JP6229307B2 - Inkjet head - Google Patents

Description

  The present invention relates to an ink jet head, and more particularly to an ink jet head that can suppress or reduce an increase in current density flowing in a common electrode.

  In Patent Document 1, the drive wall is shear-deformed by applying a voltage between a pair of electrodes formed on the drive wall that partitions the channel, and ink in the channel is ejected from the nozzle using the pressure generated at that time. There is disclosed a share mode type ink jet head that is made to operate, and an ink jet head that includes a so-called harmonica type head chip in which channel openings are respectively arranged on the front and rear surfaces (Patent Document 1).

JP 2008-143167 A

  FIG. 5 is a conceptual diagram illustrating a circuit configuration of an ink jet head according to the related art.

  In FIG. 5, A ′ is a discharge pressure applying means for applying a discharge pressure to ink, and is composed of a drive wall and a pair of electrodes sandwiching the drive wall.

  One of the pair of electrodes sandwiching the drive wall in the plurality of discharge pressure applying means A ′ is connected to the common electrode B ′, and the end of the common electrode B ′ is connected to the drive circuit C ′ by the wiring D ′. Is electrically connected.

  The other electrode of the pair of electrodes is individually electrically connected to the drive circuit C ′ via the wiring E ′ so that a plurality of drive walls can be individually driven.

  The common electrode B ′ is provided in the space between the channel rows on the rear surface of the head chip so as to extend along the channel row direction, but as the channel density increases, the distance between the channel rows becomes narrower. As the common electrode B ′ becomes thinner and the number of channels per channel column increases, the amount of current flowing through the common electrode B ′ increases. The increase in the current density at the common electrode B 'causes a delay in the rise time of the drive voltage when the drive voltage is applied to the one electrode constituting the discharge pressure applying means A'.

  By suppressing or reducing an increase in the current density flowing through the common electrode B ', effects such as preventing a delay in the rise time of the drive voltage and suitably preventing variations in the ejected droplet velocity are brought about.

  Accordingly, an object of the present invention is to provide an ink jet head capable of suppressing or reducing an increase in current density flowing in a common electrode.

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

  The above problems are solved by the following inventions.

1.
A plurality of ejection energy applying means for applying ejection energy to the ink using electrostatic capacitance formed between a pair of electrodes;
A common electrode in which one of the pair of electrodes included in each of the plurality of ejection energy applying means is connected to each other at intervals;
A drive circuit for generating a drive voltage applied between the pair of electrodes of the ejection energy applying means via the common electrode;
Have
Both ends of the common electrode are electrically connected to the same terminal of the drive circuit via mutually independent wirings ,
A product RC of a resistance R (Ω) when the drive voltage is simultaneously applied to all of the pair of electrodes and a total capacitance C (F) of the plurality of ejection energy applying means is 3.0. × ^{10 -7} ink jet head is characterized in der Rukoto below.
2.
The drive walls made up of channels and piezoelectric elements are alternately arranged side by side, the openings of the channels are arranged on the front and rear surfaces, drive electrodes are formed in the channels, and the channels perform ink ejection. Having a head chip in which channels and dummy channels that do not discharge ink are alternately arranged to form a channel row;
Each of the plurality of ejection energy applying means includes a capacitance formed between the pair of electrodes including the drive electrode in the ink channel and the drive electrode in the dummy channel adjacent to the ink channel. The drive wall is shear-deformed by using the ink, and the discharge energy for discharging from the nozzle to the ink in the ink channel is configured,
A plurality of the drive electrodes in the dummy channel of each of the plurality of ejection energy applying means are connected to the common electrode extending along the channel row direction on the front surface or the rear surface of the head chip at intervals. 2. The ink-jet head as described in 1 above.
3.
The inkjet head according to 1 or 2, wherein the RC is 1.5 × 10 ⁻⁷ or less.
4).
The inkjet head according to 1 or 2, wherein the RC is 1.0 × 10 ⁻⁷ or less.
5.
5. The inkjet head according to any one of 1 to 4, wherein a resistance between both ends of the common electrode is 1Ω or more.
6).
6. The inkjet head according to any one of 1 to 5, wherein the total of the ON resistance of the drive circuit and the wiring resistance from the drive circuit to connection to the common electrode is 0.1Ω or more.
7).
7. The inkjet head according to any one of 1 to 6, wherein the number of ejection energy applying units connected to the common electrode is 100 or more.
8).
The inkjet head according to any one of 1 to 7 above, wherein one of the ejection energy applying units has an electrostatic capacity of 500 pF or more.
9.
Together resistivity independent the wiring ink jet head according to any one of the 1 to 8, wherein the lower this than the resistivity across the common electrode.
10.
Each of the plurality of ejection energy applying means has an individual electrode wiring connected to the other electrode of the pair of electrodes, and the wirings independent of each other straddle across the individual electrode wiring 10. The ink jet head according to any one of 1 to 9 above.

