption optical device can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a perspective explanatory view of an ink jet head as a droplet discharge head according to the present invention including an electrostatic actuator according to a first embodiment of the present invention, FIG. 2 is an exploded perspective explanatory view of the head, and FIG. FIG. 4 is a cross-sectional explanatory view in the liquid chamber long side direction along the surface S1 of FIG. 1, and FIG. 4 is a cross-sectional explanatory view in the liquid chamber long side direction along the surface S2 in FIG.

  This ink-jet head is of a side shooter type that discharges liquid droplets from nozzle holes provided in the surface portion of the substrate, and includes an actuator substrate 1 that is a first substrate, a flow path substrate 2 that is a second substrate, and a third substrate. A liquid chamber in which a nozzle 4 for ejecting liquid droplets communicates via a nozzle communication path 5 is formed by sequentially laminating a nozzle substrate 3 which is a substrate of the above-described substrate and joining the three substrates 1, 2 and 3 together. (Discharge chamber) 6, a fluid resistance portion 7 for supplying liquid (ink) to the liquid chamber 6 and a common liquid chamber 8 are formed. Each liquid chamber 6 is partitioned by a liquid chamber interval wall 9.

  The actuator substrate 1 includes a diaphragm 12 that forms a diaphragm region (deformable region) 12A that forms a part of the wall surface of the liquid chamber 6, and a gap formed by sacrificial layer etching in the diaphragm region 12A of the diaphragm 12. (Electrostatic actuator) according to the present invention corresponding to each liquid chamber 6 is configured by the diaphragm 12 and the individual electrode 14.

  Further, the actuator substrate 1 is formed with a common communication path (communication pipe) 15 in the direction in which the nozzles 4 are arranged so that the gaps 13 communicate with each other and communicate with the outside of the actuator substrate 1 itself. The air gap 13 is communicated with the passage 15 via the individual communication passage 15 </ b> A, and a gas introduction hole 16 that opens to the outside of the actuator substrate 1 is formed at the other end of the common communication passage 15.

  Although details of the actuator substrate 1 will be described later, an etchable electrode forming layer 24 to be the individual electrode 14 is formed on the silicon substrate 21 via the insulating film 22, and an insulating film 25 is formed on the electrode forming layer 24. Then, an opening 26 for forming the common communication path 15 is formed in the insulating film 25, and a sacrificial layer 27 for forming the gap 13 is formed on the insulating film 26, and the sacrificial layer 27 is formed on the sacrificial layer 27. An insulating film 28 is formed, a sacrificial layer removal hole 29 is formed in the insulating film 28, the sacrificial layer 27 is removed from the sacrificial layer removal hole 29 to form the gap 13 and the individual communication path 15A, and the insulating film The electrode forming layer 24 is also removed through the openings 26 to form the common communication path 15, and then the diaphragm member 30 is laminated on the insulating film 28.

  The insulating film 22 formed on the surface of the individual electrode 14 is for preventing an electrical short circuit with the diaphragm 12 and protecting the individual electrode 14 during etching of the sacrificial layer for forming the gap 13. In addition, the insulating film 28 on the vibration plate 12 side also prevents an electrical short circuit with the individual electrode 14 and is a part of the vibration plate member 30 formed on the insulating film 28 during etching of the sacrificial layer for forming the gap 13. It is for protecting the layer of the part.

  Thereby, the height of the common communication path 15 is the sum of the height of the sacrificial layer 27 for forming the air gap 13 and the height of the electrode forming layer 24 and the insulating film 25 which are lower layers thereof. It becomes higher than the height of 27 (height of the gap 13). In this case, the height of the common communication path 15 is formed to be higher than twice the height of the gap 13 by making the thickness of the electrode forming layer 24 and the insulating film 25 which are lower layers larger than the height of the sacrificial layer 27. .

  Further, a supply port 18 for supplying ink from the outside to the common liquid chamber 8 of the flow path substrate 2 is formed in the actuator substrate 1.

  The flow path substrate 2 bonded on the actuator substrate 1 communicates with, for example, a silicon substrate having a crystal plane orientation (110), a liquid chamber (discharge chamber) 6, and each liquid chamber 6 via a fluid resistance portion 7. The common liquid chamber 10 is provided (actually a groove or a recess).

  The nozzle substrate 3 bonded on the flow path substrate 2 uses, for example, nickel having a thickness of 50 μm, and the nozzle 4 can be formed by a known method such as dry or wet etching or laser processing.

  In the droplet discharge head configured as described above, the nozzles that are desired to discharge the recording liquid based on the image data from the control unit (not shown) in a state where each liquid chamber 6 is filled with the recording liquid (ink). A pulse voltage of 40 V is applied to the individual electrode 14 corresponding to 4 by the oscillation circuit. By applying this voltage, a positive charge is charged on the surface of the individual electrode 14, and a suction action by an electrostatic force acts between the individual electrode 14 and the diaphragm 12 including the diaphragm electrode, so that the diaphragm 12 moves downward. Flex. As a result, the volume of the liquid chamber 6 is expanded, so that the recording liquid corresponding to the volume flows from the common liquid chamber 10 into the liquid chamber 6 via the fluid resistance portion 7.

