JP2012011653A - Liquid ejection head and inkjet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid ejection head capable of alleviating crosstalk without attenuating energy (vibration) necessary for ejection, and an inkjet recorder having the same.SOLUTION: This liquid ejection head 10 has a plurality of ejectors each of which is constituted by a nozzle 12 for ejecting liquid droplets, a pressure chamber 14 provided corresponding to the nozzle 12 and an energy generation element 16 for applying an ejection force to liquid in the pressure chamber 14. The liquid ejection head 10 includes common fluid channels 20, 30 for supplying liquid to the plurality of pressure chambers 14, constriction sections provided at discrete fluid channel portions 22, 32 connecting the respective pressure chambers 14 to the common fluid channels 20, 30, and atmospheric air opening holes 24, 34 which communicate with the common fluid channels 20, 30 and have openings at a nozzle face 11. Fluid vibration is absorbed by vibration of meniscuses in the atmospheric air opening holes 24, 34.

Description

  The present invention relates to a liquid discharge head, and in particular, a liquid discharge head having a structure in which liquid is supplied from a common channel to a plurality of pressure chambers corresponding to a plurality of discharge ports (nozzles), and an ink jet using the same. The present invention relates to a technique for preventing fluid mutual interference (crosstalk) between nozzles in a recording apparatus.

  In general, an ink jet head is provided with a plurality of ink ejection elements (ejectors) that eject ink droplets from nozzles by filling a liquid in a pressure chamber communicating with a nozzle and driving an energy generating element provided in the pressure chamber. Yes. Thus, in the inkjet head having a plurality of ejectors, a plurality of pressure chambers are connected in parallel to a common ink channel (common channel), and a channel structure for supplying ink from the common channel to each pressure chamber is provided. It is known (patent documents 1 to 3).

  In an inkjet head having such a flow channel structure, when one energy generating element is driven and ink is ejected from a nozzle, the ink flow at the time of ejection is connected to the same flow channel via a common flow channel. A phenomenon called crosstalk that affects the nozzle and makes the discharge unstable occurs.

  To deal with the problem of crosstalk, Patent Document 1 includes an air communication hole in the communication channel connecting the ink reservoir and the main flow channel of the nozzle, and absorbs and absorbs pressure waves due to meniscus vibration of ink in the air communication hole. The structure to perform is disclosed. Patent Document 2 discloses a configuration in which an inkjet head includes a dummy nozzle that does not eject ink in addition to an ejection nozzle that ejects ink. On the other hand, in Patent Document 3, a filter is disposed in the middle of the ink supply path for the purpose of enhancing the discharge of dust and bubbles, and a bypass flow path branched from the filter to the upstream side is provided. A configuration is proposed in which a dummy nozzle is provided at the end of the flow path.

JP-A-8-132039 JP 2004-195959 A JP 2003-226010 A

  However, in the configuration of Patent Document 1, since the discharge energy generated by the energy generating element is absorbed by the meniscus of the air communication hole, excessive discharge energy is required to discharge droplets from the nozzle. Further, according to FIG. 1 in Patent Document 1, the air communication hole is open at the bottom of a groove (atmosphere communication hole groove) formed on the upper surface of the head, and is different from the nozzle surface on which the nozzle is formed. Has been placed. For this reason, maintenance is difficult when the air communication hole is clogged due to dust and ink sticking, and the effect of suppressing crosstalk cannot be sufficiently exhibited.

  The technique described in Patent Document 2 causes pressure waves to be individually generated in the dummy nozzles so that substantially the same crosstalk as the discharge nozzles located inside acts on the discharge nozzles located at the print range end parts. Is not a technique for reducing the crosstalk itself. Patent Document 3 aims to remove bubbles from the dummy nozzle, and Document 3 is not a technique for reducing crosstalk.

  The present invention has been made in view of such circumstances, and provides a liquid discharge head capable of reducing crosstalk without attenuating energy (vibration) necessary for discharge, and an ink jet recording apparatus using the liquid discharge head. The purpose is to do.

  In order to achieve the above object, the following invention modes are provided.

  (Invention 1): The liquid ejection head according to Invention 1 corresponds to each of a plurality of nozzles for ejecting liquid droplets, a plurality of pressure chambers provided corresponding to the plurality of nozzles, and the plurality of pressure chambers. An energy generating element that gives a discharge force to the liquid in each pressure chamber, a common flow path that communicates with the plurality of pressure chambers and supplies the liquid to each pressure chamber, and each pressure chamber for each pressure chamber And a throttle part provided in an individual flow channel part connecting between the common flow channel, an air opening hole communicating with the common flow channel and having an opening on a nozzle surface on which the plurality of nozzles are formed, It is provided with.

  According to the present invention, a liquid meniscus is formed in the air opening hole connected to the common flow path. Fluid vibration due to refilling when the energy generating element is driven and droplets are ejected from the nozzle is absorbed by meniscus vibration in the atmosphere opening hole, and crosstalk is suppressed. In addition, since the restriction part is provided in the individual flow path part between the pressure chamber and the common flow path, the discharge energy generated by the energy generating element is difficult to propagate to the common flow path side and is efficiently used as discharge force. The For this reason, the vibration propagated through the common flow path can be suppressed without attenuating the vibration necessary for ejection.

  Furthermore, since the air opening hole is open to the nozzle surface, cleaning processing such as suction purge (operation of sucking and removing liquid from the nozzle and the air opening hole by applying a cap to the nozzle surface) together with the nozzle is possible. Easy maintenance.

  As the “energy generating element”, there are an aspect using a piezoelectric body (piezo jet system), an aspect using an electrostatic actuator, an aspect using a heat generating element (heater) in a thermal jet system, and the like.

  (Invention 2): In the liquid ejection head according to Invention 2, when the inertance of the nozzle is La, the inertance of the constricted portion is Lb, and the inertance of the air opening hole is Lc in the invention 1, Lb> La and Lb> Lc.

  By satisfying the condition of Lb> La, energy generated by driving the energy generating element can be efficiently used as energy for discharging droplets. Further, by satisfying the condition of Lb> Lc, vibration generated in the common flow path can be effectively absorbed by vibration of the meniscus surface of the air opening hole without propagating to the nozzle (pressure chamber).