  According to the present invention, it is possible to provide an ink jet head capable of suppressing or reducing an increase in current density flowing in a common electrode.

The conceptual diagram explaining the circuit structure in an example of the inkjet head which concerns on the 1st aspect of this invention. The exploded perspective view which looked at the head chip part in an example of the ink jet head concerning the 1st mode of the present invention from the back side. The figure which shows the result of the example The figure which shows the result of the example Conceptual diagram illustrating the circuit configuration of an inkjet head according to the prior art

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

<First aspect>
FIG. 1 is a conceptual diagram illustrating a circuit configuration in an example of an inkjet head according to the first aspect of the present invention.

  A is a discharge energy applying means, and has a function of applying discharge energy to the ink by using a capacitance formed between a pair of electrodes. As the discharge energy applying means A, a device provided with a piezoelectric element between a pair of electrodes can be preferably exemplified. The inkjet head has a plurality of nozzles for ejecting ink, and a plurality of ejection energy applying means A are provided corresponding to the plurality of nozzles. More specifically, the discharge energy applying means A has a function of applying discharge energy to the ink stored in the ink chamber individually provided for each nozzle.

  B is a common electrode, and one of a pair of electrodes included in each of the plurality of ejection energy applying means A is connected in a plurality at intervals. B1 and B2 are one end and the other end of the common electrode B. A plurality of the one electrodes are connected to the common electrode B between both ends B1 and B2 of the common electrode B.

  C is a drive circuit (also referred to as a waveform generation circuit), which applies a drive voltage (also referred to as a drive pulse) between a pair of electrodes of a plurality of ejection energy applying means A via a common electrode B, and has a capacitance. Has the function of charging or discharging the battery. Thereby, the discharge energy is applied to the ink by the discharge energy applying means A.

  In addition, the other electrode of the pair of electrodes included in each of the plurality of ejection energy applying units A is connected to the drive circuit C by the individual wiring E, and individually drives the plurality of ejection energy applying units A. Making it possible. That is, it is possible to individually eject ink from each nozzle included in the inkjet head.

  In the inkjet head of the present invention, both ends B1 and B2 of the common electrode B are electrically connected to the drive circuit C via wirings D1 and D2 that are independent of each other.

  Thereby, the effect which can suppress thru | or reduce the increase in the current density which flows into the common electrode B is acquired. For example, as the channel density in the inkjet head is increased, the distance between the channel rows is reduced, so that the common electrode B is formed thin or the number of channels per channel row is increased. By suppressing an increase in the current density at the common electrode B, an effect of preventing a delay in the rise time of the drive voltage when the drive voltage is applied between the pair of electrodes included in the ejection energy applying unit A can be obtained. . As a result, according to the present invention, even if the channel density is increased, the effect of preventing the disturbance of the droplet speed of the ejected ink can be obtained.

  In general, when the ink jet head meets one or more of the following conditions (a) to (d), the droplet velocity of the ejected ink may be easily disturbed. According to the first aspect, even in such a case, it is possible to prevent the droplet velocity of the ejected ink from being disturbed, and the significance of the present invention becomes remarkable. This is also common to the second mode described later.

  Condition (a): Resistance between both ends B1 and B2 of the common electrode B is 1Ω or more, and further 5Ω or more.

  Condition (b): The sum of the ON resistance of the drive circuit C and the wiring resistance from the drive circuit C to the connection to the common electrode B is 0.1Ω or more, and further 0.5Ω or more.

