JP2014051079A - Droplet discharge head, head cartridge, and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a droplet discharge head which stably supplies a liquid in which foreign objects are not mixed and quickly damps excessive pressure waves for realizing a droplet discharge head achieving high image quality, high speed, and high quality, and to provide an image formation device including the droplet discharge head.SOLUTION: A droplet discharge head 4 includes: a nozzle plate 2 having multiple nozzles 2a; a liquid chamber 1a with which each nozzle communicates; a passage plate 1 having a fluid resistor 1b; driving means 5 pressurizing a liquid in the liquid chamber; a diaphragm 3 having a supply port 3d for supplying the liquid to the liquid chamber; a frame 7 having a common liquid chamber 1c for storing the liquid; and a filter 3f provided at the supply port between the common liquid chamber and the diaphragm and having multiple holes. The supply port is provided at a passage excluding the liquid chamber and the fluid resistor, and a thin film part 1e is formed at the passage plate facing the supply port. A recessed part 2b which avoids the contact with the thin film part is formed at the nozzle plate facing the thin film part.

Description

  The present invention relates to a droplet discharge head that discharges droplets from nozzles by displacing a diaphragm by a driving unit mainly composed of piezoelectric elements, and an image forming apparatus including the droplet discharge head.

  In general, an inkjet head as a droplet ejection head in an inkjet recording apparatus used as an image forming apparatus such as a copying machine, a facsimile machine, a printer, or a plotter is connected to a nozzle that ejects ink droplets that are droplets. A discharge chamber (also referred to as a pressure chamber, a pressurized liquid chamber, a liquid chamber, an ink chamber, an ink flow path, etc.) and an actuator means (energy generating means) that generates energy for pressurizing ink in the discharge chamber. The actuator means is used to pressurize the ink in the ejection chamber and eject ink droplets from the nozzles. The ink-on-demand system, which ejects ink droplets only when recording is required, is the mainstream. is there.

  Such ink jet heads are roughly classified into several types according to the type of actuator means for ejecting ink droplets (recording droplets). A part of the wall of the liquid chamber is made into a thin diaphragm, and a piezoelectric element as an electromechanical conversion element is arranged corresponding to the thin diaphragm, and the diaphragm is deformed by deformation of the piezoelectric element generated by voltage application. Piezo type that discharges ink droplets by changing the pressure in the chamber, inkjet type that arranges heating element inside the liquid chamber, generates bubbles by heating the heating element by energization, and discharges ink droplets by the pressure of the bubbles This is disclosed in, for example, “Patent Document 1”.

  In addition, a vibration plate that forms a wall surface of the liquid chamber and an individual electrode outside the liquid chamber that is disposed to face the vibration plate, and an electrostatic force that is generated by applying an electric field between the vibration plate and the electrode. For example, “Patent Document 2” discloses an electrostatic type in which an ink droplet is ejected from a nozzle by deforming a diaphragm and changing a pressure volume ratio in a liquid chamber.

  In recent years, there is a tendency to use a multi-nozzle head having a plurality of nozzles in order to increase the image quality, and to further reduce the size of the liquid chamber in order to reduce the size of the droplets. In order to make the nozzle pitch fine, it is necessary to shorten not only the width direction of the liquid chamber but also the length direction. This is because small droplets are ejected by increasing the pressure resonance frequency of the liquid chamber.

  In addition, even if the liquid chamber is made small, the drive energy from the actuator element is sufficiently transmitted to the liquid chamber, and the drive energy is not transmitted to the partition walls separating the plurality of liquid chambers. There is. Furthermore, it is necessary to make the characteristics of the liquid droplets discharged from each nozzle uniform, and it is important that there is no difference in the volume and resistance of the liquid chamber between the heads. Is mandatory.

  In addition, it is required to perform continuous discharge because of the demand for high speed, and the pressure wave generated to discharge the droplets must be quickly attenuated after the discharge. However, the pressure wave generated to discharge the droplets by making the liquid chamber small is not easily attenuated, and it is necessary to provide a mechanism for damping the pressure wave, and it is difficult to downsize the area other than the liquid chamber It becomes.

  Furthermore, it can be said that factors other than the liquid chamber structure, such as ink viscosity, bubbles, and foreign matter, have a great influence on the ejection characteristics due to the demand for higher image quality. Among these, regarding the ink viscosity, there is a configuration in which a heat source is mounted on the inkjet head in order to manage the temperature of the ink, for example, a configuration in which the supply amount is adjusted by the ink temperature as disclosed in “Patent Document 3”. With respect to the bubbles, for example, as disclosed in “Patent Document 4”, there is a configuration in which a space for trapping bubbles is provided in the liquid chamber.