  (Invention 3) The liquid ejection head according to Invention 3 is the invention 1 or 2, wherein the flow resistance value from the common flow path to the nozzle opening is Ra, and the common flow path to the opening of the atmosphere opening hole is the invention 1 or 2. If the channel resistance value of R is Rc, then Ra <Rc.

  By satisfying the condition of Ra <Rc, the liquid can be more effectively extracted from the ejection nozzle when purging by suction with the cap in contact with the nozzle surface.

  (Invention 4): The liquid ejection head according to Invention 4, in any one of Inventions 1 to 3, wherein the air release hole is a straight flow extending straight from the common flow path toward the nozzle surface. It is connected to the common flow path by a path.

  According to this aspect, in the head manufacturing process, the air opening hole can be created by the same process as the nozzle hole, and the manufacturing is easy.

  (Invention 5): The liquid discharge head according to Invention 5, in any one of Inventions 1 to 4, wherein the air release hole is a straight flow extending straight from the common flow path toward the nozzle surface. It has a channel | path part and the counterbore part which the area of an opening surface becomes large toward the opening of the said nozzle surface from this flow-path part, It is characterized by the above-mentioned.

  According to this aspect, the meniscus spreads in the counterbore part, and the effect | action which absorbs a vibration improves further.

  (Invention 6): The liquid discharge head according to Invention 6 is the liquid ejection head according to any one of Inventions 1 to 5, wherein the number of the air opening holes provided in communication with the common flow path is parallel to the common flow path. Fewer than the number of pressure chambers connected.

  The number of the air opening holes can be appropriately designed. The greater the number, the greater the effect of vibration absorption.

  It is only necessary that at least one atmosphere opening hole is formed in the common flow path in which the plurality of pressure chambers are connected in parallel.

  (Invention 7): A liquid discharge head according to Invention 7, in any one of Inventions 1 to 6, wherein one end of the common flow path is connected to connect the common flow path to another flow path. A mouth is provided, and the other end is a terminal end of the common flow path, and the atmosphere opening hole is disposed at least in the terminal end of the common flow path.

  Although various design forms are possible for the place where the atmosphere opening hole is arranged, it is effective to arrange it at the dead end portion (terminal portion) of the common flow path.

  (Invention 8): A liquid discharge head according to Invention 8, in any one of Inventions 1 to 7, wherein one end of the common flow path is connected to another flow path via a connection port. In the common flow path from the connection port to the terminal end of the other end, more air release holes are arranged on the terminal end side.

  When arranging a plurality of air opening holes in the common flow path, it is effective to have a distribution in which more air opening holes are arranged on the terminal end side than on the connection port side.

  (Invention 9): The liquid ejection head according to Invention 9 is the liquid ejection head according to any one of Inventions 1 to 8, wherein the individual recovery flow channel individually communicates with the pressure chambers, and the individual recovery flow channel is used for the liquid discharge head. A plurality of pressure chambers, a common recovery channel for recovering a liquid from each pressure chamber, an atmosphere opening hole that communicates with the common recovery channel and has an opening on a nozzle surface on which the plurality of nozzles are formed; It is provided with.

  When the supply channel and the recovery channel are communicated with the pressure chamber and the liquid is circulated, an air opening hole can be formed in the common recovery channel.

  When the liquid can be supplied from the common recovery channel to the pressure chamber through the recovery channel, the common recovery channel can be interpreted as corresponding to the “common channel” in the first aspect.

  (Invention 10): A liquid discharge head according to Invention 10 corresponds to each of a plurality of nozzles for discharging droplets, a plurality of pressure chambers provided corresponding to the plurality of nozzles, and the plurality of pressure chambers. And an energy generating element that provides a discharge force to the liquid in each pressure chamber, a first common flow path that communicates with the plurality of pressure chambers and supplies the liquid to each pressure chamber, and the first common flow path A first connection port provided in the first common flow path for connecting the pressure chamber to the other first flow path, and a first individual flow connecting each pressure chamber and the common flow path for each pressure chamber. A channel, a second individual channel individually communicating with each of the pressure chambers, and a plurality of pressure chambers communicating with the plurality of pressure chambers via the second individual channel, and recovering liquid from each pressure chamber or each pressure chamber A second common flow path for supplying liquid to the second flow path and connecting the second common flow path to another second flow path Of the second connection port provided in the second common channel, the first common channel and the second common channel, the channel resistance value from the first connection port to the pressure chamber and the second An air opening hole having an opening on a nozzle surface in which the plurality of nozzles are formed, and is connected to a common flow path having a lower flow path resistance value by comparing the flow path resistance value from the connection port to the pressure chamber. , Provided.

  A tenth aspect of the present invention includes a liquid discharge head having a circulation system described in the ninth aspect, wherein the liquid is supplied from the common recovery flow path side to the pressure chamber through the individual recovery flow path.

  That is, the “common recovery channel” and “individual recovery channel” of the ninth aspect of the invention can correspond to the “second common channel” and the “second individual channel”, respectively. Therefore, the features described in Inventions 1 to 9 can be combined for Invention 10.

  (Invention 11): An ink jet recording apparatus according to Invention 11 generates a drive voltage signal to be applied to the liquid ejection head according to any one of Inventions 1 to 10 and the energy generation element, and It is characterized by comprising drive control means for controlling the discharge operation and transport means for relatively moving the liquid discharge head and the drawing medium.

  As a configuration example of a print head (recording head) used in an ink jet recording apparatus, a nozzle array in which a plurality of head modules are connected to each other and a plurality of ejection ports (nozzles) extending over the entire width of the drawing medium is arranged. It is possible to use a full line type head having the same. Such a full-line type head is usually arranged along a direction orthogonal to the relative feeding direction (relative conveyance direction) of the drawing medium (paper), but with respect to the direction orthogonal to the conveyance direction. Thus, there may be a mode in which the head is arranged along an oblique direction having a predetermined angle.

