JP2005305827A - Liquid ejection head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid ejection head which can be wired and manufactured easily even in a structure having nozzles arranged at a high density and is free from characteristic deterioration of piezoelectric elements due to humidity or the like in atmospheric air. <P>SOLUTION: The liquid ejection head comprises two piezoelectric thin film units, a pressure chamber block connected to each piezoelectric thin film unit, and a hollow portion forming block held in between the two piezoelectric thin film units. The piezoelectric thin film units are covered with a polymeric material except for a part of the first surface of a board. The hollow portion forming blocks are held in between the two boards so that mutual one surfaces of the boards face with each other, allowing the blocks to be partially connected to the boards to form a hollow part. The pressure chamber block has a surface with recessed parts, and is connected to the rear surface where no piezoelectric film for the piezoelectric thin film unit is formed, forming a pressure chamber for pressuring an ink and an ink channel. Tab wiring is arranged along the hollow portions. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid ejecting head such as an ink jet recording head, and more particularly, a piezoelectric body formed by hydrothermal synthesis that can easily take out and manufacture wiring, can arrange nozzles at high density, and has little characteristic deterioration. The present invention relates to a liquid ejecting head using a thin film.

  In recent years, personal computers have spread in the multimedia information society, and the demand for printers has increased accordingly. In particular, inkjet printers are rapidly expanding in market because they can produce high-quality color prints at a low price.

  There are various types of ink jets, which use a piezo element to convert mechanical vibration force into ink pressure waves and eject ink droplets, or heat the ink abruptly to generate bubbles, There are a method of ejecting ink droplets by pressure waves, a method of sucking and flying ink by electrostatic force, etc. Among them, a method using a piezoelectric thin film (piezo element) is a method of manufacturing a piezoelectric thin film (piezo element). Particular attention has been given to the progress of methods.

  Ink jet recording heads tend to be arranged with a plurality of nozzles of the head at a higher density in order to increase printing speed and precision. For example, Patent Document 1 discloses an ink jet recording head made of a piezoelectric ceramic material in which a plurality of nozzles are arranged in one head. FIG. 7 is a cross-sectional view illustrating a configuration example of an ink jet recording head using a piezoelectric element.

  In this ink jet recording head, a diaphragm made of a piezoelectric ceramic material sandwiched between a pair of drive electrodes, and pressure chambers and cavities are alternately provided between the diaphragms. Ink is supplied from an ink supply unit, pressurized in a pressure chamber, and discharged from a nozzle hole.

  In the ink jet recording head having such a configuration, the discharge energy generated by deforming the piezoelectric ceramic material by applying a voltage to the drive electrode sandwiched between the pressure chamber and the cavity is absorbed by the pressure chamber adjacent thereto. Therefore, droplets can be simultaneously ejected from the adjacent nozzles without being affected by the adjacent nozzles. Therefore, it is possible to control the ejection of individual nozzles and to obtain an ink jet recording head in which nozzles are arranged at a narrow pitch.

  Patent Document 2 describes a print head for an inkjet printer using a piezoelectric body formed by hydrothermal synthesis.

Japanese Unexamined Patent Publication No. 2-33311 Japanese Patent Laid-Open No. 8-118662

  However, in the conventional ink jet recording head shown in FIG. 7, it is necessary to efficiently deform the piezoelectric ceramic material in the portion including the drive electrode for discharging the ink, and the piezoelectric ceramic material between the pressure chamber and the cavity is very It is necessary to make it thinner.

  These inkjet recording heads including the drive plate are made of ceramic and are manufactured by laminating and firing green sheets. However, since the drive plate is thin and has a pressure chamber and a cavity, There is a problem that the head is deformed, the manufacturing yield is poor, and a head having sufficient characteristics cannot be obtained.

  In addition, a high electric field is applied to the drive plate containing the piezoelectric ceramic material, and when the moisture in the atmosphere is absorbed, the leakage current between the drive electrodes tends to increase, which eventually leads to dielectric breakdown. .

  Further, in the laminated type head shown in the cited document 2, there is no hollow portion corresponding to the cited document 1, and the piezoelectric driving units are laminated so as to overlap each other. It will also limit. In addition, there is no concern about the accuracy in the stacking thickness direction, and there is a concern about durability because the piezoelectric body is exposed.

