JP2003311954A - Inkjet head and inkjet printer comprising it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress occurrence of crosstalk. <P>SOLUTION: A discrete electrode having a main electrode section 35a is formed on the piezoelectric sheet 41 in an actuator unit 21 farthest from the pressure chamber 10. Hooked grooves 61a and 61b are made on the opposite sides of the main electrode section 35a in correspondence with the region between the main electrode sections 35a of adjacent discrete electrodes. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet head for printing by ejecting ink onto a recording medium, and
The present invention relates to an inkjet printer having an inkjet head.

[0002]

2. Description of the Related Art In an ink jet printer, an ink jet head distributes ink supplied from an ink tank into a plurality of pressure chambers, and selectively applies pulsed pressure to each pressure chamber to eject ink from nozzles. To do. As one means for selectively applying pressure to the pressure chamber, an actuator unit in which a plurality of piezoelectric sheets made of piezoelectric ceramics are laminated may be used.

As an example of such an ink jet head, a plurality of continuous flat plate-like piezoelectric sheets are laminated over a plurality of pressure chambers, and at least one of the piezoelectric sheets is common to many pressure chambers and has a ground potential. There is known one having one actuator unit sandwiched by a held common electrode and a large number of individual electrodes, that is, drive electrodes arranged at positions corresponding to the respective pressure chambers (see Patent Document 1). The part of the piezoelectric sheet sandwiched between the drive electrode and the common electrode and polarized in the stacking direction is exposed to the outside in the polarization direction of the piezoelectric sheet when the drive electrodes on both sides of the sandwiched part are set to a potential different from that of the common electrode. When an electric field is applied, it expands and contracts in the stacking direction due to the so-called piezoelectric vertical effect. In this case, the portion of the piezoelectric sheet sandwiched between the individual electrode and the common electrode acts as an active layer that is deformed by the piezoelectric effect when an external electric field is applied. As a result, the volume in the pressure chamber fluctuates, and ink can be ejected toward the recording medium from the nozzle communicating with the pressure chamber.

[0004]

[Patent Document 1] Japanese Unexamined Patent Publication No. 4-341852

[0005]

In the ink jet head as described above, in recent years, as the pressure chambers are arranged at a high density in order to meet the demands for higher resolution of images and high-speed printing, a certain pressure chamber is formed. Due to the deformation of the corresponding active layer, even the piezoelectric sheets corresponding to the adjacent pressure chambers are deformed, and ink is ejected from the ink ejection port where ink should not be ejected originally, or the original ink ejection amount is So-called crosstalk, which increases or decreases over the amount, has become a problem. When such crosstalk occurs, the image quality of the printed image is deteriorated, and therefore suppression of crosstalk is a very important problem for improving the quality of the inkjet printer.

A main object of the present invention is to provide an ink jet head capable of suppressing the occurrence of crosstalk and an ink jet printer having the ink jet head.

[0007]

According to the present invention, a plurality of pressure chambers each having one end connected to a nozzle and the other end connected to an ink supply source are provided, and the plurality of pressure chambers are arranged adjacent to each other in a matrix. A flow path unit and an actuator unit fixed to one surface of the flow path unit for changing the volume of the pressure chamber are provided, and the actuator unit is continuously provided over a plurality of the pressure chambers. The piezoelectric sheet arranged, the common electrode arranged on one side of the piezoelectric sheet and kept at a constant potential, and the common electrode arranged on the other side of the piezoelectric sheet, and arranged at a position corresponding to each pressure chamber. Ink jet head including a plurality of individual electrodes and a recess formed in a region of the piezoelectric sheet corresponding to the pressure chambers, and an ink jet head including the same Ttopurinta is provided (claim 1).

According to this, since the concave portion is formed in the region corresponding to between the adjacent pressure chambers in the actuator unit, the crosstalk affecting the adjacent pressure chamber due to the deformation of the active layer due to the piezoelectric effect is suppressed. be able to.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram of an inkjet printer including an inkjet head according to a first embodiment of the present invention. Inkjet printer 10 shown in FIG.
1 is a color inkjet printer having four inkjet heads 1. In this printer 101, a paper feed unit 111 is provided on the left side of the drawing, and a paper discharge unit 11 is provided on the right side of the drawing.
2 are configured respectively.

Inside the printer 101, a paper transport path is formed for transporting paper from the paper feed section 111 to the paper discharge section 112. Immediately downstream of the paper feed unit 111,
A pair of feed rollers 105a and 105b for sandwiching and transporting a sheet as an image recording medium is arranged. The sheet is fed from the left side to the right side in the figure by the pair of feed rollers 105a and 105b. Two belt rollers 106 and 107 and an endless conveyor belt 108 wound so as to be stretched between the rollers 106 and 107 are arranged in the middle of the sheet conveying path. The outer peripheral surface of the conveyor belt 108, that is, the conveyor surface is treated with silicone, and while holding the paper conveyed by the pair of feed rollers 105a and 105b on the conveyor surface of the conveyor belt 108 by its adhesive force, The belt roller 106 is driven to rotate clockwise (in the direction of arrow 104) in the figure so that it can be conveyed toward the downstream side (right side).

Pressing members 109a and 109b are arranged at the insertion and ejection positions of the paper with respect to the belt roller 106, respectively. Holding members 109a, 109b
Is for pressing the paper onto the carrying surface of the carrying belt 108 so that the paper on the carrying belt 108 does not float from the carrying surface, and to firmly adhere the paper to the carrying surface.

A peeling mechanism 110 is provided immediately downstream of the transport belt 108 along the paper transport path. The peeling mechanism 110 peels the sheet adhered to the conveyance surface of the conveyance belt 108 from the conveyance surface, and the right sheet ejection unit 112.
It is configured to be sent to.

The four ink jet heads 1 have head bodies 1a at their lower ends. The head body 1a is
Each of them has a rectangular cross section, and they are arranged close to each other so that the longitudinal direction thereof is a direction perpendicular to the paper conveyance direction (direction perpendicular to the paper surface of FIG. 1). That is, the printer 101 is a line printer. The bottom surfaces of the four head main bodies 1a face the paper transport path, and the bottom surfaces are provided with nozzles having a large number of ink ejection openings each having a minute diameter. Magenta, yellow, cyan, and black inks are ejected from each of the four head bodies 1a.

The head body 1a is arranged so that a small gap is formed between the lower surface of the head body 1a and the conveying surface of the conveying belt 108, and a sheet conveying path is formed in this gap portion. With this configuration, when the paper conveyed on the conveyor belt 108 sequentially passes immediately below the four head main bodies 1a, ink of each color is ejected from the nozzles toward the upper surface of the paper, that is, the printing surface. A desired color image can be formed on a sheet.

The ink jet printer 101 has a maintenance unit 117 for automatically performing maintenance on the ink jet head 1. The maintenance unit 117 includes four head bodies 1
Four caps 116 for covering the lower surface of a and a purging mechanism not shown are provided.

The maintenance unit 117 is used when the ink jet printer 101 is printing.
It is located at a position (retracted position) immediately below the paper feeding unit 111. Then, when a predetermined condition is satisfied after the printing is completed (for example, when the printing operation is not performed for a predetermined time, or when the power of the printer 101 is turned off), the four head main bodies are used. 1a is moved to a position immediately below, and at this position (cap position), the cap 116 covers the lower surface of the head body 1a,
The ink of the nozzle portion of the head body 1a is prevented from drying.

The belt rollers 106 and 107 and the conveyor belt 108 are supported by the chassis 113. The chassis 113 has a cylindrical member 115 arranged below it.
It is placed on top. The cylindrical member 115 is rotatable about a shaft 114 attached at a position deviated from the center thereof. Therefore, when the height of the upper end of the cylindrical member 115 changes with the rotation of the shaft 114, the chassis 113 moves up and down accordingly. Maintenance unit 1
When moving 17 from the retracted position to the cap position,
The cylindrical member 115 is rotated in advance by an appropriate angle to make the chassis 1
13, transport belt 108 and belt rollers 106, 10
It is necessary to lower 7 from the position shown in FIG. 1 by an appropriate distance to secure a space for moving the maintenance unit 117.

In a region surrounded by the conveyor belt 108, a substantially rectangular parallelepiped shape (conveyance) which supports the inkjet head 1 from the inner peripheral side by contacting the position facing the ink jet head 1, that is, the lower surface of the conveyor belt 108 on the upper side (conveyance) The guide 121 having the same width as the belt 108)
Are arranged.

Next, the structure of the ink jet head 1 according to this embodiment will be described in more detail. Figure 2
FIG. 3 is a perspective view of the inkjet head 1. Figure 3
FIG. 3 is a sectional view taken along line III-III in FIG. 2. 2 and 3
As shown in FIG. 1, the inkjet head 1 according to the present embodiment has a head main body 1a having a rectangular planar shape extending in one direction (main scanning direction) and a base 131 for supporting the head main body 1a. ing. The base 131 includes a driver IC 132 and a substrate 133 that supply drive signals to the individual electrodes 35 (see FIG. 6) and the like in addition to the head body 1a.
I support you.