  “Drawing medium” is a medium (which may be called a printing medium, an image forming medium, a recording medium, an image receiving medium, a discharged medium, or the like) that receives adhesion of droplets discharged from the discharge port of the head. Various media are included regardless of material or shape, such as continuous paper, cut paper, sealing paper, resin sheets such as OHP sheets, printed boards on which films, cloths, wiring patterns, etc. are formed.

  When a color image is formed using an ink jet print head, a head may be arranged for each color of a plurality of inks (recording liquids), or a plurality of colors of ink can be ejected from one recording head. It is good also as a simple structure.

  According to the present invention, crosstalk can be effectively reduced without attenuating energy (vibration) necessary for ejection.

Sectional drawing which showed typically the structure of the liquid discharge head which concerns on embodiment of this invention The top view which shows the example of arrangement | positioning of the nozzle in the nozzle surface of the inkjet head which concerns on this embodiment, and an air release hole The top view which shows the other example of arrangement | positioning of the nozzle and air | atmosphere open hole in a nozzle surface The top view which shows the other example of arrangement | positioning of the nozzle and air | atmosphere open hole in a nozzle surface Cross-sectional view showing an example of the flow path shape of the air opening hole Perspective plan view showing the flow path structure inside the head module 1 is a configuration diagram of an ink jet recording apparatus according to an embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<Configuration example of liquid discharge head>
FIG. 1 is a cross-sectional view schematically showing a configuration of a liquid discharge head according to an embodiment of the present invention. Here, the inkjet head 10 that ejects ink droplets will be described as an example, but in the practice of the present invention, the liquid used for ejection is not limited to ink.

  The ink jet head 10 includes a nozzle 12 serving as an ink discharge port, a pressure chamber 14 communicating with the nozzle 12, an actuator 16 (corresponding to an “energy generating element”) provided corresponding to the pressure chamber 14, and a pressure chamber 14. A first common flow path 20 for supplying liquid to the first flow path, and a first individual flow path 22 (corresponding to “individual flow path portion” and “throttle section”) for guiding ink from the first common flow path 20 to the pressure chamber 14. Prepare.

  A discharge element (ejector) serving as a recording element unit for forming one pixel dot is configured by the configuration including the nozzle 12, the pressure chamber 14 corresponding thereto, and the actuator 16 provided in the pressure chamber 14. Although FIG. 1 shows only one ejection element (only one nozzle), the inkjet head 10 is provided with a plurality of ejection elements having the same configuration.

  A plurality of pressure chambers 14 are connected to the first common flow path 20 in parallel via the first individual flow paths 22, and each of the first common flow paths 20 passes through the first individual flow paths 22 and passes through the first individual flow paths 22. Ink is supplied to the pressure chamber 14. The first common flow path 20 is connected to an ink reservoir (not shown), and the ink reservoir is further connected to an ink tank (not shown) serving as an ink supply source. The first individual flow path 22 connecting the first common flow path 20 and the pressure chamber 14 is a throttle section (the narrowest constriction section) having a sufficiently small flow path cross-sectional area as compared with the pressure chamber 14 and the first common flow path 20. Function.

  In addition, the inkjet head 10 of this example includes a second common flow path 30 that is used as an ink supply path and a recovery path. Each pressure chamber 14 is individually connected to a second individual flow path 32 (corresponding to an “individual recovery flow path”), and each pressure chamber 14 and the second common flow path are connected via the second individual flow path 32. 30 is in communication. The second common flow path 30 is connected to an ink reservoir (not shown), and the ink reservoir is connected to an ink recovery tank (not shown). Similarly to the first individual flow path 22, the second individual flow path 32 that connects the second common flow path 30 and the pressure chamber 14 also functions as a throttle unit.

  A pressure difference is provided between the first common flow path 20 and the second common flow path 30, and ink is supplied from the first common flow path 20 through the first individual flow path 22 to the pressure chamber 14 during non-ejection. Then, the ink slowly flows out from the pressure chamber 14 through the second individual flow path 32 to the second common flow path 30. By adopting such an ink circulation system, it is possible to always supply fresh ink to each pressure chamber 14, and to prevent the ink from thickening. Thereby, the stable discharge for a long time is possible.

  The speed at which ink flows due to this pressure difference in the circulation system is sufficiently slower than the speed at which ink is ejected during ejection (printing) (ejection cycle), and the speed of the ink ejected by the ink (liquid exiting the nozzle) ) Is faster. Therefore, during the continuous ejection operation, the flow of ink from the pressure chamber 14 toward the second individual flow path 32 becomes slow, and finally the pressure chamber passes from the second common flow path 30 through the second individual flow path 32. 14 is supplied with ink. As described above, the recovery system composed of the second common flow path 30 and the second individual flow path 32 functions as an ink supply flow path during the ejection operation, and from both sides of the first individual flow path 22 and the second individual flow path 32. Ink flows into the pressure chamber 14.

  A piezoelectric element is used for the actuator 16 of this example. Although not shown in the drawing, the piezoelectric element has a structure in which a piezoelectric body is interposed between the lower electrode and the upper electrode. The lower electrode is a common electrode (common electrode) for the plurality of actuators 16, and the upper electrode is an individual electrode for each actuator 16.

  A unimorph actuator is configured by a structure in which a piezoelectric element is bonded to the vibration plate 42 that constitutes the upper wall of the pressure chamber 14, and the vibration plate 42 is bent and deformed by distortion in the d31 direction of the piezoelectric body. . When a drive voltage is applied between the electrodes of the actuator 16, the actuator 16 is displaced and the volume of the pressure chamber 14 changes. Ink is ejected from the nozzles 12 by this volume change.

  In addition, although the d31 mode piezoelectric actuator is illustrated here, the energy generation element is not limited to this, and various modes such as a piezoelectric actuator using a d33 mode or a shear mode, an electrostatic actuator, a heating element, and the like. Is possible. A corresponding energy generating element corresponding to the ejection method employed is used.

  The inkjet head 10 of this example is referred to as an “air release hole 24” (hereinafter referred to as “first atmosphere release hole”) below the first common flow path 20 and communicating with the first common flow path 20 and opening in the nozzle surface 11. ) Is formed. Similarly, an air release hole 34 (hereinafter referred to as a “second air release hole”) that communicates with the second common flow path 30 and opens on the nozzle surface is formed under the second common flow path 30. .