  The present invention has been made in order to solve the above-described problems of the conventional ink jet recording head. The object of the present invention is to facilitate wiring and manufacturing even in a structure in which nozzles are arranged at high density, and can be used in the atmosphere. It is an object of the present invention to provide a liquid ejecting head that does not deteriorate the characteristics of a piezoelectric element due to the humidity inside.

  In order to achieve the above object, a liquid jet head according to the present invention includes two piezoelectric thin film units, a pressure chamber block joined to each of the piezoelectric thin film units, and a hollow portion sandwiched between the two piezoelectric thin film units. The piezoelectric thin film unit includes a conductive elastic substrate, a plurality of piezoelectric films disposed in a predetermined region on the first surface of the substrate, and the piezoelectric film on the piezoelectric film. The piezoelectric thin film unit is covered with a polymer material except for a part of the first surface of the substrate, and the driving electrode formed on the substrate and a tab wiring connected to the driving electrode. The cavity portion forming block is sandwiched so that the first surfaces of the two substrates face each other and bonded to a part of the substrate, whereby a plurality of piezoelectric film forming regions of the piezoelectric thin film units are formed. The cavity forming block; An enclosed cavity is formed, and the pressure chamber block has a recess formed on the front surface, and is bonded to the back surface of the piezoelectric thin film unit on which the piezoelectric film is not formed. A pressure chamber and an ink flow path for pressurizing ink are formed by the thin film unit, and the tab wiring is installed along the cavity.

  In particular, the piezoelectric film is desirably made by hydrothermal synthesis because it can be formed or thinned.

  In one embodiment of the present invention, the pressure chamber block and the cavity forming block are a polyimide sintered body or a laminate of polyimide films.

  In one embodiment of the present invention, the conductive elastic substrate is a Ni plate.

  Furthermore, an embodiment of the liquid jet head according to the present invention is characterized in that a nozzle block in which a plurality of nozzles are arranged is joined.

  Furthermore, an embodiment of the liquid ejecting head according to the invention is characterized in that an ink supply block for connecting the ink flow path and the external ink tank is joined.

  One aspect of the liquid jet head according to the present invention is characterized in that a plurality of liquid jet heads each including the two-layer piezoelectric thin film unit described above are further stacked.

  In one embodiment of the present invention, the polymer material coated on the first surface of the piezoelectric thin film unit is a hydrophobic resin, and the back surface of the piezoelectric thin film unit on which the piezoelectric film is not formed is coated. It is preferable that the polymer material formed is a hydrophilic resin. As the hydrophobic resin, a fluororesin is preferable, and as the hydrophilic resin, a polyimide resin is preferable.

  The liquid ejecting head according to the present invention includes a piezoelectric thin film unit formed on a substrate with a piezoelectric film and covered with a polymer material, and a block is formed so as to form a series of cavities between the two piezoelectric thin film units. Since the tab wiring is arranged using the hollow portion, wiring and manufacturing are easy even in a structure in which the nozzles are arranged at high density, and the piezoelectric element due to humidity in the atmosphere is used. A liquid jet head having no characteristic deterioration can be obtained.

  Hereinafter, a liquid jet head according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view illustrating a configuration of a liquid jet head according to an embodiment of the present invention. 2 is a cross-sectional view taken along the line X-X ′ of FIG. 1, and FIG. 3 is a partially enlarged view of the cross section taken along the line Y-Y ′ of FIG. 1. 1 to 3, the liquid jet head 1 includes two piezoelectric thin film units 2, a pressure chamber block 3 joined to each of the piezoelectric thin film units 2, and a hollow portion sandwiched between the two piezoelectric thin film units 2. Block 4 (or 4 '). In the embodiment of FIG. 2, a nozzle block 6 in which nozzles 61 are further formed, and an ink supply block 7 for supplying ink from an ink tank are also illustrated.

