JP2010143173A - Inkjet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording device, wherein an electrode in each air channel is easily formed and an improvement in productivity is attained. <P>SOLUTION: In the inkjet recording device, ink channels that jet ink and the air channels that do not jet ink are arranged to compose a series of channels so as to satisfy conditions (1) and (2) given below, and a driving waveform is applied to an electrode in each of the air channels separated from both sidewalls of each ink channel, thereby shearing and deforming the sidewalls and jetting the ink in the ink channels from a nozzle. (1) Air channels are arranged on both sides from the sidewall of the ink channel. (2) At least two air channels are arranged between the adjacent ink channels. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus.

  Today, it replaces conventional impact-type recording devices, and has the simplest principle among the non-impact-type recording devices that are expanding the market greatly, and is easy to achieve multi-gradation and colorization. As an example, an ink jet recording apparatus can be used. Among them, the drop-on-demand type that ejects only ink droplets used for printing is rapidly spreading due to its good ejection efficiency and low running cost.

  The drop-on-demand type is typically a Kaiser type or thermal jet type. Among these, the former is difficult to reduce in size, and the latter requires a heat resistance requirement for applying high heat to the ink, and each has a very difficult problem.

  The shear mode type disclosed in Patent Document 1 has been proposed as a new method for simultaneously solving the above defects.

  As shown in FIG. 12, the shear mode type ink ejecting apparatus 600 includes a bottom wall 601, a top wall 602, and a shear mode actuator wall 603 therebetween. The actuator wall 603 includes a lower wall 607 bonded to the bottom wall 601 and polarized in the direction of arrow 611 and an upper wall 605 bonded to the top wall 602 and polarized in the direction of arrow 609. A pair of actuator walls 603 forms an ink channel 613 therebetween, and an air channel 615 having a narrower space than the ink channel 613 is formed between the next pair of actuator walls 603.

  A nozzle plate 617 having a nozzle 618 is fixed to one end of each ink channel 613, and electrodes 619 and 621 are provided as metallization layers on both side surfaces of each actuator wall 603. Each electrode 619, 621 is covered with an insulating layer (not shown) for insulating from ink. The electrodes 619 and 621 facing the air channel 615 are connected to the ground 623, and the electrodes 619 and 621 provided in the ink channel 613 are connected to a silicon chip 625 that provides an actuator driving circuit. .

  Next, a method for manufacturing the ink ejecting apparatus 600 will be described. First, the piezoelectric ceramic layer polarized by the arrow 611 is bonded to the bottom wall 601, and the piezoelectric ceramic layer polarized by the arrow 609 is bonded to the top wall 602. The thickness of each piezoelectric ceramic layer is equal to the height of the lower wall 607 and the upper wall 605. Next, parallel grooves are formed in the piezoelectric ceramic layer by rotating a diamond cutting disk or the like to form a lower wall 607 and an upper wall 605. Then, an electrode 619 is formed on the side surface of the lower wall 607 by vacuum deposition, and the insulating layer is provided on the electrode 619. Similarly, the electrode 621 and the insulating layer are provided on the side surface of the upper wall 605.

  The ink channel 613 and the air channel 615 are formed by bonding the zenith portion of the upper wall 605 and the zenith portion of the lower wall 607. Next, the nozzle plate 617 in which the nozzle 618 is perforated is adhered to one end of the ink channel 613 and the air channel 615 so that the nozzle 618 corresponds to the ink channel 613, and the other of the ink channel 613 and the air channel 615 is connected. The ends are connected to silicon chip 625 and ground 623.

  Then, when the silicon chip 625 applies a voltage to the electrodes 619 and 621 of each ink channel 613, each actuator wall 603 is deformed by a piezoelectric thickness in the direction of increasing the volume of the ink channel 613, and the voltage is applied after a predetermined time. The application is stopped, the volume of the ink channel 613 is changed from the increased state to the natural state, pressure is applied to the ink in the ink channel 613, and ink droplets are ejected from the nozzles 618.

  However, in the ink ejecting apparatus 600 configured as described above, the electrodes 619 and 621 facing the air channel 615 are connected to the ground 623, and the electrodes 619 and 621 provided in the ink channel 613 serve as actuator driving circuits. Since it is connected to the silicon chip 625 to be applied, ink is ejected by applying a voltage to the electrodes 619 and 621 in each ink channel 613. For this reason, the electrodes 619 and 621 in the ink channel 613 must be covered with the insulating layer for insulating the ink. Without the insulating layer, if the ink is highly conductive, there is a possibility of short-circuiting. Even if the ink is not so highly conductive, the electrodes 619 and 621 are caused by electrical and chemical corrosion. As a result, the actuator wall 603 is not sufficiently deformed and the print quality is deteriorated. Therefore, the insulating layer for insulating the ink from the electrodes 619 and 621 is necessary, and facilities and processes for that purpose are required, resulting in a problem that productivity is lowered and cost is increased.