  Ink meniscus 51 and 52 are formed in the first atmosphere opening hole 24 and the second atmosphere opening hole 34, respectively. The vibration (crosstalk) of each common flow path (20, 30) due to refill accompanying ink ejection from the nozzle 12 is absorbed by the vibration of the meniscus 51, 52 of the atmosphere opening hole (24, 34) and transferred to other nozzle holes. Suppresses the propagation of

  The size, number, and shape of the air opening holes (24, 34) are not particularly limited. The greater the number, the greater the vibration suppression effect. From the viewpoint of preventing ink droplets from adhering to unintended positions on the paper (the drawing medium) by the atmosphere opening holes (24, 34), the conditions for the atmosphere opening holes (24, 34) include the common flow paths (20, 30). Even if the meniscus (51, 52) is shaken by the transmitted vibration and the ink is overflowed from the air opening holes (24, 34), it is necessary that the meniscus does not drop from the nozzle surface 11 (the meniscus is not destroyed). The opening area, the number of holes, and the arrangement distribution of the holes are designed so that the meniscus can be maintained by fluid vibration. In general, a hole having the same size as the discharge nozzle 12 is formed.

  Considering the number of pressure chambers 14 connected to the same common flow path (20, 30) and the resonance frequency of the common flow path (20, 30), the number of simultaneous discharge nozzles when droplets are ejected at the resonance frequency It is preferable to perform a corresponding design.

  The flow channel structure as shown in FIG. 1 is formed by etching silicon (Si) to form a groove or a hole to be a flow channel portion, or by bonding substrates using a thermal diffusion bonding technique or the like. Can be produced.

(Regarding the arrangement example of nozzle and air opening hole)
FIG. 2 is a plan view of the nozzle surface 11 of the inkjet head 10 (viewed from the ejection side). In FIG. 2, the flow path structure existing on the back side of the nozzle surface 11 is indicated by a broken line. Here, only a nozzle row in which a plurality of nozzles 12 are arranged in a row is shown, but a mode in which a plurality of such nozzle rows are provided is also possible.

  In FIG. 2, a connection port denoted by reference numeral 26 at the left end of the first common flow path 20 is a flow path connection portion connected to an ink reservoir (not shown) on the supply side. The end opposite to the connecting port 26 (the right end in FIG. 2) is not provided with a connecting port connected to the ink reservoir and other flow paths, and serves as a terminal end of a dead end.

  The first common flow path 20 can be formed with a plurality of the first atmospheric opening holes 24 described with reference to FIG. 1, but only one atmospheric opening hole is provided for one common flow path. As shown in FIG. 2, it is preferable to dispose the first atmosphere opening hole 24 at the terminal portion which is a dead end wall. Such an arrangement can most effectively reduce the influence of vibration.

  In FIG. 2, a connection port indicated by a reference numeral 36 at the right end of the second common flow path 30 is a flow path connection portion connected to an ink reservoir (not shown) on the collection side. The end opposite to the connection port 36 (the left end in FIG. 2) is not provided with a connection port connected to the ink reservoir and other flow paths, and serves as a terminal end of a dead end.

  In the second common flow path 30, it is possible to form a plurality of the second air opening holes 34 described in FIG. 1, but when only one air opening hole is provided for one common flow path. As shown in FIG. 2, it is preferable to dispose the second atmosphere opening hole 34 at the terminal portion that is a dead end wall. Such an arrangement can most effectively reduce the influence of vibration.

  In the case where the ink is supplied from the first common flow path 20 and the second common flow path 30 to the pressure chamber 14 with an equal balance at the time of ejection, the first common flow path 20 and the second common flow path 30 are equal to each other. An embodiment in which the air opening holes (24, 34) are provided is preferable.

  When the ink supply balance to the pressure chamber 14 is not uniform, it is preferable to design the arrangement of the air release holes (24, 34) according to the balance. More air opening holes are arranged in the common flow path having the larger supply amount.

  In FIG. 2, the nozzle 12, the atmosphere opening holes (24, 34), and the connection ports (26, 36) are all rectangular, but the cross-sectional shape of the flow path of each part is not particularly limited, and is circular or elliptical. Various forms such as a shape, a semi-circle, a semi-ellipse, and a polygon are possible.

  In addition, as for the shape of the pressure chamber 14, a circular pressure chamber is shown in a plan view in FIG. 2, but the shape of the pressure chamber is not particularly limited, and various forms such as an ellipse, a rhombus, a polygon, and the like are possible. is there.

(Modification 1)
FIG. 2 shows an example in which one atmosphere opening hole (24, 34) is formed for each common flow path (20, 30). However, the number of atmosphere opening holes and the distribution of arrangement (arrangement) Various designs are possible.

  For example, in FIG. 2, the flow resistance value from the supply side connection port 26 (corresponding to “first connection port”) to the pressure chamber 14 (from the connection port 26 to the first common flow path 20 and the first individual flow path 22. The flow path resistance value of the flow path system leading to the pressure chamber 14) and the flow path resistance value (from the connection port 36) from the recovery side connection port 36 (corresponding to “second connection port”) to the pressure chamber 14. The flow resistance value of the flow path system that reaches the pressure chamber 14 through the second common flow path 30 and the second individual flow path 32), the common flow belonging to the flow path system having the lower flow path resistance value. It is effective to arrange an air opening hole in the path (20 or 30). As a specific example, the flow resistance value of the flow path including the first common flow path 20 and the first individual flow path 22 is greater than the flow resistance value of the flow path including the second common flow path 30 and the second individual flow path 32. Is smaller, at least one atmosphere opening hole (24) is formed only in the first common flow path 20, and no air opening hole is formed in the second common flow path 30. Alternatively, a form in which more air opening holes are arranged in the common flow path having the smaller flow path resistance value is also possible.

  An ink reservoir (not shown) connected to the connection port 26 indicated by reference numeral 26 corresponds to “another first flow path”, and an ink reservoir (not shown) connected to the connection port 36 indicated by reference numeral 36. ) Corresponds to “another second flow path”.

