Abstract:
An ink jet recording head includes a recording element substrate; an electric wiring member including an array of leads connected to the recording element substrate at an electrical connecting portion; a supporting portion including a surface supporting the electric wiring member and a recessed bottom surface for supporting the recording element substrate; sealing material covering a part of an upper surface of the electric wiring member, the electrical connecting portion, a part of an upper surface of the recording element substrate, and the array of leads; and a projection provided between the electric wiring member and the recording element substrate at an end of the array. A level difference between upper surfaces of the projection and the recording element substrate is smaller than a level difference between the upper surfaces of the recording element substrate and the electric wiring member.

Description:
FIELD OF THE INVENTION AND RELATED ART 
     The present invention relates to an ink jet recording head, that is, a recording head which records an image on recording medium by jetting droplets of ink as recording liquid. It also relates to a method for manufacturing an ink jet recording head. 
       FIGS. 14A and 14B  show the general structure of an ink jet recording head (which hereafter will be referred to simply as “recording head”) in accordance with the prior art. The recording head shown in the drawings is made up of an ink container  100 , a recording element chip  200 , and an electrical wiring board  300 . Not only does the ink container  100  store ink, but also, serves as a supporting member, to which the recording element chip  200  and electrical wiring board  300  (which hereafter will be referred to simply as “wiring board”) are attached. Further, the recording element chip  200  and wiring board  300  are in connection with each other. They are connected by the following method. That is, unshown electrically conductive pads (electrodes), for example, metallic pads (bump made by gold plating, for example), are formed on the recording element chip  200  by a film forming process, a photolithographic process, a plating process, or the like. Then, the multiple leads with which the wiring board  300  is provided are bonded with the pads (electrodes) of the recording element chip  200  by the application of heat and load (which hereafter may be referred to as “inner lead bonding”, or ILB). It should be noted here that after the bonding of the pads (electrodes) of the recording element chip  200  with the leads of the wiring board  300 , the recording element chip  200  is bonded to the ink container  100  with adhesive, in order to prevent ink from leaking while it is supplied to the recording element chip  200  from the ink container  100  through the ink outlet of the ink container  100 . 
     It is possible that if the ink having adhered to the surface of the recording element chip  200 , at which the ink jetting outlets are open, flows onto the wiring board  300  which holds wiring formed of copper foil or the like, the ink may cause the wiring board  300  to short-circuit and/or corrode. Thus, in order to prevent this problem, the wiring board  300  is covered with a piece of cover film, on the side where the circuit formed of copper foil is present. The wiring board  300  is bonded to the ink container  100  with adhesive, by the side covered with the cover film. 
     Further, the peripheries of the recording element chip  200  is sealed with a first sealant  400 . In this specification, the sealing of the peripheries of the recording element chip  200  may be sometimes referred to as “peripheral sealing of chip”. It is possible that if the junction (electrical junction) between the pad (electrode) of the recording element chip  200  and the lead of the wiring board  300  becomes exposed, the minute ink droplets or the like having scattered from the ink jetting outlets will adhere to the junction and corrode it. Therefore, the electrical junctions are sealed with a second sealant  500 , which is formed of epoxy resin or the like, which is excellent as a sealant as well as an ion blocker. In this specification of the present invention, the sealing of the electrical joint by sealant may be sometimes referred to as “sealing of electrical junction”. 
     The first and second sealants  400  and  500 , which are used for the sealing of the peripheries of the recording element chip  200  and the sealing of the electrical junctions, respectively, are thermally hardened (cured). 
       FIGS. 15(A) ,  15 (B), and  15 (C) are schematic plan views of the recording head shown in  FIG. 14 , and show the states of the recording head, respectively, in which the recording head will be after the completion of the various steps in the manufacturing of the recording head. 
       FIG. 15A  shows the state of the precursor of the recording head, in which the precursor will be after the wiring board  300 , and the recording element chip  200  connected to the wiring board  300 , are attached to the ink container  100 .  FIG. 15(B)  shows the state of the precursor of the recording head, in which the precursor will be after the application of the first sealant  400  to the peripheries of the recording element chip  200 .  FIG. 15C  shows the state of the precursor of the recording head, in which the precursor will be after the application of the second sealant  500  to the electrical junctions between the wiring board  300  and recording element chip  200 . 
