JP5347609B2 - Liquid ejection head and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that solder joint strength decreases or a tact time decreases when laser joining is carried out using a large head even if the width of a common wiring electrode of a flexible substrate is equivalent to the width of an individual wiring electrode. <P>SOLUTION: A non-drive piezoelectric element column 12Ba wider than a drive piezoelectric element column 12A is formed at one end of a piezoelectric element member 12, and a common electrode portion 25 connected with the common electrodes 24 of all the drive piezoelectric element columns 12A is provided on the end face of the non-fr piezoelectric element column 12Ba at the individual electrode side. The individual wiring electrodes 31A of an FPC 15 are joined with an electrical connection member, i.e. solder 32, to the individual electrodes 23 of the drive piezoelectric element columns 12A of the piezoelectric element member 12, and electrically connecting the electrodes. Furthermore, the common wiring electrode 31B of the FPC 15 is similarly joined with the solder 32 to the common electrode portion 25 provided in the non-drive piezoelectric element column 12Ba at one end side of the piezoelectric element member 12, and electrically connecting the electrodes. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a liquid discharge head and an image forming apparatus.

  As an image forming apparatus such as a printer, a facsimile, a copying machine, a plotter, or a complex machine of these, for example, a liquid discharge recording type image forming using a recording head composed of a liquid discharge head (droplet discharge head) that discharges ink droplets. As an apparatus, an ink jet recording apparatus or the like is known. This liquid discharge recording type image forming apparatus means that ink droplets are transported from a recording head (not limited to paper, including OHP, and can be attached to ink droplets and other liquids). Yes, it is also ejected onto a recording medium or a recording medium, recording paper, recording paper, etc.) to form an image (recording, printing, printing, and printing are also used synonymously). And a serial type image forming apparatus that forms an image by ejecting liquid droplets while the recording head moves in the main scanning direction, and a line type head that forms images by ejecting liquid droplets without moving the recording head There are line type image forming apparatuses using

  In the present application, the “image forming apparatus” of the liquid discharge recording method is an apparatus that forms an image by discharging liquid onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, or the like. In addition, “image formation” means not only giving an image having a meaning such as a character or a figure to a medium but also giving an image having no meaning such as a pattern to the medium (simply It also means that a droplet is landed on a medium). “Ink” is not limited to ink, but is used as a general term for all liquids capable of image formation, such as recording liquid, fixing processing liquid, and liquid. DNA samples, resists, pattern materials and the like are also included.

  Conventionally, as a liquid discharge head, a piezoelectric element, particularly a stacked piezoelectric element in which piezoelectric layers and internal electrodes are alternately stacked, is used as pressure generating means (actuator means) for generating pressure to pressurize ink that is liquid in a liquid chamber. Using a so-called piezoelectric actuator that deforms an elastically deformable diaphragm that forms the wall surface of the liquid chamber by displacement in the d33 or d31 direction of the multilayer piezoelectric element, and discharges the liquid droplet by changing the volume / pressure in the liquid chamber The piezoelectric head used is known.

  In such a piezoelectric head, for example, using a laminated piezoelectric element, an FPC (flexible substrate) is provided for each of an external electrode (also referred to as an end face electrode) serving as a common electrode with internal electrodes drawn to the end face and an external electrode serving as an individual electrode. Common wiring electrodes and individual wiring electrodes of wiring members such as flexible printed cables and flexible wiring boards) are joined, and a drive signal corresponding to an image signal is given to each piezoelectric element.

  In this case, as a method of electrically connecting the wiring electrode provided on the wiring member such as FPC and the external electrode of the piezoelectric element, for example, a metal is interposed between both electrodes, and both electrodes are made of a laser such as glass. A method in which both electrodes are welded and joined together by melting the metal with a laser beam by bonding with a transmission rigid member, and both electrodes are made of metal by melting the metal by thermocompression bonding such as a heater. A method of welding and joining is known.

  By the way, since the amount of current flowing through the common electrode of the piezoelectric head is much larger than the amount of electricity flowing through the individual electrode, a common electrode portion that has been connected to the common external electrodes of a plurality of piezoelectric elements at both ends or one end is conventionally provided. The width of the piezoelectric element provided with the common electrode portion is wider than the width of the individual piezoelectric element corresponding to each nozzle, and the width of the common wiring electrode of the wiring board such as FPC is connected to the individual electrode. It is made wider than the width of the above (Patent Document 1).

  However, when the common electrode portion (connection portion between the common electrode portion and the common wiring electrode) becomes wide, the amount of electrical connection members (solder, etc.) to be used becomes the individual electrode portion (connection portion between the individual external electrode and the individual wiring electrode). ) And it is necessary to give a large amount of heat at the time of connection. Similarly, since the common electrode portion is wider than the individual electrode portion in terms of the wiring electrode width and the piezoelectric element width, the amount of heat flowing to the wiring electrode and the like when connecting the common electrode portion increases, and it is necessary to apply a large amount of heat in this respect as well.