As shown in FIG. 2, the base 131 is partially bonded to the upper surface of the head main body 1a to support the head main body 1a, and is bonded to the upper surface of the base block 138. Base block 13
8 and a holder 139 for holding 8. The base block 138 is a substantially rectangular parallelepiped member having a length substantially the same as the length of the head body 1a in the lengthwise direction. Base block 138 made of metallic material such as stainless steel
Has a function as a lightweight structure that reinforces the holder 139. The holder 139 includes a holder main body 141 arranged on the head main body 1a side, and a pair of holder support portions 142 extending from the holder main body 141 to the side opposite to the head main body 1a. A pair of holder support parts 14
2 is a plate-shaped member, and is a holder body 14
They are provided in parallel with each other at a predetermined interval along the lengthwise direction of 1.

A pair of skirts 141a projecting downward are provided at both ends of the holder body 141 in the sub-scanning direction (direction orthogonal to the main scanning direction). Here, since the pair of skirts 141a are formed over the entire width in the longitudinal direction of the holder body 141, the pair of skirts 141a form a substantially rectangular parallelepiped groove 141b on the lower surface of the holder body 141. ing. The base block 138 is housed in the groove 141b. The upper surface of the base block 138 and the holder body 141
The bottom surface of the groove portion 141b is bonded with an adhesive. The thickness of the base block 138 is the holder body 14
Since it is slightly larger than the depth of the first groove portion 141b, the lower end portion of the base block 138 protrudes below the skirt portion 141a.

Inside the base block 138, an ink reservoir 3 which is a substantially rectangular parallelepiped void (hollow region) extending in the lengthwise direction is formed as a flow path of ink supplied to the head main body 1a. There is. Base block 138
On the lower surface 145 of the opening 3 b communicating with the ink reservoir 3.
(See FIG. 4) are formed. Ink pool 3
Is connected to a main ink tank (ink supply source) (not shown) in the printer body by a supply tube (not shown). Therefore, the ink reservoir 3 is appropriately replenished with ink from the main ink tank.

The lower surface 145 of the base block 138 projects below the periphery in the vicinity of the opening 3b. The base block 138 is fixed to the flow path unit 4 (see FIG. 3) of the head body 1a only in the portion 145a of the lower surface 145 near the opening 3b. Therefore, the region of the lower surface 145 of the base block 138 other than the portion 145a near the opening 3b is separated from the head body 1a, and the actuator unit 21 is arranged in this separated portion.

The driver IC 132 is fixed to the outer surface of the holder supporting portion 142 of the holder 139 via an elastic member 137 such as sponge. A heat sink 134 is closely arranged on the outer surface of the driver IC 132. The heat sink 134 is a member having a substantially rectangular parallelepiped shape and efficiently dissipates heat generated by the driver IC 132. The driver IC 132 includes a flexible printed wiring board (FPC: Flexible Printed Circuit) which is a power feeding member.
cuit) 136 is connected. The FPC 136 connected to the driver IC 132 is electrically joined to the substrate 133 and the head body 1a by soldering. A substrate 133 is arranged above the driver IC 132 and the heat sink 134 and outside the FPC 136. Between the upper surface of the heat sink 134 and the substrate 133, and between the lower surface of the heat sink 134 and the FPC 136.
And a seal member 149 are bonded to each other.

An FPC 136 is provided between the lower surface of the skirt portion 141a of the holder body 141 and the upper surface of the flow path unit 4.
The seal member 150 is arranged so as to sandwich the. That is, the FPC 136 includes the flow path unit 4 and the holder body 1.
It is fixed to 41 by a seal member 150. This prevents the head body 1a from bending when the head body 1a is elongated, and the actuator unit 21 and the FPC 136 are prevented.
It is possible to prevent stress from being applied to the connection portion with and to securely hold the FPC 136.

As shown in FIG. 2, in the vicinity of the lower corner of the inkjet head 1 in the main scanning direction, six convex portions 30a are evenly spaced along the side wall of the inkjet head 1. These protruding portions 30a are portions provided at both ends in the sub-scanning direction of the nozzle plate 30 (see FIG. 7) in the lowermost layer of the head body 1a. That is, the nozzle plate 30 is bent about 90 degrees along the boundary line between the protruding portion 30a and other portions.
The protruding portions 30a are provided at positions corresponding to the vicinity of both ends of sheets of various sizes used for printing in the printer 101. Since the bent portion of the nozzle plate 30 has a rounded shape rather than a right angle, the jam of the sheet that is caused when the leading edge of the sheet conveyed in the direction close to the head 1 comes into contact with the side surface of the head 1. That is, jamming is less likely to occur.

FIG. 4 is a schematic plan view of the head body 1a. In FIG. 4, the ink reservoir 3 formed in the base block 138 is virtually depicted by a broken line.
As shown in FIG. 4, the head body 1a has a rectangular planar shape extending in one direction (main scanning direction). The head main body 1a has a number of pressure chambers 10 to be described later and a flow path unit 4 in which an ink ejection port 8 at the tip of a nozzle (see also FIGS. 5, 6, and 7) is formed, and the upper surface thereof is provided. A plurality of trapezoidal actuator units 21 arranged in two rows in a zigzag pattern are bonded. Each actuator unit 21 is arranged such that its parallel facing sides (upper side and lower side) are along the longitudinal direction of the flow path unit 4. The hypotenuses of the adjacent actuator units 21 overlap each other in the width direction of the flow path unit 4.

The lower surface of the flow path unit 4 corresponding to the adhesion area of the actuator unit 21 is an ink ejection area. As will be described later, a large number of ink ejection openings 8 are arranged in a matrix on the surface of the ink ejection area. Further, in the base block 138 arranged above the flow path unit 4, the ink reservoir 3 is formed along the longitudinal direction thereof. The ink reservoir 3 communicates with an ink tank (not shown) through an opening 3a provided at one end thereof and is always filled with ink.
In the ink reservoir 3, two openings 3b are arranged in pairs along the extending direction, and the openings 3b are provided in a zigzag manner in a region where the actuator unit 21 is not provided.

FIG. 5 is an enlarged view of the area surrounded by the alternate long and short dash line drawn in FIG. As shown in FIGS. 4 and 5,
The ink reservoir 3 communicates with the manifold 5 in the flow channel unit 4 located below the ink reservoir 3 through the opening 3b. The opening 3b is provided with a filter (not shown) for capturing dust and the like contained in the ink. The front end of the manifold 5 is branched into two to form a sub-manifold 5a. One actuator unit 21
Two sub-manifolds 5a enter into the lower part of the actuator unit 21 from two openings 3b located on both sides of the inkjet head 1 in the longitudinal direction. That is, one actuator unit 2
A total of four sub-manifolds 5 a extend along the longitudinal direction of the inkjet head 1 in the lower part of the nozzle 1.
Each sub-manifold 5a is filled with the ink supplied from the ink reservoir 3.

FIG. 6 is an enlarged view of the area surrounded by the alternate long and short dash line drawn in FIG. As shown in FIGS. 5 and 6,
On the upper surface of the actuator unit 21, individual electrodes 35 each having a substantially rhombic plan shape are regularly arranged in a matrix. Further, a large number of ink ejection ports 8 are arranged in a matrix on the surface of the ink ejection region corresponding to the actuator unit 21 of the flow path unit 4. Inside the flow path unit 4, substantially rhombic pressure chambers (cavities) 10 each having a planar shape slightly larger than the individual electrode 35 and communicating with each ink ejection port 8 and apertures 12 are regularly arranged in a matrix. Are arranged in. The pressure chamber 10 is formed at a position corresponding to the individual electrode 35, and most of the individual electrode 35 in plan view is the pressure chamber 1.
It is included in 0. 5 and 6, in order to make the drawings easy to understand, the actuator unit 2
The pressure chamber 10, the aperture 12 and the like, which are to be drawn in broken lines inside 1 or in the flow path unit 4, are drawn in solid lines. Further, in FIGS. 5 and 6, a groove portion 61 described later is omitted.

FIG. 7 is a partial sectional view along the longitudinal direction of the pressure chamber of the head body 1a depicted in FIG. As can be seen from FIG. 7, each ink ejection port 8 is formed at the tip of a tapered nozzle. Each ink ejection port 8 communicates with the sub-manifold 5a via a pressure chamber 10 (length 900 μm, width 350 μm) and an aperture 12. In this manner, the ink jet head 1 is provided with the ink flow path 32 that extends from the ink tank to the ink reservoir 3, the manifold 5, the sub-manifold 5a, the aperture 12 and the pressure chamber 10 to reach the ink ejection port 8.

Further, as is clear from FIG. 7, the pressure chamber 1
0 and the aperture 12 are provided at different heights.
As a result, as shown in FIG. 6, in the flow path unit 4 corresponding to the ink ejection region below the actuator unit 21, the aperture 12 communicating with one pressure chamber 10 is connected to the pressure chamber adjacent to the pressure chamber 10. It can be arranged at the same position as 10 in a plan view. As a result, since the pressure chambers 10 are in close contact with each other and are arranged at high density, high-resolution image printing is realized by the inkjet head 1 having a relatively small occupied area.