Therefore, as a technique for solving the above-described problems, the electrode in the ink channel is grounded, a voltage is applied to the electrode in the air channel, and the ink is ejected from the ink channel, whereby the ink and the electrode are separated. A technique that does not require insulation (see Patent Document 2) is known.
Japanese Patent Laid-Open No. 63-247051 Japanese Unexamined Patent Publication No. 7-132589

  However, in the case of a head in which ink channels and air channels are alternately arranged as disclosed in Patent Document 2, the electrodes on the wall surfaces of the channel walls on both sides of the air channel are divided in a fine channel, There is a problem that the process is complicated because it is necessary to make the electrodes individually.

  In this conventional head, an electrode film is formed only on the upper half of the channel wall on both sides of the air channel, and the oblique vapor deposition method is used. There was a problem that productivity was lowered.

  Accordingly, an object of the present invention is to provide an ink jet recording apparatus that can easily form an electrode in an air channel to which a driving waveform is applied and can improve productivity.

  The object of the present invention is achieved by the following configurations.

1. A plurality of channels partitioned at least partially by a side wall made of a piezoelectric material are arranged side by side, and an electrode is formed on the inner wall surface of the channel, and the channel performs ink ejection and ink ejection. A non-performing air channel is arranged so as to satisfy the following conditions (1) and (2) to form a channel row, and a drive waveform is applied to the electrodes in the air channel on both sides across the side wall of the ink channel. By doing so, the side wall is shear-deformed, and the ink in the ink channel is ejected from the nozzle.
(1) Air channels are arranged on both sides of the ink channel across the side wall (2) At least two air channels are arranged between adjacent ink channels. 2. The ink jet recording apparatus according to 1 above, wherein at least three air channels are arranged between adjacent ink channels.

  3. The ink channels are divided into N (N is an integer of 2 or more) groups so that the ink discharge timings of adjacent ink channels are not the same, and air on both sides separating the side walls of the ink channels for each group. 2. The ink jet recording apparatus according to 1 above, wherein a drive waveform is applied to an electrode in the channel.

  According to the present invention, it is possible to provide an ink jet recording apparatus capable of easily forming an electrode in an air channel to which a driving waveform is applied and improving productivity.

  Although the example of embodiment regarding this invention is shown below, the aspect of this invention is not limited to these.

  FIG. 1 is a schematic diagram showing a configuration of a line-type ink jet recording apparatus 1.

  The long recording medium 10 wound in a roll shape is fed out in the direction of arrow X from the unwinding roll 10A by a driving means (not shown) and conveyed.

  The long recording medium 10 is conveyed while being wound around and supported by a back roll 20. Ink is ejected from the inkjet head unit 30 toward the recording medium 10, and image formation based on the image data is performed. The inkjet head unit 30 includes a plurality of inkjet heads 31 corresponding to the ejection width in the recording medium width direction.

  Further, a drive signal generation unit 101 (see FIG. 5) provided for each inkjet head 31 is provided, and a control unit (not shown) controls the drive signal generation unit 101 and is common to each inkjet head 31. The drive waveform is output to the inkjet head 31, and ink droplets are ejected from the nozzles.

  FIG. 2 is an arrangement example of the inkjet head 31 of the inkjet head unit 30. Moreover, all the inkjet heads 31 are examples arranged at the same height with respect to the intermediate tank 40 that temporarily stores ink. As described above, since the ejection width that can be ejected by one inkjet head is narrower than the outer dimensions of the inkjet head, a plurality of inkjet heads are arranged in a staggered manner in the recording medium conveyance direction in order to eject without gaps. In the example shown in FIG. 2, a plurality of inkjet heads corresponding to the ejection width are arranged in two rows in a staggered manner in the recording medium width direction. FIG. 3 shows the relationship among the outer shape, the ejection width, and the staggered arrangement of the inkjet head 31. The number of the inkjet heads 31 and the number of rows in the staggered arrangement are appropriately set according to the ejection width of the inkjet head 31 and the like, and are not limited to the example of FIG.

  Ink is supplied to each inkjet head 31 through a plurality of ink tubes 43 from an intermediate tank 40 that adjusts the back pressure of ink in the inkjet head 31. In this description, the ink tube 43 in the figure is a plurality of ink tubes.