  Therefore, the common electrode portion is divided into two and each connection width is made equal to the width of the individual electrode (Patent Document 2), the common wiring electrode of the wiring board is comb-shaped, or the common wiring electrode length is shortened. (Patent Document 3) is known.

JP 2006-175845 A Japanese Patent Laid-Open No. 10-202876 JP 2002-86739 A

  By the way, if it is joining to the electrode part formed in the single board | substrate like patent document 2 and patent document 3, since there is almost no difference in the heat capacity of a common electrode formation part and an individual electrode formation part, it is an electrode of a wiring means. It is possible to improve the difference in the joining state by making the widths equal, but when joining the wiring means directly to the piezoelectric element, the piezoelectric element to which the individually cut individual electrodes are connected and the large width It has been clarified that the piezoelectric elements on which the common electrode is formed have completely different heat capacities, and even if the electrode width of the wiring board is formed to be the same width, sufficient solder joint strength cannot be ensured in the common electrode portion.

  This reduction in bonding strength becomes a greater problem as the liquid discharge head becomes larger. In other words, a small head can be joined by heating with a heater chip, and the entire joining surface can be heated longer to compensate for the difference in heat capacity, but the head is longer. When the size and size are increased, joining with the heater chip becomes difficult. Therefore, laser bonding is performed as described above. This is a method in which electrodes are bonded one by one by scanning a laser, and there is an advantage that the flexible substrate can be restrained from being stretched and the flexible substrate can be easily bonded to a large head.

  However, in laser bonding, since the heating time per electrode is short, the heat from the laser is absorbed by the piezoelectric element of the common electrode portion having a large heat capacity, and the electrode width of the wiring means is made equal to that of the individual electrode. However, the solder does not melt and cannot be joined.

  In this case, it is conceivable to extend the laser irradiation time only when bonding with the common electrode part, but this cannot increase the tact time and suppress the expansion of the flexible substrate, which is the greatest feature of laser bonding. Such problems occur.

  The present invention has been made in view of the above problems, and prevents an increase in tact time when a wiring member is bonded to a piezoelectric element, particularly when a wiring member is laser bonded to a piezoelectric element of a long head. It is an object to enable bonding in a short time without sacrificing the advantages of laser bonding.

In order to solve the above-described problem, a liquid discharge head according to the present invention includes:
A plurality of piezoelectric elements corresponding to a plurality of pressurized liquid chambers through which nozzles for discharging droplets communicate;
A wiring member for supplying a drive signal to the plurality of piezoelectric elements,
The individual electrodes of the plurality of piezoelectric elements are connected to individual wiring electrodes provided on the wiring member by an electrical connection member. The common electrode portion common to the plurality of piezoelectric elements is provided to the wiring member by an electrical connection member. Connected common wiring electrodes,
The common electrode portion is formed to have a larger area than the individual electrodes,
The common wiring electrode of the wiring member has a plurality of connection portions whose width in the nozzle arrangement direction is narrower than the width of the individual wiring electrode in the connection portion connected to the common electrode portion,
The area of the common wiring electrode per unit area of the wiring member is smaller than the area of the individual wiring electrode per unit area of the wiring member.

  Here, the amount per unit area of the electrical connection member that connects the common wiring electrode of the wiring member and the common electrode portion is the electrical connection member that connects the individual wiring electrode of the wiring member and the individual electrode. It is possible to make the configuration smaller than the amount per unit area.

  Further, the common wiring electrode of the wiring member is branched into the plurality of connection portions at a portion connected to the common electrode portion, and each branched connection portion is arranged at the same pitch as the individual wiring electrodes. And can.

  In addition, the plurality of connection portions of the common wiring electrode of the wiring member may have a length that is twice or more as long as the length connected to the common electrode portion.

  Further, the thickness of the electrical connection member that connects the common wiring electrode of the wiring member and the common electrode portion is greater than the thickness of the electrical connection member that connects the individual wiring electrode of the wiring member and the individual electrode. Can be made thin.

  An image forming apparatus according to the present invention includes the liquid ejection head according to the present invention.

  According to the liquid ejection head according to the present invention, the common electrode portion is formed to have a larger area than the individual electrode, and the common wiring electrode of the wiring member has an individual width in the nozzle arrangement direction at the connection portion connected to the common electrode portion. Since it has a plurality of connection parts narrower than the width of the wiring electrode, the area of the common wiring electrode per unit area of the wiring member is smaller than the area of the individual wiring electrode per unit area of the wiring member. Even when joining, heating by the laser can be concentrated and joining can be performed even at the same speed scanning, and the wiring member is joined to the large head without sacrificing the tact time and the merit of laser joining. Will be able to.

  According to the image forming apparatus of the present invention, since the liquid discharge head according to the present invention is provided, stable image formation can be performed.

