JP2008149588A - Piezoelectric actuator, liquid discharge head and image formation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that the joint of a piezoelectric element pillar with an oscillating board member in the state that the end area of an piezoelectric actuator can be used actually and a sufficient joint strength can be obtained is difficult. <P>SOLUTION: The piezoelectric actuator 10 includes a piezoelectric element unit 11 in which a piezoelectric element member 12a wherein two or more piezoelectric element pillars 12A are formed in a predetermined pitch through a groove and arranged in the shape of lines is jointed to a base member 13 and the oscillating board member 2 jointed to two or more piezoelectric element pillars 12A, 12B with an adhesive. One piezoelectric element pillar 12a and the oscillating board member 2 are adhered with the 1st and 2nd adhesives 21, 22. The adhering speed of the 1st adhesive 21 is made higher than the one of the 2nd adhesive 22, and the adhesion strength of the 2nd adhesive 22 is made stronger than the one of the 1st adhesive 21. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  In general, as a printer / fax / copier or an image forming apparatus combining these functions, for example, a liquid ejection apparatus including a recording head composed of a liquid ejection head that ejects liquid droplets of a recording liquid (liquid) is used. While conveying a medium (hereinafter also referred to as “paper”, the material is not limited, and a recording medium, a recording medium, a transfer material, and recording paper are also used synonymously) In some cases, image formation (recording, printing, printing, and printing are also used synonymously) is made by adhering ink to a sheet.

  The image forming apparatus means an apparatus for forming an image by discharging a liquid onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, etc. The term “not only” 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. Further, the liquid ejection apparatus means an apparatus that ejects liquid from a liquid ejection head, and is not limited to an apparatus that performs image formation.

  As the 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 the liquid chamber. Then, a so-called piezoelectric actuator is used that deforms the elastically deformable diaphragm that forms the wall surface of the liquid chamber by the displacement of the laminated piezoelectric element in the direction d33 or d31, and changes the volume / pressure in the liquid chamber to discharge droplets. Known piezoelectric heads are known.

In a liquid discharge head using such a piezoelectric actuator, as described in Patent Documents 1 and 2, the piezoelectric element and the vibration plate are joined with an adhesive.
Japanese Patent Laid-Open No. 2002-240279 JP 2006-035807 A

In this case, as described in Patent Documents 3 and 4, the end of the surface to be joined to the diaphragm of the piezoelectric element is cut, or a clearance groove is formed to release excess adhesive during bonding. It is known that
JP 2001-047632 A Japanese Patent No. 2933608

Further, as described in Patent Document 5, the vibration plate has a recess facing a region where the bonding adhesive for the piezoelectric element is not applied, and the vibration plate and the piezoelectric element are formed in the recess by a fast-curing adhesive. It is known to fix.
Japanese Patent Laid-Open No. 2002-240279

  As described above, in the piezoelectric actuator and the liquid discharge head including the piezoelectric actuator, the vibration plate and the piezoelectric element column are bonded with an adhesive. However, as the adhesive, the thermosetting property is highly reliable and has high moisture resistance. An epoxy adhesive or the like is generally used. However, since the thermosetting adhesive has a low curing rate at low temperatures, it becomes an obstacle to shortening the construction period of the assembly process.

  Therefore, when a piezoelectric element unit in which a plurality of piezoelectric elements are formed in a columnar shape is joined to a diaphragm, a UV (ultraviolet curable) adhesive is used on a portion that is not used as a piezoelectric actuator at the end of the piezoelectric element column in the arrangement direction. It is conceivable to use a thermosetting adhesive for the piezoelectric element columns used as other driving units. As a result, the UV adhesive can be instantaneously cured to prevent positional displacement, and then heat can be applied to complete the bonding.

  However, if there is only a small area even if there is a part that is not used as the drive part at the end of the piezoelectric actuator, UV adhesive is used for the end area of the piezoelectric actuator, and thermosetting adhesive is used for the center part. Since the characteristics of the actuator change between different areas of the adhesive, there is a problem that it cannot be used in practice. Further, when only the UV adhesive is used, there arises a problem that the required strength cannot be obtained because the bonding strength is weak.

  Also, in order to support high-speed recording of the image forming apparatus, for example, when a long head such as a line head is configured by arranging a plurality of piezoelectric element units side by side with respect to a common diaphragm, the drive unit is arranged at an equal pitch. In some cases, the connecting portion (end portion) of the piezoelectric element unit becomes a piezoelectric element that serves as a drive unit, and the end portion of the piezoelectric actuator may not have a portion that is not used as the drive unit. Even in such a case, when a UV adhesive is used for the driving part at the end of the piezoelectric actuator and a thermosetting adhesive is used for the central part, there is a problem that the characteristics change between the driving parts.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a piezoelectric actuator that can be actually used up to the end portion and that can provide stable bonding quality, a liquid discharge head including the piezoelectric actuator, and an image forming apparatus. To do.