(Modification 2)
FIG. 3 is a diagram showing another modification. 3, elements that are the same as or similar to those described in FIGS. 1 and 2 are given the same reference numerals, and descriptions thereof are omitted.

  As shown in FIG. 3, a plurality of air opening holes (24A to 24C, 34A to 34C) can be arranged for one common flow path (20, 30). In the figure, air opening holes 24A, 24B, and 24C are formed in the vicinity of the end portion (right end portion) of the first common flow path 20 and the two nozzles 12 closer to the end portion, respectively. Similarly, the second common flow path 30 has air release holes 34A, 34B, and 34C in the vicinity of the terminal end (left end) of the second common flow path 30 and the two nozzles 12 closer to the terminal end, respectively. Is formed.

  In FIG. 3, the air release holes (24B, 24C, 34B, 34C) are arranged in the vicinity of the branch points where the common flow paths (20, 30) branch to the individual flow paths (22, 32). 24B, 24C, 34B, 34C) and the individual flow paths (22, 32) are not limited to this. For example, a form in which the air opening hole is arranged at an intermediate position between adjacent individual flow paths is also possible.

  Moreover, in FIG. 3, although three atmosphere open holes (24A-24C, 34A-34C) were formed about one common flow path (20, 30), the number of atmosphere open holes is not limited to this, but four or more It may be the same as the number of nozzles.

  When the number of air opening holes is smaller than the number of nozzles, more air is released in the common flow path (20, 30) where the cross-talk is greatly affected, that is, near the terminal end which is a dead end wall. If the holes are arranged, vibrations can be absorbed more efficiently.

(Modification 3)
1 to 3, the circulation type head that circulates the ink in the pressure chamber 14 has been described, but the present invention is also applied to a non-circulation type head that does not have a circulation system (recovery system) flow path. it can. FIG. 4 shows an arrangement example of the nozzles and the air opening holes in the non-circulating head. In FIG. 4, the same or similar components as those in the example described in FIG.

<Preferable conditions for air opening holes>
(Conditions for inertance)
It is desirable that Lb> La and Lb> Lc when the inertances of the ink ejection nozzle, the throttle portion, and the air opening hole are La, Lb, and Lc, respectively.

  The inertance L is expressed by the following equation (Equation 1), where ρ is the ink density, l is the length of the flow path, and S is the cross-sectional area perpendicular to the flow line of the flow path.

  By satisfying Lb> La, the energy applied by driving the energy generating element (actuator) can be effectively used for discharging droplets, and can be discharged efficiently. Further, since Lb> Lc, vibration generated in the common flow channel can be absorbed by vibration of the meniscus surface of the air opening hole without being transmitted to the nozzle.

(Conditions for channel resistance)
If the flow resistance value from the common flow path to the discharge nozzle is Ra and the flow resistance value from the common flow path to the atmosphere opening hole is Rc, it is preferable that Ra <Rc. With this design, when purging by suction with the cap abutting against the nozzle surface, ink can be more effectively extracted from the discharge nozzle, and within the discharge flow path (pressure chamber). It is possible to efficiently remove mixed dust and bubbles.

  The flow path resistance R is expressed by the following equation (Equation 2), where the ink viscosity η and the cross-sectional circumferential length of the flow path are T.

(About the shape of the air opening hole)
5A and 5B show examples of air opening holes. Here, the first atmosphere opening hole 24 communicating with the first common flow path 20 will be described, but the same applies to the second atmosphere opening hole 34 communicating with the second common flow path 30.

  The air opening hole 24 shown in FIG. 5A communicates with the first common flow path 20 via a straight flow path 26 that extends straight from the first common flow path 20 toward the nozzle surface 11. Yes.

  Thus, the flow path 26 linearly formed directly below the first common flow path 20 can be formed by a manufacturing process similar to that for the nozzle holes.

  The air opening hole 24 shown in FIG. 5B is a straight-shaped channel portion (reference numeral 26, hereinafter referred to as “straight portion”) that extends straight from the first common channel 20 toward the nozzle surface 11. A counterbore 27 is added on the exit side. The counterbore part 27 of this example has an inversely tapered shape in which the opening area gradually increases from the lower end of the straight part 26 toward the nozzle surface 11.

  According to such a configuration, the meniscus 51 is formed at the boundary between the straight part 26 and the counterbore part 27 during non-ejection, and the meniscus 51 moves to the counterbore part 27 due to vibrations transmitted to the first common flow path 20 during ejection. spread. Thereby, the overflow amount of the liquid that absorbs the fluid vibration is increased, and the vibration absorption effect is further improved as compared with the example of FIG.

(About aperture types)
In the above-described embodiment, the configuration of the aperture portion has been described with a reduced cross-sectional area, but the aperture configuration is not limited to this. For example, the structure which arrange | positions the member which inhibits a flow in a flow path, such as the thing of the shape which stood the pillar in the flow path, is also possible. Moreover, it is also possible to employ a folded flow path that is up / down in the vertical direction, instead of the straight pipe line.

<Example of head module>
2 to 4, one nozzle row has been described. However, the arrangement of the nozzles 12 is not limited to a linear arrangement, but may be a polygonal line formed by combining straight lines such as a V shape or a W shape, Various designs such as an array form along a curve like a wavy line are possible.

  FIG. 6 shows an example of a head module in which nozzles are two-dimensionally arranged in a matrix.

  FIG. 6 is a perspective plan view showing a flow path structure inside the head module. In FIG. 6, the y direction is the paper (drawing medium) feed direction (sub-scanning direction), and the x direction is the paper width direction (main scanning direction). This head module 300 has an end face on the long side along the v direction having an inclination of angle γ with respect to the x direction and an end face on the short side along the w direction having an inclination of angle α with respect to the y direction. The plane shape of a parallelogram having

  A page-wide inkjet head bar that can be formed by connecting a plurality of head modules as shown in FIG. 6 in the paper width direction to form an image with a single scan for the entire drawing range of the paper width (full line capable of single-pass printing). Type inkjet head).

