Patent Publication Number: US-8118411-B2

Title: Inkjet head manufacturing method and inkjet head

Description:
This application is based on Japanese Patent Application No. 2006-280646 filed on Oct. 13, 2006, in Japanese Patent Office, the entire content of which is hereby incorporated by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to an inkjet head manufacturing method and an inkjet head, particularly to a method of manufacturing an inkjet head wherein a flow path regulating member for regulating the flow path of ink into the channel is arranged on the rear side of the head chip, and the inkjet head manufactured thereby. 
     BACKGROUND OF THE INVENTION 
     The conventional art has provided a share mode type inkjet head wherein voltage is applied to the electrode formed on a drive wall for separating the channel so that the drive wall is subjected to shear deformation, and the ink inside the channel is discharged out of the nozzle using the pressure generated inside the channel at this time. As this share mode type inkjet head, an inkjet head provided with the so-called harmonica type head chip is known, wherein the drive walls made up of piezoelectric elements and the channels are arranged alternately, and a channel aperture is arranged on each of the front side and rear side (Patent Document 1, 2). 
     In the case of an inkjet head having such a harmonica type head chip, ink is supplied into each channel from the rear side of the head chip. Accordingly, an ink manifold is connected to the rear side of the head chip, and the ink stored in this ink manifold is supplied to each channel. 
     Incidentally, as disclosed in the Patent Documents 1 and 2, the rear side of such a head chip is provided with a flow path regulating member for regulating the flow of ink into the channel by reducing the area of the aperture on the rear side of the channel. 
       FIG. 16  is a rear side view of the head chip  600  connected with a flow path regulating member  500 . This drawing illustrates a harmonica type head chip  600  wherein the air channels  601  that do not emit ink and the ink channels  602  that emit ink are arranged alternately. 
     The flow path regulating member  500  utilizes a plastic film such as a sheet of polyimide having the size capable of covering almost all the surfaces on the rear side of the head chip  600 . This film is bonded using adhesives as an epoxy adhesive and others. Here the rear side of each air channel  601  provided on the head chip  600  is completely blocked and an ink inlet  501  is formed so as to conform to each ink channel  602 , thereby reducing the area of the aperture on the rear side (on the side supplied with ink) of each ink channel  602 . The ink inlet  501  is provided, for example, by laser processing in such a way as to have a diameter smaller than that of the aperture on the rear side of the ink channel  602 . 
     As described above, the area of the aperture on the rear side of the ink channel is reduced by the flow path regulating member  500 , whereby easy control of the ink meniscus in the nozzle is ensured and high-speed drive is enabled. Thus, this arrangement provides the advantage of enhancing the drive characteristics. 
     When all the channels arranged on the head chip are ink channels, the ink inlets of the flow path regulating member are arranged so as to correspond to all the channels.
     [Patent Document 1] Unexamined Japanese Patent Application Publication No. 2004-90374   [Patent Document 2] Unexamined Japanese Patent Application Publication No. 2006-35454   

     When the aforementioned flow path regulating member is connected to the rear side of the head chip, the coated adhesive may ooze from the ink inlet. This requires a large quantity of adhesive to be coated. This involves such problems as the excess adhesive flowing into the channel to block the channel and to cause emission failure, or ink flowing into the air channel due to insufficient coating of the adhesive, with the result that ink inlet is blocked by adhesive. 
     The connection electrode and others having been pulled out to the rear side of the head chip and having been formed therein will be covered by adhesive and electrical connection cannot be made. When this problem has occurred, it is necessary to remove the unwanted adhesive by dry etching or other means. This requires extra time and effort. 
     When the flow path regulating member is bonded by the adhesive oozing from the ink outlet, contact pressure cannot be easily applied from the flow path regulating member. The utmost caution must be taken when coating the adhesive and bonding the member. This gives rise to manufacturing difficulties. 
     Moreover, processing costs cannot be ignored when the ink inlet is processed by laser. 
     Further, when the area of the aperture on the rear side of the channel is to be reduced by the flow path regulating member, the ink inlet having a smaller area than that of the aperture on the rear side of the channel is formed approximately at the center of the aperture in the conventional flow path regulating member. Thus, the bubble having occurred inside the channel at the time of driving cannot easily get out of the ink inlet, and remains inside the channel. The bubble remaining inside the channel prevents a sufficient amount of the emission pressure from being applied to the ink, with the result that emission failure occurs. 
     SUMMARY OF THE INVENTION 
     Thus, the object of the present invention is to provide an inkjet head manufacturing method capable of ensuring that a flow path regulating member is pressed and firmly bonded on the rear side of the harmonica type head chip, wherein there is no concern for possible clogging of the channel due to adhesive or possible oozing of adhesive. 
     Another object of the present invention is to provide an inkjet head containing a flow path regulating member firmly bonded on the rear side of the harmonica type head chip, wherein there is no concern for possible clogging of the channel due to adhesive or possible oozing of adhesive. 
     A further object of the present invention is to provide an inkjet head manufacturing method capable of ensuring that a flow path regulating member is pressed and firmly bonded, without any concern for possible clogging of the channel due to adhesive or possible oozing of adhesive, and that, even when the area of the aperture on the rear side of the channel has been reduced, the bubble remaining in the channel is efficiently removed, without bubbles being formed easily. 
