JP2016060114A - Ink jet head, ink jet recording device using the former, and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet head capable of homogenizing an ink density in a pressure chamber entirety for discharging ink containing pigment particles.SOLUTION: Conductive layers (an electrode U4 and an electrode L5) are individually formed on the face of the side of a pressure chamber 12 of a nozzle substrate 1 having a plurality of nozzle holes for discharging ink, and on the face of the opposite side. Between these electrodes, there are applied potential differences having controlled an electrification start, an electrification end and a weld time thereby to establish an electrophoresis phenomenon in the pressure chamber 12. This electrophoresis phenomenon performs a control to float ink particle components (pigment fine particles) which might otherwise precipitate on the bottom face of the pressure chamber 12. The pigment fine particles repeat the actions to precipitate and float thereby to move up and down in the pressure chamber 12 so that the ink is agitated.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ink jet head mounted on an ink jet recording apparatus such as a printer that ejects ink droplets to form an ink image on a recording medium, and also relates to an ink jet recording apparatus and an image forming apparatus using the ink jet head.

In the ink jet head, there are a common liquid chamber (ink reservoir, reservoir), an ink supply path, and an individual liquid chamber (pressure chamber). The following means have been proposed as means for stirring ink filled in them.
(1) The ink is agitated by a physical action such as a carriage operation of the inkjet head.
(2) A pressure difference is generated in the ink jet head connected to the ink supply unit (ink tank) to stir the ink in the common liquid chamber.
(3) Stir the ink in the pressure chamber by driving the vibration to such an extent that ink ejection does not occur.
(4) Stir while discharging the ink in the pressure chamber by vibrating the actuator by capping the nozzle surface of the inkjet head.

  In addition, as a conventional technique related to stirring of the common liquid chamber ink flow path by utilizing electric action, Patent Document 1 provides a segment electrode on the flow path substrate, and stirs the pigment ink in the common liquid chamber by electrophoresis. Are disclosed. Patent Document 2 discloses a technique in which a flexible perforated plate in contact with a diaphragm is provided and stirring is performed using a deformation difference between the diaphragm and the perforated plate. In Patent Document 3, the periphery of the nozzle of the nozzle plate is used as an electrode, the second plate constituting the wall of the pressure chamber is used as the other electrode, and charged ink particle components in ink are attracted to the vicinity of the nozzle by electrophoresis. Is disclosed. Patent Document 3 also relates to a technique for increasing the ink density in the vicinity of the nozzles using an electrical action.

  By the way, the pigment-dispersed ink (pigment ink) that may be used in the ink jet head as described above is obtained by dispersing fine particles of a pigment having an advantage such as being difficult to fade as a coloring material in an ink solvent. In this pigment-dispersed ink (pigment ink), fine particles of the pigment settle and precipitate and aggregate when left standing for a long time. If the ink in which precipitation / aggregation has occurred is ejected as it is, it may cause ejection instability such as nozzle clogging. In addition, the ink image formed on the recording medium is distorted and density unevenness is caused.

  It is clear that troubles such as nozzle clogging are largely due to pigment fine particles precipitated and aggregated in the vicinity of the nozzle. For this purpose, it is necessary to efficiently stir the ink in the pressure chamber.

  Patent Document 1 is intended to move and circulate the pigment ink precipitated in the common ink chamber of the inkjet head in the horizontal direction by electrophoresis, and has a sufficient stirring effect on the pigment fine particles precipitated in the pressure chamber. There is a possibility that it cannot be obtained. Further, in Patent Document 2, there is a possibility that an effect as expected is not obtained unless the difference in deformation amount between the diaphragm and the perforated plate is large. Further, Patent Document 3 aims to make the ink density uniform with respect to the ink in the vicinity of the nozzles, and causes a local ink stirring action, but does not reach the entire pressure chamber.

  The present invention has been made in view of the above-described conventional problems, and pigment fine particles can be quickly dispersed in a solvent, and can be stirred with respect to the ink in the entire pressure chamber including the vicinity of the nozzle. An object of the present invention is to provide an ink jet head capable of making the ink density uniform throughout the pressure chamber, and an ink jet recording apparatus using the ink jet head.

