JP5979345B2 - Liquid ejecting head and liquid ejecting apparatus - Google Patents

Description

  The present invention relates to a liquid ejecting head and a liquid ejecting apparatus, and is particularly useful when applied to a case where a droplet attached to a nozzle plate is separated from a nozzle opening.

  As a liquid ejecting apparatus, for example, a pressure generating chamber that generates pressure for ejecting ink droplets by a pressure generating means made of a piezoelectric element, for example, a pressure change is generated in the ink filled in the pressure generating chamber, and the nozzle plate is formed. There is known 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 discharges ink droplets through the nozzle openings.

  In this type of recording apparatus, high density arrangement of nozzle openings of the recording head and high speed driving are effective for improving the printing speed. However, when the recording head is driven at a high speed, minute mist-like ink droplets scattered along with the ink droplets ejected from the nozzle openings adhere to the vicinity of the nozzle openings of the nozzle plate, and the ejected ink droplets are not bent or flying. Inducing discharge failure such as discharge.

  For this reason, measures are taken such as periodically performing a maintenance operation such as wiping on the surface of the nozzle plate in which the nozzle openings are formed. However, as a result of such a maintenance operation, the high throughput performance of the apparatus, which is the purpose of high-speed operation, is reduced.

  On the other hand, with respect to ejection failure caused by adhesion of minute ink droplets to the nozzle plate, a liquid repellent part is provided around the nozzle opening, and a groove or an annular pattern having a poor liquid repellency is provided in the liquid repellent part. Therefore, a structure for removing droplets adhering to the vicinity of the ejection hole has been proposed (see, for example, Patent Documents 1 and 2). In Patent Document 1, liquid droplets held in the form of large droplets on the nozzle surface are excluded at portions having different liquid repellency to prevent ejection defects caused by droplets remaining at the nozzle discharge ports. Is. Further, Patent Document 2 has a discharge surface composed of a plurality of liquid repellent layers and a plurality of hydrophilic regions with a difference in ease of liquid drop entry, and utilizes inertial force or force of air flow. Thus, the droplets are kept away from the nozzle. As a result, the wipe frequency is reduced, the life of the discharge surface is extended, and the throughput is improved by reducing the maintenance frequency.

JP 2002-86021 A JP 2005-313637 A

  However, the conventional techniques disclosed in Patent Documents 1 and 2 merely promote the movement of the adhering liquid on the pattern due to the surface tension difference between the liquid repellency and the lyophilic property. As a result, since the droplets on the pattern are stationary at the balance position of the surface energy, it cannot be an appropriate droplet moving means, and is not sufficient as a means for improving the throughput.

  In view of the above-described problems of the prior art, the present invention removes droplets attached in the vicinity of the nozzle opening to maintain good droplet discharge performance through the nozzle opening and contribute to further improvement in throughput. An object of the present invention is to provide a liquid ejecting head and a liquid ejecting apparatus that can perform the above operation.