  Condition (c): The number of ejection energy applying means A connected to the common electrode B is 100 or more, and further 300 or more.

  Condition (d): Capacitance of one discharge energy applying means A is 500 pF or more, further 1500 pF or more.

  In the present invention, it is preferable that the resistivity of the wirings D1 and D2 independent from each other is lower than the resistivity between both ends B1 and B2 of the common electrode B. Furthermore, in the present invention, it is preferable that the resistances of the wirings D1 and D2 that are independent from each other are substantially the same.

  Hereinafter, as an example of the ink jet head according to the first aspect of the present invention, the drive wall is shear-deformed by applying a voltage between a pair of electrodes formed on the drive wall partitioning the channel, and the pressure generated at that time is A shear mode type ink jet head that discharges ink in a channel from a nozzle by using a nozzle, more specifically, a so-called harmonica type head chip in which channel openings are arranged on the front and rear surfaces, respectively. The present invention will be described in more detail by taking an inkjet head as an example.

  FIG. 2 is an exploded perspective view of the head chip portion in the example of the ink jet head according to the first aspect of the present invention as viewed from the rear side, and shows a state in which the head chip 1 and the wiring board 3 are developed left and right. ing.

  In the figure, 1 is a head chip, 2 is a nozzle plate bonded to the front surface of the head chip 1, 3 is a wiring substrate bonded to the rear surface 1b of the head chip 1, and 4 is bonded to the back side of the wiring substrate 3, A manifold member 5 for storing ink to be supplied to the head chip 1 through the substrate 3 is an FPC connected to the wiring substrate 3.

  In this specification, the surface on the side where ink is ejected from the head chip is referred to as the “front surface”, and the opposite surface is referred to as the “rear surface”. In addition, the outer surfaces located above and below in the figure across the channels arranged in parallel in the head chip are referred to as “upper surface” and “lower surface”, respectively.

  The head chip 1 is provided with a channel row in which drive walls 11 made of piezoelectric elements and channels 12 and 13 are alternately arranged. In this example, the channel string has seven channels 12 and 13, but the number of channels in the channel string is not limited.

  The head chip 1 is an independent channel type head chip in which a channel row includes an ink channel 12 that discharges ink every other channel and a dummy channel 13 that does not discharge ink. The shapes of the channels 12 and 13 are such that both side walls extend substantially perpendicular to the upper and lower surfaces of the head chip 1 and are parallel to each other.

  On the front surface and the rear surface 1b of the head chip 1, openings (not shown) on the front surface side of the channels 12 and 13 and openings 121 and 131 on the rear surface 1b side face each other. Each of the channels 12 and 13 is a straight type whose size and shape are not substantially changed in the length direction from the openings 121 and 131 on the rear surface 1b side to the openings on the front surface side. The opening 131 on the rear surface 1 b side of the dummy channel 13 is closed by the wiring board 3.

  A drive electrode 14 made of a metal film of Ni, Au, Cu, Al or the like is formed in close contact with the entire inner surface of each channel 12, 13.

  Further, on the rear surface 1b of the head chip 1, a linear common electrode 15 in which the drive electrodes 14 in all the dummy channels 13 of the channel row are electrically connected at a predetermined interval is orthogonal to the channel row. It is formed so as to be drawn upward in the direction (the vertical direction in the drawing) and extends along the channel row direction (the horizontal direction in the drawing).

  Further, on the rear surface 1 b of the head chip 1, a connection electrode 16 that is electrically connected to the drive electrode 14 in each ink channel 12 of the channel row is in the lower head of the drawing in the direction opposite to the direction in which the common electrode 15 is drawn. The chips 1 are individually drawn out toward the lower end of the rear surface 1b of the chip 1 and are arranged in parallel on the lower end side.

  A nozzle plate 2 is bonded to the front surface of the head chip 1. In the nozzle plate 2, nozzles 21 are opened only at positions corresponding to the ink channels 12. Accordingly, the opening (not shown) on the front side of each dummy channel 13 that does not eject ink is blocked by the nozzle plate 2.