  However, with respect to the foreign matter, the above-described configuration has no effect at all. For example, as disclosed in “Patent Document 5”, there is a configuration in which a filter is formed at the diaphragm supply port. As a result, the ejection failure due to the foreign matter is reduced after the head is completed. However, if the filter is clogged with the foreign matter, the amount of liquid supply becomes insufficient, and the ejection failure occurs. In addition, if the filter diameter is reduced to remove even small foreign matter, there is a problem that the amount of liquid supplied to the liquid chamber becomes insufficient due to the resistance of the filter.

  The present invention solves the above-mentioned problems, and stably supplies a liquid free of foreign matter and quickly attenuates excess pressure waves in order to realize a high-quality, high-speed and high-quality liquid droplet ejection head. It is an object of the present invention to provide a droplet discharge head that can be used and an image forming apparatus including the same.

  The invention according to claim 1 is formed in a nozzle plate having a plurality of nozzles that discharge liquid as droplets, a liquid chamber that stores the liquid and that communicates with each nozzle, and a flow path that allows the liquid to flow to the liquid chamber. A flow path plate having fluid resistance, driving means for generating pressure to pressurize the liquid in the liquid chamber, and supplying at least one wall surface of the liquid chamber to supply the liquid to the liquid chamber A diaphragm having a supply port, a frame having a common liquid chamber for storing the liquid until it flows into the liquid chamber, and a plurality of holes provided in the supply port between the common liquid chamber and the vibration plate In the liquid droplet ejection head having a filter having a portion, the supply port is provided in the flow path excluding the liquid chamber and the fluid resistance, and a thin film portion is formed in the flow path plate facing the supply port. The nozzle facing the thin film portion Wherein the recess for avoiding contact with the thin film portion is formed on.

  According to the present invention, the filter is formed almost in the entire area of the supply port facing the common liquid chamber, so that the liquid does not run out even when the diameter of the hole of the filter is made smaller than the diameter of the nozzle. Can be supplied. In addition, the residual pressure vibration of the pressure generated to discharge the liquid from the nozzle is attenuated in a region surrounded by the thin film portion, the fluid resistance portion, and the filter resistance provided on the nozzle plate and the channel plate, thereby Thus, the next droplet can be discharged. In addition, since the pressure vibration is individually attenuated by the recess communicating with each nozzle, the residual pressure vibration does not affect the other nozzles and the liquid chamber, and the discharge quality can be improved.

It is the schematic of the droplet discharge head which can apply one Embodiment of this invention. It is a principal part schematic of the droplet discharge head which can apply one Embodiment of this invention. It is a principal part schematic of the droplet discharge head which can apply one Embodiment of this invention. It is a principal part schematic of the droplet discharge head which can apply one Embodiment of this invention. It is the schematic explaining the electroforming process of the two-layer diaphragm by the nickel electroforming used for one Embodiment of this invention. It is the schematic of the droplet discharge head used for the 1st Embodiment of this invention. It is a principal part schematic of the droplet discharge head used for the 1st Embodiment of this invention. It is the schematic of the nozzle plate used for the 1st Embodiment of this invention. It is the schematic of the flow-path board used for the 1st Embodiment of this invention. It is the schematic of the diaphragm used for the 1st Embodiment of this invention. It is the schematic of the nozzle plate used for the modification of the 1st Embodiment of this invention. It is the schematic of the flow-path board used for the 2nd Embodiment of this invention. It is the schematic of the flow-path board used for the 3rd Embodiment of this invention. It is the schematic of the flow-path board used for the modification of the 3rd Embodiment of this invention. 1 is a schematic view of an edge shooter type droplet discharge head used in an embodiment of the present invention. FIG. 1 is a schematic diagram of a side shooter type droplet discharge head used in an embodiment of the present invention. FIG. 1 is a schematic front view of an image forming apparatus to which an embodiment of the present invention can be applied. 1 is a plan view of a main part of an image forming apparatus to which an embodiment of the present invention can be applied.

  The present invention includes a printer, a copier, a facsimile having a communication system, and a printing unit that perform recording on a recording medium made of paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, and the like. The present invention can be applied to a device such as a word processor, and further to an industrial recording device combined with various processing devices. The recording in the present invention includes not only giving an image having a meaning such as a character or a figure to a recording medium but also giving an image having no meaning such as a pattern to the recording medium. . Embodiments of the present invention will be described below.

  FIG. 1 is a cross-sectional view taken along the liquid chamber major axis direction (direction intersecting the nozzle arrangement direction) of a droplet discharge head using a piezoelectric element as a driving means, and FIGS. It is sectional drawing which follows. In the present embodiment, the description will be made centering on the minor axis direction of the liquid chamber, and the description will be made centering on the fact that the bonding surface is flat. Also good. Although not shown in each drawing, each joining surface is joined by an adhesive, and the coating thickness of the adhesive is about 0.4 to 10 μm.