     A still further object of the present invention is to provide an inkjet head containing a flow path regulating member bonded firmly on the rear side of the harmonica type head chip, without any concern for possible clogging of the channel due to adhesive or possible oozing of adhesive; the inkjet head further characterized in that, even when the area of the aperture on the rear side of the channel has been reduced, the bubble remaining in the channel is efficiently removed, without bubbles being formed easily. 
     Other objects of the present invention will become apparent from the following description: 
     The aforementioned objects can be achieved by the following: 
     1. A manufacturing method of an inkjet head having a head chip wherein channels and drive walls configured with piezoelectric elements are arranged alternately, and apertures are arranged respectively at front and rear surfaces of the channel in which a drive electrode is formed and a flow path regulating member arranged at the rear surface of the head chip to regulate ink flow into the channel, wherein shear deformation is caused at the drive wall by applying a voltage so that ink in the channel is emitted, the manufacturing method including steps of: providing a multilayer film to be adhered onto the rear surface of the head chip, wherein a mask layer is patterned on an organic layer so that the mask layer not etched by dry etching corresponds to the channels where ink flow is to be regulated; and removing a portion of the organic film which is not covered by the mask layer by dry etching so as to form the flow path regulation member.
 
2. An inkjet head, wherein shear deformation is caused at a drive wall by applying a voltage so as to emit ink in a channel, including: a head chip wherein the channels and the drive walls configured with piezoelectric elements are arranged alternately, apertures are arranged respectively at a front surface and rear surface of the head chip, and a drive electrode is formed in each channel; and a flow path regulating member arranged at the rear surface of the head chip to regulate ink flow into the channel, wherein the flow path regulating member is formed by a multilayer which is made in a way where a mask layer which cannot be etched by dry etching is formed on a surface of an organic film and the multilayer is etched by dry etching.
 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing the head chip portion of the inkjet head as a first embodiment as viewed from the rear side; 
         FIG. 2(   a ) is a cross sectional view of the ink channel portion of the inkjet head of  FIG. 1 , with  FIG. 2(   b ) being a cross sectional view of an air channel; 
         FIGS. 3(   a ) through ( e ) are explanatory diagrams representing the head chip manufacturing process; 
         FIG. 4  is an explanatory diagram representing the head chip manufacturing process; 
         FIG. 5  is a diagram representing the flow path regulating member manufacturing process, wherein ( a ) is a cross sectional view showing that a photo mask is applied on a laminated film coated with resists, and ( b ) is a plane view showing the same as seen from the photo mask side; 
         FIG. 6  is a diagram representing the flow path regulating member manufacturing process, wherein ( a ) is a cross sectional view of the laminated film with resists remaining thereon, and ( b ) is a plane view showing the same as seen from the resist side; 
         FIG. 7  is a diagram representing the flow path regulating member manufacturing process, wherein ( a ) is a cross sectional view of the laminated film wherein the mask layer is patterned, and ( b ) is a plane view of the same as seen from the mask layer side; 
         FIG. 8  is a diagram representing the flow path regulating member manufacturing process, wherein ( a ) is a cross sectional view showing that the laminated film of  FIG. 7  is bonded on the rear side of the head chip, and ( b ) is a rear side view of the head chip; 
         FIG. 9  is a diagram representing the flow path regulating member manufacturing process, wherein ( a ) is a cross sectional view showing that an organic film is dry-etched, and ( b ) is a rear side view of the head chip; 
         FIG. 10  is a diagram showing the head chip manufacturing process; 
         FIG. 11  is a cross sectional view representing an example of the inkjet head; 
         FIG. 12  is a perspective view showing the head chip portion of the inkjet head as a second embodiment as viewed from the rear side; 
         FIG. 13(   a ) is a cross sectional view of the ink channel of the inkjet head of  FIG. 12 , with  FIG. 13(   b ) being a cross sectional view of an air channel; 
         FIG. 14  is a cross sectional view showing the head chip portion when the inkjet head is arranged in a slanting direction; 
         FIG. 15  is a rear side view of the head chip portion of the inkjet head as a third embodiment; and 
         FIG. 16  is a rear side view of the head chip provided with a conventional flow path regulating member. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following describes the embodiments of the present invention with reference to drawings: 
       FIG. 1  is a perspective view showing the head chip portion of the inkjet head as a first embodiment as viewed from the rear side. 
     In the drawing, the reference numeral  1 A denotes a head chip and  2  indicates a nozzle plate connected with the front side of the head chip  1 A. 
     In this Specification, the surface on the side wherein ink is emitted from the head chip is referred to as the “front side” and the surface opposite thereto is called the “rear side”. The outer surfaces on the upper and lower portions in the drawing, sandwiching the channel juxtaposed in the head chip, are called the “upper side” and “lower side”, respectively. 
     The drive walls  11  made up of piezoelectric elements, and channels  12  and  13  are arranged alternately on the head chip  1 A. In this drawing, five channels  12  and  13  are illustrated by way of an example, without the number of the channels  12  and  13  being restricted thereto. 
