Method of manufacturing head unit

A frame and an ink-jet head including a nozzle plate and a fixed plate are placed on a first jig having a first face and a second face parallel to the first face and located outside the first face when seen in a direction perpendicular to the first face while being at a predetermined distance from the first face with respect to the direction perpendicular to the first face, in such a manner that a portion of the frame other than a portion formed with an adhesive layer is in contact with the second face, that an ink ejection face of the nozzle plate is opposed to the first face, and that both ends of the fixed plate are in contact with the adhesive layer. Thereafter, the adhesive layer is cured under a state where the ink ejection face is in contact with the first face, so that a head unit is manufactured.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese Patent Application No. 2006-244106, which was filed on Sep. 8, 2006, the disclosure of which is herein incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing a head unit having an ink-jet head which ejects ink to a recording medium.

2. Description of Related Art

Japanese Unexamined Patent Publication No. 2005-186383 discloses an ink-jet head assembly including a plurality of ink-jet heads each having an elongated plate with both ends thereof not being in contact with other plates, and a frame to which each of the ink-jet heads is fixed via the elongated plate. Each of the ink-jet heads includes a head main body, a reservoir unit, and the elongated plate. The head main body has a passage unit and an actuator unit. The reservoir unit is fixed to an upper face of the passage unit. The elongated plate is fixed to an upper face of the reservoir unit. The passage unit is formed therein with a plurality of individual ink passages each extending from a manifold channel through a pressure chamber to a nozzle. The actuator unit applies pressure to ink in the pressure chamber.

In the ink-jet head assembly, a plurality of through holes are formed in the elongated plate of the ink-jet head. The through holes are formed through a thickness of the plate, and arranged along a lengthwise direction of the plate. On the upper face of the reservoir unit, threaded holes are formed at positions corresponding to the through holes. Bolts which are inserted through the respective through holes are screwed into the threaded holes, so that the elongated plate and the reservoir unit are fixed to each other while a flat lower face of the elongated plate is being in tight contact with the upper face of the reservoir unit. As a result, upper and lower faces of the reservoir unit are prevented from being bent in a direction perpendicular to a plane direction, and therefore upper and lower faces of the passage unit are corrected into parallel with the lower face of the elongated plate. This improves flatness of the lower face of the passage unit, that is, flatness of an ink ejection face in which a plurality of nozzles open.

SUMMARY OF THE INVENTION

According to the above-mentioned publication document, the reservoir unit is formed by five plates being bonded to each other with an adhesive. The passage unit is formed by nine plates being put in layers so as to form a plurality of individual ink passages. A plurality of holes corresponding to manifold channels, pressure chambers, nozzles, and the like are formed in the respective nine plates. If the nine plates are bonded to each other with an adhesive, there may be a variation among a thickness of the adhesive among the nine plates, a thickness of the adhesive between the passage unit and the reservoir unit, and a thickness of the adhesive among five plates of the reservoir unit. As a result, a distance between the elongated plate and the ink ejection face with respect to a direction perpendicular to the ink ejection face varies among the ink-jet heads. In an ink-jet head assembly having such ink-jet heads fixed to a frame, a distance between the frame and the ink ejection face varies among the ink-jet heads. If a printing is performed with a printer provided with such an ink-jet head assembly, a print quality decreases because an accuracy of a landing position of ink ejected from a nozzle varies among the ink-jet heads.

An object of the present invention is to provide a method of manufacturing a head unit which presents a constant distance between an ink ejection face and a frame having an ink-jet head fixed thereto.

According to an aspect of the present invention, there is provided a method of manufacturing a head unit, comprising an ink-jet head forming step, an adhesive layer forming step, a placing step, and an adhesive layer curing step. In the ink-jet head forming step, an ink-jet head having an ink passage extending from an ink supply port to a nozzle which ejects ink is formed by putting in layers a plurality of plates which includes a nozzle plate having an ink ejection face on which the nozzle is opened and a fixed plate to be fixed to a frame. The fixed plate has both ends thereof not being in contact with the other plates. In the adhesive layer forming step, an adhesive layer is formed on the frame. In the placing step, the frame and the ink-jet head are placed on a first jig having a first face and a second face which is parallel to the first face and located outside the first face when seen in a direction perpendicular to the first face while being at a predetermined distance from the first face with respect to the direction perpendicular to the first face, in such a manner that a portion of the frame other than a portion formed with the adhesive layer is in contact with the second face, that the ink ejection face is opposed to the first face, and that the both ends of the fixed plate are in contact with the adhesive layer. In the adhesive layer curing step, the adhesive layer is cured after the placing step, under a state where the ink ejection face is in contact with the first face.

In the aspect, in the adhesive layer curing step, the adhesive layer is cured under the state where the both ends of the fixed plate are in contact with the adhesive layer and the ink ejection face is in contact with the first face. Accordingly, a distance between the frame and the ink ejection face is constant because it is regulated as the predetermined distance between the first face and the second face of the first jig. Therefore, when a plurality of head units are manufactured using the first jig, a distance between the frame and the ink ejection face is the same in all the head units. As a result, in a recording apparatus such as a printer mounted with the respective head units by the frame, a level of the ink ejection face does not vary among the head units and therefore stable print quality can be obtained.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, some preferred embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1is an exploded perspective view of a head unit which has been manufactured by a manufacturing method according to a first embodiment of the present invention.

FIG. 2is a sectional view as taken along line II-II inFIG. 1. As shown inFIG. 1, a head unit70includes a frame71, and four ink-jet heads1fixed to the frame71.

The frame71is formed by a flat-plate member made of a metal, and has a rectangular shape elongated in a main scanning direction. The frame71has a through opening72formed at a center thereof. A shape of the through opening72is substantially the same as the shape of the frame. The through opening72has such a size that passage units4of the respective four ink-jet heads1are placeable. The frame71has, at each of its lengthwise ends, four positioning holes73which are arranged at regular intervals along a sub scanning direction. The frame71and the four ink-jet heads1are bonded to each other with interposition of an adhesive layer75(seeFIG. 11C), while being positioned relative to each other by means of the positioning holes73and positioning holes92awhich are formed in a later-described reservoir base plate92of each ink-jet head1. The head unit formed in this manner is mounted to an ink-jet printer (not shown) via the frame71.

Each of the ink-jet heads1has a substantially rectangular parallelepiped shape elongated in a main scanning direction. The four ink-jet heads1are arranged side by side in the sub scanning direction and in this state bonded to both lengthwise ends of the frame71. The ink-jet heads1are supplied with ink of different colors, respectively. For example, magenta ink, cyan ink, yellow ink, and black ink are supplied to the ink-jet heads1shown at the near side to the far side inFIG. 1, respectively. That is, the head unit70is mounted to a color ink-jet printer (not shown). Since all the ink-jet heads1have the same construction, a construction of one ink-jet head1will be described below.

