WO2012144597A1

WO2012144597A1 - Ink-jet head

Info

Publication number: WO2012144597A1
Application number: PCT/JP2012/060716
Authority: WO
Inventors: 光高松; 渡辺　英生
Original assignee: コニカミノルタＩｊ株式会社
Priority date: 2011-04-22
Filing date: 2012-04-20
Publication date: 2012-10-26
Also published as: EP2700506A4; JP5846201B2; JPWO2012144597A1; EP2700506A1; EP2700506B1

Abstract

The purpose of the present invention is to provide an ink-jet head which enables the disposition of wiring electrodes at high density and can easily support an increased density of channels. An ink-jet head comprises a head chip (1) in which drive channels and dummy channels are alternately disposed, and a wiring substrate (3), and is characterized in that in the wiring substrate (3), through-holes for supplying ink are formed only at positions corresponding to openings of the drive channels, at least one wiring electrode passes between adjacent through-holes in at least one row of through-holes among a plurality of rows of through-holes corresponding to channel rows and extends to an end of the wiring substrate projecting sideways from the head chip, and at least one wiring electrode passing between the through-holes is not in contact with an opening of the dummy channel and overlaps with the opening of the dummy channel as seen from an ink discharge direction.

Description

Inkjet head

The present invention relates to an ink jet head, and more particularly, to an ink jet head having a head chip in which drive channels and dummy channels are alternately arranged, and capable of increasing the density of the channels.

By applying a drive signal of a predetermined voltage to the drive electrode formed on the drive wall that partitions the channel, the drive wall is subjected to shear deformation, and ink in the channel is ejected from the nozzle by using the pressure generated at that time. As such a shear mode type ink jet head, one having a so-called harmonica type head chip in which opening portions of channels are respectively arranged on the front surface and the rear surface is known.

In the harmonica type head chip, since the drive electrode faces the channel and is not exposed to the outside, the problem is how to electrically connect each drive electrode to the drive circuit. Among the channel rows arranged in parallel on the head chip, the channel row located outside forms a connection electrode that is electrically connected to the drive electrode from each channel to the end of the head chip using the rear surface of the head chip. It is easy to make an electrical connection with an FPC or the like at the end of the head chip. However, when the drive signal is applied to the drive electrodes of the channel rows located on the inner side from the end of the head chip, the connection electrodes that are electrically connected to the drive electrodes extend beyond the outer channel row to the end of the head chip. There is a problem that it has to be formed.

Conventionally, in order to solve such a problem, Patent Document 1 discloses that four channel rows are arranged by shifting the channel pitch by ¼, and driving electrodes in each channel are arranged on the rear side of the head chip. An electrical contact is formed by being exposed to the periphery of each of the openings, a flexible substrate having a wiring electrode formed on one side of the rear surface of the head chip, and a wiring electrode forming surface facing the rear surface of the head chip, It is disclosed that a drive signal can be applied from one side of the head chip to each drive electrode of all channel rows by bonding so as to cover the entire rear surface.

In the flexible substrate, through holes are formed at positions corresponding to the respective channels, and ink can be supplied to the respective channels through the through holes. Between adjacent through-holes in the same channel row, a wiring electrode is formed which is electrically connected to the electrical contacts of the channel row located on the inner side. In Patent Document 1, by shifting the pitch by ¼ between the four channel columns, a maximum of three wiring electrodes pass between the channels. Since each wiring electrode passes between adjacent through holes, the wiring electrodes are arranged so as to be within the range of the width (thickness) of the drive wall when viewed from the direction along the ink ejection direction.

By the way, in the shear mode type ink-jet head, each channel in the channel row is divided into a drive channel that discharges ink and a dummy channel that does not discharge ink, and the channel row is configured by alternately arranging these channels. There is an ink jet head having an independently driven type head chip. By alternately arranging the drive channels and the dummy channels, it is possible to simultaneously eject ink from all the drive channels.

In Patent Document 2, a connection electrode that is electrically connected to a drive electrode in each channel is formed on the rear surface of such an independent drive type harmonica type head chip, and is positioned inside a plurality of juxtaposed channel rows. The connection electrode of the channel row to be used is formed on the rear surface of the head chip on the rear surface of the head chip by using a flexible substrate having a wiring electrode formed on one side so as to have a narrow width equal to the width of the wiring electrode. Pulling out to the end is disclosed.