  Thereafter, by setting the pulse voltage to the individual electrode 14 to 0 V (stopping application), the diaphragm 12 bent downward by the electrostatic force returns to the original position due to its own rigidity. As a result, the pressure in the liquid chamber 6 is rapidly increased, and a recording liquid droplet is ejected from the nozzle hole 4 communicating with the liquid chamber 6. Then, by repeating this operation and continuously ejecting the recording liquid from the nozzle 4, an image is formed on a recording medium (paper) disposed facing the droplet ejection head.

  Here, in the electrostatic actuator, the electrostatic force acting between the individual electrode 14 and the diaphragm 12 is given by the following equation (1). Here, F: electrostatic force acting between the electrodes, ε: dielectric constant, S: area of the opposing surface of the electrodes, d: distance between the electrodes, V: applied voltage.

  That is, it can be seen that the electrostatic force F is inversely proportional to the square of the inter-electrode distance d and directly proportional to the square of the applied voltage V. That is, in order to reduce the drive voltage of the electrostatic actuator or the droplet discharge head equipped with the electrostatic actuator, the distance (gap height: gap length) between the individual electrode 14 and the diaphragm 12 is reduced. It is important to form.

  Therefore, as described above, by forming the air gap 13 by sacrificial layer etching, it is possible to stably form a fine air gap accurately and without variation, so that static characteristics with little variation in operating characteristics between the actuators can be obtained. Electrostatic actuators can be obtained, and by applying this electrostatic actuator to a droplet discharge head, variations in droplet discharge characteristics between nozzles can be reduced and high quality images can be formed. become able to.

  Here, when the gap 13 is formed by the sacrificial layer etching as described above, the height of the gap 13 is limited when the common communication path for communicating the gaps 13 is formed by the sacrificial layer etching.

  Therefore, in the electrostatic actuator of the droplet discharge head according to the present embodiment, the electrode forming layer 24 that forms the individual lower layer 14 constituting the lower layer part below the layer to be removed by sacrificial layer etching is also sacrificial layer etched. A sacrificial layer for forming the electrode forming layer 24 and the gap 13 is formed by forming the opening 26 in the insulating film 25 that protects the surface of the individual electrode 14 by forming it with a material that can be removed (the same material as the sacrificial layer). Since they are integrated and removed simultaneously by sacrificial layer etching to form the common communication path 15, the height of the common communication path 15 is formed higher than the height of the gap 13 as a whole, and thereby the cross-sectional area is large. A communication path can be obtained, and a highly reliable actuator and droplet discharge head can be obtained.

  In addition, the lower layer of the sacrificial layer forming the void is composed of a lower layer film made of the same material as the sacrificial layer, and an intermediate film interposed between the lower layer film and the sacrificial layer, and an opening is provided in the intermediate film. By forming the wall surface of the communication path, the sacrificial layer and the lower layer film can be simultaneously removed by etching, and a common communication path having a height higher than the gap can be easily formed. Moreover, by forming a part of the common communication path in the lower layer part, the height of the common communication path can be easily made higher than the height of the gap, and the film thickness (layer thickness) of the lower layer part can be selected. By doing so, it is possible to easily form a common communication path having a height exceeding twice the height of the gap. Further, by forming the common communication path having a height exceeding twice the height of the gap, the fluid resistance of the common communication path can be greatly reduced.

  Next, details of the actuator substrate 1 will be described with reference to FIGS. 5 is an explanatory plan view showing the substrate in a transparent state, FIG. 6 is an explanatory sectional view taken along line AA in FIG. 5, FIG. 7 is an explanatory sectional view taken along line BB in FIG. These are expansion explanatory drawings around a communicating path.

  As described above, the diaphragm 12 of the actuator substrate 1 is composed of the insulating film 28 and the diaphragm member 30. The diaphragm member 30 is formed on the insulating film 28 with a diaphragm electrode (upper electrode) 32 and a deflection preventing film. A (nitride film) 33, a film stiffness adjusting film 34, and a resin film 35 are sequentially laminated.

  As shown in FIG. 5, the diaphragm 12 includes deformable diaphragm regions 12 </ b> A separated by partition walls 31 formed corresponding to the partition walls 9 between the liquid chambers 6. Here, the short side length a and the long side length b of one diaphragm region 12A are, for example, a short side length a of 60 μm and a long side length b of 1000 μm.

  On the other hand, as described above, on the insulating film 22 formed on the surface of the silicon substrate 21, individual electrodes 14 that are individually separated so as to face each diaphragm region 12 </ b> A are formed. An insulating film 25 is formed.

  The gaps 13 between these diaphragm regions 12A and the individual electrodes 14 are formed by sacrificial layer etching. The sacrificial layer etching is performed by forming a sacrificial layer 27 having the height of the gap 13 on the insulating film 25 and then sequentially laminating an insulating film 28, a diaphragm electrode 32, and a deflection preventing film (nitride film) 33. A sacrificial layer removal hole 29 penetrating them is formed, and the sacrificial layer 27 in the space 13 is removed through the sacrificial layer removal hole 29.

  As shown in FIG. 5, the sacrificial layer removal holes 29 are equally spaced in the long side direction of the diaphragm region 12 </ b> A at intervals equal to or shorter than the short side length a of the diaphragm region 12 </ b> A and the same side of the opposite side. Formed in position. Since the sacrificial layer etching is isotropic, the sacrificial layer removal efficiency is higher when the sacrificial layer removal hole 29 is arranged in the center of the diaphragm region 12A, but the sacrificial layer removal hole 29 is present in the diaphragm region 12A. Therefore, the sacrificial layer removal hole 29 is preferably arranged outside the diaphragm region 12A. Further, by arranging a plurality of sacrificial layer removal holes 29, the sacrificial layer 27 can be efficiently removed, and the gap 13 can be formed efficiently.

