JP2015085565A - Droplet discharge head and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a droplet discharge head that obtains damper effect, which achieves good pressure fluctuation propagated to a common liquid chamber, and inhibits vaporization of a moisture content from the common liquid chamber thereby achieving good discharge performance over a long time.SOLUTION: A droplet discharge head includes: multiple nozzles 9; an individual liquid chamber 10 communicating with the nozzles; a common liquid chamber 14 communicating with the individual liquid chamber; a piezoelectric element 4 for increasing pressure of the individual liquid chamber; a damper layer 8 forming one wall surface of the common liquid chamber; an air storage chamber 15 which is provided so as to face the common liquid chamber through the damper layer; and a valve 20 which allows the air storage chamber 15 to communicate with an exterior part 16.

Description

  The present invention relates to a droplet discharge head that discharges droplets from a nozzle, and an image forming apparatus that forms an image by discharging droplets from a droplet discharge head onto a recording material.

  As an image forming apparatus such as a printer, a facsimile, a copying apparatus, a plotter, and a complex machine of these, for example, a liquid discharge recording type image forming apparatus (for example, ink jet recording) using a recording head composed of a droplet discharge head that discharges ink droplets. Device) is known. This liquid discharge recording type image forming apparatus forms an image by discharging ink droplets from a recording head onto a recording material conveyed. A line using a serial type image forming apparatus that forms an image by ejecting droplets while the recording head moves in the main scanning direction, and a line type head that forms images by ejecting droplets without moving the recording head There is a type image forming apparatus.

  The image forming apparatus here forms an image on a recording material, but the material of the recording material is not limited to paper, but OHP, thread, fiber, fabric, leather, metal, plastic, It means an apparatus for forming an image by discharging a liquid onto any recording material such as glass, wood and ceramics. Image formation not only applies an image having a meaning such as a character or a figure to a recording material, but also applies an image having no meaning such as a pattern to the recording material (simply ejects a droplet). ) Also means. The liquid ejected as droplets is not limited to so-called ink, and is not particularly limited as long as it becomes liquid when ejected, and includes, for example, DNA samples, resists, pattern materials, and the like. It is. In addition, the “image” is not limited to a planar image, and includes an image given to a three-dimensionally formed image and an image formed by three-dimensionally modeling a solid itself.

  The droplet discharge head includes a plurality of nozzles, a plurality of individual liquid chambers communicating with each nozzle, an actuator that generates energy for boosting each individual liquid chamber, and a common liquid chamber communicating with each individual liquid chamber. Configurations provided are known. In this droplet discharge head, the ink is supplied from the common liquid chamber to each individual liquid chamber communicating with each nozzle, and the actuator corresponding to each individual liquid chamber is driven to boost the pressure in each individual liquid chamber, and the ink from the nozzles. Liquid droplets are discharged.

  At this time, the pressure fluctuation generated in the individual liquid chambers also propagates to the common liquid chambers communicating with the individual liquid chambers. If mutual interference occurs that affects the ink in the adjacent individual liquid chambers due to the pressure fluctuation propagated to the common liquid chamber, it may cause unintended droplet leakage and ejection, and instability of the ejection state. Preventing high-quality image output.

  In order to solve the above-mentioned mutual interference problem, one wall surface of the common liquid chamber is formed of a damper film such as a deformable resin film, and an air storage chamber provided to face the common liquid chamber via the damper film; A configuration is known in which a damper mechanism having a communication passage for communicating the air storage chamber with the outside is provided (for example, Patent Document 1). In this configuration, the pressure fluctuation propagated to the common liquid chamber when the actuator is driven so as to increase the pressure in each individual liquid chamber, the damper film forming one wall surface of the common liquid chamber faces the common liquid chamber side. By deforming to escape to the air storage chamber. Since the air storage chamber communicates with the outside through the communication path, the pressure in the air storage chamber is maintained at the same pressure as the outside.

  Patent Document 2 describes a droplet discharge head in which a communication path for communicating an air storage chamber provided so as to face a common liquid chamber via a damper film to the outside is an elongated path.

  Patent Document 3 describes a liquid droplet ejection head that has an air layer above the common liquid chamber and can communicate with the outside by a valve that can open and close the air layer.

  In the droplet discharge head of Patent Document 1, an air storage chamber that faces the common liquid chamber and the diaphragm is opened to the atmosphere through a ventilation path. In the configuration in which the air storage chamber is opened to the atmosphere, the water in the ink in the common liquid chamber gradually becomes water vapor, diffuses through the resin film and diffuses into the air storage chamber, and then enters the air via the communication path. Spread. As described above, when water is volatilized from the ink in the common liquid chamber, the viscosity of the ink gradually increases, and good ejection performance cannot be obtained. On the other hand, if the air storage chamber is sealed without providing a communication passage that communicates with the outside, an increase in the viscosity of the ink in the common liquid chamber is prevented, but the pressure in the air storage chamber increases and the resin film is on the air storage chamber side. It becomes difficult to deform and the damper effect decreases.

  In the liquid droplet ejection head of Patent Document 2, the volatilization of moisture in the ink in the common liquid chamber can be suppressed to some extent by connecting the air storage chamber and the outside through an elongated passage, but the volatilization can be suppressed at a higher level. It is desired.

  In the droplet discharge head of Patent Document 3, the pressure fluctuation propagated to the common liquid chamber is attenuated by changing the volume of the air layer above the common liquid chamber. The air layer valve is normally closed and prevents water vapor from evaporating from the ink and diffusing from the air layer to the outside. When the air layer pressure deviates from a predetermined range, the air layer valve is opened to adjust the pressure, and the air layer maintains the effect of attenuating pressure fluctuations in the common liquid chamber. However, this droplet discharge head does not have a damper film between the ink in the common liquid chamber and the air layer. For this reason, the ink directly touches the air layer, and bubbles are inevitably mixed into the ink, and it is difficult to maintain good ejection performance. Further, if it is attempted to obtain the effect of attenuating the pressure fluctuation of the common liquid chamber only by the air layer without providing the damper film, it is necessary to provide a large air layer, leading to an increase in the size of the droplet discharge head.

  The present invention has been made in view of the above problems, and its purpose is to obtain a good damper effect of pressure fluctuations propagated in the common liquid chamber, and to suppress the volatilization of moisture from the common liquid chamber. It is an object of the present invention to provide a liquid droplet ejection head and an image forming apparatus that can obtain good ejection performance over a wide range.

  In order to achieve the above object, the invention of claim 1 is directed to a plurality of nozzles for discharging droplets, a plurality of individual liquid chambers communicating with the nozzles, and a common liquid communicating with the plurality of individual liquid chambers. A chamber, an actuator for raising the pressure of the individual liquid chamber, a flexible member forming at least a part of the common liquid chamber, and the common liquid chamber so as to face the common liquid chamber via the flexible member. In the liquid droplet ejection head provided with the air storage chamber, a valve that enables communication between the air storage chamber and the outside is provided.

  According to the present invention, it is possible to obtain a good damper effect of pressure fluctuation propagated into the common liquid chamber, to suppress the volatilization of moisture from the common liquid chamber, and to obtain a good discharge performance over a long period of time. There is an effect.