The flexible substrate on which the wiring electrode is formed is provided so as to close the opening on the rear surface side of the dummy channel when crossing the outer channel row. Since the surface opposite to the wiring electrode formation surface faces the rear surface of the head chip, the flexible substrate may cause a short circuit with the drive electrode or connection electrode exposed in or near the opening of the dummy channel. Is prevented. In addition, since the flexible substrate is provided so as to close the opening on the rear surface side of the dummy channel, there is an advantage that it is easy to cope with the higher density of the channel.

JP 2002-178509 A JP 2008-143167 A

Normally, harmonica type head chips are supplied with ink from the rear side to each channel. For this reason, if the wiring electrode is exposed on the rear surface side of the head chip as described in Patent Document 2, the wiring electrode comes into direct contact with the ink, and there is a problem of electrode corrosion.

In order to prevent the electrode from coming into direct contact with the ink, it is generally known that a protective film is formed on the surface of the electrode. However, depending on the ink used, the protective film may penetrate, From the viewpoint of avoiding corrosion of steel, there are still problems to be solved.

As described in Patent Document 1, when the wiring electrode is disposed so as to face the rear surface of the head chip, the wiring electrode can be prevented from coming into direct contact with the ink, but is wired beyond the channel row. When viewed from the direction along the ink ejection direction, the wiring electrode passes over the driving wall between the channels, so the width of the driving wall becomes narrower as the channel becomes higher in density, making it difficult to achieve high density. There is a problem.

That is, in the technique described in Patent Document 1, as the channels become denser and the space between the channels through which the wiring electrodes should pass (the width of the drive wall) becomes narrower, the wiring electrodes are not formed narrower. It must not be. However, if the wiring electrode is made narrow, the electrical resistance is increased, and there is a limit to the narrowing of the wiring electrode.

Therefore, the present invention is such that the substrate having the wiring electrode is bonded to the rear surface of the independent drive type harmonica type head chip having a plurality of channel rows so that the wiring electrode is on the rear surface side of the head chip. An object is to provide an inkjet head in which wiring electrodes can be arranged with high density and can easily cope with high density of channels.

Other problems of the present invention will become apparent from the following description.

The above problems are solved by the following inventions.

1. Channels and drive walls made of piezoelectric elements are alternately arranged, and a plurality of channel rows in which drive electrodes are formed on the drive wall facing the channel are arranged side by side, and openings of the channels are respectively provided on the front surface and the rear surface. A connecting electrode that is electrically connected to the driving electrode in the channel is formed on the rear surface, and the channel row is alternately arranged with a driving channel that ejects ink and a dummy channel that does not eject ink. A head chip,
A wiring board that covers the plurality of channel rows with respect to the rear surface of the head chip and is bonded so as to protrude to the side of the head chip;
By electrically connecting the wiring electrodes formed on the surface of the wiring board on the side bonded to the head chip to the connection electrodes, each of the connection electrodes is electrically drawn to the end of the wiring board. An inkjet head that discharges ink in the drive channel from a nozzle by applying a voltage to the drive electrode via the wiring electrode and the connection electrode;
In the wiring board, through holes for supplying ink are formed only at positions corresponding to the openings of the drive channels, and at least one of the plurality of through hole rows corresponding to the channel rows. Between the adjacent through-holes in the row of through-holes, at least one of the wiring electrodes passes through and extends to the end of the wiring board that protrudes to the side of the head chip,
At least one of the wiring electrodes passing between the through holes is not in contact with the opening of the dummy channel and overlaps the opening of the dummy channel when viewed from the ink discharge direction. An inkjet head.

2. 2. The inkjet head according to 1, wherein the wiring board is made of any one of glass, silicon, and ceramics.

3. The head chip has two channel rows of A rows and B rows,
One wiring corresponding to the drive channel of the B row among the wiring electrodes electrically connected to the connection electrode of the channel row of the B row is provided between the through holes of one A row. 3. The ink jet head according to

claim

1 or 2, wherein a total of two wiring electrodes of the electrode and one wiring electrode corresponding to the dummy channel in the B row adjacent to the driving channel pass therethrough.

