JP6144452B2 - Ink jet recording apparatus and method of manufacturing ink jet head included in the same - Google Patents

Description

  The present invention relates to an inkjet recording apparatus and a method of manufacturing an inkjet head included in the inkjet recording apparatus.

  Patent Document 1 discloses an ink jet printer in which a sheet is transported along a flat transport surface below an ink jet head, and a plurality of nozzles are opened on the lower surface of the ink jet head facing the transport surface. In the ink jet printer described in Patent Document 1, the lower surface where the plurality of nozzles of the ink jet head are open is a plane parallel to the conveying surface, and the gap between the lower surface and the conveying surface is at any position in the surface direction. It is the same.

JP 2009-241459 A (FIG. 4)

  By the way, the gap between the opposed surface of the inkjet head that faces the conveying surface and the conveying surface is narrowed for reasons such as reducing the deviation of the ink landing position from the nozzle and improving the printing quality. . When the gap is narrow in this way, for example, when the recording medium absorbs a large amount of ink and is bent or bent and lifted from the conveyance surface and conveyed, the recording medium is opposed to the inkjet head. There is a risk of damaging the opening edge of the nozzle formed on the opposing surface. Also, if a liquid repellent film is formed to prevent ink from adhering to the opposite surface of the inkjet head, the recording medium may come into contact with the liquid repellent film and damage the liquid repellent film. There is also.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an ink jet recording apparatus in which an adjacent area of an ink ejecting area is brought close to an arrangement surface of the recording medium to prevent the recording medium from coming into contact with the ink ejecting area, and a method of manufacturing an ink jet head included therein Is to provide.

Ink jet recording apparatus of the present invention, a conveying means for conveying the ink jet head for ejecting ink onto a recording medium, the recording medium wherein the conveyance direction along the placement surface of the recording medium, the ink-jet head wherein the recording medium and is a relatively movable, the ink jet head, the surface facing open the arrangement surface and the gap has an ink ejection area in which a plurality of nozzles are opened, the plurality Nozzles form a nozzle row along the nozzle arrangement direction, a plurality of the nozzle rows are arranged in a direction intersecting the nozzle arrangement direction, and the ink ejection region is recessed in a direction away from the arrangement surface. Is curved in the transport direction.

The plurality of nozzle rows are preferably arranged in a direction intersecting the transport direction.
The plurality of nozzle rows are preferably formed on a single plate.
Furthermore, it is preferable that the ink ejection region is curved so as to approach the arrangement surface as it goes outward from the central portion.
According to this, when one nozzle having an ink ejecting area is focused, the area just outside of the nozzle is approaching the arrangement surface. Even if the recording medium comes into contact with the ink ejecting area, The area contacts and presses the recording medium prior to the nozzle, and the recording medium is prevented from further floating. Thereby, when the ink ejection area is flat, all the nozzles are contacted when the recording medium is brought into contact with the ink ejection area and conveyed, but the ink ejection area is curved, Even if the recording medium comes into contact with the ejection area, the number of nozzles that come into contact with the recording medium can be kept to a minimum.
In addition, the arrangement surface may be curved in a direction approaching the ink ejection region in the transport direction, and the curvature of the ink ejection region may be larger than the curvature of the arrangement surface.
Moreover, it is preferable that the difference between the longest distance and the shortest distance between the ink ejection region and the arrangement surface is 30 to 50 μm.

In addition, the prior SL ink ejection region, on both sides of a plurality of the nozzle rows along the nozzle arrangement direction, the convex portions along the nozzle array direction are formed respectively, the nozzle row and the convex portion Are preferably arranged side by side.

According to this, even if the recording medium comes into contact with the ink ejection area, the recording medium comes into contact with the tip of the convex portion that is closer to the arrangement surface than the nozzle in the ink ejection area. Contact with the row can be prevented.
Moreover, it is preferable that the said convex part protrudes toward the curvature center of the said ink ejection area | region.

  By making the adjacent area closer to the recording medium placement surface than the ink ejection area, it is possible to prevent the recording medium from contacting the ink ejection area. Even if the recording medium comes into contact with the adjacent area, the ink ejecting area and the adjacent area are formed of the same member, so that only the adjacent area portion of the member does not fall off. Further, as compared with the case of forming with another member, the assembly error does not occur, and it can be formed with high accuracy.

1 is a schematic plan view of an ink jet printer according to an embodiment. (A) is the perspective view which looked at the inkjet head from the lower part, (b) is the figure which looked at the inkjet head from the conveyance direction. (A) is the A section enlarged view of Drawing 2 (a), and (b) is a BB line sectional view of (a). (A) is the figure which looked at the inkjet head vicinity in case 1 from the scanning direction, (b) is the figure which looked at the inkjet head vicinity in case 2 from the scanning direction. It is the figure which looked at the inkjet head vicinity from the conveyance direction. It is a figure explaining the manufacturing process of a flow path unit. It is the perspective view which looked at the ink jet head in modification 1 from the lower part. It is the perspective view which looked at the ink jet head in modification 2 from the lower part. It is the figure which looked at the inkjet head vicinity in the modification 3 from the scanning direction. 10 is a side view of the vicinity of an inkjet head in Modification 4. FIG.