The pressure chambers 10 are arranged in the planes shown in FIGS. 5 and 6 in the longitudinal direction of the ink jet head 1 (first arrangement direction) and in a direction slightly inclined from the width direction of the ink jet head 1 (second arrangement). Direction) in the ink ejection area. The first arrangement direction and the second arrangement direction form an angle θ slightly smaller than a right angle. Of these, the second arrangement direction corresponds to the direction along the lower left side or the upper right side of the pressure chamber 10 illustrated in FIG. 6. The ink ejection openings 8 are arranged at 50 dpi in the first arrangement direction. On the other hand, 12 pressure chambers 10 are arranged in the second arrangement direction so that 12 pressure chambers are included in the ink ejection region corresponding to one actuator unit 21. As a result, twelve ink ejection openings 8 are present in the entire width of the inkjet head 1 in a range separated by the distance between two ink ejection openings 8 adjacent in the first arrangement direction. It should be noted that at both ends (corresponding to the hypotenuse of the actuator unit 21) of each ink ejection area in the first arrangement direction, a complementary relationship with an ink ejection area corresponding to another actuator unit 21 facing in the width direction of the inkjet head 1 is provided. Therefore, the above condition is satisfied. Therefore, in the ink jet head 1 according to the present embodiment, ink is sequentially ejected from a large number of ink ejection openings 8 arranged in the first and second arrangement directions as the ink jet head 1 moves in the width direction relative to the paper. By ejecting droplets, printing can be performed at 600 dpi in the main scanning direction.

Next, the structure of the flow path unit 4 will be described in more detail with reference to FIG. FIG. 8 is a schematic diagram showing the positional relationship among the pressure chamber 10, the ink discharge port 8 and the aperture (restricted flow path) 12. As shown in FIG. 8, the pressure chambers 10 have a predetermined spacing of 50 dp in the first arrangement direction.
i are arranged in rows. The rows of such pressure chambers 10 are arranged in 12 rows in the second arrangement direction, and as a whole, the pressure chambers 10 are two-dimensionally arranged in the ink ejection region corresponding to one actuator unit 21.

There are two types of pressure chambers: a pressure chamber 10a in which the nozzle is connected to the upper acute angle portion in FIG. 8 and a pressure chamber 10b in which the nozzle is connected to the lower acute angle portion. The plurality of pressure chambers 10a and the plurality of pressure chambers 10b are both arranged in the first arrangement direction to form pressure chamber rows 11a and 11b, respectively. As shown in FIG. 8, in the ink ejection area corresponding to one actuator unit 21,
Two pressure chamber rows 11a are arranged in order from the lower side in FIG.
Two pressure chamber rows 11b are arranged adjacent to the upper side thereof. Such a combination of two pressure chamber rows 11a and two pressure chamber rows 11b makes up a set of four pressure chamber rows, and a set of pressure chamber rows forms an ink discharge corresponding to one actuator unit 21. Within the region, they are arranged three times from the bottom. The straight line connecting the upper acute corners of the pressure chambers in each pressure chamber row 11a, 11b intersects the lower oblique side of each pressure chamber in the pressure chamber row adjacent to the pressure chamber row from above.

As described above, the first pressure chamber row 11a and the second pressure chamber row 11 in which the positions of the nozzles connected to the pressure chambers 10 are different when viewed from the direction perpendicular to the paper surface of FIG.
By arranging b and 2 adjacent to each other, the pressure chambers 10 are regularly aligned as a whole. On the other hand, the nozzles are arranged collectively in the central region in a set of pressure chamber rows in which these four pressure chamber rows are one set.
As a result, as described above, when four pressure chamber rows are set as one set and the sets of pressure chamber rows are repeatedly arranged three times from the lower side, the boundary neighborhood region between the sets of pressure chamber rows, that is, Areas where nozzles do not exist are formed on both sides of the set of four pressure chamber rows. A wide sub-manifold 5a for supplying ink to each pressure chamber 10 is extended there. In the embodiment of the present invention, in the ink ejection area corresponding to one actuator unit 21, one is provided on the lower side in the drawing, between the lowest pressure chamber row set and the second pressure chamber row set. , A total of four sub-manifolds 5a having a wide width are provided in the first arrangement direction.

As shown in FIG. 8, the nozzles communicating with the ink ejection openings 8 for ejecting ink are 50d in the first arrangement direction, corresponding to the pressure chambers 10 regularly arranged in this direction.
They are arranged at equal intervals of pi. Further, unlike the case where the twelve pressure chambers 10 are regularly arranged in the second arrangement direction that intersects the first arrangement direction at the angle θ, the twelve pressure chambers corresponding to the twelve pressure chambers 10 are also arranged. As described above, the nozzles are connected to the upper acute-angled portion and the lower acute-angled portion of the pressure chamber 10, and are not regularly arranged in the second arrangement direction at regular intervals. .

On the other hand, when the nozzles are always in communication with the acute-angled portions on the same side of the pressure chamber 10, the nozzles are also regularly arranged in the second arrangement direction at regular intervals.
In other words, in this case, the nozzle is 1 from the lower side to the upper side in the figure.
Each time the row of pressure chambers rises, they are arranged so as to be displaced in the first arrangement direction by an interval corresponding to 600 dpi which is the resolution at the time of printing. On the other hand, in the present embodiment, a total of four pressure chamber rows, that is, two pressure chamber rows 11a and two pressure chamber rows 11b, is set as one set, and this is repeated three times from the lower side. Therefore, the displacement of the nozzle position in the first arrangement direction is not always the same every time one pressure chamber row goes up from the lower side to the upper side in the drawing.

In the ink jet head 1 according to the present embodiment, the strip-shaped region R having a width (about 508.0 μm) corresponding to 50 dpi in the first arrangement direction and extending in the direction orthogonal to the first arrangement direction. Think In this strip-shaped region R, only one nozzle exists in any of the 12 pressure chamber rows. That is, when such a strip region R is partitioned at an arbitrary position in the ink ejection region corresponding to one actuator unit 21, 12 nozzles are always distributed in this strip region R. The positions of the points obtained by projecting these 12 nozzles on a straight line extending in the first array direction are
They are separated by an interval corresponding to the resolution of 600 dpi at the time of printing.

These 12 nozzles are referred to as (1) to (12) in order from the position on the left where the 12 nozzles belonging to one strip region R are projected on a straight line extending in the first arrangement direction. These 12 nozzles are (1), (7), (2), (8), (5), (11), (6), (12),
They are arranged in the order of (9), (3), (10), and (4).

When the active layer in the actuator unit 21 of the ink jet head 1 according to this embodiment having the above-described structure is appropriately driven, 600 dpi is obtained.
It is possible to draw characters and figures having the resolution of. That is, specific characters and figures can be printed on the print medium by sequentially and selectively driving the active layers corresponding to the 12 rows of pressure chambers in accordance with the conveyance of the print medium.

For example, a case of printing a straight line extending in the first arrangement direction at a resolution of 600 dpi will be described. First, the case where the nozzle communicates with the acute angle portion on the same side of the pressure chamber 10 will be briefly described. In this case, in response to the conveyance of the print butterfly, ink is started to be ejected from the nozzles in the pressure chamber row located at the bottom in FIG. 8 and sequentially belongs to the pressure chamber row adjacent to the upper side. Select a nozzle to eject ink. As a result, ink dots are formed adjacent to each other at an interval of 600 dpi in the first arrangement direction. Finally, a straight line extending in the first array direction is drawn with a resolution of 600 dpi as a whole.

On the other hand, in the embodiment of the present invention, ink is started to be ejected from the nozzles in the pressure chamber row 11a located at the bottom in FIG. 8, and the pressure adjacent to the upper side is sequentially transferred as the print medium is conveyed. Ink is selected by selecting a nozzle that communicates with the chamber. At this time, since the displacement of the nozzle position in the first arrangement direction is not always the same every time one row of pressure chambers is moved upward from the lower side, the print medium is sequentially formed along the first arrangement direction as the print medium is conveyed. Ink dots are 600dp
The intervals of i are not equal.

That is, as shown in FIG. 8, in response to the conveyance of the print medium, first, ink is ejected from the nozzle (1) communicating with the pressure chamber row 11a at the bottom in the figure to print. A space corresponding to 50 dpi on the medium (approximately 508.0 μm
In m), a dot row is formed. After that, as the print medium is conveyed, the position where the straight line is formed is the second pressure chamber row 1 from the bottom.
When the position of the nozzle (7) communicating with 1a is reached, ink is ejected from this nozzle (7). As a result, 2 dots are formed at the position (about 42.3 μm × 6 = about 254.0 μm) displaced in the first arrangement direction by 6 times the interval (about 42.3 μm) corresponding to 600 dpi from the initially formed dot position. The th ink dot is formed.

Next, when the straight line formation position reaches the position of the nozzle (2) communicating with the third pressure chamber row 11b from the bottom as the print medium is conveyed, ink is ejected from the nozzle (2). It As a result, 6 dots from the initial dot position
A third ink dot is formed at a position displaced in the first arrangement direction by an interval (about 42.3 μm) corresponding to 00 dpi. Further, when the straight line formation position reaches the position of the nozzle (8) communicating with the fourth pressure chamber row 11b from the bottom as the print medium is conveyed, ink is ejected from the nozzle (8). As a result, the distance from the position of the first formed dot is 7 for the interval (about 42.3 μm) corresponding to 600 dpi.
A position displaced by a factor of 2 in the first array direction (approximately 42.3 μm ×
7 = about 296.3 μm), the fourth ink dot is formed. Further, as the print medium is conveyed, the nozzle in which the straight line forming position communicates with the fifth pressure chamber row 11a from the bottom.
When the position (5) is reached, ink is ejected from the nozzle (5). As a result, 60 dots from the dot position that was initially formed
A position (about 42.3 μm × 4 =) displaced in the first array direction by four times the distance corresponding to 0 dpi (about 42.3 μm)
A fifth ink dot is formed at about 169.3 μm).