4). The head chip has three channel rows of A row, B row and C row,
Among the wiring electrodes electrically connected to the connection electrode of the channel row of the C row, between the through holes of one B row, one wiring corresponding to the drive channel of the C row A total of the two wiring electrodes of the electrode and one wiring electrode corresponding to the dummy channel in the C row adjacent to the driving channel pass through,
One wiring corresponding to the drive channel of the B row among the wiring electrodes electrically connected to the connection electrode of the channel row of the B row is provided between the through holes of one A row. An electrode, two of the wiring electrodes corresponding to the dummy channel in the B row adjacent to the driving channel, one wiring electrode corresponding to the driving channel in the C row, and the driving channel 4. The inkjet head according to claim 1, wherein a total of four wiring electrodes including two of the one wiring electrode corresponding to the dummy channel in the C row adjacent to the C row pass.

According to the present invention, even if the substrate having the wiring electrode is joined to the rear surface of the independently driven harmonica type head chip having a plurality of channel rows so that the wiring electrode is on the rear surface side of the head chip, It is possible to provide an inkjet head in which wiring electrodes can be arranged with high density and can easily cope with high density of channels.

1 is an exploded perspective view of an inkjet head according to the present invention. Partial rear view of a head chip according to the present invention Partial rear view showing the bonding state between the head chip and the wiring board Sectional view along line (iv)-(iv) in FIG. Sectional view along line (v)-(v) in FIG. Partial rear view showing a bonding state between a head chip having three channel rows and a wiring board Sectional view along line (vii)-(vii) in FIG. Partial sectional view of an inkjet head showing a comparative example

The head chip in the present invention has a plurality of parallel channel rows in which channels and drive walls made of piezoelectric elements are alternately arranged. The head chip is arranged with channel openings facing the front and rear surfaces, respectively. Each channel is formed in a straight shape whose cross-sectional shape does not change from the rear opening (channel inlet) to the front opening (channel outlet), and a drive electrode is formed on the surface of the drive wall facing each channel. Is done.

Such a head chip is a hexagonal so-called shear mode harmonica type head chip, and by applying a drive signal of a predetermined voltage to each drive electrode on both sides of the drive wall, the drive wall is shear-deformed, A change in pressure for ejection is applied to the ink supplied into the channel, and the ink is ejected as an ink droplet from a nozzle disposed on the front surface of the head chip.

In the present invention, in such a hexahedral harmonica type head chip, a surface on which nozzles are arranged and ink is ejected is defined as a “front surface”, and a surface on the opposite side is defined as a “rear surface”. A direction parallel to the front surface or the rear surface of the head chip and away from the head chip is defined as “side” of the head chip.

The channel row in the present invention is an independently driven head chip in which drive channels and dummy channels are alternately arranged. On the rear surface of the head chip, connection electrodes that are electrically connected to the drive electrodes in the drive channel and the dummy channel are individually formed and arranged on the rear surface of the head chip at the same pitch as the corresponding drive channel or dummy channel.

The drive channel is a channel that ejects ink from the nozzles according to image data during image recording, and the dummy channel is a channel that does not always eject ink regardless of the image data. Since the dummy channel does not need to eject ink, generally, ink is not filled or a nozzle corresponding to the dummy channel is not formed on the nozzle plate.

The wiring board bonded to the rear surface of the head chip by an adhesive is an intermediate wiring member that connects between the head chip and the drive circuit. Preferably, the electrical connection between the head chip and the electric wiring member from the drive circuit is relayed to facilitate electrical connection with the electric wiring member. This wiring board electrically draws out each drive electrode to the side orthogonal to the channel row of the head chip via the corresponding connection electrode.

The wiring board according to the present invention is bonded to the rear surface of the head chip so as to cover all the channel rows opened in the rear surface and to have the end portion protruding to the side perpendicular to the channel row in the head chip. .

This wiring board has a through hole for enabling ink supply in the driving channel only at a position corresponding to the driving channel of the head chip. Therefore, the opening on the rear surface side of the dummy channel is closed by the wiring board.

The opening means a portion where the dummy channel is opened flush with the rear surface of the head chip.

A wiring electrode that is electrically connected to each connection electrode arranged on the rear surface of the head chip is formed on a surface (hereinafter referred to as a surface) of the wiring substrate that is bonded to the head chip. In a state where the wiring substrate is bonded to the rear surface of the head chip, each wiring electrode has one end electrically connected to the corresponding connection electrode and the other end protruding to the side of the head chip. It extends to the end.