  Hereinafter, preferred embodiments of the present invention will be described. This embodiment is an example in which the present invention is applied to an inkjet printer that records desired characters or images on a recording sheet by ejecting ink from the inkjet head onto the recording sheet.

  First, a schematic configuration of the ink jet printer according to the present embodiment will be described. FIG. 1 is a schematic plan view of the ink jet printer according to the present embodiment. As shown in FIG. 1, an ink jet printer 1 (ink jet recording apparatus) includes a carriage 2 configured to reciprocate along a predetermined scanning direction (left and right direction in FIG. 1), and an ink jet mounted on the carriage 2. A head 3, a transport mechanism 4 that transports the recording paper P (recording medium) in a transport direction orthogonal to the scanning direction (from the top to the bottom in FIG. 1), and the recording paper P transported by the transport mechanism 4 are supported from the bottom surface. And a maintenance mechanism 5 for recovering the ink ejection performance of the inkjet head 3.

  The carriage 2 is supported by two guide shafts 6 and 7 extending in parallel with the scanning direction, and is configured to reciprocate in the scanning direction along the two guide shafts 6 and 7. An endless belt 9 is connected to the carriage 2, and when the endless belt 9 is driven by a motor (not shown), the carriage 2 moves in the scanning direction as the endless belt 9 travels. ing.

  An ink jet head 3 is mounted on the carriage 2. The ink-jet head 3 has a large number of nozzles 15 (see FIG. 2A) on the lower surface (the surface on the opposite side of the paper in FIG. 1). The inkjet head 3 is configured to eject ink supplied from an ink cartridge (not shown) from a large number of nozzles 15 onto a recording paper P that is conveyed downward (conveying direction) in FIG. ing.

  The transport mechanism 4 includes a paper feed roller 10 disposed upstream of the inkjet head 3 in the transport direction (upward in FIG. 1) and a paper discharge roller 11 disposed downstream of the inkjet head 3 in the transport direction. doing. The paper feed roller 10 and the paper discharge roller 11 are rotationally driven by a paper feed motor 12 and a paper discharge motor 13, respectively. The transport mechanism 4 supplies the recording paper P to the inkjet head 3 from above in FIG. 1 by the paper feed roller 10, and records the characters and images recorded by the inkjet head 3 by the paper discharge roller 11. The paper P is configured to be discharged downward in FIG.

  The platen 8 is disposed below the carriage 2 (in the depth direction in FIG. 1) between the paper feed roller 10 and the paper discharge roller 11 in the transport direction. The upper surface of the platen 8 facing the ink jet head 3 is a transport surface 8a (arrangement surface) on which the recording paper P is transported, and the recording paper P is supported by the transport surface 8a along the transport surface 8a. Are transported.

  Next, the inkjet head 3 will be described. FIG. 2A is a perspective view of the inkjet head as viewed from below, and FIG. 2B is a diagram of the inkjet head as viewed from the transport direction. Fig.3 (a) is the A section enlarged view of Fig.2 (a), (b) is the BB sectional drawing of (a). In FIG. 3A, illustration of the convex portion 30 formed on the head lower surface 16 to be described later is omitted. As shown in FIGS. 2A and 2B and FIGS. 3A and 3B, the inkjet head 3 includes a flow path unit 6 in which an ink flow path including a nozzle 15 and a pressure chamber 24 is formed; And a piezoelectric actuator 17 that applies pressure to the ink in the pressure chamber 24.

  First, the flow path unit 6 will be described. As shown in FIGS. 3A and 3B, the flow path unit 6 includes a cavity plate 20, a base plate 21, a manifold plate 22, a nozzle plate 23, a liquid repellent film 29, and a convex portion 30. The plates 20 to 23 are joined with a thermosetting adhesive in a laminated state. Among these, the cavity plate 20, the base plate 21, and the manifold plate 22 are each substantially rectangular plates in plan view made of a metal material (in this embodiment, stainless steel: SUS430). The nozzle plate 23 is a substantially rectangular plate that is the same as the three plates 20 to 22, and is formed of, for example, a polymer synthetic resin material (polyimide in the present embodiment), and is thermoset on the lower surface of the manifold plate 22. Bonded with adhesive.

  Since these three plates 20 to 22 are formed of a metal material, an ink flow path including relatively large holes such as a manifold 27 and a pressure chamber 24 described later can be easily formed by etching, for example. It is like that. Further, since the nozzle plate 23 is formed of a polymer synthetic resin material, it is easier to form a fine nozzle 15 described later by laser processing, for example, as compared with a case of a metal material.

