JP2009220370A - Liquid jet head and liquid jet device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid jet head and a liquid jet device capable of not only effectively preventing nozzle's irregular ejection but also effectively preventing fluid cross talk caused by pressure variation associated with ejection of a droplet. <P>SOLUTION: The liquid jet head includes: a channel unit 16 and a case head 20 that are channel forming members equipped with a pressure generation chamber 11 which is installed to eject ink through respective nozzle apertures 13 by the pressure variation, a dome-shaped reservoir 22 which communicates with the pressure generation chamber 11 so as to supply the ink to the pressure generation chamber 11 and also whose height in a perpendicular direction is gradually decreased toward a part communicating with the pressure generation chamber 11, and space 60 which is air bubble accumulation formed by communicating with the reservoir 22; and a piezoelectric element 17 disposed corresponding to the pressure generation chamber 11 and deformed when a driving signal is supplied thereto, so as to cause the pressure variation in liquid in the pressure generation chamber 11. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquid ejecting head and a liquid ejecting apparatus that eject liquid from nozzle openings, and is particularly useful when applied to an ink jet recording head and an ink jet recording apparatus that eject ink as liquid.

  As an ink jet recording head which is an example of a liquid ejecting head, for example, an actuator unit provided with a piezoelectric element and a pressure generating chamber, a nozzle plate provided with a nozzle opening communicating with the pressure generating chamber and discharging ink, Some have a flow path unit provided with a reservoir serving as a common ink chamber for the pressure generation chamber.

  In this type of ink jet recording head, a mechanism for absorbing pressure fluctuations at the time of ejection of ink droplets is required in a reservoir portion which is a common ink chamber for reducing fluid crosstalk. For this reason, a compliance portion is formed which can easily vibrate by weakening mechanical rigidity, for example, by thinning a part of a member closing the reservoir (for example, see Patent Document 1).

  However, as in Patent Document 1, when the upper surface of the reservoir is formed in the same plane as the upper surface of the liquid supply path that communicates the pressure generation chamber and the reservoir, bubbles stay at the boundary between the reservoir and the liquid supply path. There is a problem that nozzle missing occurs easily depending on the size of the retained bubbles.

  As a measure for solving such a problem, it has been proposed to use a dome-shaped reservoir whose height gradually decreases toward the boundary with the liquid supply path (see, for example, Patent Document 2 and Patent Document 3).

JP 2002-355961 A JP 2001-129777 A (paragraphs 0110 to 0113, FIG. 33) Japanese Patent Laying-Open No. 2005-131791 (FIG. 4)

  Since the reservoir is formed in a dome shape as described above, the bubbles can be separated from the liquid supply path, so that the risk of nozzle missing is reduced. However, since it is difficult to form the compliance region in the vicinity of the liquid supply path as in the case of Patent Document 1, a new problem arises that fluid crosstalk occurs between adjacent pressure generation chambers.

  Such a problem exists not only in an ink jet recording head but also 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 prevent nozzle omission, and at the same time, can effectively reduce fluid crosstalk caused by pressure fluctuations associated with droplet ejection. An object is to provide an injection device.

  An aspect of the present invention that solves the above problems is a pressure generation chamber that is installed so as to discharge liquid through each nozzle opening due to pressure fluctuation, and communicates with the pressure generation chamber so as to supply the liquid to the pressure generation chamber. And a flow path forming member comprising a dome-shaped flow path whose height in the vertical direction gradually decreases toward a portion communicating with the pressure generating chamber, and a space serving as a bubble reservoir formed in communication with the flow path. The liquid ejecting head includes pressure generating means disposed corresponding to the pressure generating chamber and deformed by supply of a drive signal to cause pressure fluctuation in the liquid in the pressure generating chamber.