  In order to solve the above problems, a piezoelectric actuator according to the present invention includes a piezoelectric element member in which a plurality of piezoelectric element columns are formed at predetermined pitches through grooves and arranged in a line, and a plurality of piezoelectric elements. And a piezoelectric element column and a diaphragm member are bonded to each other with a first adhesive and a second adhesive, and the first adhesive is a second adhesive. The bonding speed is higher than that of the adhesive, and the second adhesive has a higher adhesive strength than the first adhesive.

  Here, the first adhesive is a visible light curable adhesive, a two-component curable adhesive, a thermosetting adhesive, an ultraviolet curable adhesive, or a humidity curable adhesive, and the second adhesive is a thermosetting adhesive. It is preferable that Moreover, it is preferable that a 1st adhesive agent exists in an edge part side rather than a 2nd adhesive agent in the direction orthogonal to the row direction of a some piezoelectric element pillar. Moreover, it is preferable that the piezoelectric element column has a recess formed in the bonding portion of the second adhesive, and in this case, the recess may be a notch opened toward the end. The recess may be formed in a range smaller than the inactive region of the piezoelectric element column, or conversely, the recess may be formed in a range larger than the inactive region of the piezoelectric element column.

  Moreover, it can be set as the structure containing the 1st piezoelectric element adhere | attached with a 1st, 2nd adhesive agent, and the 2nd piezoelectric element adhere | attached with a 2nd adhesive agent. The first piezoelectric element column includes a first piezoelectric element column bonded by a first adhesive and a second adhesive, and a second piezoelectric element column bonded by a second adhesive, and the first piezoelectric element column includes a second piezoelectric element column. A concave portion is formed in the adhesive portion of the adhesive, and the concave portion is not formed in the second piezoelectric element column. In these cases, the first piezoelectric element column may be a piezoelectric element column to which no driving voltage is applied, and the second piezoelectric element column may be a piezoelectric element column to which a driving voltage is applied.

  The liquid discharge head according to the present invention includes the piezoelectric actuator according to the present invention.

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

  According to the piezoelectric actuator according to the present invention, a plurality of piezoelectric element columns are formed at a predetermined pitch through grooves, and are bonded to the plurality of piezoelectric element columns with piezoelectric element members arranged in rows. The one piezoelectric element column and the diaphragm member are bonded with a first adhesive and a second adhesive, and the first adhesive has a bonding speed higher than that of the second adhesive. Since the second adhesive has a stronger adhesive strength than the first adhesive, the bonding position can be determined by the first adhesive and the bonding quality can be stabilized by the second adhesive. It is possible to obtain a stable joint quality that can be used up to the end.

  According to the liquid ejection head according to the present invention, since the piezoelectric actuator according to the present invention is provided, it is possible to use up to the end and obtain a stable joining quality, and it is possible to use the drive up to the end of the piezoelectric actuator. Thus, it is possible to connect the piezoelectric element columns at an equal pitch, and it is possible to make a long head by connecting them by one.

  According to the image forming apparatus of the present invention, since the liquid discharge head according to the present invention is provided, the liquid discharge head is used as a drive unit to the end of the piezoelectric actuator, and the piezoelectric element columns are connected at a constant pitch. The long head can be made, and high-speed recording can be achieved at low cost.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. First, an embodiment of a liquid discharge head according to the present invention will be described with reference to FIGS. 1 is an external perspective view of the liquid discharge head, FIG. 2 is a cross-sectional explanatory view along the longitudinal direction of the liquid chamber along the line AA in FIG. FIG. 3 is a cross-sectional explanatory view along the shorter direction of the liquid chamber (the direction in which the liquid chambers are arranged).

  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 liquid chamber (hereinafter referred to as a “pressurized liquid chamber” as a separate flow path) through which a nozzle 4 that discharges liquid droplets (liquid droplets) communicates with the pressure chamber, the pressure chamber, the flow path, etc. 6), a fluid resistance section 7 that also serves as a supply path for supplying ink (recording liquid) that is liquid to the pressurized liquid chamber 6, and a common liquid that supplies recording liquid to the plurality of pressurized liquid chambers 6. A chamber 8 is formed. The recording liquid is supplied to the common liquid chamber 8 from a liquid tank (not shown) via a supply path.

  Here, the flow path substrate 1 is configured by adhering a restrictor plate 1A and a chamber plate 1B. The flow path substrate 1 is formed by etching the SUS substrate with an acidic etchant or machining such as punching (pressing), so that each pressurized liquid chamber 6, fluid resistance portion 7, common liquid chamber 8, etc. Each opening is formed. The fluid resistance portion 7 is formed by opening a portion of the restrictor plate 1A and not opening a portion of the chamber plate 1B.