It is principal part sectional drawing of the inkjet recording head which concerns on this embodiment. It is explanatory drawing of an example of the valve which enables communication with an air storage chamber and the exterior. It is explanatory drawing of the other example of the valve which enables communication with an air storage chamber and the exterior. It is explanatory drawing which shows schematic structure of the serial type inkjet recording device provided with the inkjet recording head which concerns on this embodiment. FIG. 5 is a plan view of a main part of the serial type inkjet recording apparatus of FIG. 1 is a cross-sectional view of a line type ink jet recording apparatus including an ink jet recording head according to an embodiment.

Embodiments of the present invention will be described below with reference to the drawings.
First, the droplet discharge head of the present invention will be described using an inkjet recording head as one embodiment. In the following description, a piezoelectric element is used as an actuator that generates energy for boosting the individual liquid chambers of the ink jet recording head. While this actuator is compatible with inks with a wide range of physical properties, it has been difficult to increase the density of the individual liquid chambers and reduce the size of the head. However, in recent years, a method for increasing the density and reducing the size by using a so-called MEMS (Micro Electro Mechanical Systems) technique has been established. That is, a unimorph type actuator is formed by laminating a diaphragm, an electrode layer, a piezoelectric layer, etc. in a separate liquid chamber using a thin film forming technique. By patterning this into individual piezoelectric elements and electrodes / wiring members using a semiconductor device manufacturing process such as photolithography, the density and size are reduced.

  FIG. 1 is a cross-sectional view of a main part of an ink jet recording head according to the present embodiment. The ink jet recording head includes a nozzle plate 1, an individual liquid chamber substrate 2, a vibration plate 3, a piezoelectric element 4, a driving IC 5, a holding substrate 6, a frame member 7, a damper layer 8, and the like. The individual liquid chamber substrate 2 is a substrate on which the partition portion of the individual liquid chamber 10, the fluid resistance (not shown), and the ink supply port 11 are formed. A diaphragm 3 that forms one surface of the individual liquid chamber 10 is laminated on the individual liquid chamber substrate 2. On the diaphragm 3, the piezoelectric element 4 as an actuator for boosting the inside of the individual liquid chamber 10, a driving IC 5 that outputs a driving signal to the piezoelectric element 4, and a wiring (not shown) between the piezoelectric element 4 and the driving IC 5. Etc. are formed. The diaphragm 3 has an opening corresponding to the ink supply port 11 to the individual liquid chamber 10. The nozzle plate 1 having the nozzles 9 is joined to the surface of the individual liquid chamber substrate 2 opposite to the surface on which the vibration plate 3 is laminated. A holding substrate 6 having an opening 12 serving as an ink flow path and a frame member 7 forming a common liquid chamber 14 are stacked on the individual liquid chamber substrate 2 on which the piezoelectric element 4 and the driving IC 5 are formed.

  An ink flow path is formed by such a laminated structure of the frame member 7, the holding substrate 6, the vibration plate 3, the individual liquid chamber substrate 2, and the nozzle plate 1. Specifically, the individual liquid is supplied from the common liquid chamber 14 of the frame member 7 through the opening 12 of the holding substrate 6, the opening of the diaphragm 3, the ink supply port 11 of the individual liquid chamber substrate 2, and fluid resistance (not shown). Ink is supplied into the chamber 10. By driving the piezoelectric element 4 formed on the diaphragm 3 that forms one wall surface of the individual liquid chamber substrate 2 and displacing the diaphragm 3, the pressure in the individual liquid chamber 10 is increased and ink droplets are ejected from the nozzles 9. Is discharged. The piezoelectric element 4 has a configuration in which a piezoelectric body is sandwiched between a lower electrode and an upper electrode, and is driven by a drive IC 5 connected to a wiring member drawn from the upper electrode and the lower electrode.

  Further, the frame member 7 has a damper layer 8 made of a flexible member that forms the upper surface of the common liquid chamber 14 inside, and an air storage chamber 15 is formed on the upper portion of the damper layer 8, and the air storage chamber A valve 20 is formed to enable communication between 15 and the outside 16. When the piezoelectric element 4 is driven to increase the pressure in the individual liquid chamber 10 to eject ink droplets from the nozzle 9, the pressure fluctuation generated in the individual liquid chamber 10 is also propagated to the common liquid chamber 14 that communicates. The pressure fluctuation propagated to the common liquid chamber 14 is released to the air storage chamber 15 as the damper layer 8 forming the upper surface of the common liquid chamber 14 is deformed to the air storage chamber 15 side facing the common liquid chamber 14. Thus, mutual interference that affects the ink in the adjacent individual liquid chamber 10 due to the pressure fluctuation propagated to the common liquid chamber 14 is prevented.

Hereinafter, the constituent members of the ink jet recording head of this embodiment will be described in detail.
The nozzle plate 1 is a substrate on which nozzles 9 for ink ejection are arranged, and any material can be used from the required rigidity and workability. Examples thereof include metals or alloys such as SUS and nickel, inorganic materials such as silicon and ceramics, and resin materials such as polyimide. The processing method of the nozzle 9 can be selected arbitrarily from the characteristics of the substrate material and the required accuracy and workability, such as electroforming plating method, etching method, pressing method, laser processing method, photolithography method, etc. Etc. The opening diameter, the number of arrays, and the array density of the nozzles 9 can be set to an optimum combination according to the specifications required for the ink jet recording head.

  In the individual liquid chamber substrate 2, a partition wall portion, a fluid resistance portion (not shown), and an ink supply port 11 of the individual liquid chamber 10 are formed. Any material can be used as the material of the individual liquid chamber substrate 2 in view of workability and physical properties. For example, it is preferable to use a silicon substrate capable of using a photolithography method at 300 dpi (about 85 [μm] pitch). . Any processing of the individual liquid chamber 10 can be used, but when the above-described photolithography method is used, either a wet etching method or a dry etching method can be used. In any method, since the individual liquid chamber 10 side of the diaphragm 3 is made of a silicon dioxide film or the like, an etch stop layer can be formed, so that the height of the individual liquid chamber 10 can be controlled with high accuracy.

The individual liquid chamber 10 has a function of applying pressure to the ink and discharging droplets from the nozzle 9. The individual liquid chamber substrate 2 is integrally formed with a diaphragm 3 that forms one wall surface of the individual liquid chamber 10 and a piezoelectric element 4 in which a lower electrode, a piezoelectric body, and an upper electrode are laminated. Although any diaphragm 3 can be used, it is preferable to use a material having high rigidity such as silicon, nitride, oxide, or carbide. Alternatively, a stacked structure of these materials may be used. In the case of a laminated film, it is preferable that the residual stress is reduced in consideration of the internal stress of each material. For example, in the case of stacked the _Si 3 _{N 4} and SiO _2, the SiO ₂ serving as the _Si 3 _{N 4} as the tensile stress and compressive stress are alternately stacked, arrangement of stress relaxation can be mentioned as an example.

  The thickness of the diaphragm 3 can be selected according to desired characteristics, but is generally preferably in the range of 0.5 to 10 [μm], more preferably in the range of 1.0 to 5.0 [μm]. . If the diaphragm 3 is too thin, the diaphragm 3 is liable to be damaged due to cracks or the like, and if it is too thick, the displacement amount becomes small and the discharge efficiency is lowered. Moreover, when too thin, the natural frequency of the diaphragm 3 is lowered, and there is a problem that the drive frequency cannot be increased.