An aspect of the present invention that solves the above-described problem is a liquid ejecting head that causes a pressure change in a liquid in a pressure generation chamber by pressure generation means and discharges the liquid in the pressure generation chamber through a nozzle opening formed in a nozzle plate A liquid repellent film formed on a surface opposite to the pressure generating chamber of the nozzle plate and capable of electrochemically controlling wettability based on a potential gradient formed by applying a voltage, In contrast to the positive / negative polarity of the voltage applied to one electrode of the electrode pair embedded in the liquid-repellent film while maintaining the electrical insulation, the other electrode is applied with a voltage of opposite sign polarity. And the liquid repellent film is made of an organic molecule having a functional group having a reversible redox ability or an organic molecule having a polynuclear metal complex as a functional group. Located in the liquid jet head.
According to this aspect, the lyophilic / liquid repellent gradient is generated along the voltage gradient formed by the positive and negative electrode pairs with respect to the liquid repellent film. For this reason, the droplets adhering to the liquid repellent film are drawn into the lyophilic region and are discharged from the region having the liquid repellency. As a result, the moving force to the method of separating the droplet from the nozzle opening acts, and the droplet can be excluded from the vicinity of the nozzle opening. As a result, it is possible to effectively prevent ejection defects such as flight bending of droplets ejected from the nozzle openings.
Here, the voltage applying means is configured so that a plurality of the electrode pairs are formed, and the electrodes to which the voltage is applied are switched so as to move with time from the nozzle opening side, and the voltage is applied to the pair of the electrode pairs. Is preferably configured. In this case, the droplets adhering to the liquid repellent film can be positively moved in the direction away from the nozzle openings, and the droplets near the nozzle openings can be more reliably eliminated.
Another aspect of the invention is a liquid ejecting apparatus including the liquid ejecting head.
According to this aspect, the time required for maintenance such as conventional wiping can be reduced as much as possible, so that the throughput can be improved accordingly.
According to another aspect of the invention, there is provided a liquid ejecting head that causes a pressure change in the liquid in the pressure generating chamber by the pressure generating means and discharges the liquid in the pressure generating chamber through a nozzle opening formed in a nozzle plate. A liquid repellent film formed on the surface opposite to the pressure generating chamber of the nozzle plate and capable of electrochemically controlling the wettability based on a potential gradient formed by applying a voltage, and maintaining electrical insulation between them. A voltage capable of applying a voltage of opposite sign polarity to the other electrode with respect to the positive / negative polarity of the applied voltage to one electrode of the electrode pair embedded in the liquid repellent film in the state The liquid ejecting head includes an applying unit.
According to this aspect, the lyophilic / liquid repellent gradient is generated along the voltage gradient formed by the positive and negative electrode pairs with respect to the liquid repellent film. For this reason, the droplets adhering to the liquid repellent film are drawn into the lyophilic region and are discharged from the region having the liquid repellency. As a result, the moving force to the method of separating the droplet from the nozzle opening acts, and the droplet can be excluded from the vicinity of the nozzle opening. As a result, it is possible to effectively prevent ejection defects such as flight bending of droplets ejected from the nozzle openings.

  Here, the voltage applying means is configured so that a plurality of the electrode pairs are formed, and the electrodes to which the voltage is applied are switched so as to move with time from the nozzle opening side, and the voltage is applied to the pair of the electrode pairs. Is preferably configured. In this case, the droplets adhering to the liquid repellent film can be positively moved in the direction away from the nozzle openings, and the droplets near the nozzle openings can be more reliably eliminated.

Another aspect of the invention is a liquid ejecting apparatus including the liquid ejecting head.
According to this aspect, the time required for maintenance such as conventional wiping can be reduced as much as possible, so that the throughput can be improved accordingly.

It is a typical perspective view which shows the structure of a liquid ejecting apparatus. FIG. 2 is an exploded perspective view illustrating a schematic configuration of a recording head according to an embodiment. FIG. 3 is a plan view of FIG. 2. FIG. 4 is a cross-sectional view taken along line AA ′ in FIG. 3. It is an enlarged plan view which expands and shows the surface of a nozzle plate. FIG. 6 is a cross-sectional view taken along line BB ′ in FIG. 5.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic diagram illustrating an example of an ink jet recording apparatus (hereinafter also referred to as a recording apparatus). As shown in FIG. 1, the recording head units 1A and 1B are provided in an ink jet recording apparatus I as a liquid ejecting apparatus. That is, the recording head units 1A and 1B are mounted on the carriage 3 of the ink jet recording apparatus I, and the carriage 3 is provided on the carriage shaft 5 attached to the apparatus main body 4 of the ink jet recording apparatus I so as to be movable in the axial direction. ing. The recording head units 1A and 1B, for example, discharge a black ink composition and a color ink composition, respectively.

  The carriage 3 on which the recording head units 1A and 1B are mounted is moved along the carriage shaft 5 by transmitting the driving force of the driving motor 6 to the carriage 3 via a plurality of gears and a timing belt 7 (not shown). . On the other hand, the apparatus main 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 paper feeding roller (not shown) in FIG. It is wound around and transported.