  According to this aspect, it is possible to absorb the pressure fluctuation in the flow path due to the back pressure accompanying the discharge of the liquid droplets through the nozzle opening due to the deformation of the pressure generating means by the bubble accumulation in the space. That is, it can function as a compliance that absorbs pressure fluctuations by actively utilizing bubbles. As a result, the problem in the case of providing a compliance part that weakens the mechanical rigidity can be solved at once. Specifically, the structural complexity associated with forming the thin portion can be avoided, and the structural crosstalk associated with the presence of the mechanically weak portion can be satisfactorily suppressed.

  On the other hand, bubbles generated in the reservoir reach the top along the ceiling of the dome-shaped reservoir. That is, since the bubbles float on the top of the reservoir away from the inlet portion of the ink supply path, they do not stay at the inlet portion of the ink supply path. As a result, nozzle omission can be effectively prevented.

  Here, the flow path can be suitably configured by a reservoir that constitutes a common liquid chamber provided across the direction in which the pressure generating chambers are arranged side by side. In this case, the pressure fluctuation can be accurately suppressed by the bubble accumulation in the reservoir portion which is a common liquid chamber. As a result, fluid crosstalk can be satisfactorily suppressed. At the same time, since the bubbles float on the top of the reservoir, it is possible to effectively prevent the nozzles from dropping due to the retention of bubbles.

  The space is a flow in which the pressure generation chamber is formed adjacent to a liquid supply path that communicates between the reservoir and the pressure generation chamber in the flow path forming substrate in which the pressure generation chamber is formed. It can be suitably provided on the path forming substrate. In this case, since the compliance part by the bubble accumulation is formed in the vicinity of the adjacent pressure generation chamber, fluid crosstalk can be satisfactorily prevented. Furthermore, the space may be formed as a concave portion from the flow path forming substrate in which the pressure generating chamber is formed toward the nozzle plate having the nozzle openings. Also in this case, since the compliance part by the bubble accumulation is formed in the vicinity of the adjacent pressure generation chamber, the fluid crosstalk can be satisfactorily prevented.

  The space is formed in the flow path forming substrate adjacent to a liquid supply path that communicates between the reservoir and the pressure generating chamber in the flow path forming substrate in which the pressure generating chamber is formed, and It can also be formed as a recess from the flow path forming substrate toward the nozzle plate side having the nozzle openings. In this case, when the volume of the space provided in the flow path forming substrate cannot be sufficiently increased, it is useful for adjustment for obtaining the optimum compliance by complementing the shortage of the volume.

  Furthermore, a plurality of the spaces can be assigned corresponding to a plurality of pressure generating chambers. In this case, the opening area when providing the space can be adjusted as appropriate. As a result, by making the opening area according to the surface tension of the liquid droplets, the space can be surely stored as a bubble, ensuring the required compliance, and providing the beam can also ensure the strength of the member providing the space. .

  According to another aspect of the invention, there is provided a liquid ejecting apparatus including the liquid ejecting head as described above. According to this aspect, both the fluid crosstalk and the structural crosstalk can be suppressed and high quality printing can be performed. As a result, the printing quality can be improved.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(Embodiment)
FIG. 1 is a cross-sectional view of an ink jet recording head which is an example of a liquid jet head according to an embodiment of the present invention. As shown in the figure, an ink jet recording head 10 includes a flow path forming substrate 12 having a plurality of pressure generating chambers 11 and a nozzle plate 14 in which a plurality of nozzle openings 13 communicating with the pressure generating chambers 11 are formed. And a flow path unit 16 including a vibration plate 15 provided on the surface of the flow path forming substrate 12 opposite to the nozzle plate 14. Furthermore, a piezoelectric element unit 18 having a piezoelectric element 17 provided in a region corresponding to each pressure generating chamber 11 on the vibration plate 15, and an accommodating portion 19 that is fixed on the vibration plate 15 and accommodates the piezoelectric element unit 18. And a case head 20.