     The head chip  1 A is an independent channel type head chip wherein channels that emit ink (referred to as “ink channels” in some cases)  12  and the channels that do not emit ink (referred to as “air channels” in some cases)  13  are arranged alternately. Each of the channels  12  and  13  is configured in such a way that the walls on both sides rise almost vertical with respect to the upper side and lower side of the head chip  1 A, and are parallel to each other. 
       FIG. 2(   a ) is a cross sectional view of the inkjet head  12  of  FIG. 1 , and  FIG. 2(   b ) is a cross sectional view of an air channel  13 . 
     The apertures  121  and  131  on the front side of each of the channels  12  and  13 , and the apertures  122  and  132  on the rear side are arranged face to face with each other on the front side and rear side of the head chip  1 A. Each of the channels  12  and  13  is designed in a straight form with a very small change in size and shape along the length from the apertures  122  and  132  on the rear side to the apertures  121  and  131  on the front side. 
     A drive electrode  14  made up of a metallic film such as Ni, Co, Cu and Al is formed in a closely linked configuration on the inner surface of each of the channels  12  and  13 . 
     On the rear side of the head chip  1 A, the connection electrodes  15  electrically connected with the drive electrode  14  in each of the ink channels  12  are formed by being separately pulled out downward in the drawing. One common electrode  16  electrically connected with all of the drive electrodes  14  inside each of the air channels  13  is formed by being pulled out upward in the drawing, in the direction opposite to the connection electrode  15 . 
     The following describes an example of manufacturing such as head chip  1 A with reference to  FIGS. 3 and 4  without the present invention being restricted thereto. 
     The piezoelectric element substrate  101  made of polarized PZTs is connected to one substrate  100  using an epoxy based adhesive, and a photosensitive resin film  102  is bonded on the surface of the piezoelectric element substrate  101  ( FIG. 3(   a )). 
     Then from the side of the photosensitive resin film  102 , a plurality of parallel grooves  103  are ground using a dicing blade and others. Each of the grooves  103  is ground from one end of the piezoelectric element substrate  101  to the other end at such a predetermined depth as to almost reach the substrate  100 . This arrangement provides a straight form with a very small change in size and shape along the length ( FIG. 3(   b )). 
     After that, from the side wherein the grooves  103  have been ground, electrode forming metals such as Ni, Co, Cu, Al and others are applied by sputtering method, vapor deposition method or other means, so that a metallic film  104  is formed on the upper side of the resin film  102  having been left ungrounded, and on the inner surface of each groove  103  ( FIG. 3(   c )). 
     This is followed by the step of removing the photosensitive resin film  102 , together with the metallic film  104  formed on the surface thereof. This will yield a substrate  105  wherein the metallic film  104  is formed only on the inner surface of each groove  103 . Two substrates  105  having been formed in the similar manner are prepared, and a positioning step is taken to ensure that the grooves  103  of each substrate  105  will match with each other. Then an epoxy based adhesive or the like is used to bond them together ( FIG. 3(   d )). 
     The head substrate  106  having been produced is cut in the direction perpendicular to the length of the groove  103 , whereby a plurality of harmonica type head chips  1 A are produced. The grooves  103  are formed into the channels  12  and  13 , and the metallic film  104  in each groove  103  is formed into a drive electrode  14 . The drive wall  11  is created between the adjacent grooves  103 . The width between the cut lines C, C . . . determines the drive length (L) of the ink channel  12  of the head chips  1 A,  1 A . . . produced separately, and is determined adequately in response to this drive length ( FIG. 3(   e )). 
     The rear side of the head chip  1 A having been obtained is provided with a photosensitive resin film  200  wherein an opening  201  for forming a connection electrode  15 , and an opening  202  for forming a common electrode  16  are formed by exposure and development. From the side of the photosensitive resin film  200 , such electrode metals are applied, similarly to the case of the metallic film  104 , so that the connection electrode  15  and common electrode  16  are formed inside each of the openings  201  and  202  on an selective basis ( FIG. 4 ). 
     The openings  201  and  202  are preferably provided over all the surfaces of the channels  12  and  13  when consideration is given to the working efficiency in the development and rinsing processes of the photosensitive resin film  200 . This preferred arrangement ensures easy removal of the developing solution and rinsing water from the channels  12  and  13 . 
     A nozzle plate  2  is connected to the front side of the head chip  1 A in the aforementioned manner as shown in  FIG. 1  and  FIG. 2 . The nozzle plate  2  is provided with a nozzle  21  only at the position conforming to the ink channel  12 . Thus, the aperture  131  on the front side of the air channel  13  which does not emit ink is blocked by the nozzle plate  2 . 
     Such a harmonica type head chip  1 A is provided with the flow path regulating members  3  for regulating the flow path independently for each air channel  13  to ensure that ink is not supplied to the aperture  132  on the rear side of each air channel  13  since ink is supplied from the rear side. Thus, this aperture  132  is completely blocked. 
     As shown in  FIG. 2(   b ), the flow path regulating member  3  is formed of a laminate which is made up of an organic film layer  3   a  in contact with the rear side of the head chip  1 A and a mask layer  3   b  formed on the surface of this organic film layer  3   a.    
