JP2012179821A - Liquid ejecting device - Google Patents

Abstract

Disclosed is a nozzle that can effectively maintain a discharge diameter of a liquid at an opening of a nozzle opening over a long period of time, and lowers the viscosity of a liquid that is thickened at a meniscus portion in the opening, thereby discharging the liquid. A liquid ejecting apparatus capable of maintaining good characteristics for a long period of time is provided.
A pressure generating chamber filled with liquid, a piezoelectric element that deforms by supplying a driving signal and causes a pressure change in the liquid via an elastic film, and a nozzle that discharges the liquid in the pressure generating chamber in accordance with the pressure change A liquid ejecting apparatus including a liquid ejecting head including an opening 21 and a control unit that supplies a drive signal. The nozzle opening has a discharge port diameter from the pressure generating chamber side toward the opening 21A of the nozzle opening. The control means increases the volume of the pressure generation chamber by deformation of the pressure generation means, and then deforms the pressure generation means in the direction opposite to the deformation direction through the nozzle opening. The piezoelectric element is controlled so that the liquid is discharged.
[Selection] Figure 4

Description

The present invention relates to a liquid ejecting apparatus, and in particular, once a liquid meniscus is drawn into a pressure generating chamber, the volume in the pressure generating chamber is expanded, and a pressure in a reverse direction is applied to the liquid from such a state to drop droplets from a nozzle opening. The present invention is useful when applied to a liquid ejecting apparatus equipped with a liquid ejecting head for performing so-called striking.

As the liquid ejecting apparatus, for example, a plurality of pressure generating chambers that generate pressure for ejecting ink droplets by pressure generating means including, for example, a piezoelectric element, and an ink supply path for individually supplying ink from a common reservoir to each pressure generating chamber And an ink jet recording apparatus (hereinafter also referred to as a recording apparatus) including an ink jet recording head (hereinafter also referred to as a recording head) that is formed in each pressure generating chamber and includes a nozzle opening that discharges ink droplets. (For example, refer to Patent Document 1).

In such a recording apparatus, ejection energy is applied to the ink in the pressure generating chamber communicated with the nozzle corresponding to the print signal, and ink droplets are ejected from the nozzle opening to the outside, and land on a predetermined position of a medium such as paper. Therefore, in this type of recording apparatus, the nozzle opening faces the atmosphere. For this reason, the ink is thickened by evaporation through the nozzle openings. As a result, the ink droplet ejection characteristics may be adversely affected due to the thickened ink. In other words, the thickened ink adheres to the periphery of the opening of the nozzle opening in a solidified state, resulting in a narrowing of the effective discharge port diameter of the nozzle opening, resulting in inconvenience that landing variation occurs. In this case, since the discharge port diameter of the nozzle opening that determines the discharge performance depends on the discharge port diameter of the base end portion, the effective discharge port diameter of the nozzle opening is narrowed by the ink thickening phenomenon as described above. This is because the ejection amount and ejection speed of ink droplets change.

For this reason, in the general-purpose recording apparatus according to the related art, for example, before the ink is thickened, the ink near the nozzle opening is always fresh by moving the recording head to a part other than the medium and appropriately discharging the ink. The device has been devised such as maintaining a proper state.

JP 2002-355961 A

However, as described above, when ink is discharged, there remains a problem that ink is wasted.

Such problems are not limited to ink jet recording heads that eject ink,
This also exists in a liquid ejecting head that ejects liquid other than ink.

In view of the above-described problems of the prior art, the present invention can effectively maintain the discharge diameter of the liquid at the opening of the nozzle opening at a predetermined discharge diameter for a long time without discarding the liquid. An object of the present invention is to provide a liquid ejecting apparatus capable of reducing the viscosity of a liquid thickened at a meniscus portion in an opening and maintaining good discharge characteristics over a long period of time.