  2 is an exploded perspective view showing a schematic configuration of an ink jet recording head (hereinafter also referred to as a recording head) incorporating the recording head units 1A and 1B shown in FIG. 1, and FIG. 3 is a plan view of FIG. FIG. 4 is a cross-sectional view taken along line AA ′ of FIG.

  As shown in FIGS. 2 to 4, the flow path forming substrate 11 of the recording head 10 is made of a silicon single crystal substrate. One surface of the flow path forming substrate 11 is made of silicon dioxide, and an elastic film 50 serving as a vibrating portion in this embodiment is formed. A plurality of pressure generating chambers 12 are arranged in the width direction on the flow path forming substrate 11. In addition, a communication portion 13 is formed in a region of the flow path forming substrate 11 outside the pressure generation chamber 12 in the longitudinal direction, 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 formed by narrowing the width of the flow path from one side, but 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 flow path forming substrate 11 is provided with a liquid flow path including the pressure generation chamber 12, the communication portion 13, the ink supply path 14, and the communication path 15, and ink is supplied to the pressure generation chamber 12. Filled.

  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 opening surface side of the flow path forming substrate 11. 20 is fixed by an adhesive, a heat welding film or the like. Here, the nozzle plate 20 can be suitably configured by, for example, a silicon single crystal substrate, stainless steel, or the like. On the surface of the nozzle plate 20, a liquid repellent film 52 is formed via an insulating film 51 when this is a conductor such as a silicon single crystal substrate or stainless steel. Here, the liquid repellent film 52 in this embodiment is formed of a material that can electrochemically control wettability based on a potential gradient formed by application of a voltage. For example, the desired liquid repellent film 52 can be suitably formed of an organic thin film made of an organic molecule having a functional group having a reversible redox ability such as ferrocenylalkanethiol. Moreover, it can also form with the organic thin film which consists of an organic molecule which has polynuclear metal complexes, such as other metallocenes and a ruthenium complex, in a functional group.

  Although not shown in FIGS. 1 to 4, a plurality of electrode pairs are embedded in the liquid repellent film 52. The electrode pair will be described in detail later.

  As described above, the elastic film 50 is formed on the opening surface on the opposite side of the flow path forming substrate 11. 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, a first electrode 60, a piezoelectric layer 70 which is a thin film having a thickness of 2 μm or less, preferably 0.3 to 1.5 μm, and a second electrode 80 are laminated. Thus, the piezoelectric element 300 is configured. 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 a common electrode of the piezoelectric element 300, and the second electrode 80 is an individual electrode of the piezoelectric element 300. However, there is no problem even if this 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.

  At least a part of the manifold 100 is formed on the flow path forming substrate 11 on which the piezoelectric element 300 is formed, that is, on the first electrode 60, the elastic film 50, the insulator film provided as necessary, and the lead electrode 90. A protective substrate 30 having a manifold portion 31 is bonded via an adhesive 35. 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 generating chamber 12, and as described above, the manifold portion 31 is connected to the communication portion 13 of the flow path forming substrate 11. 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 11 may be divided into a plurality of pressure generating chambers 12 and only the manifold portion 31 may be used as a manifold. Further, for example, only the pressure generating chamber 12 is provided on the flow path forming substrate 11, and a member (for example, an elastic film 50, an insulator film provided if necessary) interposed between the flow path forming substrate 11 and the protective substrate 30. ) 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. The piezoelectric element holding part 32 only needs to have a space that does not hinder the movement of the piezoelectric element 300, and the space may be sealed or unsealed.

  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 11, for example, glass, a ceramic material, etc. In this embodiment, the same material as the flow path forming substrate 11 is used. It is formed using a silicon single crystal substrate.

  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 device (not shown in FIGS. 2 to 4), which will be 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. 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. Here, the drive circuit 120 in this embodiment incorporates a temperature detection sensor (not shown in FIGS. 2 to 4) for managing the temperature. This will be described in detail later.