  A droplet discharge head 4 shown in FIG. 1 includes a flow channel plate 1 as a liquid chamber substrate that forms a liquid chamber 1a and a fluid resistance portion 1b, and a nozzle 2a that discharges a droplet bonded to the upper surface of the flow channel plate 1. , A diaphragm 3 bonded to the lower surface of the flow path plate 1 and having a thin portion 3a, and a laminated piezoelectric element 5 bonded to the diaphragm 3 as a driving means for changing the internal pressure of the liquid chamber 1a. And a base substrate 6 to which the laminated piezoelectric element 5 is fixed. In FIG. 1, the adhesive layer is not shown because it is thinner than other members, and the diaphragm 3 has three layers as shown in FIG. 2, as shown in FIG. You may use what has the convex part 3b of two layers, and the thick part 3c.

  In the present embodiment, the laminated piezoelectric element 5 is formed by alternately laminating piezoelectric material layers and internal electrodes, and is configured to pressurize the liquid in the liquid chamber 1a using a vertical displacement as the piezoelectric direction. . Further, in the present embodiment, the laminated piezoelectric element 5 as shown in FIG. 2 is divided into comb teeth by half-cut dicing, and alternately used as the piezoelectric element driving unit 5a and the supporting unit (non-driving unit) 5b. This structure is called a bi-pitch structure. Since the flow path unit is supported by the support portion 5b, it is very effective in preventing the flow path plate 1 from being lifted by the pressure increase in the liquid chamber 1a and suppressing so-called mutual interference. In addition, the piezoelectric element driving portion 5a of the laminated piezoelectric element 5 having a higher density of the liquid chamber 1a as shown in FIG. 4 is set at the same interval as the nozzle pitch and does not form the support portion 5b (normal pitch structure). May be.

  Examples of the material of the flow path plate 1 include silicon, nickel, 42 alloy, SUS304, and other stainless steel materials. A liquid-resistant thin film made of a silicon oxide film, a titanium nitride film, or an organic resin film such as a metal film or polyimide may be formed on the surface of the flow path plate 1 in contact with the liquid. By forming such a liquid-resistant thin film, the flow path plate material is less likely to elute from the liquid, and the wettability is also improved, so that bubbles do not easily stay and stable droplet discharge is possible. The layers and films in the present invention include all structures that are substantially flat.

  In the configuration shown in FIGS. 1 and 2, the flow path plate 1 has a thickness of 40 to 600 μm (the liquid chamber 1a may be formed by laminating the flow path plates 1), and the longitudinal length of the liquid chamber 1a. 400 to 1600 μm and the width of the liquid chamber 1 a is 120 to 130 μm. The width of the flow path partition is about 15 to 50 μm (liquid chamber pitch 150 dpi) at the joint surface with the diaphragm 3. As shown in FIG. 4, the thickness of the flow channel plate 1 is 100 to 600 μm (the liquid chamber 1 a can be formed by laminating the flow channel plates 1), and the longitudinal length 400 to 400 of the liquid chamber 1 a. The width may be 1200 μm and the width of the liquid chamber 1a may be 50 to 70 μm (because the liquid chamber pitch is 300 dpi).

  The nozzle plate 2 is formed of a metal material, for example, a nickel plating film by an electroforming method, and has a number of nozzles 2a that are fine discharge ports for causing droplets to fly. The internal shape (inner side shape) of the nozzle 2a is a horn shape (may be a substantially cylindrical shape or a substantially truncated cone shape), and its diameter is about 15 to 35 μm on the droplet discharge side. In the present embodiment, the nozzle 2a has a diameter of 18 to 24 μm, and the nozzle pitch of each row is 150 dpi / 300 dpi. Further, a resin material may be used as the nozzle plate 2.

  On the liquid discharge surface (nozzle surface side) of the nozzle plate 2, a water repellent treatment layer 2 d (see FIG. 2) subjected to a water repellent surface treatment is provided. Liquid physical properties, such as tetrafluoroethylene nickel eutectoid plating, electrodeposition coating of fluororesin, evaporative fluororesin, such as vapor-deposited fluoride pitch, and baking after solvent coating of silicon resin and fluororesin The water-repellent treatment layer 2d selected according to the above is provided to stabilize the liquid droplet shape and flight characteristics and to obtain high-quality image quality.

  The frame 7 in which the engraving that becomes the supply port 3d for supplying the liquid from the outside and the common liquid chamber 1c is formed is formed by injection molding of epoxy resin. The resin material may be polyphenylene sulfide or the like.