     A film made of resin that can be patterned by general dry etching can be used as an organic film layer  3   a . Examples include films made of various types of resins such as polyimide, liquid crystal polymer, aramid and polyethylene terephthalate. Of these examples, a polyimide film characterized by excellent etching property is preferably utilized. Further, to facilitate dry etching, the thinnest possible film is preferably used. Use of an aramid film is preferred because it exhibits high strength despite its property of thickness. 
     The thickness of the organic film layer  3   a  is preferably in the range of 10 through 100 μm to ensure strength and ease of dry etching. 
     Further, a metallic film is preferably used because the mask layer  3   b  serves as a masking material in a later dry etching process, and has an excellent resistance during dry etching. The metal that can be used is exemplified by Al, Cu, Ni, W, Ti and Au. Of these, the Al is preferably used because it is less costly, and is characterized by easy patterning. 
     The mask layer  3   b  is only required to be resistant to dry etching. It is possible to use an inorganic thin film other than the metallic film resistant to dry etching such as silicon oxide film, aluminum oxide film and silicon nitride film. Further, this layer is only required to work as a mask layer  3   b  at the time of termination of dry etching of the organic film  3   a , despite slight etching at the time of dry etching. Thus, it is possible to use an organic thin film that can be patterned, as exemplified by a photosensitive resist film and a photosensitive polyimide film. Such an organic thin film per se can be patterned, and this feature provides an advantage of simplifying the work process, as compared to the metallic film being patterned. 
     The thickness of this mask layer  3   b  is preferably in the range of 0.1 through 50 μm from the viewpoint of resistance to dry etching and ease of patterning. 
     The following describes an example of the method of forming this flow path regulating member  3  with reference to  FIG. 5  through  FIG. 9 : 
     As shown in  FIG. 5(   a ), a lamination film  300  is prepared, wherein a metallic film  302  is formed on the entire surface of the organic film  301  having almost the same area as that of the rear side of the head chip  1 A using such a normal thin film patterning technique as sputtering technique. Then the entire surface of this metallic film  302  is coated with a resist  400 . 
     This organic film  301  becomes an organic film layer  3   a  constituting the flow path regulating member  3  later, and the metallic film  302  becomes a mask layer  3   b  constituting the flow path regulating member  3  later. The following describes an example wherein a polyimide film having a thickness of 25 μm is used as an organic film  301 , and aluminum having a thickness of 5 μm as a metallic film  302  is sputtered on the surface. 
     The normal step of photolithography is used for patterning of the resist  400 . The reference numeral  401  in  FIG. 5  denotes a photo mask. This photo mask  401  has a rectangular opening  401   a  having an aperture area slightly greater than that of the aperture  132  on the rear side of each air channel  13  so as to correspond to each air channel  13  of the head chip  1 A. Therefore, light can pass through only this opening  401   a . When this photo mask  401  is used in the step of exposure, only the resist  400  of the portion to which light is applied is exposed. 
     If steps of exposure and development are taken after such a photo mask  401  has been coated on the surface of the resist  400 , the resist  402  of independent rectangular pattern remains on the surface of the lamination film  300 , as shown in  FIGS. 6(   a ) and ( b ). 
     The metallic film  302  not coated with the resist  402  is wet-etched on this lamination film  300 . A proper etching solution is selected in conformity to the metal used in the metallic film  302 . In this case, phosphoric acid is used to etch the metallic film  302  made of aluminum. After wet etching, unwanted resist  402  is removed. This procedure yields a lamination film  300  wherein the mask layer  3   b  is formed by the metallic film  302  remaining on the surface of the organic film  301 , as shown in  FIGS. 7(   a ) and ( b ). 
     As shown in  FIGS. 8(   a ) and ( b ), positioning steps are taken to ensure that the organic film  301  is brought in contact with the head chip  1 A and the position of each mask layer  3   b  conforms to the position of each air channel  13  of the head chip  1 A. Then the lamination film  300  having been obtained is bonded on the rear side of the head chip  1 A using an epoxy based adhesive. 
     This is followed by the step of removing the exposed organic film  301  by dry etching wherein this mask layer  3   b  is used as a mask. 
     A specific dry etching method can be selected as appropriate in conformity to the resin used in the organic film  301 . When polyimide is used as the organic film  301 , for example, in this embodiment, oxygen plasma can be used for dry etching. A parallel tabular RF plasma apparatus is used. After vacuum exhaustion, 50 sccm of oxygen gas is supplied and the valve is adjusted so that pressure is 10 Pa. High frequency with a frequency of 13.56 MHz and power of 500 watts is applied, and the organic film  301  made of polyimide is decomposed and removed in about ten minutes by the oxygen plasma having been generated. 
     During this dry etching, the mask layer  3   b  is not decomposed, and the organic film  301  below the mask layer  3   b  remains without being dry-etched. It becomes an organic film layer  3   a , as shown in  FIGS. 9(   a ) and ( b ). Thus, a rectangular flow path regulating member  3  made of the lamination between this organic film layer  3   a  and mask layer  3   b  is obtained independently for each air channel  13 . 