  An inkjet head according to the present invention includes a nozzle substrate having a plurality of nozzle holes for discharging ink, a pressure chamber communicating with the nozzle holes, and a piezoelectric element actuator for generating a pressure for discharging the ink liquid filled in the pressure chamber. And a diaphragm that is bonded to the piezoelectric element actuator and propagates pressure to the pressure chamber, and a voltage applying means that applies a voltage to the piezoelectric element actuator, and has a charge such as pigment dispersion ink. In an ink jet head that discharges ink liquid containing ink particle components from the nozzle holes, a conductive layer serving as an electrode is provided on the surface of the nozzle substrate on the pressure chamber side and on the surface of the diaphragm opposite to the pressure chamber. Each of these conductive layers is formed, and a potential difference is applied between these conductive layers to control energization start, energization end, energization time, etc. To generate electrophoresis phenomenon, characterized by having a control means to float the ink particles components to be settled to the bottom of the pressure chamber by the electrophoretic phenomenon.

  According to the present invention, the pigment fine particles can be rapidly dispersed in the solvent by causing the settled pigment fine particles to swing up and down by electrophoresis. Further, since the electrode is provided on the entire surface of the nozzle plate, the ink in the entire pressure chamber including the vicinity of the nozzle can be agitated. As a result, the ink density in the entire pressure chamber can be made uniform.

It is a conceptual sectional view showing the composition of Embodiment 1 of the present invention. FIG. 2 is an enlarged cross-sectional view cut out from FIG. 1 for explaining the operation of the first embodiment. FIG. 3 is a cross-sectional view in which a main part is enlarged from FIG. 2 in order to explain the operation of the first embodiment. FIG. 3 is a conceptual cross-sectional view corresponding to FIG. It is the typical sectional view showing the example applied to the head of a thin film type piezo system. It is typical sectional drawing which looked at FIG. 5 from the side. It is a perspective explanatory view of an ink jet recording apparatus. It is a side view for demonstrating the mechanism part of the inkjet recording device shown in FIG.

Embodiments of the present invention will be described with reference to the drawings.
<Embodiment 1>
FIG. 1 is a conceptual cross-sectional view showing the configuration of Embodiment 1 of the present invention.
In the figure, 1 is a nozzle substrate, and 2 is a liquid chamber substrate (support plate). For example, both the nozzle substrate 1 and the liquid chamber substrate 2 are made of Si. A nozzle 3 is formed on the nozzle substrate 1. The electrode U (4) and the electrode L (5) are made of a conductive material such as a conductive thin film. The diaphragm 6 is made of metal or nonmetal, and the piezoelectric element actuator 7 is made of PZT (lead zirconate titanate). Further, the FPC 8 is a flexible printed circuit board, the base material 9 is SUS (stainless steel material), and the frame 10 is made of epoxy resin. In the figure, 11 is a drive circuit, and 12 is a pressure chamber.

FIG. 2 is an enlarged cross-sectional view cut out from FIG. 1 for explaining the operation of the first embodiment.
The surface of the pigment fine particles Pp is positively or negatively charged by a dispersant (not shown). When a voltage is applied between the electrode U (4) and the electrode L (5), the pigment fine particle Pp attracts the opposite electrode to the charge charged on the surface and repels the same electrode as the charged charge. . Therefore, electrophoresis occurs in the pressure chamber 12, and the pigment fine particles Pp move up and down. Then, as shown by arrows in FIG. 2, when the polarities are alternately switched so that the polarities of the electrodes U (4) and L (5) are opposite, the direction of electrophoresis acting on the pigment fine particles Pp is changed. change.

FIG. 3 is a cross-sectional view in which the main part is enlarged from FIG. 2 in order to explain the operation of the first embodiment.
In the ink jet head that has been allowed to stand for a long time, the components of the pigment fine particles Pp of the ink liquid that fills the pressure chamber settle and settle on the nozzle substrate 1. If ink is ejected while the pigment fine particles Pp are precipitated, the nozzle 3 is clogged, the ink image is distorted, and density unevenness occurs. For example, if pigment fine particles Pp whose surface is negatively charged are included in the ink, when the electrode U (4) is positive (the electrode L is negative), it moves toward the electrode U (5) by electrophoresis. . Conversely, when the electrode U (4) is negative (the electrode L is positive), it moves toward the electrode L (5) by electrophoresis (and gravity).