  The diaphragm member 2 is adhesively bonded to the chamber plate 1B constituting the flow path substrate 1. The diaphragm member 2 is composed of a metal plate, a resin plate, a laminated member of a metal plate and a resin layer, and the part forming the wall surface of the pressurized liquid chamber 6 is a deformable diaphragm region 2A.

  The nozzle plate 3 forms a large number of nozzles 4 having a diameter of 10 to 30 μm corresponding to the pressurized liquid chambers 6 and is bonded to the restrictor plate 1 </ b> A of the flow path substrate 1 with an adhesive. As this nozzle plate 3, what consists of metals, such as stainless steel and nickel, resin, such as a polyimide resin film, silicon | silicone, and those combinations can be used. Further, a water repellent film is formed on the nozzle surface (surface in the ejection direction: ejection surface) by a known method such as a plating film or a water repellent coating in order to ensure water repellency with ink.

  A plurality of piezoelectric element units 11 are adhesively bonded and arranged in two rows on the outer side of the diaphragm member 2 (on the side opposite to the pressurized liquid chamber 6). The plurality of piezoelectric element units 11 and the diaphragm member 2 constitute a piezoelectric actuator 10 according to the present invention.

  One piezoelectric element unit 11 includes a piezoelectric element member 12 formed without dividing a plurality of piezoelectric element columns 12a by half-cut groove processing (slit processing), and a base member 13 to which the piezoelectric element members 12 are joined. And. Each piezoelectric element column 12a of the piezoelectric element member 22 has a second piezoelectric element column (driving piezoelectric element column) 12A that is driven every other one and a first piezoelectric element column (non-driving piezoelectric element column) 12B that is not driven. Use as A power feeding member 14 such as an FPC cable for applying a driving waveform is connected to one end face of each piezoelectric element member 12.

  The piezoelectric element member 12 includes a lead zirconate titanate (PZT) piezoelectric layer having a thickness of 10 to 50 μm / layer, and an internal electrode layer made of silver / palladium (AgPd) having a thickness of several μm / layer. The internal electrodes are alternately electrically connected to individual electrodes and common electrodes (not shown) that are end face electrodes (external electrodes) on the end faces. This piezoelectric constant is d33 (d33 indicates expansion / contraction perpendicular to the internal electrode surface (thickness direction)). The diaphragm region 2A is displaced by the expansion / contraction of the piezoelectric element column 12A, and the pressurized liquid chamber 6 is contracted and expanded. It is supposed to let you. When the drive signal is applied to the piezoelectric element column 12A and charging is performed, the piezoelectric element column 12A expands, and when the electric charge charged to the piezoelectric element column 12A is discharged, the piezoelectric element column 12A contracts in the opposite direction.

  It should be noted that the ink in the pressurized liquid chamber 6 may be pressurized using the displacement in the d33 direction as the piezoelectric direction of the piezoelectric element column 12A, or may be pressurized using the displacement in the d31 direction as the piezoelectric direction of the piezoelectric element column 12A. A configuration may be adopted in which the ink in the liquid chamber 6 is pressurized. In the present embodiment, a configuration using displacement in the d33 direction is adopted.

  Further, a frame member 17 is joined around the diaphragm member 2 with an adhesive. In the frame member 17, a buffer chamber 18 adjacent to the common liquid chamber 8 is formed via a diaphragm portion 2 </ b> C as a deformable portion configured by the diaphragm member 2. The diaphragm portion 2 </ b> C forms wall surfaces of the common liquid chamber 8 and the buffer chamber 18. The buffer chamber 18 communicates with the atmosphere via the communication path 20.

  In this liquid discharge head, the piezoelectric elements 12 are formed at intervals of 300 dpi and are arranged in two rows so as to face each other. Further, the pressurized liquid chamber 6 and the nozzle 4 are arranged in two rows in a staggered manner at intervals of 150 dpi, and a resolution of 300 dpi can be obtained in one scan.

  In addition, as described above, since this liquid discharge head is made of SUS and has the same thermal expansion coefficient, various problems due to thermal expansion during the assembly or use of the head are avoided. Can do.

  In the liquid discharge head configured as described above, for example, the voltage applied to the second piezoelectric element column 12A is lowered from the reference potential, so that the second piezoelectric element column 12A contracts, and the diaphragm region 2A of the diaphragm member 2 is reduced. And the volume of the pressurized liquid chamber 6 expands, so that the recording liquid flows into the pressurized liquid chamber 6, and then the voltage applied to the second piezoelectric element column 12A is increased to increase the second piezoelectric element. The recording liquid in the pressurizing liquid chamber 6 is pressurized by extending the element columns 12A in the stacking direction and deforming the diaphragm region 2A in the nozzle 4 direction to contract the volume / volume of the pressurizing liquid chamber 6. The recording liquid droplets are ejected (ejected) from the nozzle 4.