An aspect of the present invention that solves the above problem includes a pressure generating chamber in which one surface is defined by a vibrating portion and filled with a liquid, and a pressure change is applied to the liquid via the vibrating portion that is deformed by supplying a driving signal. A liquid ejecting apparatus comprising: a pressure ejecting unit that generates pressure; a liquid ejecting head that includes a nozzle opening that ejects liquid in the pressure generating chamber in accordance with the pressure change; and a control unit that supplies the drive signal. The nozzle opening is formed in a tapered shape in which the discharge port diameter gradually increases from the pressure generating chamber side toward the opening of the nozzle opening, and the control means is configured to deform the pressure generating means. After the volume of the pressure generating chamber is increased by deformation of the vibrating portion, the liquid is discharged through the nozzle opening by deforming the pressure generating means in a direction opposite to the deformation direction. Serial there is provided a liquid ejecting apparatus characterized by controlling the pressure generating means.
According to this aspect, even if the thickened portion where the ink is solidified due to the increase in the viscosity of the ink is formed in the peripheral portion in the opening portion of the nozzle opening, the taper shape formed toward the opening portion of the nozzle opening causes the above-described Since the discharge port diameter gradually increases toward the opening, the influence of the decrease in the discharge port diameter in the opening due to the solidified thickened part is removed, and the influence on the droplet discharge characteristics by the thickened part is reduced as much as possible. can do. That is, since it is easy to maintain the discharge port diameter of the opening more than the discharge port diameter of the base end of the nozzle opening that defines the discharge characteristics of the droplets discharged through the nozzle opening, It is possible to stably maintain the discharge characteristics defined by the discharge port diameter over a long period of time.

Further, in this aspect, the liquid of the meniscus portion thickened by touching air at the opening is drawn upstream and mixed with the fresh liquid that has not been thickened. The viscosity of the liquid can be reduced. Since the liquid is discharged through the nozzle opening after being mixed with the fresh liquid in this way, the liquid droplet can be landed on a predetermined medium while maintaining good discharge characteristics.

Furthermore, in this aspect, since the viscosity of the liquid in the meniscus portion is reduced by mixing with fresh liquid, solidification of the thickened portion can be suppressed by that amount, which also contributes to stabilization of the discharge characteristics. be able to.
As a result, it is possible to realize a liquid ejecting apparatus that can improve the quality of printed matter by improving the liquid ejection characteristics.

Here, the pressure generating means is preferably formed of a piezoelectric element. In this case, it is possible to easily realize so-called striking, in which the liquid is once drawn from the opening of the nozzle opening to the pressure generating chamber side and then the pressure is generated in the opposite direction to discharge the droplet from the nozzle opening. is there.

FIG. 2 is an exploded perspective view illustrating a schematic configuration of a recording head according to an embodiment. It is a top view of FIG. FIG. 3 is a cross-sectional view taken along line AA ′ in FIG. 2. FIG. 3 is a schematic diagram illustrating an enlarged nozzle opening portion of a recording head. It is a wave form diagram which shows a drive signal. It is the schematic which shows an example of the recording device which concerns on embodiment. It is a block diagram which shows the control system which concerns on embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows an ink jet recording head constituting an ink jet recording head unit (hereinafter also referred to as a head unit) mounted on an ink jet recording apparatus (hereinafter also referred to as a recording device) as an example of a liquid ejecting apparatus according to the present embodiment. 1 is an exploded perspective view showing a schematic configuration (hereinafter also referred to as a recording head). 2 is a plan view of FIG. 1, and FIG.
It is A 'sectional view.

As shown in FIGS. 1 to 3, the flow path forming substrate 10 of the recording head I is made of a silicon single crystal substrate, and one surface thereof is made of silicon dioxide, and an elastic film 50 serving as a vibrating portion in this embodiment is formed. Is formed. A plurality of pressure generating chambers 12 are arranged in parallel in the width direction of the flow path forming substrate 10. In addition, a communication portion 13 is formed in a region outside the longitudinal direction of the pressure generation chamber 12 of the flow path forming substrate 10, and the communication portion 13 and each pressure generation chamber 12 are provided for each pressure generation chamber 12. Communication is made via a supply path 14 and a communication path 15. The communication part 13 communicates with a manifold part 31 of the protective substrate 30 described later and constitutes a part of the manifold 100 that becomes a common ink chamber of each pressure generating chamber 12. The ink supply path 14 is formed with a narrower width than the pressure generation chamber 12, and maintains a constant flow path resistance of ink flowing into the pressure generation chamber 12 from the communication portion 13. In this embodiment, the ink supply path 14 is reduced by narrowing the width of the flow path from one side.
However, the ink supply path may be formed by narrowing the width of the flow path from both sides. Further, the ink supply path may be formed by narrowing from the thickness direction instead of narrowing the width of the flow path. Thus, in this embodiment, the pressure generation chamber 12, the communication portion 13, and the ink supply path 14 are provided on the flow path forming substrate 10.
In addition, a liquid flow path including the communication path 15 is provided, and the pressure generation chamber 12 is filled with ink.

