JP2009143002A - Liquid jet head and liquid jet apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid jet head which can effectively prevent generation of a leakage current from a bonding wire part. <P>SOLUTION: The liquid jet head I includes a pressure generating element 300 prepared correspondingly to a pressure generation chamber 12 which communicates with a nozzle opening 21 that jets the liquid, a driving IC 120 for driving the pressure generating element 300, and a bonding wire 130 which electrically connects the driving IC 120 and a lead electrode 90 led out of the pressure generating element 300. An insulating film 400 of an inorganic insulating material is formed to at least a surface of the bonding wire 130. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid ejecting head and a liquid ejecting apparatus, and more particularly, to an ink jet recording head that ejects ink droplets by displacement of a pressure generating element provided corresponding to a pressure generating chamber communicating with a nozzle opening that ejects ink droplets. It is useful.

  Some liquid ejecting heads are provided with pressure generating elements such as piezoelectric elements and heat generating elements corresponding to pressure generating chambers communicating with nozzle openings for discharging ink droplets. As a liquid ejecting head using a piezoelectric element as a pressure generating element, for example, a part of a pressure generating chamber communicating with a nozzle opening for ejecting ink droplets is constituted by a vibration plate, and the vibration plate is deformed by the piezoelectric element to generate pressure There is an ink jet recording head that pressurizes ink in a generation chamber and ejects ink droplets from nozzle openings. Two types of ink jet recording heads have been put into practical use, one using a longitudinal vibration mode piezoelectric actuator that expands and contracts in the axial direction of the piezoelectric element and one using a flexural vibration mode piezoelectric actuator. . For example, an actuator in a flexural vibration mode is used. For example, a uniform piezoelectric material layer is formed over the entire surface of the diaphragm by a film formation technique, and this piezoelectric material layer is applied to a pressure generation chamber by a lithography method. A piezoelectric element is known that is divided into shapes to be formed and is independent for each pressure generating chamber.

  Further, such an ink jet recording head requires a drive IC (semiconductor integrated circuit) for driving the piezoelectric element. This driving IC is mounted on a bonding substrate that is bonded to a flow path forming substrate in which a pressure generating chamber is formed, for example, a fixing member that structurally holds and fixes a head chip, and is electrically connected to each piezoelectric element by wire bonding. A connecting structure is adopted. The driving IC and the bonding wire are protected by being covered with a mold (see Patent Document 1). That is, a resin called a potting agent is filled in an IC holding portion that is a space surrounding the driving IC of the head case.

JP 2000-135790 A (Figs. 5-8, 11, 12, 14)

  However, since the potting agent made of an organic insulating material absorbs a lot of moisture, current leakage from the bonding wire portion may occur due to this. This is because the adjacent bonding wires may be short-circuited through the potting agent moisture.

  Alternatively, when the head case is provided, the bonding wire and the head case may be short-circuited through the potting agent moisture. Incidentally, the head case is usually made of SUS which is a conductor.

  SUMMARY An advantage of some aspects of the invention is that it provides a liquid ejecting head and a liquid ejecting apparatus that can effectively prevent generation of a leakage current from a bonding wire portion.

One embodiment of the present invention for achieving the above object is as follows.
A pressure generating element provided corresponding to a pressure generating chamber communicating with a nozzle opening for injecting a liquid; a driving IC for driving the pressure generating element; a lead wiring drawn from the pressure generating element; and the driving A liquid ejecting head comprising a bonding wire for electrically connecting an IC,
In the liquid ejecting head, an insulating film made of an inorganic insulating material is formed on at least the surface of the bonding wire.
According to this aspect, it is possible to satisfactorily prevent current leakage between adjacent bonding wires and between each bonding wire and the head case. Therefore, stable characteristics are ensured for a long time even when used in a high humidity environment.

  Here, a head case made of a conductive material in which an IC holding portion that is a space surrounding the drive IC is provided penetrating in the thickness direction, and the insulating film is formed on the inner peripheral surface of the head case and the head case. It may be formed on the surface of the driving IC. As a result, current leakage between each bonding wire and the head case can be satisfactorily prevented. The leakage of the current can be prevented even better.