  Ink supply to the intermediate tank 40 is performed by a liquid feed pump P provided in the middle of the supply pipe 51 from the storage tank 50 for storing ink.

  The recording medium on which the image is formed is dried by the drying unit 100 and wound on the winding roll 10B.

  Next, the shear mode type inkjet head 31 will be described.

  Each inkjet head 31 is arranged so that the nozzle surface side faces the recording surface of the recording medium 10, and a drive signal generation unit 101 (FIG. 5) provided with a circuit for generating a drive waveform via the flexible cable 6. 5)).

  4A is a perspective view showing a partial cross section of the head chip portion of the shear mode type inkjet head 31, and FIG. 4B is a cross sectional view of the ink channel 28 as seen from the channel arrangement direction.

  In the figure, 310 is a head chip, and 22 is a nozzle forming member bonded to the front surface of the head chip 310.

  FIG. 5 is a cross-sectional view of the channel row as seen from the channel extending direction, and shows the positions of the nozzles provided corresponding to each ink channel for easy understanding.

  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 310 has a channel row in which a plurality of channels 28 and 128 separated by a side wall 27 are arranged in parallel. Here, the channel string is exemplified as having 19 channels 28 and 128, but the number of channels in the channel string is not limited at all.

  Each side wall 27 is composed of two piezoelectric materials 27 a and 27 b having different polarization directions as indicated by arrows in FIG. 5, but the piezoelectric material may be at least part of the side wall 27.

  As in this embodiment, when two sheets of piezoelectric material are bonded and used so that the polarization directions are opposite, the shear deformation amount is doubled compared to the case of one plate piezoelectric material, so the same deformation amount can be obtained. Has the advantage that the drive voltage is 1/2 or less.

The head chip 310 is configured by arranging a channel row in parallel so that an ink channel 28 that ejects ink and an air channel 128 that does not eject ink satisfy the following conditions (1) and (2). ing.
(1) Air channels 128 are disposed on both sides of the side wall 27 of the ink channel 28. (2) Two air channels 128 are disposed between adjacent ink channels 28. Ink at both ends of the channel row Three air channels 128 are arranged on both outer sides of the side wall 27 of the channel 28. The shape of each channel 28, 128 is such that both side walls extend substantially perpendicular to the upper and lower surfaces of the head chip 310 and are parallel to each other.

  On the front surface and the rear surface of the head chip 310, the opening on the front surface side and the opening on the rear surface side of each of the channels 28 and 128 face each other. Each of the channels 28 and 128 is a straight type whose size and shape are not substantially changed in the length direction from the opening on the rear surface side to the opening on the front surface side.

  As shown in FIG. 5, electrodes 29 made of a metal film such as Ni, Au, Cu, and Al are formed in close contact with the entire inner surfaces of the channels 28 and 128, respectively. An insulating protective film may be formed on the surface of the electrode 29 of the ink channel 28 that contacts the ink. As the protective film, an organic insulating film such as a parylene film is preferable. The electrodes 29 in the air channels 128 on both sides of each ink channel 28 are connected to the drive signal generator 101 via the first connection electrodes 301, respectively, and all the ink channels 28 and all but the sides of the ink channels 28 are all connected. The electrode 29 in the air channel 128 is grounded via the second connection electrode 300.

  A specific example of electrical connection will be described with reference to a cross-sectional view of the ink channel 28 viewed from the channel arrangement direction shown in FIG. Although not shown, the air channel 128 has the same electrical connection. On the lower surface of the head chip 310, the first connection electrode 301 corresponding to the electrode 29 in the air channel 128 on both sides of each ink channel 28 of the head chip 310 on the surface and all the ink channels 28 and both sides of the ink channels 28 are provided. The wiring substrate 102 in which the second connection electrodes 300 corresponding to the electrodes 29 in all the air channels 128 other than the other are formed in the same number and in parallel with the electrodes 29 of each channel, and the connection electrodes are the head chip 310. The electrodes 29 and the connection electrodes on the surface of the wiring substrate 102 are electrically connected across the front surface of the head chip 310 and the front end surface of the wiring substrate 102. The connection electrode is formed.

  The wiring substrate 102 is made of a substrate that is substantially the same width as the width of the head chip 310 (the length in the channel arrangement direction) and is sufficiently longer than the length of the head chip 310, and its front end surface is the head chip 310. The surface opposite to the connection electrode formation surface of the front surface is fixed to the lower surface of the head chip 310 so as to be flush with the front surface.