  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 fixed plate 42 is made of a relatively hard material. Since the area 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. Has been.

  In the recording head 10, ink is taken in from an ink introduction port connected to an external ink supply unit (not shown), and the inside is filled with ink from the manifold 100 to the nozzle opening 21. Thereafter, a voltage is applied between each of the first electrode 60 and the second electrode 80 corresponding to the pressure generation chamber 12 in accordance with a drive signal from the drive circuit 120. Thus, the elastic film 50, the adhesion layer 56, the first electrode 60, and the piezoelectric layer 70 are bent and deformed, whereby the ink in each pressure generating chamber 12 vibrates due to the deformation through the elastic film 50 functioning as a vibrating part. To communicate. As a result, the pressure in each pressure generating chamber 12 increases and ink droplets are ejected from the nozzle openings 21.

  FIG. 5 is an enlarged plan view showing the surface of the nozzle plate in an enlarged manner, and FIG. 6 is a sectional view taken along the line BB ′ of FIG. As shown in both figures, as described above, on the surface of the nozzle plate 20, the liquid repellent film 52 whose wettability changes electrochemically based on the gradient of the potential formed by applying a voltage is interposed through the insulating film 51. However, a plurality of pairs (10 pairs in the figure) of electrode pairs 53 are embedded in the liquid repellent film 52. That is, in this embodiment, a central electrode 54 passing through the center line of the nozzle row formed by the plurality of nozzle openings 21 and continuing along the outer periphery of the nozzle opening 21 is arranged in parallel on both sides of the electrode 54. A plurality of provided electrodes 54A1, 54B1, 54C1, 54D1, 54E1, 54A2, 54B2, 54C2, 54D2, and 54E2 are formed. Thus, the electrodes 54A1 to 54E1 and the electrodes 54A2 to 54E2 are formed in both directions (left and right directions) separated from the nozzle openings 21 along a direction perpendicular to the nozzle row.

  The voltage applying means 55 applies a predetermined voltage between the electrodes 54, 54A1 to 54E1, and 54A2 to 54E2 forming each electrode pair 53. Here, in the voltage application means 55, the electrode 54 on the nozzle opening 21 side or the electrodes 54A1 to 54D1 and the electrodes 54A2 to 54D2 of the electrode pairs 53 are negative, and the electrodes 54A1 to 54E1 and electrodes 54A2 to 54E2 on the opposite side are positive. A voltage is applied so that the electrode pair 53 to which the voltage is applied is sequentially separated from the nozzle opening 21 from the electrodes (54, 54A1), (54, 54A2) (left or right direction in the figure) with time. Applied so as to move. That is, first, a predetermined voltage is applied between the electrodes (54, 54A1) and (54, 54A2), and the electrodes to which this voltage is applied are changed from the electrodes (54A1, 54B1), (54A2, 54B2) to the electrodes (54E1, 54D1) and (54E2, 54D2).

  In this embodiment, the wettability of the liquid repellent film 52 changes depending on the voltage gradient formed by the application of voltage. That is, the plus side has lyophilicity (or lyophobic property) and the minus side has lyophobic property (or lyophilic property) with respect to the ink droplets to be attached. As a result, the moving force of the potential from the minus side to the plus side (or from the plus side to the minus side) acts on the ink droplets 57 attached to the liquid repellent film 52. In particular, in this embodiment, since the polarities of the electrodes 54A1 to 54E1 and 54A2 to 54E2 are sequentially switched over time in the direction away from the nozzle opening 21, the ink droplet 57 is indicated by an arrow in FIGS. A driving force that moves in the indicated direction (left-right direction) continuously acts. For example, when the change in wettability of the water-repellent film 52 with respect to the adhered ink droplet 57 is lyophobic on the plus side of the applied voltage and lyophilic on the minus side, the ink droplet 57 is ejected from the nozzle as shown by the solid line in FIGS. A voltage is applied by the voltage applying means 55 so that the electrode 54 is negative and the electrodes 54A1 and 54A2 are positive even if they are attached between the openings 21, and then the electrodes 54A1 and 54A2 are negative and the electrodes 54B1 and 54B2 are positive. When the voltage is sequentially applied to the electrode pair 53 separated from the nozzle opening 21, the ink droplet 57 moves in the direction away from the nozzle opening 21, as indicated by the dotted line in FIGS. Is done. As a result, the ink droplet 57 is separated from the nozzle opening 21 and does not adversely affect the ejection performance of the head.