  The lower electrode (not shown) and the upper electrode (not shown) constituting the piezoelectric element 4 can be made of any conductive material. For example, metals, alloys, and conductive compounds can be raised. A single layer film or a laminated film of these materials may be used. Moreover, since it is necessary to select a material that does not react with or diffuse with the piezoelectric body, it is necessary to select a highly stable material. In addition, an adhesive layer may be formed in consideration of adhesiveness with the piezoelectric body and the diaphragm 3 as necessary. Examples of the electrode material include Pt, Ir, Ir oxide, Pd, Pd oxide, and the like as highly stable materials. Further, examples of the adhesion layer with the diaphragm 3 include Ti, Ta, W, and Cr.

  As the piezoelectric material constituting the piezoelectric body, a ferroelectric material exhibiting piezoelectricity can be used. For example, lead zirconate titanate and barium titanate are generally used. Arbitrary methods can be used as the method for forming the piezoelectric body, and examples thereof include a sputtering method and a sol-gel method, and the sol-gel method is preferable because the film forming temperature is low. The upper electrode and the piezoelectric body need to be patterned for each individual liquid chamber 10. For patterning, a normal photolithography method can be used. Also, when the piezoelectric film is formed by the sol-gel method, a spin coating method or a printing method can also be used.

  The piezoelectric element 4 needs to be formed above the individual liquid chamber 10. When formed on the partition wall that divides the individual liquid chamber 10, the deformation of the diaphragm 3 is hindered, which causes a decrease in discharge efficiency and damage of the piezoelectric element due to stress concentration.

  A fluid resistance portion (not shown) communicating with the individual liquid chamber 10 is formed on the individual liquid chamber substrate 2. The fluid resistance unit has a function of supplying ink from the ink supply port 11 to the individual liquid chamber 10. At the same time, the piezoelectric element 4 is driven to have a function of preventing ink backflow and discharging from the nozzle 9 by the pressure generated in the individual liquid chamber 10. Therefore, it is necessary to reduce the cross-sectional area of the individual liquid chamber 10 in the ink flow direction and increase the fluid resistance. When silicon is used for the individual liquid chamber substrate 2 and the individual liquid chamber 10 and the fluid resistance portion are formed by etching using a photolithography method, there is an advantage that processing can be performed under the same conditions as the individual liquid chamber 10. In order to increase the fluid resistance by making the height of the fluid resistance portion lower than that of the individual liquid chamber 10, it is necessary to control the overetching amount of the individual liquid chamber 10 by time management. For this reason, fluid resistance cannot be made uniform due to variations in etching rate. As a result, the discharge uniformity is deteriorated.

  The fluid resistance portion communicates with the common liquid chamber 14 formed in the frame member 7 through the ink supply port 11 and the opening portion 12 formed in the holding substrate 6. The individual liquid chambers 10 are partitioned by partition walls, and corresponding piezoelectric elements 4 are formed. The height of the individual liquid chamber 10 can be arbitrarily set from the head characteristics, but is preferably in the range of 20 to 100 [μm]. Moreover, although the partition part of the individual liquid chamber 10 can be arbitrarily set according to the arrangement density, the width of the partition part is preferably 10 to 30 [μm]. When the partition wall is narrow, when the piezoelectric element 4 in the adjacent individual liquid chamber 10 is driven, mutual interference between the adjacent individual liquid chambers 10 occurs, and the discharge variation increases. When narrowing the width of the partition wall, it is possible to reduce the height of the liquid chamber.

  Although illustration is omitted, wiring to the piezoelectric element 4 will be described. In order to input a drive signal to the piezoelectric elements 4 arranged above the individual liquid chambers 10, individual wiring is drawn from the upper electrode constituting the piezoelectric element 4, and common wiring is drawn from the lower electrode. From the upper electrode, it is pulled out to the individual wiring pad via the individual wiring and connected to the drive IC 5. Furthermore, it is pulled out from the driving IC 5 to the connection pad provided on one end side in the longitudinal direction via the wiring. The lower electrode is drawn to the connection pad through the common wiring. The connection pads are connected to the head external circuit by a flexible printed circuit board (hereinafter abbreviated as FPC). A drive control signal is sent from the head external circuit to the drive IC 5 via the FPC.

The wiring is preferably formed by the same material and the same process. As the wiring material, a metal / alloy / conductive material having a low resistance value can be used. Further, it is necessary to use a material having a low contact resistance for the upper electrode and the lower electrode. For example, Al, Au, Ag, Pd, Ir, W, Ti, Ta, Cu, Cr and the like can be exemplified, and a laminated structure of these materials may be used in order to reduce contact resistance. As a material for reducing the contact resistance, any conductive compound may be used. Examples thereof include oxides such as Ta ₂ O ₅ , TiO ₂ , TiN, ZnO, In ₂ O ₃ and SnO, nitrides, and composite compounds thereof.

  The film thickness of the wiring can be arbitrarily set, but is preferably 3 [μm] or less. In addition, it is preferable to employ a film forming method with high film thickness uniformity such as a vacuum film forming method. Since these wirings also serve as a joint surface with the holding substrate 6 to be described later, it is necessary to adopt a film thickness / film forming method capable of ensuring height uniformity.

Since the individual liquid chamber substrate 2 is as thin as 20 to 100 [μm], the holding substrate 6 is bonded to the side facing the nozzle plate 1 in order to ensure the rigidity of the individual liquid chamber substrate 2. Although any material can be used as the material of the holding substrate 6, it is necessary to select a material having a thermal expansion coefficient close to prevent the individual liquid chamber substrate 2 from warping. Therefore, it is preferable to use ceramic materials such as glass, silicon, SiO ₂ , ZrO ₂ , and Al ₂ O ₃ .

  The holding substrate 6 has an opening 12 communicating with the individual liquid chamber arrangement direction, and forms a part of the common liquid chamber 14. Further, in order to secure a space in which the diaphragm 3 can be displaced by driving the piezoelectric element 4, the holding substrate recess 13 is formed in a region of the holding substrate 6 that faces the piezoelectric element 4. Although not shown, it is preferable that the holding substrate recess 13 is divided for each individual liquid chamber 10 and bonded on the individual liquid chamber partition walls. As a result, the rigidity of the individual liquid chamber substrate 2 having a small plate thickness can be increased, and mutual interference between adjacent individual liquid chambers when the piezoelectric element 4 is driven can be reduced. For this reason, the holding substrate 6 is preferably not a low-rigidity material such as resin but a high-rigidity material such as silicon. Further, since the holding substrate recess 13 is partitioned for each individual liquid chamber 10, high processing accuracy is required for high density, and in the 300 dpi head, the partition wall width of the holding substrate 6 is 5 to 20 [μm]. Is desirable.

  The frame member 7 includes a common liquid chamber 14 that is long in the arrangement direction of the individual liquid chambers that store ink to be supplied to the individual liquid chambers 10, and a damper layer 8 that includes a flexible member that forms the upper surface of the common liquid chamber 14. And an air storage chamber 15 facing the common liquid chamber 14 via the damper layer 8. The frame member 7 includes a valve 20 that allows the air storage chamber 15 and the outside 16 to communicate with each other.