  The insulating film can be suitably formed by a CVD method. In this case, the predetermined insulating film can be deposited well on the entire necessary part without causing physical damage to the film forming part and also by wrapping around the shadow part.

  The IC holding unit may be filled with a potting agent made of an organic insulating film material on the insulating film to constitute a liquid ejecting head. In this case, coupled with the function of the insulating film, it is possible not only to prevent contamination and damage of the bonding wire portion but also to relieve stress.

According to another aspect of the invention, there is provided a liquid ejecting apparatus including the liquid ejecting heads described above.
According to this aspect, it is possible to prevent the leakage of current from the bonding wire portion and to obtain a liquid ejecting apparatus having good characteristics for a long time.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1 is an exploded perspective view showing an ink jet recording head according to the present embodiment, FIG. 2 is a plan view of FIG. 1, and FIG. 3 is a cross-sectional view taken along the line AA ′ of FIG. is there. As shown in these drawings, the flow path forming substrate 10 is made of a silicon single crystal substrate having a plane orientation (110), and one surface thereof is made of silicon dioxide previously formed by thermal oxidation, and has a thickness of 0.5. An elastic film 50 of ˜2 μm is formed. The flow path forming substrate 10 is provided with two rows in which a plurality of pressure generating chambers 12 are arranged in the width direction. Further, a communication portion 13 is formed for each row of the pressure generation chambers 12 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 the pressure generation chamber 12 are connected to the ink supply path 14. It is communicated via. The communication part 13 constitutes a part of a reservoir that communicates with a reservoir part of a protective substrate, which will be described later, and serves as a common ink chamber for the pressure generating chambers 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.

  Further, on the opening surface side of the flow path forming substrate 10, a nozzle plate 20 having 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 provided with an adhesive or It is fixed via a heat welding film or the like.

  On the other hand, as described above, the elastic film 50 having a thickness of, for example, about 1.0 μm is formed on the side opposite to the opening surface of the flow path forming substrate 10. For example, an insulator film 55 having a thickness of about 0.4 μm is formed. Further, on the insulator film 55, a lower electrode film 60 having a thickness of, for example, about 0.2 μm, a piezoelectric layer 70 having a thickness of, for example, about 1.0 μm, and a thickness of, for example, about 0 A 0.05 μm upper electrode film 80 is laminated to form a piezoelectric element 300 as a pressure generating element provided corresponding to the pressure generating chamber 12 communicating with the nozzle opening 21 for ejecting ink. Here, the piezoelectric element 300 refers to a portion including the lower electrode film 60, the piezoelectric layer 70, and the upper electrode film 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 lower electrode film 60 is a common electrode of the piezoelectric element 300 and the upper electrode film 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. In the present embodiment, the elastic film 50, the insulator film 55, and the lower electrode film 60 constitute a diaphragm. A lead electrode 90 is connected to the vicinity of one end of the upper electrode film 80 of each piezoelectric element 300. The lead electrode 90 extends to the vicinity of the central portion of the flow path forming substrate 10 and is electrically connected to a driving IC 120 mounted on a protective substrate 30 described later by a bonding wire 130.

  On the flow path forming substrate 10 on which such a piezoelectric element 300 is formed, there is a piezoelectric element holding portion 31 capable of ensuring a space that does not hinder its movement in a region facing the piezoelectric element 300, and a protective substrate 30 is bonded via an adhesive 35. Since the piezoelectric element 300 is formed in the piezoelectric element holding part 31, it is protected in a state hardly affected by the external environment. In addition, although the piezoelectric element holding | maintenance part 31 may be sealed, it does not need to be sealed by providing the fine communicating hole connected with the exterior. Moreover, the piezoelectric element holding | maintenance part 31 is provided for every row | line | column of the piezoelectric element 300 arranged in parallel by this form.