  Then, by returning the voltage applied to the second piezoelectric element column 12A to the reference potential, the diaphragm region 2A is restored to the initial position, and the pressurized liquid chamber 6 expands to generate a negative pressure. The recording liquid is filled into the pressurized liquid chamber 6 from the common liquid chamber 8. Therefore, after the vibration of the meniscus surface of the nozzle 4 is attenuated and stabilized, the operation proceeds to the next droplet discharge.

  Note that the driving method of the head is not limited to the above example (drawing-pushing), and striking or pushing can be performed depending on the direction of the drive waveform.

Therefore, the bonding of the piezoelectric element member 12 and the diaphragm member 2 in this liquid discharge head will be specifically described with reference to FIG. FIG. 4 is an enlarged explanatory view of the piezoelectric element unit.
As described above, the piezoelectric actuator 10 includes a piezoelectric element unit in which a plurality of piezoelectric element columns 12a are formed at predetermined pitches through grooves, and the piezoelectric element members 12a arranged in a line are joined to the base member 13. 11 and a diaphragm member 2 that is adhesively bonded to the plurality of piezoelectric element columns 12A and 12B. One piezoelectric element column 12a and the diaphragm member 2 include a first adhesive 21 and a second adhesive. The first adhesive 21 has a higher bonding speed than the second adhesive 22, and the second adhesive 22 has a higher bonding strength than the first adhesive 21.

  Here, as the first adhesive 21, it is preferable to use a visible light curable adhesive, a two-component curable adhesive, a thermosetting adhesive, an ultraviolet curable adhesive, and a humidity curable adhesive, and the second adhesive 22. It is preferable to use a thermosetting adhesive.

  In addition, the piezoelectric element column 12a is in a direction orthogonal to the direction in which the plurality of piezoelectric element columns are arranged, and the end portion on the side that does not face the piezoelectric element columns in the other rows (the end portion on the side where the feeding member 14 is connected). In addition, a notch 23 which is a recess opened toward the end is formed, and the first adhesive 21 is applied to the notch 23. Here, the notch 23 is formed in a range larger than the inactive region 24 of the piezoelectric element column 12a. The inactive region 24 is a region where alternating internal electrodes do not face each other, and the active region 25 is a region where alternating internal electrodes face each other.

  Since it comprised in this way, the 1st adhesive agent 21 and the 2nd adhesive agent 22 are apply | coated to each piezoelectric element pillar 12a of the piezoelectric element unit 11, and in the state which aligned with the diaphragm member 2, the adhesion speed is high. 1 adhesive 21 is cured, primary bonding is completed in a state where the piezoelectric element unit 11 and the diaphragm member 2 are positioned, and then the second adhesive 22 having high bonding strength is cured, The piezoelectric element unit 11 and the diaphragm member 2 are firmly joined.

  Thereby, it is possible to actually use up to the piezoelectric element column 12a at the end of the piezoelectric element column of the piezoelectric element member 12 in the arrangement direction, and a sufficient bonding strength is obtained, and the bonding quality is stabilized.

Here, a specific example will be described with reference to FIG. FIG. 5 is an explanatory diagram for explaining the bonding process of the piezoelectric element unit to the diaphragm member.
First, the nozzle plate 3, the restrictor plate 1A, the chamber plate 1B, and the vibration plate member 2 (polyimide: using a thickness of 4 μm) were laminated and prepared so that the length of the nozzle row from end to end was 12 inches. .

  On the other hand, the piezoelectric element unit 11 is prepared by bonding the piezoelectric element member 12 to the SUS base member 13 with an adhesive, dicing at 300 dpi, and then applying electrical wiring. The piezoelectric element unit 11 has a length of 1 inch, and twelve are arranged to constitute a liquid discharge head corresponding to a nozzle row of 12 inches.

  Here, when twelve piezoelectric units 11 are joined to the diaphragm member 2, when the second and subsequent piezoelectric element units 11 are aligned and joined to the diaphragm member 2, the piezoelectric element unit 11 joined first is sufficiently If they are not joined, when they interfere with the previous piezoelectric unit 11 during the second alignment joining, a positional deviation is easily caused, resulting in a failure.

  Accordingly, a notch 23 is formed on the surface of the piezoelectric element column 11 that contacts the diaphragm member 2 of the piezoelectric element column 12a. Adhesive 21) was applied by dispensing. In addition, the notch part 23 as a recessed part was formed by giving a groove process by dicing in the arrangement direction of the piezoelectric element pillars 12a. In addition, a thermosetting adhesive (second adhesive 22) was applied to the joint surface of the piezoelectric element column 12a other than the region other than the notch 23 with the diaphragm member 2.