  After the sacrificial layer etching, the sacrificial layer removal hole 29 is completely sealed with the film stiffness adjusting film 34. Thereafter, although not shown, a wiring layer and a supply port 18 for supplying the recording liquid to the common liquid chamber 8 are formed for taking out to the external electrode, and a liquid contact film is formed on the entire surface of the actuator substrate 1 by vapor deposition polymerization or the like. The resin film 35 is formed.

  Further, in order to ensure the reliability of the actuator, a hydrophobic film forming material, such as hexamethyldisilazane (HMDS), is formed in the gap 13 from the outside through the common communication path 15 and the gas introduction hole 16 formed here. Is introduced.

  Thus, as shown in FIG. 8, the height H1 of the common communication path 15 becomes (the thickness of the electrode forming layer 24 + the thickness of the insulating film 25 + the thickness of the sacrificial layer 27). It becomes higher than the height H2 of the gap 13 which is the same as the height H2 (H1> H2). On the other hand, as shown in FIG. 9, when the common communication path 15 'is formed by etching only the sacrificial layer 27 for forming the gap 13, the height H1' of the common communication path 15 is the gap It becomes the same as the height H2 (H1 ′ = H2).

  In other words, the height of the common communication path 15 is higher than that in the case where the common communication path 15 ′ is formed only by the sacrificial layer for forming the gap, so that the cross-sectional area is increased and a large conductance can be ensured. it can.

  Thereby, for example, when the hydrophobic film forming material is introduced from the outside into the gap via the common communication path, the gas of the hydrophobic film forming material can be easily introduced. Further, by sealing the sacrificial layer removal hole with the common communication path opened to the outside, it is possible to eliminate the bending of the diaphragm due to the differential pressure between the atmospheric pressure and the internal pressure of the air gap. Furthermore, by connecting the common communication path to a buffer chamber having a sufficient volume, it is possible to eliminate the differential pressure between the outside and the inside of the air gap due to changes in environmental temperature and atmospheric pressure with high responsiveness.

Next, the manufacturing process of the actuator substrate 1 to which the manufacturing method according to the present invention is applied will be described with reference to FIGS. 10 to 12 are cross-sectional explanatory views corresponding to the cross section along the line AA in FIG. 5, and FIGS. 13 to 15 are cross-sectional explanatory views corresponding to the cross section along the line BB in FIG.
First, as shown in FIGS. 10A and 13A, for example, an insulating film (thermal oxide film) having a thickness of 1.6 μm is formed on the surface (here, both surfaces) of a silicon (Si) substrate 21 having a thickness of 400 μm. 22 is formed, and P-doped polysilicon is formed to a thickness of 0.6 μm on the insulating film 22 as an electrode forming layer 24 for forming the individual electrode 14.

  Then, as shown in each figure (b), the polysilicon (electrode forming layer) 24 is formed by forming a separation groove 40 by a litho-etching method, so that the individual electrode 14, the portion 41 constituting the partition wall, and the common communication path 15 are formed. In addition to the separation and patterning, the portion 42 corresponding to the portion 43 that penetrates the silicon substrate 21 and forms the supply port 18 is removed.

  Then, as shown in each figure (c), a CVD oxide film is deposited to a thickness of 0.2 μm, the individual electrode 14 formed of polysilicon 24a, the part 41 constituting the partition, and the part that becomes the communication path An insulating film 25 is formed on 42. At this time, the insulating film 25 is also formed in the separation groove 40 that separates the individual electrode 14, the portion 41 constituting the partition wall, and the portion 42 serving as a common communication path. Thereafter, the insulating film 25 on the portion 42 that becomes the common communication path is removed by a lithoetch method to form the opening 26, and the portion 42 that becomes the common communication path is exposed.

  Next, as shown in FIGS. 11A and 14A, a non-doped polysilicon film is formed as a sacrificial layer 27 on the insulating layer (film) 25 to a thickness of 0.2 μm, which is a gap interval, by a CVD method. To do. Then, the polysilicon is separated and patterned into a portion 45 that becomes the gap 13, a portion 46 that forms the partition wall, a portion 47 that becomes the individual communication passage 15 </ b> A, and a portion 48 that becomes the common communication passage 15 by the litho-etching method and supplies the polysilicon. A portion corresponding to the portion 43 to be the mouth 18 is removed.

  At this time, a portion 48 for forming the common communication passage 15 formed of the sacrificial layer 27 made of polysilicon and a portion 42 for forming the common communication passage 15 formed of the electrode forming layer 24 made of polysilicon constituting the lower layer portion. Since the opening 26 is formed in the insulating film 25 that is an intermediate film, the polysilicon that forms the sacrificial layer 27 is directly formed on the polysilicon that forms the electrode forming layer 24 that is the lower layer film, that is, The sacrificial layer and the electrode forming layer are in contact with each other and are integrated.

  In this way, by using polysilicon as the material for forming the sacrificial layer, a general-purpose technique generally known as a sacrificial layer removal step can be used, and there is selectivity with other materials and freedom of the process. A stable actuator with high degree, low cost, excellent mass productivity can be obtained.

  Thereafter, a sacrificial layer 27 is formed, and a CVD oxide film is deposited on the portion 45 serving as a gap, the portion 46 constituting the partition, the portions 47 and 48 serving as the individual communication passage 15A and the common communication passage 15, and insulated. The film 28 is formed with a thickness of 0.1 μm.