  As shown in FIGS. 3A and 3B, among the four plates 20 to 23, the uppermost cavity plate 20 includes a plurality of pressure chambers 24 arranged along a plane. It is formed by a hole penetrating 20 in the thickness direction. The plurality of pressure chambers 24 are arranged in four rows in the transport direction (vertical direction in FIG. 2). Further, as shown in FIG. 3B, the plurality of pressure chambers 24 are respectively covered with a diaphragm 40 and a base plate 21 described later from above and below. Furthermore, each pressure chamber 24 is formed in a substantially elliptical shape that is long in the scanning direction (left-right direction in FIG. 3A) in plan view.

  Communication holes 25 and 26 are formed at positions where the base plate 21 overlaps both ends in the longitudinal direction of the pressure chamber 24 in plan view. The manifold plate 22 is formed with four manifolds 27 extending in the transport direction so as to overlap a portion of the pressure chamber 24 on the side of the communication hole 25 in plan view. These four manifolds 27 communicate with an ink supply port (not shown), and ink is supplied from an ink tank (not shown) to the manifold 27 via the ink supply port. Further, a plurality of communication holes 28 that are continuous with the plurality of communication holes 26 are formed at positions where the manifold plate 22 overlaps the ends of the plurality of pressure chambers 24 opposite to the manifolds 27 in plan view.

  Furthermore, a plurality of nozzles 15 are formed at positions where the nozzle plate 23 overlaps the plurality of communication holes 28 in plan view. As shown in FIG. 2 (a), the plurality of nozzles 15 constitutes four nozzle rows arranged in the transport direction and arranged in the scanning direction, and the plurality of pressure chambers 24 arranged in four rows, It arrange | positions so that it may overlap with the edge part on the opposite side to the manifold 27, respectively. From the nozzles 15 belonging to the four nozzle rows, inks of a total of four colors, black, yellow, cyan, and magenta, are ejected from the upstream side in the forward movement direction (main scanning direction) of the inkjet head 3, respectively. . Hereinafter, the lower surface of the nozzle plate 23 on which the plurality of nozzles 15 are formed is referred to as a head lower surface 16 that faces the transport surface 8a.

  The head lower surface 16 of the nozzle plate 23 is covered with a liquid repellent film 29. The liquid repellent film 29 is made of a material having higher liquid repellency than the nozzle plate 23 made of polyimide or the like (for example, a fluorine resin such as PTFE (polytetrafluoroethylene)). Therefore, even if a part of the ink ejected from the nozzle 15 adheres to the head lower surface 16, the ink is less likely to stay around the nozzle 15 due to the high liquid repellency of the liquid repellent film 29 and adheres to the head lower surface 16. It is possible to prevent the ink from adversely affecting the ink ejected from the nozzle 15 thereafter (such as occurrence of ejection bending).

  As shown in FIG. 3B, the manifold 27 communicates with the pressure chamber 24 through the communication hole 25, and the pressure chamber 24 communicates with the nozzle 15 through the communication holes 26 and 29. . As described above, a plurality of ink flow paths from the manifold 27 to the nozzles 15 through the pressure chambers 24 are formed in the flow path unit 6.

  A plurality of convex portions 30 projecting toward the transport surface 8 a are formed on the head lower surface 16 of the nozzle plate 23 covered with the liquid repellent film 29. The protruding direction of the convex portion 30 extends toward the direction directly below the nozzle plate 23. This is for forming the convex portion 30 after the nozzle plate 23 is bent in the inkjet head manufacturing method described later. However, if the convex portion 30 is formed before the nozzle plate 23 is bent, the convex portion 30 is It turns to the center of curvature. The plurality of convex portions 30 are made of, for example, a polymer synthetic resin material such as polyimide, extend in the transport direction, and are arranged in a plurality of rows (5 rows in the present embodiment) side by side in the scanning direction. The height of the convex portion 30 from the head lower surface 16 is the same in the transport direction. The plurality of convex portions 30 are alternately arranged with the nozzle rows in the scanning direction, and all the nozzle rows are configured such that both sides of the scanning direction are sandwiched by the convex portions 30.

2A and 2B, the head lower surface 16 of the nozzle plate 23 is curved so as to be recessed in a direction away from the transport surface 8a. That is, compared to the ink ejection region 16a in which the plurality of nozzles 15 at the center of the head lower surface 16 are formed, the adjacent region 16b that surrounds the entire circumference of the ink ejection region 16a of the head lower surface 16 and in which the nozzles 15 are not formed. The distance from the transport surface 8a is small.
Also in the ink ejection region 16a, the head lower surface 16 is curved so as to approach the transport surface 8a toward the adjacent region 16b outside the center portion in the scanning direction.