Here, the polarity of the voltage applied to the electrodes U (4) and L (5) and the charging time are controlled by the drive circuit 11, and the pigment fine particles Pp are swung in the pressure chamber 12 to stir the ink. To do.
First, in order to raise the pigment fine particles Pp that have precipitated, a force is generated to attract the electrode U (4) and the pigment fine particles Pp (or to repel the electrode L (5) and the pigment fine particles Pp). For this purpose, as shown in FIG. 3A, a voltage pulse with the electrode U (4) positive and the electrode L (5) negative is sent from the drive circuit 11, and the electrode U (4) and electrode L (5) are sent. ) To generate a potential difference. Then, the pigment fine particles Pp move toward the electrode U (4) by electrophoresis. However, if electricity is applied for a long time with the same polarity, the pigment fine particles Pp reach the electrode U (4) and aggregate.

  Therefore, next, as shown in FIG. 3B, a voltage pulse is sent from the drive circuit 11 to make the electrode U (4) negative and the electrode L (5) positive to send the electrode U (4) and the electrode L ( A potential difference is generated during 5). Then, the pigment fine particles move toward the electrode L (5) by electrophoresis and gravity. This prevents the pigment fine particles Pp from reaching the electrode U (4) and aggregating. That is, by controlling the polarity and time of the voltage pulse by the drive circuit 11 itself or a control means such as its control device (a known means such as a microcomputer can be adopted) and repeating the above-described operation, the pigment fine particles Pp move up and down. And the ink is agitated.

  Although the electrode U (4) is joined to the diaphragm 6, no action is generated to move the diaphragm 6. Therefore, the influence on the diaphragm 6 and the piezoelectric element actuator 7 joined to the diaphragm 6 is not affected. Very small.

  These operations are performed in a preparation stage before ink is ejected from the nozzle 3. This is because new ink is supplied from an ink supply unit (not shown) to the pressure chamber 12 which is decompressed by ejecting ink from the nozzle 3, and the pigment fine particles Pp move without being settled by the ink flow. Because.

  As described above, the pigment fine particles Pp are rapidly dispersed in the solvent by causing the settled pigment fine particles Pp to swing up and down by electrophoresis. Further, by providing electrodes on the entire surface of the nozzle substrate 1, the ink in the entire pressure chamber 12 including the vicinity of the nozzle 3 can be agitated. As a result, the ink density of the entire pressure chamber 12 can be made uniform.

<Embodiment 2>
FIG. 4 is a conceptual cross-sectional view corresponding to FIG. 1 showing the configuration of the second embodiment of the present invention. Components that are the same as or in common with the embodiment of FIG.
In this embodiment, for example, the diaphragm 6 is a conductor such as Ni, and the diaphragm 6 is used as it is as an alternative to the electrode U (4). Since the diaphragm 6 is not driven in the same manner as when the electrode U (4) is charged in the first embodiment, the influence on the diaphragm 6 and the piezoelectric element actuator 7 bonded thereto is very small. Moreover, since the process of creating the electrode U (4) in the inkjet head manufacturing process is not required, an effect equivalent to that of the first embodiment can be obtained while suppressing an increase in cost.

<Embodiment 3>
In the above description of the first and second embodiments, the description has been made with reference to the laminated piezo type head. However, the present invention is not limited to the laminated piezo type head.
For example, FIG. 5 is a schematic cross-sectional view illustrating an example of application to a thin-film piezo head, which corresponds to FIG. FIG. 6 is a schematic cross-sectional view of FIG. 5 viewed from the side.

  In these drawings, 13 is a fluid resistance section, 14 is a supply section, 15 is a common liquid chamber, and a line indicated by 16 is an ink flow path. In the figure, 21 is an upper electrode (individual electrode), 22 is a lower electrode (common electrode), and 23 is a piezoelectric layer (PZT). Reference numeral 24 denotes a piezoelectric element protection space, and reference numeral 25 denotes a wiring space. A bypass wiring 26 is wired in the wiring space 25. In the figure, 27 is an upper electrode pad portion, 28 is a protective substrate (subframe), 29 is an interlayer insulating film, 30 is a passivation layer, and 31 is a lead wiring. Reference numeral 32 denotes a column of the protective substrate 28, and 33 denotes a flow path partition wall.