  Next, as shown in each figure (b), a P-doped polysilicon layer to be a diaphragm electrode layer 32 is formed on the insulating film 28 with a thickness of 0.1 μm, and this polysilicon layer is formed by a lithoetch method. While separating into the diaphragm electrode layer 32 and the part 49 which comprises a partition, the part 43 used as the supply port 18 is removed, and opening is formed.

  At the same time, in order to prevent the diaphragm electrode layer 32 made of the same material as the sacrificial layer 27 from being etched during the sacrificial layer etching, an opening 50 having an opening diameter larger than the sacrificial layer removal hole 29 to be formed later is formed. . Then, a nitride film 33a having a thickness of 0.15 μm is deposited on the diaphragm electrode layer 32 as an anti-bending layer 33 of the diaphragm 12 by the LP-CVD method. The deflection preventing layer 33 made of this nitride film is also formed in the opening 50 to cover the end face side of the opening 50 of the diaphragm electrode layer 32.

  After that, as shown in each figure (c), a sacrificial layer removal hole 29 having an opening diameter of 2 μm is formed through the nitride film 33a and the insulating film 28 as the deflection preventing layer 33 by a litho-etching method, and the portion that becomes the supply port 18 The processed hole 51 of the supply port 18 is formed by removing the nitride film 33a, the insulating film 28, and the insulating film 25.

Then, for example, sacrificial layer etching such as SF ₆ plasma treatment or dry etching with XeF ₂ gas is performed to form the sacrificial layer 27 in the portion 45 that becomes the gap 13, the sacrificial layer 27 in the segment 47 that becomes the individual communication path 15A, By completely removing the sacrificial layer 27 of the portion 48 that becomes the passage 15 and the electrode forming layer 24 of the portion 42 that becomes the common communication passage 15, the air gap 13, the individual communication passage 15 </ b> A, and the common communication passage 15 are formed. Here, the sacrificial layer etching is performed by dry etching, but wet etching of a TMAH solution or a KOH solution may be used.

  In this way, the lower layer portion of the sacrificial layer 27 is formed by the etching-removable electrode forming layer 24 that forms the individual electrode 14 and the insulating film 25 that is an intermediate layer for protecting the individual electrode 14, and is formed in the common communication path. In the corresponding portion, the insulating film 25 is removed and the opening 26 is formed to expose the lower electrode forming layer 24 and to be in a state of being continuous with the sacrificial layer 27 for forming the gap 13. Etching is performed to simultaneously remove the sacrificial layer 27 for forming the air gap 13 and the portion of the electrode forming layer 24 corresponding to the common communication path 15, which is a lower layer film located below the sacrificial layer 27. The height of the common communication path 15 thus made is higher than the height of the gap 13 by the height of the lower layer (the total thickness of the insulating film 25 and the electrode forming layer 24), and is common only to the sacrificial layer 24. A communication passage 15 is formed Than, be able form a large common connection path 15 of the cross-sectional area, it is possible to sufficiently ensure the conductance of the common connection path 15.

  In this way, the lower layer portion is composed of a lower layer film made of the same material as the sacrificial layer and an intermediate film interposed between the lower layer film and the sacrificial layer, and an opening for forming a communication path is formed in the intermediate film. As a result, the gap and the communication path can be formed simultaneously in one step of sacrificial layer etching to form the gap, so that a highly reliable actuator with little dimensional variation can be obtained and the manufacturing process can be shortened. be able to.

  In addition, since a communication path that can obtain a sufficient conductance different in height from the gap can be formed in the same process as the gap, mass production and cost reduction can be achieved.

  Next, as shown in FIGS. 12A and 15A, a rigidity adjusting film 34 is formed by atmospheric pressure CVD for the purpose of sealing the sacrificial layer removal hole 29 and adjusting the rigidity of the diaphragm 12. To do. The film thickness at this time is a film thickness that can seal the sacrificial layer removal hole 29, for example, a thickness of 0.6 μm. By performing this step, the gap 13 is sealed and completely blocked from the outside air.

  Thereafter, as shown in each figure (b), after removing the rigidity adjusting film 34 and the insulating films 22 and 28 in the portion serving as the supply port 18 by a lithoetch method, the silicon substrate is subjected to anisotropic etching, for example, an ICP etcher. The supply port 18 is formed by etching so as to penetrate 21 from the front surface to the back surface. Here, by forming the supply port 18 by anisotropic etching, it is possible to obtain a high effect in terms of processing shape controllability, fine workability and processing accuracy, and high density.

  Next, as shown in each figure (c), a resin film 35 as a liquid contact film is formed to a thickness of 1 μm on the entire surface of the actuator substrate 1 by a vapor deposition polymerization method with excellent coverage. Thereafter, only the electrode wiring take-out pad portion (not shown) is opened by the lithoetch method. Here, examples of the material used as the resin film 35 include a PBO film (polybenzoxazole), a polyimide film, and polyparaxylylene. However, the material has corrosion resistance against droplets and can be formed by vapor deposition polymerization. Other materials may be used.

  Thereafter, although not shown, for example, after introducing HMDS as a material for forming a hydrophobic film into the gap 13 from the gas introduction hole 16 through the common communication path 15 and the individual communication path 15A, the gas introduction hole 16 is introduced. Is sealed using, for example, an epoxy adhesive or the like. In this case, the sealing agent does not enter the gap 13 and stops inside the common communication path 15.