  Specifically, the distance X1 between the position (head lower surface 16 end) closest to the transport surface 8a of the head lower surface 16 (adjacent region 16b) and the transport surface 8a is about 1.5 mm. The position of the head lower surface 16 (adjacent region 16b) closest to the transport surface 8a (the end of the head lower surface 16) and the position of the head lower surface 16 (ink ejection region 16a) farthest from the transport surface 8a (the center of the head lower surface 16). The distance X2 is 0.02 to 0.5 mm. Further, the protruding length X3 of the convex portion 30 is 3.5 μm. That is, the tip of the convex portion 30 does not protrude toward the conveyance surface 8a side from the position (head lower surface 16 end portion) closest to the conveyance surface 8a of the head lower surface 16 (adjacent region 16b).

  In addition, since the curvature of curving the head lower surface 16 is very small (curving of about 30 to 50 μm with respect to the nozzle plate of 40 mm in the scanning direction and 50 mm in the transport direction), the ink landing position from the nozzle 15 to the recording paper P The deviation is very small and does not affect the print quality. If the deviation of the landing position is large, there is no problem if the ink ejection timing is appropriately controlled according to the deviation of the landing position.

  Next, the piezoelectric actuator 17 will be described. As shown in FIG. 3B, the piezoelectric actuator 17 includes a vibration plate 40 disposed on the upper surface of the flow path unit 6 (cavity plate 20) so as to cover the plurality of pressure chambers 24, and an upper surface of the vibration plate 40. In addition, a piezoelectric layer 41 disposed so as to face the plurality of pressure chambers 24 and a plurality of individual electrodes 42 disposed on the upper surface of the piezoelectric layer 41 are provided.

  The diaphragm 40 is a substantially rectangular metal plate in plan view, and is made of, for example, a ferromagnetic metal material such as ferritic stainless steel (SUS430). The vibration plate 40 is joined to the cavity plate 20 in a state of being disposed on the upper surface of the cavity plate 20 so as to cover the plurality of pressure chambers 24. In addition, the upper surface of the conductive diaphragm 40 is disposed on the lower surface side of the piezoelectric layer 41, thereby generating an electric field in the thickness direction in the piezoelectric layer 41 with the plurality of individual electrodes 42 on the upper surface. Also serves as an electrode. The diaphragm 40 as the common electrode is connected to the ground wiring of a head driver (not shown) that drives the piezoelectric actuator 17 and is always held at the ground potential.

  The piezoelectric layer 41 is made of a piezoelectric material mainly composed of lead zirconate titanate (PZT), which is a solid solution of lead titanate and lead zirconate and is a ferroelectric substance. The piezoelectric layer 41 is continuously formed across the plurality of pressure chambers 24 on the upper surface of the vibration plate 40. The piezoelectric layer 41 is polarized in the thickness direction at least in a region facing the pressure chamber 24.

  A plurality of individual electrodes 42 are respectively disposed in regions on the upper surface of the piezoelectric layer 41 facing the plurality of pressure chambers 24. Each individual electrode 42 has a substantially oval planar shape that is slightly smaller than the pressure chamber 24, and faces the central portion of the pressure chamber 24. Further, a plurality of contact portions 45 are drawn from the end portions of the plurality of individual electrodes 42 along the longitudinal direction of the individual electrodes 42. The plurality of contact portions 45 are electrically connected to a head driver (not shown) via a flexible printed wiring board (not shown). As a result, the head driver can selectively apply one of the two types of potentials of the predetermined drive potential and the ground potential to the plurality of individual electrodes 42.

  Next, the operation of the piezoelectric actuator 17 during ink ejection will be described. When a predetermined drive potential is applied to a certain individual electrode 42 from the head driver, between the individual electrode 42 to which this drive potential is applied and the diaphragm 40 as a common electrode held at the ground potential. A potential difference is generated, and an electric field in the thickness direction acts on the piezoelectric layer 41 sandwiched between the individual electrode 42 and the diaphragm 40. Since the direction of the electric field is parallel to the polarization direction of the piezoelectric layer 41, the piezoelectric layer 41 in the region (active region) facing the individual electrode 42 contracts in a plane direction perpendicular to the thickness direction. Here, since the lower vibration plate 40 of the piezoelectric layer 41 is fixed to the cavity plate 20, as the piezoelectric layer 41 positioned on the upper surface of the vibration plate 40 contracts in the surface direction, the vibration plate 40. The portion covering the pressure chamber 24 is deformed so as to protrude toward the pressure chamber 24 (unimorph deformation). At this time, since the volume in the pressure chamber 24 decreases, the ink pressure in the pressure chamber 24 rises, and ink is ejected from the nozzle 15 communicating with the pressure chamber 24.

  Returning to FIG. 1, the maintenance mechanism 5 is an area outside the area facing the recording paper P on the conveyance surface 8 a (the right side in FIG. 1) (hereinafter referred to as a maintenance area). A suction cap 31 that closely contacts the head lower surface 16 of the inkjet head 3, a suction pump 33 connected to the suction cap 31, a wiper 32 that wipes the head lower surface 16, and the like. ing.