FIG. 3 is an exploded perspective view illustrating an example of a liquid discharge head according to the first embodiment of the present invention. It is sectional explanatory drawing along the liquid chamber longitudinal direction of the head. It is sectional explanatory drawing of the bipitch structure along the liquid chamber transversal direction of the head. It is sectional explanatory drawing of the normal pitch structure along the liquid chamber transversal direction of the head. It is typical explanatory drawing in alignment with the direction orthogonal to the nozzle arrangement direction with which it uses for description of the electrode connection structure of a piezoelectric element member and FPC. It is a principal part plane explanatory view of a joined state similarly. It is a principal part front explanatory drawing of a piezoelectric element member and FPC similarly. It is typical explanatory drawing in alignment with the direction orthogonal to the nozzle arrangement direction with which it uses for description of the electrode connection structure of a comparative example. It is a principal part front explanatory drawing of a piezoelectric element member and FPC similarly. It is principal part plane explanatory drawing of the joining state along the direction orthogonal to the nozzle arrangement direction of another example. It is a principal part front explanatory drawing of a piezoelectric element member and FPC similarly. 1 is an overall configuration diagram illustrating an example of an image forming apparatus according to the present invention. Similarly it is principal part plane explanatory drawing.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. An example of a liquid discharge head including a piezoelectric actuator according to the present invention will be described with reference to FIGS. 1 is an exploded perspective view of the head, FIG. 2 is a cross-sectional explanatory view along a direction (liquid chamber longitudinal direction) orthogonal to the nozzle arrangement direction of the head, and FIGS. 3 and 4 are nozzle arrangement directions of the head. It is sectional explanatory drawing of the different example along (liquid chamber transversal direction).

  The liquid discharge head includes a flow path substrate (liquid chamber substrate) 1 formed of a SUS substrate, a vibration plate member 2 bonded to the lower surface of the flow path substrate 1, and a nozzle plate 3 bonded to the upper surface of the flow path substrate 1. And a plurality of nozzles 4 for ejecting droplets (liquid droplets) by these, respectively, as a plurality of liquid chambers (pressurized liquid chamber, pressure chamber, Also referred to as a pressure chamber, a flow path, etc.) 6, a fluid resistance portion 7 that also serves as a supply path for supplying ink to the liquid chamber 6, and a communication portion 8 that communicates with the liquid chamber 6 via the fluid resistance portion 7. Ink is supplied from a common liquid chamber 10 formed in a frame member 17 to be described later to the communication portion 8 through a supply port 9 formed in the diaphragm member 2.

  The flow path substrate 1 is configured by bonding a flow path plate 1A and a communication plate 1B. The flow path substrate 1 is formed by etching the SUS substrate using an acidic etchant or machining such as punching (pressing) to open openings such as the communication path 5, the pressurized liquid chamber 6, and the fluid resistance portion 7. Each is formed.

  The diaphragm member 2 has each vibration region (diaphragm portion) 2a that forms a wall surface corresponding to each liquid chamber 6, and an island-shaped convex portion on the outer side of the vibration region 2a (on the side opposite to the liquid chamber 6). 2b is provided, and upper end surfaces (joint surfaces) of the piezoelectric element columns 12A and 12B of the laminated piezoelectric element member 12 as driving means (actuator means, pressure generating means) for deforming the vibration region 2a on the island-shaped convex portions 2b. Are joined. The lower end surface of the multilayer piezoelectric element member 12 is joined to the base member 13.

  Here, the piezoelectric element member 12 is formed by alternately laminating piezoelectric material layers 21 and internal electrodes 22 a and 22 b, and the internal electrodes 22 a and 22 b are respectively substantially perpendicular to the end face, that is, the diaphragm 2 of the piezoelectric element 12. By pulling out to the side surface, connecting to the end face electrodes (external electrodes) 23, 24 formed on the side face, and applying a voltage between the end face electrodes (external electrodes) 23, 24, displacement in the stacking direction occurs. Here, the external electrode 23 is used as an individual external electrode (individual electrode), and the external electrode 24 is used as a common external electrode (common electrode).

  The piezoelectric element member 12 is formed by forming grooves by half-cut dicing and forming a required number of piezoelectric element columns 12A and 12B in a comb-like shape at a predetermined interval with respect to one piezoelectric element member. In this example, each of the piezoelectric element columns 12A and 12B becomes “a plurality of piezoelectric elements”.

  The piezoelectric element columns 12A and 12B of the piezoelectric element member 12 are the same, but the piezoelectric element column that is driven by giving a drive waveform is used as a drive piezoelectric element column 12A, and a piezoelectric element that is used as a simple support without giving a drive waveform. The element columns are distinguished as non-driving piezoelectric element columns 12B. In this case, as shown in FIG. 3, a bi-pitch configuration in which driving piezoelectric element columns 12A and non-driving piezoelectric element columns 12B are used alternately, or all piezoelectric element columns are driven piezoelectric element columns as shown in FIG. Any of the normal pitch configurations used as 12A can be employed.

  The piezoelectric element member 12 is connected to an FPC 15 as a flexible wiring member for giving a driving signal to the driving piezoelectric element column 12A. The FPC 15 is bonded to the base member 13 with a hot melt adhesive 16 in the vicinity of the piezoelectric element member 12.