  Thus, by sealing the common communication path 15 with the sealant, the gas introduced into the gap 13 is prevented from diffusing to the outside, and foreign matter, moisture, and the like from the outside are prevented from being mixed. Therefore, a highly reliable actuator can be obtained.

Through the above steps, the actuator substrate 1 on which the electrostatic actuator according to the present invention is formed is completed.
Then, by sequentially stacking the actuator substrate 1, the above-described flow path substrate 2, and the nozzle substrate 3, the droplet discharge head according to the present invention including the electrostatic actuator according to the present invention can be manufactured. .

  Next, a second embodiment of the electrostatic actuator according to the present invention will be described with reference to FIGS. 16 is an explanatory plan view of the actuator substrate of the electrostatic actuator, FIG. 17 is an explanatory sectional view taken along the line CC in FIG. 16, and FIG. 18 is an explanatory sectional view taken along the line DD in FIG. is there.

  In this embodiment, the common communication path 15 includes a lower portion 15 a formed by sacrificial layer etching of the electrode formation layer 24 and an upper portion 15 b formed by sacrificial layer etching of the insulating film 25 and the sacrificial layer 27. The widths in the direction orthogonal to the direction in which the liquid crystal is arranged (the width in the direction along the liquid chamber long side direction, which is referred to as “length”) are made different. That is, as shown in FIGS. 16 and 18, the sacrifice of the electrode formation layer 24 is performed so that the relationship between the upper side length c and the lower side length d in the short side cross section of the common communication path 15 is upper side length c <lower side length d. The length of the lower portion 15a formed by layer etching is increased.

Thus, by forming the relationship between the upper side length c and the lower side length d in the short side cross section of the common communication path 15 such that the upper side length c <the lower side length d, the cross sectional area of the common communication path 15 is set to the first side. It can be made larger than in the case of the embodiment , and more sufficient conductance can be ensured.

  Note that the cross-sectional area of the common communication path 15 can be further increased by increasing the length of the upper side length c in the short side cross section of the common communication path 15, but if the upper side length c is increased too much, vibration will occur. The strength of the plate 12 cannot be sufficiently ensured, and the vibration plate 12 on the common communication path 15 may break when a structure, for example, the flow path substrate 2 is joined to the actuator substrate 1.

  Therefore, here, the upper side length c of the common communication path 15 is not increased, but the lower side length d is increased, so that the strength of the diaphragm 12 on the common communication path 15 is maintained and the common communication path 15 is disconnected. The area is increased to ensure sufficient conductance.

  The remaining configuration of the second embodiment is the same as that of the first embodiment. Further, in the manufacturing process, when the polysilicon which is the electrode forming layer 24 is patterned in the process of FIG. 10B and FIG. The other steps are the same except that the width (width) is formed to a length (width) corresponding to the lower side length d.

Next, different examples of the arrangement of the gas introduction hole and the common communication path in each of the above embodiments will be described with reference to FIGS.
FIG. 19 shows an example in which one end side of each gap 13 is communicated with one common communication path 15 via an individual communication path 15 </ b> A, and a gas introduction hole 16 is formed at one end of the common communication path 15. FIG. 20 shows an example in which one end side of each gap 13 is communicated with one common communication path 15 via an individual communication path 15 </ b> A, and gas introduction holes 16 are formed at both side ends of the common communication path 15.

  In FIG. 21, both end portions of each gap 13 are communicated with the common communication passages 15 and 15 via the individual communication passages 15A and 15A, respectively, and gas introduction holes 16 and 16 are formed at both ends of each common communication passage 15 and 15, respectively. It is an example. FIG. 22 is an example in which both end portions of each air gap 13 are communicated with the common communication passages 15 and 15 via the individual communication passages 15A and 15A, respectively, and the gas introduction holes 16 are formed at one end portions of the respective common communication passages 15 and 15. is there.

  In these examples, as the number of gas introduction holes and the number of common communication paths are relatively large, the gas can be efficiently introduced into the gap.

Next, still another example of the arrangement of the gas introduction hole and the common communication path in each of the above embodiments will be described with reference to FIG.
In this example, the gaps 13 are grouped into a required number to form gap groups 13G1 to 13Gn, sub-common communication paths 15S1 to 15Sn are formed for the gap groups 13G1 to 13Gn, and sub-common communication paths 15S1 to 15Sn are further formed. Is connected to one main common communication path 15M2, and this main common communication path 15M2 is connected to the gas introduction hole 16 via the main common communication path 15M1.

  In other words, the common communication path is branched into the gas introduction holes, and the gas communication holes are communicated with the gaps of the gap groups grouped according to the required number. As a result, the gas can be introduced into each gap 13 more uniformly.

Next, another example of the electrostatic actuator according to the present invention will be described with reference to FIG. In addition, the figure is a principal plane explanatory drawing of the actuator.
In this example, apart from the common communication path 15, a part of the partition wall portion 31 between the gaps 13 is removed to form the communication path 71, so that each gap 13 communicates with the adjacent gap 13. . Here, a part of the partition wall 31 where the sacrificial layer removal holes 29 between the gaps 13 are present is removed.

  As a result, gas introduction into each gap 13 or exhaust efficiency can be improved. However, in this case, it is important to communicate within a range in which crosstalk between the actuators does not occur.