  In the droplet discharge head 4 configured as described above, a drive waveform (pulse voltage of 10 to 50 V) is applied to the piezoelectric element driving unit 5a in accordance with the recording signal, thereby causing the piezoelectric element driving unit 5a to move in the stacking direction. Displacement occurs, the liquid chamber 1a is pressurized through the diaphragm 3, the pressure rises, and droplets are ejected from the nozzle 2a. Thereafter, the liquid pressure in the liquid chamber 1a decreases with the end of the droplet discharge, and a negative pressure is generated in the liquid chamber 1a due to the inertia of the liquid flow and the discharge process of the driving pulse, and the liquid filling process is started. Transition. At this time, the liquid supplied from the liquid tank flows into the common liquid chamber 1c, and is filled into the liquid chamber 1a from the common liquid chamber 1c via the supply port 3d through the fluid resistance portion 1b.

  The fluid resistance portion 1b is effective in attenuating residual pressure vibration after ejection, but has resistance against refilling (refilling) due to surface tension. By appropriately selecting the fluid resistance portion 1b, it is possible to balance the attenuation of the residual pressure and the refill time, and to shorten the time (drive cycle) until shifting to the next droplet discharge operation. Further, in order to attenuate the residual pressure, the driving period can be further shortened by providing the damper 3 with a damping function on the diaphragm 3.

  In the above-described configuration, as the shapes of the convex portion 3b and the thick portion 3c, there is a configuration in which the periphery of the convex portion 3b is surrounded by the thin portion 3a and the periphery is surrounded by the thick portion 3c. As this forming method, there is a method of stacking two nickel plating films by an electroforming method, and protrusions such as ribs may be formed by this electroforming method.

  Here, the electroforming process of the two-layer diaphragm by nickel electroforming will be described with reference to FIG. As shown in FIG. 5A, the first layer 212 for forming the thin portion 208 is formed on the electroformed support substrate 211. As shown in FIG. A resist pattern 214 to be the window 213 is formed and nickel electroforming is performed. As a result, as shown in FIG. 5C, nickel is deposited and deposited on the first layer 212 to form a nickel layer 215. Further, by continuing electroforming, as shown in FIG. A nickel layer 215 grows until it protrudes from the window 213. Then, the overhang portion 215a is formed by enlarging in the surface direction of the resist pattern 214 due to the edge effect. If this process is continued, as shown in FIG. 5E, the nickel layer 215 further expands in the thickness direction and the planar direction, and the resist pattern 214 is removed after the electroforming is completed in a predetermined growth process. As a result, as shown in FIG. 5 (f), a diaphragm having an island-shaped thick portion 206 having a bowl-shaped cross section surrounded by the recess 216 is obtained.

  Moreover, as the diaphragm 3, the structure which has a metal layer and a resin layer can be considered. As a member constituting the metal layer, nickel, 42 alloy, and SUS304 are conceivable. By forming a metal film such as silicon oxide or titanium on the surface, there is no need to worry about moisture permeation of the liquid. When the diaphragm 3 is a resin layer, the rigidity of the thin portion 3a is lower than that of the metal layer, so that the displacement efficiency of the laminated piezoelectric element 5 is not hindered. Moreover, when the flow path plate 1 is a metal, the bonding strength between the resin layer and the metal is enhanced as compared with the bonding between the metals. The resin layer may be a rolled film, which can provide a highly reliable product with almost no defects such as pinholes even when the thickness is reduced.

  In the present embodiment, a treatment showing affinity for the adhesive, such as forming a hydroxyl group or a silicon oxide thin film layer, may be performed in the bonding region between the vibration plate 3 and the laminated piezoelectric element 5 as the driving means. Conceivable. The silicon oxide thin film layer is formed by a method in which film formation can be performed at a temperature within a range in which heat is not relatively applied, that is, no thermal influence is generated on the diaphragm 3. Specifically, sputtering, ion beam vapor deposition, ion plating, CVD (chemical vapor deposition), P-CVD (plasma vapor deposition) and the like are suitable. In the present embodiment, the silicon oxide film is generated by oxidizing the sputtered film after sputtering of silicon. It is advantageous from the viewpoint of process time and material cost that the silicon oxide film has a minimum necessary thickness within a range in which adhesion can be secured. In this embodiment, the thickness of the silicon oxide film is used in the range of 10 to 2000 mm.

  In the water repellent treatment of this embodiment, the water repellent film is formed by a known method such as a plating film or a water repellent coating. As a water repellent treatment method, a spin coater, a roll coater, a screen printing, a spray coater, or the like can be used. In addition, a method of forming a film by vacuum deposition is also used. According to this method, the adhesion of the water repellent film is improved. In the present embodiment, the thickness of the thin part is 2 to 10 μm, and the length of the thin part region in the liquid chamber short direction is 10 to 50 μm.