  In FIG. 6, reference numeral 380 represents a nozzle. As shown in the drawing, a supply-side ink flow path 310 and a recovery-side ink flow path 320 are provided for each nozzle row in which the nozzles 380 are arranged in the w direction in the figure, with the nozzle row interposed therebetween. The supply-side ink flow path 310 and the recovery-side ink flow path 320 correspond to the first common flow path 20 and the second common flow path 30 described with reference to FIGS.

  In FIG. 6, the supply-side ink flow path 310 provided along the w direction is a branch flow path branched from the supply-side common flow path main flow 330 (corresponding to the supply-side ink reservoir). The main flow 330 is connected to an ink tank (not shown) via a supply connection port (not shown). The recovery-side ink flow path 320 is a branch flow path branched from the recovery-side common flow path main stream 340 (corresponding to the recovery-side ink reservoir), and the recovery-side common flow path main flow 340 is connected via a connection port (not shown). Connected to a collection tank (not shown).

  A channel connecting portion (branch portion) between the supply-side common channel main flow 330 and each supply-side ink channel 310 corresponds to the connection port 26 described with reference to FIG. Further, the flow path connecting portion (branch portion) between the recovery side common flow path main flow 340 and each recovery side ink flow path 320 corresponds to the connection port 36 described with reference to FIG.

  Although not shown in FIG. 6, each supply-side ink flow path 310 and recovery-side ink flow path 320 are each provided with an air opening hole as described in FIG. 2 or FIG. 3.

<Effects of Embodiment>
According to the embodiment of the present invention described with reference to FIG. 1 to FIG. 6, it is possible to reduce the influence of crosstalk without lowering the ejection efficiency from the discharge nozzle. Further, since the air opening hole is opened in the nozzle surface 11 and can be cleaned by the same maintenance means as the ejection nozzle (suction purge with a suction cap, etc.), the air opening hole is clogged due to ink sticking or the like. It is possible to prevent the crosstalk reduction effect from being lowered.

<Configuration Example of Inkjet Recording Device>
An example of an ink jet recording apparatus using the ink jet head according to the embodiment of the present invention described above will be described.

  FIG. 7 is an overall configuration diagram showing a configuration example of the ink jet recording apparatus according to the embodiment of the present invention. The ink jet recording apparatus 100 of this example mainly includes a paper feeding unit 112, a treatment liquid application unit (precoat unit) 114, a drawing unit 116, a drying unit 118, a fixing unit 120, and a paper discharge unit 122. The ink jet recording apparatus 100 uses an ink jet head 172M on a recording medium 124 (corresponding to a “drawing medium”, which may hereinafter be referred to as “paper” for convenience) held on an impression cylinder (drawing drum 170) of the drawing unit 116. , 172K, 172C, and 172Y, a single-pass inkjet recording apparatus that forms a desired color image by ejecting droplets of a plurality of colors, and a processing liquid (here, agglomerates) on the recording medium 124 before the droplets are ejected. This is an on-demand type image forming apparatus to which a two-liquid reaction (aggregation) method is applied in which an image is formed on a recording medium 124 by reacting the processing liquid and the ink liquid.

(Paper Feeder)
A recording medium 124 that is a sheet is stacked on the paper feeding unit 112, and the recording medium 124 is fed one by one from the paper feeding tray 150 of the paper feeding unit 112 to the processing liquid application unit 114. In this example, a sheet (cut paper) is used as the recording medium 124, but a configuration in which continuous paper (roll paper) is cut to a required size and fed is also possible.

(Processing liquid application part)
The processing liquid application unit 114 is a mechanism that applies the processing liquid to the recording surface of the recording medium 124. The treatment liquid contains a color material aggregating agent that agglomerates the color material (pigment in this example) in the ink applied by the drawing unit 116, and the ink comes into contact with the treatment liquid and the ink. And the solvent are promoted.

  The processing liquid application unit 114 includes a paper feed cylinder 152, a processing liquid drum (also referred to as “precoat cylinder”) 154, and a processing liquid coating device 156. The processing liquid drum 154 includes a claw-shaped holding means (gripper) 155 on the outer peripheral surface thereof, and the recording medium 124 is sandwiched between the claw of the holding means 155 and the peripheral surface of the processing liquid drum 154. The tip can be held.

  A processing liquid coating device 156 is provided outside the processing liquid drum 154 so as to face the peripheral surface thereof. The processing liquid coating device 156 includes a processing liquid container in which the processing liquid is stored, an anix roller (measuring roller) partially immersed in the processing liquid in the processing liquid container, the anix roller and the processing liquid drum 154. A rubber roller that is pressed against the upper recording medium 124 and transfers the measured processing liquid to the recording medium 124. Instead of the application method using a roller, various methods such as a spray method and an ink jet method can be applied.

  The recording medium 124 to which the processing liquid is applied is transferred from the processing liquid drum 154 to the drawing drum 170 of the drawing unit 116 via the intermediate transport unit 126.

(Drawing part)
The drawing unit 116 includes a drawing drum (also referred to as “drawing cylinder” or “jetting cylinder”) 170, a sheet pressing roller 174, and inkjet heads 172M, 172K, 172C, and 172Y. Similar to the treatment liquid drum 154, the drawing drum 170 includes a claw-shaped holding means (gripper) 171 on the outer peripheral surface thereof. Ink is applied to the recording medium 124 fixed to the drawing drum 170 from the inkjet heads 172M, 172K, 172C, 172Y.

  Each of the inkjet heads 172M, 172K, 172C, and 172Y is a full-line inkjet recording head having a length corresponding to the maximum width of the image forming area in the recording medium 124, and image formation is performed on the ink ejection surface thereof. A nozzle row (two-dimensional array nozzle) in which a plurality of nozzles for ejecting ink are arranged over the entire width of the region is formed. Each inkjet head 172M, 172K, 172C, 172Y is installed so as to extend in a direction orthogonal to the conveyance direction of the recording medium 124 (the rotation direction of the drawing drum 170).

  Corresponding color ink cassettes (ink tanks) are attached to the respective ink jet heads 172M, 172K, 172C, and 172Y. Ink droplets are ejected from the inkjet heads 172M, 172K, 172C, and 172Y toward the recording surface of the recording medium 124 held on the outer peripheral surface of the drawing drum 170.