Next, a liquid cartridge according to the present invention will be described with reference to FIG.
The liquid cartridge integrated head 100 includes an ink jet head 102 that is a droplet discharge head according to the present invention having nozzle holes 101 and the like, and an ink tank (liquid tank) that supplies recording liquid (ink) to the ink jet head 102. ) 103 is integrated.

  As described above, by integrating the ink tank (liquid tank) for supplying the recording liquid (ink) to the liquid droplet ejection head according to the present invention, there is little variation in the liquid droplet ejection characteristics, and a highly reliable liquid droplet ejection head is obtained. An integrated liquid cartridge (ink tank integrated head) can be obtained at low cost.

  Next, an example of an image forming apparatus according to the present invention equipped with an ink jet head which is a droplet discharge head according to the present invention will be described with reference to FIGS. 26 is a perspective explanatory view of the image forming apparatus, and FIG. 27 is a side explanatory view of a mechanism portion of the image forming apparatus.

  The image forming apparatus includes a carriage that can move in the main scanning direction inside the recording apparatus main body 111, a recording head that includes the droplet discharge head according to the present invention mounted on the carriage, a liquid cartridge that supplies recording liquid to the recording head, and the like. A sheet feeding cassette (or a sheet feeding tray) 114 on which a large number of sheets 113 can be stacked from the front side is removably inserted in the lower part of the apparatus main body 111. The manual feed tray 115 for manually feeding the paper 113 can be opened, the paper 113 fed from the paper feed cassette 114 or the manual feed tray 115 is taken in, and the printing mechanism section After a required image is recorded by 112, it is discharged onto a discharge tray 116 mounted on the rear side.

  The printing mechanism 112 holds a carriage 123 slidably in the main scanning direction by a main guide rod 121 and a sub guide rod 122 which are guide members horizontally mounted on left and right side plates (not shown). (Y), cyan (C), magenta (M), and black (Bk) recording liquid droplets (ink droplets) of the respective colors are ejected from a recording head 124 including a liquid droplet ejection head according to the present invention. The droplet discharge ports are arranged in a direction crossing the main scanning direction, and are mounted with the droplet discharge direction facing downward. Also, the liquid cartridges 125 for supplying the recording liquids of the respective colors to the head 124 are replaceably mounted on the carriage 123. In addition, it can also be set as the structure which mounts the liquid cartridge based on this invention.

  The liquid cartridge 125 has an air port that communicates with the atmosphere above, a supply port that supplies recording liquid to the droplet discharge head below, and a porous body filled with the recording liquid inside. The recording liquid supplied to the droplet discharge head is maintained at a slight negative pressure by the capillary force of the body.

  Further, although the heads 124 of the respective colors are used here as the recording heads, a single head having nozzles for ejecting recording droplets of the respective colors may be used.

  Here, the carriage 123 is slidably fitted to the main guide rod 121 on the rear side (downstream side in the paper conveyance direction), and is slidably mounted on the sub guide rod 122 on the front side (upstream side in the paper conveyance direction). is doing. In order to move and scan the carriage 123 in the main scanning direction, a timing belt 130 is stretched between a driving pulley 128 and a driven pulley 129 that are rotationally driven by a main scanning motor 127. The carriage 123 is reciprocally driven by forward and reverse rotations of the main scanning motor 127.

  On the other hand, in order to convey the sheet 113 set in the sheet cassette 114 to the lower side of the head 124, the sheet 113 is guided from the sheet feeding cassette 114 to the sheet feeding roller 131 and the friction pad 132. A guide member 133, a transport roller 134 that reverses and transports the fed paper 113, a transport roller 135 that is pressed against the peripheral surface of the transport roller 134, and a tip that defines the feed angle of the paper 113 from the transport roller 134 A roller 136 is provided. The transport roller 134 is rotationally driven by a sub-scanning motor 137 through a gear train.

  A printing receiving member 139 is provided as a paper guide member that guides the paper 113 fed from the transport roller 134 on the lower side of the recording head 124 corresponding to the movement range of the carriage 123 in the main scanning direction. On the downstream side of the printing receiving member 139 in the paper conveyance direction, a conveyance roller 141 and a spur 142 that are rotationally driven to send the paper 113 in the paper discharge direction are provided, and paper discharge that further feeds the paper 113 to the paper discharge tray 116. A roller 143 and a spur 144, and guide members 145 and 146 forming a paper discharge path are disposed.

  At the time of recording, the recording head 124 is driven according to the image signal while moving the carriage 123 to discharge the recording liquid onto the stopped sheet 113 to record one line, and after the sheet 113 is conveyed by a predetermined amount. Record the next line. Upon receiving a recording end signal or a signal that the trailing edge of the sheet 113 reaches the recording area, the recording operation is terminated and the sheet 113 is discharged.

  A recovery device 147 for recovering defective ejection of the head 124 is disposed at a position outside the recording area on the right end side in the movement direction of the carriage 123. The recovery device 147 includes a cap unit, a suction unit, and a cleaning unit. The carriage 123 is moved to the recovery device 147 side during printing standby, and the head 124 is capped by the capping unit, and the ejection port portion is kept in a wet state to prevent ejection failure due to recording liquid drying. Further, by ejecting a recording liquid not related to recording during recording or the like, the recording liquid viscosity of all the ejection ports is made constant and stable ejection performance is maintained.