In the same manner, ink dots are successively formed while sequentially selecting nozzles communicating with the pressure chambers 10 located from the lower side to the upper side in the drawing. At this time, when the nozzle number shown in FIG. 8 is N, (magnification n = N-1) ×
Ink dots are formed at positions displaced from the initially formed dot positions in the first arrangement direction by an amount corresponding to (an interval corresponding to 600 dpi). When 12 nozzles are finally selected, between the ink dots formed by the nozzle (1) in the lowermost pressure chamber row 11a in the figure at an interval (about 508.0 μm) corresponding to 50 dpi. Are connected by 12 dots formed at intervals (about 42.3 μm) corresponding to 600 dpi, for a total of 60
It is possible to draw a straight line extending in the first arrangement direction with a resolution of 0 dpi.

Next, the sectional structure of the ink jet head 1 according to this embodiment will be described. FIG. 9 is a partially exploded perspective view of the head main body 1a depicted in FIG. Figure 7
As shown in FIG. 9, the main part on the bottom side of the inkjet head 1 includes, from above, the actuator unit 21, the cavity plate 22, the base plate 23, the aperture plate 24, the supply plate 25, the manifold plates 26, 27, 28, and the cover. The plate 29 and the nozzle plate 30 have a laminated structure in which a total of 10 sheet materials are laminated. Of these, the flow path unit 4 is composed of nine plates excluding the actuator unit 21.

As will be described in detail later, in the actuator unit 21, four piezoelectric sheets 41 to 44 (see FIG. 11) are laminated and electrodes are arranged, so that only the uppermost layer of them is applied when an electric field is applied. A layer having a portion to be an active layer (hereinafter, simply referred to as "layer having an active layer") and the remaining three layers are inactive layers. The cavity plate 22 is a metal plate provided with a large number of substantially rhombic openings corresponding to the pressure chambers 10.
The base plate 23 is a metal plate in which, for one pressure chamber 10 of the cavity plate 22, a communication hole between the pressure chamber 10 and the aperture 12 and a communication hole from the pressure chamber 10 to the ink ejection port 8 are provided. The aperture plate 24 is a metal plate in which, for each pressure chamber 10 of the cavity plate 22, a communication hole from the pressure chamber 10 to the ink ejection port 8 is provided in addition to the aperture 12. The supply plate 25 is a metal plate in which a communication hole between the aperture 12 and the sub-manifold 5a and a communication hole from the pressure chamber 10 to the ink ejection port 8 are provided for each pressure chamber 10 of the cavity plate 22. Manifold plates 26, 27, 2
Reference numeral 8 denotes a metal plate in which, in addition to the sub-manifold 5a, one pressure chamber 10 of the cavity plate 22 is provided with a communication hole from the pressure chamber 10 to the ink ejection port 8. The cover plate 29 is a metal plate in which a communication hole from the pressure chamber 10 to the ink ejection port 8 is provided for each pressure chamber 10 of the cavity plate 22. The nozzle plate 30 is a metal plate in which each of the pressure chambers 10 of the cavity plate 22 is provided with a tapered ink ejection port 8 that functions as a nozzle.

These ten sheets 21 to 30 are shown in FIG.
The ink channels 32 are aligned with each other and stacked so that the ink flow paths 32 as shown in FIG. The ink flow path 32 is
First from the sub-manifold 5a, it extends upwards, horizontally in the aperture 12, then further upwards, again horizontally in the pressure chamber 10, and then diagonally downward in the direction away from the aperture 12 and then vertically. Heading downward to the ink ejection port 8.

Next, the detailed structure of the actuator unit 21 will be described. FIG. 10 is an enlarged plan view of the actuator unit 21. 11 is a partial cross-sectional view of the head body 1a shown in FIG. 4 taken along the line XI-XI in FIG.

As shown in FIG. 10, individual electrodes 35 having a thickness of about 1.1 μm are provided on the upper surface of the actuator unit 21 at positions substantially overlapping with the pressure chambers 10 in plan view. . The individual electrode 35 includes a substantially rhombus-shaped main electrode portion 35a and a substantially rhombus-shaped auxiliary electrode portion 35b formed continuously from one acute angle portion of the main electrode portion 35a and smaller than the main electrode portion 35a. The auxiliary electrode portion 35b is connected to the acute angle portion of the main electrode portion 35a, and this connecting portion has a constricted shape. The main electrode portion 35a is smaller than the pressure chamber 10 and has a shape similar to that of the pressure chamber 10. The main electrode portion 35a is arranged so as to fit in the pressure chamber 10 in a plan view. Further, the auxiliary electrode portion 35b is
In plan view, most of the area protrudes from the pressure chamber 10. A piezoelectric sheet 41, which will be described later, is exposed in a region other than the individual electrodes 35 on the upper surface of the actuator unit 21.

In the ink jet head 1 of the present embodiment, the portion of each individual electrode 35 excluding the vicinity of the acute angle portion of the main electrode portion 35a has a width of about 30 μm and a depth of 20 to 25 μm.
It is surrounded by a groove portion 61 of a degree. This groove 61
Is the groove portion 6 arranged on one side of the pressure chamber 10 in the first arrangement direction which is the longitudinal direction of the inkjet head 1.
1a and a groove portion 61b arranged on the other side. Each of the grooves 61a and 61b has a "dogleg" shape (V shape) slightly separated from the outer edge of the main electrode portion 35a, and is formed at substantially the same position as the inner wall of the pressure chamber 10 in a plan view. Here, the two groove portions 61a and 61b are pressed in a plan view from a position slightly apart from an acute-angled tip (acute-angled portion) of the main electrode portion 35a in the second arrangement direction slightly inclined from the width direction of the inkjet head 1. It extends along the inner wall of the chamber 10 and extends to the vicinity of the constricted portion where the main electrode portion 35a and the auxiliary electrode portion 35b are connected. Grooves 61a, 61b
Is a piezoelectric sheet 41 including an active layer, as shown in FIG.
Through, and the bottom portion thereof reaches a thickness position of about half of the piezoelectric sheet 42.

As shown in FIG. 11, the actuator unit 21 has four piezoelectric sheets 41, 42, 43, which are formed to have the same thickness of about 15 μm.
Includes 44. And the actuator unit 2
An FPC 136 for supplying a signal for controlling the potentials of the individual electrode 35 and the common electrode 34 is attached to 1. The FPC 136 is an auxiliary electrode portion 35b of the individual electrode 35.
It is fixed by soldering and is electrically connected. The piezoelectric sheets 41 to 44 are used for the inkjet head 1.
It is a continuous layered flat plate (continuous flat plate layer) so as to be arranged over a large number of pressure chambers 10 formed in one ink discharge region therein. By arranging the piezoelectric sheets 41 to 44 as a continuous flat plate layer over a large number of pressure chambers 10, it is possible to arrange the individual electrodes 35 at high density by using, for example, a screen printing technique.
Therefore, the pressure chambers 10 formed at the positions corresponding to the individual electrodes 35 can be arranged at high density, and high-resolution images can be printed. In the present embodiment, the piezoelectric sheets 41 to 44 are made of a lead zirconate titanate (PZT) -based ceramic material having ferroelectricity.

A common electrode 34 having a thickness of about 2 μm formed on the entire surface of the sheet is interposed between the uppermost piezoelectric sheet 41 and the piezoelectric sheet 42 adjacent below the sheet.
In addition, as described above, the upper surface of the actuator unit 21, that is, the upper surface of the piezoelectric sheet 41 has a planar shape similar to that of the pressure chamber 10 (length 850 μm, width 250 μm) and the projection area in the stacking direction is the pressure. An individual electrode 35 including a main electrode portion 35a included in the chamber area and a substantially rhombus-shaped auxiliary electrode portion 35b smaller than the main electrode portion 35a is formed for each pressure chamber 10. Furthermore, the piezoelectric sheet 4
3 and the piezoelectric sheet 44, and between the piezoelectric sheet 42 and the piezoelectric sheet 43.
Reinforcing metal films 36a and 36b are provided to reinforce. The reinforcing metal films 36a and 36b are formed on the entire surface of the sheet similarly to the common electrode 34 and have substantially the same thickness. In the present embodiment, the individual electrode 35 has Ni (a film thickness of about 1 μm) as a base and Au as a surface layer.
The common electrode 34 and the reinforcing metal film 36 are made of a laminated metal material having a film thickness of about 0.1 μm.
a and 36b are made of Ag—Pd based metal material. The reinforcing metal films 36a and 36b do not act as electrodes and need not necessarily be provided, but the presence of the reinforcing metal films 36a and 36b causes the piezoelectric sheet 4 after sintering.
The piezoelectric sheets 41 to 4 which can compensate for the brittleness of 1 to 44
4 has an advantage that it is easy to handle.