  The nozzle plate 3 is formed from a nickel (Ni) metal plate, and is manufactured by an electroforming method (electroforming). In this nozzle plate 3, nozzles 4 having a diameter of 10 to 35 μm are formed corresponding to the respective liquid chambers 6 and bonded to the flow path plate 1 with an adhesive. A water repellent layer is provided on the droplet discharge side surface (surface in the discharge direction: discharge surface or surface opposite to the liquid chamber 6 side) of the nozzle plate 3.

  This head is configured to pressurize the ink in the liquid chamber 6 by using the displacement in the d33 direction as the piezoelectric direction of the piezoelectric element member 12, and the droplet discharge direction is the flow direction of the recording liquid in the liquid chamber 6. The side shooter method is different from that of droplets. By adopting the side shooter system, the size of the piezoelectric element member 12 becomes approximately the size of the head, and the miniaturization of the piezoelectric element member 12 can be directly linked to the miniaturization of the head, and the head can be easily miniaturized.

  Further, a frame member 17 formed by injection molding with an epoxy resin or polyphenylene sulfite is joined to the outer peripheral side of the actuator portion composed of the piezoelectric element member 12, the base member 13, the FPC 15, and the like. The frame member 17 is formed with the common liquid chamber 10 described above, and further, a supply port 19 for supplying a recording liquid from the outside to the common liquid chamber 10 is formed. It is connected to an ink supply source such as an ink cartridge.

  In the liquid ejection head configured as described above, for example, when driven by a punching method, a drive pulse voltage of 20 to 50 V is selectively applied to the drive piezoelectric element column 12A according to an image recorded from a control unit (not shown). When applied, the driving piezoelectric element column 12A to which the pulse voltage is applied is displaced to deform the vibration region 2a of the vibration plate 2 in the direction of the nozzle plate 3, and the inside of the liquid chamber 6 is changed by the volume (volume) change of the liquid chamber 6. A liquid droplet is discharged from the nozzle 4 of the nozzle plate 3 by pressurizing the liquid. As the liquid droplets are discharged, the pressure in the liquid chamber 6 decreases, and a slight negative pressure is generated in the liquid chamber 6 due to the inertia of the liquid flow at this time. Under this state, by turning off the application of voltage to the driving piezoelectric element column 12A, the diaphragm 2 returns to the original position and the liquid chamber 6 becomes the original shape, so that further negative pressure is generated. To do. At this time, the recording liquid is filled from the common liquid chamber 10 into the liquid chamber 6, and droplets are ejected from the nozzles 4 in response to the next drive pulse application.

  In addition to the above-described pushing, the liquid ejection head is not limited to the pulling method (a method of releasing the diaphragm 2 from the pulled state and pressurizing it with a restoring force), and the pulling-pushing method (the diaphragm 2 at the intermediate position). It is also possible to drive by pulling from this position and then extruding.

  Next, an electrode connection structure between the piezoelectric element member and the FPC in this liquid discharge head will be described with reference to FIGS. 5 is a schematic explanatory diagram along a direction orthogonal to the nozzle arrangement direction, FIG. 6 is a principal plan explanatory diagram of the joined state, and FIG. 7 is a principal front explanatory diagram of the piezoelectric element member and the FPC. Here, all the piezoelectric element columns of the piezoelectric element member 12 are illustrated in a normal pitch configuration used as the driving piezoelectric element column 12A.

  A wide non-driving piezoelectric element column 12Ba is formed at one end (or both ends) of the piezoelectric element member 12, and the common electrode of all the driving piezoelectric element columns 12A is formed on the individual electrode side end face of the non-driving piezoelectric element column 12Ba. A common electrode part 25 is provided to which 24 is connected. The common electrode portion 25 is wider in the nozzle arrangement direction than the individual electrode 23, and thus the common electrode portion 25 is formed to have a larger area than the individual electrode 23. Further, the connection between the common electrode portion 25 and each common electrode 24 is made through internal electrodes 22 a and 22 b that are not divided by half-cut dicing of the piezoelectric element member 12.

  In the FPC 15, a plurality of individual wiring electrodes 31A and a common wiring electrode 31B are formed on a base material 30. Then, the individual wiring electrodes 31A of the FPC 15 are joined and electrically connected to the individual electrodes 23 of each driving piezoelectric element column 12A of the piezoelectric element member 12 by solder 32 which is an electrical connection member. The common wiring electrode 31B of the FPC 15 is also joined and electrically connected to the common electrode portion 25 provided on the non-driving piezoelectric element column 12Ba on the one end side of 12 by the solder 32.

  Here, the common wiring electrode 31 </ b> B of the FPC 15 has a plurality of connection portions 31 </ b> Ba formed in a connection portion 15 </ b> A where one wiring branches into a plurality of portions and is connected to the common electrode portion 25 of the piezoelectric element member 12. The plurality of connection portions 31Ba have a width in the nozzle arrangement direction narrower than the width of the individual wiring electrode 31A (the width of the individual electrode 23), and in this example, the width is ½. The plurality of connection portions 31Ba have the same pitch as the individual wiring electrode 31A (the same pitch as the individual electrode 23).