  When ejection failure occurs, the ejection port (nozzle) of the head 124 is sealed with a capping unit, and bubbles and the like are sucked out together with the recording liquid from the ejection port with a suction unit through the tube. Dust and the like are removed by the cleaning means, and the ejection failure is recovered. The sucked recording liquid is discharged to a waste liquid receiving portion (not shown) installed at the lower part of the main body, and is absorbed and held by the liquid absorber of the waste liquid receiving portion.

  As described above, according to the image forming apparatus of the present invention, since the liquid droplet ejection head or the liquid cartridge according to the present invention is provided, high-quality recording can be performed.

Next, a micro pump as a micro device provided with the electrostatic actuator according to the present invention will be described with reference to FIG. In addition, the figure is principal part cross-sectional explanatory drawing of the micropump.
This micro pump has an actuator substrate 201 constituted by an electrostatic actuator according to the present invention and a flow path substrate 202, and a flow path 203 through which a fluid flows is formed in the flow path substrate 202. The actuator substrate 201 includes a vibration plate 212 that forms the wall surface of the flow path 203, and an individual electrode 214 that faces the deformable region 212A of the vibration plate 212 via a gap 213 formed by sacrificial layer etching.

  The configuration of the actuator substrate 1 is the same as that of each of the above embodiments. An insulating film 222 is formed on the silicon substrate 221, an individual electrode 214 is formed on the insulating film 222, and the insulating film 225 is covered. A sacrificial layer 227 is formed on the film 225, a part of the diaphragm 212 is further formed, and then the sacrificial layer is etched to form a gap 213. Although not shown, a common communication path that communicates each gap 213 is formed.

  The operation principle of the micropump will be described. As in the case of the droplet discharge head described above, by selectively applying a pulse potential to the individual electrode 214, the suction action by the electrostatic force is performed between the diaphragm 212 and the diaphragm 212. As a result, the deformable region 212A of the diaphragm 212 is deformed to the electrode 214 side. Here, by sequentially driving the deformable region 212A of the diaphragm 212 from the right side in the figure, the fluid in the flow path 203 flows in the direction of the arrow, and the fluid can be transported.

  Thus, by providing the electrostatic actuator according to the present invention, a small and low-power-consumption micropump capable of stable liquid transportation can be obtained. In order to increase transport efficiency, one or more valves, such as a check valve, may be provided between the deformable regions.

Next, an example of an optical device provided with the electrostatic actuator according to the present invention will be described with reference to FIG. This figure is a schematic configuration diagram of the device.
This optical device has an actuator substrate 301 including a mirror 300 corresponding to a diaphragm whose surface can reflect light and can be deformed. A dielectric multilayer film or a metal film is preferably formed on the surface of the mirror 300 in order to increase the reflectance (these are formed on the resin film surface).

  The actuator substrate 301 has a deformable mirror 300 (corresponding to a vibration plate of the head) on a base substrate 321 on which an insulating film 322 is formed, and a deformable region 300A of the mirror 300 via a predetermined gap 313. And an opposing electrode 314. Further, an insulating film 325 is formed over the electrode 314, and the gap 313 is formed by etching the sacrificial layer 327. Other configurations are different from those described in the foregoing embodiment of the electrostatic actuator in that the diaphragm has a mirror surface, and thus detailed illustration and description are omitted.

  The principle of this optical device will be described. As in the case of the electrostatic actuator described above, by selectively applying a pulse potential to the electrode 314, the deformable region 300A of the mirror 300 facing the electrode 314 is deformed. Since a suction action due to electrostatic force occurs, the deformable region 300A of the mirror 300 is deformed into a concave shape to form a concave mirror. Therefore, when the light from the light source 330 is applied to the mirror 300 via the lens 331, the light is reflected at the same angle as the incident angle when the mirror 300 is not driven, but is driven when the mirror 300 is driven. Since the deformable region 300A becomes a concave mirror, the reflected light becomes divergent light. Thereby, an optical modulation device can be realized.

  Thus, by providing the electrostatic actuator according to the present invention, a small and low power consumption optical device can be obtained.

  An example in which this optical device is applied will be described with reference to FIG. In this example, the optical devices described above are two-dimensionally arranged, and the deformable region 300A of each mirror 300 is driven independently. Although a 4 × 4 array is shown here, it is possible to arrange more than this.

  Accordingly, similarly to FIG. 29 described above, the light from the light source 330 is irradiated to the mirror 300 via the lens 331, and the light incident on the portion where the mirror 300 is not driven enters the projection lens 332. On the other hand, the portion where the deformable area A of the mirror 300 is deformed by applying a voltage to the electrode 314 becomes a concave mirror, so that light diverges and hardly enters the projection lens 732. The light incident on the projection lens 332 is projected on a screen (not shown) or the like, and an image can be displayed on the screen.

  In the above-described embodiment, the example in which the ink jet head is applied as a liquid droplet ejection head has been described. However, as a liquid droplet ejection head other than the ink jet head, for example, a liquid droplet ejection head that ejects liquid resist as liquid droplets, DNA The present invention can also be applied to other droplet discharge heads such as a droplet discharge head that discharges the sample as droplets. Electrostatic actuators and their manufacturing methods include not only micro pumps and optical devices (light modulation devices), but also micro switches (micro relays), multi optical lens actuators (light switches), micro flow meters, pressure sensors, etc. It can also be applied to.