  The suction cap 31 is formed of a flexible material such as rubber or synthetic resin, and can be moved up and down by a lifting mechanism (not shown), and is positioned at a retracted position separated from the head lower surface 16 of the inkjet head 3. To do. Then, the suction cap 31 is lifted from the retracted position by the elevating mechanism and stops when it moves to the capping position. The suction cap 31 in the capping position is in close contact with the head lower surface 16 and covers the plurality of nozzles 15 when the inkjet head 3 is in the maintenance area and faces the head lower surface 16.

  Then, when the suction pump 33 performs a suction operation with the suction cap 31 in close contact with the curvature of the head lower surface 16 of the inkjet head 3 and covering the nozzle 15, the suction cap 31 and the head lower surface 16 The air in the formed sealed space is sucked and the pressure is lowered, and the ink is discharged from the nozzle 15 to the suction cap 31. As a result, the ink in the nozzle 15 whose viscosity has increased (thickened) due to the evaporation of water, and the bubbles and dust mixed in the ink flow path in the inkjet head 3 are discharged from the nozzle 15 together with the ink. Thus, so-called suction purge for restoring ink ejection characteristics is possible.

  The wiper 32 is disposed adjacent to the suction cap 31 in the maintenance area, closer to the print area in the scanning direction than the suction cap 31. The wiper 32 is made of an elastic material such as rubber, and extends longer than the nozzle row in the transport direction, and the tip thereof faces upward.

  After the suction purge described above, when the suction cap 31 is separated from the head lower surface 16 of the inkjet head 3, a part of the ink discharged from the nozzle 15 is attached to the head lower surface 16. Therefore, after the wiper 32 is moved to a position protruding above the head lower surface 16 by a lifting mechanism (not shown), the inkjet head 3 is moved in the scanning direction together with the carriage 2 and attached to the head lower surface 16 by the wiper 32. The ink is wiped off. At this time, since the lower surface 16 of the head including the boundary between the adjacent region 16b and the ink ejecting region 16a is smoothly curved, the wiper 32 can be smoothly wiped without the wiper 32 being caught. The ink adhering to the ink 32 can be prevented from being scattered and the wear of the wiper 32 can be reduced.

  Here, for example, the recording paper P sometimes absorbs a large amount of ink ejected from the inkjet head 3 during recording, and is bent or bent, so that the recording paper P may float from the transport surface 8a to the inkjet head 3 side. . Further, the bent recording paper P may be transported by the transport mechanism 4. Further, the transport mechanism 4 may erroneously stack a plurality of recording papers P and transport the recording paper P in an end portion in the scanning direction. If the lower surface 16 of the head is recessed in a direction away from the conveying surface 8a and is not curved and is flat in parallel with the conveying surface 8a, the space between the recording paper P on the conveying surface 8a and the lower surface 16 of the head of the inkjet head 3 is between. Since the gap is small at the same distance at any position in the surface direction, the floating recording paper P contacts the head lower surface 16 and damages the nozzles 15 and the liquid repellent film 29 formed on the head lower surface 16. There is a fear.

  Therefore, in the present embodiment, the head lower surface 16 of the nozzle plate 23 is curved so as to be recessed in a direction away from the transport surface 8a. The distance between the ink ejection area 16a on the head lower surface 16 and the transport surface 8a in the adjacent area 16b adjacent to the ink lower area 16a on the head lower surface 16 is reduced.

  As a result, when the portion of the recording paper P that has floated to the head lower surface 16 side is transported toward the ink jet head 3, it is not the ink ejection region 16a but the adjacent region 16b that is disposed near the transport surface 8a. It is restrained from being lifted further by being pressed down by contact. Accordingly, it is possible to prevent the recording paper P from coming into contact with the ink ejection area 16a.

  More specific description will be given with reference to FIGS. 4 (a), 4 (b) and FIG. 4A is a diagram of the vicinity of the inkjet head in Case 1 as viewed from the scanning direction, and FIG. 4B is a diagram of the vicinity of the inkjet head in Case 2 as viewed from the scanning direction. FIG. 5 is a view of the vicinity of the inkjet head as viewed from the transport direction. First, a case where the recording paper P that has lifted from the transport surface 8a has been transported to the inkjet head 3 will be described (case 1). As an example, when the recording paper P is transported on the transport surface 8a, the leading edge of the recording paper P is in a free state until it is nipped by the paper discharge roller 11, and is likely to float.

  In this case, since the adjacent area 16b of the head lower surface 16 is disposed upstream of the ink ejection area 16a in the transport direction, the recording paper P that has floated is adjacent to the upstream area in the transport direction before the ink ejection area 16a. 16b is contacted. Then, the recording paper P is pressed against the adjacent area 16b, and is prevented from further floating. At this time, since the adjacent region 16b is closer to the transport surface 8a than the ink ejection region 16a, the recording paper P is lifted more than the distance between the adjacent region 16b and the transport surface 8a as shown in FIG. In a state where this is suppressed, the ink passes through the lower part of the ink ejection region 16a located farther from the transport surface 8a than the adjacent region 16b. Accordingly, it is possible to prevent the recording paper P from coming into contact with the ink ejection area 16a.