  In this embodiment, polyphenylene sulfide (PPS) resin is used as the resin layer. However, other polymer materials that can be stretched, such as polyimide (PI) resin, polyetherimide (PEI) resin, polyamideimide (PAI) resin, are used. , Polybalavanic acid (PPA) resin, polysulfone (PSF) resin, polyethersulfone (PES) resin, polyetherketone (PEK) resin, polyetheretherketone (PEEK) resin, polyolefin (APO) resin, polyethylene naphthalate ( PEN) resin, aramid resin, polypropylene resin, vinylidene chloride resin, polycarbonate resin, or the like may be used.

  6 to 10 show a first embodiment in which the features of the present invention are employed. In FIG. 6, the supply port 3d of the diaphragm 3 is provided with a filter 3f having a plurality of holes for removing foreign substances. The diameter of the hole of the filter 3f is about 5 to 20 μm, and is formed to be smaller than the diameter of the nozzle 2a. In the present embodiment, with respect to the supply port 3d formed in the diaphragm 3, almost the entire region facing the common liquid chamber 1c is set as a region where the filter 3f is provided. Here, the filter 3f may be provided with a region for blocking the flow of the adhesive.

  On the wall surface of the flow path plate 1 on the nozzle plate 2 side facing the filter 3f, there are provided a damper chamber 1d engraved to give a damper function and a liquid chamber damper 1e as a thin film portion subjected to a thinning process. It has been. Further, the nozzle plate 2 facing the liquid chamber damper 1e is provided with a damper air chamber 2b which is a space for flowing air as a recess for avoiding contact with the liquid chamber damper 1e. Examples of the method for reducing the thickness of the flow path plate 1 and the method for forming the damper air chamber 2b in the nozzle plate 2 include an etching method.

  With the above-described configuration, the filter 3f is formed over almost the entire area of the supply port 3d facing the common liquid chamber 1c, so that the liquid is insufficient even when the diameter of the hole of the filter is smaller than the diameter of the nozzle 2a. Can be supplied without. Further, the residual pressure vibration generated to discharge the liquid from the nozzle 2a is surrounded by the filter resistance of the liquid chamber damper 1e, the fluid resistance portion 1b, and the filter 3f provided in the nozzle plate 2 and the flow path plate 1. By attenuating in the region, the next droplet can be ejected in a short time. Further, since the pressure vibration is individually attenuated by the damper air chamber 2b communicating with each nozzle 2a, the residual pressure vibration does not affect the other nozzles 2a and the liquid chamber 1a, and the discharge quality can be improved. Furthermore, since the supply port 3d can be closed by the filter 3f so that foreign matter does not enter the liquid chamber 1a at the initial stage of manufacturing the droplet discharge head 4, the yield of the droplet discharge head can be improved. A high-quality and high-speed droplet discharge head can be provided at low cost.

  FIG. 7A shows a state in which the droplet discharge head 4 is superposed on the nozzle plate 2, the flow path plate 1, and the vibration plate 3 from above, and FIG. 7B shows a state 1 in FIG. FIG. 7C shows a cross section of the damper chamber 1d and the damper air chamber 2b, which are 2-2 cross sections of FIG. 7A, respectively. FIG. 8 shows the nozzle plate 2, and a damper air chamber 2b which is a space corresponding to the nozzle 2a is formed in the nozzle plate 2. The damper air chamber 2b communicates with the outside via the damper air passage 2c, and the liquid residual pressure vibration in the damper air chamber 2b is attenuated by the air in and out of the damper air chamber 2b. Note that a highly viscous gel or the like may be enclosed in the damper air chamber 2b. In this case, the damper air passage 2c may not communicate with the outside.

  FIG. 11 shows a modification of the damper air passage. The damper air passage 2e shown in this modification is formed separately from the damper air chamber 2b provided corresponding to the nozzle 2a, so that it is less susceptible to the influence of pressure vibration of another channel. It is configured.

  FIG. 9 shows the flow path plate 1, and the flow path plate 1 has three areas: a liquid chamber 1a area, a fluid resistance portion 1b area, and a damper chamber 1d area. As a method of forming the flow path plate 1, the liquid chamber 1a region and the fluid resistance portion 1b region include mechanical processing such as press processing and etching processing, and the damper chamber 1d region is half-etched by etching processing to form a thin film region. The method of doing is mentioned. In the present embodiment, a thin film having a thickness of 1 to 20 μm is considered.