  As the frame member 7, an arbitrary one can be used in view of necessary rigidity and workability, but it is preferable to mold a resin from the viewpoint of cost, and it is preferable to use a material such as epoxy or polyphenyl sulfide. After the frame member 7 itself having an opening is molded by injection molding, the damper layer 8 is formed. Examples of the damper layer 8 include a silicone elastomer molded by injection molding. In order to increase the compliance, it is preferable to form the damper layer 8 as thin as possible and to use a material having a low Young's modulus. The thickness of the damper layer 8 is preferably 50 to 500 [μm], and the Young's modulus is preferably 10 [MPa] or less.

  A valve 21 that enables communication between the air storage chamber 15 and the outside 16 will be described with reference to the drawings. FIG. 2 is an explanatory diagram of an example of a valve that allows the air storage chamber 15 and the outside 16 to communicate with each other. FIG. 2 shows a configuration in which one valve 21 having a shape in which two plate-like portions 21 a and 21 b are connected by a rod-like portion 21 c is provided in the opening 17 of the frame member 7 as the valve 21. The material of the valve 21 is preferably a low density, and a resin is suitable. The width of the plate-like portion 21 a as the closing portion of the valve 21 is wider than the width of the opening 17, and the length of the rod-like portion 21 c is longer than the height of the opening 17.

  When the pressure of the air storage chamber 15 is substantially the same as the pressure of the external 16, the valve 21 is closed because the plate-like portion 21 a closes the opening 17 by its own weight as shown in FIG. ing. When the ink jet recording head is not driven (when the piezoelectric element 4 is not driven and no pressure is generated in the individual liquid chamber 10), the pressure in the air storage chamber 15 does not change, so the valve 21 is closed. The air storage chamber 15 is kept in a sealed state. Therefore, even if water vapor diffuses from the common liquid chamber 14 to the air storage chamber 15 via the damper layer 8, it does not diffuse to the outside 16, so that an increase in the viscosity of the ink in the common liquid chamber 14 can be suppressed.

  On the other hand, as the ink jet recording head is driven (when the piezoelectric element 4 is driven and pressure is generated in the individual liquid chamber 10), the damper layer 8 is deformed and pressure fluctuation occurs in the air storage chamber 15. When the pressure in the air storage chamber 15 becomes higher than the pressure in the external 16 due to this pressure fluctuation, the plate-like portion 21b is pushed up as shown in FIG. While being opened, air flows from the inside of the air storage chamber 15 to the outside 16 (arrow A in the figure). Thereby, the pressure of the air storage chamber 15 becomes the same pressure as the outside 16, and then the valve 21 returns to the closed state by its own weight. That is, as the ink jet recording head is driven, the valve 21 opens, and the outside 16 and the air storage chamber 15 communicate with each other. Thereby, it is prevented that the damper layer 8 becomes difficult to deform | transform, and a favorable damper effect can be maintained.

  Furthermore, by providing a valve that allows the air storage chamber 15 and the outside 16 to communicate with each other, an ink jet recording head caused by a change in the pressure (atmospheric pressure) of the outside 16 due to the use environment that occurs in a configuration in which the air storage chamber 15 is sealed. Can be prevented from occurring. Specifically, when the use environment is highland, the pressure (atmospheric pressure) of the outside 16 is low, but when the air storage chamber 15 is sealed, the pressure of the air storage chamber 15 does not change. Becomes higher than the pressure of the external 16. For this reason, the damper layer 8 may be deformed toward the common liquid chamber 14 due to the pressure of the air storage chamber 15, and ink may leak from the nozzle 9 communicating with the common liquid chamber 14. On the other hand, when the usage environment is low, the pressure (atmospheric pressure) of the external 16 is high, but if the air storage chamber 15 is sealed, the pressure of the air storage chamber 15 does not change. It becomes higher than the pressure in the storage chamber 15. For this reason, the damper layer 8 is deformed toward the air storage chamber 15 and the air storage chamber 15 is contracted. If the air storage chamber 15 is kept in a contracted state, air is trapped inside the head from the nozzle 9 and air may enter the individual liquid chamber 10 to affect the ink discharge performance.

  In the ink jet recording head of this embodiment, when the usage environment is high and the pressure of the external 16 is low, the pressure in the air storage chamber 15 becomes higher than the pressure of the external 16 and the plate-like portion is pushed up. Acts on 21b. Specifically, when the force that pushes up the valve 21 is greater than the force that pushes down the valve 21 due to the relationship between the pressure difference between the outside 16 and the inside of the air storage chamber 15 and the dead weight of the valve 21, FIG. As shown, the valve 21 is opened, and air flows from the air reservoir 15 to the outside 16 (arrow A in the figure). Thereby, the pressure in the air storage chamber 15 becomes the same pressure as the pressure of the outside 16 (atmospheric pressure), and it is possible to prevent ink from leaking from the nozzle 9.

  On the other hand, when the usage environment is low and the pressure of the outside 16 is high, a force that draws air from the nozzle 9 into the ink jet recording head acts, and a force that contracts the air storage chamber 15 acts on the damper layer 8. The valve 21 is lifted and opened by the force, and air is introduced from the outside 16 into the air storage chamber 15 (arrow B in the figure). Thereby, the pressure in the air storage chamber 15 becomes the same as the pressure of the external 16, and the contracted state of the air storage chamber 15 is eliminated, so that it is possible to prevent air from being entrained from the nozzle 9.

  FIG. 3 is an explanatory diagram of another example of a valve that enables communication between the air storage chamber 15 and the outside 16. FIG. 3 shows two valves, an intake valve 22 that performs intake from the external 16 to the air storage chamber 15 and an exhaust valve 23 that performs exhaust from the air storage chamber 15 to the external 16. The openings 18 and 19 are provided respectively. The intake valve 22 and the exhaust valve 23 have plate-like portions 22a and 23a and springs 22b and 23b that are elastic members for urging the plate-like portions 22a and 23a, respectively. The opening 18 of the intake valve 22 has extending portions 24a and 24b extending inward in the width direction at the upper and lower portions thereof, and the upper and lower portions of the opening 18 are extended from the width of the plate-like portion 22a by the extending portions 24a and 24b. Is also narrower. The spring 22 b of the intake valve 22 is fixed to the extending portion 24 b below the opening 18 and biases the plate-like portion 22 a toward the extending portion 24 a above the opening 18. Further, the opening 19 of the exhaust valve 23 has extending portions 25a and 25b whose upper and lower portions extend inward in the width direction, and the upper and lower portions of the opening 19 are formed on the plate-like portion 23a by the extending portions 25a and 25b. It is narrower than the width. The spring 23 b of the exhaust valve 23 is fixed to the extending part 25 a at the upper part of the opening 19 and urges the plate-like part 23 a toward the extending part 25 b at the lower part of the opening 19.

  When the pressure in the air storage chamber 15 is substantially the same as the pressure in the outside 16, as shown in FIG. 3A, the plate-like portion 22a of the intake valve 22 is urged by a spring 22b and abuts on the upper extension portion 24a. The upper part of the opening 18 is closed, and the intake valve 22 is closed. Further, the plate-like portion 23a of the exhaust valve 23 is urged by a spring 23b and abuts against the lower extending portion 25b to close the lower portion of the opening 19 so that the exhaust valve 23 is closed. When the ink jet recording head is not driven, the pressure in the air storage chamber 15 does not change, so both the intake valve 22 and the exhaust valve 23 are closed, and the air storage chamber 15 is in a sealed state. For this reason, even if water vapor diffuses from the common liquid chamber 14 to the air storage chamber 15 via the damper layer 8, it does not diffuse to the outside 16, thereby suppressing an increase in the viscosity of the ink in the common liquid chamber 14.