  Further, as shown in FIG. 4B, when the recording paper P bent larger than the width of the ink ejection region 16a in the transport direction is transported, two recording media P sandwiching the ink ejection region 16a in the transport direction. Since the adjacent area 16b is close to the transport surface 8a, it is possible to prevent the bent recording paper P from contacting the two adjacent areas 16b and coming into contact with the ink ejecting area 16a. Further, since the adjacent area 16b on the downstream side in the transport direction with respect to the ink ejection area 16a of the head lower surface 16 is disposed close to the transport surface 8a, for example, the rear end of the recording paper P is sandwiched from the paper feed roller 10. Even when ink is absorbed and floated by the recording operation in the released and free state, it can be prevented from coming into contact with the adjacent area 16b on the downstream side in the transport direction and coming into contact with the ink ejecting area 16a. it can.

  Further, since the serial type ink jet head 3 as described above reciprocates in the scanning direction together with the carriage 2, the recording sheet P on which the ink ejection area 16a on the lower surface 16 of the head is lifted is contacted from either side of the scanning direction. There is a risk. Therefore, as shown in FIG. 5, the adjacent areas 16b located on both sides in the scanning direction across the ink ejection area 16a are approaching the transport surface 8a, so that the recording that floats when the inkjet head 3 moves in the scanning direction. The paper P comes into contact with and is pressed against the adjacent area 16b adjacent to the ink ejection area 16a in the scanning direction. Therefore, it is possible to prevent the recording paper P from coming into contact with the ink ejection area 16a of the inkjet head 3 that moves in the scanning direction.

  As described above, in the present embodiment, the adjacent region 16b of the head lower surface 16 is disposed adjacent to the entire circumference surrounding the ink ejecting region 16a, so that the recording paper P contacts the ink ejecting region 16a. Can be prevented from the entire periphery.

  Further, in addition to the adjacent region 16b being closer to the transport surface 8a than the ink ejecting region 16a, the ink ejecting region 16a is curved so as to be recessed away from the transport surface 8a, and the ink ejecting region 16a is outside. It is approaching the conveyance surface 8a smoothly as it goes to. Therefore, even when the recording paper P is in contact with the ink ejection area 16a, the area immediately outside the nozzle 15 is close to the transport surface 8a when one nozzle 15 having the ink ejection area 16a is focused on. The outer area contacts and presses the recording paper P before the nozzle 15 to suppress the recording paper P from further floating. As a result, when the ink ejection area 16a is flat, when the recording paper P comes into contact with the ink ejection area 16a and is conveyed, it contacts all the nozzles 15, but the ink ejection area 16a is curved so as to be recessed. Therefore, even if the recording paper P contacts the ink ejection area 16a, the contact with the nozzle 15 can be kept to a minimum.

  Furthermore, since the convex portions 30 are formed on both sides of the nozzle row of the ink ejection area 16a, even if the recording paper P comes into contact with the ink ejection area 16a, the recording paper P in the ink ejection area 16a Since it contacts the tip of the convex part 30 which is closer to the transport surface 8a than the nozzle 15, it is possible to prevent the recording paper P from contacting the nozzle row.

  Even if the recording paper P comes into contact with the adjacent area 16b, the ink ejecting area 16a and the adjacent area 16b are formed integrally with the nozzle plate 23, so that only the portion of the adjacent area 16b is not dropped. Absent. Further, as compared with the case where the adjacent region 16b is formed on a member different from the nozzle plate 23, an assembly error does not occur, and the ink ejection region 16a and the adjacent region 16b can be formed with high accuracy.

  Next, a method for manufacturing the inkjet head 3 will be described. FIG. 6 is a diagram illustrating a manufacturing process of the flow path unit. First, among the four plates 20 to 23 constituting the flow path unit 6, ink such as the pressure chamber 24 and the manifold 27 is added to the three plates of the cavity plate 20 made of SUS430, the base plate 21, and the manifold plate 22. The holes constituting the flow path are formed by etching. A plurality of nozzles 15 are formed on the nozzle plate 23 made of polyimide by laser processing. Further, a liquid repellent film 29 is formed on the nozzle opening surface of the nozzle plate 23 by coating or the like.

  The thickness of the nozzle plate 23 is 0.05 mm, and the total thickness of the three plates 20 to 22 is 0.7 mm. And as shown to Fig.6 (a), it joins with the thermosetting adhesive in the state which laminated | stacked the four plates 20-23 mutually, and is more than the curing temperature of a thermosetting adhesive from both sides of a lamination direction (this implementation). It is heated and pressed at a heating temperature of about 150 degrees in the form for about 1 hour (heating and pressing step).