  In the flow path forming substrate 12, a plurality of pressure generating chambers 11 are partitioned by a partition wall and arranged in parallel in the width direction on the surface layer portion on one side. For example, in this embodiment, a plurality of pressure generating chambers 11 are arranged in parallel on the flow path forming substrate 12. A reservoir 22 to which ink is supplied via a liquid inlet 21 communicating with ink supply means (not shown) outside the case head 20 is provided outside the row of the pressure generating chambers 11. Through the thickness direction. The reservoir 22 and each pressure generation chamber 11 communicate with each other via an ink supply path 23, and ink is supplied to each pressure generation chamber 11 from the ink supply means via the liquid inlet 21 and the reservoir 22. .

  Here, the reservoir 22 in this embodiment is formed in a dome shape whose height gradually decreases toward a portion communicating with the pressure generating chamber 11, that is, a boundary portion with the ink supply path 23. For this reason, the reservoir 22 is formed as a flow path extending from the flow path forming substrate 12 through the diaphragm 15 to a part of the case head 20, and a lower end portion of the liquid introduction port 21 is opened at the top. . As a result, the bubbles 44 formed in the reservoir 22 are lighter than the ink filled in the reservoir 22, and therefore reach the top along the dome-shaped ceiling. That is, it does not stay at the inlet of the ink supply path 23. Here, in this embodiment, the dome is formed so that the heights of both at the boundary between the reservoir 22 and the ink supply path 23 are the same. As a result, even if bubbles are generated at the inlet portion of the ink supply path 23, the bubbles quickly move toward the top of the reservoir 22 without staying in the portion.

  The ink supply path 23 is formed with a narrower width than the pressure generation chamber 11, and plays a role of keeping constant the flow path resistance of the ink flowing from the reservoir 22 into the pressure generation chamber 11. Further, a nozzle communication hole 24 penetrating the flow path forming substrate 12 is formed on the end side of the pressure generating chamber 11 opposite to the reservoir 22. In other words, in this embodiment, the pressure generation chamber 11, the reservoir 22, the ink supply path 23, and the nozzle communication hole 24 are provided as the liquid flow path in the flow path forming substrate 12. Such a flow path forming substrate 12 is made of a silicon single crystal substrate, and the pressure generating chamber 11 and the like provided in the flow path forming substrate 12 are formed by etching the flow path forming substrate 12.

  A nozzle plate 14 having nozzle openings 13 is bonded to one surface side of the flow path forming substrate 12 via an adhesive 50, and each nozzle opening 13 is connected to a nozzle communication hole provided in the flow path forming substrate 12. Each pressure generating chamber 11 is communicated with each other via 24. On the other hand, the diaphragm 15 is bonded to the other surface side of the flow path forming substrate 12, that is, the opening surface side of the pressure generating chamber 11. Each pressure generating chamber 11 is sealed by the vibration plate 15. Here, the vibration plate 15 is formed of a composite plate of an elastic film 25 made of an elastic member such as a resin film and a support plate 26 made of, for example, a metal material that supports the elastic film 25 and is elastic. The membrane 25 side is bonded to the flow path forming substrate 12 with an adhesive 51. In addition, an island portion 27 with which the tip end portion of the piezoelectric element 17 abuts is provided in a region of the vibration plate 15 facing each pressure generation chamber 11. The front end surface of the piezoelectric element 17 is bonded to the island portion 27 with an adhesive 28.

  The piezoelectric element 17 is integrally formed in one piezoelectric element unit 18. That is, a piezoelectric element forming member 34 in which the piezoelectric material 31 and the electrode forming materials 32 and 33 are vertically sandwiched and laminated is formed to correspond to each pressure generating chamber 11. Each piezoelectric element 17 is formed by cutting into comb teeth. An inactive region that does not contribute to the vibration of the piezoelectric element 17 (piezoelectric element forming member 34), that is, the base end side of the piezoelectric element 17 is fixed to the fixed substrate 35. In this embodiment, the piezoelectric element unit 18 is constituted by the piezoelectric element 17 (piezoelectric element forming member 34) and the fixed substrate 35. In the vicinity of the base end portion of the piezoelectric element 17, a circuit board 37 having a wiring 36 for supplying a signal for driving each piezoelectric element 17 is connected to the surface opposite to the fixed board 35.