  When the damper layer 8 is deformed and the pressure of the air storage chamber 15 becomes higher than the pressure of the outside 16 as the ink jet recording head is driven, the plate-like portion 23a of the exhaust valve 23 is air-filled as shown in FIG. It is pushed by the pressure of the storage chamber 15 and is lifted and opened from the lower extending portion 25b. On the other hand, the plate-like portion 22a of the intake valve 22 is also pushed by the pressure of the air storage chamber 15, but hits the upper extending portion 24a and closes the upper portion of the opening 18, and the intake valve 22 remains closed. When the exhaust valve 23 is in an open state, air flows from the inside of the air storage chamber 15 to the outside 16 through the opening 19 (arrow A in the figure), and the pressure in the air storage chamber 15 becomes the same as the pressure of the outside 16. Become. That is, the exhaust valve 23 is opened as the ink jet recording head is driven, and the exterior 16 and the air storage chamber 15 communicate with each other. This prevents the damper layer 8 from becoming difficult to deform as the ink jet recording head is driven. The damper effect can be maintained.

In addition, it is possible to prevent the occurrence of a malfunction of the ink jet recording head with respect to a change in pressure (atmospheric pressure) of the external 16 due to the use environment.
When the usage environment is high and the pressure of the external 16 is lower than the pressure in the air storage chamber 15, the exhaust valve 23 is lifted to the external 16 side as shown in FIG. That is, the force that pushes up the exhaust valve 23 due to the weight of the exhaust valve 23, the urging force of the spring 23 b to the exhaust valve 23, and the pressure difference between the external 16 and the air storage chamber 15 is the exhaust valve 23. When the force is greater than the force that pushes down, the exhaust valve 23 opens. When the exhaust valve 23 is in an open state, air flows from the air storage chamber 15 to the outside 16 through the opening 19 (arrow A in the figure), and the pressure in the air storage chamber 15 becomes the same as the pressure of the outside 16. . As a result, it is possible to prevent the damper layer 8 from being deformed toward the common liquid chamber 14 due to the expansion of the air storage chamber 15 and the ink leaking from the nozzle 9 communicating with the common liquid chamber 14 at high altitude.

  On the other hand, when the usage environment is low and the pressure of the external 16 becomes high, as shown in FIG. 3C, the plate-like portion 22a of the intake valve 22 is pushed by the pressure of the external 16 and is more than the extension portion 24a on the upper side. Opened apart. On the other hand, the plate-like portion 23a of the exhaust valve 23 is also pressed by the pressure of the outside 16, but hits the lower extending portion 25b and closes the lower portion of the opening 19 so that the exhaust valve 23 remains closed. When the intake valve 22 is in an open state, air flows from the outside 16 into the air storage chamber 15 through the opening 18 (arrow B in the figure), and the pressure in the air storage chamber 15 becomes the same as the pressure of the outside 16. Become. Thereby, since the state which the air storage chamber 15 contracted in the lowland is eliminated, it is possible to prevent air from being entrained from the nozzle 9.

  In the configuration of FIG. 3, the two valves of the intake valve 22 and the exhaust valve 23 are opened and closed using elastic members such as springs 22b and 23b, respectively. This is advantageous in that it can cope with a wider range of pressure fluctuations as compared with the configuration shown in FIG.

Hereinafter, a specific manufacturing process of the ink jet recording head of the present embodiment will be described in detail based on examples.
<Example 1>
The individual liquid chamber substrate 2 is formed using a silicon wafer having a diameter of 6 inches. A diaphragm 3 having a three-layer structure is formed by stacking SiO ₂ 0.6 [μm], Si 1.5 [μm], and SiO ₂ 0.4 [μm] on a silicon wafer having a thickness of 600 [μm]. Formed. On the diaphragm 3, Ti 20 [nm] and Pt 200 [nm] were formed as a lower electrode (not shown) by sputtering. A 2 [μm] thick film was formed on the lower electrode by a sol-gel method using lead zirconate titanate (PZT) as an organometallic solution, and then fired at 700 ° C. to form a PZT piezoelectric film (not shown) Formed. Thereafter, Pt 200 [nm] was formed on the piezoelectric film by a sputtering method to form an upper electrode (not shown).

  After the formation of the upper electrode, the upper electrode, the piezoelectric film, and the lower electrode were patterned by a dry etching method to form the piezoelectric element 4 and the resistance temperature detector (not shown) corresponding to the individual liquid chamber 10. The arrangement pitch of the piezoelectric elements 4 was 85 [μm], and the width of the piezoelectric body was 40 [μm]. The length of the piezoelectric elements 4 in the longitudinal direction was 1000 [μm], and the number of the piezoelectric elements 4 arranged in one row was set to four rows of 300. Further, the movable part of the diaphragm 3 was not covered with the part on the partition wall of the individual liquid chamber 10. Thus, the deformation of the diaphragm 3 corresponding to the individual liquid chamber 10 is not hindered. The resistance temperature detector was formed at a position close to a connection pad (not shown) on the individual liquid chamber substrate 2. By forming it at a position close to the connection pad, it becomes possible to indicate the temperature state by the energy supplied to the ink jet recording head via the FPC (appendix), and the drive control of the piezoelectric element 4 can be performed with high accuracy. .

  Next, an interlayer insulating film (not shown) is formed by a plasma CVD method, contact holes are formed in the interlayer insulating film on the upper electrode and the lower electrode, and Ti 50 [nm] and Al 2 [μm] are sequentially formed. A wiring layer was formed by stacking and dry etching.

  Thereafter, the position corresponding to the ink supply port 11 to the individual liquid chamber 10 of the vibration plate 3 is removed by dry etching, the opening is formed, and the individual liquid chamber substrate 2 in which the actuator and the ink flow path are formed is completed. To do.

  Next, the holding substrate 6 is formed using a silicon wafer having a diameter of 6 inches. First, the silicon wafer is polished to a thickness of 400 [μm], and an oxide film or the like is formed on the individual liquid chamber substrate 2 side. Thereafter, the oxide film is patterned by photolithography so that the holding substrate recess 13 and the opening 12 are opened. Further, a resist is formed thereon, and the resist is patterned by photolithography so that only the opening 12 is opened. Then, the opening 12 is formed through the ICP etching from the individual liquid chamber substrate 2 side. Thereafter, only the resist on the individual liquid chamber substrate 2 side is removed, and half etching is performed by ICP etching using the first patterned oxide film pattern as a mask. Finally, when the oxide film is removed, the holding substrate recess 13 on the individual liquid chamber substrate 2 side and the opening 12 penetrating therethrough can be formed.

  The holding substrate 6 is manufactured as described above by applying an epoxy adhesive to the bonding surface of the holding substrate 6 thus created with a flexographic printing machine with a film thickness of 2 [μm], bonding, and curing the adhesive. The individual liquid chamber substrate 2 was joined. Thereafter, the drive IC 5 was physically and electrically bonded and mounted on the individual liquid chamber substrate 2 bonded to the holding substrate 6.