     The drive electrode  14  is not illustrated in  FIG. 8  and  FIG. 9   
     After that, the mask layer  3   b  of the flow path regulating member  3  can be removed further by etching, but this is not necessary. 
     In the aforementioned method, the lamination film  300  wherein the mask layer  3   b  is patterned on the surface of organic film  301  is bonded on the rear side of the head chip  1 A. It is also possible to make such arrangements that a layer serving as a mask layer  3   b  such as a metallic film  302  is formed on the entire surface of the organic film  301 , and this is bonded on the rear side of the head chip  1 A. After that, the mask layer  3   b  can be formed by patterning through etching. When this method is employed, the presence of a layer serving as the mask layer  3   b  eliminates the possibility of the organic film  301  being elongated by heat and pressure at the time of bonding the lamination film  300 , with the result that the mask layer  3   b  is not misaligned with the air channel  13 . Moreover, the pattern of the mask layer  3   b  is transferred using a photo mask. The photo mask is positioned with reference to the head chip  1 A by means of an exposure apparatus. This positioning can be achieved to an accuracy of several microns. This high accuracy cannot possibly be achieved by other conventional methods. 
     In this case, if the metallic film is used as a mask layer  3   b , the drive electrode  14  of the head chip  1 A may be damaged at the time of wet etching. To prevent this, the metallic film should be made of the metal different from that used in the drive electrode  14  of the head chip  1 A, to ensure that the drive electrode  14  will not be damaged at the time of wet etching. 
     After only the organic film  301  has been bonded on the rear side of the head chip  1   b , the mask layer  3   b  can be formed by patterning the metallic film and others on the surface thereof by sputtering on an selective basis. 
     As described above, in the present invention, the lamination film  300  is provided on the rear side of the head chip  1 A, wherein this lamination film  300  is formed by the step wherein the mask layer  3   b  which has not been etched at the time of etching of the organic film  301  is patterned on the surface of the organic film  301 . After this lamination film  300  has been formed, etching is provided from the side of the mask layer  3   b , and the organic film  301  at other than the site coated with the mask layer  3   b  is removed, whereby the flow path regulating member  3  is formed. The lamination film  300  is bonded on the rear side of the head chip  1 A when the lamination film  300  has no opening of the ink inlet and others before patterning by etching. Thus, there is no possibility of the adhesive oozing out of the opening that might result in insufficient adhesive, even if adhesive has been coated. This means that there is no need of coating a large amount of adhesive. Further, to avoid the problem of the adhesive oozing out of the opening, the present invention allows contact pressure to be performed at the time of bonding, whereby reliable bonding is ensured. 
     Even if the adhesive has oozed out at the time of bonding the lamination film  300 , unwanted adhesive can be decomposed and removed simultaneously in the subsequent step of dry etching of the organic film  301 . This arrangement solves the problem of the channel being blocked by the excess adhesive or the electrode surface being covered therewith. 
     Since the normal patterning technique can be used, a high-precision flow path regulating member  3  can be formed at reduced costs. 
     In the present invention, the organic film  301  at other than the site masked by the mask layer  3   b  can be removed entirely by dry etching. Thus, when the film is bonded on the rear side of the head chip  1 A, the outer shape can be made greater than the size of the rear side of the head chip  1 A. This signifies substantially improved workability. In the conventional way of bonding the flow path regulating member, the size of the flow path regulating member must be determined to conform to the rear side of the head chip in advance, and the member must be formed in a size smaller than that of the head chip to ensure that the electrode pulled out and formed on the rear side of the head chip will not be covered. This makes it very difficult to achieve high-precision bonding of the flow path regulating member. Moreover, the flow path regulating member with an ink inlet having been formed in advance has been weakened, and tends to be deformed by the slightest force. This results in difficult bonding work, namely, difficult bonding by high precision positioning. However, all these problems are solved by the present invention. 
     Incidentally, the drive electrode  14  in the ink channel  12  is brought in direct contact with ink. Accordingly, when water based ink is used, a protective film must be coated on the surface of the drive electrode  14 . Further, the flow path regulating member  3  is also brought in direct contact with ink. When a solvent based ink is used, it is necessary to provide a protective film to protect the flow path regulating member  3  from the solvent. After the flow path regulating member  3  has been formed in the aforementioned manner, all the surfaces of the head chip  1 A, namely, the surface of each drive electrode  14  and the surface of the flow path regulating member  3  are preferably coated with a protective film  17 , as shown in  FIG. 10 . Here the drive electrode  14  is not illustrated. 
     A film made of paraxylylene and derivatives thereof (hereinafter referred to as “parylene film  17 ) is preferably used as a protective film  17  for coating. The parylene film  17  is a resin film made of a polyparaxylylene resin and/or its derivative resin. It is formed by the Chemical Vapor Deposition: CVD method) wherein the solid diparaxylylene dimer or its derivative is a source of vapor deposition. To be more specific, the paraxylylene radical produced by vaporization and thermal decomposition of the diparaxylylene dimer is adsorbed on the surface of the head chip  1 A, and a film is formed by polymerization. 