  The wiring board 3 is formed of a flat plate-like substrate larger than the rear surface 1b of the head chip 1, and is bonded to the rear surface 1b of the head chip 1 with an adhesive. Here, it has a size that protrudes to the lower side of the figure than the head chip 1, and a connecting portion 31 with the FPC 5 is formed by the protruding portion.

  The substrate material used for the wiring board 3 is not particularly limited, and examples thereof include glass, silicon, ceramics, and plastic. Among them, it is preferable to use a glass substrate in that the dimensional change due to heat is small, it is relatively inexpensive and easy to process.

  In the wiring board 3, the ink in the common ink chamber 41 in the manifold member 4 is supplied to each ink channel 12 in the channel row at a position corresponding to the opening 122 of the ink channel 12 on the rear surface 1 b of the head chip 1. Ink supply ports 32 for the ink channels 12 are individually penetratingly formed. Each ink supply port 32 is formed in the same shape and size as the opening 121 of the ink channel 12.

  The manifold member 4 is formed in a box shape having a size that surrounds all the openings 121 of the ink channel channel 12 that opens on the rear surface 1b of the head chip 1, and is bonded to the back surface of the wiring board 3 with an adhesive. Yes. The inside of the manifold member 4 is a common ink chamber 41 in which ink that is commonly supplied to the ink channel 13 is stored. The ink in the common ink chamber 41 is passed through each ink supply port 32 of the wiring board 3. Each ink channel 12 is supplied.

  On the surface of the wiring substrate 3 on the side to which the head chip 1 is bonded, the individual electrode wiring 33 that is electrically connected to the connection electrode 16 provided for each ink channel 12 of the channel row of the head chip 1 on one end. Are individually formed by vapor deposition, sputtering, plating, or the like. One end of the individual electrode wiring 33 is disposed in the vicinity of the ink supply port 32, and the other end extends to the lower end of the wiring substrate 3 in the figure, and is arranged in the connection portion 31 with the FPC 5.

  Further, when the surface of the wiring substrate 3 is bonded to the rear surface 1 b of the head chip 1, the common electrode wiring 35 a connected to one end 15 a of the common electrode 15 and the other end 15 b of the common electrode 15 are electrically connected. And the common electrode wiring 35b connected to each other.

  One end of each of the common electrode wirings 35a and 35b which are independent from each other is disposed in the bonding region 30 with the head chip 1 to be electrically connected to the common electrode 15 on the rear surface 1b of the head chip 1, and the other end side is respectively After facing toward the lower end of the wiring board 3 in the figure, the common electrode wirings 35a and 35b are arranged in the connection portion 31 in a state where they are joined to one wiring 35c.

  In the illustrated example, the common electrode wiring 35 a is routed to the back surface (the surface on the side to which the head chip 1 is bonded) via the through hole 36 a provided in the wiring substrate 3, and is provided on the wiring substrate 3. After being pulled back to the surface of the wiring substrate 3 again through another through hole 36b and connected to the common electrode wiring 35b, one wiring 35c is formed. Thus, by drawing the common electrode wiring 35a to the back surface side of the wiring substrate 3, the common electrode wiring 35b can be joined across the individual electrode wiring 33 provided on the front surface side. When forming the wiring penetrating the wiring substrate 3 through the through holes 36a and 36b, for example, an evaporation method, a sputtering method, a plating method, or the like can be used. In particular, the combined use of the vapor deposition method and the electrolytic plating method, or the combined use of the sputtering method and the electrolytic plating method forms a metal film having a uniform thickness on the inner peripheral surface over the entire length of each through hole 36a, 36b. It is particularly preferable because it can be used.

  The FPC 5 is connected to the connection portion 31 of the wiring board 3 by an anisotropic conductive film or the like, and a drive signal of a predetermined voltage from a drive circuit (not shown) is sent to each of the individual electrode wirings 33 arranged in the connection portion 31. And the wiring 35c formed by joining the common electrode wirings 35a and 35b. The drive signal is applied between the drive electrode 14 in the dummy channel 13 and the drive electrode 14 in the ink channel 12 via each of the common electrode 15 and the connection electrode 16 of the head chip 1, Deform. A drive circuit (drive IC) may be mounted on the FPC 5.