  The piezoelectric thin film unit 2 includes a conductive elastic substrate 21, a plurality of piezoelectric films 22 formed on a predetermined region of the first surface of the elastic substrate 21, and drive electrodes 23 formed on the piezoelectric film 22. And a tab wiring 24 connected to the drive electrode 23. The piezoelectric thin film unit 2 is covered with a polymer material 25 except for a part of the first surface of the substrate 21. That is, the first surface of the piezoelectric thin film unit 2 is covered with the polymer material 25 except for the portion where the hollow block 4, 4 'and the conductive elastic substrate 21 are in contact with each other. On the back surface of the unit 2 (the surface opposite to the first surface of the substrate), the conductive elastic substrate 21 is covered with the polymer material 25 or the polymer sheet. The piezoelectric film 22 is preferably formed by hydrothermal synthesis because the adhesion strength with the substrate is high without sintering and a pre-oriented piezoelectric film can be obtained by an easy process. The same effect can be obtained by attaching a thin film piezoelectric body.

  The hollow block 4, 4 'is formed of the conductive elastic body so as to form a series of hollow portions communicating with the outside so that the portions of the two piezoelectric thin film units 2 on which the plurality of piezoelectric films are formed face each other and do not contact each other. Bonded between the substrates 21. In other words, the cavity block 4, 4 'is sandwiched so that the first surfaces of the two substrates 21 face each other and bonded to a part of the substrate 21, whereby the liquid jet head of the present invention is A cavity 5 surrounded by a plurality of piezoelectric film forming regions of the piezoelectric thin film units 2 and the cavity blocks 4 and 4 ′ is formed. A tab wiring 24 is installed along the cavity 5 and is connected to an external piezoelectric drive circuit (not shown).

  The pressure chamber block 3 is formed with a pressure chamber 32 for pressurizing ink and a recess 31 for forming an ink flow path 33, and the back surface of the piezoelectric thin film unit 2 where the piezoelectric film 22 is not formed. The pressure chamber 32 and the ink flow path 33 for pressurizing ink are formed by the concave portion 31 and the piezoelectric thin film unit 2.

  As described above, the liquid jet head 1 according to the present invention has the ink pressure chamber 3 formed on one side of the piezoelectric thin film unit 2 and the hollow portion 5 communicating between the two piezoelectric thin film units.

  The operation of the liquid jet head will be briefly described with reference to FIG. Since the piezoelectric film 22 is formed on the conductive elastic substrate 21, a voltage is generated between the conductive elastic substrate 21 serving as a common electrode and the drive electrode 23 (that is, in the thickness direction of the piezoelectric film). When applied, in a normal driving method, the piezoelectric film 22 extends in the thickness direction of the piezoelectric film 22 and contracts in a direction parallel to the substrate. For this reason, in the region where the piezoelectric film is formed, the substrate 21 and the piezoelectric film 22 are bent toward the pressure chamber 32 in contact with the substrate, and the ink in the pressure chamber 32 is pressurized to the nozzle side. The ink is pushed out and ejected from the nozzle 61. Ink is supplied through an ink supply block 7.

  As described above, since the liquid ejecting head according to the present invention has the cavity portion 5, even if one piezoelectric film 22 vibrates and applies pressure to the pressure chamber 32, the pressure chamber 32 faces the pressure chamber 32. Since there is no influence, a liquid jet head without noise can be provided. In addition, the cavity 5 is formed over a plurality of piezoelectric film 22 formation regions, communicates with the outside, and can be formed with a simple configuration, so that a drive signal is sent to the drive electrode 23 of each piezoelectric film 22. Since the tab wiring 24 can be installed using the hollow portion 5, wiring and manufacturing are easy. The common electrode which is the other electrode of the piezoelectric film 22 uses the conductive elastic substrate 21, and the substrate 21 is directly connected to the outside, so that no new wiring is required.

  In addition, since the piezoelectric film 22, the drive electrode 23, and a part of the conductive elastic substrate 21 facing the hollow portion 5 are covered with the polymer material, they are not easily affected by humidity and the like, and the characteristics are deteriorated. Can be avoided. In particular, the polymer material coated on the first surface of the piezoelectric thin film unit is preferably a hydrophobic resin, which makes it less susceptible to humidity and the like, and avoids deterioration of characteristics. Examples of the hydrophobic resin include a fluororesin, and a tetrafluoroethylene resin is particularly preferable.