As shown inFIG. 2, the ink-jet head1includes a head main body13, a reservoir unit90, a flexible printed circuit board (FPC)50, and a control board54. The head main body13has a passage unit4and an actuator unit21. The reservoir unit90is disposed on an upper face of the passage unit4and supplies ink into the passage unit4. The FPC50is mounted with a driver IC52which supplies a drive signal to the actuator unit21. The control board54is electrically connected to the FPC50.

As shown inFIG. 2, one end of the FPC50is electrically connected to an upper face of the actuator unit21. The control board54is disposed above the reservoir unit90in a horizontal manner. The other end of the FPC50is connected to a connector54aof the control board54. Based on a command from the control board54, the driver IC52supplies a drive signal to the actuator unit21through a wire provided in the FPC50.

An ink reservoir90awhich stores ink therein is formed inside the reservoir unit90. The ink reservoir90acommunicates with openings5bwhich are formed in an upper face of the passage unit4. Ink contained in the ink reservoir90ais accordingly supplied through the openings5ato the passage unit4.

The actuator unit21, the reservoir unit90, the control board54, and the FPC50are covered by side covers53and a head cover55which are made of a metal material, so that intrusion of ink or ink mist scattering outside is prevented. An elastic sponge51is interposed between a side face of the reservoir unit90and the FPC50. The sponge51presses the driver IC52to an inner face of the side cover53so that heat generated in the driver IC52is quickly dissipated to the outside through the side cover53and the head cover55. Thus, the side covers53and the head cover55function as a dissipation member, too.

Next, the head main body13will be described in detail.FIG. 3is a plan view of the head main body13.FIG. 4is an enlarged view of a region enclosed by an alternate long and short dash line inFIG. 3. InFIG. 4, for the purpose of easy understanding, pressure chambers10, apertures12, and nozzles8are illustrated with solid lines through they locate under the actuator units21and therefore actually should be illustrated with broken lines. As shown inFIG. 3, in a plan view, the passage unit4has a rectangular shape elongated in the main scanning direction. Four actuator units21each having a trapezoidal shape are bonded to the upper face of the passage unit4while being arranged in two rows in a zigzag pattern.

In a lower face of the passage unit4, that is, in an ink-ejection face4a, a plurality of nozzles8are opened in regions corresponding to where the respective actuator units21are bonded (seeFIG. 4). In the upper face of the passage unit4, a plurality of pressure chambers10are opened in regions where the respective actuator units21are bonded. The pressure chamber10has a substantially rhombic shape with its corners rounded. Both the nozzles8and the pressure chambers10are arranged in a matrix along two directions. Pressure chambers10corresponding to one actuator unit21constitute one pressure chamber group9.

As shown inFIGS. 3 and 4, manifold channels5and sub manifold channels5aare formed within the passage unit4. The manifold channels5communicate with the openings5b. The sub manifold channels5aare branched from the manifold channels5. In regions corresponding to where the actuator units21are bonded, the sub manifold channels5aextend along the lengthwise direction of the passage unit4. On the upper face of the passage unit4, the pressure chambers10are arranged along a direction of extension of the sub manifold channels5a, that is, along the lengthwise direction of the passage unit4, to form pressure chamber rows. With respect to a widthwise direction of the passage unit4, there are sixteen parallel pressure chamber rows extending in the lengthwise direction of the passage unit4. Each pressure chamber row included in one pressure chamber group9forms a line with a corresponding pressure chamber row included in a next nearest neighboring pressure chamber group9. On the ink ejection face, the nozzles8are arranged in the same manner as the pressure chambers10are.

Next, a cross-sectional structure of the head main body13will be described.FIG. 5is a sectional view as taken along line V-V inFIG. 4. As shown inFIG. 5, the head main body13is formed by the passage unit4and the actuator unit21being bonded to each other. The passage unit4has a layered structure of nine metal plates, namely, from the top, a cavity plate22, a base plate23, an aperture plate24, a supply plate25, manifold plates26,27,28, a cover plate29, and a nozzle plate30. Holes formed in the respective plates22to30constitute ink passages33within the passage unit4. The ink passages33extend from the openings5bto the respective nozzles8. The ink passages33include the manifold channels5, the sub manifold channels5a, and individual ink passages32. The individual ink passages32are passages each extending from an exit of a sub manifold channel5athrough an aperture and a pressure chamber10to a nozzle8. A plurality of the individual ink passages32are formed corresponding to the respective nozzles8. Each of the actuator units21is bonded to the upper face of the passage unit4so as to close openings of all the pressure chambers10included in a corresponding pressure chamber group9.

Next, the actuator unit21will be described.FIG. 6Ais a partial sectional view of the actuator unit21, andFIG. 6Bis a plan view of an individual electrode35. As shown inFIG. 6A, the actuator unit21includes three piezoelectric sheets41,42, and43each having a thickness of approximately 15 μm. The piezoelectric sheets41to43are disposed so as to extend over all the pressure chambers10included in a corresponding pressure chamber group9. This makes it possible that individual electrodes35corresponding to the respective pressure chambers10are arranged on the piezoelectric sheet41at a high density by using a screen printing technique for example. The piezoelectric sheets41to43are made of a lead zirconate titanate (PZT)-base ceramic material having ferroelectricity.

The individual electrode35has a thickness of approximately 1 μm, and includes a main electrode portion35aand an extending-out portion35b. As shown inFIG. 6B, the main electrode portion35ahas a substantially rhombic shape in a plan view which is substantially the same as but a slightly smaller than the pressure chamber10. The individual electrode35is disposed so as to fall within the pressure chamber10in a plan view. The extending-out portion35bextends out from an acute portion of the main electrode portion35ato the outside of the pressure chamber10, that is, to a position opposed to a wall portion22aof the cavity plate22which defines the pressure chambers10. A circular land36having a diameter of approximately 160 μm is provided on a surface of a distal end of the extending-out portion35b.

A common electrode34is disposed between the uppermost piezoelectric sheet41and the piezoelectric sheet42disposed thereunder. The common electrode34is formed substantially over an entire upper face of the piezoelectric sheet42, and grounded in an unillustrated region. As a consequence, a potential can be controlled independently for every individual electrode35.

The actuator unit21is of so-called unimorph type, and includes a plurality of actuators corresponding to the respective individual electrodes35.