  By connecting the flexible cable 6 with the anisotropic conductive film 78 to the connection electrodes 300 and 301 of the wiring board 102, the drive waveform from the drive signal generation unit 101 is connected to the inkjet head 31. To each electrode 29 in the air channel 128 on both sides of each ink channel 28. In addition, the electrodes 29 in all the ink channels 28 and in all the air channels 128 other than both sides of the ink channel 28 are grounded via the second connection electrode 300.

  In this embodiment, as shown in FIG. 5, each electrode 29 in the air channel 128 on both sides of each ink channel 28 is connected to the drive signal generating unit 101 as a common electrode, and all the ink channels 28 and ink are connected. The electrodes 29 in all the air channels 128 except for both sides of the channel 28 are grounded as a common electrode.

  The flow path substrate 104 is substantially the same width as the head chip 310 and is slightly shorter than the wiring substrate 102, but is formed of a substrate that is sufficiently longer than the length of the head chip 310. The front end face is fixed to the upper surface of the head chip 310 so that it is flush with the front surface of the head chip 310.

  Thereby, the rear surface of the head chip 310 is covered with the wiring substrate 102 and the flow path substrate 104 protruding from the rear surface side of the head chip 310.

  The surrounding wall portion 103 is a side wall forming member having a substantially U shape in a plan view provided so as to surround the rear surface of the inkjet head 31 between the wiring substrate 102 and the flow path substrate 104, and is formed of polyimide, It is made of high-performance resin called engineering plastic such as polycarbonate. As a result, a space is formed on the rear surface side of the ink jet head 31 so that the upper and lower sides are covered by the flow path substrate 104 and the wiring substrate 102 and the side surfaces are enclosed by the wall portion 103. A common ink chamber 77 for supplying the ink is formed. Reference numeral 25 denotes an inlet for allowing ink to flow into the common ink chamber 77, whereby the common ink chamber 77 functions as an ink manifold. Although not shown, the common ink chamber 77 includes a filter in order to prevent inflow of dust.

  In addition, on the rear surface of the head chip 310, a flow path regulating member 302 that allows ink to flow into each ink channel 28 and regulates ink flow into each air channel 128 completely opens the opening on the rear surface side of each air channel 128. The flow path is regulated so as to prevent the inflow of ink into each air channel 128.

  The nozzle forming member 22 is bonded to the front surface of the head chip 310. In the nozzle forming member 22, nozzles 23 are opened only at positions corresponding to the respective ink channels 28. Accordingly, the opening on the front side of each air channel 128 that does not eject ink is blocked by the nozzle forming member 22.

  One end of the ink channel 28 (hereinafter sometimes referred to as a nozzle end) is connected to a nozzle 23 formed on the nozzle forming member 22, and the other end (hereinafter also referred to as a manifold end) is connected to a common ink chamber. 77, the ink supply port 25 is connected to the ink tube 43.

  Next, although the manufacture example of such an inkjet head 31 is demonstrated below, it is not limited to this at all.

  First, plate-like piezoelectric materials 27b and 27a made of PZT or the like that are polarized in the thickness direction are stacked so that the polarization directions are different from each other with the joint portion interposed therebetween, and are bonded using an epoxy adhesive. Further, a dry film is attached to the surface of the upper piezoelectric material substrate 27a.

  Next, from the dry film side, a plurality of parallel grooves to be the channels 28 and 128 are ground using a dicing blade or the like. Each groove is ground at a certain depth D (see FIG. 4) from one end of the piezoelectric materials 27a and 27b to the other end and to the middle of the lower piezoelectric material 27b. It is formed in a straight shape whose size and shape are almost the same in the length direction.

  Next, an electrode forming metal such as Ni, Au, Cu, and Al is applied by sputtering, vapor deposition, plating, or the like from the ground side of the groove, and is applied to the top surface of the remaining dry film and the inner surface of each groove. A metal film is formed.

  Thereafter, the dry film is removed together with the metal film formed on the surface thereof to obtain a substrate on which the metal film is formed only on the inner surface of each groove.

  Next, the cover plate 24 is bonded via an adhesive so as to cover each groove, and cut along a direction perpendicular to the length direction of the grooves, thereby making it possible to form a plurality of head chips 310 having channel rows at a time. create. Each groove serves as a channel 28 or 128, and the metal film in each groove serves as an electrode 29. Between adjacent grooves, a side wall 27 composed of piezoelectric materials 27a and 27b having different polarization directions with a joint portion interposed therebetween. The width between the cut lines determines the drive length (indicated by L in FIG. 4) of the ink channel 28 of the head chip 310 manufactured thereby, and is appropriately determined according to this drive length.