(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 electrode pair 53 may be a pair in principle. In this case, a voltage is applied so that the nozzle opening 21 side is lyophobic and the opposite side is lyophilic. Also by this, a force that moves in a direction away from the nozzle opening 21 acts on the ink droplets 57, and the ink droplets ejected from the nozzle openings 21 are ejected from the nozzle openings 21 by being isolated from the nozzle openings 21. This is because defects can be prevented in advance. Here, a plurality of pairs of electrode pairs 53 are formed as in the above embodiment, and the ink droplets 53 are switched so that the electrode pairs 53 to which a voltage is applied from the nozzle opening 21 side toward the opposite side are moved over time. 57 can be more reliably excluded from the vicinity of the nozzle opening 21.

  Furthermore, it is also possible to form a groove at the end of the nozzle plate 20 to which the ink droplet 57 is moved to collect the ink droplet 57. In the case of a serial type recording apparatus, the ink droplet 57 moved to the end portion of the nozzle plate 20 is wiped without interrupting the head movement when the head moves to one end portion in the main scanning direction. It can also be configured as follows.

  When the nozzle plate 20 is formed of an insulator, for example, glass ceramics, the insulating film 51 can be omitted. In this case, the electrodes 54A1 to 54E1 and 54A2 to 54E2 may be formed directly on the nozzle plate 20, and the liquid repellent film 52 may be formed on the surface of the nozzle plate 20 so that they are embedded. The shape of the electrode 54 and the like is not limited to that of the above embodiment. It can be made into arbitrary shapes as needed.

  Further, the recording head 10 in the above embodiment has been described as using the thin film type piezoelectric element 300 as a pressure generating means for causing a pressure change in the pressure generating chamber 12, but it is not particularly limited to this. . 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.

  In the embodiment shown in FIG. 1, the recording head units 1A and 1B are mounted on a carriage 3 that moves in a direction (main scanning direction) that intersects 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, a so-called line-type ink jet recording apparatus that performs printing simply by transporting the recording sheet S while the recording head main body is fixed may be used.

  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 recording apparatus (inkjet recording apparatus), 1A, 1B recording head unit, 10 recording head (inkjet recording head), 12 pressure generating chamber, 20 nozzle plate, 21 nozzle opening, 51 insulating film, 52 liquid repellent film, 53 Electrode pair, 54, 54A1 to 54E1, 54A2 to 54E2 electrode, 55 voltage applying means, 57 ink droplet, 300 piezoelectric element

Claims (3)

A liquid ejecting head for causing a pressure change in a liquid in a pressure generating chamber by a pressure generating unit and discharging the liquid in the pressure generating chamber through a nozzle opening formed in a nozzle plate;
A liquid repellent film formed on the surface opposite to the pressure generating chamber of the nozzle plate and capable of electrochemically controlling wettability based on a potential gradient formed by applying a voltage;
A pair of electrodes embedded in the liquid repellent film while maintaining electrical insulation between each other;
The relative positive and negative polarity of the voltage applied to one electrode of the electrode pair, have a, and voltage application means capable of applying an opposite sign polarity voltage to the other electrode,
The liquid ejecting head , wherein the liquid repellent film is composed of an organic molecule having a functional group having a reversible redox ability or an organic molecule having a polynuclear metal complex as a functional group . The liquid ejecting head according to claim 1,
A plurality of electrode pairs are formed;
The voltage applying means is configured to apply voltage to a set of the electrode pair by switching so that the electrode to which the voltage is applied is moved from the nozzle opening side over time. Jet head.   A liquid ejecting apparatus comprising the liquid ejecting head according to claim 1.

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