Patent Publication Number: US-7585060-B2

Title: Liquid ejecting head and liquid ejecting apparatus

Description:
The entire disclosure of Japanese Patent Application No, 2006-162763, filed Jun. 12, 2006 is expressly incorporated by reference herein. 
     BACKGROUND 
     1. Technical Field 
     The present invention generally relates to liquid ejecting heads and liquid ejecting apparatuses, and more particularly, it relates to an ink jet recording head and an ink jet recording apparatus in which a portion of a pressure-generating chamber communicating with a nozzle opening that ejects an ink droplet is constituted by a diaphragm, a piezoelectric element is provided on a surface of the diaphragm, and the ink droplet is ejected by displacement of the piezoelectric element. 
     2. Related Art 
     A typical ink jet recording head has a configuration in which a portion of a pressure-generating chamber communicating with a nozzle opening that ejects an ink droplet is constituted by a diaphragm, the diaphragm is deformed by a piezoelectric element to apply a pressure to ink provided in the pressure-generating chamber, so that the ink is ejected from a nozzle opening as an ink droplet. For example, the ink jet recording head uses a piezoelectric actuator of flexural vibration mode. 
     Such an ink jet recording head includes a passage-forming substrate having an array of pressure-generating chambers communicating with nozzle openings, a joint substrate bonded to a surface of the passage-forming substrate with piezoelectric elements, and a driver IC mounted on a wiring pattern provided at the joint substrate, for driving the piezoelectric elements. The driver IC and the wiring pattern are electrically connected by wire bonding, and also the driver IC and lead wires extending from the piezoelectric elements are electrically connected by wire bonding (for example, see JP-A-2004-034293). 
     With this ink jet recording head of the related art, since wires of the wiring pattern on which the driver IC is mounted are arranged at high density, the wiring pattern is necessary to be highly accurately patterned. This may increase manufacturing cost, and cause the adjacent wires to short-circuit, resulting in occurrence of defective connection. In addition, since the driver IC and the wiring pattern, as well as the driver IC and the piezoelectric elements are connected by wire bonding, a relatively wide area is necessary for extension of bonding wires. This may cause an increase in size of the head. These problems may be involved not only in the ink jet recording heads that eject ink, but also in other liquid ejecting heads that eject liquid other than ink. 
     SUMMARY 
     An advantage of some aspects of the invention is to provide a liquid ejecting head and a liquid ejecting apparatus that allows a driver circuit and a piezoelectric element to be electrically connected easily, thereby reducing manufacturing cost and preventing defective connection from occurring. 
     According to an aspect of the invention, a liquid ejecting head includes a passage-forming substrate, a plurality of pressure-generating elements, and an IC chip. The passage-forming substrate has a nozzle opening, and a pressure-generating chamber communicating with the nozzle opening. The plurality of pressure-generating elements are provided on a surface of the passage-forming substrate with a diaphragm interposed therebetween. The pressure-generating elements have electrodes and cause pressure change in the pressure-generating chamber. The IC chip is mounted on the surface of the passage-forming substrate with the pressure-generating elements. The IC chip includes a semiconductor substrate, a driver circuit, a first pad, an external wiring pattern, a second pad, and a through electrode. The driver circuit is provided at a surface of the semiconductor substrate. The driver circuit drives the pressure-generating elements. The first pad is provided on a surface of the semiconductor substrate opposite to a surface facing the passage-forming substrate. The first pad is electrically connected to the driver circuit. The external wiring pattern is electrically connected to the first pad. The second pad is provided on the surface of the semiconductor substrate facing the passage-forming substrate. The second pad is electrically connected to the electrodes of the pressure-generating elements. The through electrode penetrates through the semiconductor substrate. The through electrode is connected to the second pad. In this liquid ejecting head, the electrodes of the pressure-generating elements include individual electrodes, and at least the individual electrodes are electrically connected to the driver circuit via the through electrode. 
     With this configuration, the pressure-generating elements can be electrically connected to the driver circuit via the through electrode relatively easily and reliably. Also, since the wiring structure for the connection between the pressure-generating elements and the driver circuit is simplified, the manufacturing cost can be reduced, and the defective connection can be prevented. 