  As a result, the ink comes into contact with the treatment liquid previously applied to the recording surface, and the color material (pigment) dispersed in the ink is aggregated to form a color material aggregate. As an example of the reaction between the ink and the treatment liquid, in this embodiment, an acid is contained in the treatment liquid, and the pigment dispersion is destroyed and aggregated by the PH down. Avoids droplet ejection interference due to liquid coalescence. Thus, the color material flow on the recording medium 124 is prevented, and an image is formed on the recording surface of the recording medium 124.

  The droplet ejection timing of each inkjet head 172M, 172K, 172C, 172Y is synchronized with an encoder (not shown) that detects the rotational speed arranged on the drawing drum 170. Further, maintenance operations such as cleaning of the nozzle surfaces of the inkjet heads 172M, 172K, 172C, and 172Y and discharging the thickened ink (suction purge) may be performed by retracting the head unit from the drawing drum 170.

  In this example, the configuration of CMYK standard colors (four colors) is illustrated, but the combination of ink colors and the number of colors is not limited to this embodiment, and light ink, dark ink, and special color ink are used as necessary. May be added. For example, it is possible to add an inkjet head that discharges light-colored ink such as light cyan and light magenta, and the arrangement order of the color heads is not particularly limited.

  The recording medium 124 on which an image is formed by the drawing unit 116 is transferred from the drawing drum 170 to the drying drum 176 of the drying unit 118 via the intermediate conveyance unit 128.

(Drying part)
The drying unit 118 is a mechanism for drying moisture contained in the solvent separated by the color material aggregating action. As shown in FIG. 7, the drying unit 118 includes a drying drum (also referred to as “drying cylinder”) 176 and a solvent drying device 178. I have. Similar to the treatment liquid drum 154, the drying drum 176 includes a claw-shaped holding unit (gripper) 177 on the outer peripheral surface thereof.

  The solvent drying device 178 is disposed at a position facing the outer peripheral surface of the drying drum 176, and includes a plurality of halogen heaters 180 and hot air ejection nozzles 182 disposed between the halogen heaters 180. The recording medium 124 that has been dried by the drying unit 118 is transferred from the drying drum 176 to the fixing drum 184 of the fixing unit 120 via the intermediate conveyance unit 130.

(Fixing part)
The fixing unit 120 includes a fixing drum (also referred to as “fixing cylinder”) 184, a halogen heater 186, a fixing roller 188, and an in-line sensor 190. Like the processing liquid drum 154, the fixing drum 184 includes a claw-shaped holding unit (gripper) 185 on the outer peripheral surface thereof. The recording medium 124 is conveyed by the rotation of the fixing drum 184, and the recording surface is subjected to preliminary heating by the halogen heater 186, fixing processing by the fixing roller 188, and inspection by the inline sensor 190.

  The fixing roller 188 is a roller member that heats and pressurizes the dried ink to weld the self-dispersing polymer fine particles in the ink to form a film of the ink, and is configured to heat and press the recording medium 124. The Specifically, the fixing roller 188 is disposed so as to be in pressure contact with the fixing drum 184 and constitutes a nip roller with the fixing drum 184. By heating the recording medium 124 with the fixing roller 188, thermal energy equal to or higher than the Tg temperature (glass transition temperature) of the latex contained in the ink is applied, and the latex particles are melted. As a result, pressing and fixing are performed on the unevenness of the recording medium 124, and the unevenness of the image surface is leveled to obtain glossiness.

  In the embodiment shown in FIG. 7, only one fixing roller 188 is provided. However, a structure in which a plurality of fixing rollers 188 are provided may be used depending on the thickness of the image layer and the Tg characteristics of latex particles.

  On the other hand, the inline sensor 190 is a reading unit for measuring an ejection defect check pattern, image density, image defect, and the like for an image (including a test pattern) recorded on the recording medium 124, and is a CCD line sensor. Etc. apply.

  According to the fixing unit 120 configured as described above, the latex particles in the thin image layer formed by the drying unit 118 are heated and pressurized by the fixing roller 188 and are melted. Can be made.

  In addition, instead of the ink containing the high boiling point solvent and the polymer fine particles (thermoplastic resin particles), a monomer component that can be polymerized and cured by ultraviolet (UV) exposure may be contained. In this case, the inkjet recording apparatus 100 includes a UV exposure unit that exposes the ink on the recording medium 124 to UV light instead of the heat-pressure fixing unit (fixing roller 188) using a heat roller. As described above, when ink containing an actinic ray curable resin such as a UV curable resin is used, an actinic ray such as a UV lamp or an ultraviolet LD (laser diode) array is used instead of the fixing roller 188 for heat fixing. Means for irradiating are provided.

(Output section)
As shown in FIG. 7, a paper discharge unit 122 is provided following the fixing unit 120. The paper discharge unit 122 includes a discharge tray 192. Between the discharge tray 192 and the fixing drum 184 of the fixing unit 120, a transfer drum 194, a conveyance belt 196, and a stretching roller 198 are in contact with each other. Is provided. The recording medium 124 is sent to the conveyor belt 196 by the transfer drum 194 and discharged to the discharge tray 192. Although the details of the paper transport mechanism by the transport belt 196 are not shown, the recording medium 124 after printing is held at the front end of the paper by a gripper (not shown) gripped between the endless transport belt 196, and the transport belt 196. Is carried above the discharge tray 192.

  Although not shown in FIG. 7, in addition to the above-described configuration, the ink jet recording apparatus 100 of this example includes an ink storage / loading unit that supplies ink to each of the ink jet heads 172M, 172K, 172C, and 172Y, and a processing liquid. A means for supplying a processing liquid to the applying unit 114 and a head maintenance unit for cleaning each ink jet head 172M, 172K, 172C, 172Y (nozzle surface wiping, purging, nozzle suction, etc.) Are provided with a position detection sensor for detecting the position of the recording medium 124 and a temperature sensor for detecting the temperature of each part of the apparatus.