  Thereafter, after the head chip 310 and the wiring substrate 102 are fixed using an adhesive, a dry film is applied to the front surface of the head chip 310 and the front end surface and the surface of the wiring substrate 102 (the side opposite to the fixing surface of the head chip 310), for example. Each of the connection electrodes 300 and 301 electrically connected to the electrode 29 in each channel can be formed at a time by performing patterning using this and then depositing aluminum.

  The method for forming the Al film is not limited to vapor deposition, and a general thin film forming method can be employed. Moreover, the method of apply | coating an electrically conductive paste with an inkjet can also be used. After the Al film is formed, the dry film is dissolved and peeled off with a solvent to remove the Al film formed on the dry film, and the second connection is made to the front surface of the head chip 310 and the front end surface and the surface of the wiring substrate 102. Only the electrode 300 and the first connection electrode 301 remain.

  Then, a flow path regulating member 302 that regulates ink inflow into each air channel 128 is bonded to the rear surface of the head chip 310 so as to completely close the opening on the rear surface side of each air channel 128.

  Thereafter, the flow path substrate 104 is fixed. Thereafter, a common ink chamber 77 is formed by fixing the surrounding wall portion 103 so as to surround the rear surface of the head chip 310 between the wiring substrate 102 and the flow path substrate 104. Thereafter, the flexible cable 6 is bonded to the connection electrodes 300 and 301 of the wiring board 102.

  Next, the single nozzle forming member 22 provided with the nozzle 23 is bonded via an adhesive.

  In addition, as a material for the nozzle forming member 22, a synthetic resin such as a polyimide resin, a polyethylene terephthalate resin, a liquid crystal polymer, an aromatic polyamide resin, a polyethylene naphthalate resin, a polysulfone resin, or a metal material such as stainless steel can be used. .

  As described above, according to the ink jet head 31 of the present embodiment, since the two air channels 128 are arranged between the adjacent ink channels 28, the electrode in the air channel 128 can be formed on the entire surface of the inner wall of the channel. It becomes possible.

  For this reason, it is not necessary to limit the electrode formation position to the upper half of the channel wall as in the prior art, so that it is not necessary to perform evaporation twice in different directions.

  That is, it can be formed on the entire inner wall of the channel by a single vapor deposition and sputtering, and since an electroless plating method or the like can be used as a method for forming an electrode, it becomes easy to form an electrode in the air channel, Productivity can be improved. In particular, the electroless plating method is preferable because an electrode can be formed on the entire surface of the groove even if there are large irregularities in the groove.

  In the present embodiment, the connection electrodes of the wiring board 102 are used to electrically connect the electrodes 29 in the air channels 128 on both sides of each ink channel 128 and the wiring from the drive signal generation unit 101, and to each ink channel 28. Production that can easily perform electrical connection between the electrode 29 in the other air channel 128 and the ground, and can easily form a common ink chamber for supplying ink into each ink channel 28. An ink jet head with high performance can be provided.

  On the other hand, in the case of a head in which ink channels and air channels are alternately arranged in parallel, the electrodes on the wall surfaces of the channel walls on both sides of the air channel are divided into fine channels and separated into individual electrodes. Thus, since the wiring for connecting to the drive signal generator must be provided, the structure becomes complicated.

  Next, the operation principle when ejecting ink droplets from the nozzle 23 of the ink channel 28 will be described.

  FIGS. 6A to 6C are diagrams showing the operation, and are cross-sectional views of the inkjet head 31 as viewed from the extending direction of the channel. In FIG. 6, five of 19 channels 28 and 128 are shown.

  When the drive waveform shown in FIG. 7 is applied from the drive signal generator 101 to the electrodes 29A and 29C formed in close contact with the inner surfaces of the air channels 128 on both sides of the central ink channel 28, and all the other electrodes 29 are grounded, Ink droplets are ejected from the nozzles 23 by the operation exemplified below.

  (1) In the state shown in FIG. 6A, the ink jet head 31 grounds the electrode 29B and applies an expansion pulse (positive voltage) made of a rectangular wave with a pulse width of 1AL to the electrodes 29A and 29C. First, an electric field in a direction perpendicular to the polarization direction of the piezoelectric materials 27a and 27b constituting the side walls 27B and 27C is generated by the first rising edge (P1) of the pulse, and both 27a and 27b cause a shear deformation on the bonding surface of the side walls. As shown in FIG. 6B, the side wall 27B and the side wall 27C are deformed outward from each other, and the volume of the ink channel 28 is expanded. As a result, a negative pressure is generated in the ink in the ink channel 28 and the ink flows (Draw). At this time, the upper and lower wall portions of the ink channel 28 are contracted, but the side walls 27A and 27D of the air chamber 128 on both sides of the ink channel 28 are also deformed as shown, and the upper and lower wall portions of the air chamber 128 are extended. Therefore, the driving voltage can be lowered by assisting the shrinkage of the upper and lower wall portions of the ink channel 28. This will be described in detail.