  Such a piezoelectric element unit 18 is fixed in a state where the distal end portion of the piezoelectric element 17 is in contact with the island portion 27 of the diaphragm 15 as described above. For example, in this embodiment, the case head 20 is fixed on the diaphragm 15 as described above, and the piezoelectric element unit 18 is accommodated in the accommodating portion 19 of the case head 20 and the piezoelectric element 17 is fixed. The fixed substrate 35 thus fixed is fixed to the case head 20 on the side opposite to the piezoelectric element 17. Specifically, a stepped portion 38 is provided in the accommodating portion 19 of the case head 20, and the fixed substrate 35 is bonded to the stepped portion 38 of the case head 20 with an adhesive 39.

  Further, a wiring board 41 provided with a plurality of conductive pads 40 to which the respective wirings 36 of the circuit board 37 are connected is fixed on the case head 20. 41 is substantially blocked. The wiring board 41 is formed with a slit-like opening 42 in a region facing the housing part 19 of the case head 20, and the circuit board 37 is drawn out of the housing part 19 from the opening 42 of the wiring board 41. It is.

  Moreover, the circuit board 37 which comprises the piezoelectric element unit 18 consists of chip-on-film (COF) in which the drive IC (not shown) for driving the piezoelectric element 17 was mounted in this embodiment, for example. Each wiring 36 of the circuit board 37 is connected to the electrode forming materials 32 and 33 constituting the piezoelectric element 17 by, for example, solder, anisotropic conductive agent, or the like on the base end side. On the other hand, each wiring 36 is joined to each conductive pad 40 of the wiring board 41 on the tip side. Specifically, each wiring 36 is connected to the wiring board 41 in a state in which the tip of the circuit board 37 drawn out of the housing part 19 from the opening 42 of the wiring board 41 is bent along the surface of the wiring board 41. The conductive pads 40 are joined to each other.

  In this embodiment, a part of the support plate 26 is removed by conventional etching, and the formation region of the reservoir 22 is extended to the case head 20 through the configuration region of the compliance portion that is substantially constituted only by the elastic film 25. ing. As a result, the conventional compliance portion as described above has been removed, but instead, a space 60 for storing bubbles is provided in the reservoir 22.

  Here, FIG. 2 which is a sectional view taken along line AA ′ of FIG. 1 and FIG. 3 which is an enlarged sectional view taken along line BB ′ of FIG. As shown in FIGS. 1 to 3, the space 60 is open at one end at a position adjacent to the ink supply path 23 below the ink supply path 23, and is parallel to the ink supply path 23 and the pressure generation chamber 11. The other end of the flow path forming substrate 12 is closed. Here, the relationship between the surface tension of the ink and the cross-sectional area of the opening of the space 60 is adjusted so that the space 60 is not filled with ink. As a result, the space 60 can be a bubble reservoir. The bubbles retained in the bubble reservoir can function as a suitable compliance that absorbs vibrations caused by pressure waves propagated from the pressure generation chamber 11. In this embodiment, one space 60 is allocated to a plurality (eight in the figure) of ink supply paths 23. Of course, one space 60 may be assigned to each ink supply path 23. However, manufacturing is easier when the number of spaces 60 is reduced and more ink supply paths 23 are made to correspond to one space 60 within the range permitted by the mechanical strength of the flow path forming substrate 12.