  As a result, the electrode area per unit area in the portion connected to the common electrode portion 25 of the common wiring electrode 31 </ b> B of the FPC 15 is about ½ the area smaller than the portion connected to the individual electrode 23. Further, if the amount of solder 32 that is an electrical connection member used in the portion connected to the common electrode portion 25 of the common wiring electrode 31B of the FPC 15 is the same, the portion of the solder 32 connected to the individual electrode 23 The amount is about ½ that is less than the amount. Here, the unit area refers to a certain area including the electrode portion and the non-electrode portion of the FPC, and in the configuration in which the electrode portions are arranged at regular intervals with the non-electrode portion interposed therebetween as shown in FIG. It is set as the area of a region including the same number of electrode portions.

  The length of the connection portion 31Ba of the common wiring electrode 31B of the FPC is a length obtained by combining the length L1 of the portion 15A connected to the common electrode portion 25 and the length L2 equal to or longer than this length L1, that is, the connection The portion 31Ba is configured to have a length that is at least twice as long as the length connected to the common electrode portion 25.

  As a method of connecting the individual electrodes 23 and the common electrode portion 25 of these piezoelectric element members 12 and the electrodes 31A and 31B of the FPC 15, laser light is applied to the FPC 15 in a state where the FPC 15 is pressurized with a laser transmitting rigid member such as glass. A laser bonding method is used in which the electrodes 31 and the solder 32 are irradiated to melt and harden the solder 32. In addition, the electrodes are aligned, the piezoelectric element member 12 and the FPC 15 are overlapped, and the heater chip temperature is increased in a pulsed manner while pressing the base material on the back surface of the joining portion 15A of the FPC 15 with the heater chip (block). Although a heater joining method for joining by melting and curing can be used, the configuration according to the present invention is particularly effective in the case of the laser joining method.

  The solder 32 may be a material having a lower melting point than the electrode 31 of the FPC 15 made of a metal member and the base material 30 of the FPC 15 and made of a conductive material. Pb) is preferably not contained. For example, a solder mainly composed of tin (Sn) and bismuth (Bi) can be used as the solder 32. Since lead is not contained, it is effective from the viewpoint of environmental protection, and the solder 32 mainly composed of tin (Sn) and bismuth (Bi) has a very low melting point among non-lead members. Therefore, the electrodes 31A and 31B of the FPC 15 and the individual electrodes 23 and the common electrode portion 25 of the piezoelectric element member 12 can be easily welded without damaging the FPC 15 and the piezoelectric element member 12.

  Here, solder is used as the electrical connection member, but an anisotropic conductive film, a conductive adhesive, or the like can also be used. Further, it can be formed in advance on the individual electrode 23 on the piezoelectric element member 12 side, the common electrode portion 25, or the connection portion 31Ba of the FPC individual wiring electrode 31A and the common wiring electrode 31B by a printing method, a plating method, or the like. . Here, although FPC is used as the wiring member, it may be any film provided with a plurality of electrodes that are thin and parallel to each other. For example, TAB (Tape Automated Bonding) can also be used. .

  Next, in order to compare the configuration of the above embodiment with the configuration of the comparative example shown in FIGS. 8 and 9 in which the common wiring electrode 31B of the FPC 15 has the same width as the individual wiring electrode, a piezoelectric element is used by using a laser bonding method. The individual electrodes 23 and the common electrode portion 25 of the member 12 and the electrodes 31A and 31B of the FPC 15 were connected.

  As a result, in the configuration of the above-described embodiment, the common electrode portion 25 of the piezoelectric element member 12 and the FPC 15 are subjected to laser irradiation conditions that allow the individual electrode 23 of the piezoelectric element member 12 and the solder 32 of the individual wiring electrode 31A of the FPC 15 to be melted and joined. The connection portion 31Ba of the common wiring electrode 31B can be bonded, and the bonding failure between the electrodes of the piezoelectric element member 12 and the FPC 15 and the damage of the FPC base material do not occur, and a good bonding is obtained.

  On the other hand, in the conventional configuration, when the joining was performed under the same laser irradiation conditions, the individual electrode 23 and the individual wiring electrode 31A could be joined without any problem, but the solder 32 was melted well in the common electrode portion 25 and the common wiring electrode 31B. It was not possible to join without. Further, if the bonding with the individual electrode 23 is performed under an irradiation condition in which the solder 32 of the common electrode portion 25 can be melted, the expansion / contraction of the base material 30 of the FPC 15 is increased, resulting in poor bonding, or part of the base material 30. Damage also occurred.

  Thus, the common electrode portion is formed to have a larger area than the individual electrode, and the common wiring electrode of the wiring member has a plurality of narrower widths in the nozzle arrangement direction than the width of the individual electrode at the connection portion connected to the common electrode portion. Even when laser bonding is performed, the common wiring electrode area per unit area of the wiring member is smaller than the area of the individual wiring electrode per unit area of the wiring member. It is possible to concentrate the heating due to the above, and to enable the bonding even at the same speed scanning, and to bond the wiring member to the large head without sacrificing the tact time and the merit of the laser bonding.