  A reservoir portion 32 constituting at least a part of the reservoir 110 is provided outside the piezoelectric element holding portions 31 of the protective substrate 30. These reservoir portions 32 are provided across the width direction of the pressure generating chamber 12 through the protective substrate 30 in the thickness direction, and are communicated with the communicating portion 13 of the flow path forming substrate 10 to each pressure generating chamber. Each of the reservoirs 110 is a common ink chamber for each of the 12 columns. In this embodiment, in the region between the piezoelectric element holding portions 31 of the protective substrate 30, through holes 33 that penetrate the protective substrate 30 in the thickness direction are provided corresponding to the rows of the piezoelectric elements 300. Yes. The lead electrode 90 drawn from each piezoelectric element 300 is exposed in the through hole 33 in the vicinity of its end. In addition, 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, a ceramic material, etc., and in this embodiment, the same as the flow path forming substrate 10 It was formed using a silicon single crystal substrate of the material.

  A driving IC (semiconductor integrated circuit) 120 for driving the piezoelectric element 300 is provided on the surface of the protective substrate 30, that is, the surface opposite to the bonding surface with the flow path forming substrate 10. Implemented for each column. Each drive IC 120 and the lead electrode 90 are electrically connected by a bonding wire 130 in the through hole 33 of the protective substrate 30. In this embodiment, the lead electrode 90 is a lead-out wiring drawn from each piezoelectric element 300. Further, the flexible flat cable (FFC) 112 and each driving IC 120 are electrically connected by bonding wires 114.

  Further, a compliance substrate 40 including a sealing film 41 and a fixing plate 42 is bonded on the protective substrate 30 so as to surround a peripheral portion including a region corresponding to the reservoir portion 32. Here, the sealing film 41 is made of a material having low rigidity and flexibility (for example, a polyphenylene sulfide (PPS) film having a thickness of 6 μm), and the sealing film 41 seals one surface of the reservoir portion 32. It has been stopped. The fixing plate 42 is made of a hard material such as metal (for example, stainless steel (SUS) having a thickness of 30 μm). Since the region of the fixing plate 42 facing the reservoir 110 is an opening 43 that is completely removed in the thickness direction, one surface of the reservoir 110 is sealed only by the flexible sealing film 41. Has been.

  In this embodiment, the head case 200 having an IC holding portion 151 that is a space surrounding the drive IC 120 on the protective substrate 30 and having a thickness of, for example, 2 to 3 mm is bonded via an adhesive (not shown). . Here, the head case 200 is bonded to a compliance substrate 40 provided on the protective substrate 30. The head case 200 is usually made of a conductive material such as metal, and the IC holding portion 151 is provided so as to penetrate the head case 200 in the thickness direction. The head case 200 has one end connected to an ink cartridge (not shown) and the other end formed with an ink communication hole 202 connected to the reservoir 110. The ink communication hole 202 is connected to the reservoir 110 through the ink communication hole 202. Is to be supplied.

  Further, an insulating film 400 of an inorganic insulating material is formed on the surfaces of the bonding wires 114 and 130, the inner peripheral surface of the head case 200, and the surface of the driving IC 120, that is, the portion facing the IC holding portion 151. This insulating film 400 can be suitably formed by a CVD method. Note that since the insulating film 400 is for preventing current leakage from the bonding wires 114 and 130, it is sufficient that the insulating film 400 be formed at least on the surfaces of the bonding wires 114 and 130 serving as charging portions. However, when the insulating film 400 is formed as in this embodiment, the most stable current leakage prevention structure is obtained.

  In this embodiment, the potting agent 250 made of an organic insulating material is filled in the IC holding portion 151 after the insulating film 400 is formed so as to cover the driving IC 120 and the bonding wires 114 and 130. The kind of the potting agent 250 is not particularly limited. For example, there are silicone resins, urethane resins, and the like. When the potting agent 250 is filled in this way, not only can the contamination and damage of the bonding wires 114, 130, etc. be prevented in combination with the function of the insulating film 400, but also the stress of the portions can be relieved. Can be realized. This is because the bonding wires 114 and 130 can be fixed so as not to move.

  In the ink jet recording head I of this embodiment, ink is taken in from an external ink supply unit such as an ink cartridge through the ink communication hole 202 provided in the head case 200. Then, after filling the interior from the reservoir 110 to the nozzle opening 21 with ink, it is driven between the lower electrode film 60 and the upper electrode film 80 corresponding to the pressure generating chamber 12 in accordance with a drive signal from the drive IC 120. A voltage is applied, and the pressure in each pressure generating chamber 12 is increased by the elastic film 50, the lower electrode film 60 and the piezoelectric layer 70, and ink droplets are ejected from the nozzle openings 21.