  FIG. 10A shows the diaphragm 3. In the present embodiment, the hole is formed over the entire area of the filter 3f region. However, the outer periphery of the filter 3f region has a hole so that the hole of the filter 3f is not clogged due to the flow of adhesive or the like. There may be no area. As this area | region, 5-50 micrometers is preferable.

  10B and 10C show the hole shape of the filter 3f. FIG. 10B shows a straight type A, and even such a hole shape sufficiently serves as a filter. FIG. 10C shows a tapered type B whose diameter gradually decreases from the common liquid chamber 1c side to the damper chamber 1d side in the thickness direction, that is, from the inner side to the outer side. In the flow of liquid from the common liquid chamber 1c side to the damper chamber 1d side, foreign matter can be caught by the filter 3f, and in the flow of liquid from the damper chamber 1d side to the common liquid chamber 1c side, the hole diameter on the damper chamber 1d side is small. As a result, the fluid resistance of the filter 3f is high, and the effect of attenuating the residual pressure can be improved. Thereby, a high-quality and long-life droplet discharge head can be provided.

  FIG. 12 shows a flow path plate used in the second embodiment of the present invention. This flow path plate 1A is the same as the flow path plate 1 except that the film thickness of the liquid chamber damper 1e in the damper chamber 1d region is different. In the flow path plate 1A, the film thickness of the liquid chamber damper 1e is not constant, and the thinnest layer 1f that is a further thinned portion with a width of about 5 to 20 μm is formed along the wall surface forming the damper chamber 1d. Has been. The thinnest lower layer 1f is formed so that its thickness is about 5 to 15 μm thinner than the liquid chamber damper 1e. With this configuration, by providing the damper film 1d with the thinnest lower layer 1f that is easily deformable, the efficiency of damping the residual pressure vibration is improved, and the residual pressure vibration can be damped more quickly.

  FIG. 13 shows a flow path plate used in the third embodiment of the present invention, and FIG. 14 shows a flow path plate used in a modification of the third embodiment of the present invention. Compared with the above-described flow path plate 1A, the flow path plate 1B shown in FIG. 13 includes not only the thinnest lower layer 1f formed along the wall surface forming the damper chamber 1d, but also two liquid chamber dampers 1e. It is different in that it is also formed so as to be divided. Further, the flow path plate 1C shown in FIG. 14 is formed so that the thinnest lower layer 1f is formed along the wall surface forming the damper chamber 1d, and the liquid chamber damper 1e is divided into a plurality of three or more. Yes. According to this configuration, since the liquid chamber damper 1e and the thinnest thin film lower layer 1f are each divided into a plurality of parts, the effect of damping the residual pressure vibration can be further improved as compared with the second embodiment.

  An inkjet head, which is a droplet discharge head to which the present invention can be applied, includes an edge shooter method in which the shape from the ink flow path to the discharge port is linear, and a side shooter method in which the direction of the ink flow path differs from the direction of the discharge port Any of these may be used. Below, an example of this inkjet head is shown.

  First, an edge shooter type inkjet head will be described. In FIG. 15 showing the edge shooter type inkjet head 10, the inkjet head 10 includes an ejection energy generator 17 (an electrode for applying an ejection signal to the generator 17, a protective layer provided on the generator 17 as necessary, and the like). And a top plate 13 constituting a cover of the flow path 14 and a wall material 12 constituting the side wall of the flow path 14 and the orifice 15.

  In the inkjet head 10, when a recording signal is applied to the ejection energy generator 17 through an electrode (not shown) in a state where the ink is stored in the flow path 14 from a liquid chamber (not shown) in which ink is stored, the generator is generated. The ejection energy generated from 17 acts on the ink in the flow path 14 above the generator 17 (ejection energy operating section), and as a result, the ink is ejected as droplets from the orifice 15. The ejected ink droplets adhere to a recording material such as recording paper fed in front of the orifice 15.

  Such an edge shooter-type ink jet head has the advantage that each part can be precisely miniaturized, the orifices can be multi-sized or miniaturized, and the mass productivity is high. On the other hand, there are limits to the response frequency and ink-like flying speed when ejecting ink droplets. In addition, bubbles are generated in the ink due to the heat generated by the electrothermal conversion element. The bubbles contract due to a decrease in temperature, and the discharge energy generator 17 is gradually destroyed by an impact when the bubbles disappear in the vicinity of the discharge energy generator 17. Is done. This phenomenon is called a cavitation phenomenon, and is particularly remarkable in an edge shooter type ink jet head. For this reason, the edge shooter type inkjet head has a relatively short life.

  Next, a side shooter type inkjet head will be described. In FIG. 16 showing the side shooter type ink jet head 20, the ink jet head 20 is provided with an orifice 25 in the top plate 23, the ink flow direction 21 to the ejection energy acting portion in the flow path 24, and the opening central axis of the orifice 25. 22 is a right angle.