     Preferably, in the liquid ejecting head, the IC chip may be arranged such that a plurality of semiconductor substrates are laminated. Each of the semiconductor substrates may have the through electrode penetrating therethrough. Also, the through electrodes of the semiconductor substrates may be connected to one another via an intermediate wiring pattern, the intermediate wiring pattern extending to a joint surface where the adjacent semiconductor substrates are bonded. 
     With this configuration, the position of an end of the through electrode located at the surface of the IC chip near the external wiring pattern may be different from the position of the other end of the through electrode located at the surface thereof near the passage-forming substrate. Accordingly, the through electrode can be connected to the electrodes of the pressure-generating elements at desired position. 
     Preferably, the liquid ejecting head may further includes a joint substrate bonded to the surface of the passage-forming substrate with the pressure-generating element. At least one of surfaces of a passage through which liquid is supplied may be constituted by the joint substrate. 
     With this configuration, the IC chip is mounted on the passage-forming substrate. Accordingly, even when the joint substrate for constituting the passage is bonded on the passage-forming substrate, a conductive adhesive used for mounting the IC chip may not have the ink-resistant characteristic. This may widen the choices of adhesives. 
     Preferably, in the liquid ejecting head, the passage-forming substrate may have a nozzle plate bonded thereon, the nozzle plate having the nozzle opening made by punching. Also, the passage-forming substrate and the nozzle plate may be made of a silicon single crystal substrate. 
     With this configuration, the passage-forming substrate and the nozzle plate are made of the silicon single crystal substrate, thereby having the same coefficient of thermal expansion. Accordingly, even when the IC chip is mounted on the passage-forming substrate at a relatively high temperature, the passage-forming substrate and the like would not be deformed. 
     Preferably, in the liquid ejecting head, the through electrode may be connected to lead electrodes extending from the electrodes of the pressure-generating elements. 
     With this configuration, the IC chip can be mounted on the passage-forming substrate relatively easily, and the driver circuit can be electrically connected to the pressure-generating elements further reliably. 
     Preferably, in the liquid ejecting head, the electrodes of the pressure-generating elements may include common electrodes. The lead electrodes may include common lead electrodes and individual lead electrodes, the common lead electrodes extending from the common electrodes of the pressure-generating elements, the individual lead electrodes extending from the individual electrodes of the pressure-generating elements. Also, the common lead electrodes and the individual lead electrodes may be located at the same height in a region where the common lead electrodes and the individual lead electrodes are connected to the driver circuit. 
     With this configuration, the connection surface between the individual lead electrodes and the driver circuit, and the connection surface between the common lead electrodes and the driver circuit become arranged at the same plane. Accordingly, the driver circuit can be connected to the individual and common lead electrodes without rattling. 
     According to another aspect of the invention, a liquid ejecting apparatus includes the above-described liquid ejecting head. 
     With this configuration, a liquid ejecting apparatus can be provided that is capable of promoting the reduction in size of the head, and enhancing the reliability of the head. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
         FIG. 1  is an exploded perspective view showing a recording head according to a first embodiment. 
         FIG. 2A  is a plan view showing the recording head according to the first embodiment. 
         FIG. 2B  is a cross-sectional view showing the recording head according to the first embodiment. 
         FIG. 3  is an enlarged cross-sectional view showing the recording head according to the first embodiment. 
         FIG. 4  is an enlarged cross-sectional view showing a recording head according to a second embodiment. 
         FIG. 5  is an enlarged cross-sectional view showing a modification of the recording head according to the second embodiment. 
         FIG. 6  is a schematic illustration showing a recording apparatus according to an embodiment. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The invention is described below in detail according to embodiments. 