The common electrode 34 is grounded via the FPC 136 in a region (not shown). As a result, the common electrode 34 is kept at the ground potential equally in the regions corresponding to all the pressure chambers 10. In addition, the individual electrode 35 has a substantially rhombus-shaped auxiliary electrode portion 3 so that the potential of each of the individual electrodes 35 corresponding to each pressure chamber 10 can be controlled.
5b, the FPC 13 is independently provided for each individual electrode 35.
6 is in contact with a lead wire (not shown) provided in the wiring 6, and is connected to the driver IC 132 via this lead wire. As described above, in the present embodiment, the individual electrode 35 and the FPC 136 are connected to each other in the auxiliary electrode portion 35b outside the pressure chamber 10 in a plan view, which inhibits expansion and contraction of the actuator unit 21 in the stacking direction. The amount of volume change of the pressure chamber 10 can be increased. The common electrode 34 may be formed in a larger number for each pressure chamber 10 so that the projection region in the stacking direction includes the pressure chamber region, or the projection region may be formed in the pressure chamber region. As described above, a large number of smaller pressure chambers than the pressure chambers 10 may be formed for each pressure chamber 10, and it is not always necessary that the conductive sheet is formed on the entire surface of the sheet. However, at this time, it is necessary that the common electrodes are electrically connected so that all the portions corresponding to the pressure chamber 10 have the same potential.

In the ink jet head 1 according to this embodiment, the piezoelectric sheets 41 to 44 are polarized in the thickness direction. That is, in the actuator unit 21, the uppermost side (that is, the side farthest from the pressure chamber 10) of the piezoelectric sheet 41 is a layer in which an active layer that is deformed by the application of an external electric field is present and the lower side (that is, in the pressure chamber 10). Near side) It has a so-called unimorph type configuration in which the three piezoelectric sheets 42 to 44 are inactive layers that are deformed by the deformation of the active layers. Therefore, when the individual electrode 35 is set to a predetermined positive or negative potential with respect to the common electrode 34, for example, if the electric field and the polarization are in the same direction, the electric field application portion sandwiched between the electrodes in the piezoelectric sheets 41 to 43 is the active layer. It acts as a piezoelectric lateral effect and contracts in the direction perpendicular to the polarization direction. On the other hand, since the piezoelectric sheets 42 to 44 do not contract spontaneously because they are not affected by the electric field, the piezoelectric sheets 42 to 44 are arranged between the uppermost piezoelectric sheet 41 and the lower piezoelectric sheets 42 to 44 in a direction perpendicular to the polarization direction. Therefore, the piezoelectric sheets 41 to 44 are all deformed so as to be convex toward the inactive side (unimorph deformation). At this time, as shown in FIG. 11, since the lower surfaces of the piezoelectric sheets 41 to 44 are fixed to the upper surfaces of the partition walls (cavity plates) 22 that partition the pressure chambers, as a result, the piezoelectric sheets 41 to 44 move to the pressure chambers. Deform so that it is convex toward the side. Therefore, the volume of the pressure chamber 10 decreases, the pressure of the ink rises, and the ink is ejected from the ink ejection port 8. After that, when the individual electrode 35 is returned to the same potential as the common electrode 34, the piezoelectric sheets 41 to 44 return to the original shape and the volume of the pressure chamber 10 returns to the original volume, so that ink is sucked from the manifold 5 side.

As another driving method, the individual electrode 35 is previously set to a potential different from that of the common electrode 34, the individual electrode 35 is once set to the same potential as the common electrode 34 each time an ejection request is made, and then at a predetermined timing. And individual electrode 35 again
Can have a potential different from that of the common electrode 34. In this case, the piezoelectric sheets 41 to 44 return to their original shapes at the timing when the individual electrode 35 and the common electrode 34 have the same potential, so that the volume of the pressure chamber 10 is in the initial state (state where the potentials of both electrodes are different). ), The ink is sucked into the pressure chamber 10 from the manifold 5 side. After that, at a timing when the individual electrode 35 is again set to a potential different from that of the common electrode 34, the piezoelectric sheets 41 to 44 are deformed so as to be convex toward the pressure chamber 10, and the volume of the pressure chamber 10 is reduced, so that the pressure on the ink is increased. , Ink is ejected.

If the direction of the electric field applied to the piezoelectric sheets 41 to 44 and the polarization direction thereof are opposite, the piezoelectric lateral effect causes the activation in the piezoelectric sheet 41 sandwiched between the individual electrode 35 and the common electrode 34. The layer tries to extend in the direction perpendicular to the polarization direction. Therefore, the piezoelectric sheets 41 to 44 are arranged in the pressure chamber 10
It deforms so that it becomes concave to the side. Therefore, the volume of the pressure chamber 10 increases and ink is sucked from the manifold 5 side. After that, when the potential of the individual electrode 35 returns to its original value, the piezoelectric sheets 41 to 44 return to their original flat plate shape, and the volume of the pressure chamber 10 returns to the original volume, so that ink is ejected from the ink ejection port 8.

As described above, in the ink jet head 1 according to the present embodiment, the non-active layer side of the actuator unit 21 is fixed to the upper surface of the partition wall 22 partitioning the pressure chamber, and only the uppermost piezoelectric sheet 41 has the piezoelectric effect. It is configured to include an active layer that causes spontaneous displacement.
Since the uppermost piezoelectric sheet 41 that is not fixed includes the active layer, the displacement of the active layer due to the application of the external electric field is propagated to the adjacent region as it is. However, the groove portion 61 that reaches the piezoelectric sheet 42 is formed in a portion of each individual electrode 35 excluding the vicinity of the acute angle portion of the main electrode portion 35a.
a and 61b are formed, and these two groove portions 61a and 61b are formed.
b is the main electrode portion 35 in the second arrangement direction of the pressure chambers 10.
The pressure chamber 10 in plan view from a position slightly away from the acute angle portion of a.
Along the line, the main electrode portion 35a and the auxiliary electrode portion 335b are extended to the vicinity of the constricted portion. For this reason,
When looking around in the plane direction of the piezoelectric sheet 41 from the central portion of the main electrode portion 35a which causes a large displacement when a voltage is applied to the individual electrode 35, at least 1 is present in almost all the plane directions.
There will be one groove 61. Therefore, as compared with the case where the groove 61 is not formed, the pressure chamber 10
Even if the active layer in the portion corresponding to (1) is deformed, the deformation amount of the piezoelectric sheet 41 in the portion corresponding to another adjacent pressure chamber 10 is small. That is, it is possible to suppress the occurrence of so-called crosstalk in which ink is ejected from an ink ejection port where ink should not be originally ejected or the ink ejection amount increases or decreases from the original amount. Therefore, an image of good quality can be printed, the quality of the ink jet printer is improved, and the pressure chambers 10 can be arranged at a higher density to form an image of higher resolution. Is possible.

When the active layer is driven, the piezoelectric sheet 41 farthest from the fixed portion to the flow path unit 4 has a larger deformation amount than the other piezoelectric sheets 42, 43 and 44. Therefore, since the grooves 61a and 61b are formed on the upper surface of the piezoelectric sheet 41, that is, on the surface of the actuator unit 21 opposite to the surface facing the pressure chamber 10, the deformation transmitted to the adjacent pressure chamber 10 side and thereby the deformation. It is possible to effectively reduce the generated crosstalk. In addition, the grooves 61a and 61b are formed on the piezoelectric sheet 4
Since it is formed on the upper surface of No. 1, the manufacturing process is simple and easy to manufacture, and the grooves 61a and 61b can be formed with high positional accuracy.

In the ink jet head 1 of the present embodiment, the groove portions 61a and 61b which penetrate the common electrode 34 and reach the piezoelectric sheet 42 are not formed in an annular shape which completely surrounds the main electrode portion 35a. Therefore, the common electrode 34 in the corresponding portion in the main electrode portion 35a is not separated from the other portions, and the common electrode 34 is an integral continuous body. Therefore, the wiring to the common electrode 34 is easy.

The actuator unit 21 is a unimorph in which three piezoelectric sheets 42 to 44 as inactive layers are arranged between the piezoelectric sheet 41 farthest from the pressure chamber 10 including the active layer and the flow path unit 4. It has a structure.
Therefore, due to the piezoelectric lateral effect of the active layer, the pressure chamber 10
It is possible to increase the volume change of the pressure chamber 10 and to reduce the voltage applied to the individual electrode 35 as compared with an inkjet head in which the pressure chamber 10 side is a layer including an active layer and the opposite side is a non-active layer. Alternatively, the pressure chamber 10 can be highly integrated. By lowering the applied voltage,
The driver for driving the individual electrodes 35 can be downsized and the cost can be suppressed, and a sufficient amount of ink can be ejected even when the pressure chamber 10 is made small and highly integrated. As a result, downsizing of the head 1 and high-density arrangement of print dots are realized. Further, by making the layer including the active layer one layer, the volume change amount of the pressure chamber 10 can be made relatively large, and therefore, the driving voltage of the individual electrode 35 can be lowered and the pressure chamber 10 can be downsized. It was confirmed by the present inventor that high integration can be achieved.

Further, in the ink jet head 1 of the present embodiment, the piezoelectric sheet 41 farthest from the pressure chamber 10 is constituted so as to be a layer including the active layer, so that the deformation of the active layer is restricted. The layer will not be on the active layer. As a result, the volume change amount of the pressure chamber 10 due to the piezoelectric lateral effect of the active layer can be made larger than in the case where the piezoelectric sheet farthest from the pressure chamber 10 is the inactive layer. In addition, the groove portions 61a, 6 are formed adjacent to the active layer.
By forming 1b, a remarkable effect of suppressing crosstalk can be obtained.

The ink jet head 1 has the piezoelectric sheet 41 farthest from the pressure chamber of the actuator unit 21.
Only the layer including the active layer is formed, and the individual electrode 35 is formed only on the surface (upper surface) opposite to the surface on the pressure chamber side. Therefore, the actuator unit 2
It is not necessary to form a through hole for electrically connecting to the individual electrodes provided inside the actuator 21 so as to overlap each other in plan view, and thus it can be easily manufactured.