  With the above-described configuration, the energy from the ejection energy generator 27 can be converted more efficiently into the formation of ink droplets and their flying kinetic energy, and the meniscus can be quickly restored by supplying ink. This is particularly effective when a heating element is used for the discharge energy generator 27. Further, the side shooter method can avoid the occurrence of a so-called cavitation phenomenon, which is a problem in the edge shooter method, in which the discharge energy generator is gradually destroyed by the impact when the bubbles disappear. In other words, if the bubble grows and reaches the orifice in the side shooter system, the bubble is brought into the atmosphere, and the bubble does not contract due to the temperature drop. For this reason, there is an advantage that the life of the inkjet head is long.

  Next, the image forming apparatus 100 including the droplet discharge head 4 or the inkjet heads 10 and 20 described above will be described. 17 and 18, the carriage 103 is slidably held by guide rods 101 and guide rails 102 stretched on left and right side plates (not shown), and the main scanning motor 104 is actuated via the timing belt 105. The carriage 103 is moved and scanned in the main scanning direction indicated by an arrow 18. On the carriage 103, for example, a recording head 107, which is four droplet ejection heads that eject droplets of each color of yellow (Y), cyan (C), magenta (M), and black (K), includes a plurality of liquids. The droplet discharge ports are arranged in a direction orthogonal to the main scanning direction, and are mounted with the droplet discharge direction facing downward. A droplet discharge head using a piezoelectric actuator such as a piezoelectric element is used.

  In addition, a sub tank 108 for supplying ink of each color to the recording head 107 is mounted on the carriage 103 for each color. Each sub tank 108 is supplemented with ink from an ink cartridge as a main tank via an ink supply tube (not shown). In this embodiment, the sub tank 108 and the recording head 107 constitute the head cartridge 106. However, a configuration in which the sub tank 108 is provided separately, a configuration in which the ink cartridge is mounted on the carriage 103 without using the sub tank 108, and the like are employed. Also good.

  Under the image forming apparatus 100, a paper feeding unit that feeds the paper 112 stacked on a paper stacking unit (pressure plate) 111 such as a paper feeding cassette 110 is disposed. This paper feeding unit has a half-moon roller-shaped paper feeding roller 113 for separating and feeding the paper 112 one by one from the paper stacking unit 111, and a separation pad 114 made of a high friction resistance member disposed opposite to the paper feeding roller 113. The separation pad 114 is urged toward the paper feed roller 113 side.

  Further, as a transport unit for transporting the paper 112 fed from the paper feed unit below the recording head 107, a transport belt 121 that electrostatically attracts and transports the paper 112, and a guide 115 from the paper feed unit. A counter roller 122 that holds and conveys the paper 112 to be conveyed with the conveyance belt 121, a conveyance guide 123 that changes the direction of the paper 112 that is fed substantially vertically upward to substantially follow the conveyance belt 121, and a presser A tip pressure roller 125 urged toward the conveyor belt 121 by the member 124, a charging roller 126 as a charging unit for charging the surface of the conveyor belt 121, and the like are provided.

  A conveyance belt 121 made of an endless belt is stretched between a conveyance roller 127 and a tension roller 128, and the driving force from the sub-scanning motor 131 is transmitted through the timing belt 132 and the timing roller 133. The transport roller 127 circulates in the sub-scanning direction, which is the belt traveling direction in FIG. A guide member 129 is provided on the back side of the conveyance belt 121 in correspondence with an image forming area formed by the recording head 107. As shown in FIG. 18, a slit disk 134 is attached to the shaft of the conveying roller 127, and a sensor 135 that detects the rotation of the slit disk 134 is provided in the vicinity of the slit disk 134. And the sensor 135 constitute an encoder 136.

  The charging roller 126 is in contact with the surface layer of the conveyor belt 121 and is driven to rotate as the conveyor belt 121 travels, and a load of 2.5 N is applied to both ends of the support shaft as pressure. As shown in FIG. 17, an encoder scale 142 having slits is disposed in front of the carriage 103, and an encoder sensor 143 including a transmission type photosensor that detects the slits of the encoder scale 142 is disposed on the front surface of the carriage 103. It is arranged. Thus, an encoder 144 that detects the position of the carriage 103 in the main scanning direction (position relative to the home position) is configured.

  As a paper discharge unit that discharges the paper 112 recorded by the recording head 107, a separation unit that separates the paper 112 from the conveyance belt 121, a paper discharge roller 152 and a paper discharge roller 153, and a paper discharge unit that stocks the paper 112 to be discharged. A paper tray 154 is provided. A double-sided paper feeding unit 161 is detachably provided on the back side of the apparatus. The double-sided paper feeding unit 161 takes in and reverses the paper 112 returned by the reverse rotation of the transport belt 121 and feeds it again between the counter roller 122 and the transport belt 121.