     There are various types of parylene films  17 . In response to required performances, various forms of parylene films, or a multi-layer parylene film made of a plurality of these parylene films laminated one on top of the other can be used as a desired parylene film  17 . 
     Such a parylene film  17  preferably has a thickness of 1 μm through 10 μm. 
     The parylene film  17  permeates fine areas to form a film. Thus, if the head chip  1 A is coated before the nozzle plate  2  is connected, the drive electrode  14  as well as the flow path regulating member  3  are protected against ink since both the inner surface facing the interior of the air channel  13  and the outer surface exposed to the rear side of the head chip  1 A are coated with the parylene film  17 . 
     The flow path regulating member  3  is protected on both sides by the formation of this parylene film  17 , with the result that the durability is greatly improved. 
     Even though a pin-hole occur to the parylene film  17  for coating the flow path regulating member  3  so that the solvent based ink permeates, the parylene film  17  per se does not dissolve, and continues to be present on both surfaces of the flow path regulating member  3 . Thus, it does not lose the function as the flow path regulating member  3 , and its reliability is maintained for a long period of time. 
     Moreover, as in the present embodiment, the flow path regulating member  3  is formed independently for each air channel  13 . Thus, the adverse effect of a pin-hole having occurred to the parylene film  17  is restricted to the flow path regulating member  3  alone, so that the flow path regulating members  3  of other air channels  13  are not affected. This arrangement provides an advantage that the damage is kept to a minimum. 
     Needless to say, regardless of the presence or absence of the parylene film  17 , the flow path regulating member  3  is formed independently for each air channel  13 . This arrangement ensures that other flow path regulating members  3  are not affected, even if separation or other defects have occurred to any of the flow path regulating members  3 . As described above, when these flow path regulating members  3  are to be formed independently for respective channels, they must be bonded one by one according to the conventional method, and this involves difficult work. In the present invention, however, they can be formed in one operation when they are formed independently for respective channels. This arrangement provides the aforementioned advantages easily. 
     After the parylene film  17  has been formed in the aforementioned manner, the nozzle plate  2  is connected to the front side of the head chip  1 A, as shown in  FIG. 10 . 
     The wiring board  4 , for example, as shown in  FIG. 11 , is connected to the rear side of the head chip  1 A, whereby the connection electrode  15  and common electrode  16  formed on the rear side of the head chip  1 A are electrically connected with the drive circuit (not illustrated). 
       FIG. 11  is a cross sectional view wherein the head chip  1 A connected with the wiring board  4  is cut at the air channel  13 . 
     The wiring board  4  is formed of a plate-formed substrate which is made up of a ceramic material such as a nonpolarizable PZT, AIN-BN and AIN. Plastic, glass of low thermal expansion or the like can also be used. Further, the same substrate material as that of the piezoelectric element substrate used in the head chip  1  can be used by depolarization. Further, to reduce the distortion of the head chip  1  resulting from the difference in coefficient of thermal expansion, the material is preferably selected so that the difference in the coefficient of thermal expansion from the head chip  1 A will be kept within ±1 ppm. The number of the materials constituting the wiring board  4  is not restricted to one. Several sheets of thin plate-formed substrate materials can be laminated to get a desired thickness. 
     The wiring board  4  extends in the direction perpendicular to the direction of a row of the channels of the head chip  1 A (in the vertical direction in  FIG. 11 ). The overhangs  41   a  and  41   b  that hang substantially over the upper side and lower side of the head chip  1 A are provided. Further, one concave portion  42  extending across the width (in the direction of channel row) is formed on one surface of the wiring board  4  connected with the rear side of the head chip  1 A. This concave portion  42  is provided with a groove large enough to cover the apertures  122  and  132  on the rear side of all the channels  12  and  13  in the direction of the channel row of the head chip  1 A. This constitutes a common ink chamber for supplying ink equally to each of the ink channels  12  (not illustrated in  FIG. 11 ). 
     To be more specific, as shown in  FIG. 11 , the height of the concave portion  42  in the vertical direction of the drawing is greater than that of each of the channels  12  and  13 , and is smaller than the thickness perpendicular to the direction of the channel row of the head chip  1 A. Thus, when the wiring board  4  is connected with the rear side of the head chip  1 A, the apertures  122  and  132  on the rear side of each of the channels  12  and  13  faces inside the concave portion  42 . 
     The flow path regulating member  3  is built in this concave portion  42 . To be more specific, the wiring board  4  is connected to a very narrow area on the rear side of the head chip  1 A where the flow path regulating member  3  is not provided. This area is very close to each of the channels  12  and  13  (e.g., the distance is 0 through 200 μm). This requires a very difficult and high-precision positioning work when one plate-formed flow path regulating member is connected in the conventional manner. However, in the present invention, the flow path regulating member  3  can be formed by patterning technique. This arrangement ensures high-precision positioning, as described above, and allows the channels  12  and  13  to be easily formed in a very close position. Further, the present invention easily provide an area for electrical connection between each connection electrode  15  (not illustrated in  FIG. 11 ) and common electrode  16 . Needless to say, even if adhesive oozes out into this area, it is decomposed and removed at the time of dry etching. Thus, electrical connection is immune to any trouble. 