     As the sealant  400  for sealing the peripheries of the recording element chip, such a sealant that is highly fluid and is unlikely to stress the recording element chip as it hardens and/or after it hardens, is selected. On the other hand, as the second sealant  500  for sealing the electrical junctions formed by ILB, such a sealant that is significantly harder than the sealant used as the sealant  400  after it hardens is selected, in consideration of the durability related to the following facts. That is, the surface of the recording element chip, at which the ink jetting outlets are open, is wiped, as necessary, by a wiper blade, in order to remove the ink droplets having adhered to the surface. Therefore, the second sealant  500  is required to be hard enough to be resistant to friction wear. Further, it is possible that the second sealant  500  will come into contact with recording medium. Therefore, it is required that the second sealant  500  does not peel even if it comes into contact with recording medium. 
     Next, the sealing step will be described in more detail. Referring to  FIGS. 15B and 15C , the sealing step, which is one of the steps in an ink jet recording manufacturing process, is carried out in the order of the sealing of the peripheries of the recording element chip and the sealing of the electrical junctions made by ILB. Normally, a necessary amount of sealant is applied to the preselected areas of the recording head, with the use of a three axis robot (X-Y-Z axis robot), a dispenser, a syringe, a needle, etc. 
       FIG. 16  is a schematic drawing which shows how the electrical junctions made by ILB is sealed. As will be evident from the drawing, the second sealant  500  is applied onto the leads  301 , and the first sealing member  400  (applied in advance), by a needle  600 , which is moved in the direction indicated by an arrow mark. 
     It should be noted here that capillary force caused the first sealant  400 , that is, the sealant which was applied in advance to the peripheries of the recording element chip  200 , to fill every nook and corner of the abovementioned electrical junctions. Further, as the first sealant  400  was applied, the body of first sealant  400  between the adjacent two leads  301  was pulled upward by its surface tension, as high as the highest point of the leads  301 . Therefore, the body of first sealant  400  between the adjacent two leads  301  remains in the form into which the balance between its weight and the surface tension shaped it. The second sealant  500  is to be applied onto the first sealant  400  while the first sealant  400  is in the above-described state. As the second sealant  500  is applied, it airtightly adheres to the layer of first sealant  400 . 
     However, there occurred sometimes the following problem. That is, at the beginning and/or end of the step for applying the second sealant  500 , the second sealant  500  sank into the uncured layer of the first sealant  400 , and as it sank, it sometimes partially exposed the lead(s)  301 , allowing thereby ink to come into contact with the exposed portion(s) of leads, which resulted in electrical problems. 
     As for the solution to this problem, in the past, the following means have been adopted. That is, Japanese Laid-open Patent Application 2004-255866 discloses a liquid jetting head which had a significantly reduced distance between the edges of the recording element chip placement hole of the wiring board, and the corresponding edges of the recording element chip, compared to that of a liquid jetting head in accordance with the prior art. Further, Japanese Laid-open Patent Application H10-44442 discloses a liquid jetting head, which is provided with dummy leads for preventing the sealant from sinking after the sealant is applied. A dummy lead is a lead which does not have an electrical connection with a recording element chip. It is shorter than a normal lead, and is positioned next to the outermost lead of the group of leads arranged in parallel in the direction perpendicular to that in which the leads extend. 
     However, even in the case of the structural arrangement such as those disclosed in Japanese Laid-open Patent Applications 2004-255866 and H10-44442, there is a significant amount of difference in height between the top surface of the wiring board and the top surface of the recording element chip, which are partially coated with sealant(s) to cover the electrical junctions formed by ILB. This difference in height (step) is intentionally provided in order to prevent the “edge touch”, which is a phenomenon that the leads come into contact with the corner(s) of the lateral surface(s) of the recording element chip. That is, the design of the ink jet recording heads is such that as the recording element chip and wiring board are put together, the top surface of the wiring board is positioned higher than the top surface of the recording element chip. Further, referring to  FIG. 17  (which is an enlarged view of the adjacencies of the electrical junction shown in  FIG. 15B ), the wiring board is provided with overhangs  303 , which are provided to position the wiring board  300  as close as possible to the recording element chip  200  to support the second sealant  500  with the portion  303  to prevent the second sealant  500  from sinking. This design makes steeper the virtual line which connects the edge of the top surface of the wiring board  300  and the edge of the top surface of the recording element chip  200 . 