Among the plurality of through hole rows of the wiring substrate corresponding to the channel row of the head chip, at least one wiring electrode passes between the adjacent through holes in at least one through hole row. The wiring electrode passing between the through holes is a wiring electrode that is electrically connected to the connection electrode of another channel row.

At least one wiring electrode passing between the through holes is in non-contact with the opening of the dummy channel in a state where the wiring substrate is bonded to the rear surface of the head chip via an adhesive, and When viewed from the ink ejection direction, it overlaps the opening of the dummy channel. That is, the wiring electrode passing between the through holes is not in contact with the rear surface of the head chip other than in contact with the connection electrode to which the wiring electrode is to be conducted.

As a result, even if the wiring board is bonded to the entire rear surface of the head chip so that the wiring electrode is on the rear surface side of the head chip, the wiring electrode is in contact with the rear surface of the head chip other than the connection electrode of the corresponding channel. Therefore, occurrence of crosstalk and short circuit can be prevented. In addition, since at least one wiring electrode passing between the through holes passes over the opening of the dummy channel, even if the space between the channels is narrow, it is between adjacent through holes including the opening of the dummy channel. Since all of the space can be used, high-density wiring is possible without particularly reducing the width of the wiring electrode, and the channel density can be increased.

In such an ink jet head, an electric wiring member having a wiring electrically connected to the wiring electrode is joined to an end portion of the wiring substrate protruding to the side of the head chip. The electric wiring member is connected to the drive circuit, and a voltage from the drive circuit is applied to the drive electrode via the wiring electrode and the connection electrode of the wiring board. Thereby, the ink in a drive channel can be discharged from a nozzle. As the electrical wiring member, a flexible printed circuit board (hereinafter referred to as FPC) is preferably used.

In the wiring board according to the present invention, the substrate material is preferably one of glass, silicon, and ceramics. When these are used, the rigidity is higher than that of the resin material having the same thickness, the wiring board can be made thinner by that amount, and the flow path resistance of the through hole can be suppressed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is an exploded perspective view of an inkjet head, and FIG. 2 is a partial rear view of the head chip.

In the figure, 1 is a shear mode type harmonica head chip, 2 is a nozzle plate, 3 is a wiring board, and 4 is an FPC.

The head chip 1 has two channel rows, A row and B row. Here, the lower channel row in FIG. 2 is the A row, and the upper channel row is the B row. In each channel row,

drive channels

11A and 11B and

dummy channels

12A and 12B are alternately arranged. Drive

walls

13A and 13B made of piezoelectric elements are formed between the

drive channels

11A and 11B and the

adjacent dummy channels

12A and 12B. Each

drive channel

11A, 11B and each

dummy channel

12A, 12B are opened to the front surface 1a and the rear surface 1b of the head chip 1, respectively, and the drive electrode 14 is formed in close contact with the inner surface by plating, vapor deposition, sputtering, or the like. Has been.

In the head chip 1, the drive channel 11A and the dummy channel 12A of the channel row of the A row and the drive channel 11B and the dummy channel 12B of the channel row of the B row are arranged so as to be shifted from each other by one pitch. That is, when viewed in a direction parallel to the rear surface 1b of the head chip 1 and orthogonal to the channel row, the A-channel drive channel 11A and the B-row dummy channel 12B are positioned on the same straight line, and the A-row dummy channel The channel 12A and the drive channel 11B in the B row are located on the same straight line.

On the rear surface 1b of the head chip 1,

connection electrodes

15A and 15B that are electrically connected to the drive electrodes 14 of the

drive channels

11A and 11B and the

dummy channels

12A and 12B are formed by plating, vapor deposition, sputtering, or the like. One end of each

connection electrode

15A, 15B is electrically connected to the drive electrode 14 in the

corresponding drive channel

11A, 11B or

dummy channel

12A, 12B. The other end of each connection electrode 15A corresponding to the drive channel 11A and the dummy channel 12A in the A row is formed from the inside of each

channel

11A, 12A to one end edge 1c (lower end edge in FIG. 2) of the head chip 1. However, in each connection electrode 15B corresponding to the drive channel 11B and the dummy channel 12B in the B row, the connection electrodes 15B extend from the

channels

11B and 12B toward the A row side and before the channel row in the A row. Is formed. Accordingly, all of the

connection electrodes

15A and 15B extend from the

channels

11A, 11B, 12A, and 12B in the same direction (direction of the edge 1c).