     One of the overhangs  41   a  of the wiring board  4  is provided with the wired electrodes  43  (not illustrated in  FIG. 11 ) each having the same number and same pitch as those of the connection electrodes  15  formed on the rear side of the head chip  1 A. The other overhang  41   b  is provided with a wired electrode  44  for connection with the common electrode  16  formed on the rear side of the head chip  1 A. The wiring board  4  is connected to the rear side of the head chip  1 A by an anisotropic conductive film or the like so that each of the wired electrodes  43  will be electrically connected with each of the connection electrodes  15 , and the wired electrode  44  is electrically connected with the common electrode  16 . 
     When a wiring board  4  is connected to the rear side of the head chip  1 A, ink can be supplied to the concave portion  42  serving as a common ink chamber from both ends of the concave portion  42  or one of the ends. It is also possible to form an opening  45  leading from the bottom of the concave portion  42  to the surface opposite to the surface for connection with the head chip  1 A, and to further connect a box-shaped ink manifold  46  capable of storing the ink in the amount greater than that of the concave portion  42 , as shown in  FIG. 11 . 
     When a wiring board  4  is connected to the rear side of the head chip  1 A, the aforementioned parylene film  17  is formed preferably before the nozzle plate  2  is connected to the head chip  1 A after the wiring board  4  has been connected to the head chip  1 A. This arrangement ensures electrical connection between each of the connection electrodes  15  and common electrodes  16 , and each of the wired electrodes  43  and  44 , and allows a protective film to be formed on the surface of the wired electrodes  43  and  44  facing the concave portion  42  of the wiring board  4  which will be brought in direct contact with ink. 
     The following describes the second embodiment of the inkjet head of the present invention: 
       FIG. 12  is a perspective view of the head chip of the inkjet head of the second embodiment, as viewed from the rear side.  FIG. 13(   a ) is a cross sectional view showing the ink channel  12  of the inkjet head of  FIG. 12 , and  FIG. 13(   b ) is a cross sectional view of the air channel  13 . 
     The same reference numerals in  FIGS. 1 and 2  are assigned to the same components, which will not be described in details to avoid duplication. Further, the method of manufacturing this head chip  1 B is the same as that of  FIG. 3  and  FIG. 4 . 
     In the inkjet head of the second embodiment, the same flow path regulating member  31  as the flow path regulating member  3  in the first embodiment is formed in each air channel  13  of the head chip  1 B. At the same time, each ink channel  12  is provided with a flow path regulating member  32  independently so as to reduce the area of the aperture  122  on the rear side thereof. 
     To be more specific, the flow path regulating member  31  formed to conform to each air channel  13  is formed of a laminate made up of an organic film layer  31   a  on the side in contact with the head chip  1 B and the mask layer  31   b  on the surface thereof, whereby the aperture  132  on the rear side of each air channel  13  is completely blocked. The flow path regulating member  32  formed to conform to each of the ink channels  12  is formed of a laminate made up of an organic film layer  32   a  on the side in contact with the head chip  1 B and the mask layer  32   b  on the surface thereof. Part of the aperture  122  on the rear side of each of the ink channels  12  is exposed to reduce the area of the aperture. 
     In this flow path regulating member  32 , the direction of width in the direction of the channel row is slightly greater than the width of the ink channel  12 , and the vertical direction perpendicular to the direction of width is smaller than the height of the ink channel  12 . Accordingly, the aperture area is reduced by the flow path regulating member  32  to ensure that only the top end and bottom end of each of the apertures  122  on the rear side of the ink channel  12  will open. 
     The flow path regulating member  32  conforming to this ink channel  12  is only required to be formed by patterning, simultaneously with the formation of the flow path regulating member  31  conforming to the air channel  13 , using the same procedure as that for forming a flow path regulating member  3  in the first embodiment. Since this flow path regulating member  32  is also formed by patterning, this arrangement ensures high-precision reduction in the area of the aperture  122  on the rear side of each of the ink channels  12 . 
     When the wiring board  4  is to be connected after the flow path regulating members  31  and  32  have been formed as in the case of  FIG. 11 , a parylene film  17  is preferably formed on all the surfaces of the head chip  1 B, namely, on the surface of each of the drive electrode  14  and the surfaces of the flow path regulating members  31  and  32 , subsequent to connection, similarly to the case of  FIG. 10 . 
     In the head chip  1 B of the second embodiment, the area of the aperture  122  on the rear side of each of the ink channels  12  is reduced by the flow path regulating member  32 . This arrangement permits an effective reduction in the vibration of the ink meniscus of the nozzle when the head is driven at a high speed, similarly to the conventional case of using the flow path regulating plate with the ink inlet kept open. 
     Moreover, unlike the case of an ink inlet being formed at the center of the aperture of the ink channel as in the conventional art, this flow path regulating member  32  is designed in such a way that the top end and bottom end of the aperture  122  of the ink channel  12  are opened to form the apertures  122   a  and  122   b . Thus, when the inkjet head is placed in an inclined position, as shown in  FIG. 14 , so that the direction of emission of ink a will be inclined with respect to the direction of gravity g, the aperture (e.g., aperture  122   a ) which is not blocked by the flow path regulating member  32  is located at the top-most position for the ink channel  12 . Accordingly, the bubble b produced in the ink channel  12  is collected to this top-most position and is easily removed from the aperture  122   a  to enter the common ink chamber outside the head chip  1 B. Even if there is bubble b inside the common ink chamber, it does not affect ejectionany more. This eliminates the possibility of any problem being caused by bubble b. 