FIG. 3 is a perspective explanatory view of a droplet discharge head according to the present invention including the electrostatic actuator according to the first embodiment of the present invention. It is a disassembled perspective explanatory drawing of the head. FIG. 2 is a cross-sectional explanatory view taken along a surface S1 in FIG. FIG. 2 is an explanatory cross-sectional view along a surface S2 of FIG. It is principal part plane explanatory drawing of the actuator board | substrate which comprises the electrostatic actuator. FIG. 6 is a cross-sectional explanatory view taken along line AA in FIG. 5. FIG. 6 is a cross-sectional explanatory view taken along line BB in FIG. 5. It is principal part expanded sectional explanatory drawing of FIG. It is principal part expanded sectional explanatory drawing similar to FIG. 7 with which it uses for description of a comparative example. FIG. 6 is an explanatory cross-sectional view corresponding to a cross section taken along line AA of FIG. 5 for explaining the manufacturing process of the actuator substrate to which the manufacturing method according to the present invention is applied. It is explanatory drawing with which it uses for description of the process following FIG. It is explanatory drawing with which it uses for description of the process following FIG. FIG. 6 is a cross-sectional explanatory view corresponding to a cross section taken along line BB in FIG. 5 for explaining the manufacturing process of the actuator substrate. It is explanatory drawing with which it uses for description of the process following FIG. It is explanatory drawing with which it uses for description of the process following FIG. It is a plane explanatory view used for explanation of an actuator substrate which constitutes an electrostatic actuator concerning a 2nd embodiment of the present invention. It is sectional explanatory drawing which follows the CC line of FIG. It is sectional explanatory drawing which follows the DD line | wire of FIG. It is typical explanatory drawing with which it uses for description of the 1st example of arrangement | positioning of the common communicating path and gas introduction hole in each embodiment. It is a typical explanatory view similarly used for explanation of the 2nd example. It is a typical explanatory view similarly provided for description of the third example. It is a typical explanatory view similarly provided for description of the fourth example. It is typical explanatory drawing with which it uses for description of the other example of arrangement | positioning of the common communicating path and gas introduction hole in each embodiment. It is a plane explanatory view used for explanation of other examples of the electrostatic actuator according to the present invention. FIG. 6 is a perspective explanatory view for explaining a liquid cartridge according to the present invention. 1 is a perspective explanatory view illustrating an example of an image forming apparatus according to the present invention. It is explanatory drawing of the mechanism part of the image forming apparatus. It is explanatory drawing explaining an example of the micropump which concerns on this invention. It is explanatory drawing explaining an example of the optical device which concerns on this invention. It is an isometric view explanatory drawing used for description of the application example of the same optical device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Actuator board | substrate 2 ... Flow path board | substrate 3 ... Nozzle board | substrate 4 ... Nozzle hole 5 ... Nozzle communication path 6 ... Liquid chamber (discharge chamber)
DESCRIPTION OF SYMBOLS 7 ... Fluid resistance part 9 ... Liquid chamber space | interval wall 10 ... Common liquid chamber 11 ... Actuator element 12 ... Diaphragm 13 ... Air gap 14 ... Individual electrode 15 ... Common communication path 15A ... Individual communication path 24 ... Electrode formation layer (lower layer film)
25. Insulating film (intermediate film)
26 ... Opening 27 ... Sacrificial layer 28 ... Insulating film 29 ... Sacrificial layer removal hole 32 ... Diaphragm electrode (upper electrode)
33 ... Film bending prevention film (nitride film)
34 ... Film rigidity adjusting film 35 ... Resin film 100 ... Liquid cartridge 111 ... Image forming apparatus 124 ... Recording head 201, 301 ... Actuator substrate

Claims (9)

In an electrostatic actuator comprising a deformable diaphragm and an electrode facing the diaphragm through a gap formed by sacrificial layer etching, and deforming the diaphragm with an electrostatic force,
The plurality of gaps communicate with each other through a common communication path,
The common communication path is formed by removing a sacrificial layer that forms the gap, and a first portion that is formed by removing the electrode forming layer that communicates with the first portion and forms the electrode. Two parts,
The electrostatic actuator, wherein a length of a short side cross section of the second portion is longer than a length of a short side cross section of the first portion of the common communication path . 2. The electrostatic actuator according to claim 1 , wherein the common communication path communicates with the outside or a buffer chamber. 3. The electrostatic actuator according to claim 1 or 2 , wherein the common communication path is branched. In the method for manufacturing an electrostatic actuator as claimed in any one of claims 1 to 3, wherein the common connection path is electrostatic actuator, characterized in that formed at the same time of forming a sacrificial layer etching said gap Manufacturing method. 4. A droplet discharge head comprising an electrostatic actuator for discharging droplets from a nozzle, wherein the electrostatic actuator is the electrostatic actuator according to any one of claims 1 to 3. Droplet discharge head. The liquid droplet ejection head according to claim 5 , wherein the liquid droplet ejection head for ejecting liquid droplets and an ink tank for supplying a recording liquid to the liquid droplet ejection head are integrated. A liquid cartridge characterized by. 8. An image forming apparatus equipped with a droplet discharge head for discharging droplets, wherein the droplet discharge head is the droplet discharge head according to claim 5 or the droplet discharge head of the liquid cartridge according to claim 7. An image forming apparatus. 4. A micropump for transporting liquid by an electrostatic actuator, wherein the electrostatic actuator is the electrostatic actuator according to any one of claims 1 to 3 . 4. An optical device that changes the reflection direction of light by an electrostatic actuator, wherein the electrostatic actuator is the electrostatic actuator according to any one of claims 1 to 3 .

Images