  Then, the piezoelectric element unit 11 and the diaphragm member 2 are aligned by alignment, and the ultraviolet curable adhesive is applied to the notch portion 23 as a recess while the diaphragm member 2 and the piezoelectric element unit 11 are in contact with each other. The adhesive (first adhesive 21) is irradiated with ultraviolet light, and primary bonding is completed in a state where the agent is firmly positioned. Subsequently, the thermosetting adhesive (second adhesive 22) is cured by applying heat in an environment such as an oven. Here, an ultraviolet curable adhesive is used as an example of a fast curable adhesive having a high adhesion speed, but as described above, if it is fast cured, heat curing, anaerobic, humidity curing, two liquid reaction type, etc. It is also possible to use an adhesive.

  As described above, a fast-curing ultraviolet curable adhesive and a thermosetting adhesive with high bonding strength are used as an adhesive for bonding one piezoelectric element column and a diaphragm member. A part and the diaphragm member can be instantaneously completed to cure, and no positional deviation occurs during alignment bonding of the piezoelectric element unit. In this case, the joint interface can be firmly connected by using the thermosetting adhesive together, and a stable joint interface can be obtained. Furthermore, since the concave portion formed in the piezoelectric element column is arranged on the open end side, the ultraviolet light can reach sufficiently and stable curing can be completed in a short time. Furthermore, since the UV curable adhesive is applied only to the recesses, it does not mix with the thermosetting adhesive (second adhesive) and is less likely to cause poor bonding due to an unexpected chemical reaction. . Thereby, the stable joining quality is securable.

  Moreover, it is possible to prevent the displacement efficiency of the piezoelectric element column from being lowered by making the recess (notch) to which the first adhesive is applied smaller (narrower) than the inactive region of the piezoelectric element column. On the other hand, the concave portion (notch portion) for applying the first adhesive is made larger (wider) than the inactive region of the piezoelectric element column, so that the first adhesive can be sufficiently applied and bonded. The strength can be increased, and defects such as joining displacement can be reduced.

  The piezoelectric element unit and the diaphragm member may be joined, for example, when a semi-solid adhesive is applied to the end of the piezoelectric element member 12 (a recess or a notch is provided before slitting the piezoelectric element member 12). Is applied in a line shape, and then the piezoelectric element member 12 is slitted by dicing and divided into piezoelectric element columns, so that the ends of the piezoelectric element columns (including recesses or notches) are included. It is also possible to obtain a piezoelectric element member coated with the first adhesive and to bond it to the diaphragm member. Alternatively, after applying the first adhesive in a line shape at a position corresponding to the end of the piezoelectric element column (including the recess or notch) on the diaphragm member side, the piezoelectric element of the diaphragm member and the piezoelectric element unit Bonding with a pillar can also be performed.

  Further, as shown in FIG. 5, when a plurality of piezoelectric element units are arranged side by side and joined to the diaphragm to form a long head by one connection, if the drive units are arranged at an equal pitch, adjacent piezoelectric elements One of the piezoelectric element columns adjacent to the unit is a drive unit. Therefore, as before, the piezoelectric element column at the end of the piezoelectric element unit cannot be bonded to the diaphragm using the ultraviolet curable adhesive, and the other piezoelectric element columns cannot be bonded to the diaphragm using the thermosetting adhesive. On the other hand, according to the present invention, the piezoelectric element column at the end of the piezoelectric element unit can be joined to the diaphragm with the thermosetting resin (second adhesive).

  In other words, the piezoelectric element column at the end of the piezoelectric element unit can be used as a driving unit, and a plurality of piezoelectric element units are connected to one diaphragm while keeping the driving piezoelectric element columns at an equal pitch. Therefore, a long head such as a single connecting line head can be realized. As a result, a line-type image forming apparatus as will be described later provided with a liquid discharge head including the piezoelectric actuator according to the present invention can be configured, and high-speed recording becomes possible.

  Next, another embodiment of the liquid discharge head according to the present invention will be described with reference to FIGS. 6 is a schematic perspective view illustrating a state where an adhesive is applied to the piezoelectric element column of the piezoelectric element unit constituting the piezoelectric actuator of the head, FIG. 7 is a bottom explanatory view of the diaphragm member, and FIG. FIG. 9 is a cross-sectional explanatory view of the piezoelectric actuator corresponding to a cross section taken along line BB in FIG. 7, and FIG. 9 is a cross-sectional explanatory view of a main part of the head corresponding to a cross section taken along line CC in FIG.

  Here, as in the above embodiment, the second piezoelectric element column (driving piezoelectric element column) 12A and the first piezoelectric element column (non-driving piezoelectric element column) 12B of the piezoelectric element member 12 are cut as recesses. The notch portion 23 is formed at the end of the piezoelectric element column in the direction in which the piezoelectric element columns are arranged and not opposed to the piezoelectric element columns in the other rows. The notch 23 is smaller than the inactive region 24.