     First Embodiment 
       FIG. 1  is an exploded perspective view showing an ink jet recording head which is an example of a liquid ejecting head according to a first embodiment of the invention.  FIGS. 2A and 2B  are a plan view and a cross-sectional view of  FIG. 1 . As shown in the drawings, a passage-forming substrate  10  is made of a silicon single crystal substrate arranged along a plane (110) in this embodiment. An elastic film  50  is previously formed on one surface of the passage-forming substrate  10 . The elastic film  50  has a thickness ranging from 0.5 to 2 μm and made of silicon dioxide by thermal oxidization. A plurality of pressure-generating chambers  12  are aligned in a width direction of the passage-forming substrate  10  to form an array  13 . Here, two arrays  13  are provided at the passage-forming substrate  10 . Communicating portions  14  are provided in regions of the passage-forming substrate  10  at outer sides in a longitudinal direction of the arrays  13  of the pressure-generating chambers  12 . The communicating portions  14  communicate with the pressure-generating chambers  12  through ink supply passages  15  that are respectively provided at the pressure-generating chambers  12 . The communicating portions  14  communicate with reserving portions of protection substrates (described below) and serve as a portion of a reservoir that is a common ink chamber for the pressure-generating chambers  12 . The ink supply passages  15  has a width smaller than that of the pressure-generating chambers  12 , and hold the flow resistance of ink (an example of liquid) constant, the ink flowing from the communicating portions  14  to the pressure-generating chambers  12 . 
     An insulating film  51  is provided at an open side of the passage-forming substrate  10 , and a nozzle plate  20  is fixed to the insulating film  51  with an adhesive, a hot welding film, or the like, interposed therebetween. The insulating film  51  has been used as a mask when forming the pressure-generating chambers  12 . The nozzle plate  20  has nozzle openings  21  formed by punching, each nozzle opening  21  communicating with the pressure-generating chamber  12  at an end opposite to the ink supply passage  15 . The material of the nozzle plate  20  may be, for instance, glass ceramic, a silicon single crystal substrate, or stainless steel. In particular, a silicon single crystal substrate is preferably used because it is the material of the passage-forming substrate  10 . 
     On a side opposite to the open side of the passage-forming substrate  10 , the elastic film  50  with a thickness of about 1.0 μm is formed as described above, and an insulating film  55  with a thickness of about 0.4 μm is formed on the elastic film  50 . Also, piezoelectric elements  300  are provided on the insulating film  55 . Each piezoelectric element  300  includes a bottom electrode film  60  with a thickness of about 0.2 μm, a piezoelectric material layer  70  with a thickness of about 1.0 μm, and a top electrode film  80  with a thickness of about 0.05 μm. Note that the piezoelectric element  300  (an example of the pressure-generating element) is a portion including the bottom electrode film  60 , the piezoelectric material layer  70 , and the top electrode film  80 . In general, one of the electrodes of the piezoelectric element  300  serves as a common electrode, and the residual electrode and the piezoelectric material layer  70  are patterned corresponding to each pressure-generating chamber  12 . In this embodiment, the bottom electrode film  60  serves as a common electrode of the piezoelectric element  300 , and the top electrode film  80  serves as an individual electrode of the piezoelectric element  300 . Alternatively, these arrangement may be reversed depending on the arrangement of a driving circuit and wiring. In this embodiment, the elastic film  50 , the insulating film  55  and the bottom electrode film  60  define a diaphragm. Alternatively, the elastic film  50  and the insulating film  55  may not be provided and only the bottom electrode film  60  may serve as a diaphragm. 
     Lead electrodes are connected to the electrodes of the piezoelectric elements  300 . In particular, individual lead electrodes  90 , for example, made of gold (Au), are connected to the top electrode films  80  serving as the individual electrodes of the piezoelectric elements  300 . The individual lead electrodes  90  extend to a region between the arrays  13  of the pressure-generating chambers  12 . A plurality of common lead electrodes  91  extend from the bottom electrode films  60  serving as the common electrodes of the piezoelectric elements  300 . For instance, one common lead electrode  91  may be provided every tenth piezoelectric element  300 . 
     Though described below in details, a driver circuit (semiconductor integrated circuit) for driving the piezoelectric elements  300  is electrically connected to tip ends of the individual lead electrodes  90  extending from the piezoelectric elements  300  and on the tip ends of the common lead electrodes  91  extending from the bottom electrode films  60 . 