     The presence of this significant amount of difference in height (step) between the top surface of the wiring board  300  and the top surface of recording element chip  200  sometimes causes the body of sealant to be applied across the area which corresponds to the abovementioned virtual line which connects the edge of the top surface of the wiring board  300  and the edge of the top surface of the recording element chip  200 , to become “constricted”, that is, narrow (in terms of direction perpendicular to direction in which sealant is applied). If the body of sealant applied across the abovementioned area narrows by a large amount, it is possible that the lead(s) is partially exposed. If ink comes into contact with the exposed portion of a lead, electrical problems occur. 
     To concretely describe the cause of the above described narrowing of the body of applied sealant, referring to  FIG. 18 , there is an intentionally provided difference  800  (which is 0.1-0.15 mm) in height between the portion of the top surface of the wiring board  300 , across which the second sealant member  500  ( FIG. 6 ) is applied, and the top surface of the recording element chip  200 . 
     In  FIG. 19A , the second sealant  500  is applied across the aforementioned electrical junctions and their adjacencies, inclusive of where the abovementioned step is present. It is applied with a needle  600 . It is applied from the left-to-right direction of the drawing, while moving the needle  600  at a preset speed, and causing the needle  600  to extrude the sealant  500  at a preset rate. 
     While the needle  600  is moved across the area above the electrical junctions and their adjacencies (step  800  in  FIG. 18 ), that is, the area between the top surface of the wiring board and the top surface of the recording element chip, that is, while applying the second sealant  500  in the high-to-low direction, a part or parts of the electrical junctions and their adjacencies fail to be coated with the second sealant  500 . That is, while the needle  600  is moved across the immediately downstream or upstream side of the wiring board  300 , the body of second sealant  500  extruded from the needle  600  fails to completely cover the area to be covered, because the amount by which the second sealant  500  is extruded per unit length of time is insufficient to cover the entirety of the area to be covered by the second sealant  500 . Thus, the body of applied second sealant  500  locally narrows in terms of the direction perpendicular to the direction in which the second sealant  500  is applied. The thus created narrow portion of the body of applied second sealant  500  is the abovementioned “constricted portion” of the second sealant  500 . 
     To describe the cause of the narrowing of the body of applied second sealant in more detail with reference to  FIG. 19B , while the needle  600  is moved in the direction indicated by an arrow mark in the drawing to apply the second sealant  500 , as long as the rate (Q) at which the second sealant  500  is applied, the moving speed of the needle  600 , and the special volume ((size of area which can be covered with second sealant  500 , by needle  600 )×distance V from portion of surface to be covered to tip of needle  600 ) remain constant (V 1 =V 2 ), the body of sealant extruded from the needle  600  continuously forms a belt of second sealant  500  which is uniform in width. 
     In reality, however, while the needle  600  is moved across the edge of the wiring board and the immediately downstream side of the edge of the wiring board, the special volume V, that is, the volume of the space formed by the needle tip and the surface to be coated, suddenly changes (V 1 &lt;V 2 ). Thus, the needle  600  temporarily fails to supply the area with a sufficient amount of second sealant  500 . As a result, these areas are not coated with the second sealant  500 . In other words, each time the needle  600  fails to supply the second sealant  500  in the amount sufficient to accommodate the changes in the above described spatial volume V, the narrowing  700  of the body of applied second sealant  500  occurs. This phenomenon is likely to occur as the distance from the tip of the needle  600  to the surface to be coated suddenly increases, that is, when the needle  600  is moved across the edge of the wiring board  300  in the abovementioned direction. Further, the greater the application speed, the larger the portion of the area to be coated with the second sealant  500  which will fail to be coated, and therefore, the more conspicuous the narrowing  700  of the body of applied second sealant  500 . 
     If it is possible to eliminate the difference  800  in height, which is present between the top surface of the wiring board and the top surface of the recording element chip, it is possible to prevent the occurrence of the narrowing. However, this step difference  800  in height is intentionally provided to prevent the “edge touch”, as described above. Therefore, it is not allowed to eliminate the difference  800  in height to make the top surface of the wiring board level with the top surface of the recording element chip. 
     Further, when it is necessary to shorten the processing time for productivity, and/or if the length by which the sealant is to be applied becomes longer, because the recording element chip is widened for image quality, and therefore, the number of electrical junctions formed by ILB increases, the speed at which the sealant is applied must be further increased. However, it is possible that the increase in the sealant application speed results in the more frequent occurrence of the narrowing of the second sealant attributable to the above described step difference in height between the wiring board and recording element chip, which might result in the decline in productivity as well as yield. 