  According to the present invention, the ends 15a and 15b of the common electrode 15 are thus connected to the same terminal of the drive circuit via the common electrode wirings 35a and 35b that are independent of each other, thereby flowing to the common electrode 15. An effect of suppressing or reducing an increase in current density can be obtained. As a result, as the channel density in the inkjet head is increased, the distance between the channel rows is reduced, so that the common electrode 15 can be formed thin or the number of channels per channel row can be increased. An increase in current density at the common electrode 15 is suppressed. Therefore, an effect of preventing a delay in the rise time of the drive voltage when the drive voltage is applied between the pair of drive electrodes 14 and 14 sandwiching the drive wall 12 made of a piezoelectric element can be obtained. As a result, according to the present invention, even if the channel density is increased, the effect of preventing the disturbance of the droplet speed of the ejected ink can be obtained.

  In the above example, when the both ends 15a and 15b of the common electrode 15 are electrically connected to the same terminal of the drive circuit via the mutually independent wirings, the common electrode wirings 35a and Although the case where 35b was joined was shown, it is not limited to this, Any method may be used.

  For example, the mutually independent wirings connected to both ends 15a and 15b of the common electrode 15 may be merged at the rear surface 1b of the head chip 1, or may be merged at the wiring board 3 as described above. You may make it merge in FPC5. In these cases, the merged wiring may be connected to the same terminal of the drive circuit. Or you may connect the mutually independent wiring connected to the both ends 15a and 15b of the common electrode 15 with the same terminal of a drive circuit directly.

  When the mutually independent wirings connected to both ends 15a and 15b of the common electrode 15 are joined in the FPC 5, as in the case of the wiring board 3 described above, through holes are provided in the FPC 5 and both sides of the FPC 5 are used. Thus, it is also preferable that the individual electrode wirings are joined together.

<Second aspect>
Next, the ink jet head according to the second aspect of the present invention will be described.

  An inkjet head according to a second aspect of the present invention includes a plurality of ejection energy applying units that apply ejection energy to ink using an electrostatic capacity formed between a pair of electrodes, and the plurality of ejection energy applying units. And a drive applied between the pair of electrodes of the ejection energy applying means via the common electrode, and a common electrode in which a plurality of one of the pair of electrodes included in each A driving circuit for generating a voltage.

According to a second aspect of the present invention, in the inkjet head having the above-described configuration, a resistance R (Ω) when the driving voltage is applied simultaneously to all of the pair of electrodes, and static electricity of the plurality of ejection energy applying means. The product RC of the total capacitance C (F) is 3.0 × 10 ⁻⁷ or less, preferably 1.5 × 10 ⁻⁷ or less, more preferably 1.0 × 10 ⁻⁷ or less. And

  As a result, an increase in the density of current flowing through the common electrode is suppressed, and a change in ejected droplet velocity can be prevented.

  The resistance R (Ω) can be calculated based on the ON resistance of the circuit, the wiring resistance connecting the drive circuit and the common electrode, and the resistance of the common electrode.

  The ink jet head according to the second aspect of the present invention is not limited to the one having the configuration of the first aspect described above. For convenience, the first mode is compared when the ON resistance of the circuit and the wiring resistance connecting the driving circuit and the common electrode are ignored and only the resistance of the common electrode whose resistance value is relatively easy is considered. Thus, both ends of the common electrode are electrically connected to the same terminal of the drive circuit via wirings independent of each other, so that only one end of the common electrode is connected to the drive circuit by wiring. Since RC can be significantly reduced (usually to about ¼), the RC condition according to the second aspect can be suitably achieved.

  As described above, in the description of the first aspect and the second aspect of the present invention, the case where the head chip mainly has one channel row has been described for convenience. However, the present invention is not limited to this, and in particular, The significance of the invention becomes more prominent when the head chip has a plurality of channel rows, preferably 4 rows or more, more preferably 6 rows or more. When the head chip has a plurality of channel rows, it is difficult to secure a sufficient space for forming the common electrode. In particular, when the common electrode is formed between the channel rows, the space restriction becomes large. According to the present invention, an increase in current density in the common electrode can be suppressed or reduced, and in such a case, particularly when a narrow common electrode must be provided in a limited space, Is preferred.