     The top end and bottom end of this aperture  122  is made to open by the flow path regulating member  32  formed so as to reduce the area of the aperture  122  on the rear side of the of each of the ink channels  12 . This arrangement provides a head characterized by excellent bubble removing performance and ejectionreliability. 
     In each of the ink channels  12 , the area of the aperture  122  on the rear side after having been narrowed by the flow path regulating member  32  is preferably 1 through 10 times the aperture area on the emission side of the nozzle  21  formed on the nozzle plate  2 , more preferably 2 through 5 times. The optimum value is preferably obtained from the result of an ejectiontest. According to the test made by the present inventors, the optimum area of the aperture  122  on the rear side after having been reduced by the flow path regulating member  32  is 2000 μm 2  for the head chip having a nozzle diameter of 28 μm (aperture area: 615 μm 2 ). 
     In this case, the flow path regulating member  32  was formed in such a way that both the top end and bottom end of the aperture  122  of the ink channel  12  are opened to form apertures  122   a  and  122   b , respectively. This arrangement allows the bubble b to be removed independently of whether the upper side or lower side of the head chip  1 B is located on the upper position, and does not preferably impose any restriction when the inkjet head is installed in a slanting direction. Without the present invention being restricted thereto, the flow path regulating member  32  can be formed in such a way that either the top end or bottom end alone in the aperture  122  on the rear side of the ink channel  12  is open. In this case, the inkjet head is installed in a slanting direction so that the open side of the apertures  122  on the rear side without being blocked by the flow path regulating member  32  is located on the upper position. This arrangement makes it possible to remove the bubble b. 
     The first embodiment and the second embodiment use an example of the independent channel type inkjet head wherein the channels arranged side by side on the head chips  1 A and  1 B were assigned alternately as ink channels  12  and air channels  13 . However, in the head chip, all the channels can be used as ink channels  12 . 
       FIG. 15  indicates the rear side of the head chip  1 C in the third embodiment when all the channels are used as ink channels  12 . The same reference numerals in  FIGS. 1 and 2  indicate the same structure, and will not be described in details. The manufacturing methods of this head chip  1 C in  FIG. 3  and  FIG. 4  are the same, therefore the connection electrodes  15  are formed for all the channels instead of the common electrodes  16  being formed. In this case as well, the drive electrode  14  is not illustrated. 
     As illustrated in the same drawing, a flow path regulating member  32  formed of the laminate made up of an organic film layer  32   a  and mask layer  32   b  is provided independently on the aperture  122  on the rear side of each of the ink channels  12  so as to reduce the area of the aperture  122 . In this case as well, the area of the aperture  122  on the rear side of each of the ink channels  12  is reduced by the flow path regulating member  32  so that the top end and bottom end are open. Thus, similarly to the case of  FIG. 14 , installation of the inkjet head in a slanting direction ensures easy removal of the bubble from the ink channel  12 . 
     The flow path regulating member  32  can be formed of one flow path regulating member so as to reduce the area of the apertures  122  on the rear sides of all the ink channels  12 . In this case as well, as illustrated, if it is formed independently for each ink channel  12 , other ink channels  12  are not affected by the problems of any of the flow path regulating members  32 . 
     In this embodiment, it goes without saying that the flow path regulating member  32  can be formed in such a way that either the top end or bottom end alone in the aperture  122  on the rear side of the ink channel  12  is open. 
     In the aforementioned description, the head chips  1 A,  1 B and  1 C constituting the inkjet head each have only one channel row. However, a plurality of channel rows can be used. In this case, the flow path regulating members  3 ,  31  and  32  can be applied in the same manner. 
     The aforementioned embodiment provides a method of manufacturing the inkjet head wherein a flow path regulating member can be pressed and firmly bonded on the rear side of a harmonica type head chip, without any possibility of the channel being blocked by adhesive, or the adhesive being oozed out. 
     Further, the aforementioned embodiment provides a method of manufacturing the inkjet head wherein a flow path regulating member can be pressed and firmly bonded without any possibility of the channel being blocked by adhesive, or the adhesive being oozed out, and wherein bubbles can be easily removed from the channel so that bubbles hardly remain inside, even if the area of the aperture on the rear side of the channel is reduced. 
     Furthermore, the aforementioned embodiment provides an inkjet head containing the flow path regulating member which can be firmly bonded on the rear side of a harmonica type head chip, without any possibility of the channel being blocked by adhesive, or the adhesive being oozed out. 
     Still further, the aforementioned embodiment provides an inkjet head containing the flow path regulating member which can be firmly bonded on the rear side of a harmonica type head chip, without any possibility of the channel being blocked by adhesive, or the adhesive being oozed out, wherein bubbles can be easily removed from the channel so that bubbles hardly remain inside, even if the area of the aperture on the rear side of the channel is reduced.