The nozzle plate 2 is bonded to the front surface 1a of the head chip 1 with an adhesive. In the nozzle plate 2, nozzles 21 are opened only at positions corresponding to the

drive channels

11A and 11B.

The wiring board 3 is a flat board that is larger than the outer shape of the rear surface 1 b of the head chip 1. When the wiring board 3 is joined to the rear surface 1b of the head chip 1, it is preferably difficult to bend, and glass, silicon, and ceramics are preferably used. In this embodiment, a glass substrate is used.

In the bonding region 31 (the region indicated by the alternate long and short dash line in FIG. 1) 31 that is bonded to the rear surface 1b of the head chip 1, only the positions corresponding to the

drive channels

11A and 11B opened on the rear surface 1b of the head chip 1 are not present. Through

holes

32A and 32B for individually supplying ink into the

drive channels

11A and 11B from the illustrated common ink chamber are individually opened. The opening areas of the through

holes

32A and 32B are the same as or slightly larger than the opening areas of the

drive channels

11A and 11B.

The thickness of the wiring board 3 is preferably 0.3 mm to 0.8 mm from the viewpoint of ensuring appropriate rigidity while suppressing the flow resistance of the through

holes

32A and 32B.

Further, on the surface of the wiring board 3,

wiring electrodes

33A and 33B that are electrically connected in a one-to-one correspondence with the

connection electrodes

15A and 15B arranged on the rear surface 1b of the head chip 1 are provided on the wiring board. 3 is formed by plating, vapor deposition, sputtering, or the like so as to extend in a direction crossing the channel row of the head chip 1 on the surface of 3.

One end of each wiring electrode 33A corresponding to the connection electrode 15A drawn from each

channel

11A, 12A in the A row is located in the vicinity corresponding to each

channel

11A, 12A in the A row in the bonding region 31, and the other end is , Extending from the bonding region 31 toward a side perpendicular to the channel row of the head chip 1, protruding from the bonding region 31 and reaching the end 3 a of the wiring substrate 3.

On the other hand, one end of each wiring electrode 33B corresponding to the connection electrode 15B drawn from each

channel

11B, 12B in the B row is located in the vicinity corresponding to each

channel

11B, 12B in the B row in the junction region 31. The end extends in the same direction as the wiring electrode 33A, passes between adjacent through holes 32A in the A row, protrudes from the bonding region 31, reaches the end portion 3a of the wiring board 3, and alternates with the wiring electrodes 33A. It is arranged to be.

The wiring board 3 is positioned so that the

wiring electrodes

33A and 33B are electrically connected to the

connection electrodes

15A and 15B of the corresponding head chip 1, and bonded to the rear surface 1b of the head chip 1 by an adhesive. Yes. As the adhesive, an anisotropic conductive adhesive containing conductive particles can be used, but it is preferable to use an adhesive containing no conductive particles in order to increase the reliability of short circuit prevention. .

Next, details of the wiring electrode 33B passing between the through

holes

32A and 32A in the A row will be further described with reference to FIGS.

3 is a partial rear view of the state in which the wiring board 3 is bonded to the rear surface 1b of the head chip 1 as viewed from the back side of the wiring board 3. FIG. 4 is a line (iv)-(iv) in FIG. FIG. 5 is a sectional view taken along line (v)-(v) in FIG.

Wiring electrodes electrically connected to the connection electrodes 15B for row B, B and the drive channel connection electrode 15B and the wiring electrode 33B ₁ that is electrically connected to 11B of the column, the connection electrode 15B electrically dummy channel 12B of row B consisting wiring connected electrodes 33B ₂ Metropolitan to. These

wiring electrodes

33B ₁ and 33B ₂ extend between the adjacent through

holes

32A and 32A in the A row to the end portion 3a of the wiring board 3. A row of through holes 32A in the surface of the wiring board 3, between 32A, B 1 present between the wiring electrodes 33B ₁ for connecting electrode 15B electrically adjacent one drive channel 11B connected in sequence, one dummy total two is arranged between the wiring electrodes 33B ₂ for one electrically connected to the connection electrode 15B of channel 12B.