  Further, the side (second surface side) where the pressure chamber 32 of the conductive elastic substrate 21 is formed is covered with a polymer material 25 or a polymer sheet is adhered thereto, thereby preventing the substrate from being deteriorated by ink or the like. In addition, the affinity with ink can be increased and the generation of bubbles can be prevented. Since the pressure chamber is filled with ink, it is necessary to have a complete gap immediately after manufacturing the ink jet recording head. In addition, when ink is filled in the pressure chamber and discharged from the nozzle, if bubbles remain in the ink pressure chamber, the deformation energy of the drive unit is used only to compress the bubbles, and ink is discharged from the nozzles. I can't. In order to fill ink without leaving bubbles in the ink pressure chamber, it is preferable that the inner wall of the ink pressure chamber has a characteristic that the ink gets wet well, or the ink pressure chamber has a shape in which bubbles do not easily remain. For this purpose, it is preferable to provide a hydrophilic film on the inner surface of the ink pressure chamber. That is, the polymer material coated on the back surface (second surface) where the piezoelectric film of the piezoelectric thin film unit is not formed is preferably a hydrophilic resin. Examples of the hydrophilic resin include an epoxy resin and a polyimide resin, and a polyimide resin is particularly preferable. As the polymer material, a polymer sheet that has been a polymer sheet from the beginning may be bonded.

  Further, in the embodiment of FIGS. 1 to 3, the piezoelectric films of the two piezoelectric thin film units are arranged so as to face each other, but it is also possible to form the liquid jet head by shifting the piezoelectric films so as not to face each other. It is. Accordingly, the two rows of nozzles can be arranged so as to complement each other rather than being in the same position in the upper and lower sides, and the degree of freedom of design is widened, and the nozzles can be arranged at high density.

  As described above, the liquid jet head of the present invention sandwiches a block so as to form a series of hollow portions between a piezoelectric thin film unit coated with a polymer material and manufactured by hydrothermal synthesis, and the two piezoelectric thin film units, By arranging the tab wiring using the hollow portion, even in the structure where the nozzles are arranged at high density, wiring and manufacturing are easy, and the characteristics of the piezoelectric element deteriorate due to humidity in the atmosphere. There can be no liquid jet head. Further, unlike the case of manufacturing from a ceramic green sheet, firing or the like is unnecessary.

  Examples of the pressure chamber block and the cavity forming block include a resin block and a ceramic block. Examples of the resin block include polyurethane, polyamide, polycarbonate and the like, and a polyimide sintered body is particularly preferable. Since the polyimide sintered body has heat resistance, there is an effect that it is not deformed even if heat treatment is performed during the manufacturing process. The pressure chamber block and the cavity forming block may be a laminate in which resin films are laminated. Examples of the resin for the resin film include polyurethane, polyamide, polycarbonate and the like, and polyimide is particularly preferable.

  The conductive elastic substrate of the present invention may be formed by forming a conductive thin film on plastic or ceramic in addition to a metal plate or an alloy plate. In particular, the conductive elastic substrate of the present invention is preferably a Ni plate. The Ni substrate is an alkali-resistant material and is useful as a substrate for a hydrothermally synthesized PZT piezoelectric film using strong alkali.

  As shown in FIG. 1, the liquid ejecting head of the present invention can eject liquid with uniform and stable characteristics by joining nozzle blocks each having a plurality of nozzles. In the liquid ejecting head of the present invention, the end of the ink flow path may be directly used as the ejecting nozzle without using the nozzle block.

  Further, as shown in FIG. 1, the liquid ejecting head according to the present invention has a plurality of ink supply blocks for joining ink from an external ink tank (not shown) to the present liquid ejecting head. A necessary type of ink can be selected and supplied to the ink chamber.

  In the liquid jet head of the present invention described above, the jet head composed of two nozzle rows is one unit. As shown in FIG. 4, a plurality of the jet heads are further stacked in the vertical direction. It is possible to increase the number of nozzle rows. Accordingly, it is possible to provide a liquid ejecting head having a large number of nozzles in the height direction and the horizontal direction. Since the tab wiring is always led out from the cavity, it is not particularly complicated by the lamination. Furthermore, in the case of stacking, it is possible to change the nozzle arrangement by shifting in the nozzle pitch direction.