In addition, a nozzle plate in which a nozzle opening 21 communicating with the vicinity of the end portion of each pressure generating chamber 12 on the side opposite to the ink supply path 14 is formed on one side of the flow path forming substrate 10. 2
0 is fixed by an adhesive, a heat welding film, or the like. Here, the nozzle plate 20
Can be suitably composed of, for example, glass ceramics, a silicon single crystal substrate, stainless steel or the like.

As described above, the elastic film 50 is formed on the opening surface on the opposite side of the flow path forming substrate 10. The elastic film 50 is made of, for example, titanium oxide having a thickness of about 30 to 50 nm. An adhesion layer 56 is provided for improving the adhesion between the first electrode 60 and the base. Note that an insulator film made of zirconium oxide or the like may be provided on the elastic film 50 as necessary.

Further, on the adhesion layer 56, the first electrode 60 and a thickness of 2 μm or less, preferably 0.
A piezoelectric layer 70 that is a thin film having a thickness of 3 to 1.5 μm and a second electrode 80 are laminated to form a piezoelectric element 300. Here, the piezoelectric element 300 is a pressure generating unit in this embodiment, and refers to a portion including the first electrode 60, the piezoelectric layer 70, and the second electrode 80. In general, one electrode of the piezoelectric element 300 is used as a common electrode, and the other electrode and the piezoelectric layer 70 are patterned for each pressure generating chamber 12. In this embodiment, the first electrode 60 is connected to the piezoelectric element 300.
Although the second electrode 80 is an individual electrode of the piezoelectric element 300, there is no problem even if it is reversed for the convenience of the drive circuit and wiring. Also, here, the piezoelectric element 300 and the diaphragm that is displaced by driving the piezoelectric element 300 are collectively referred to as an actuator device.
In the above-described example, the elastic film 50, the adhesion layer 56, the first electrode 60, and the insulator film provided as necessary function as a vibration plate. However, the present invention is not limited to this. For example, the elastic film 50 and the adhesion layer 56 may not be provided. Further, the piezoelectric element 300 itself may substantially serve as a diaphragm.

The second electrode 80, which is an individual electrode of the piezoelectric element 300, is drawn from the vicinity of the end on the ink supply path 14 side, and extends to the elastic film 50 or an insulator film provided as necessary.
For example, a lead electrode 90 made of gold (Au) or the like is connected.

On the flow path forming substrate 10 on which the piezoelectric element 300 is formed, that is, the first electrode 60 and the elastic film 5.
A protective substrate 30 having a manifold portion 31 that constitutes at least a part of the manifold 100 is bonded via an adhesive 35 on 0 or an insulating film provided as necessary and the lead electrode 90. In the present embodiment, the manifold portion 31 is formed across the protective substrate 30 in the thickness direction and across the width direction of the pressure generation chamber 12. As described above, the manifold portion 31 is connected to the communication portion 13 of the flow path forming substrate 10. A manifold 100 is formed which communicates and serves as a common ink chamber for the pressure generation chambers 12. Alternatively, the communication portion 13 of the flow path forming substrate 10 may be divided into a plurality of pressure generation chambers 12 and only the manifold portion 31 may be used as a manifold. Further, for example, only the pressure generation chamber 12 is provided in the flow path forming substrate 10 and a member (for example, an elastic film 50, an insulator film provided as necessary, etc.) interposed between the flow path forming substrate 10 and the protective substrate 30 is provided. ) May be provided with an ink supply path 14 for communicating the manifold 100 and each pressure generating chamber 12.

A piezoelectric element holding portion 32 having a space that does not hinder the movement of the piezoelectric element 300 is provided in a region of the protective substrate 30 that faces the piezoelectric element 300. Piezoelectric element holder 32
Need only have a space that does not hinder the movement of the piezoelectric element 300, and the space may or may not be sealed.