     A protection substrate  30  is bonded on the passage-forming substrate  10 . The protection substrate  30  has a piezoelectric element retainer  31  that is a space for protecting the piezoelectric elements  300 . In this embodiment, a plurality of protection substrates  30  are bonded on the passage-forming substrate  10 . In particular, one protection substrate  30  may be provided for each array  13  of the piezoelectric elements  300 . Each protection substrate  30  has a reserving portion  32  provided at a region corresponding to the communicating portion  14  of the passage-forming substrate  10 . In this embodiment, the reserving portion  32  penetrates through the protection substrate  30  in the thickness direction and is disposed along the array  13  of the pressure-generating chambers  12 . As mentioned above, the reserving portion  32  communicates with the communicating portion  14  of the passage-forming substrate  10  to define a reservoir  100  that is a common ink chamber for the pressure-generating chambers  12 . In other words, the protection substrate  30  defines a portion of an ink passage through which ink is supplied. 
     The material of such a protection substrate  30  may be glass, a ceramic material, metal, resin, or the like. The protection substrate  30  is preferably made of a material having substantially the same coefficient of thermal expansion as that of the passage-forming substrate  10 . In this embodiment, the protection substrate  30  is made of the same material as that of the passage-forming substrate  10 , i.e., a silicon single crystal substrate. 
     A compliant substrate  40  is bonded on the protection substrate  30 . The compliant substrate  40  includes a sealing film  41  and a fixing plate  42 . The sealing film  41  is made of a flexible material having a low rigidity (for example, a polyphenylene sulfide (PPS) film with a thickness of 6 μm). One surface of the reserving portion  32  is sealed with the sealing film  41 . The fixing plate  42  is made of a rigid material like metal, for example, stainless steel (SUS) with a thickness of 30 μm. A region of the fixing plate  42  facing the reservoir  100  is completely removed in the thickness direction to form an opening  43 . One surface of the reservoir  100  is sealed only with the flexible sealing film  41 . 
     An IC chip  200  having a driver circuit  201  for driving the piezoelectric elements  300  is mounted on the passage-forming substrate  10  in a region between the protection substrates  30 . The above-described individual lead electrodes  90  and common lead electrodes  91  extend to the region between the protection substrates  30 . For example, an anisotropic conductive agent, such as an anisotropic conductive film (ACF), anisotropic conductive paste (ACP), a non-conductive film (NCF), or non-conductive paste (NCP) is applied on the individual lead electrodes  90  and the common lead electrodes  91 , and the IC chip  200  is mounted thereon. Though described below, through electrodes  202  are provided in the IC chip  200 . The driver circuit  201  is connected to the individual lead electrodes  90  and the common lead electrodes  91  via the through electrodes  202 . In particular, the top electrode films  80  serving as the individual electrodes of the piezoelectric elements  300  are electrically connected to the driver circuit  201  via the individual lead electrodes  90  and the through electrodes  202 . The bottom electrode films  60  serving as the common electrodes of the piezoelectric elements  300  are electrically connected to the driver circuit  201  via the common lead electrodes  91  and the through electrodes  202 . 
     As shown in an enlarged cross-sectional view in  FIG. 3 , a semiconductor substrate  203  of the IC chip  200  is, for instance, made of a silicon substrate. The driver circuit  201  for driving the piezoelectric elements  300  is disposed on one surface of the semiconductor substrate  203 , i.e., on the surface located opposite to a joint surface with respect to the passage-forming substrate  10 . An external wiring pattern  204  made of a flexible tape, for example, a chip-on-film (COF) is fixed to one surface of the IC chip  200 . First pads  205  connected to the driver circuit  201  are provided on the one surface of the IC chip  200 . Wiring lines  206  of the external wiring pattern  204  are connected to the first pads  205 . 
     The top electrode films  80  serving as the individual electrodes of the piezoelectric elements  300  are electrically connected to the driver circuit  201  via the through electrodes  202  provided in the IC chip  200  as described above. The through electrodes  202  penetrate through the IC chip  200  in the thickness direction, and are provided corresponding to the individual lead electrodes  90  and the common lead electrodes  91 . Ends of the through electrodes  202  are connected to a connection wiring pattern  207  provided on the surface of the IC chip  200  (i.e., a surface to which the external wiring pattern  204  is fixed) and are electrically connected to the driver circuit  201  via the connection wiring pattern  207 . The other ends of the through electrodes  202  are connected to second pads  208  provided on the surface of the IC chip  200  at the individual lead electrode  90  side. Tip ends of the individual lead electrodes  90  extending from the top electrode films  80  of the piezoelectric elements  300  are connected to the second pads  208 . Although not shown, the through electrodes  202  are also provided at regions corresponding to the common lead electrodes  91  extending from the bottom electrode films  60  serving as the common electrodes of the piezoelectric elements  300 . The common lead electrodes  91  are connected to predetermined wiring lines  206  of the external wiring pattern  204  via the through electrodes  202 . For instance, one common lead electrodes  91  may be provided every second nozzle or tenth nozzle within a range not causing cross talk. 