  Then, after the 600 [μm] individual liquid chamber substrate 2 was polished to 80 [μm], the individual liquid chamber 10 and the fluid resistance portion (not shown) were formed by ICP dry etching. The width of the individual liquid chamber 10 was 60 [μm], the width of the fluid resistance portion was 30 [μm], and the length was 300 [μm]. Etching of the fluid resistance portion and the individual liquid chamber 10 was performed until the diaphragm 3 was reached, and was set to the same height. The portion of the diaphragm 3 corresponding to the ink supply port 11 is etched in advance, so that a through-hole can be formed.

  After the wafer was cut into chips by dicing, the nozzle plate 1 and the individual liquid chamber substrate 2 were joined by the same method as the holding substrate 6. As the nozzle plate 1, a SUS material having a thickness of 30 [μm] formed by pressing the nozzles 9 having a diameter of 20 [μm] at a pitch of 85 [μm] was used.

  Next, the frame member 7 was formed using polyphenyl sulfide. The frame member 7 is formed by injection molding polyphenyl sulfide so as to have a space for forming the common liquid chamber 14 and the air storage chamber 15 and an opening 17 shown in FIG. Thereafter, the damper layer 8 made of silicone elastomer is formed between the common liquid chamber 14 and the air storage chamber 15 inside the frame member 7 by injection molding. As the valve 20 that enables the air storage chamber 15 and the outside 16 to communicate with each other, a valve 21 shown in FIG. 2 is formed by forming an elastic body by injection molding or the like and pushed into an opening 17 formed in the frame member 7. The frame member 7 is bonded onto the holding substrate 6.

  Further, the common liquid chamber 14 of the frame member 7 is connected to an ink tank (not shown). Further, an FPC connected to the head external circuit is bonded to the individual wiring pad portion by ACF bonding or wire bonding. By such a manufacturing process, an ink jet recording head that obtains a good damper effect of pressure fluctuations propagated into the common liquid chamber and suppresses the volatilization of moisture from the common liquid chamber and obtains a good discharge performance over a long period of time. Obtained.

<Example 2>
The second embodiment is different from the first embodiment in the configuration of the valve 20 that allows the air storage chamber 15 and the outside 16 to communicate with each other, and is otherwise the same as the first embodiment. In Example 1, when the frame member 7 is formed, injection molding is performed so as to have a space for forming the common liquid chamber 14 and the air storage chamber 15 and the openings 18 and 19 having the shape shown in FIG. Thereafter, a damper layer 8 made of silicone elastomer is formed between the common liquid chamber 14 and the air storage chamber 15 inside the frame member 7 by injection molding, and an intake valve 22 made of a plate-like portion and a spring shown in FIG. Valves 23 are formed and set in openings 18 and 19 respectively. By such a manufacturing process, an ink jet recording head that obtains a good damper effect of pressure fluctuations propagated into the common liquid chamber and suppresses the volatilization of moisture from the common liquid chamber and obtains a good discharge performance over a long period of time. Obtained.

Next, a configuration example of an ink jet recording apparatus as an example of an image forming apparatus including the droplet discharge head of the present invention according to the embodiment will be described.
FIG. 4 is a side view showing the overall configuration of an inkjet recording apparatus 201 as an example of the present embodiment. FIG. 5 is a plan view showing the main configuration of the inkjet recording apparatus 201 of FIG.
This ink jet recording apparatus 201 is a serial type ink jet recording apparatus, and a carriage 233 is slidable in a main scanning direction by a main guide rod 231 and a sub guide rod 232 which are guide members horizontally mounted on left and right side plates 221A and 221B. Hold. Then, the main scanning motor (not shown) moves and scans in the arrow direction (carriage main scanning direction) in FIG. 5 via the timing belt. The carriage 233 is provided with a recording head 234 including a droplet discharge head according to the present invention in order to discharge ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (K). Wearing.

  The recording head 234 arranges nozzle rows composed of a plurality of nozzles in the sub-scanning direction orthogonal to the main scanning direction, and directs the ink droplet ejection direction downward. The recording head 234 is configured by attaching droplet discharge heads 234a and 234b each having two nozzle rows to one base member. Then, one nozzle row of one head 234a has black (K) droplets, the other nozzle row has cyan (C) droplets, and one nozzle row of the other head 234b has magenta (M) droplets. Droplets are discharged, and the other nozzle row discharges yellow (Y) droplets. In this example, a four-color droplet is ejected with a two-head configuration, but a droplet ejection head for each color may be provided. The carriage 233 is equipped with sub tanks 235a and 235b (referred to as “sub tank 235” when not distinguished) for supplying ink of each color corresponding to the nozzle rows of the recording head 234. The sub tank 235 is supplied with ink of each color from the ink cartridge 210 of each color by the supply unit 224 via the supply tube 236 of each color.

  On the other hand, as a paper feeding unit for feeding the paper 242 stacked on the paper stacking unit (pressure plate) 241 of the paper feed tray 202, a half-moon roller (feeding) that separates and feeds the paper 242 one by one from the paper stacking unit 241. Paper roller) 243 and paper feed roller 243. A separation pad 244 made of a material having a large friction coefficient is provided, and the separation pad 244 is urged toward the paper feed roller 243 side. A sheet 242 fed from the sheet feeding unit is fed to the lower side of the recording head 234. For this purpose, a guide member 245 for guiding the paper 242, a counter roller 246, a conveyance guide member 247, and a pressing member 248 having a tip pressure roller 249 are provided. In addition, a transport belt 251 serving as a transport unit for electrostatically attracting the fed paper 242 and transporting the paper 242 at a position facing the recording head 234 is provided. The conveyor belt 251 is an endless belt, and is configured to wrap around the conveyor roller 252 and the tension roller 253 so as to circulate in the belt conveyance direction (sub-scanning direction).

  In addition, a charging roller 256 that is a charging unit for charging the surface of the transport belt 251 is provided. The charging roller 256 is disposed so as to come into contact with the surface layer of the conveyor belt 251 and to rotate following the rotation of the conveyor belt 251. The transport belt 251 rotates in the belt transport direction when the transport roller 252 is rotationally driven through timing by a sub-scanning motor (not shown). Further, as a paper discharge unit for discharging the paper 242 recorded by the recording head 234, a separation claw 261 for separating the paper 242 from the transport belt 251, a paper discharge roller 262, and a paper discharge roller 263 are provided. ing. A paper discharge tray 203 is provided below the paper discharge roller 262.

  A double-sided unit 271 is detachably attached to the back surface of the apparatus main body. The duplex unit 271 takes in the paper 242 returned by the reverse rotation of the transport belt 251, reverses it, and feeds it again between the counter roller 246 and the transport belt 251. The upper surface of the duplex unit 271 is a manual feed tray 272. Further, a maintenance / recovery mechanism 281 for maintaining and recovering the nozzle state of the recording head 234 is disposed in a non-printing area on one side in the scanning direction of the carriage 233. The maintenance / recovery mechanism 281 includes cap members (hereinafter referred to as “caps”) 282a and 282b (hereinafter referred to as “caps 282” when not distinguished) for capping each nozzle surface of the recording head 234, and nozzle surfaces. A wiper blade 283 that is a blade member for wiping the ink, and an empty discharge receiver 284 that receives liquid droplets when performing empty discharge for discharging liquid droplets that do not contribute to recording in order to discharge thickened ink. Yes.