  In the case of a thin film piezo type head, an electrode (electrode U (4) in the illustrated example) for applying an electric field to the piezo (piezoelectric element) is provided on the upper surface of the diaphragm 6. Therefore, in order to substitute the diaphragm 6 itself for the electrode U (4) for electrophoresis, it is possible to provide an insulating layer (an interlayer insulating film 29 in the illustrated example) on the upper surface of the diaphragm 6.

<Embodiment 4>
Hereinafter, an ink jet recording apparatus as an example of an image forming apparatus equipped with an ink jet head according to the present invention will be described with reference to FIGS. FIG. 7 is an explanatory perspective view of the ink jet recording apparatus, and FIG. 8 is an explanatory side view of a mechanism portion of the ink jet recording apparatus.

  This ink jet recording apparatus is an example, but includes a recording head including a carriage movable in the main scanning direction inside the recording apparatus main body 81 and an ink jet head embodying the present invention mounted on the carriage. Inside the recording apparatus main body 81 is housed a printing mechanism portion 82 and the like configured by an ink cartridge for supplying ink to the recording head. Further, a paper feed cassette (or a paper feed tray) 84 on which a large number of sheets 83 can be stacked from the front side can be detachably attached to the lower part of the recording apparatus main body 81. Further, the manual feed tray 85 for manually feeding the paper 83 can be turned over. As a result, the paper 83 fed from the paper feed cassette 84 or the manual feed tray 85 is taken in, and after a required image is recorded by the printing mechanism unit 82, the paper is discharged onto the paper discharge tray 86 mounted on the rear side.

  The printing mechanism 82 holds a carriage 93 slidably in the main scanning direction by a main guide rod 91 and a sub guide rod 92 which are guide members horizontally mounted on left and right side plates (not shown). A recording head 94 composed of an ink jet head according to the present invention is mounted on the carriage 93 in such a manner that a plurality of ink discharge ports (nozzles) are arranged in a direction crossing the main scanning direction and the ink droplet discharge direction is directed downward. . The recording head 94 ejects ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (Bk). Further, each ink cartridge 95 for supplying ink of each color to the recording head 94 is replaceably mounted on the carriage 93.

  The ink cartridge 95 has an air port that communicates with the atmosphere upward, a supply port that supplies ink to the inkjet head below, and a porous body filled with ink inside. The ink supplied to the inkjet head is maintained at a slight negative pressure by the capillary force of the porous body. Further, although the recording heads 94 for the respective colors are used here as the recording heads, a single head having nozzles for ejecting ink droplets of the respective colors may be used.

  Here, the carriage 93 is slidably fitted to the main guide rod 91 on the rear side (downstream side in the paper conveyance direction), and is slidably mounted on the sub guide rod 92 on the front side (upstream side in the paper conveyance direction). doing. In order to move and scan the carriage 93 in the main scanning direction, a timing belt 100 is stretched between a driving pulley 98 and a driven pulley 99 that are rotationally driven by a main scanning motor 97. The timing belt 100 is fixed to the carriage 93, and the carriage 93 is reciprocated by forward and reverse rotation of the main scanning motor 97.

  On the other hand, in order to convey the paper 83 set in the paper feed cassette 84 to the lower side of the recording head 94, a paper feed roller 101 and the like are provided. The paper supply roller 101 and the friction pad 102 separate and supply the paper 83 from the paper supply cassette 84. A guide member 103 that guides the paper 83 and a conveyance roller 104 that reverses and conveys the fed paper 83 are provided. Further, a conveyance roller 105 pressed against the peripheral surface of the conveyance roller 104 and a leading end roller 106 that defines a feeding angle of the paper 83 from the conveyance roller 104 are provided. The transport roller 104 is rotationally driven by a sub-scanning motor 107 through a gear train.

  A printing receiving member 109 is provided as a paper guide member that guides the paper 83 sent from the transport roller 104 below the recording head 94 in accordance with the movement range of the carriage 93 in the main scanning direction. On the downstream side of the printing receiving member 109 in the sheet conveyance direction, a conveyance roller 111 and a spur 112 that are rotationally driven to send out the sheet 83 in the sheet discharge direction are provided. Further, a paper discharge roller 113 and a spur 114 for feeding the paper 83 to the paper discharge tray 86, and guide members 115 and 116 for forming a paper discharge path are provided.

  At the time of recording, the recording head 94 is driven according to the image signal while moving the carriage 93, thereby ejecting ink onto the stopped sheet 83 to record one line. Record the line. Upon receiving a recording end signal or a signal that the trailing edge of the paper 83 has reached the recording area, the recording operation is terminated and the paper 83 is discharged.