As such a protective substrate 30, it is preferable to use a material substantially the same as the coefficient of thermal expansion of the flow path forming substrate 10, for example, glass, ceramic material, etc. In this embodiment, the flow path forming substrate 10 is used.
Is formed using a silicon single crystal substrate of the same material.

Further, the protective substrate 30 is provided with a through hole 33 that penetrates the protective substrate 30 in the thickness direction, and the vicinity of the end portion of the lead electrode 90 drawn from each piezoelectric element 300 is exposed in the through hole 33. It is comprised so that it may do.

On the other hand, a drive circuit 120 that drives the piezoelectric element 300 under control of a control unit (not shown in FIGS. 1 to 3) described in detail later is fixed on the protective substrate 30. For example, a circuit board or a semiconductor integrated circuit (IC) can be used as the drive circuit 120. And
The drive circuit 120 and the lead electrode 90 are electrically connected via a connection wiring 121 made of a conductive wire such as a bonding wire.

In addition, a compliance substrate 40 including a sealing film 41 and a fixing plate 42 is bonded onto the protective substrate 30. Here, the sealing film 41 is made of a material having low rigidity and flexibility, and one surface of the manifold portion 31 is sealed by the sealing film 41.
The fixing plate 42 is formed of a relatively hard material. Since the region of the fixing plate 42 facing the manifold 100 is an opening 43 that is completely removed in the thickness direction,
One surface of the manifold 100 is sealed only with a flexible sealing film 41.

In such a recording head I, ink is taken in from an ink introduction port connected to an external ink supply unit (not shown), and ink is filled from the manifold 100 to the nozzle opening 21. Thereafter, in accordance with a drive signal from the drive circuit 120, a voltage is applied between each of the first electrode 60 and the second electrode 80 corresponding to the pressure generation chamber 12, and the elastic film 50 and the adhesion layer 5 are applied.
6. The first electrode 60 and the piezoelectric layer 70 are bent and deformed. Thus, the vibration accompanying the deformation is transmitted to the ink in each pressure generating chamber 12 through the elastic film 50 functioning as a vibrating portion. As a result, the pressure in each pressure generating chamber 12 increases and ink droplets are ejected from the nozzle openings 21. The ink ejection driving operation will be described in detail later.

4A and 4B are enlarged views of the nozzle opening portion of the recording head. FIG. 4A is a schematic diagram illustrating the nozzle opening of the present embodiment, and FIG. 4B is a schematic diagram illustrating the conventional nozzle opening. As shown in FIG. 2A, the nozzle opening 21 is formed in a tapered shape in which the discharge port diameter gradually increases from the pressure generating chamber 12 (see FIGS. 1 to 3) side toward the opening 21A of the nozzle opening 21. Yes. That is, (opening 2
1A discharge port diameter Φ1)> (discharge port diameter Φ2 of the base end portion 21B). Therefore, the thickened portion 22 may be formed in the peripheral portion of the opening portion 21A due to the increase in the viscosity of the ink and the ink solidifies over time.

However, in this embodiment, even if the thickening portion 22 prevents the peripheral portion of the opening 21A from functioning as an ink droplet discharge path (the discharge port diameter Φ3 in the central portion excluding the thickening portion 22). It is easy to satisfy ≧ (discharge port diameter Φ2 of the base end portion 21B). This is because the nozzle opening 21 is formed in a tapered shape in which the discharge port diameter gradually increases toward the opening 21A. As a result, it is possible to reduce as much as possible the influence of the thickened portion 22 on the ink droplet ejection characteristics. That is, since the ejection characteristics of the ink droplets ejected through the nozzle opening 21 are uniquely determined based on the ejection port diameter Φ2, if the relationship of (ejection port diameter Φ3) ≧ (ejection port diameter Φ2) is maintained, the increase is increased. The presence of the viscous portion 22 does not hinder the ejection of ink droplets through the opening 21A. On the other hand, when the thickened portion 022 is formed in the conventional nozzle opening 021 shown in FIG. 4B, the substantial discharge port diameter Φ4 is reduced accordingly. That is, (discharge port diameter Φ2)> (discharge port diameter Φ4) with respect to the discharge port diameter Φ2 determined in consideration of the discharge characteristics of the ink droplets, the discharge characteristics deteriorate accordingly.