  In addition, in the non-printing area on the other side of the carriage 233 in the scanning direction, idle ejection that receives droplets when performing idle ejection that ejects droplets that do not contribute to recording in order to discharge ink that has been thickened during recording or the like. A receptacle 288 is arranged. The idle discharge receiver 288 includes an opening 289 along the nozzle row direction of the recording head 234.

  In the image forming apparatus configured as described above, the sheets 242 are separated and fed one by one from the sheet feeding tray 202, and the sheet 242 fed substantially vertically upward is guided by the guide member 245. Then, the paper is sandwiched between the transport belt 251 and the counter roller 246 and transported. Further, the front end is guided by the transport guide 237 and pressed against the transport belt 251 by the front end pressure roller 249, and the transport direction is changed by approximately 90 °. The At this time, an alternating voltage is applied to the charging roller 256 so that a positive output and a negative output are alternately repeated. In this case, a positive voltage and a negative voltage are alternately charged in a band shape with a predetermined width in a charging voltage pattern in which the conveying belt 251 alternates, that is, in the sub-scanning direction that is the circumferential direction. When the sheet 242 is fed onto the conveyance belt 251 charged alternately with plus and minus, the sheet 242 is attracted to the conveyance belt 251, and the sheet 242 is conveyed in the sub scanning direction by the circumferential movement of the conveyance belt 251.

Therefore, by driving the recording head 234 according to the image signal while moving the carriage 233, ink droplets are ejected onto the stopped paper 242 to record one line, and after the paper 242 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 paper 242 has reached the recording area, the recording operation is finished and the paper 242 is discharged onto the paper discharge tray 203.

  As described above, since the inkjet recording apparatus 201 includes the droplet discharge head according to the present invention as a recording head, it is possible to perform highly reliable and stable droplet discharge, high speed, and high printing uniformity. A quality image can be formed.

  Next, another configuration example of the ink jet recording apparatus as an example of an image forming apparatus including the droplet discharge head of the present invention according to the embodiment will be described. FIG. 6 is a side view showing the overall configuration of an inkjet recording apparatus 401 of another example of the present embodiment. The ink jet recording apparatus 401 is a line type ink jet recording apparatus, and has an image forming unit 402 and the like inside the apparatus main body 401, and a large number of recording media (sheets) 403 can be stacked on the lower side of the apparatus main body 401. A paper feed tray 404 is provided. A sheet 403 fed from the sheet feeding tray 404 is taken in, and a required image is recorded by the image forming unit 402 while the sheet 403 is conveyed by the conveying mechanism 405. Thereafter, the paper 403 is discharged onto a paper discharge tray 406 attached to the side of the apparatus main body 401. In addition, a duplex unit 407 that can be attached to and detached from the apparatus main body 401 is provided. When performing double-sided printing, after the one-side (front) printing is completed, the paper 403 is taken into the double-sided unit 407 while being conveyed in the reverse direction by the conveyance mechanism 405. Then, the paper is reversed and sent to the transport mechanism 405 again with the other side (back side) as the printable side. After the other side (back side) printing is completed, the paper 403 is discharged to the paper discharge tray 406. Here, the image forming unit 402 is, for example, four full-line type droplet discharge heads that discharge droplets of each color of black (K), cyan (C), magenta (M), and yellow (Y). The recording heads 411k, 411c, 411m, and 411y are provided. When the colors of the recording heads 411k, 411c, 411m, and 411y are not distinguished, they are hereinafter referred to as “recording head 411”. Each recording head 411 is mounted on the head holder 413 with the nozzle surface on which nozzles for discharging droplets are formed facing downward.

  Also, a maintenance / recovery mechanism 412k, 412c, 412m, 412y for maintaining and recovering the performance of the recording head is provided corresponding to each recording head 411. When the colors of the maintenance / recovery mechanisms 412k, 412c, 412m, and 412y are not distinguished, they are hereinafter referred to as “a maintenance / recovery mechanism 412”. During the head performance maintenance operation such as purge processing and wiping processing, the recording head 411 and the maintenance / recovery mechanism 412 are relatively moved so that the capping member constituting the maintenance / recovery mechanism 412 faces the nozzle surface of the recording head 411. Let Here, the recording head 411 is arranged to eject droplets of each color in the order of blank, cyan, magenta, and yellow from the upstream side in the paper conveyance direction, but the arrangement and the number of colors are not limited to this.

  Further, as the line-type recording head, one or a plurality of recording heads provided with a plurality of nozzle rows that discharge droplets of each color at a predetermined interval may be used. Further, the recording head and the recording liquid cartridge that supplies ink to the recording head can be integrated or separated. The sheets 403 in the sheet feed tray 404 are separated one by one by a sheet feed roller (half-moon roller) 421 and a separation pad (not shown) and fed into the apparatus main body 401. Then, the sheet is fed between the registration roller 425 and the conveyance belt 433 along the guide surface 423a of the conveyance guide member 423, and is conveyed to the conveyance belt 433 of the conveyance mechanism 405 through the guide member 426 at a predetermined timing.

  In addition, the conveyance guide member 423 is also formed with a guide surface 423 b for guiding the paper 403 sent out from the duplex unit 407. Further, a guide member 427 for guiding the sheet 403 returned from the transport mechanism 405 to the duplex unit 407 during duplex printing is also provided. The transport mechanism 405 includes a transport belt 433, a charging roller 434, a platen member 435, and a pressing roller 436. The conveyance belt 433 is an endless conveyance belt that is stretched between a conveyance roller 431 that is a driving roller and a driven roller 432. The charging roller 434 is a charging roller for charging the conveyance belt 433. The platen member 435 is a member that maintains the flatness of the transport belt 433 at a portion facing the image forming unit 402. The holding roller 436 presses the sheet 403 fed from the conveying belt 433 against the conveying roller 431 side. Although not shown in the drawings, a cleaning roller made of a porous material or the like, which is a cleaning means for removing ink attached to the conveyance belt 433, is also provided. On the downstream side of the transport mechanism 405, a paper discharge roller 438 and a spur 439 for sending the paper 403 on which an image is recorded to the paper discharge tray 406 are provided.

  In the image forming apparatus configured as described above, the transport belt 433 moves in the direction indicated by the arrow and is charged by coming into contact with the charging roller 434 to which a high potential applied voltage is applied. When the paper 403 is fed onto the conveyance belt 433 charged to this high potential, the paper 403 is electrostatically attracted to the conveyance belt 433. In this way, the sheet 403 that is strongly adsorbed to the transport belt 433 is calibrated for warpage and unevenness, and forms a highly flat surface. Then, the sheet 403 is moved around the conveyor belt 433, and droplets are ejected from the recording head 411. As a result, a required image is formed on the sheet 403, and the sheet 403 on which the image is recorded is discharged to the discharge tray 406 by the discharge roller 438.

  As described above, since the inkjet recording apparatus 401 includes the droplet ejection head according to the present embodiment as a recording head, it is possible to perform highly reliable and stable droplet ejection, and a high-quality image without print unevenness. Can be formed.

  In the above-described embodiment, the liquid droplet ejection head according to the present invention has been described using an example in which the liquid droplet ejection head is applied to a recording head that ejects ink droplets of an ink jet recording apparatus. The present invention is not limited to this, and the present invention can also be applied to liquid droplets other than ink, for example, a droplet discharge head that discharges a liquid resist for patterning, and a droplet discharge head that discharges a gene analysis sample.