     In this embodiment, as described above, the through electrodes  202  are provided in the semiconductor substrate  203  of the IC chip  200 . Also, the second pads  208  to which the individual lead electrodes  90  and the common lead electrodes  91  are connected are provided on the surface thereof located opposite to the surface to which the external wiring pattern  204  is fixed. That is, the top electrode films  80  and the bottom electrode films  60  of the piezoelectric elements  300  are electrically connected to the driver circuit  201  via the through electrodes  202 . 
     Accordingly, the wiring structure for electrically connecting the driver circuit  201  and the electrodes of the piezoelectric elements  300  (the bottom electrode films  60  and the top electrode films  80 ) can be simplified. Therefore, it is not necessary to provide wiring lines for mounting the IC chip  200  on the passage-forming substrate  10 . Generally, high current is supplied to the bottom electrode films  60  when all nozzles are driven. Since at least one wiring line is connected to the bottom electrode films  60  from the external wiring pattern  204  having a relatively small resistance, the bottom electrode films  60  may become thin and accurate, and the bottom electrode films  60  do not disturb displacement of the head, thereby improving displacement characteristic. This may promote reduction in size of the head and its manufacturing cost. 
     The individual lead electrodes  90  extending from the top electrode films  80  and the common lead electrodes  91  extending from the bottom electrode films  60  may be preferably arranged at the same height in a region where these electrodes  90  and  91  are connected to the driver circuit  201 , i.e., in a region where these electrodes  90  and  91  are connected to the second pads  208 . When the height (thickness) of the common lead electrodes  91  extending from the bottom electrode films  60  are lower (smaller) than that of the individual lead electrodes  90  extending from the top electrode films  80 , pads for adjusting the height are provided at the region where the common lead electrodes  91  are connected to the driver circuit. With this configuration, the driver circuit can be connected to the individual lead electrodes  90  and the common lead electrodes  91  without rattling. 
     In this embodiment, the nozzle plate  20  is made of a silicon single crystal substrate which is the same material as that of the passage-forming substrate  10 . Accordingly, the mounting temperature of the IC chip  200  can be relatively high such as about 150° C. In particular, the coefficient of linear expansion of the passage-forming substrate  10  is the same as that of the nozzle plate  20 . Even when the mounting temperature of the IC chip  200  is relatively high, the IC chip  200  can be mounted reliably without deformation occurring in the passage-forming substrate  10  and the like. 
     In this embodiment, the IC chip  200  is mounted on the passage-forming substrate  10 , and the protection substrate  30 , which is a joint substrate having the reserving portion  32  to form the ink passage, is bonded. When the protection substrate  30  is bonded to the passage-forming substrate  10 , an adhesive having ink-resistant characteristic (liquid-resistant characteristic) is necessary to be used. For example, if the IC chip is mounted on the protection substrate, an adhesive for connecting and fixing the IC chip also needs to have the ink-resistant characteristic. That is, a method of connecting the IC chip is limited. However, since the IC chip  200  is mounted on the passage-forming substrate  10  as described in this embodiment, the adhesive (anisotropic conductive agent) may not have the ink-resistant characteristic. This may widen the choices of adhesives. In other words, this may widen the choices of methods of connecting the IC chip. 
     With the ink jet recording head of the above-described embodiment, an external ink supplying unit (not shown) supplies ink, the passage from the reservoir  100  to the nozzle openings  21  is filled with the ink, then a voltage is applied between the bottom electrode films  60  and the top electrode films  80  corresponding to the pressure-generating chambers  12  in accordance with a recording signal sent from the driver circuit  201 , and consequently the elastic film  50 , the insulating film  55 , the bottom electrode film  60  and the piezoelectric material layer  70  are bent. Accordingly, the pressure in the pressure-generating chambers  12  increases and ink droplets are ejected from the nozzle openings  21 . 