Next, an operation of the actuator unit21will be described. When an ejection request is issued from the outside, the driver IC52selectively supplies a drive signal to actuators included in the actuator unit21. A portion of the actuator unit21corresponding to the actuator supplied with the drive signal deforms protrudingly toward a pressure chamber10. This raises pressure of ink contained in the pressure chamber, so that ink is ejected from a corresponding nozzle8.

Next, the reservoir unit90will be described.FIG. 7is a sectional view of the reservoir unit90along a longitudinal direction thereof. As shown inFIGS. 2 and 7, the reservoir unit90includes a lower reservoir95and an upper reservoir91. The lower reservoir95is bonded to the upper face of the passage unit4with a ultraviolet curing resin2sandwiched therebetween. The upper reservoir91is a made of a resin and disposed on an upper face of the lower reservoir95. The lower reservoir95and the upper reservoir91are fixed to each other by screwing.

The lower reservoir95is formed by three metal plates, a reservoir base plate92, a reservoir plate93, and an under plate94, being positioned in layers. In a plan view, the plates92to94have a rectangular shape elongated in the main scanning direction. With respect to the sub scanning direction, the plates92to94are shorter than a distance between the two side covers53, as shown inFIG. 2.

As shown inFIGS. 2 and 7, the reservoir base plate92is thicker than the plates93and94, and higher in strength and rigidity. With respect to the main scanning direction, the reservoir base plate92is longer than the plates93and94and extends on both sides, as shown inFIGS. 1 and 7. With respect to the main scanning direction, the reservoir plate93and the under plate94have substantially the same length as that of the nine plates22to30of the passage unit4. That is, among the plates22to30and the plates92to94which constitute the reservoir unit90and the passage unit4, the reservoir base plate92is longest with respect to the main scanning direction. The other plates22to30,93, and94have substantially the same length with respect to the main scanning direction.

Positioning holes92aare formed at both lengthwise ends of the reservoir base plate92. By positioning the positioning holes92ainto an exact overlap with the positioning holes73of the frame71, the respective ink-jet heads1are placed in predetermined positions in the frame71.

As shown inFIG. 7, a through hole61is formed in the reservoir base plate92. The through hole61connects an ink passage96formed in the upper reservoir91to an ink passage62formed in the reservoir plate93. A hole is formed in the reservoir plate93. The hole serves as the ink passage62which connects the through hole61to ten through holes63formed in the under plate94. In the under plate94, through holes63are formed at positions opposed to ten openings5bformed on the upper face of the passage unit4(seeFIG. 3). On a lower face of the under plate94, a recess94ais formed in a portion where the through holes63are not formed. Due to the recess94a, a gap appears between the passage unit4and the lower reservoir95. The actuator unit21is disposed in the gap.

The upper reservoir91has an ink supplier96awhich is shown in an upper-left portion ofFIG. 7. An ink supply port is formed on an upper face of the ink supplier96a. Through the ink supply port of the ink supplier96a, ink is supplied to the ink passage96within the upper reservoir91. A damper film101is provided at a part of a lower face of the upper reservoir91. The damper film101is spaced from the reservoir base plate92by a predetermined distance, and extends in parallel with the reservoir base plate92. The damper film101damps vibration traveling through ink in the ink passage96. A filter97is provided in a middle of the ink passage96so as to be opposed to the damper film101. Ink supplied through the ink supply port of the ink supplier96ahas foreign materials removed therefrom by the filter97, and flows into the lower reservoir95.

The reservoir unit90has the ink passage96formed in the upper reservoir91, and the ink reservoir90aformed in the lower reservoir95. The ink reservoir90ais made up of the through hole61, the ink passage62, and the through holes63. Ink which has been supplied through the ink supply port of the ink supplier96ainto the reservoir unit90is supplied through the through holes63and the ink supply ports5binto the passage unit4.

Next, a method of manufacturing the head unit70will be described.

First, a process of forming the ink-jet head1will be described.FIG. 8is a flowchart showing a process of forming the ink-jet head1according to the first embodiment of the present invention.FIGS. 9A,9B, and9C timewisely show a process of forming the ink-jet head1according to the first embodiment of the present invention. To form the ink-jet head1, parts, namely, the passage unit4, the actuator unit21, and the reservoir unit90, are separately prepared and then the parts are assembled to each other.

A preparation of the passage unit4will be described. First, in S1ofFIG. 8, the respective plates22to30constituting the passage unit4are etched using a patterned photoresist as a mask, to thereby form holes which will constitute the ink passage33shown inFIG. 5(hole forming step).

Then, in S2, an epoxy-based thermosetting adhesive is applied to lower faces of the respective plates22to29other than the nozzle plate30(adhesive applying step). Then, in S3, the nine plates22to30are put in layers with the thermosetting adhesive sandwiched therebetween so as to form the ink passages33(passage unit laminating step).

Then, in S4, a layered body obtained in S3, that is, a precursor of the passage unit4made up of the nine plates22to30is heated under pressure up to a temperature equal to or higher than a curing temperature of the thermosetting adhesive. The thermosetting adhesive is thereby cured to bond the nine plates22to30to one another thereby forming the passage unit4(passage unit forming step).

A preparation of the actuator unit21will be described. First, three green sheets made of piezoelectric ceramics are prepared. A preparation of the green sheets includes in advance an estimated amount of contraction which will be caused by sintering. On one of the green sheets, a conductive paste is screen-printed in a pattern of the common electrode34. Then, while the green sheets are positioned to each other by use of a jig, the green sheet printed with the conductive paste in the pattern of the common electrode34is put under the green sheet printed with no conductive paste and in addition the other green sheet printed with no conductive paste is put under the green sheet printed with the conductive paste in the pattern of the common electrode34(S5).

Then, in S6, a layered body obtained in S5is degreased in the same manner as for known ceramics, and baked at a predetermined temperature. Thereby, the three green sheets turn into the piezoelectric sheets41to43, and the conductive paste turns into the common electrode34. Subsequently, a conductive paste is screen-printed in a pattern of the individual electrodes35, on the uppermost piezoelectric sheet41. Further, the conductive paste is baked, to form the individual electrodes35on the piezoelectric sheet41. Thereafter, gold including a glass frit is printed on a surface of a distal end of an extending-out portion35bof each individual electrode35, to form the land36. In this way, the actuator unit21shown inFIGS. 6A and 6Bis completed.

A preparation of the reservoir unit90will be described. First, a resin member for the upper reservoir91is formed by means of a known injection molding method, and then the filter97and the damper film101are attached to predetermined positions, so that the upper reservoir91is prepared (S7).