Thereafter, the stacked body of the four plates 20 to 23 is cooled to the environmental temperature in a free state where the pressing is released and not restrained (cooling step). The cooling may be natural cooling or any of forced air cooling in a constant temperature layer set to a temperature lower than the air blown by the fan or the environmental temperature. Then, since the linear expansion coefficient of polyimide is 3.6 × 10 ⁻⁵ and the linear expansion coefficient of SUS430 is 10 to 11 × 10 ⁻⁶ , as shown in FIG. Due to the temperature change, the nozzle plate 23 tends to contract more than the three plates 20 to 22, and the nozzle plate 23 is curved so as to be recessed toward the three plates 20 to 22. Thereby, the nozzle plate 23 can be easily curved so as to be recessed toward the three plates 20 to 22. In addition, it is possible to change the curved shape of the nozzle plate 23 suitably by changing the heating temperature in the heating press process mentioned above.

  Subsequently, as shown in FIG. 6C, convex portions 30 are respectively formed by coating or the like on both sides of the nozzle row on the surface of the nozzle plate 23 on which the liquid repellent film 29 is formed, thereby completing the flow path unit 6. Let And the inkjet actuator 3 and the flow path unit 6 which were produced with the conventionally well-known technique are laminated | stacked, and it joins by metal diffusion joining etc., and the inkjet head 3 is completed.

  Next, modified examples in which various changes are made to the present embodiment will be described. However, the same reference numerals are given to those having the same configuration as in the above embodiment, and the description thereof is omitted as appropriate.

  In the present embodiment, the adjacent region 16b located closer to the transport surface 8a than the ink ejecting region 16a is formed so as to surround the entire periphery of the ink ejecting region 16a, but moves relative to the ink jet head 3 as viewed. It suffices if the recording paper P is on the approaching side. For example, as shown in FIG. 7, the head lower surface 116 of the inkjet head 103 may be recessed and curved in the transport direction (Modification 1). At this time, both sides of the head lower surface 116 sandwiching the ink ejection region 116a in the transport direction are adjacent regions 116b that are closer to the transport surface 8a than the ink ejection region 116a. The adjacent region 116b may be disposed only on the upstream side in the transport direction, not on both sides in the transport direction. Such a modification is suitable, for example, a so-called line-type head that has a width equal to or larger than the width of the recording paper P and that transports the recording paper P to a fixed inkjet head. .

  As shown in FIG. 8, the head lower surface 216 of the inkjet head 203 may be concave and curved in the scanning direction (Modification 2). At this time, both sides of the head lower surface 216 sandwiching the ink ejection area 216a in the scanning direction are adjacent areas 216b that are closer to the transport surface 8a than the ink ejection area 216a. Note that when the first modification and the second modification are compared, the first modification in which the extending direction of the convex portion and the arrangement direction of two adjacent regions sandwiching the ink ejection region intersect each other in both directions. Can be protected from.

  Further, in the present embodiment, the entire head lower surface 16 of the inkjet head 3 is recessed and curved, but as shown in FIG. 9, the ink ejection region 316a is a flat surface, and the ink ejection region 316a has a flat surface. The adjacent region 316b may be bent toward the transport surface 8a and approach the transport surface 8a (Modification 3). In this case, it becomes easy to bend | fold by projecting the part which wants to bend of the several plate containing a nozzle plate compared with another plate. In the case of bending, the nozzle plate 23 is easier to hold the bent shape than the high-molecular synthetic resin material, which is the same metal as the three plates 20 to 22.

  Further, in the present embodiment, the recording paper P is linearly conveyed. However, as shown in FIG. 10, for example, the recording paper P is moved to a so-called drum-type head that is conveyed on the curved conveying surface 408. The present invention can also be applied (Modification 4). In this case, the bending rate of the head lower surface 416 of the ink jet head 403 is made larger than the bending rate of the conveying surface 408, so that the distance (X10) between the ink ejection region 416a where the plurality of nozzles 415 are opened and the conveying surface 408 is obtained. In addition, the distance (X11) between the conveyance area 408 and the adjacent area 416b adjacent to the ink ejection area 416a can be reduced.

  In the present embodiment, the head lower surface 16 of the inkjet head 3 is covered with the liquid repellent film 29, but the head lower surface 16 may not be covered with the liquid repellent film 29.

  Furthermore, in this embodiment, although the convex part 30 was formed in the head lower surface 16 of the inkjet head 3, the convex part does not need to be formed.