  Next, a method for manufacturing a liquid jet head according to the present invention will be described with reference to the drawings. FIG. 4 is a cross-sectional view of a piezoelectric thin film unit produced by forming a piezoelectric film on a Ni substrate by a hydrothermal synthesis method. The piezoelectric thin film unit 1 can be manufactured as follows using a hydrothermal synthesis method. First, a piezoelectric film (for example, PZT film 223) is formed on the Ti film 221 by a hydrothermal synthesis method as follows. That is, first, a resist is spin-coated on a conductive elastic substrate (for example, the Ni substrate 211), and the resist in a predetermined region is removed by a photolithography technique. Next, a titanium film 221 is formed at a predetermined position on a substrate (for example, Ni substrate 211) by sputtering to a thickness of about 0.5 to 1 μm, and the resist is removed. Thereby, the Ti film 221 can be formed in the region where the piezoelectric film (for example, the PZT film 223) is formed.

Next, a PZT seed crystal 222 is formed on the substrate obtained in this step (for example, the Ni substrate 211) by the following method. Prepared by mixing lead nitrate (Pb (NO ₃ ) ₂ ) aqueous solution, zirconium oxychloride (ZrCl ₂ · 8H ₂ O) aqueous solution, strontium nitrate (Sr (NO ₃ ) ₂ ) and potassium hydroxide (KOH) aqueous solution The aforementioned substrate (for example, Ni substrate 211) is immersed in the reaction solution, and hydrothermal treatment is performed at 150 ° C. In this reaction, a Ti source eluted from the titanium film 221 is reacted with a Pb source and a Zr source in the reaction solution, so that a piezoelectric thin film seed crystal (for example, PZT seed crystal 222) has a thickness of 0.1 μm on the surface of the titanium layer 221. It will be formed.

Next, a piezoelectric film (for example, PZT film 223) is grown on the piezoelectric thin film seed crystal (for example, PZT seed crystal 222) obtained above by a hydrothermal synthesis method. In this embodiment, the reaction solution used in this hydrothermal reaction is a lead nitrate (Pb (NO ₃ ) ₂ ) aqueous solution, a zirconium oxychloride (ZrCl ₂ .8H ₂ O) aqueous solution, or titanium tetrachloride (TiCl _4). ) A mixture of an aqueous solution and a potassium hydroxide (KOH) aqueous solution can be used.

  As described above, in the method for forming a piezoelectric thin film element according to the present invention, a piezoelectric film (eg, PZT film 223) can be selectively formed only on a piezoelectric thin film seed crystal (eg, PZT seed crystal 222). As a result, a piezoelectric film (for example, PZT film 223) can be selectively formed in a predetermined region by a hydrothermal synthesis method.

  In this way, after a piezoelectric film (for example, PZT film 223) is formed on a conductive elastic substrate (for example, Ni substrate 211), a predetermined film is formed on the piezoelectric film (for example, PZT film 223) by photolithography. A drive electrode 23 made of an Au electrode is formed in the pattern. The tab electrode 24 is used for wiring with the drive electrode. FIG. 5 shows a schematic diagram in which tab wiring is provided on the drive electrode on the piezoelectric film. The drive electrode 23 and the tab wiring 24 are connected by forming a contact hole 241 at a predetermined position of the tab corresponding to the predetermined electrode and connecting with a conductive resin.

  Next, a region on the conductive elastic substrate in contact with the cavity forming block is masked with a metal mask, and a polymer material is spray-coated. As the polymer material, a fluororesin is preferable.

  Subsequently, a fluorine-based or sulfone-based polymer material is applied to the second surface (the back surface of the first surface) of the conductive elastic substrate, or a polymer sheet is adhered. An epoxy resin can be used as the adhesive. The piezoelectric thin film unit can be manufactured as described above.

  Next, a method for manufacturing the liquid jet head of the present invention using the piezoelectric thin film unit will be described with reference to FIG. The pressure chamber block 3 is a block in which a recess 31 for the ink flow path 33 and the pressure chamber 32 is formed, and the piezoelectric film 22 of the piezoelectric thin film unit 2 is formed on the surface where the recess 31 is formed. Bonded with an adhesive in accordance with the surface that is not formed (corresponding to the back surface of the first surface of the substrate 21, the second surface), that is, the surface on which the polymer sheet of the second surface of the conductive elastic substrate is formed. Let An epoxy resin can be used as the adhesive. Two such pressure chamber blocks 3 and piezoelectric thin film units joined are prepared.