Wiring electrodes 33B ₂ having one end connected to the connecting electrodes 15B and electrically dummy channel 12B of the B column, the other end side of the through hole 32A of the A column from a connection portion between said connection electrode 15B, wire toward between 32A substrate 3 passes through the opening 120A so as to partially cover the edge 121a of the opening 120A of the dummy channel 12A in the A row located between the through

holes

32A and 32A. Bends on the surface of the wiring board 3 toward the space between

adjacent connection electrodes

15A and 15A in row A so as not to contact the connection electrode 15A of the dummy channel 12A, and is electrically connected to the

connection electrodes

15A and 15A. It extends to the end portion 3a so as to be parallel to the

wiring electrodes

33A and 33A.

The wiring electrodes 33B ₁ whose one end is connected to the connection electrode 15B and the electrically driven channel 11B of row B, the other end is positioned between the through

holes

32A, 32A of the A column from a connection portion between said connection electrode 15B on the opening 120A of the dummy channels 12A of the a column, after passing through the opening upper 120A so as to cover a portion to the wiring electrodes 33B ₂ faces the edge portion 121a which is overlaying edges on 121b, the dummy so as not to contact with the connection electrodes 15A of the channel 12A, bent to the connection electrodes 15A of adjacent a column, and the wiring electrodes 33B ₂ on the surface of the wiring board 3 toward between 15A opposite the connection electrodes 15A, It extends to the end 3a so as to be parallel to the

wiring electrodes

33A and 33A electrically connected to 15A.

Note that the

edges

121a and 121b of the opening 120A of the dummy channel 12A are drive electrodes formed on the opposing drive wall 13 among the four edges forming the periphery of the opening 120A of the dummy channel 12A. 14 is the edge portion on the opening side.

As described above, in the inkjet head according to the present invention, the

wiring electrodes

33B ₁ and 33B ₂ corresponding to the B-row channel row adjacent to the A-row channel row located on the outermost side of the head chip 1 are arranged. When passing between the through

holes

32A and 32A in the A row, not only in the space on the

drive walls

13A and 13A in the A row on the rear surface 1b of the head chip 1, but also in the opening 120A of the dummy channel 12A from this space On the other hand, as shown in FIG. 4, a part protrudes by the amount of protrusion c. The

wiring electrodes

33B ₁ and 33B ₂ are arranged so as to partially overlap the

edges

121a and 121b of the opening 120A of the dummy channel 12A when viewed in the ink ejection direction (from the top to the bottom in FIG. 4). Has been.

Since these

wiring electrodes

33B ₁ and 33B ₂ are both formed in close contact with the surface of the wiring substrate 3, they are not in contact with the opening 120A of the dummy channel 12A, that is, the rear surface 1b of the head chip 1. Since the gap S corresponding to the thickness of the

connection electrodes

15A and 15B + the thickness of the

wiring electrodes

33A and 33B is formed between the head chip 1 and the wiring board 3, as shown in FIGS. The surfaces of the

wiring electrodes

33B ₁ and 33B ₂ are separated from the rear surface 1b of the head chip 1 by a distance corresponding to the thickness of the

connection electrodes

15A and 15B at a portion other than the connection portion with the connection electrode 15B. The surface of the

wiring electrodes

33B ₁ and 33B ₂ and the rear surface 1b of the head chip 1 are insulated by being filled with the adhesive 50. Therefore, even if the

wiring electrodes

33B ₁ and 33B ₂ are arranged so as to overlap the opening 120A, the

wiring electrodes

33B ₁ and 33B ₂ do not come into contact with the driving electrode 14 exposed in the opening 120A, and there is a risk of crosstalk or short circuit. Absent.

Further, the wiring space of the

wiring electrodes

33B ₁ and 33B ₂ is not limited to the space corresponding to the thickness of the drive wall 13A, and a wide area extending between the through

holes

32A and 32A can be used. Therefore, the wiring electrodes 33B ₁ 33B ₂ can be formed wide. Therefore, an increase in the electrical resistance of the

wiring electrodes

33B ₁ and 33B ₂ can be suppressed.