  Further, a recovery device 117 for recovering the ejection failure of the recording head 94 is disposed at a position outside the recording area on the right end side in the movement direction of the carriage 93. The recovery device 117 includes a cap unit, a suction unit, and a cleaning unit. The carriage 93 is moved to the recovery device 117 side during printing standby, and the recording head 94 is capped by the capping unit, and the ejection port portion is kept in a wet state to prevent ejection failure due to ink drying. Further, by ejecting ink that is not related to recording during recording or the like, the ink viscosity of all the ejection ports is made constant and stable ejection performance is maintained.

  When a discharge failure occurs, the discharge port (nozzle) of the recording head 94 is sealed with a capping unit, and bubbles and the like are sucked out from the discharge port with a suction unit through a tube. As a result, ink, dust or the like adhering to the ejection port surface is removed by the cleaning means, and the ejection failure state is recovered. Further, the sucked ink is discharged to a waste ink reservoir (not shown) installed at the lower part of the main body and absorbed and held by an ink absorber inside the waste ink reservoir.

  In future industrial applications, there is a possibility of application to a head that ejects special ink, for example, large charged particles or living cells.

  The present invention is not limited to the embodiments described above, and many variations are possible by those having ordinary knowledge in the art within the technical idea of the present invention.

1: Nozzle substrate 2: Liquid chamber substrate 3: Nozzles 4 and 5: Electrode 6: Vibration plate 7: Piezoelectric element actuator 8: FPC
9: Base material 10: Frame 11: Drive circuit 12: Pressure chamber 13: Fluid resistance unit 14: Supply unit 15: Common liquid chamber 16: Ink channel 21: Upper electrode (individual electrode)
22: Lower electrode (common electrode)
23: Piezoelectric layer (PZT)
24: Piezoelectric element protection space 25: Wiring space 26: Bypass wiring 28: Protection substrate 29: Interlayer insulating film 30: Passivation layer 31: Lead-out wiring 32: Protection substrate column 33: Channel partition wall 81: Recording device main body 82: Printing mechanism 83: Paper 84: Paper feed cassette 85: Manual feed tray 86: Paper discharge tray 91: Main guide rod 92: Secondary guide rod 93: Carriage 94: Recording head 95: Ink cartridge 97: Main scanning motor 98: Drive pulley 99: driven pulley 100: timing belt 101: feed roller 102: friction pad 103: guide member 104: transport roller 105: transport roller 106: tip roller 107: sub-scanning motor 109: printing receiving member 111: transport roller 112: Spur 113: Paper discharge roller 114: Spur 115 : Guide member 116: guide member 117: recovery device L: electrode Pp: pigment fine particles

JP 05-254118 A JP 2013-176852 A JP 2011-167930 A

Claims (6)

A nozzle substrate having a plurality of nozzle holes for discharging ink;
A pressure chamber communicating with the nozzle hole;
A piezoelectric element actuator for generating a pressure for discharging the ink liquid filled in the pressure chamber;
A diaphragm that is bonded to the piezoelectric element actuator and propagates pressure to the pressure chamber;
Voltage applying means for applying a voltage to the piezoelectric element actuator;
Have
In an inkjet head that discharges ink liquid containing charged ink particle components such as pigment-dispersed ink from the nozzle holes,
A conductive layer to be an electrode is formed on the surface of the nozzle substrate on the pressure chamber side and on the surface of the diaphragm on the side opposite to the pressure chamber,
An electrophoretic phenomenon is generated in the ink liquid in the pressure chamber by applying a potential difference that controls energization start, energization end, energization time, etc. between these conductive layers, and the electrophoretic phenomenon will cause sedimentation on the bottom surface of the pressure chamber. A control means for floating the ink particle component
An inkjet head characterized by that. The inkjet head according to claim 1, wherein the conductive layer formed on the diaphragm is made of a conductive material, and the diaphragm is substituted for the electrode.
An inkjet head characterized by that.   3. The ink jet head according to claim 1, wherein the ink jet head is a stacked piezo head.   3. The ink jet head according to claim 1, wherein the ink jet head is a thin film type piezo head.   An ink jet recording apparatus using the ink jet head according to claim 1. An image forming apparatus using the ink jet head according to claim 1.