  Then, a first adhesive 21 (for example, an ultraviolet curable adhesive) is applied to the notch 23 of the first piezoelectric element column (non-driving piezoelectric element column) 12B with a dispenser or the like, and the first piezoelectric element is also applied. A second adhesive 22 (for example, a thermosetting adhesive) is applied to the entire upper surface of the pillar (non-driving piezoelectric element pillar) 12B. On the other hand, the first adhesive 21 is not applied to the notch 23 of the second piezoelectric element column (driving piezoelectric element column) 12A, and the upper surface of the second piezoelectric element column (driving piezoelectric element column) 12A. A second adhesive 22 (for example, a thermosetting epoxy adhesive) is applied to the entire area.

  On the other hand, in the diaphragm region 2A of the diaphragm member 2, an island-shaped first convex portion 31A joined to the second piezoelectric element column (drive piezoelectric element column) 12A of the piezoelectric element member 12 is formed. In addition, between the diaphragm regions 2A and 2A of the diaphragm member 2, there is another member joined to the first piezoelectric element column (non-driving piezoelectric element column) 12B corresponding to the liquid chamber interval wall 6A of the flow path member 1. A second convex portion 31B having the same thickness as the portion is formed.

  The electrode 15 of the power supply member 14 is provided corresponding to the second piezoelectric element column (driving piezoelectric element column) 12A.

  Thus, when the piezoelectric element unit 10 is joined to the diaphragm member 2, the first piezoelectric element column (non-driving piezoelectric element column) 12B is positioned corresponding to the liquid chamber interval wall 6A of the flow path member 1, In the same manner as in the embodiment, after the primary bonding is completed by irradiating the first adhesive 21 with ultraviolet rays, the first piezoelectric element column (non-driving piezoelectric element column) 12B and the second piezoelectric element column are applied by applying heat. (Drive piezoelectric element column) The second adhesive 22 of 12A is cured to complete the joining.

  Thus, by applying the first adhesive only to the non-driving piezoelectric element columns arranged under the liquid chamber interval wall and not applying the first adhesive to the driving piezoelectric element columns, the bonding speed can be reduced. Even when the amount of application of the fast (fast-curing) first adhesive is too large, the flow of the adhesive to the diaphragm region is suppressed, so variation in the displacement characteristics of the diaphragm region can be reduced. Can be reduced.

Next, still another embodiment of the liquid discharge head according to the present invention will be described with reference to FIG. FIG. 10 is a schematic perspective explanatory view showing a state in which an adhesive is applied to the piezoelectric element columns of the piezoelectric element unit constituting the piezoelectric actuator of the head.
Here, the first piezoelectric element column (non-driving piezoelectric element column) 12B of the piezoelectric element member 12 has notches 23 as recesses in the direction in which the piezoelectric element columns are arranged, and the piezoelectric element columns in other rows. It is formed in the edge part of the side which does not oppose. The first piezoelectric element column (non-driving piezoelectric element column) 12B applies a first adhesive 21 (for example, an ultraviolet curable adhesive) to the notch 23 with a dispenser or the like, and the upper surface thereof Two adhesives 22 (for example, thermosetting adhesives) are applied to the entire area.

  In contrast, the second piezoelectric element column (driving piezoelectric element column) 12A is not formed with the notch 23, and the second adhesive 22 (for example, a thermosetting epoxy adhesive) is applied to the entire upper surface thereof. It is applied.

  As described above, since the concave portion is formed only in the non-driven second piezoelectric element column, the piezoelectric element column to which the fast-curing first adhesive is applied can be discriminated in appearance, and the first driven column is erroneously detected. It is possible to prevent the fast-curing first adhesive from being applied to the piezoelectric element columns. Further, by not forming a recess in the driven second piezoelectric element column, stable bonding can be performed without reducing the displacement efficiency of the second piezoelectric element column even when the inactive region is very small.

Next, an example of the image forming apparatus according to the present invention including the liquid discharge head according to the present invention will be described with reference to FIG. In addition, FIG. 11 is a schematic block diagram of the whole mechanism part of the apparatus.
The image forming apparatus includes an image forming unit 202 and the like inside the apparatus main body 201, and includes a paper feed tray 204 on the lower side of the apparatus main body 201 on which a large number of recording media (sheets) 203 can be stacked. The paper 203 fed from the paper tray 204 is taken in, a required image is recorded by the image forming unit 202 while the paper 203 is transported by the transport mechanism 205, and then a paper discharge tray 206 mounted on the side of the apparatus main body 201. The sheet 203 is discharged.