     SUMMARY OF THE INVENTION 
     Thus, the present invention can provide an ink jet recording head, having a wiring board and recording element chip which are different in height relative to where the recording element chip is attached, being thereby prevented from making direct contact with each other, and having a second sealant which does not have a constricted (narrow) portion. 
     According to an aspect of the present invention, there is provided an ink jet recording head comprising a recording element substrate having an ejection outlet for ejecting ink; an electric wiring member connected to said recording element substrate at an electrical connecting portion to supply electric power to said recording element substrate, said electric wiring member including an array of leads; a supporting portion for supporting said recording element substrate and said electric wiring member, said supporting portion includes a surface supporting said electric wiring member and a recessed bottom surface for supporting said recording element substrate, wherein said supporting surface is recessed in a recess of the bottom surface; a sealed region of sealing material sealing said electric wiring member, said sealed region covering a part of an upper surface of said electric wiring member, the electrical connecting portion, a part of an upper surface of said recording element substrate, and said array of leads; and a projection provided between said electric wiring member and said recording element substrate at an end, with respect to a direction of arrangement of the array, of said array in said sealed region, wherein a level difference between an upper surface of said projection and an upper surface of said recording element substrate is smaller than a level difference between the upper surface of said recording element substrate and the upper surface of said electric wiring member. 
     According to another aspect of the present invention, there is provided a manufacturing method for an ink jet recording head, said method comprising a step of preparing a recording element substrate having an ejection outlet for ejecting ink; a step of preparing an electric wiring member connected to said recording element substrate at an electrical connecting portion to supply electric power to said recording element substrate, said electric wiring member including an array of leads; a step of preparing a supporting portion for supporting said recording element substrate and said electric wiring member, said supporting portion includes a surface supporting said electric wiring member and a recessed bottom surface for supporting said recording element substrate, wherein said supporting surface is recessed in a recess of the bottom surface; a step of providing a projection between said electric wiring member and said recording element substrate at an end, with respect to a direction of arrangement of the array, of said array in said sealed region, wherein a level difference between an upper surface of said projection and an upper surface of said recording element substrate is smaller than a level difference between the upper surface of said recording element substrate and the upper surface of said electric wiring member; and a step of applying sealing material, along the direction from a side where said projection is provided, to provide a sealed region to seal said electric wiring member, said sealed region covering a part of an upper surface of said electric wiring member, the electrical connecting portion, a part of an upper surface of said recording element substrate, and said array of leads. 
     These and other objects, features, and advantages of the present invention will become more apparent upon consideration of the following description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic plan view of a part of the bottom of the ink container of the ink jet recording head in the first embodiment of the present invention, showing the downwardly facing side of the ink container. 
         FIG. 2  is a schematic plan view of a part of the downwardly facing side of the ink container of the ink jet recording head shown in  FIG. 1 , showing the bottom surface of the ink container, to which the recording element chip and wiring board have been attached. 
         FIG. 3  is a schematic sectional view of the precursor of the ink jet recording head, shown in  FIG. 2 , at Plane A-A in  FIG. 2 . 
         FIG. 4  is a sectional view of the precursor of the ink jet recording head, shown in  FIG. 2 , at Plane B-B in  FIG. 2 . 
         FIG. 5  is a schematic drawing which shows the flow of the first sealant. 
         FIGS. 6A and 6B  are schematic drawings which describe the result of the experiment in which the electrical junctions of a conventional ink jet recording head, which was made by ILB, were sealed with the sealants. 
         FIGS. 7A and 7B  are schematic drawings which describe the result of the experiment in which the electrical junctions of the conventional ink jet recording head in this embodiment, which was made by ILB, were sealed with the sealants. 
         FIG. 8  is a schematic bottom view of the ink container of the ink jet recording apparatus in the second embodiment of the present invention. 
         FIG. 9  is a schematic bottom view of a part of the ink container of the ink jet recording head shown in  FIG. 8 , showing the bottom surface of the ink container to which the recording element chip and wiring board have been attached. 
         FIG. 10  is a sectional view of the precursor of the ink jet recording head, shown in  FIG. 9 , at Plane A-A in  FIG. 9 . 