Then, in S8, the respective plates92to94constituting the lower reservoir95are etched using a patterned photoresist as a mask, to thereby form the recess94aand holes which will constitute the ink reservoir90ashown inFIG. 7(hole forming step). Here, to form the holes in the respective plates92to94, a pressing process may be adopted instead of an etching process.

Then, in S9, an epoxy-based thermosetting adhesive is applied to lower faces of the two plates92and93other than the under plate94(adhesive applying step). Here, on the lower face of the reservoir base plate92, the thermosetting adhesive is not applied to both lengthwise ends of the reservoir base plate92, that is, to portions not opposed to the reservoir plate93. Then, in S10, the plates92to94are put in layers with the thermosetting adhesive sandwiched therebetween so as to form the ink reservoir90a(reservoir unit laminating step).

Then, in S11, a layered body obtained in S10, that is, a precursor of the lower reservoir95made up of the three plates92to94is heated under pressure up to a temperature equal to or higher than a curing temperature of the thermosetting adhesive. The thermosetting adhesive is thereby cured to bond the three plates92to94to one another thereby forming the lower reservoir95(reservoir unit forming step). Then, the upper reservoir91is placed on the lower reservoir95so as to make communication between the ink reservoir90aand the ink passage96, and the upper reservoir91and the lower reservoir95are fixed to each other with a screw. In this way, the reservoir unit90is completed.

In a case where a heat-resistance temperature of the resin member and the damper film101of the upper reservoir91is higher than the curing temperature of the thermosetting adhesive, it may be possible to fix the upper reservoir91to the precursor of the lower reservoir95obtained in S10with a screw and then heating the precursor of the lower reservoir95under pressure to cure the thermosetting adhesive.

The passage unit preparation process S1to S4, the actuator unit preparation process S5and S6, and the reservoir unit preparation process S7to S11are performed independently of one another, and any one of them may precede another, or alternatively they may be performed concurrently.

Subsequently, in S12, an epoxy-based thermosetting adhesive is applied, using a bar coater, to regions of an upper face of the passage unit4obtained in S4where actuator units21will be bonded. Here, application of the adhesive may be done through a transfer method, not limited to using a bar coater.

Then, in S13, four actuator units21are placed on the upper face of the passage unit4with the thermosetting adhesive applied in S12sandwiched therebetween. The respective actuator units21are positioned relative to the passage unit4in such a manner that the individual electrodes35and the pressure chambers10are opposed to each other. This positioning is based on positioning marks (not shown) which have been formed in the passage unit4and the actuator unit21beforehand during the steps S1to S6.

Then, in S14, a layered body made up of the passage unit4and the actuator units21obtained in S13, that is, a precursor of the head main body13, is heated under pressure up to a temperature equal to or higher than a curing temperature of the thermosetting adhesive. The thermosetting adhesive is thereby cured, to bond the passage unit4and the actuator units21to each other. Then, in S15, the precursor of the head main body13is self-cooled. Then, in S16, wires of the FPC50are bonded to the lands36of the actuator units21. In this way, the head main body13is completed.

Then, in S17, a ultraviolet curing resin2is applied, in a predetermined thickness, to a portion of a lower face of the reservoir unit90where the recess94ais not formed (resin applying step). The ultraviolet curing resin2is crosslink-cured by UV light energy. The ultraviolet curing resin2is higher in viscosity than the thermosetting adhesives applied in S2, S9, and S12, and can be applied in a predetermined thickness.

Here, a jig105which is used in S18will be described. As shown inFIG. 9A, the jig105includes a supporter106which supports the ink ejection face4a, and a pair of walls107which protrude upward from both sides of the supporter106. Thus, the jig105has a recessed shape in a cross-sectional view. The supporter106has a bottom face106awhich is in parallel with the ink ejection face4aand slightly larger than one ink ejection face4a. An upper face107aof the wall107is in parallel with the bottom face106a. In a plan view, that is, when seen in a direction perpendicular to the bottom face106a, the upper face107aof the wall107is located outside the bottom face106a. In addition, with respect to a vertical direction, that is, a direction perpendicular to the bottom face106a, the upper face107aof the wall107is at a predetermined distance T from the bottom face106a. The distance T is substantially equal to a total thickness of the nine plates22to30constituting the passage unit4, the two plates93and94other than the reservoir base plate92constituting the lower reservoir95, the thermosetting adhesives existing between the respective plates, and the resin2after cured.

In S18, the head main body13is placed on the jig105in such a manner that the ink ejection face4aof the passage unit4is in contact with the bottom face106aof the supporter106, as shown inFIGS. 9A and 9B. Then, the reservoir unit90is put on the passage unit4while being positioned relative to the head main body13and the jig105so as to make communication between the through holes63formed in the under plate94and the ink supply ports5bof the passage unit4and also so as to make opposition between the upper faces107aof the walls107and the lower faces of both lengthwise ends of the reservoir base plate92(laminating step). At this time, there is a narrow clearance between the upper face107aof the jig105and the lower faces of the both lengthwise ends of the reservoir base plate92, as shown inFIG. 9B. In this step, depending on a viscosity of the ultraviolet curing resin2, a thickness of the ultraviolet curing resin2may decrease due to weight of the reservoir unit90to bring the lower faces of the both lengthwise ends of the reservoir base plate92into contact with the upper faces107.

Then, as shown inFIG. 9C, while the ink ejection face4ais kept in contact with the bottom face106a, a layered body99made up of the head main body13and the reservoir unit90is pressed toward the jig105, that is, pressed downward so as to bring the lower faces of the both lengthwise ends of the reservoir base plate92into contact with the upper faces107aof the walls107. As a result of this pressing, the thickness of the ultraviolet curing resin2decreases and the lower faces of the both lengthwise ends of the reservoir base plate92comes into contact with the upper faces107a, even though in S18there has been a clearance between the upper faces107aof the jig105and the lower faces of the both lengthwise ends of the reservoir base plate92as shown inFIG. 9B. Then, in S19, under this state where the ink ejection face4ais in contact with the bottom face106awhile the lower faces of the both lengthwise ends of the reservoir base plate92are in contact with the upper faces107a, a UV light irradiator (not shown) irradiates UV light toward the ultraviolet curing resin2to cure the ultraviolet curing resin2(resin curing step). As a consequence, a distance between the ink ejection face4aand the lower face of the reservoir base plate92becomes substantially equal to the distance T between the bottom face106aand the upper face107aof the jig105.