  When a drive waveform is applied to the air channel 128 on both sides of the ink channel 28, if a similar drive waveform is applied to the air channel 128 adjacent to the air channel 128, a potential difference is applied to the electrodes on both sides of the side wall 27A or 27D. Therefore, the electric field is not applied and the side wall 27A or 27D is not deformed.

  In contrast, as shown in FIG. 6B, when a driving waveform is applied to the air channels 128 on both sides of the ink channel 28, when the air channel 128 adjacent to the air channel 128 is grounded, the side wall 27A. Alternatively, a potential difference is generated between the electrodes on both sides of 27D, an electric field is applied in a direction orthogonal to the polarization direction of the side wall, and the side wall 27A or 27D is deformed. The expansion of the upper and lower wall portions of the air chamber 128 caused by this deformation assists the shrinkage of the upper and lower wall portions of the ink channel 28, so that the volume displacement of the ink channel 28 increases and the ink droplets are ejected from the nozzles. Since the pressure change becomes large, the driving voltage can be lowered.

  As described above, in the ink jet head of this embodiment, when the air channel adjacent to the air channel on both sides of the ink channel is grounded, the driving voltage when ejecting ink droplets from the ink channel can be reduced.

  (2) When the potential is returned to 0 after 1 AL time has elapsed since the first application of P1 (P2), the side walls 27B and 27C return from the expanded position to the neutral position shown in FIG. High pressure is applied.

  Subsequently, a contraction pulse (negative voltage) having a pulse width of 2AL made of a rectangular wave is applied. First, as shown in FIG. 6C, the side walls 27B and 27C are deformed in opposite directions due to the fall of the contraction pulse (P3), and the volume of the ink channel 28 contracts. Due to this contraction, a higher pressure is applied to the ink in the ink channel 28 (Reinforce). As a result, the ink meniscus in the nozzle changes in the direction in which it is pushed out from the nozzle 23. When this positive pressure increases as the ink droplets are ejected from the nozzles, the ink droplets are ejected from the nozzles. At this time, the upper and lower wall portions of the ink channel 28 extend, but the side walls 27A and 27D of the air chamber 128 on both sides of the ink channel 28 are also deformed as shown, and the upper and lower wall portions of the air chamber 128 contract. Therefore, the driving voltage can be lowered by assisting the extension of the upper and lower wall portions of the ink channel 28.

  (3) Further, when 2AL time elapses, the potential is returned to 0 (P4), and the side walls 27B and 27C are returned from the contracted position to the neutral position.

  Through a series of these operations, a part of the ink in the ink channel 28 flies from the nozzle 23 as an ink droplet.

  Such a droplet discharge method is a droplet discharge method based on a so-called DRR (Draw-Release-Reinforce) method, and the pulse width of the expansion pulse greatly affects the discharge force of the ink droplet, and this pulse width is in the vicinity of 1AL. When they coincide, the ink droplet ejection force (ejection speed) becomes maximum.

  Note that AL (Acoustic Length) is ½ of the acoustic resonance period of the ink channel, as described above. This AL measured the speed of ink droplets ejected by applying a rectangular wave pulse to the side wall 27, which is an electrical / mechanical conversion means, and changed the rectangular wave pulse width while keeping the rectangular wave voltage value constant. Sometimes it is determined as the pulse width that maximizes the flying speed of the ink droplets. The value of AL is determined depending on the structure of the head, the ink density, and the like.

  A pulse is a rectangular wave having a constant voltage peak value. When 0V is 0% and a peak voltage is 100%, the pulse width is the start of rising or falling of the voltage from 0V. Is defined as the time between 10% of 10% and 10% of the start of falling from the peak voltage or 10% of rising. Furthermore, the rectangular wave here refers to a waveform in which both the rise time and fall time between 10% and 90% of the voltage are within ½ of AL, preferably within ¼. .

  It is preferable to use a rectangular wave as the driving waveform because the ejection efficiency is improved and the pulse width can be easily set.