[Modification]
In the embodiment of FIG. 7, the ink jet recording apparatus of a method (direct recording method) that forms an image by directly ejecting ink droplets onto the recording medium 124 has been described, but the scope of application of the present invention is not limited to this, The present invention is also applied to an intermediate transfer type image forming apparatus that forms an image (primary image) on an intermediate transfer member and then transfers the image to a recording sheet in a transfer unit to form a final image. Can be applied.

  Further, in the above embodiment, an inkjet recording apparatus using a page-wide full-line head having a nozzle row having a length corresponding to the entire width of the recording medium (single-pass image for completing an image by one sub-scanning). However, the scope of application of the present invention is not limited to this, and an inkjet that performs image recording by scanning a plurality of heads while moving a short recording head such as a serial (shuttle scan) head. The present invention can also be applied to a recording apparatus.

<Means for moving head and paper relative to each other>
In the above-described embodiment, the configuration in which the drawing medium is conveyed with respect to the stopped head is exemplified. However, in implementing the present invention, a configuration in which the head is moved with respect to the stopped drawing medium is also possible. It is also possible to move both the drawing medium and the drawing medium.

<Application examples of the present invention>
In the above embodiment, application to an inkjet recording apparatus for graphic printing has been described as an example, but the scope of application of the present invention is not limited to this example. For example, a wiring drawing apparatus for drawing a wiring pattern of an electronic circuit, a manufacturing apparatus for various devices, a resist printing apparatus that uses a resin liquid as a functional liquid for ejection, a color filter manufacturing apparatus, and a material deposition material. The present invention can be widely applied to an inkjet system that draws various shapes and patterns using a liquid functional material, such as a fine structure forming apparatus that forms a structure.

  DESCRIPTION OF SYMBOLS 10 ... Inkjet head, 11 ... Nozzle surface, 12 ... Nozzle, 14 ... Pressure chamber, 16 ... Actuator, 20 ... 1st common flow path, 22 ... 1st separate flow path, 24 ... 1st atmosphere release hole, 26 ... Connection Port 30, second common channel 32, second individual channel 34, second air opening hole 36, connection port 42, diaphragm 51, meniscus 52, meniscus 100, inkjet recording apparatus 124 ... recording medium, 170 ... drawing drum, 300 ... head module, 310 ... supply side ink flow path, 320 ... recovery side ink flow path, 380 ... nozzle

Claims (11)

A plurality of nozzles for discharging droplets;
A plurality of pressure chambers provided corresponding to the plurality of nozzles;
An energy generating element that is disposed corresponding to each of the plurality of pressure chambers, and that applies a discharge force to the liquid in each pressure chamber;
A common flow path that communicates with the plurality of pressure chambers and supplies liquid to each pressure chamber;
For each of the pressure chambers, a throttle portion provided in an individual flow channel portion connecting between each pressure chamber and the common flow channel,
An air opening hole communicating with the common flow path and having an opening on a nozzle surface on which the plurality of nozzles are formed,
A liquid discharge head comprising: In claim 1,
A liquid ejection head, wherein Lb> La and Lb> Lc, where La is an inertance of the nozzle, Lb is an inertance of the throttle portion, and Lc is an inertance of the atmosphere opening hole. In claim 1 or 2,
If the flow resistance value from the common flow path to the opening of the nozzle is Ra, and the flow resistance value from the common flow path to the opening of the atmosphere opening hole is Rc, then Ra <Rc. Liquid discharge head. In any one of Claims 1 thru | or 3,
The liquid discharge head, wherein the atmosphere opening hole is connected to the common flow path by a straight flow path extending straight from the common flow path toward the nozzle surface. In any one of Claims 1 thru | or 4,
The air opening hole has a straight-shaped flow channel portion that extends straight from the common flow channel toward the nozzle surface, and the size of the opening surface increases from the flow channel portion toward the opening of the nozzle surface. A liquid discharge head having a counterbore portion. In any one of Claims 1 thru | or 5,
The liquid discharge head according to claim 1, wherein the number of the air opening holes provided in communication with the common flow path is smaller than the number of the pressure chambers connected in parallel to the common flow path. In any one of Claims 1 thru | or 6,
One end of the common flow path is provided with a connection port for connecting the common flow path to another flow path, and the other end is a terminal end of the common flow path,
The liquid discharge head, wherein the air release hole is disposed at least at the end portion of the common flow path. In any one of Claims 1 thru | or 7,
One end of the common channel is connected to another channel via a connection port,
Of the common flow path from the connection port to the terminal end of the other end, a larger number of the air opening holes are arranged on the terminal end side. In any one of Claims 1 thru | or 8,
An individual recovery channel individually communicating with each of the pressure chambers;
A common recovery flow path that communicates with the plurality of pressure chambers via the individual recovery flow paths and recovers liquid from each pressure chamber;
An air opening hole communicating with the common recovery flow path and having an opening on a nozzle surface on which the plurality of nozzles are formed,
A liquid discharge head comprising: A plurality of nozzles for discharging droplets;
A plurality of pressure chambers provided corresponding to the plurality of nozzles;
An energy generating element that is disposed corresponding to each of the plurality of pressure chambers, and that applies a discharge force to the liquid in each pressure chamber;
A first common flow path communicating with the plurality of pressure chambers and supplying a liquid to each pressure chamber;
A first connection port provided in the first common flow path for connecting the first common flow path to another first flow path;
A first individual flow path connecting between each pressure chamber and the common flow path for each pressure chamber;
A second individual flow path individually communicating with each of the pressure chambers;
A second common flow path that communicates with the plurality of pressure chambers via the second individual flow path, recovers liquid from each pressure chamber, or supplies liquid to each pressure chamber;
A second connection port provided in the second common flow path for connecting the second common flow path to another second flow path;
Of the first common flow path and the second common flow path, the flow resistance value from the first connection port to the pressure chamber is compared with the flow resistance value from the second connection port to the pressure chamber. An air opening hole having an opening on the nozzle surface where the plurality of nozzles are formed,
A liquid discharge head comprising: A liquid discharge head according to any one of claims 1 to 10,
Drive control means for generating a drive voltage signal to be applied to the energy generating element and controlling the discharge operation of the liquid discharge head;
Conveying means for relatively moving the liquid ejection head and the drawing medium;
An ink jet recording apparatus comprising:

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