  Here, a method of manufacturing the ink jet recording head I as described above will be described with reference to FIGS. 4 to 7 are cross-sectional views of the pressure generating chamber 12 in the longitudinal direction. First, the flow path forming substrate 10 made of a silicon single crystal substrate is thermally oxidized in a diffusion furnace at about 1100 ° C. to form an elastic film 50 and a silicon dioxide film 52 serving as a protective film on the surface.

  Next, as shown in FIG. 4A, an insulator film 55 made of zirconium oxide is formed on the elastic film 50 (silicon dioxide film 52). Next, as shown in FIG. 4B, for example, platinum and iridium are stacked on the insulator film 55 to form the lower electrode film 60, and then the lower electrode film 60 is patterned into a predetermined shape. Thereafter, for example, the piezoelectric layer 70 made of lead zirconate titanate (PZT) is formed by using, for example, a sol-gel method. The method for manufacturing the piezoelectric layer 70 is not limited to the sol-gel method, and for example, a MOD (Metal-Organic Decomposition) method or the like may be used.

  Next, an upper electrode film 80 made of, for example, iridium is formed on the entire surface of the flow path forming substrate 10. Next, as shown in FIG. 4C, the piezoelectric layer 300 and the upper electrode film 80 are patterned in a region facing each pressure generating chamber 12 to form the piezoelectric element 300. Next, as shown in FIG. 4D, a lead electrode 90 made of, for example, gold (Au) or the like is formed over the entire surface of the flow path forming substrate 10, and then a mask pattern made of, for example, a resist (not shown). ) To pattern each piezoelectric element 300.

  Next, as shown in FIG. 5A, a protective substrate 30 having a piezoelectric element holding portion 31 and a reservoir portion 32 formed of a silicon single crystal substrate in advance on the piezoelectric element 300 side of the flow path forming substrate 10 is provided. Bonded on the flow path forming substrate 10 via an adhesive 35. Subsequently, a protective film is formed by patterning the silicon dioxide film opposite to the surface on which the piezoelectric element 300 of the flow path forming substrate 10 is formed into a predetermined shape, and the flow path forming substrate 10 is formed using this protective film as a mask. By performing anisotropic etching (wet etching) using an alkaline solution such as KOH, the pressure generating chamber 12, the communication part 13, the ink supply path 14, and the like are formed on the flow path forming substrate 10. Thereafter, a nozzle plate 20 having a nozzle opening 21 is bonded to the surface of the flow path forming substrate 10 opposite to the protective substrate 30 to close the pressure generating chamber 12, the communication portion 13, the ink supply path 14, and the like. .

  Next, as shown in FIG. 5B, the compliance substrate 40 is bonded to the protective substrate 30.

  Next, as shown in FIG. 6A, the drive IC 120 is mounted on the protective substrate 30. Specifically, the driving IC 120 is bonded onto the protective substrate 30, and the driving IC 120 and the lead electrode 90 are connected by the bonding wire 130 by wire bonding.

  Next, as shown in FIG. 6B, the head case 200 provided with the IC holding portion 151 is joined to the compliance substrate 40 fixed on the protective substrate 30.

  Thereafter, as shown in FIG. 7A, an insulating film 400 is formed by a CVD method on a portion facing the IC holding portion 151.

  Next, as shown in FIG. 7B, a potting agent 250 containing a silicone resin as a main agent is filled from, for example, a nozzle needle (not shown) from the opening opposite to the protective substrate 30 of the IC holding portion 151.

  By manufacturing the liquid ejecting head I in this manner, current leakage between the bonding wires 114 and 130 and between the bonding wires 114 and 130 and the head case 200 can be effectively prevented for a long time.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to embodiment mentioned above.

  For example, in the above-described embodiment, a thin film type liquid jet head manufactured by applying a film forming and lithography process is taken as an example. However, the present invention is not limited to this, and for example, a green sheet is attached. The present invention can also be applied to a thick film type liquid jet head formed by this method.