  In the drive waveform of FIG. 7, it is preferable that the ratio of the drive voltage Von (V) of the expansion pulse and the drive voltage Voff (V) of the contraction pulse is | Von |> | Voff |. Thus, the relationship | Von |> | Voff | has an effect of promoting the supply of ink into the ink channel, and is particularly preferable when high-frequency driving is performed with high-viscosity ink. Note that the reference voltage of the voltage Von and the voltage Voff is not always zero. The voltage Von and the voltage Voff are respectively differential voltages from the reference voltage. Further, it is more preferable that | Von | / | Voff | = 2.

  As described above, in the inkjet head of this embodiment in which the two air channels 128 are provided between the adjacent ink channels 28, when the air channels 128 adjacent to the air channels 128 on both sides of the ink channel 28 are grounded, The drive voltage when ejecting ink droplets from the ink channel 28 can be reduced.

  In this ink jet head, as shown in FIG. 5, when adjacent ink channels are driven simultaneously, the driving waveform is applied to the air channels 128 adjacent to the air channels 128 on both sides of the ink channel 28 without being grounded. The assist effect cannot be obtained and the drive voltage cannot be reduced.

  In order to compensate for this, the ink discharge timings of adjacent ink channels 28 are divided into N groups (N is an integer of 2 or more) so that the side walls of the ink channels 28 are separated for each group. A drive waveform is preferably applied to the electrodes 29 in the air channels 128 on both sides.

  Among the plurality of ink channels 28, the ink channels 28 that are separated from each other with one or more ink channels 28 are grouped together into one group, and divided into two or more groups. Drive control is performed so that the ink ejection operation is sequentially performed in a time-sharing manner.

  For example, a two-cycle ejection method is performed in which all the ink channels 28 are selected every other channel and ejected in two groups.

  In the present embodiment, channel numbers 28-1, 28-2, 28-3, 28 are sequentially applied from the ink channel at one end to the ink channel at the other end for the five ink channels shown in FIG. -4, 28-5, all ink channels are divided into two groups with channel numbers 28-1, 28-3, 28-5 as group A and channel numbers 28-2, 28-4 as group B. Divided drive.

  FIG. 8 shows a timing chart of drive waveforms applied to the air channel electrodes on both sides of the ink channels 28 of each group A and B when the two-cycle discharge operation is driven with the drive waveforms of FIG.

  At the time of ink discharge, first, the drive waveform of FIG. 7 is applied to the air channel electrodes on both sides of each ink channel of group A, and all the other channel electrodes are grounded, and ink is ejected from the nozzles of each ink channel of group A. Let the drops be ejected.

  Subsequently, the same operation as described above is performed for each channel 28 of the group B. Image formation is performed by repeating the ink ejection operation performed in the order of the A group and the B group while transporting the recording medium.

  Of course, in the driving method shown in FIG. 8, when an image is actually formed, the driving waveform is not always applied to the air channels on both sides of all the ink channels as described above, and the driving is not performed according to the image data. There is also an ink channel.

  Next, an example of a three-cycle discharge method in which the ink channels 28 are selected every two channels and discharged in three groups will be described.

  In the present embodiment, among the five ink channels shown in FIG. 5, all ink channels are grouped as channel numbers 28-1 and 28-4, group A, channel numbers 28-2 and 28-5 as group B, and channel number 28. -3 is divided into three groups as a C group and is divided and driven.

  FIG. 9 shows a timing chart of the drive waveforms applied to the air channel electrodes on both sides of the ink channels 28 of each group A, B, and C when the three-cycle ejection operation is driven with the drive waveforms of FIG.

  At the time of ink ejection, first, the drive waveform of FIG. Let the drops be ejected.

  Subsequently, the operation is performed in the same manner as described above for each channel 28 of the B group, and further to each channel 28 of the C group.

As described above, the ink discharge timings of adjacent ink channels 28 are divided into N groups (N is an integer of 2 or more) so that the ink discharge timings are not the same, and both sides of the ink channel 28 are separated from each other. By applying a drive waveform to the electrode 29 in the air channel 128, when the ink is ejected from a certain ink channel, the drive voltage is lowered by the aforementioned assist effect regardless of whether or not the adjacent ink channel ejects ink. Can be made.
<Other embodiments>
In the above embodiment, two air channels 128 are arranged between adjacent ink channels 28. However, in this embodiment, three air channels 128 are arranged between adjacent ink channels 28. Except for this point, the configuration and discharge operation of the apparatus are the same as those in the above embodiment, and thus detailed description thereof is omitted.

  FIG. 10 is a cross-sectional view of a channel row in which three air channels 128 are disposed between adjacent ink channels 28. In addition, the same code | symbol is attached | subjected and demonstrated about the same structure as said embodiment.