In the ink jet head 1, the piezoelectric sheet 41 having an active layer and the piezoelectric sheets 42 which are inactive layers are used.
Since 44 and 44 are formed of the same material, there is no need to replace the material, and it is possible to manufacture by a relatively simple manufacturing process. Therefore, it is expected that the manufacturing cost can be reduced. Furthermore, since the piezoelectric sheet 41 including the active layer and the piezoelectric sheets 42 to 44 that are inactive layers all have substantially the same thickness, the cost can be reduced by simplifying the manufacturing process. . This is because it becomes possible to easily perform the thickness adjusting step when coating and laminating the ceramic material to be the piezoelectric sheet.

As described above, the common electrode 34 and the individual electrode 3
The portion of the piezoelectric sheet 41 sandwiched between 5 and
When a voltage is applied between 35, it deforms due to the piezoelectric effect. For example, the piezoelectric sheet 41 contracts in the surface direction when it extends in the thickness direction when a voltage is applied. At this time, another piezoelectric sheet 42, between the piezoelectric sheet 41 and the pressure chamber 10,
Since 43 and 44 exist as inactive layers, the active layer portion of the actuator unit 21 is deformed so as to be convex toward the pressure chamber 10 as a whole. The amount of displacement of the actuator unit 21 at this time differs depending on the location depending on the relative position to the pressure chamber 10. That is, the displacement amount of the actuator unit 21 whose displacement is regulated by the partition walls 22 is the largest in the central portion of the pressure chambers 10 having the wide widths between the partition walls 22 and near the acute angle portion of the pressure chambers 10 having the narrow width between the partition walls 22. Is the smallest.

Here, in the region near the central portion of the pressure chamber 10 where the displacement amount in the thickness direction is large, the displacement obtained by combining the displacement in the surface direction and the displacement in the thickness direction of the active layer formed on the piezoelectric sheet 41. Propagates around. If another pressure chamber 10 is disposed adjacent to the center of the pressure chamber 10, the propagated displacement causes crosstalk with the other pressure chamber 10 and adversely affects ink ejection. In the present embodiment, as described above, the portion of the individual electrode 35 excluding the vicinity of the acute angle portion of the main electrode portion 35a is surrounded by the groove portion 61 that reaches the thickness position of about half the piezoelectric sheet 42. This effectively prevents the propagation of unnecessary displacement in the region near the center of the pressure chamber 10.

On the other hand, in the vicinity of the acute angle portion of the pressure chamber 10, even if a voltage is applied between the electrodes 34 and 35 to cause displacement in the plane direction, the displacement amount in the thickness direction is very small or almost nonexistent. Moreover, since the actuator unit 21 is fixed to the partition wall 22 of the flow path unit 4, the displacement of the active layer in the plane direction does not easily propagate. Therefore, although the displacement in the surface direction is slightly propagated to another pressure chamber 10 adjacent to the acute angle portion of the pressure chamber 10, the propagated displacement hardly causes adverse effects on ink ejection due to crosstalk. Therefore, as shown in FIG. 10, the groove 61 is not formed in the vicinity of the acute angle portion of the pressure chamber 10. further,
By not providing the groove 61 in the vicinity of the acute angle portion of the pressure chamber 10, the continuity of the common electrode 34 formed so as to sandwich the piezoelectric sheet 41 is also ensured.

Next, a method of manufacturing the ink jet head 1 according to this embodiment will be described with reference to FIG.

To manufacture the ink jet head 1,
First, the flow path unit 4 and the actuator unit 21 are separately manufactured in parallel, and then both are bonded. In order to manufacture the flow path unit 4, etching is performed on each of the plates 22 to 30 constituting the flow path unit 4 by using the patterned photoresist as a mask, and then, as shown in FIGS.
An opening and a recess as shown in (3) are formed in each of the plates 22 to 30. After that, the nine plates 22 to 30 are superposed on each other with an adhesive interposed and bonded so that the ink flow path 32 is formed, and thus the flow path unit 4 is manufactured.

On the other hand, in order to manufacture the actuator unit 21, first, a conductive paste serving as the reinforcing metal film 36a is pattern-printed on the green sheet of the ceramic material serving as the piezoelectric sheet 44. In parallel with that,
A conductive paste serving as the reinforcing metal film 36b is pattern-printed on a ceramic green sheet serving as the piezoelectric sheet 43, and a conductive paste serving as the common electrode 34 is formed on the ceramic green sheet serving as the piezoelectric sheet 42. Pattern print. Then, the laminate obtained by stacking the four green sheets to be the piezoelectric sheets 41 to 44 while aligning them using a jig is fired at a predetermined temperature. Then, the individual electrodes 35 are formed on the fired laminated piezoelectric sheet 41. The individual electrodes 35 are formed on the piezoelectric sheet 41 by, for example, plating a conductive film on the entire surface of the piezoelectric sheet 41 and removing unnecessary portions by laser patterning, or using a mask having an opening at a portion corresponding to the individual electrodes 35. Conductive film on PV
It may be formed by vapor deposition by D (Physical Vapor Deposition) or the like. The production of the actuator unit 21 is completed by the steps up to here.

If the above-mentioned evaporation at the time of firing is taken into consideration, the individual electrodes 35 made of a metal paste may be pattern-printed after firing the piezoelectric sheets 41 to 44, and the individual electrodes 35 may be further fired. In this case, the piezoelectric sheet 4
Since the piezoelectric sheets 41 to 44 have already been sufficiently shrunk during firing of 1 to 44, there is almost no dimensional change of the piezoelectric sheets 41 to 44 due to shrinkage during firing of the individual electrodes. Therefore, the individual electrodes 35 can be accurately aligned with the corresponding pressure chambers 10 as in the case of forming them by using the plating method or the vapor deposition method.

Further, as described above, the reinforcing metal film 3
By providing 6a and 36b, the brittleness of the piezoelectric sheets 41 to 44 can be compensated and the handling property of the piezoelectric sheets 41 to 44 can be improved, but the reinforcing metal film 36 is not necessarily required.
It is not necessary to provide a and 36b. For example, if the size of the actuator unit 21 is about 1 inch, the handling property of the piezoelectric sheets 41 to 44 will not be impaired due to brittleness without providing the reinforcing metal films 36a and 36b.

Furthermore, in the present embodiment, as described above, the individual electrodes 35 are formed only on the piezoelectric sheet 41. On the other hand, piezoelectric sheets 42 to 44 other than the piezoelectric sheet 41
When the individual electrodes are formed on the upper side, it is necessary to print the individual electrodes on the desired piezoelectric sheets 41 to 44 before stacking and firing the piezoelectric sheets 41 to 44. Therefore, due to the contraction of the piezoelectric sheets 41 to 44 that occurs during firing, a difference occurs in the positional accuracy of the individual electrodes on the piezoelectric sheets 42 to 44 and the positional accuracy of the individual electrodes 35 on the piezoelectric sheet 41. However, in the present embodiment, since the individual electrode 35 is formed only on the piezoelectric sheet 41, such a positional accuracy difference does not occur, and the individual electrode 35 is accurately positioned with respect to the corresponding pressure chamber 10. Will be aligned.

Next, the actuator unit 21 manufactured as described above is bonded to the flow path unit 4 with an adhesive so that the piezoelectric sheet 44 and the cavity plate 22 are in contact with each other. At this time, the both are bonded on the basis of the alignment marks formed on the surface of the cavity plate 22 of the flow path unit 4 and the surface of the piezoelectric sheet 41, respectively.

Next, as shown in FIG. 12, the individual electrode 35
Laser processing is performed using, for example, a YAG laser while controlling the emission direction so that the outer edge of the pressure chamber 10 is irradiated with the laser beam in plan view with reference to each of the main electrode portions 35a. By this laser processing, the piezoelectric sheet 42
"V-shaped" groove 61 reaching up to the middle of
a and 61b are formed on both sides of each main electrode portion 35a.

After that, the FPC 136 for supplying an electric signal to the individual electrode 35 is electrically joined to the actuator unit 21 by soldering, and the manufacturing of the ink jet head 1 is completed through a predetermined process.

In the manufacturing method described above, the piezoelectric sheet 4 is used.
When laminating 1 to 44, the individual electrodes are not formed between the adjacent piezoelectric sheets, that is, the active layers are included only in the piezoelectric sheet 41 farthest from the pressure chamber 10, so that they overlap in a plan view. Through holes for connecting the individual electrodes provided to each other to the piezoelectric sheets 41 to 4 are formed.
4 need not be formed. Therefore, as mentioned above,
The inkjet head 1 according to the present embodiment can be manufactured at a low cost by a relatively simple process.

In the manufacturing method described above, the individual electrode 3
5, only the common electrode 34 and the reinforcing metal films 36a and 36b
Unlike the above, the ceramic sheets 41 to 44 are not fired together with the ceramic material. This is because the individual electrodes 35 are exposed, so that they are easily evaporated by high temperature heating during firing,
This is because it is more difficult to control the thickness than the common electrode 34 covered with the ceramic material. However, since the common electrode 34 and the like also decrease in thickness to some extent during firing, it is difficult to reduce the thickness in consideration of maintaining continuity after firing. On the other hand, the individual electrode 35 can be formed thinner than the common electrode 34 and the like because it is formed by the method described above after firing. As described above, in the inkjet head 1 of the present embodiment, the displacement of the piezoelectric sheet 41, which is the active layer, is hard to be regulated by the individual electrode 35 by making the individual electrode 35 in the uppermost layer thinner than the common electrode 34. Thus, the volumetric deformation amount of the pressure chamber 10 in the inkjet head 1 is improved.