  In the above-described embodiment, the flexural vibration type ink jet recording head is exemplified, but the present invention is not limited to this. For example, a longitudinal vibration type in which piezoelectric materials and electrode forming materials are alternately stacked to expand and contract in the axial direction. The present invention can be applied to ink jet recording heads having various structures, such as the ink jet recording head.

  In addition, although the piezoelectric element has been described as the pressure generating element provided corresponding to the pressure generating chamber communicating with the nozzle opening for ejecting ink droplets, the pressure generating element is not limited to the piezoelectric element, and is drawn from other elements such as a heating element. The present invention can also be applied to a connection portion between a bonding wire connected to the lead-out wiring and the lead-out wiring.

  Furthermore, the ink jet recording head I of the above-described embodiment constitutes a part of a recording head unit including an ink flow path communicating with an ink cartridge or the like, and is mounted on the ink jet recording apparatus. FIG. 8 is a schematic view showing an example of the ink jet recording apparatus. As shown in FIG. 8, the recording head units 1A and 1B having the head main body are detachably provided with cartridges 2A and 2B constituting the ink supply means, and the carriage 3 on which the recording head units 1A and 1B are mounted is 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. 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 conveyed on the platen 8. It is like that.

  In the above-described embodiment, the ink jet recording head I has been described as an example of the liquid ejecting head of the present invention. However, the basic configuration of the liquid ejecting head is not limited to that described above. Of course, the present invention can also be applied to a liquid ejecting liquid other than ink. Other liquid ejecting heads include, for example, various recording heads used in image recording apparatuses such as printers, color material ejecting heads used for manufacturing color filters such as liquid crystal displays, organic EL displays, and FED (field emission). Examples thereof include an electrode material ejection head used for electrode formation such as a display, and a bioorganic matter ejection head used for biochip production.

FIG. 2 is an exploded perspective view of a recording head according to an embodiment. FIG. 3 is a plan view of the recording head according to the embodiment. FIG. 3 is a cross-sectional view of the recording head according to the embodiment. FIG. 6 is a cross-sectional view illustrating a manufacturing process of the liquid jet head according to the embodiment. FIG. 6 is a cross-sectional view illustrating a manufacturing process of the liquid jet head according to the embodiment. FIG. 6 is a cross-sectional view illustrating a manufacturing process of the liquid jet head according to the embodiment. FIG. 6 is a cross-sectional view illustrating a manufacturing process of the liquid jet head according to the embodiment. 1 is a schematic diagram of a recording apparatus according to an embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Flow path formation board | substrate, 12 Pressure generation chamber, 13 Communication part, 14 Ink supply path, 20 Nozzle plate, 21 Nozzle opening, 30 Protection board, 31 Piezoelectric element holding | maintenance part, 32 Reservoir part, 33 Through-hole, 40 Compliance board, 50 elastic film, 55 insulator film, 60 lower electrode film, 70 piezoelectric layer, 80 upper electrode film, 90 lead electrode, 110 reservoir, 120 driving IC, 130 bonding wire, 151 IC holding part, 200 head case, 250 potting Agent, 300 piezoelectric element, 400 insulating film

Claims (5)

A pressure generating element provided corresponding to a pressure generating chamber communicating with a nozzle opening for injecting a liquid; a driving IC for driving the pressure generating element; a lead wiring drawn from the pressure generating element; and the driving A liquid ejecting head comprising a bonding wire for electrically connecting an IC,
A liquid ejecting head, wherein an insulating film of an inorganic insulating material is formed at least on a surface of the bonding wire. The liquid ejecting head according to claim 1,
An IC holding portion which is a space surrounding the driving IC and is provided penetrating in the thickness direction and made of a conductive material, and
The liquid ejecting head according to claim 1, wherein the insulating film is formed on an inner peripheral surface of the head case and a surface of the driving IC. The liquid ejecting head according to claim 1 or 2,
The liquid ejecting head according to claim 1, wherein the insulating film is formed by a CVD method. The liquid ejecting head according to any one of claims 1 to 3,
The liquid ejecting head, wherein the IC holding portion is configured by filling a potting agent from an organic insulating material on the insulating film.   A liquid ejecting apparatus comprising the liquid ejecting head according to claim 1.