  Next, the polymer material 25 of the conductive elastic substrate 21 on the side (front surface, first surface) of the piezoelectric thin film unit 2 where the two pressure chamber blocks 3 are joined is formed. The liquid ejecting head 1 having a structure in which the cavity portion forming blocks 4 and 4 ′ are bonded to the portions where no coating is applied, and the cavity portion 5 and the cavity portion block 4 are sandwiched between the two piezoelectric thin film units 2. Can be formed. It is easy to manufacture the cavity block 4 as two blocks, that is, a nozzle side cavity block 4 installed on the side close to the nozzle and an ink supply side cavity block 4 ′ close to the ink supply side. Therefore, these two blocks may be formed as one hollow block having a structure in which a connecting portion is provided to such an extent that the hollow portion 5 is not blocked. As described above, the liquid jet head of the present invention can be manufactured.

1 is a perspective view of an ink jet recording head according to an embodiment of the present invention. It is X-X 'sectional drawing of FIG. FIG. 2 is a Y-Y ′ sectional view of FIG. 1. It is sectional drawing of the piezoelectric thin film unit concerning embodiment of this invention. It is the schematic of the piezoelectric thin film unit which shows the connection method of the tab wiring of this invention. 1 is a perspective view illustrating an embodiment of a liquid jet head according to the present invention. It is principal part sectional drawing which shows the structure of the conventional inkjet recording head.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid ejecting head 2 Piezoelectric thin film unit 21 Conductive elastic substrate (common electrode)
211 Ni substrate 22 Piezoelectric film 221 Titanium film 222 PZT seed crystal film 223 PZT film 23 Drive electrode 24 Tab wiring 241 Contact hole 25 Polymer material 3 Pressure chamber block 31 Recess 32 Pressure chamber 33 Ink flow path 4, 4 ′ cavity Part block 5 Cavity part 6 Nozzle block 61 Nozzle 7 Ink supply block

Claims (9)

A liquid ejecting head comprising two piezoelectric thin film units, a pressure chamber block bonded to each of the piezoelectric thin film units, and a cavity forming block sandwiched between the two piezoelectric thin film units;
The piezoelectric thin film unit includes a conductive elastic substrate, a plurality of piezoelectric films disposed in a predetermined region of the first surface of the substrate, a drive electrode formed on the piezoelectric film, and a drive electrode Connected tab wiring,
The piezoelectric thin film unit is coated with a polymer material except for a part of the first surface of the substrate,
The hollow portion forming block is sandwiched so that the first surfaces of the two substrates face each other and bonded to a part of the substrate, whereby a plurality of piezoelectric film forming regions of the piezoelectric thin film units are formed. And a hollow portion surrounded by the hollow portion forming block,
The pressure chamber block has a concave portion formed on the front surface, and is bonded to the back surface of the piezoelectric thin film unit on which the piezoelectric film is not formed, and pressure for pressurizing ink by the concave portion and the piezoelectric thin film unit. Chamber and ink flow path are formed,
The liquid ejecting head according to claim 1, wherein the tab wiring is disposed along the hollow portion.   The liquid ejecting head according to claim 1, wherein the piezoelectric film is a piezoelectric body formed by hydrothermal synthesis.   The liquid ejecting head according to claim 1, wherein the pressure chamber block and the cavity forming block are polyimide sintered bodies.   The liquid ejecting head according to claim 1, wherein the pressure chamber block and the cavity forming block are a laminate of polyimide films.   The liquid ejecting head according to claim 1, wherein the conductive elastic substrate is a Ni plate.   The liquid jet head according to claim 1, wherein nozzle blocks each having a plurality of nozzles are joined.   The liquid ejecting head according to claim 1, wherein an ink supply block for connecting the ink flow path and the external ink tank is joined.   A liquid jet head comprising a plurality of the liquid jet heads according to claim 1 laminated.   The polymer material coated on the first surface of the piezoelectric thin film unit is a hydrophobic resin, and the polymer material coated on the back surface of the piezoelectric thin film unit on which the piezoelectric film is not formed is a hydrophilic resin. The liquid jet head according to claim 1, wherein

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