Furthermore, in this embodiment, since the piezoelectric element 300 is driven by the drive signal SD having the waveform shown in FIG. 5, the ink in the meniscus portion thickened by touching the air in the opening 21A is upstream (pressure generation chamber). 12 side) and mixed with fresh ink that has not been thickened, and then can be discharged to the outside through the nozzle openings 21. More specifically, first, a negative voltage is applied between the first electrode 60 and the second electrode 80 that are at ground potential (portion A in FIG. 5). As a result, since the piezoelectric element 300 is deformed so as to protrude upward in FIG. 3, the volume of the pressure generating chamber 12 increases, and the ink in the meniscus portion formed in the opening 21A is moved to the pressure generating chamber 12 side. Be drawn into. The ink whose viscosity has been increasing at the meniscus portion facing the air is drawn into the pressure generating chamber 12 and mixed with fresh ink in the pressure generating chamber 12. As a result, the viscosity of the ink that has been increased in viscosity can be reduced.

From this state, a positive voltage is applied between the first electrode 60 and the second electrode 80 that are at the ground potential (B portion in FIG. 5). As a result, the piezoelectric element 300 is deformed so as to be convex downward in FIG. 3 this time, so that the elastic film 50 is deformed by such deformation, and the pressure generating chamber 1
2 causes pressure fluctuations in the ink in 2. As a result, the ink in the pressure generation chamber 12 is pushed downward and discharged through the nozzle opening 21. Thus, after the viscosity of the meniscus portion thickened in the opening 21A is mixed with the fresh ink in the pressure generation chamber 12 to reduce the viscosity, the ink can be ejected in a predetermined manner. As a result, it is possible to remove the influence of ink thickening and maintain good ejection characteristics.

Furthermore, in this embodiment, the viscosity of the ink in the meniscus portion is also reduced by mixing with fresh ink in the pressure generation chamber 12, so that solidification of the thickened portion 22 can be suppressed accordingly.

FIG. 6 is a schematic view showing a recording apparatus which is a liquid ejecting apparatus according to this embodiment. As shown in the drawing, in the recording apparatus II according to the present embodiment, a recording head I having an ink flow path communicating with an ink cartridge or the like constitutes recording head units 1A and 1B. Here, the recording head units 1A and 1B are detachably provided with cartridges 2A and 2B constituting the ink supply means, and a carriage 3 on which the recording head units 1A and 1B are mounted is provided.
A carriage shaft 5 attached to the apparatus body 4 is provided so as to be movable in the axial direction. The recording head units 1A and 1B, for example, are configured to eject a black ink composition and a color ink composition, respectively. Then, the driving force of the driving motor 6 is transmitted to the carriage 3 via a plurality of gears and a timing belt 7 (not shown), so that the carriage 3 on which the recording head units 1A and 1B are mounted is moved along the carriage shaft 5. The On the other hand, the apparatus body 4 is provided with a platen 8 along the carriage shaft 5, and a recording sheet S which is a recording medium such as paper fed by a supply roller (not shown) is wound around the platen 8 and conveyed. It has come to be.

FIG. 7 is a block diagram showing a control system of the ink jet recording apparatus according to this embodiment. As shown in the figure, a controller 110 for controlling the recording apparatus II is provided in the recording apparatus II. The control unit 110 includes a CPU 111, a device control unit 112, and a drive circuit 120 that is a head control unit for a capacitive load.

More specifically, when a signal indicating movement of the carriage 3 (see FIG. 6) is input from the CPU 111 to the apparatus control unit 112, the apparatus control unit 112 drives the drive motor 6 to move the carriage 3 to the carriage shaft 5. A signal indicating conveyance of the recording sheet S (see FIG. 6) from the CPU 111 is input to the apparatus control unit 112, and the apparatus control unit 112
The supply roller 23 is driven to convey the recording sheet S.