Thereafter, the FPC50and the control board54are electrically connected via the connector54a, and besides the side covers53and the head cover55are assembled on the passage unit4so as to cover the actuator unit21, the reservoir unit90, the control board54, and the FPC50, as shown inFIG. 2. In this way, the ink-jet head1is completed.

Subsequently, a description will be given to a method of manufacturing a head unit70by bonding four ink-jet heads1to the frame71.FIG. 10is a flowchart showing a method of manufacturing the head unit70.FIGS. 11A,11B, and11C timewisely show a method of manufacturing the head unit70.

A preparation of the frame71will be described. First, in S20, in a rectangular flat plate made of a metal which will be the frame71, a through hole72is formed by a die-stamping process. Then, in S21, at each lengthwise end of the flat plate, four positioning holes73are formed at regular intervals along a widthwise direction of the flat plate. The intervals between the positioning holes73are set so as to cause no interference among the four ink-jet heads1which are positioned with their positioning holes92aoverlapping the corresponding positioning holes73, respectively. In this way, the frame71is completed. The frame preparation process S20and S21and the ink-jet head forming process S1to S19are performed independently of each other, and any one of them may precede the other, or alternatively they may be performed concurrently.

Then, in S22, a thermosetting adhesive is applied to a portion of an upper face of the frame71surrounding each positioning hole73, to thereby form an adhesive layer75having a predetermined thickness, as shown inFIG. 11A(adhesive layer forming step) In this embodiment, the thermosetting adhesive used at this time is, like the ultraviolet curing resin2, higher in viscosity than the thermosetting adhesives applied in S2, S9, and S12, and can be applied in a predetermined thickness.

Here, a jig125which is used in S23will be described. As shown inFIG. 11A, like the jig105described above, the jig125includes a supporter126which supports the ink ejection face4a, and a pair of walls127which protrude upward from both sides of the supporter126. Thus, the jig125has a recessed shape in a cross-sectional view. The supporter126has a bottom face126awhich is in parallel with the ink ejection face4aand slightly larger than the four ink ejection faces4a. An upper face127aof the wall127is in parallel with the bottom face126a. In a plan view, that is, when seen in a direction perpendicular to the bottom face126a, the upper face127aof the wall127is located outside the bottom face126a. In addition, with respect to the vertical direction, that is, the direction perpendicular to the bottom face126a, the upper face127aof the wall127is at a predetermined distance U from the bottom face126a. The distance U is a value obtained by subtracting, from the distance T shown inFIG. 9A, a thickness of the frame71and a thickness of the adhesive layer75which has become smaller than in S22due to a later-described pressing process (seeFIG. 11C). The jig125differs from the jig105described above in that it has eight projections128which project upward from the bottom face127a. The projections128are provided at regular intervals with respect to a direction perpendicularly crossing the drawing sheet ofFIG. 11A. Four projections128are provided on each of the pair of walls127. The projections128are formed so as to correspond to the positioning holes92aof the four heads1and the positioning holes73of the frame71.

In S23, as shown inFIGS. 11A and 11B, the projections128are inserted into the respective positioning holes73, and the frame71is placed on the jig125in such a manner that a lower face of the frame71, that is, a face of the frame71opposite to its face formed with the adhesive layer75is in contact with the upper face127a. Then, the respective four ink-jet heads1are placed on the jig125in such a manner that the projections128are inserted into the positioning holes92a, the ink ejection faces4aare opposed to the bottom face126a, and the lower faces of the both lengthwise ends of the reservoir base plate92are in contact with the adhesive layer75(placing step). At this time, the ink ejection faces4aare spaced from the bottom face126a, as shown inFIG. 11B. This is because, as described above, the distance U is a value obtained by subtracting, from the distance T, a total thickness of the frame71and the adhesive layer75which has become smaller in thickness than in S22due to a later-described pressing process (seeFIG. 11C). In this step, depending on a viscosity of the adhesive layer75, a thickness of the adhesive layer75may decrease due to weight of the reservoir base plate92and the upper reservoir91to bring the ink ejection face4ainto contact with the bottom face126a.

Then, as shown inFIG. 11C, the reservoir base plates92of the respective ink-jet heads1are pressed toward the jig125, that is, pressed downward. As a result of this pressing, the thickness of the adhesive layer75decreases and the ink ejection face4acomes into contact with the bottom face126a, even though in S23there has been a clearance between the ink ejection face4aand the bottom face126aas shown inFIG. 11B. Then, in S24, under this state where the ink ejection face4ais in contact with the bottom face126awhile the lower faces of the both lengthwise ends of the reservoir base plate92are in contact with the adhesive layer75, the four ink-jet heads1and the frame71are heated to cure the adhesive layer (adhesive layer curing step). As a consequence, a distance between the lower face of the frame71and the ink ejection face4abecomes substantially equal to the distance U between the bottom face126aand the upper face127aof the jig125. In this way, the head unit70is manufactured.

As thus far described above, in the method of manufacturing the head unit70according to this embodiment, the adhesive layer75is cured in the adhesive layer curing step S24while the lower faces of the both lengthwise ends of the reservoir base plate92are in contact with the adhesive layer75and the ink ejection faces4aare in contact with the bottom face126a. Accordingly, a distance between the lower face of the frame71and the ink ejection faces4ais constant because it is regulated as the distance U between the bottom face126aand the upper face127aof the jig125. Therefore, when a plurality of head units70are manufactured using the same jig125, a distance between the lower face of the frame71and the ink ejection faces4ais the same in all the head units70. As a result, in a recording apparatus such as a printer mounted with the respective head units70by the frame71, a level of the ink ejection face4adoes not vary among the head units70and therefore stable print quality can be obtained.

The head unit70includes the four ink-jet heads1. In the placement step S23, the respective four ink-jet heads1are placed on the jig125in such a manner that the ink ejection faces4aare opposed to the bottom face126aand the lower faces of the both lengthwise ends of the is reservoir base plate92are in contact with the adhesive layer75. In the adhesive layer curing step S24, under the state where the ink ejection faces4aare in contact with the bottom face126awhile the lower faces of the both lengthwise ends of the reservoir base plate92are in contact with the adhesive layer75, the adhesive layer75is cured and thus the four ink-jet heads1are bonded to the frame71through the adhesive layer75. As a result, the four ink-jet heads1included in one head unit70have their ink ejection faces4apositioned at the same level.