     Second Embodiment 
       FIG. 4  is an enlarged cross-sectional view showing the overview of the ink jet recording head according to a second embodiment. This embodiment is a modification of the IC chip  200 , and other components are similar to those of the first embodiment. In particular, as shown in  FIG. 4 , an IC chip  200 A of this embodiment includes two laminated semiconductor substrates (a first semiconductor substrate  203 A and a second semiconductor substrate  203 B). The first and second semiconductor substrates  203 A and  203 B respectively have first and second through electrodes  202 A and  202 B. The first through electrodes  202 A provided in the first semiconductor substrate  203 A are connected to the second through electrodes  202 B provided in the second semiconductor substrate  203 B, via an intermediate wiring pattern  209  provided between the first and second semiconductor substrates  203 A and  203 B. 
     With this configuration, a connection portion where the through electrodes (first through electrodes) are connected to the connection wiring pattern  207 , and a connection portion where the second pads  208  of the through electrodes (second through electrodes) are connected to the second pads  208 , can be arranged at different positions in a plane direction of the IC chip  200 A. In other words, the connection portions of the through electrodes can be relatively easily located at desired positions without extension of wiring lines to the surface of the IC chip  200 A. This configuration may provide advantages similar to those of the first embodiment. 
     In this embodiment, while the driver circuit  201  is provided at the surface of the second semiconductor substrate  203 B, i.e., at the surface opposite to a surface facing the first semiconductor substrate  203 A, it is not limited thereto. For example, as shown in  FIG. 5 , the driver circuit  201  may be provided at the surface of the second semiconductor substrate  203 B facing the first semiconductor substrate  203 A. In such a case, the second pads  208 , to which the individual lead electrodes  90  extending from the top electrode films  80  and the common lead electrodes  91  extending from the bottom electrode films  60  of the piezoelectric elements  300  are connected, may be connected to the driver circuit  201  via the first through electrodes  202 A provided in the first semiconductor substrate  203 A and via the intermediate wiring pattern  209 . Also, the first pads  205 , to which the external wiring pattern  204  is connected, may be connected to the driver circuit  201  via the second through electrodes  202 B provided in the second semiconductor substrate  203 B and via the intermediate wiring pattern  209 . 
     While the IC chip has a laminated structure having the two semiconductor substrates in this embodiment, the IC chip may have a laminated structure having three or more semiconductor substrates. 
     Other Embodiment 
     The embodiments of the invention are described above, however, the basic structure of the ink jet recording head is not limited thereto. The ink jet recording head described in the embodiments is mounted in an ink jet recording apparatus as a portion of a recording head unit having an ink passage communicating with an ink cartridge and the like.  FIG. 6  is a schematic illustration showing such an ink jet recording apparatus. As shown in  FIG. 6 , recording head units  1 A and  1 B have ink jet recording heads. Cartridges  2 A and  2 B (ink supplying units) are detachably attached to the recording head units  1 A and  1 B. The recording head units  1 A and  1 B are mounted in a cartridge  3 . The cartridge  3  is provided at a carriage shaft  5  attached to an apparatus body  4 , and is movable along the cartridge shaft  5 . The recording head units  1 A and  1 B, for example, eject a black ink composition and a color ink composition. The driving force of a driving motor  6  is transmitted to the carriage  3  through a plurality of gears (not shown) and a timing belt  7 . With this driving force, the carriage  3  having the recording head units  1 A and  1 B mounted thereon moves along the carriage shaft  5 . Also, a platen  8  is provided at the apparatus body  4  along the carriage shaft  5 . A recording sheet S, which is a recording medium such as paper, fed by a sheet-feeding roller (not shown) is transported over the platen  8 . 
     While the above embodiment is described based on the ink jet recording head as a liquid ejecting head, the invention may be applied to a variety of liquid ejecting heads. The invention may be applied to a configuration for ejecting liquid other than ink. Examples of the liquid ejecting heads may include various recording heads used for image recording apparatuses such as printers; color material ejecting heads used for manufacturing color filters of liquid crystal displays etc.; electrode materials ejecting heads used for forming electrodes of organic electroluminescence (EL) displays, field emission displays (FEDs), etc.; and living organic material ejecting heads used for manufacturing biochips.