  In addition, a duplex unit 207 that can be attached to and detached from the apparatus main body 201 is provided, and when performing duplex printing, the sheet 203 is taken into the duplex unit 207 while being transported in the reverse direction by the transport mechanism 205 after one-side (front) printing is completed. Then, the other side (back side) is sent to the transport mechanism 205 again as the printable side, and the sheet 203 is discharged to the discharge tray 206 after the other side (back side) printing is completed.

  Here, the image forming unit 202, for example, ejects liquid droplets of each color of black (K), cyan (C), magenta (M), and yellow (Y), and is a full line type of four liquids according to the present invention. The recording heads 211k, 211c, 211m, and 211y (which are referred to as “recording heads 211” when the colors are not distinguished) are configured by ejection heads, and each recording head 211 has a nozzle surface on which nozzles for ejecting droplets are formed downward. The head holder 213 is attached. As described above, the recording head 211 includes a piezoelectric actuator in which a plurality of piezoelectric element units are joined to a diaphragm.

  Further, maintenance recovery mechanisms 212k, 212c, 212m, and 212y for maintaining and recovering the head performance corresponding to each recording head 211 are provided (referred to as “maintenance recovery mechanism 212” when colors are not distinguished), and purge processing, During the head performance maintenance operation such as wiping processing, the recording head 211 and the maintenance / recovery mechanism 212 are relatively moved so that the capping member constituting the maintenance / recovery mechanism 212 faces the nozzle surface of the recording head 211.

  Here, the recording head 211 is arranged to eject droplets of each color in the order of yellow, magenta, cyan, and black from the upstream side in the paper conveyance direction, but the arrangement and the number of colors are not limited to this. Further, as the line-type head, one or a plurality of heads provided with a plurality of nozzle rows for discharging droplets of each color at predetermined intervals can be used, and a recording liquid cartridge for supplying a recording liquid to the head and the head. Can be integrated or separated. Furthermore, two heads can be arranged in a straight line at different levels to form a line type head.

  The sheets 203 in the sheet feeding tray 204 are separated one by one by a sheet feeding roller (half-moon roller) 221 and a separation pad (not shown) and fed into the apparatus main body 201, and are registered along the guide surface 223 a of the conveyance guide member 223. 225 and the conveying belt 233, and are sent to the conveying belt 233 of the conveying mechanism 205 via the guide member 226 at a predetermined timing.

  In addition, a guide surface 223 b that guides the sheet 203 sent out from the duplex unit 207 is also formed on the transport guide member 223. Further, a guide member 227 for guiding the sheet 203 returned from the transport mechanism 205 during duplex printing to the duplex unit 207 is also provided.

  The transport mechanism 205 includes an endless transport belt 233 that is stretched between a transport roller 231 that is a driving roller and a driven roller 232, a charging roller 234 that charges the transport belt 233, and an image forming unit 202. A platen member 235 that maintains the flatness of the conveying belt 233 at the opposite portion, a pressing roller 236 that presses the paper 203 fed from the conveying belt 233 against the conveying roller 231, and other recording liquid that is not shown, but adheres to the conveying belt 233. It has a cleaning roller made of a porous material or the like, which is a cleaning means for removing (ink).

  A paper discharge roller 238 and a spur 239 for sending the paper 203 on which an image is recorded to the paper discharge tray 206 are provided on the downstream side of the transport mechanism 205.

  In the image forming apparatus configured as described above, the transport belt 233 rotates in the direction indicated by the arrow, and is positively charged by coming into contact with the charging roller 334 to which a high potential applied voltage is applied. In this case, the charging belt 233 is charged at a predetermined charging pitch by switching the polarity of the charging voltage of the charging roller 234 at a predetermined time interval.

  Here, when the sheet 203 is fed onto the conveying belt 233 charged to this high potential, the inside of the sheet 203 is in a polarized state, and the charge opposite in polarity to the charge on the conveying belt 233 is conveyed to the conveying belt 233 of the sheet 203. The charge on the transport belt 233 and the charge on the transported sheet 203 are electrostatically attracted to each other, and the sheet 203 is electrostatically attracted to the transport belt 233. Is done. In this way, the sheet 203 strongly adsorbed to the conveyor belt 233 is calibrated for warpage and unevenness, and a highly flat surface is formed.

  Then, the paper 203 is moved around the conveyor belt 233 and droplets are ejected from the recording head 211, whereby a required image is formed on the paper 203, and the paper 203 on which the image is recorded is discharged to the paper discharge roller 238. Is discharged to the discharge tray 206.

  As described above, since the image forming apparatus includes the recording head including the liquid discharge head according to the present invention, it is possible to form an image at high speed using a recording head that can be obtained at low cost and high reliability. it can.

  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 recording liquid or a fixing processing liquid that is a liquid other than ink. The piezoelectric actuator according to the present invention can also be used for fluid pumps, optical microdevices, and the like other than liquid ejection heads.