  In the above embodiment, the amount of solder 32 as an electrical connection member is about ½ that the common electrode portion 25 is smaller than the individual electrode 23. However, bonding failure and overheating due to expansion / contraction of the wiring member such as the FPC 15 If there is no problem such as damage to the wiring member due to the above, or a significant reduction in production efficiency, it is not necessary to reduce to 1/2.

  In addition, the amount per unit area of the electrical connection member that connects the common wiring electrode and the common electrode portion of the wiring member is determined per unit area of the electrical connection member that connects the individual wiring electrode and the individual electrode of the wiring member. By adopting a configuration smaller than the amount, the common electrode portion and the individual electrode can be connected under the same conditions, and the connection failure of the electrode between the piezoelectric element and the wiring member and the damage to the piezoelectric element and the wiring member can be reduced.

  In addition, by making the common electrode part at the end of the piezoelectric element member wider than the individual electrode, even if the nozzle pitch is reduced and the piezoelectric element column provided with the individual electrode becomes thinner, the common end of the piezoelectric element member is shared. The width of the piezoelectric element column provided with the electrode portion can be widened, the strength of the piezoelectric element can be maintained, and damage at the time of connecting the piezoelectric element and the wiring member or other assembly can be reduced.

  In addition, the electrode area per unit area in the part connected to the common electrode part of the common wiring electrode of the wiring member can be easily shared by making the electrode area per unit area in the part connected to the individual electrode of the wiring member smaller. It is possible to reduce the amount of the electrical connection member of the electrode portion, and it is possible to reduce poor connection of the electrodes between the piezoelectric element and the wiring member and damage to the piezoelectric element and the wiring member.

  In addition, the pitch of the connection portions of the common wiring electrode of the wiring member is the same as the pitch of the individual electrodes, and the width of the connection portion of the common wiring electrode of the wiring member is made smaller than the width of the individual electrode, so that the heater chip, laser, etc. The amount of heat of the heating tool can be uniformly applied to the common electrode portion and the individual electrode portion, and the excess amount of heat can be reduced. That is, since the connection failure between the electrodes of the piezoelectric element and the wiring member and the damage of the piezoelectric element and the wiring member can be reduced with a simple configuration, the equipment cost and the heating time can be shortened.

  In addition, the plurality of connecting portions of the common wiring electrode of the wiring member have a length that is at least twice as long as the length connected to the common electrode portion, so that the amount of heat flowing through the wiring of the wiring member is reduced. In addition, it is possible to reduce electrode connection failure between the piezoelectric element and the wiring member and damage to the piezoelectric element and the wiring member.

  That is, in a configuration in which a plurality of connection portions of the common wiring electrode are immediately connected to each other when they are disconnected from the connection portion, the heat capacity of the connection portion increases, so that heat at the time of connection of the wiring member is increased by the wiring. It flows to the connecting part through the terminal and lowers the temperature of the connecting part. On the other hand, the influence of the heat capacity of the joint portion can be reduced by configuring the connection portion to be sufficiently longer than the length for connecting the connection portions as described above.

  Next, another specific embodiment will be described with reference to FIGS. 10 is an explanatory plan view of a main part in a joined state along a direction orthogonal to the nozzle arrangement direction, and FIG. 11 is an explanatory front view of the main part of the piezoelectric element member and the FPC. Here, all the piezoelectric element columns of the piezoelectric element member 12 are illustrated in a normal pitch configuration used as the driving piezoelectric element column 12A.

  The common wiring electrode 31B of the FPC 15 is divided into a plurality of wirings to form a plurality of connection portions 31Ba in the connection portion 15A, and the arrangement pitch of the plurality of connection portions 31Ba is equal to the pitch of the individual wiring electrodes 31A. The width of the connection portion 31Ba of the electrode 31B is smaller than the width of the individual wiring electrode 31A and is about 2/3. Further, the thickness of the solder 32 of the connection portion 31Ba of the common wiring electrode 31B is set to about 2/3 of the thickness of the solder 32 of the individual wiring electrode 31A. Thereby, the amount of the solder 32 which is an electrical connection member per unit area of the FPC 15 is set to be about 4/9 in which the connection portion 32Ba of the common wiring electrode 32 is smaller than the individual broken line electrode 31A. The solder 32 is formed on the electrode 31A and the connection portion 31Ba of the FPC 15 by electroplating, and the integrated current amount at the time of plating is changed between the individual wiring electrode 31A and the common wiring electrode 31B. The thickness of the connection portion 31ba of the electrode 31B is controlled.

  Similar to the above-described embodiment, the common electrode of the piezoelectric element member 12 is used under a laser irradiation condition in which the individual electrode 23 of the piezoelectric element member 12 and the solder 32 of the individual wiring electrode 31A of the FPC 15 can be melted and bonded using the laser bonding method. The connection part 31Ba of the common wiring electrode 31B of the part 25 and the FPC 15 can be joined, and the joining of the piezoelectric element member 12 and the FPC 15 does not fail and the FPC base material is not damaged.

  Since the laser bonding method is non-contact heating unlike a heater chip or the like, even if the solder thickness is different and the pressure surface is not flat, it is possible to reliably bond. Specifically, the laser irradiation is performed while spraying and pressing air on the laser irradiation portion, so that even a non-flat surface can be bonded in a uniform pressurized state.