In the present embodiment, the groove portions 61a, 61
Although b is formed so as to reach the second piezoelectric sheet 42 from the top, the groove is formed so as to be contained only in the uppermost piezoelectric sheet 41, that is, so as not to reach the second piezoelectric sheet 42 from the top. It may have been done. Alternatively, the groove may be formed so as to reach the third or fourth piezoelectric sheet 43, 44 from the top. When the groove portion is formed so as to reach the second or lower piezoelectric sheet from the top, the groove portion is not formed in an annular shape so that the common electrode 34 is not divided into a plurality, and at least a part is connected to another region. Is preferred. However, if a wiring is provided for each common electrode, the common electrode may be divided into a plurality of portions for the groove portion.

In the present embodiment, the elongated groove portions 61a and 61b are formed as the concave portions, but the concave portions do not have to be elongated grooves, and for example, concave portions having a circular planar shape are provided between the adjacent pressure chambers 10. You may make it form one or more in the said area | region. However, the elongated groove portion is preferable because the effect of suppressing crosstalk can be further enhanced.

In the present embodiment, the elongated grooves 61a and 61b corresponding to the outer edges of the pressure chambers 10 are formed as the recesses in plan view. However, two or more such elongated grooves are arranged in parallel for each outer edge of the pressure chambers. May be provided. Further, the width of the groove portion can be arbitrarily changed within a range that does not hinder the operation of the piezoelectric sheet.

In this embodiment, the groove portions 61a and 61b are formed by laser processing. However, the groove portions can be formed by various methods such as etching using a patterned photoresist as a mask, other than laser processing. Is.

Further, the concave portion is the actuator unit 21.
It may be formed before bonding the flow path unit 4 and
It may be formed after bonding as described above. Further, when forming the individual electrode 35 on the uppermost piezoelectric sheet 41, the conductive film is removed by laser processing after forming the conductive film on the entire surface of the piezoelectric sheet 41. , The piezoelectric sheet 4 along with the removal of the conductive film
It is also possible to form a concave portion in 1.

Further, in the above-described embodiment, the pressure chamber 10
Although the active layer is formed only on the uppermost piezoelectric sheet 41 farthest from the uppermost layer, the uppermost piezoelectric sheet 41 does not necessarily include the active layer, and in addition to the uppermost piezoelectric sheet 41, The active layer may be formed on any other piezoelectric sheet. Even in these cases, a sufficient crosstalk suppressing effect can be obtained. Further, the inkjet head of the above-mentioned embodiment has a unimorph structure utilizing the piezoelectric lateral effect, but unlike this,
The present invention can also be applied to an inkjet head that utilizes the piezoelectric vertical effect in which the active layer is arranged closer to the pressure chamber than the inactive layer. Further, in the above-described embodiment, the inactive layers are all piezoelectric sheets, but an insulating sheet other than the piezoelectric sheet may be used as the inactive layer.

Next, ink jet heads according to second to sixth embodiments of the present invention will be described. The inkjet heads according to these embodiments differ from the first embodiment only in the position and shape of the groove formed in the actuator unit. Therefore, in the drawings according to these embodiments, the same members as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 13 is an enlarged plan view of an actuator unit in an ink jet head according to the second embodiment of the present invention. FIG. 14 shows XIV-XI of FIG.
It is sectional drawing which followed the V line.

As shown in FIG. 13, in the ink jet head of this embodiment, the actuator unit 2
Between the two individual electrodes 35 adjacent to each other on the upper surface of 1'in the first arrangement direction, a longer diagonal line of the main electrode portion 35a is provided corresponding to a portion excluding the vicinity of the acute angle portion of the main electrode portion 35a. A groove portion 61c having a substantially linear shape is provided in parallel with. As shown in FIG. 14, the groove portion 61 c penetrates the actuator unit 21 ′, and the bottom portion thereof reaches the upper surface of the cavity plate 22.

In the actuator unit 21 'having such a form, the reinforcing metal film 36b is formed on each piezoelectric sheet constituting the actuator unit 21' as described above.
It is obtained by pattern-printing conductive pastes that will become the common electrodes 34, overlapping them, firing at a predetermined temperature, and forming individual electrodes 35 on the piezoelectric sheet 41 in the fired laminate. The linear through hole to be the groove 61c is formed by fixing the actuator unit 21 'to the flow path unit 4 with an adhesive and then performing laser processing while adjusting the output of the YAG laser, the number of irradiations, and the emission direction. It Then, as shown in FIG.
The FPC 136 for supplying an electric signal to the actuator is attached onto the actuator unit 21 ', and the manufacturing of the inkjet head 1 is completed.

In the form of the groove portion 61c described above, since the groove portion 61c is formed as a through hole reaching from the surface of the actuator unit 21 'to the opposite surface thereof,
There is no ceramic material itself that propagates the displacement of the active layer generated by applying a voltage between the individual electrode 35 and the common electrode 343 to the adjacent pressure chamber side. This makes it possible to more effectively suppress the propagation of displacement to the adjacent pressure chamber side, that is, crosstalk.
Further, as shown in FIG. 14, the groove portion 61c which is a through hole.
Corresponds to the portion between the adjacent pressure chambers of the flow path unit 4, leaving a sufficient thickness to securely bond and fix the actuator unit 21 '.
Since it is formed in 1 ', the mechanical rigidity as the piezoelectric element can be kept high, and the responsiveness of the ink ejection performance in the inkjet head 1 can be improved.

The groove 61c may be filled with silicone rubber 71 in order to prevent corrosion of the electrode exposed in the groove 61c. The silicon rubber 71 is a material that is less likely to propagate deformation than the piezoelectric sheets 41 to 44.

Since the groove portion 61c penetrates the actuator unit 21 'in this manner, the pressure chamber 1
It is possible to extremely effectively reduce the deformation transmitted to the adjacent pressure chamber 10 side when driving the active layer corresponding to 0 and the crosstalk caused thereby.

The groove portion penetrating the actuator unit as described above may be employed not only in the present embodiment but also in the above-mentioned first embodiment and third to fifth embodiments described later. Is possible. Further, in the present embodiment, the groove portion 61c may not penetrate the actuator unit 21 '. In this case, since only one groove is formed between the adjacent individual electrodes 35, the manufacturing process is simplified as compared with the first embodiment.

Next, an ink jet head according to a third embodiment of the present invention will be described. FIG. 15 is an enlarged plan view of the actuator unit in the inkjet head according to the present embodiment.

As shown in FIG. 14, in the ink jet head of the present embodiment, the upper surface of the actuator unit is slightly separated from the lower right side of the main electrode portion 35a of each individual electrode 35, and the pressure in the plan view is small. From almost the same position as the inner wall of the chamber 10 (excluding the vicinity of the acute angle portion of the main electrode portion 35a),
It is slightly separated from the upper left side of the main electrode portion 35a of the individual electrode 35 adjacent to the individual electrode 35 on the right side in the first arrangement direction, and is substantially at the same position as the inner wall of the pressure chamber 10 in plan view (the main electrode portion 35a. (Excluding the vicinity of the acute angle portion) is provided with a substantially linear groove portion 61d. The groove portion 61d penetrates the piezoelectric sheet 41, and the bottom portion thereof has the piezoelectric sheet 42.
Has reached the middle of. Also in this embodiment, since the groove portion 61d is provided, when the active layer corresponding to a certain pressure chamber 10 is driven, it is transmitted to the adjacent pressure chamber 10 side, as in the first embodiment. It is possible to reduce deformation and the resulting crosstalk.

Next explained is an ink jet head according to the fourth embodiment of the invention. FIG. 16 is an enlarged plan view of the actuator unit in the inkjet head according to the present embodiment.

As shown in FIG. 16, in the ink jet head of this embodiment, the upper surface of the actuator unit is slightly separated from the upper left side of the main electrode portion 35a of each individual electrode 35, and the pressure chamber is seen in a plan view. A groove 61e having a substantially linear shape is provided at substantially the same position as the inner wall of 10 (excluding the vicinity of the acute angle portion of the main electrode portion 35a), and is slightly separated from the lower right side of the main electrode portion 35a of each individual electrode 35. In a plan view, substantially linear groove portions 61f are provided at substantially the same position as the inner wall of the pressure chamber 10 (except in the vicinity of the acute angle portion of the main electrode portion 35a).
Is provided. The groove portions 61e and 61f penetrate the piezoelectric sheet 41, and the bottom portion thereof reaches the middle of the piezoelectric sheet 42.

The lower end portion of the groove portion 61e has a main electrode portion 35a.
Is located slightly below the connection between the upper left side and the lower left side. On the other hand, the upper end portion of the groove portion 61f has the main electrode portion 3
It is located slightly above the connection between the upper right side and the lower right side of 5a. That is, the two groove portions 61e and 61f slightly overlap each other in the longer diagonal direction of the main electrode portion 35a. In this way, the grooves 61e, 61 are formed so as to overlap each other with respect to the longer diagonal direction of the main electrode part 35a, although each is relatively short.
By providing f, similarly to the first embodiment, when the active layer corresponding to a certain pressure chamber 10 is driven, the deformation transmitted to the adjacent pressure chamber 10 side and the crosstalk caused thereby are prevented. It is possible to reduce. The lower end of the groove 61e and the upper end of the groove 61f do not overlap with each other in the longer diagonal direction of the main electrode portion 35a, and both are substantially at the same position in the longer diagonal direction of the main electrode portion 35a. Even if there is, the same effect can be obtained.