In the resin application step S17, the ultraviolet curing resin2is applied onto the lower face of the reservoir unit90, that is, onto the plate94which is located between the reservoir base plate92and the nozzle plate30. Then, in the lamination step S18, the reservoir unit90is put on the passage unit4with the ultraviolet curing resin2sandwiched therebetween. Then, in the resin curing step S19, the ultraviolet curing resin2is cured under the state where the ink ejection faces4aare in contact with the bottom face106awhile the lower faces of the both lengthwise ends of the reservoir base plate92are in contact with the upper face107a. Accordingly, a distance between the lower face of the reservoir base plate92and the ink ejection face4ais constant because it is regulated as the distance T between the bottom face106aand the upper face107aof the jig105. Therefore, when a plurality of ink-jet heads1are formed using the same jig105, a distance between the lower face of the reservoir base plate92and the ink ejection face4abecomes the same in all the ink-jet heads1. As a result, in a recording apparatus such as a printer mounted with the head unit70by the frame71, the ink ejection faces4aof the four ink-jet heads1included in the head unit70are at the same level. Therefore, more stable print quality can be obtained.

The reservoir base plate92is most rigid among all the plates92to94which constitute the lower reservoir95, and not easily deformed by external force. Accordingly, in S10and S11, the plates93and94are bonded while following the reservoir base plate92. Thus, warping of the three plates92to94constituting the lower reservoir95can be suppressed.

All the plates92to94which constitute the lower reservoir95are made of the same material, and the reservoir base plate92is thickest among the plates92to94. By using the same material for the plates92to94and making the reservoir base plate92thicker than the other plates like this, the reservoir base plate92can easily obtain higher rigidity and therefore the above-described effects can be obtained.

After the reservoir unit90and the passage unit4are prepared separately, the reservoir unit90is put on the passage unit4as shown inFIGS. 9A to 9C, to form the layered body99. In such a case, handling of members is easier than in a case where the plates constituting the reservoir unit90and the passage unit4are put in layers at one time to form the layered body.

In the resin application step S17, the ultraviolet curing resin2is applied to the lower face of the reservoir unit90. Then, in the lamination step S18, the reservoir unit90is put on the passage unit4with the ultraviolet curing resin2sandwiched therebetween. Accordingly, even though the reservoir unit90and the passage unit4are prepared separately and then put in layers to form the ink-jet head1, a distance between the ink ejection face4aand the lower face of the reservoir base plate92is constant.

The jig125has projections128which are inserted into the positioning holes73of the frame71and the positioning holes92aof the reservoir base plate92. Therefore, a position of the frame71bonded to the reservoir base plate92can be stabilized.

Next, a description will be given to a method of manufacturing a head unit according to a second embodiment of the present invention.FIGS. 12A,12B, and12C timewisely show a process of forming an ink-jet head according to the second embodiment of the present invention.FIG. 13is a flowchart showing a method of manufacturing a head unit according to the second embodiment of the present invention.FIGS. 14A and 14Btimewisely show the method of manufacturing the head unit according to the second embodiment of the present invention. This embodiment is substantially the same as the first embodiment except that a positional relationship in the vertical direction between the reservoir base plate92and the frame71is reverse to in the first embodiment. The same members as in the first embodiment will be denoted by the same reference numerals, and specific descriptions thereof will be omitted.

A process of forming the ink-jet head1according to this embodiment will be described. First, the head main body13and the reservoir unit90are prepared through steps S1to S17which are the same as in the first embodiment (seeFIG. 8).

Here, a jig205which is adopted in this embodiment will be described with reference toFIG. 12A. The jig205is used in both a lamination step S18and a placement step G23.

As shown inFIG. 12A, the jig205includes a supporter206which supports the ink ejection face4a, and a pair of walls207which protrude upward from both sides of the supporter206. Thus, the jig205has a recessed shape in a cross-sectional view. The supporter206has a bottom face206awhich is in parallel with the ink ejection face4aand slightly larger than the four ink ejection faces4a. An upper face207aof the wall207is in parallel with the bottom face206a. In a plan view, that is, when seen in a direction perpendicular to the bottom face206a, the upper face207aof the wall207is located outside the bottom face206a. In addition, with respect to the vertical direction, that is, the direction perpendicular to the bottom face206a, the upper face207aof the wall207is at a predetermined distance V from the bottom face206a. The distance V is substantially equal to a total thickness of the nine plates22to30constituting the passage unit4, the three plates92to94constituting the lower reservoir95, the thermosetting adhesives existing between the respective plates, the resin2after cured, and an adhesive275after cured. The wall207has a step surface207bwhich extends in parallel with the bottom face206a. The step surface207bis located between the bottom face206aand the upper face207ain a plan view, and located between the bottom face206aand the upper face207awith respect to the vertical direction. The step surface207bis at a predetermined distance T from the bottom face206awith respect to the vertical direction. The distance T is the same as the predetermined distance T of the first embodiment, and equal to a value obtained by subtracting, from the distance V, a thickness of the reservoir base plate92and a thickness of the resin275after cured.

The jig205has eight projections228which project upward from the step surfaces207b. Like the projections128of the first embodiment, the projections228are provided at regular intervals with respect to a direction perpendicularly crossing the drawing sheet ofFIG. 12A. Four projections228are provided on each of the pair of walls207, so as to correspond to the positioning holes92aof the four heads1and the positioning holes73of the frame71.

In this embodiment, in S18, the head main body13is placed on the jig205in such a manner that the ink ejection face4aof the passage unit4is in contact with the bottom face206aof the supporter206, as shown inFIGS. 12A and 12B. Then, the projections228are inserted into the positioning holes92aof the reservoir base plate92while lower faces of both lengthwise ends of the reservoir base plate92are opposed to the step surfaces207bof the walls207. Thus, the reservoir unit90is put on the passage unit4(laminating step). At this time, based on positioning of the reservoir unit90made by the projections228, the head main body13is positioned on the bottom face206aso as to make communication between the through holes63formed in the under plate94and the ink supply ports5bof the passage unit4. As shown inFIG. 12B, there is a narrow clearance between the step surface207bof the jig205and the lower faces of the both lengthwise ends of the reservoir base plate92. In this step, depending on a viscosity of the ultraviolet curing resin2, a thickness of the ultraviolet curing resin2may decrease due to weight of the reservoir unit90to bring the lower faces of the both lengthwise ends of the reservoir base plate92into contact with the step surfaces207b.