The

wiring electrodes

33B ₁ and 33B ₂ passing over the opening 120A of the dummy channel 12A in the A column are wired so as to overlap the opening 120A of the dummy channel 12A, and then connected to the dummy channel 12A. It is bent so as to avoid the portion of the connection electrode 15A so as not to contact 15A, and is parallel to the wiring electrode 33A at the end 3a of the wiring board 3.

In the above embodiment, the head chip 1 is exemplified as having two channel rows of A row and B row, but the number of channel rows may be three or more.

6 and 7, an ink jet head using a head chip 1 ′ having three channel rows of A row, B row and C row will be described.

6 is a partial rear view of the state in which the wiring board 3 ′ is bonded to the rear surface 1b of the head chip 1 ′ as viewed from the back side of the wiring board 3 ′, and FIG. 7 is (vii)-(vii) in FIG. FIG. In this head chip 1 ′, the channel rows A and B have the same configuration as that of the head chip 1 including the two channel rows described above, and thus the description thereof is omitted here. 3 and 4 are parts having the same configuration, and detailed description thereof is omitted.

The C columns are arranged such that the arrangement pitch of the drive channels 11C and the dummy channels 12C is the same as the arrangement pitch of the drive channels 11A and the dummy channels 12A of the A columns.

In this embodiment, two wiring electrodes 33C that pass between adjacent through

holes

32B, 32B in the B row of the wiring board 3 ′, that is, wiring that is electrically connected to the connection electrode 15C of the drive channel 11C in the C row. The electrode 33C ₁ and the wiring electrode 33C ₂ electrically connected to the connection electrode 15C of the dummy channel 12C in the C row pass so as to overlap with the opening 120B of the dummy channel 12B in the B row, and are described above. It has the same configuration as the

wiring electrodes

33B ₁ and 33B ₂ that pass between the through

holes

32A and 32A in the A row in the embodiment of the two channel rows. In this case, A in the code is read as B, and B is read as C.

On the other hand, between the through

holes

32A and 32A in the A row, the

wiring electrodes

33B ₁ and 33B ₂ that are electrically connected to the connection electrodes 15B in the B row, and the wiring electrodes that are electrically connected to the connection electrodes 15C in the C row. A total of four of 33C ₁ and 33C ₂ are arranged.

At this time, as shown in FIG. 7, the wiring electrodes 33B ₁ and 33C ₁ located on the inner side of the opening 120A are overlapped with the openings 120A of the dummy channels 12A in the A row when viewed from the ink discharge direction. The wiring electrodes 33B ₂ and 33C ₂ located on the outer side are respectively disposed within the thickness range of the drive wall 13A. Each of the

wiring electrodes

33B ₁ , 33B ₂ , 33C ₁ , 33C ₂ is not in contact with the rear surface 1b of the head chip 1, and the adhesive 50 is filled between the rear surfaces 1b.

Thus, according to the present invention, it is possible to arrange a total of four

wiring electrodes

33B ₁ , 33B ₂ , 33C ₁ , 33C ₂ by using the entire space between the through

holes

32A, 32A. It is possible to cope with higher density.

The head chip 1 having two channel rows shown in FIGS. 1 to 5 is configured so that the lead-out directions of the

wiring electrodes

33A and 33B on the surface of the wiring board 3 are on both ends with the head chip interposed therebetween. The two head chips 1 can be arranged in parallel to form a head chip having four channel rows. In the case of the head chip 1 ′ having three channel rows shown in FIGS. 6 and 7, a head chip having six channel rows can be similarly formed.

In a head chip having two channel rows, when the wiring electrodes on the surface of the wiring board are formed as shown in FIGS. 3 to 5 (the present invention), and as shown in FIG. The channel density at which wiring is possible was verified in the case where each of the two wiring electrodes was formed on the drive wall so as not to overlap the opening of the dummy channel (comparative example).

When the channel density is 180 dpi (dot per inch), as shown in Table 1, the drive wall thickness is 59 μm, the channel width is 82 μm, and the through hole width is 102 μm.

Here, in consideration of the processing accuracy and the bonding position accuracy between the head chip and the wiring board, in the case of the comparative example, the distance a1 between the wiring electrode and the adjacent through hole, and the opening between the wiring electrode and the dummy channel, The distances a2 must be 20 μm or more. In this case, the width of each wiring electrode is 9 μm at the maximum. Wiring with a width of 20 μm or less is highly difficult to manufacture, and even if it can be manufactured, the wiring thickness must be reduced in proportion to the wiring width. It is expected to adversely affect the ink ejection.