In the present embodiment, the flow path unit 6 and the piezoelectric actuator 17 are separately manufactured. However, only the piezoelectric actuator is prepared in advance, and the four plates 20 to 23 are heated and pressed as described above. In this case, the diaphragm 40 may be disposed on the upper surface of the cavity plate 20 and the piezoelectric actuator 17 may be joined together. in this case,
The linear expansion coefficient of PZT, which is the material of the piezoelectric layer 41, is 3-4 × 10 ⁻⁶ , and the linear expansion coefficient is the same as that of polyimide, which is the material of the nozzle plate 23, and SUS430, which is the material of the three plates 20-22. In comparison, polyimide>SUS430> PZT. Therefore, due to the temperature change from the heating temperature to the environmental temperature in the cooling process described above, the nozzle plate 23 contracts more than the three plates 20 to 22 and the three plates 20 to 22 become larger than the piezoelectric layer 41. In an attempt to shrink, the nozzle plate 23 is greatly curved so as to be recessed toward the three plates 20 to 22. Thereby, the nozzle plate 23 can be easily curved so as to be recessed toward the three plates 20 to 22.

  Furthermore, in this embodiment, by releasing the pressing state of the four plates 20 to 23 stacked at the time of the cooling step after the heating and pressing step, the difference in linear expansion coefficient between the four plates 20 to 23 is caused. Although the nozzle plate 23 is curved due to the difference in shrinkage rate, it may be bent mechanically. In this case, the bending height can be freely controlled by the press amount. Further, it can be bent or bent into an arbitrary shape. In the case of bending by pressing, as described above, the nozzle plate 23 is less likely to be broken when it is made of the same metal as the three plates 20 to 22 than the polymer synthetic resin material, and maintains a bent shape. It's easy to do. Further, the nozzle plate 23 may be formed by being curved by injection molding. In any case, as compared with the case where the ink ejection region 16a and the adjacent region 16b are formed as separate members, the ink ejection region 16a and the adjacent region 16b can be formed with high accuracy without causing an assembly error.

  In the present embodiment, the recording paper P is transported in the transport direction by the transport mechanism 4, but the ink jet head 3 not only moves in the scan direction, but also intersects the scan direction (transport direction). In addition, the ink jet head 3 may move relative to the recording paper P so that relative conveyance between the recording paper P and the ink jet head 3 is realized.

DESCRIPTION OF SYMBOLS 1 Inkjet printer 3 Inkjet head 4 Conveyance mechanism 8a Conveyance surface 15 Nozzle 16 Head lower surface 16a Ink ejection area 16b Adjacent area P Recording paper

Claims (6)

An inkjet head that ejects ink onto a recording medium;
Transport means for transporting the recording medium in a transport direction along the recording medium placement surface;
The inkjet head and the recording medium are relatively movable,
The ink jet head has an ink ejection region in which a plurality of nozzles are opened on a surface facing the arrangement surface with a gap therebetween,
The plurality of nozzles form a nozzle row along a nozzle arrangement direction, and a plurality of the nozzle rows are arranged in a direction intersecting the nozzle arrangement direction,
An ink jet recording apparatus, wherein the ink ejecting area is curved so as to approach the arrangement surface radially from a central portion thereof . The inkjet head is movable in a scanning direction parallel to the arrangement surface and intersecting the transport direction;
The inkjet recording apparatus according to claim 1, wherein the plurality of nozzle rows are arranged in the scanning direction. An inkjet head that ejects ink onto a recording medium;
Transport means for transporting the recording medium in a transport direction along the recording medium placement surface;
The inkjet head and the recording medium are relatively movable,
The ink jet head has an ink ejection region in which a plurality of nozzles are opened on a surface facing the arrangement surface with a gap therebetween,
The plurality of nozzles form a nozzle row along a nozzle arrangement direction, and a plurality of the nozzle rows are arranged in a direction intersecting the nozzle arrangement direction,
The ink ejection region is curved so as to be recessed in a direction away from the arrangement surface in the transport direction,
The arrangement surface is curved so as to protrude in a direction approaching the ink ejection region in the transport direction,
An ink jet recording apparatus , wherein a curvature of the ink ejection region is larger than a curvature of the arrangement surface . The inkjet recording apparatus according to claim 3, wherein the ink ejection area is curved along the transport direction that is the nozzle arrangement direction. An inkjet head that ejects ink onto a recording medium;
Transport means for transporting the recording medium in a transport direction along the recording medium placement surface;
The inkjet head and the recording medium are relatively movable,
The ink jet head has an ink ejection region in which a plurality of nozzles are opened on a surface facing the arrangement surface with a gap therebetween,
The plurality of nozzles form a nozzle row along a nozzle arrangement direction, and a plurality of the nozzle rows are arranged in a direction intersecting the nozzle arrangement direction,
In the ink ejection region, convex portions are formed along the nozzle arrangement direction on both sides of the plurality of nozzle rows along the nozzle arrangement direction, respectively.
The nozzle rows and the convex portions are arranged alternately,
The ink ejection area is curved in the direction in which the convex portions are arranged,
The inkjet recording apparatus , wherein the plurality of protrusions protrude in a direction perpendicular to the arrangement surface .   The difference between the longest distance and the shortest distance between the ink ejection region and the arrangement surface is 30 to 50 μm, according to any one of claims 1 to 5. Inkjet recording device.

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