  Further, in the above description, a piezoelectric actuator method using the piezoelectric element 4 is employed as pressure generating means for generating pressure fluctuations in the individual liquid chamber 10 and ejecting ink droplets from the nozzles 9. However, the present invention is not limited to this, and an electrostatic actuator method or a thermal method in which bubbles are generated in the individual liquid chamber 10 using a heater or the like, and the individual liquid chamber is pressurized to eject ink droplets from the nozzles is used. It can also be applied to a droplet discharge head.

What has been described above is merely an example, and the present invention has specific effects for each of the following modes.
(Aspect A)
A plurality of nozzles 9 for discharging droplets of ink or the like, a plurality of individual liquid chambers 10 communicating with the nozzles, a common liquid chamber 14 communicating with the plurality of individual liquid chambers, and a pressure for boosting the individual liquid chamber An actuator such as the piezoelectric element 4, a flexible member such as a damper layer 8 that forms at least a part of the common liquid chamber, and an air storage chamber 15 provided to face the common liquid chamber via the flexible member. A droplet discharge head such as an inkjet recording head. This droplet discharge head includes a valve 20 that enables communication between the air storage chamber 15 and the outside 16.

  In (Aspect A), when the pressure of the air storage chamber facing the common liquid chamber via the flexible member fluctuates, the valve is opened to connect the air storage chamber and the outside, and the air storage chamber portion is Keep the same pressure as the outside. Thereby, it is suppressed that a flexible member becomes difficult to deform | transform into the air storage chamber side by the pressure fluctuation of an air storage chamber, and a favorable damper effect is maintained. Other than this, the valve is closed and the air storage chamber is shut off from the outside to be in a sealed state. For this reason, even if water vapor diffuses from the common liquid chamber to the air storage chamber via the flexible member, it does not diffuse to the outside, so that an increase in the viscosity of the ink in the common liquid chamber can be suppressed.

(Aspect B)
In (Aspect A), the valve can be opened and closed in conjunction with the pressure difference between the air storage chamber and the outside. According to this, compared with the structure which opens and closes a valve using the pump described in the liquid discharge head of patent document 3, there exists an effect that a valve can be opened and closed with a simple structure. Further, since the valve can be opened and closed in conjunction with the pressure difference between the air storage chamber and the outside, as described in the above embodiment, the occurrence of a malfunction of the ink jet recording head due to a change in external pressure (atmospheric pressure) due to the use environment Can also be prevented. Specifically, when the usage environment is high and the external pressure is lower than the pressure in the air storage chamber, the valve opens and air flows from the air storage chamber to the outside so that the air storage chamber and the outside are at the same pressure. The problem that ink leaks from the nozzle can be prevented. On the other hand, if the usage environment is low and the external pressure is higher than the pressure in the air storage chamber, the valve opens and air flows from the outside to the air storage chamber, so that the air storage chamber and the outside have the same pressure, and the nozzle in the low ground The problem of entraining air can be prevented.

(Aspect C)
In (Aspect A) or (Aspect B), the valve 21 has a closing portion such as a plate-like portion 21a that closes the opening 17 that communicates with the outside provided in the air storage chamber, and the weight of the valve, the air storage chamber, According to the relationship with the pressure difference with the outside, the opening is opened and closed by moving the closing portion. According to this, as described above with reference to FIG. 2, it is possible to realize a valve capable of maintaining a good damper effect and suppressing the increase in the viscosity of the ink in the common liquid chamber.

(Aspect D)
In (Aspect A) or (Aspect B), the valve such as the exhaust valve 23 biases the closed part such as a plate-like part 23a that closes the opening 19 that communicates with the outside provided in the air storage chamber. An elastic member such as a spring 23b is provided, and the opening 19 is opened and closed by moving the closing portion according to the relationship between the weight of the valve, the urging force of the elastic member, and the pressure difference between the air storage chamber and the outside. . According to this, as described with reference to FIG. 3, it is possible to realize a valve that can maintain a good damper effect and can suppress the increase in viscosity of the ink in the common liquid chamber and the effect.

(Aspect E)
In (Aspect D), the valve includes an exhaust valve 23 that exhausts air from the air storage chamber to the outside, and an intake valve 22 that intakes air from the outside into the air storage chamber. According to this, since the two valves of the intake valve and the exhaust valve are opened and closed using the self-weight of the valve, the pressure difference, and the biasing force of the elastic member, respectively, the self-weight of the valve and the pressure difference Compared to the configuration in which one valve opens and closes (Aspect C), there is a merit that it can cope with a wider range of pressure fluctuations.

(Aspect F)
An image forming apparatus such as an ink jet recording apparatus provided with the liquid droplet ejection head according to any one of (Aspect A) to (Aspect E). According to this, a good image can be obtained over a long period of time.

1 Nozzle plate 2 Individual liquid chamber substrate 3 Vibration plate 4 Piezoelectric element 5 Drive IC
6 Holding substrate 7 Frame member 8 Damper layer 9 Nozzle 10 Individual liquid chamber 11 Ink supply port 12 Opening portion 13 Holding substrate recessed portion 14 Common liquid chamber 15 Air storage chamber 16 External 17, 18, 19 Open 20, 21 Valve 21a, 21b Plate -Shaped part 21b Bar-shaped part 22 Intake valve 22a Plate-like part 22b Spring 23 Exhaust valve 22a Plate-like part 22b Spring 24a, 24b Extending part (intake valve)
25a, 25b Extension part (exhaust valve)
201 Inkjet recording device (serial type)
401 Inkjet recording device (line type)

Japanese Patent No. 428545 JP 2002-103608 A JP 2012-210769 A

Claims (6)

A plurality of nozzles for discharging droplets, a plurality of individual liquid chambers communicating with the nozzles, a common liquid chamber communicating with the plurality of individual liquid chambers, and an actuator for boosting the individual liquid chambers; In a liquid droplet ejection head comprising: a flexible member that forms at least a part of the common liquid chamber; and an air storage chamber that is provided to face the common liquid chamber via the flexible member.
A droplet discharge head, comprising: a valve that enables communication between the air storage chamber and the outside.   2. The droplet discharge head according to claim 1, wherein the valve can be opened and closed in conjunction with a pressure difference between the air storage chamber and the outside.   3. The droplet discharge head according to claim 1, wherein the valve has a closing portion that closes an opening that communicates with the outside provided in the air storage chamber, and that the self-weight of the valve, the air storage chamber, and the outside A droplet discharge head configured to open and close the opening by moving the closing portion in accordance with a pressure difference.   3. The droplet discharge head according to claim 1, wherein the valve includes a closing portion that closes an opening that communicates with the outside provided in the air storage chamber, and an elastic member that biases the closing portion. The droplet discharge unit is configured such that the closed portion moves and opens and closes the opening according to the relationship between the weight of the elastic member, the biasing force of the elastic member, and the pressure difference between the air storage chamber and the outside. head.   5. The droplet discharge head according to claim 4, wherein the valve includes a valve that exhausts air from the air storage chamber to the outside, and a valve that sucks air from the outside into the air storage chamber.   An image forming apparatus comprising the droplet discharge head according to claim 1.

Images