  In the image forming apparatus 100 configured as described above, the sheets 112 are separated and fed one by one from the sheet feeding unit, and the sheet 112 fed substantially vertically upward is guided by the guide 115, and the conveyance belt 121 and the counter It is sandwiched between the rollers 122 and conveyed, and further, the leading end is guided by the conveying guide 123 and pressed against the conveying belt 121 by the leading end pressing roller 125, and the conveying direction is changed substantially at right angles.

  At this time, an alternating voltage is applied from a high voltage power supply to the charging roller 126 by a control circuit (not shown) so that a positive output and a negative output are alternately repeated, and the conveying belt 121 is in an alternating charging voltage pattern, that is, in a circumferential direction. In the sub-scanning direction, plus and minus are alternately charged in a band shape with a predetermined width. When the paper 112 is fed onto the conveyance belt 121 in which plus and minus are alternately charged, the paper 112 is attracted to the conveyance belt 121 by electrostatic force, and the paper 112 is moved in the sub-scanning direction by the circumferential movement of the conveyance belt 121. It is conveyed to.

  Therefore, by driving the recording head 107 according to the image signal while moving the carriage 103, droplets are ejected onto the stopped sheet 112 to record one line, and after the sheet 112 is conveyed by a predetermined amount, The following recording operation is performed. Upon receiving a recording end signal or a signal that the trailing edge of the paper 112 reaches the recording area, the recording operation is finished and the paper 112 is discharged to the paper discharge tray 154.

  In the case of double-sided image formation, the recording belt 112 is fed into the double-sided paper feeding unit 161 by rotating the conveyor belt 121 in reverse when the recording on the front surface (surface on which image formation is first performed) is completed. 112 is reversed (in a state where the back surface becomes the image forming surface), and is fed again between the counter roller 122 and the transport belt 121, and is controlled onto the transport belt 121 in the same manner as described above by performing timing control. After image formation, the paper is discharged to a paper discharge tray 154.

  The image forming apparatus according to the present invention can be applied to a printer, a facsimile, a copying machine, a complex machine of these, and the like, and a liquid droplet ejection head that ejects a liquid other than ink, such as a DNA sample, a resist, a pattern material, and the like. It can also be applied to a head cartridge and an image forming apparatus including these.

1, 1A, 1B, 1C Channel plate (liquid chamber substrate)
1a Liquid chamber 1b Fluid resistance 1c Common liquid chamber 1e Thin film part (liquid chamber damper)
1f Thinnest layer 2 Nozzle plate 2a Nozzle 2b Recessed part (damper air chamber)
DESCRIPTION OF SYMBOLS 3 Diaphragm 3d Supply port 3f Filter 4 Droplet discharge head 5 Drive means (laminated piezoelectric element)
7 Frame 10, 20 Droplet discharge head (inkjet head)
100 Image forming apparatus 106 Head cartridge 107 Liquid droplet ejection head (recording head)

Japanese Patent Laid-Open No. 10-100401 JP-A-2-289351 JP 2006-306066 A JP 2008-87464 A Japanese Patent No. 4394973

Claims (6)

A nozzle plate having a plurality of nozzles for discharging liquid as droplets, a liquid chamber for storing the liquid and communicating with the nozzles, and a flow path having fluid resistance formed in a flow path for flowing the liquid to the liquid chamber A plate, drive means for generating pressure to pressurize the liquid in the liquid chamber, and a diaphragm having a supply port for forming at least one wall surface of the liquid chamber and supplying the liquid to the liquid chamber; A liquid having a frame having a common liquid chamber for storing the liquid until it flows into the liquid chamber, and a filter having a plurality of holes provided in the supply port between the common liquid chamber and the diaphragm. In the droplet discharge head,
The supply port is provided in the flow path excluding the liquid chamber and the fluid resistance, a thin film portion is formed in the flow path plate facing the supply port, and the nozzle plate facing the thin film portion is A droplet discharge head, wherein a recess for avoiding contact with the thin film portion is formed. The droplet discharge head according to claim 1,
The droplet discharge head, wherein the hole has a tapered shape. The droplet discharge head according to claim 1 or 2,
The thin-film portion has a thinnest thin-film portion further thinned on the outer peripheral portion thereof. The droplet discharge head according to any one of claims 1 to 3,
A droplet discharge head, wherein a thinned portion is formed inside the thin film portion.   5. A head cartridge comprising the droplet discharge head according to claim 1.   An image forming apparatus comprising the liquid droplet ejection head according to claim 1.

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