  According to the present embodiment as described above, ink droplets can be ejected by changing the volume of each pressure generating chamber 11 by deformation of the piezoelectric element 17 and the diaphragm 15. Specifically, when ink is supplied from an ink cartridge (not shown) to the reservoir 22 through the liquid inlet 21, the ink is distributed from the ink supply path 23 to each pressure generating chamber 11. Thus, the piezoelectric element 17 is contracted by applying a voltage to the piezoelectric element 17 in a state where each pressure generating chamber 11 is filled with ink. As a result, the diaphragm 15 is deformed together with the piezoelectric element 17 to expand the volume of the pressure generating chamber 11, and ink is drawn into the pressure generating chamber 11. After the ink is filled up to the nozzle opening 13, the voltage applied to the electrode forming materials 32 and 33 of the piezoelectric element 17 is released according to a recording signal supplied via the wiring board. As a result, the piezoelectric element 17 is expanded to return to the original state, and the diaphragm 15 is also displaced to return to the original state. As a result, the volume of the pressure generation chamber 11 contracts, the pressure in the pressure generation chamber 11 increases, and ink droplets are ejected from the nozzle openings 13. At this time, the pressure fluctuation caused by the back pressure at the time of discharge is propagated in the reservoir 22, but the pressure fluctuation is well absorbed by the bubble pool in the space 60. This is because the bubbles in the bubble reservoir function as compliance. In other words, in the present embodiment, it is possible to replace the conventional compliance unit by actively using bubbles.

  On the other hand, the bubbles 44 generated in the reservoir 22 reach the top along the ceiling of the dome-shaped reservoir 22. That is, the bubbles 44 float on the top of the reservoir 22 away from the inlet portion of the ink supply path 23 and therefore do not stay at the inlet portion of the ink supply path 23. As a result, nozzle omission can be effectively prevented.

  4 and 5 are cross-sectional views of the principal part showing modifications of the structure of the space portion in the present embodiment. A space 61 shown in FIG. 4 is formed in the nozzle plate 14 as a recess from the flow path forming substrate 12 toward the nozzle plate 14. More specifically, the space 61 is a recess provided in the nozzle plate 14 below the ink supply path 23 and the pressure generation chamber 11, and one end of the space 61 opens at the bottom of the reservoir 22 through the opening 62 and the other end. Is closed. The relationship between the surface tension of the ink and the opening area of the opening 62 in the space 61 is adjusted so that the space 61 is not filled with ink. As a result, the space 61 can be used as a bubble reservoir, and the bubbles in the bubble reservoir function as a suitable compliance that absorbs vibrations caused by pressure waves propagated from the pressure generation chamber 11. Thus, a space 61 that exhibits the same function as the space 60 shown in FIGS. 1 to 3 can also be formed in the nozzle plate 14.

  In addition to the space 60, the space 63 shown in FIG. 5 is formed by forming a recess 64 in the nozzle plate 14 from the flow path forming substrate 12 toward the nozzle plate. More specifically, the space 63 has a concave portion 64 provided in the nozzle plate 14 integrated therewith together with the space 60. Here, the space 63 opens into the reservoir 22 only through an opening at one end of the space 60. Thus, the recess 64 functions to complement the volume of the space 60. The space 63 of this example is useful for adjustment for obtaining the optimum compliance by complementing the shortage of the volume when the volume of the space 60 cannot be increased sufficiently.

(Other embodiments)
In the above embodiment, the space 60 serving as a bubble reservoir is provided in the reservoir 22, but the present invention is not limited to this. Basically, any flow path that communicates with the pressure generation chamber 11 and that propagates the pressure fluctuation in the pressure generation chamber 11 may be used. Further, the space 60 need not be provided adjacent to the ink supply path 23. However, if it is close to the ink supply path 23, the pressure fluctuation propagated through the ink supply path 23 can be absorbed quickly and the fluid crosstalk can be accurately suppressed.

  In the above-described embodiment, an ink jet recording head having a longitudinal vibration type piezoelectric element in which piezoelectric materials and electrode forming materials are alternately stacked to expand and contract in the axial direction has been described. For example, the type of ink jet recording head is not limited. For example, an ink jet recording head having a thick film type piezoelectric element, for example, an ink jet recording head having a thin film type piezoelectric element having a piezoelectric material formed by a sol-gel method, a MOD method, a sputtering method, etc. An ink jet recording head with a so-called electrostatic actuator that arranges electrodes with a predetermined gap and controls the vibration of the diaphragm with electrostatic force. A heating element is placed in the pressure generation chamber and generated by the heat generated by the heating element. The same effect can be obtained even with an ink jet recording head that ejects liquid droplets from the nozzle openings using bubbles.