Therefore, in the case of this comparative example, in order to realize a practical wiring width, the channel density up to about 120 dpi is the limit as shown in Table 1.

On the other hand, in the case of the present invention, as shown in Table 2, even when the channel density is 180 dpi, the width of the wiring electrode can be a maximum of 46 μm, and 1/3 of the distance b in FIG. The width that can be passed.

In the case of two channel rows, it can be seen that a wiring width of 22 μm can be secured even at 300 dpi, and a higher density can be achieved than in the comparative example.

In the case of the present invention, even if three channel rows are used, a distance b of 1/7 can pass through the wiring electrode, and can be realized if the channel density is 180 dpi.

1, 1 ': Head chip 1a: Front surface 1b: Rear surface 1c:

Edges

11A, 11B, 11C: Drive

channels

12A, 12B, 12C:

Dummy channels

120A, 120B:

Openings

121a, 121b:

Edges

13A, 13B: Drive walls 14: driving

electrodes

15A, 15B: connection electrode 2: nozzle plate 21: nozzle 3,3 ': wiring board 3a: end 31:

junction regions

32A, 32B, 32C: through holes _{33A, 33B, 33B 1, 33B} 2 , 33C ₁ , 33C ₂ : Wiring electrode 4: FPC
50: Adhesive

Claims

Channels and drive walls made of piezoelectric elements are alternately arranged, and a plurality of channel rows in which drive electrodes are formed on the drive wall facing the channel are arranged side by side, and openings of the channels are respectively provided on the front surface and the rear surface. A connecting electrode that is electrically connected to the driving electrode in the channel is formed on the rear surface, and the channel row is alternately arranged with a driving channel that ejects ink and a dummy channel that does not eject ink. A head chip,
A wiring board that covers the plurality of channel rows with respect to the rear surface of the head chip and is bonded so as to protrude to the side of the head chip;
By electrically connecting the wiring electrodes formed on the surface of the wiring board on the side bonded to the head chip to the connection electrodes, each of the connection electrodes is electrically drawn to the end of the wiring board. An inkjet head that discharges ink in the drive channel from a nozzle by applying a voltage to the drive electrode via the wiring electrode and the connection electrode;
In the wiring board, through holes for supplying ink are formed only at positions corresponding to the openings of the drive channels, and at least one of the plurality of through hole rows corresponding to the channel rows. Between the adjacent through-holes in the row of through-holes, at least one of the wiring electrodes passes through and extends to the end of the wiring board that protrudes to the side of the head chip,
At least one of the wiring electrodes passing between the through holes is not in contact with the opening of the dummy channel and overlaps the opening of the dummy channel when viewed from the ink discharge direction. An inkjet head.
2. The ink jet head according to claim 1, wherein the wiring board is made of any one of glass, silicon, and ceramics.
The head chip has two channel rows of A rows and B rows,
One wiring corresponding to the drive channel of the B row among the wiring electrodes electrically connected to the connection electrode of the channel row of the B row is provided between the through holes of one A row. 3. The ink jet head according to claim 1, wherein a total of the two wiring electrodes of the electrode and one wiring electrode corresponding to the dummy channel in the B row adjacent to the driving channel pass therethrough. .
The head chip has three channel rows of A row, B row and C row,
Among the wiring electrodes electrically connected to the connection electrode of the channel row of the C row, between the through holes of one B row, one wiring corresponding to the drive channel of the C row A total of the two wiring electrodes of the electrode and one wiring electrode corresponding to the dummy channel in the C row adjacent to the driving channel pass through,
One wiring corresponding to the drive channel of the B row among the wiring electrodes electrically connected to the connection electrode of the channel row of the B row is provided between the through holes of one A row. An electrode, two of the wiring electrodes corresponding to the dummy channel in the B row adjacent to the driving channel, one wiring electrode corresponding to the driving channel in the C row, and the driving channel 3. The inkjet head according to claim 1, wherein a total of four wiring electrodes including two of the one wiring electrode corresponding to the dummy channel in the C row adjacent to the C line pass.