On the other hand, the driving circuit 120 includes an analog signal SA for generating a head driving signal SD from the CPU 111 and a switching signal S for performing switching control of the driving circuit 120.
S is input. The drive circuit 120 generates a drive signal SD based on the analog signal SA and the switching signal SS, and selectively drives each piezoelectric element 300 of the recording head I to eject ink. The drive signal SD is a signal having a waveform shown in FIG. More specifically, the drive circuit 120 forms the drive signal SD having the waveform shown in FIG. 5 based on the analog signal SA and the switching signal SS supplied from the CPU 111 and selectively applies the drive signal SD to the piezoelectric element 300. . As a result, in the recording head I, the above-described striking operation described with reference to FIG. 5 is performed, and the ink that has formed the meniscus at the nozzle opening 21 is drawn into the pressure generating chamber 12 side and mixed with fresh ink. After the viscosity is reduced by this, the ink is discharged toward a medium such as paper to be printed.

(Other embodiments)
As mentioned above, although each embodiment of this invention was described, the basic composition of this invention is not limited to what was mentioned above. For example, the recording apparatus II in the above embodiment has a recording head I using a thin film type piezoelectric element 300 as pressure generating means for causing a pressure change in the pressure generating chamber 12.
However, it is not necessary to limit to this. Any ink can be used as long as it can draw the ink meniscus formed in the nozzle opening to the pressure generating chamber 12 side and then eject the ink as ink droplets from the nozzle opening. For example, a thick film type piezoelectric actuator formed by a method such as attaching a green sheet, or a longitudinal vibration type piezoelectric actuator in which piezoelectric materials and electrode forming materials are alternately stacked to expand and contract in the axial direction is used. be able to. Further, even a so-called electrostatic actuator that generates static electricity between the diaphragm and the electrode, deforms the diaphragm by electrostatic force, and discharges droplets from the nozzle openings can be applied in principle.

In the embodiment shown in FIG. 6, the recording head units 1A and 1B are mounted on the carriage 3 that moves in the direction (main scanning direction) intersecting the conveyance direction of the recording sheet S, and the recording head units 1A and 1B are mainly used. This is a so-called serial type ink jet recording apparatus that performs printing while moving in the scanning direction, but is not limited thereto. Of course, it may be a so-called line-type ink jet recording apparatus in which printing is performed simply by transporting the recording sheet S while the recording head is fixed.

Furthermore, in the above-described embodiment, the ink jet recording apparatus has been described as an example of the liquid ejecting apparatus. However, the present invention is widely applied to all liquid ejecting apparatuses having a liquid ejecting head, and liquid other than ink. Needless to say, the present invention can also be applied to a liquid ejecting apparatus that includes a liquid ejecting head that ejects the liquid. Other liquid ejecting heads include, for example, various recording heads used in image recording apparatuses such as printers, color material ejecting heads used in the manufacture of color filters such as liquid crystal displays, organic EL displays, and FEDs (field emission displays). Examples thereof include an electrode material ejection head used for electrode formation, a bioorganic matter ejection head used for biochip production, and the like.

I ink jet recording head (recording head), II ink jet recording device (recording device), 10 flow path forming substrate, 12 pressure generating chamber, 20 nozzle plate,
21 nozzle opening, 21A opening, 21B base end, 22 thickening part, 50 elastic film, 60 first electrode, 70 piezoelectric layer, 80 second electrode, 90 lead electrode,
100 manifold, 110 control unit, 120 drive circuit, 300 piezoelectric element

Claims (2)

A pressure generating chamber in which one surface is defined by a vibrating portion and filled with a liquid; a pressure generating means that deforms by supply of a drive signal to cause a pressure change in the liquid via the vibrating portion; and the pressure change And a liquid jet head provided with a nozzle opening for discharging the liquid in the pressure generating chamber,
A liquid ejecting apparatus comprising control means for supplying the drive signal,
The nozzle opening is formed in a tapered shape in which the discharge port diameter gradually increases from the pressure generation chamber side toward the opening of the nozzle opening,
The control means increases the volume of the pressure generating chamber by the deformation of the vibration part accompanying the deformation of the pressure generating means, and then deforms the pressure generating means in a direction opposite to the direction of the deformation to thereby reduce the nozzle. The liquid ejecting apparatus according to claim 1, wherein the pressure generating unit is controlled to discharge the liquid through an opening. The liquid ejecting apparatus according to claim 1,
The liquid ejecting apparatus according to claim 1, wherein the pressure generating means is formed of a piezoelectric element.

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