  Thus, by making the thickness of the electrical connection member that connects the common wiring electrode and the common electrode portion thinner than the thickness of the electrical connection member that connects the individual wiring electrode and the individual electrode, the common wiring is more than in the above embodiment. The width of the electrode can be increased, and more current can flow through the common wiring electrode.

  Here, the amount of solder 32, which is an electrical connection member, is about 4/9, which is less than that of the individual electrode in the common electrode portion. However, bonding failure due to expansion / contraction of the wiring member, wiring board damage due to overheating, production It does not need to be 4/9 unless a problem such as a significant decrease in efficiency occurs.

  In addition, since solder is used as the electrical connection member and the electrode of the wiring member is formed by electroplating, the film thickness of the electrical connection member of the common wiring electrode and the individual wiring electrode can be easily controlled. It is possible to cope with the finer nozzle pitch than the printing method.

Next, an example of an image forming apparatus equipped with the liquid ejection head according to the present invention will be described with reference to FIGS.
This image forming apparatus is a serial type image forming apparatus, and a carriage 233 is slidably held in the main scanning direction by main and slave guide rods 231 and 232 which are guide members horizontally mounted on the left and right side plates 221A and 221B. The main scanning motor that does not perform moving scanning in the direction indicated by the arrow (carriage main scanning direction) via the timing belt.

  The carriage 233 has recording heads 234a and 234b (which are composed of liquid ejection heads according to the present invention for ejecting ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (K). When not distinguished, it is referred to as “recording head 234”). A nozzle row composed of a plurality of nozzles is arranged in the sub-scanning direction orthogonal to the main scanning direction, and is mounted with the ink droplet ejection direction facing downward.

  Each of the recording heads 234 has two nozzle rows. One nozzle row of the recording head 234a has black (K) droplets, the other nozzle row has cyan (C) droplets, and the recording head 234b has one nozzle row. One nozzle row ejects magenta (M) droplets, and the other nozzle row ejects yellow (Y) droplets. In this example, four-color droplets are ejected in a two-head configuration. However, a recording head for each color can be provided, and a nozzle row in which a plurality of nozzles ejecting four-color droplets are arranged. It is also possible to have a single recording head configuration.

  The carriage 233 is equipped with sub tanks 235a and 235b (referred to as “sub tank 235” when not distinguished) for supplying ink of each color corresponding to the nozzle rows of the recording head 234. The sub tank 235 is supplied with ink of each color from the ink cartridge 210 of each color via a supply tube 236 for each color by a supply unit (not shown).

  On the other hand, as a paper feed unit for feeding the paper 242 loaded on the paper stacking unit (pressure plate) 241 of the paper feed tray 202, a half-moon roller (feed) that feeds the paper 242 from the paper stacking unit 241 one by one. A separation pad 244 made of a material having a large coefficient of friction is provided opposite to the sheet roller 243 and the sheet feeding roller 243, and the separation pad 244 is urged toward the sheet feeding roller 243 side.

  In order to feed the sheet 242 fed from the sheet feeding unit to the lower side of the recording head 234, a guide member 245 for guiding the sheet 242, a counter roller 246, a conveyance guide member 247, and a tip pressure roller. And a conveying belt 251 which is a conveying means for electrostatically attracting the fed paper 242 and conveying it at a position facing the recording head 234.

  The conveyor belt 251 is an endless belt, and is configured to wrap around the conveyor roller 252 and the tension roller 253 so as to circulate in the belt conveyance direction (sub-scanning direction). In addition, a charging roller 256 that is a charging unit for charging the surface of the transport belt 251 is provided. The charging roller 256 is disposed so as to come into contact with the surface layer of the conveyor belt 251 and to rotate following the rotation of the conveyor belt 251. The transport belt 251 rotates in the belt transport direction when the transport roller 252 is rotationally driven through timing by a sub-scanning motor (not shown).

  Further, as a paper discharge unit for discharging the paper 242 recorded by the recording head 234, a separation claw 261 for separating the paper 242 from the transport belt 251, a paper discharge roller 262, and a paper discharge roller 263 are provided. A paper discharge tray 203 is provided below the paper discharge roller 262.

  A double-sided unit 271 is detachably attached to the back surface of the apparatus main body. The duplex unit 271 takes in the paper 242 returned by the reverse rotation of the transport belt 251, reverses it, and feeds it again between the counter roller 246 and the transport belt 251. The upper surface of the duplex unit 271 is a manual feed tray 272.

  Further, a maintenance / recovery mechanism 281 that is a head maintenance / recovery device according to the present invention includes a recovery means for maintaining and recovering the nozzle state of the recording head 234 in the non-printing area on one side of the carriage 233 in the scanning direction. Is arranged. The maintenance / recovery mechanism 281 includes cap members (hereinafter referred to as “caps”) 282a and 282b (hereinafter referred to as “caps 282” when not distinguished) for capping each nozzle surface of the recording head 234, and nozzle surfaces. A wiper blade 283 that is a blade member for wiping the ink, and an empty discharge receiver 284 that receives liquid droplets for discharging the liquid droplets that do not contribute to recording in order to discharge the thickened recording liquid. ing.