  In the above description, the share mode type inkjet head having the common electrode extending along the channel row direction on the rear surface 1b of the head chip is mainly taken as an example. However, the first aspect and the second aspect of the present invention are the same. However, the present invention can be suitably used for, for example, a share mode type ink jet head having a common electrode extending in the channel row direction on the front surface of the head chip.

  In addition, the first and second aspects of the present invention are not limited to the share mode type ink jet head, and use a capacitance formed between a pair of electrodes to impart ejection energy to the ink. A plurality of discharge energy applying means, a common electrode in which one of the pair of electrodes included in each of the plurality of discharge energy applying means is connected to each other at intervals, and the common electrode Any inkjet head having a drive circuit for generating a drive voltage applied between the pair of electrodes of the ejection energy applying means can be suitably applied.

  In the above description, the configuration described for one aspect can be applied to other aspects as appropriate.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

(Test 1)
As shown in FIG. 2, an inkjet head having the following specifications is prepared in which both ends of the common electrode are electrically connected to the same terminal of the drive circuit via mutually independent wirings, depending on the number of drive channels driven simultaneously. The change in discharge droplet velocity was measured. The ejection droplet velocity was measured for the nozzle of the ink channel (120th ink channel from the end) located in the center of the channel row.

<Inkjet head specifications>
・ Capacitance: 900pF / 1 ink channel ・ Number of ink channels: 256 / one channel row ・ Number of dummy channels: 257/1 channel row ・ ON resistance of drive circuit and drive circuit to connection to common electrode Total wiring resistance: 0.1Ω
-Resistance between both ends of the common electrode in the head chip: 3Ω

  The results are shown in FIG.

(Test 2)
In Test 1, the change in ejected droplet velocity with the number of drive channels driven simultaneously was measured in the same manner as in Test 1 except that only one end of the common electrode was electrically connected to the terminal of the drive circuit.

  The results are shown in FIG.

(Test 3; Reference Example)
In Test 2, the change in ejected droplet velocity due to the number of drive channels driven simultaneously is measured in the same manner as in Test 2, except that an inkjet head having the following specifications with a large common electrode formation width (line width) is used. did.

<Inkjet head specifications>
・ Capacitance: 900pF / 1 ink channel

-Number of ink channels: 256/1 channel row-Number of dummy channels: 257/1 channel row-ON resistance of drive circuit and total wiring resistance from drive circuit to common electrode: 0.1Ω
-Resistance between both ends of the common electrode in the head chip: 0.45Ω

  The results are shown in FIG.

<Evaluation>
In the case where the formation width (line width) of the common electrode is large (Test 3), the change in the ejection droplet speed due to the number of drive channels is relatively small, but the formation width (line width) of the common electrode is large. There is a problem in terms of increasing the density.

  On the other hand, when the formation width of the common electrode is narrowed (Test 2), it is sufficient from the viewpoint of increasing the channel density, but there arises a problem that the change in the ejection droplet speed due to the number of drive channels becomes large.

  On the other hand, in the test 1 according to the first aspect of the present invention, that is, when both ends of the common electrode are electrically connected to the same terminal of the drive circuit via independent wiring, the formation width of the common electrode It can be seen that the change in the ejected droplet velocity due to the number of drive channels is prevented as compared with Test 2 in which the same. That is, it can be seen that even if the channel density is increased, an increase in the current density flowing through the common electrode is suppressed, a delay in the rise time of the drive voltage can be prevented, and a disturbance in the droplet speed of the ejected ink can be prevented.

  Furthermore, simulation was performed based on the measurement data of Tests 1 to 3, and the relationship between RC and droplet velocity was derived (FIG. 4). In the graph shown in FIG. 4, the horizontal axis corresponds to the logarithm of RC.

As shown in FIG. 4, a common correlation (shown by a curve) was found between the RC and the ejection droplet velocity for the measurement data of tests 1 to 3. From this correlation, when ink is ^ejected under the condition that RC is 3.0 × 10 ⁻⁷ or less, preferably 1.5 × 10 ⁻⁷ or less, more preferably 1.0 × 10 ⁻⁷ or less, It can be seen that an increase in the density of the current flowing through the common electrode is suppressed, a delay in the rise time of the drive voltage is prevented (a speed ratio of 90% or more is suitably achieved), and a change in the discharge droplet speed can be prevented.