  In addition, the ink jet recording head according to the above embodiment constitutes a part of a recording head unit including a liquid introduction port communicating with an ink cartridge or the like, and is mounted on the ink jet recording apparatus. FIG. 6 is a schematic view showing an example of the ink jet recording apparatus. As shown in the figure, recording head units 1A and 1B having ink jet recording heads are provided with cartridges 2A and 2B constituting ink supply means in a detachable manner, and a carriage 3 on which the recording head units 1A and 1B are mounted. Is provided on a carriage shaft 5 attached to the apparatus body 4 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.

  The driving force of the driving motor 6 is transmitted to the carriage 3 via a plurality of gears and 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 paper feed roller (not shown) is wound around the platen 8. It is designed to be transported.

  In the above-described embodiment, an ink jet recording head has been described as an example of a liquid ejecting head. However, the present invention is widely intended for all liquid ejecting heads and ejects liquids other than ink. Of course, the present invention can also be applied to an inspection method for a liquid jet head. 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.

FIG. 3 is a cross-sectional view of the liquid jet head according to the embodiment of the invention. It is the sectional view on the AA 'line of FIG. It is a BB 'line expanded sectional view of FIG. It is principal part sectional drawing which shows the modification of the structure of the space part in the said embodiment. It is principal part sectional drawing which shows the modification of the structure of the space part in the said embodiment. 1 is a schematic view of an ink jet recording apparatus according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Inkjet recording head, 11 Pressure generation chamber, 12 Flow path formation board | substrate, 13 Nozzle opening, 14 Nozzle plate, 15 Diaphragm, 16 Flow path unit, 17 Piezoelectric element, 18 Piezoelectric element unit, 20 Case head, 22 Reservoir, 44 bubbles, 60, 61, 63 spaces

Claims (7)

A pressure generating chamber installed to discharge liquid through each nozzle opening due to pressure fluctuation, a portion communicating with the pressure generating chamber to supply the liquid to the pressure generating chamber and a portion communicating with the pressure generating chamber A flow path forming member comprising a flow path that forms a dome shape whose height in the vertical direction gradually decreases, and a space that becomes a bubble reservoir formed in communication with the flow path;
A liquid ejecting head comprising pressure generating means disposed corresponding to the pressure generating chamber and deformed by supply of a drive signal to cause pressure fluctuation in the liquid in the pressure generating chamber. The liquid ejecting head according to claim 1,
The liquid ejecting head according to claim 1, wherein the flow path is a reservoir that constitutes a common liquid chamber provided in a direction in which the pressure generating chambers are arranged side by side. The liquid ejecting head according to claim 2,
The liquid ejecting head according to claim 1, wherein the space is provided on a flow path forming substrate in which the pressure generation chamber is formed adjacent to a liquid supply path communicating between the reservoir and the pressure generation chamber. The liquid ejecting head according to claim 2,
The liquid ejecting head according to claim 1, wherein the space is formed as a concave portion from the flow path forming substrate in which the pressure generation chamber is formed toward the nozzle plate side having the nozzle openings. The liquid ejecting head according to claim 2,
The space is formed in the flow path forming substrate adjacent to a liquid supply path that communicates between the reservoir and the pressure generating chamber in the flow path forming substrate in which the pressure generating chamber is formed, and the flow path A liquid ejecting head, wherein the liquid ejecting head is formed as a concave portion from the forming substrate toward the nozzle plate side having the nozzle openings. In the liquid jet head according to any one of claims 2 to 5,
The liquid ejecting head according to claim 1, wherein a plurality of the spaces are assigned in correspondence with a plurality of pressure generating chambers.   A liquid ejecting apparatus comprising the liquid ejecting head according to claim 1.

Images