  In addition, in the non-printing area on the other side in the scanning direction of the carriage 233, the liquid that receives liquid droplets when performing idle ejection that ejects liquid droplets that do not contribute to recording in order to discharge the recording liquid thickened during recording or the like. An ink recovery unit (empty discharge receiver) 288 that is a recovery container is disposed, and the ink recovery unit 288 includes an opening 289 along the nozzle row direction of the recording head 234 and the like.

  In this image forming apparatus configured as described above, the sheets 242 are separated and fed one by one from the sheet feeding tray 202, and the sheet 242 fed substantially vertically upward is guided by the guide 245, and is conveyed to the conveyor belt 251 and the counter. It is sandwiched between the rollers 246 and conveyed, and further, the leading end is guided by the conveying guide 237 and pressed against the conveying belt 251 by the leading end pressing roller 249, and the conveying direction is changed by approximately 90 °.

  At this time, a positive output and a negative output are alternately applied to the charging roller 256, that is, an alternating voltage is applied, and a charging voltage pattern in which the conveying belt 251 alternates, that is, in the sub-scanning direction that is the circumferential direction. , Plus and minus are alternately charged in a band shape with a predetermined width. When the sheet 242 is fed onto the conveyance belt 251 charged alternately with plus and minus, the sheet 242 is attracted to the conveyance belt 251, and the sheet 242 is conveyed in the sub scanning direction by the circumferential movement of the conveyance belt 251.

  Therefore, by driving the recording head 234 according to the image signal while moving the carriage 233, ink droplets are ejected onto the stopped paper 242 to record one line, and after the paper 242 is conveyed by a predetermined amount, Record the next line. Upon receiving a recording end signal or a signal that the trailing edge of the paper 242 has reached the recording area, the recording operation is finished and the paper 242 is discharged onto the paper discharge tray 203.

  As described above, since the image forming apparatus includes the liquid ejection head according to the present invention, there is no bonding failure, the reliability of the recording head is improved, and stable recording can be performed.

  In the above embodiment, the present invention has been described with reference to an example in which the present invention is applied to an image forming apparatus having a printer configuration. However, the present invention is not limited to this. For example, the present invention may be applied to an image forming apparatus such as a printer / fax / copier multifunction machine. it can. Further, the present invention can be applied to an image forming apparatus using a liquid other than the narrowly defined ink, a fixing processing liquid, or the like.

DESCRIPTION OF SYMBOLS 1 Flow path plate 2 Nozzle plate 3 Vibration plate 4 Nozzle 6 Individual liquid chamber 10 Common liquid chamber 12 Piezoelectric element member 12A, 12B Piezoelectric element column 12Ba Piezoelectric element column 13 Base member 15 FPC (wiring member)
23 Individual electrode 25 Common electrode part 31A Individual wiring electrode (connection electrode)
31B Common wiring electrode (connection electrode)
31Ba connection part 32 ... solder member 234 ... carriage 235 ... recording head

Claims (6)

A plurality of piezoelectric elements corresponding to a plurality of pressurized liquid chambers through which nozzles for discharging droplets communicate;
A wiring member for supplying a drive signal to the plurality of piezoelectric elements,
The individual electrodes of the plurality of piezoelectric elements are connected to individual wiring electrodes provided on the wiring member by an electrical connection member. The common electrode portion common to the plurality of piezoelectric elements is provided to the wiring member by an electrical connection member. Connected common wiring electrodes,
The common electrode portion is formed to have a larger area than the individual electrodes,
The common wiring electrode of the wiring member has a plurality of connection portions whose width in the nozzle arrangement direction is narrower than the width of the individual wiring electrode in the connection portion connected to the common electrode portion,
The liquid ejection head, wherein an area of the common wiring electrode per unit area of the wiring member is smaller than an area of the individual wiring electrode per unit area of the wiring member.   The amount per unit area of the electrical connection member that connects the common wiring electrode of the wiring member and the common electrode portion is the unit area of the electrical connection member that connects the individual wiring electrode of the wiring member and the individual electrode. The liquid discharge head according to claim 1, wherein the liquid discharge head is smaller than a hit amount.   The common wiring electrode of the wiring member is branched into the plurality of connection portions at a portion connected to the common electrode portion, and each branched connection portion is arranged at the same pitch as the individual wiring electrodes. The liquid discharge head according to claim 1 or 2.   4. The plurality of connection portions of the common wiring electrode of the wiring member have a length that is at least twice as long as the length of the common wiring electrode connected to the common electrode portion. The liquid discharge head described.   The thickness of the electrical connection member that connects the common wiring electrode of the wiring member and the common electrode portion is thinner than the thickness of the electrical connection member that connects the individual wiring electrode of the wiring member and the individual electrode. The liquid discharge head according to claim 1, wherein the liquid discharge head is a liquid discharge head.   An image forming apparatus comprising the liquid discharge head according to claim 1.

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