It is an external appearance perspective explanatory view showing an example of a liquid discharge head concerning the present invention provided with a piezoelectric actuator concerning the present invention. FIG. 2 is a cross-sectional explanatory view along a liquid chamber longitudinal direction (a direction orthogonal to the liquid chamber arrangement direction) along the line AA in FIG. 1. FIG. 6 is a cross-sectional explanatory view along the liquid chamber short direction (liquid chamber arrangement direction). It is an enlarged explanatory view of a piezoelectric actuator part. It is explanatory drawing with which it uses for description of the joining process to the diaphragm member of a piezoelectric element unit similarly. FIG. 10 is a schematic perspective explanatory view showing a state in which an adhesive is applied to a piezoelectric element column of a piezoelectric element unit constituting a piezoelectric actuator of another embodiment of the liquid discharge head according to the present invention. It is a bottom face explanatory drawing of a diaphragm member similarly. FIG. 8 is a cross-sectional explanatory view of a piezoelectric actuator corresponding to a cross section taken along line BB in FIG. 7. FIG. 8 is an explanatory cross-sectional view of a main part of the head corresponding to a cross section taken along the line CC of FIG. 7. FIG. 10 is a schematic perspective explanatory view showing a state in which an adhesive is applied to a piezoelectric element column of a piezoelectric element unit constituting a piezoelectric actuator of still another embodiment of the liquid ejection head according to the present invention. 1 is an overall configuration explanatory view showing an example of an image forming apparatus according to the present invention including a liquid discharge head according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Flow path board 2 ... Vibrating plate member 3 ... Nozzle plate 4 ... Nozzle 6 ... Pressurizing liquid chamber 10 ... Piezoelectric actuator 11 ... Piezoelectric element unit 12 ... Piezoelectric element member 12A ... 2nd piezoelectric element pillar (non-driving piezoelectric element) Pillar)
12B: First piezoelectric element column (drive piezoelectric element column)
21 ... 1st adhesive agent 22 ... 2nd adhesive agent 23 ... Notch part (concave part)
211k, 211c, 211m, 211y ... recording head (liquid ejection head)

Claims (12)

A plurality of piezoelectric element columns formed at a predetermined pitch through the groove, and arranged in a row;
A diaphragm member adhesively bonded to the plurality of piezoelectric element columns;
The one piezoelectric element column and the diaphragm member are bonded with a first adhesive and a second adhesive, and the first adhesive has a higher bonding speed than the second adhesive, and the second adhesive The piezoelectric actuator is characterized in that the adhesive strength is stronger than that of the first adhesive.   2. The piezoelectric actuator according to claim 1, wherein the first adhesive is any one of a visible light curable adhesive, a two-component curable adhesive, a thermosetting adhesive, an ultraviolet curable adhesive, and a humidity curable adhesive. The piezoelectric actuator is a thermosetting adhesive.   3. The piezoelectric actuator according to claim 1, wherein the first adhesive is located on an end side of the second adhesive in a direction orthogonal to an arrangement direction of the plurality of piezoelectric element columns. Piezoelectric actuator. 4. The piezoelectric actuator according to claim 1, wherein the piezoelectric element column has a recess formed in a bonding portion of the second adhesive. 5.
  5. The piezoelectric actuator according to claim 4, wherein the concave portion is a notch opened toward an end portion.   6. The piezoelectric actuator according to claim 4, wherein the concave portion is formed in a range smaller than an inactive region of the piezoelectric element column.   6. The piezoelectric actuator according to claim 4, wherein the recess is formed in a range larger than an inactive region of the piezoelectric element column.   8. The piezoelectric actuator according to claim 1, wherein the first piezoelectric element bonded by the first and second adhesives and the second piezoelectric element bonded by the second adhesive are provided. A piezoelectric actuator comprising:   8. The piezoelectric actuator according to claim 1, wherein the first piezoelectric element column bonded by the first and second adhesives and the second piezoelectric element bonded by the second adhesive. A piezoelectric actuator comprising a column, wherein the first piezoelectric element column is formed with a recess in a bonding portion of the second adhesive, and the second piezoelectric element column is not formed with the recess.   10. The piezoelectric actuator according to claim 8, wherein the first piezoelectric element column is a piezoelectric element column to which no driving voltage is applied, and the second piezoelectric element column is a piezoelectric element column to which a driving voltage is applied. A piezoelectric actuator characterized by being.   11. A liquid ejection head that ejects liquid droplets from the nozzles by displacing a diaphragm that forms a wall surface of a liquid chamber that communicates with a nozzle that ejects liquid droplets with the piezoelectric actuator. A liquid discharge head, which is the piezoelectric actuator according to any one of the above.   An image forming apparatus comprising a liquid discharge head for discharging liquid droplets to form an image, wherein the liquid discharge head is the liquid discharge head according to claim 11.

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