Then, as shown inFIG. 12C, while the ink ejection face4ais kept in contact with the bottom face206a, a layered body99made up of the head main body13and the reservoir unit90is pressed toward the jig205, that is, pressed downward so as to bring the lower faces of the both lengthwise ends of the reservoir base plate92into contact with the step surfaces207b. As a result of this pressing, the thickness of the ultraviolet curing resin2decreases and the lower faces of the both lengthwise ends of the reservoir base plate92come into contact with the step surfaces207b, even though in S18there has been a clearance between the step surfaces207band the lower faces of the both lengthwise ends of the reservoir base plate92as shown inFIG. 12B. Then, in S19, under this state where the ink ejection face4ais in contact with the bottom face206awhile the lower faces of the both lengthwise ends of the reservoir base plate92are in contact with the step surfaces207b, a UV light irradiator (not shown) irradiates UV light toward the ultraviolet curing resin2to cure the ultraviolet curing resin2(resin curing step). As a consequence, a distance between the ink ejection face4aand the lower face of the reservoir base plate92becomes substantially equal to the distance T between the bottom face206aand the step surface207bof the jig205.

Thereafter, the FPC50and the control board54are electrically connected via the connector54a, and besides the side covers53and the head cover55are assembled on the passage unit4so as to cover the actuator unit21, the reservoir unit90, the control board54, and the FPC50, as shown inFIG. 2. In this way, the ink-jet head1is completed.

Subsequently, a description will be given to a method of manufacturing a head unit by bonding four ink-jet heads1to the frame71.

First, as shown inFIG. 13, the frame71is prepared through steps S20and S21which are the same as in the first embodiment (seeFIG. 10).

Then, in G22, a thermosetting adhesive is applied to a portion of a lower face of the frame71surrounding each positioning hole73, to thereby form an adhesive layer275having a predetermined thickness, as shown inFIG. 14A(adhesive layer forming step). The thermosetting adhesive used at this time has high viscosity like in the first embodiment.

Then, in G23, the projections228are inserted into the positioning holes73, so that the frame71is placed on the jig205in such a manner that lower faces of both lengthwise ends of the frame71are, in their portions where no adhesive layer275is formed, opposed to the upper face207a(placing step). At this time, the adhesive layer275comes into contact with upper faces of both lengthwise ends of the reservoir base plate92. There is a narrow clearance between the upper face207aand the lower faces of the both lengthwise ends of the frame71. In this step, depending on a viscosity of the adhesive layer275, a thickness of the adhesive layer275may decrease due to weight of the frame71to bring the lower faces of the both lengthwise ends of the frame71into contact with the upper face207a.

Then, as shown inFIG. 14B, the frame71is pressed toward the jig205, that is, pressed downward. As a result of this pressing, the thickness of the adhesive layer275decreases and the lower faces of the both widthwise ends of the frame71comes into contact with the upper face207a, even though in G23there has been a clearance between the upper face207aand the lower faces of the both widthwise ends of the frame71. Then, a step S24which is the same as in the first embodiment is performed. In S24, under a state where the ink ejection face4ais in contact with the bottom face206a, the lower faces of the both lengthwise ends of the reservoir base plate92are in contact with the step surfaces207b, the upper faces of the both lengthwise ends of the reservoir base plate92is in contact with the adhesive layers275, and the lower face of the both lengthwise ends of the frame71are in contact with the upper face207a, the four ink-jet heads1and the frame71are heated to cure the adhesive layers275(adhesive layer curing step). As a consequence, a distance between the ink ejection face4aand the lower face of the frame71becomes substantially equal to the distance V between the bottom face206aand the upper face207aof the jig205. In this way, the head unit is manufactured.

As thus far described above, in the method of manufacturing the head unit according to this embodiment, forming the ink-jet head1using the jig205is continuously followed by bonding the frame71to the ink-jet head1using the jig205, without moving the ink-jet head1away from the jig205. Since the same jig205is used for forming the ink-jet head1and for bonding the frame71to the ink-jet head1, a total process involved in manufacturing the head unit can be simplified and in addition costs for a jig is reduced to thereby reduce costs for manufacturing a head unit, as compared with when separate jigs are used. Besides, using the single jig205serves to relieve a problem of unevenness in size among jigs which may occur when a plurality of jigs are used. This can improve accuracy of a distance between the lower face of the frame71and the ink ejection face4a. Thus, a further higher-quality printing can be realized.

Next, a description will be given to a method of manufacturing a head unit according to a third embodiment of the present invention.FIG. 15is a flowchart showing a process of forming an ink-jet head, in a method of manufacturing a head unit according to a third embodiment of the present invention. A manufacturing method of this embodiment is the same as of the first embodiment except for a process of forming an ink-jet head. The same steps as in the first embodiment shown inFIG. 8will be denoted by the same reference numerals, and specific descriptions thereof will be omitted.

In this embodiment, a thermosetting resin is used for bonding the reservoir unit90and the head main body13to each other, although the ultraviolet curing resin2is used therefor in the first embodiment. The thermosetting adhesives existing among the respective nine plates22to30which constitute the passage units4, among the respective three plates92to94which constitute the lower reservoir95, between the passage unit4and actuator unit21, and the thermosetting resin disposed between the reservoir unit90and the passage unit4are cured simultaneously.

First, as shown inFIG. 15, steps S1to S3which are the same as in the first embodiment are performed, to form a precursor of the passage unit4made up of the nine plates22to30. Next, steps S5and S6which are the same as in the first embodiment are performed, to prepare the actuator unit21.

Then, through steps S8to S10which are the same as in the first embodiment, a precursor of the lower reservoir95made up of the three plates92to94is formed.

Then, steps F9and F10which are substantially the same as the steps S12and S13of the first embodiment are performed. In F9, an epoxy-based thermosetting adhesive is applied to regions of an upper face of the precursor of the passage unit4obtained in S3where actuator units21will be bonded. In F10, four actuator units21are placed on the upper face of the precursor of the passage unit4with the thermosetting adhesive applied in F9sandwiched therebetween. At this time, the actuator units21are positioned in the same manner as in the first embodiment. Thereby, a precursor of the head main body13is formed.

Then, a step S16which is the same in the first embodiment is performed, to bond wires of the FPC50to the lands36of the actuator units21.

Then, in F12, a thermosetting resin2is applied, in a predetermined thickness, to a portion of a lower face of the precursor of the lower reservoir95where the recess94ais not formed (resin applying step). The thermosetting resin is cured by being heated up to a curing temperature or higher. The thermosetting resin is higher in viscosity than the thermosetting adhesives applied in S2, S9, and F9, and can be applied in a predetermined thickness.

Then, in F13, the precursor of the head main body13is placed on the jig105in such a manner that a lower face of the precursor of the head main body13, that is, the ink ejection face4a, is in contact with the bottom face106aof the supporter106of the jig105which is the same jig105as in the first embodiment. Then, the precursor of the lower reservoir95is put on the precursor of the head main body13with the thermosetting resin interposed therebetween, while being positioned relative to the precursor of the head main body13and the jig105so as to make communication between the through holes63formed in the under plate94and the ink supply ports5bof the passage unit4and also so as to make opposition between the upper faces107aof the walls107and lower faces of both lengthwise ends of the reservoir base plate92(laminating step). At this time, like in the first embodiment, there is a narrow clearance between the upper face107aand the lower faces of the both lengthwise ends of the reservoir base plate92.