Next explained is an ink jet head according to the fifth embodiment of the invention. FIG. 17 is an enlarged plan view of the actuator unit in the inkjet head according to the present embodiment.

As shown in FIG. 17, in the ink jet head of this embodiment, the pressure chamber 10 is slightly separated from the left side of the main electrode portion 35a of each individual electrode 35 on the upper surface of the actuator unit in plan view. An "V-shaped" (V-shaped) groove portion 61g is provided at substantially the same position as the inner wall (excluding the vicinity of the acute angle portion of the main electrode portion 35a). The groove portion 61g penetrates the piezoelectric sheet 41, and the bottom portion thereof reaches the middle of the piezoelectric sheet 42. Also in the present embodiment, since the groove portion 61g is provided, it is transmitted to the adjacent pressure chamber 10 side when the active layer corresponding to a certain pressure chamber 10 is driven, as in the first embodiment. It is possible to reduce deformation and the resulting crosstalk.

Next explained is an ink jet head according to a sixth embodiment of the invention. FIG. 18 is an enlarged plan view of the actuator unit in the inkjet head according to the present embodiment.

As shown in FIG. 18, the ink jet head of this embodiment is longer than the groove portions 61a and 61b formed in the first embodiment and extends to a position closer to the acute angle portion of the pressure chamber 10. It has existing groove portions 61h and 61i. At this time, when the direction of the six pressure chambers 10 adjacent to the pressure chamber 10 depicted in FIG. 18 is viewed from the center position of the pressure chamber 10 depicted in the center of FIG. Also, since there is at least one groove 61, an extremely high crosstalk suppressing effect can be obtained.

Further, as is clear from the above description,
In the present embodiment, when the second array direction is viewed from the center position of the main electrode portion 35a that causes a large displacement, the center position of a certain pressure chamber 10 and another pressure chamber 10 that is adjacent to the second array direction. There will be at least one groove 61 between them. Therefore, when the active layer corresponding to a certain pressure chamber 10 is deformed, the deformation amount of the piezoelectric sheet 41 in the portion corresponding to another pressure chamber 10 adjacent in the second arrangement direction is such that the groove portion 61 is not formed. It will be smaller than the case. Since the pressure chambers 10 adjacent to each other in the second arrangement direction are often driven simultaneously when printing is performed, the pressure chambers 1 adjacent to each other in the second arrangement direction are provided as in the present embodiment.
By forming at least one groove 61 corresponding to 0, it is possible to significantly suppress the occurrence of crosstalk that adversely affects the image quality.

As is clear from the above-described first to sixth embodiments, in the present invention, the position and shape of the groove portion formed in the actuator unit can be variously changed. For example, the groove portion 61 described in the first embodiment.
a and 61b, and the groove portion 61c described in the second embodiment.
Both may be formed in the actuator unit.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments, and various design changes are possible within the scope of the claims. Is. For example, in the above-described embodiment, the materials for the piezoelectric sheet and the electrodes are not limited to those described above, and other known materials may be used.
Further, the planar shape and cross-sectional shape of the pressure chamber, the arrangement form, the number of piezoelectric sheets including the active layer, the number of inactive layers, and the like may be appropriately changed. For example, only one elongated actuator unit may be bonded to the flow path unit. Further, the piezoelectric sheet including the active layer and the inactive layer may have different layer thicknesses.

[0107]

As described above, according to the present invention,
It is possible to suppress the occurrence of crosstalk.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an inkjet printer including an inkjet head according to a first embodiment of the present invention.

FIG. 2 is a perspective view of the inkjet head according to the first embodiment of the present invention.

FIG. 3 is a sectional view taken along line III-III in FIG.

4 is a plan view of a head body included in the inkjet head depicted in FIG. 2. FIG.

5 is an enlarged view of a region surrounded by an alternate long and short dash line drawn in FIG. 4. FIG.

FIG. 6 is an enlarged view of a region surrounded by an alternate long and short dash line drawn in FIG.

FIG. 7 is a partial cross-sectional view of the head body depicted in FIG.

FIG. 8 is an enlarged view of a region surrounded by a chain double-dashed line drawn in FIG.

9 is a partially exploded perspective view of the head body depicted in FIG.

FIG. 10 is an enlarged plan view of an actuator unit.

11 is a partial cross-sectional view of the head body shown in FIG. 4 taken along the line XI-XI in FIG.

12 is a partial cross-sectional view corresponding to FIG. 11 in a process in the middle of manufacturing the head body shown in FIG.

FIG. 13 is an enlarged plan view of an actuator unit included in an inkjet head according to a second embodiment of the present invention.

FIG. 14 is a partial cross-sectional view of a head body of an inkjet head according to a second embodiment of the present invention.

FIG. 15 is an enlarged plan view of an actuator unit included in an inkjet head according to a third embodiment of the present invention.

FIG. 16 is an enlarged plan view of an actuator unit included in an inkjet head according to a fourth embodiment of the present invention.

FIG. 17 is an enlarged plan view of an actuator unit included in an inkjet head according to a fifth embodiment of the present invention.

FIG. 18 is an enlarged plan view of an actuator unit included in an inkjet head according to a sixth embodiment of the present invention.

[Explanation of symbols]

1 inkjet head 1a head body 4 flow path unit 5 manifold 5a Sub-manifold 8 ink outlets 10 Pressure chamber 12 apertures 21 Actuator unit 22 Cavity plate 30 nozzle plate 32 ink flow path 34 common electrode 35 individual electrodes 35a Main electrode part 35b Auxiliary electrode part 36a, 36b Reinforcing electrode 41 Piezoelectric sheet (layer including active layer) 42, 43, 44 Piezoelectric sheet (inactive layer) 61a, 61b Grooves (recesses) 101 inkjet printer 136 Flexible Printed Circuit (FPC)

Claims (12)

[Claims] 1. A flow path unit including a plurality of pressure chambers, one end of which is connected to a nozzle and the other end of which is connected to an ink supply source, wherein the plurality of pressure chambers are arranged adjacent to each other in a matrix, and An actuator unit fixed to one surface of the flow path unit for changing the volume is provided, and the actuator unit includes a piezoelectric sheet continuously arranged over a plurality of the pressure chambers, and the piezoelectric sheet. A common electrode disposed on one side of the sheet and kept at a constant potential, a plurality of individual electrodes disposed on the other side of the piezoelectric sheet and disposed at positions corresponding to the respective pressure chambers, the piezoelectric sheet And an indentation formed in a corresponding region between the pressure chambers. 2. The pressure chambers are formed in a parallelogram shape, the pressure chambers are arranged in a matrix so that the sides of the pressure chambers are parallel to each other, and the individual electrodes are formed in a shape similar to the pressure chambers. The inkjet head according to claim 1, wherein the recess is formed so as to substantially surround the pressure chamber. 3. The inkjet head according to claim 1, wherein the recess is formed along an outer edge of the pressure chamber. 4. The ink jet head according to claim 3, wherein the concave portion is formed corresponding to a region of the pressure chamber excluding an acute angle portion. 5. The flow path unit includes a plurality of rows in which the plurality of pressure chambers are arranged in a row, and one pressure chamber in one row is adjacent to the pressure chamber in the row. A recess is formed in a region between the pressure chamber and another pressure chamber, and at least one recess is formed in the region when viewed from the center of the one pressure chamber toward the other pressure chamber. The inkjet head according to claim 3. 6. The recess is formed in a region between one pressure chamber and at least six pressure chambers adjacent to the pressure chamber. The inkjet head according to claim 3, wherein at least one recess is formed in the region when the direction of the adjacent pressure chambers is viewed from the one pressure chamber. 7. The method according to claim 1, wherein the concave portion is formed on a surface opposite to a surface fixed to the one surface of the flow path unit. Inkjet head. 8. The ink jet head according to claim 1, wherein the concave portion penetrates the actuator unit. 9. The ink jet head according to claim 1, wherein the common electrode is formed as one continuous body in the actuator unit. 10. One or a plurality of inactive layers made of a piezoelectric sheet is arranged between the flow path unit and the piezoelectric sheet sandwiched between the common electrode and the individual electrode. The inkjet head according to any one of claims 1 to 9. 11. The ink jet head according to claim 1, wherein the piezoelectric sheet farthest from the pressure chamber is sandwiched between the common electrode and the individual electrode. . 12. A flow path unit including a plurality of pressure chambers, one end of which is connected to a nozzle and the other end of which is connected to an ink supply source, wherein the plurality of pressure chambers are arranged adjacent to each other in a matrix, and the pressure chambers An ink jet printer including an ink jet head including an actuator unit fixed to one surface of the flow path unit for changing a volume, wherein the actuator unit is continuously arranged over a plurality of the pressure chambers. Piezoelectric sheet, a common electrode arranged on one side of the piezoelectric sheet and kept at a constant potential, and a plurality of common electrodes arranged on the other side of the piezoelectric sheet and arranged at positions corresponding to the respective pressure chambers. And an individual electrode and a concave portion formed in a region corresponding to the pressure chamber of the piezoelectric sheet. .