  As shown in FIG. 10, by grounding the central air channel among the three air channels, when ink is ejected from a certain ink channel, the above-mentioned ink channel is ejected regardless of whether ink is ejected or not. The driving voltage can be reduced by the assist effect. Moreover, since the central air channel is always grounded, all ink channels can be driven simultaneously.

  As described above, the ink jet recording apparatus according to the present invention is characterized in that at least two air channels 128 are arranged between adjacent ink channels 28. For example, in the above-described embodiment, when the driving voltage is lowered due to the assist effect, the adjacent ink channels 28 cannot perform the ink ejection operation at the same time, and it is necessary to perform the ink ejection operation in a time division manner. In the embodiment, all the ink channels 28 can perform the ink ejection operation simultaneously, and the recording time can be shortened.

  In the above embodiment, the first piezoelectric material 27a and the second piezoelectric material 27b that are polarized in the thickness direction are stacked and then the groove is formed. In the present embodiment, the thickness direction is used. The flat plate-shaped first piezoelectric material 27a and the second piezoelectric material 27b that are polarized to each other are each formed with a groove and then bonded. Except for this point, the configuration and discharge operation of the apparatus are as described above. Since this is the same as the embodiment, detailed description is omitted.

  FIG. 11 is a cross-sectional view of a channel array of heads bonded to each other after grooves are formed in the first piezoelectric material 27a and the second piezoelectric material 27b that are polarized in the thickness direction. In addition, the same code | symbol is attached | subjected and demonstrated about the same structure as said embodiment.

  A plate-like first piezoelectric material 27a and a second piezoelectric material 27b polarized in the thickness direction are prepared, and a plurality of grooves that become ink channels 28 and dummy channels 128 are straightly parallel by diamond blades or the like, respectively. To be cut.

  The second piezoelectric material 27a and the first piezoelectric material 27b in which the metal electrode 29 is provided in the groove are fixed so that the surfaces of the substrates on which the groove is formed face each other. Here, they are aligned and fixed so that the grooves of each substrate face each other. For example, an adhesion method using an epoxy-based adhesive can be usually used as the fixing means, but in this aspect, there is no particular limitation as long as the metal electrodes in the grooves of the aligned substrates are electrically connected.

  In the above embodiment, the case where the present invention is applied to the line type ink jet recording apparatus 1 has been described. The present invention is not limited to this, and can be applied to other ink jet recording apparatuses.

It is a schematic diagram which shows the structure of a line type inkjet recording device. It is a figure which shows the example of arrangement | positioning of an inkjet head. It is a figure which shows the positional relationship of zigzag arrangement | positioning of an inkjet head. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows schematic structure of the shear mode (shear mode) type inkjet head which concerns on embodiment, (a) is a perspective view which shows a partial cross section, (b) is sectional drawing of the state provided with the ink supply part It is. It is sectional drawing of the channel row which concerns on embodiment. (A)-(c) is a figure which shows operation | movement of a head. It is a figure which shows the example of a drive waveform. 6 is a timing chart of driving waveforms applied to the air channel electrodes on both sides of the ink channels of each group of A and B in the two-cycle driving of the head. 6 is a timing chart of driving waveforms applied to the air channel electrodes on both sides of the ink channels of each group of A, B, and C in the three-cycle driving of the head. It is sectional drawing of the channel row which concerns on other embodiment. It is sectional drawing of the channel row which concerns on other embodiment. It is explanatory drawing which shows the ink ejection apparatus of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 10 Recording medium 10A Unwinding roll 10B Winding roll 20 Back roll 30 Inkjet head unit 31 Inkjet head

Claims (3)

A plurality of channels partitioned at least partially by a side wall made of a piezoelectric material are arranged side by side, and an electrode is formed on the inner wall surface of the channel, and the channel performs ink ejection and ink ejection. A non-performing air channel is arranged so as to satisfy the following conditions (1) and (2) to form a channel row, and a drive waveform is applied to the electrodes in the air channel on both sides across the side wall of the ink channel. By doing so, the side wall is shear-deformed, and the ink in the ink channel is ejected from the nozzle.
(1) Air channels are arranged on both sides of the ink channel across the side wall (2) At least two air channels are arranged between adjacent ink channels 2. The ink jet recording apparatus according to claim 1, wherein at least three air channels are disposed between adjacent ink channels. The ink channels are divided into N (N is an integer of 2 or more) groups so that the ink discharge timings of adjacent ink channels are not the same, and air on both sides separating the side walls of the ink channels for each group. The ink jet recording apparatus according to claim 1, wherein a driving waveform is applied to an electrode in the channel.

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