Then, while the ink ejection face4ais kept in contact with the bottom face106a, a layered body obtained in F13made up of the precursor of the head main body13and the precursor of the lower reservoir95is pressed toward the jig105, that is pressed downward so as to bring the lower faces of the both lengthwise ends of the reservoir base plate92into contact with the upper faces107aof the walls107. As a result of this pressing, the thickness of the thermosetting resin decreases and the lower faces of the both lengthwise ends of the reservoir base plate92come into contact with the upper faces107a, even though in F13there has been a clearance between the upper faces107aof the jig105and the lower faces of the both lengthwise ends of the reservoir base plate92. Then, in F14, under this state where the ink ejection face4ais in contact with the bottom face106awhile the lower faces of the both lengthwise ends of the reservoir base plate92are in contact with the upper faces107a, the layered body obtained in F13is heated, to cure the thermosetting resin (resin curing step). This heating also cures the thermosetting resins existing among the respective nine plates22to30which constitute the passage units4, among the respective three plates92to94which constitute the lower reservoir95, and between the passage unit4and actuator unit21. Consequently, a layered body made up of the head main body13and the lower reservoir95is obtained. A distance between the ink ejection face4aand the lower face of the reservoir base plate92becomes substantially equal to the predetermined distance T between the bottom face106aand the upper face107aof the jig105.

Then, through a step S7which is the same as in the first embodiment, the upper reservoir91is formed. Then, in F16, the upper reservoir91is placed on the lower reservoir95obtained in F14so as to make communication between the ink reservoir90aand the ink passage96, and the upper reservoir91and the lower reservoir95are fixed to each other with a screw. Thereby, a layered body of the head main body13and the reservoir unit90is formed.

Thereafter, the FPC50and the control board54are electrically connected via the connector54a, and besides the side covers53and the head cover55are assembled on the passage unit4so as to cover the actuator unit21the reservoir unit90, the control board54, and the FPC50, as shown inFIG. 2. In this way, the ink-jet head1is completed.

As thus far described above, in the method of manufacturing the head unit according to this embodiment, a plurality of plates included in the ink-jet head1are cured and bonded at one time in the resin curing step F14. As a result, as compared with in the first and second embodiments, a process of forming the ink-jet head1can be simplified and performed efficiently in a shorter period of time.

It suffices that the head unit70includes one or more ink-jet heads1. The number of ink-jet heads1included is not limited to four.

The frame71may be a plate member not having the through hole72. Various constructions are adoptable as long as they can fix the ink-jet head1.

It may not always necessary that the reservoir base plate92is thickest among the plates92to94constituting the lower reservoir95. The reservoir base plate92may have the same thickness as that of the other plates93and94.

A plate fixed to the frame71is not limited to the reservoir base plate92. The plate may be any of the plates constituting the ink-jet head1other than the nozzle plate30, as long as both ends thereof are not in contact with the other plates.

The projections128may not be formed on the upper face127aof the jig125. In such a case, the positioning holes73and92aof the frame71and the reservoir base plate92may be omitted.

In a case where members included in the ink-jet head1, such as the upper reservoir91, the control board54and the like, have heat resistance lower than the curing temperature of the thermosetting adhesive which forms the adhesive layer75,275, the adhesive layer75,275may be formed by a ultraviolet curing resin. In such a case, in the adhesive layer curing step S24, UV light is irradiated and heating is not performed. Therefore, there is no heat influence on the upper reservoir91, the control board54, and the like. Alternatively, it may be possible that the upper reservoir91, the control board54, and the like are not mounted in the ink-jet head forming process but they are mounted after the frame71is bonded via the adhesive layers75,275to a layered body made up of the passage unit4, the actuator unit21, and the lower reservoir95. This provides a greater degree of freedom in selecting a material for bonding the respective members.

A material for bonding the passage unit4and the reservoir unit90to each other may not necessarily be higher in viscosity than the thermosetting adhesives disposed among the respective nine plates22to30which constitute the passage units4, among the respective three plates92to94which constitute the lower reservoir95, and between the passage unit4and actuator unit21. For example, the material may have a viscosity equal to or lower than the viscosity of the above-described thermosetting adhesives. In terms of costs, it is more advantageous that the passage unit4and the reservoir unit90are bonded to each other using the same adhesive as disposed among the respective plates22to30, among the respective plates92to94, and between the passage unit4and actuator unit21, than using a different material. In a case where the passage unit4and the reservoir unit90are bonded to each other using a material of lower viscosity, in S18of the first embodiment, a thickness of the material decreases due to weight of the reservoir unit90to bring the lower faces of the both lengthwise ends of the reservoir base plate92into contact with the upper faces107aof the walls107. In a case where the passage unit4and the reservoir unit90are bonded to each other using a material of lower viscosity, in S18of the second embodiment, a thickness of the material decreases due to weight of the reservoir unit90to bring the lower faces of the both lengthwise ends of the reservoir base plate92into contact with the step surfaces207bof the walls207. In a case where the passage unit4and the reservoir unit90are bonded to each other using a material of lower viscosity, in F13of the third embodiment, a thickness of the material decreases due to weight of the precursor of the lower reservoir95to bring the lower faces of the both lengthwise ends of the reservoir base plate92into contact with the upper faces107aof the walls107. Therefore, it is not necessary to perform a pressing after S18and F13.

A material used for bonding the passage unit4and the reservoir unit90to each other is not limited to a resin, and various materials may be used.

The same applies to a material used for bonding the frame71and the reservoir base plate92to each other, that is, a material for forming the adhesive layer75,275. Thus, in a case where the adhesive layer75,275is formed by a material of lower viscosity, in S23of the first embodiment, a thickness of the adhesive layer75decreases due to weight of the reservoir base plate92and the upper reservoir91to bring the ink ejection face4ainto contact with the bottom face126a. In a case where the adhesive layer75,275is formed by a material of lower viscosity, in G23of the second embodiment, a thickness of the adhesive layer275decreases due to weight of the frame71to bring the lower faces of the both lengthwise ends of the frame71into contact with the upper face207a. Therefore, it is not necessary to perform a pressing after S23and G23.

As the material used for bonding the frame71and the reservoir base plate92to each other, that is, as the material for forming the adhesive layer75,275, various materials may be used.