Therefore, the condition according to the second aspect of the present invention described above, that is, the sum of the resistance R (Ω) when the drive voltage is simultaneously applied to all of the pair of electrodes and the capacitance of the plurality of ejection energy applying means. If the product RC with C (F) satisfies the condition of 3.0 × 10 ⁻⁷ or less, preferably 1.5 × 10 ⁻⁷ or less, more preferably 1.0 × 10 ⁻⁷ or less, It can be seen that the delay of the rise time of the drive voltage can be prevented, and the disturbance of the discharge droplet speed can be prevented.

  Further, from the above results, RC is compared with the case of one-end connection (Test 2) by connecting both ends of the common electrode to the same terminal of the drive circuit via mutually independent wiring (Test 1). It can be seen that the above conditions can be suitably achieved.

A: Discharge energy applying means B: Common electrode B1: One end of the common electrode B2: Other end of the common electrode C: Drive circuit D1, D2: Wiring E: Wiring 1: Head chip 11: Drive wall (piezoelectric element)
12: Ink channel 13: Dummy channel 14: Drive electrode 15: Common electrode 15a: One end of the common electrode 15b: Other end of the common electrode 16: Connection electrode 2: Nozzle plate 21: Nozzle 3: Wiring board 30: Bonding region 31: Connection part 32: Ink supply port 33: Individual electrode wiring 35a, 35b: Common electrode wiring 35c: Wiring 36a, 35b: Through hole 4: Manifold member 41: Common ink chamber 5: FPC

Claims (10)

A plurality of ejection energy applying means for applying ejection energy to the ink using electrostatic capacitance formed between a pair of electrodes;
A common electrode in which one of the pair of electrodes included in each of the plurality of ejection energy applying means is connected to each other at intervals;
A drive circuit for generating a drive voltage applied between the pair of electrodes of the ejection energy applying means via the common electrode;
Have
Both ends of the common electrode are electrically connected to the same terminal of the drive circuit via mutually independent wirings ,
A product RC of a resistance R (Ω) when the drive voltage is simultaneously applied to all of the pair of electrodes and a total capacitance C (F) of the plurality of ejection energy applying means is 3.0. × ^{10 -7} ink jet head is characterized in der Rukoto below. The drive walls made up of channels and piezoelectric elements are alternately arranged side by side, the openings of the channels are arranged on the front and rear surfaces, drive electrodes are formed in the channels, and the channels perform ink ejection. Having a head chip in which channels and dummy channels that do not discharge ink are alternately arranged to form a channel row;
Each of the plurality of ejection energy applying means includes a capacitance formed between the pair of electrodes including the drive electrode in the ink channel and the drive electrode in the dummy channel adjacent to the ink channel. The drive wall is shear-deformed by using the ink, and the discharge energy for discharging from the nozzle to the ink in the ink channel is configured,
A plurality of the drive electrodes in the dummy channel of each of the plurality of ejection energy applying means are connected to the common electrode extending along the channel row direction on the front surface or the rear surface of the head chip at intervals. The ink-jet head according to claim 1. The RC is 1.5 × 10 ^-7 The inkjet head according to claim 1, wherein the inkjet head is as follows. The RC is 1.0 × 10 ^-7 The inkjet head according to claim 1, wherein the inkjet head is as follows. The inkjet head according to claim 1, wherein a resistance between both ends of the common electrode is 1Ω or more. The inkjet head according to claim 1, wherein the total of the ON resistance of the drive circuit and the wiring resistance from the drive circuit to connection to the common electrode is 0.1Ω or more. The inkjet head according to claim 1, wherein the number of ejection energy applying units connected to the common electrode is 100 or more. The inkjet head according to any one of claims 1 to 7, wherein one of the ejection energy applying units has a capacitance of 500 pF or more. The inkjet head according to claim 1, wherein resistivity of the wirings independent from each other is lower than resistivity between both ends of the common electrode. Each of the plurality of ejection energy applying means has an individual electrode wiring connected to the other electrode of the pair of electrodes, and the wirings independent of each other straddle across the individual electrode wiring The ink jet head according to claim 1, wherein the ink jet head is provided.

Images