         FIGS. 11A ,  11 B, and  11 C are schematic drawings of the modified version of the ink jet recording head in the second embodiment of the present invention. 
         FIG. 12  is a schematic drawing which shows how, where, and why bubbles collect in the corners of the recording element chip placement recess when the first sealant is applied. 
         FIGS. 13A ,  13 B,  13 C and  13 D are schematic drawings of the ink jet recording head in the third embodiment of the present invention. 
         FIGS. 14A and 14B  are schematic perspective views of the ink jet recording head in accordance with the prior art, showing the general structure of the ink jet recording head. 
         FIGS. 15A ,  15 B, and  15 C are schematic drawing of the precursors of the ink jet recording head in accordance with the prior art, showing the steps, one for one, of the process for manufacturing the ink jet recording head. 
         FIG. 16  is a schematic drawing which shows how the electrical junctions made by ILB are sealed. 
         FIG. 17  is an enlarged view of the electrical junctions prior to the application of the second sealant thereto. 
         FIG. 18  is a schematic drawing which shows the difference in height (relative to bottom surface of recording element chip placement recess) provided between the top surface of wiring board and the top surface of recording element chip to prevent the “edge touch”. 
         FIGS. 19A and 19B  are schematic drawings which show the cause of the local narrowing of the second sealant. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiment 1 
     Hereinafter, the ink jet recording head (which hereafter will be referred to as “recording head”) in one of the preferred embodiments of the present invention will be described in detail with reference to the appended drawings. 
       FIG. 1  is a plan view of the bottom of the ink container  100  of the recording head in this embodiment, and shows the structure of the bottom. As will be evident from the drawing, the bottom surface of the ink container  100  is provided with a wiring board attachment area  102 , that is, the area to which the wiring board  300  ( FIG. 2 ) is bonded with adhesive. The area  102  is the bottom surface, in true sense, of the ink container  100 , which supports the wiring board  300 . The wiring board supporting area  102  is provided with a recess  103 , which occupies the center portion of the area  102 , and the bottom surface  103   b  of which is recessed by a preset distance from the wiring board supporting area  102 . It is to the bottom surface  103   b  of the recess  103  that the recording element chip  200  is bonded with adhesive. In other words, the ink container  100  doubles as the component which supports the recording element chip  200  and wiring board  300 . 
     The ink container  100  is also provided with multiple ink outlets  104  through which ink is supplied to the recording element chip  200  from the ink container  100  (unshown), and which open at the bottom surface  103   b  of the recess  103 . After ink is supplied to the recording element chip  200 , it is jetted, in the form of an ink droplet, out of the recording element chip  200  through the ink outlets of the recording element chip  200 , toward recording medium. 
     The ink container  100  is also provided with four projections  101 , which are integral with the ink container  100 . The four projections  101  protrude from the four corner areas of the bottom surface  103   b  of the recess  103 , one for one (drawing shows only two of four projections  101 ). More specifically, each projection  101  is formed as an integral part of the ink container  100 , of a resinous substance. Incidentally, the projection  101  does not need to be an integral part of the ink container  100 . That is, it may be attached to the ink container  100  after being formed independently from the ink container  100 . From the standpoint of the object of the present invention, even if the projection  101  is not formed as an integral part of the ink container  100 , its effect is the same as that of the one formed as an integral part of the ink container  100 . 
     Referring to  FIG. 2 , the recording element chip  200  is provided with multiple metallic bumps  202 , which are formed by plating, whereas the wiring board  300  is provided with multiple leads  301 . The recording head  200  is fitted in the recess  103 , and its bumps  202  are bonded with the multiple leads  301  of the wiring board  300 , one for one, establishing electrical connection between the recording head  200  and wiring board  300 . Thus, the electric power for driving the ink jet recording head can be transmitted to the recording element chip  200  from an external power source. More concretely, the multiple leads  301  of the wiring board  300  are laid, by their end portions, on the multiple bumps  202  (formed along edges of recording element chip  200 ) of recording element chip  200 , one for one, and heat and pressure is applied to the points of contact between the bumps  202  and leads  301  to weld the leads  301  to the bumps  202  one for one (inner lead bonding). It should be noted here that among the multiple leads  301  shown in the drawing, a pair of leads  301   a , located at the ends, one for one, in terms of the direction parallel to the direction in which the leads  301  of the wiring board  300  arranged in parallel, are dummy leads, that is, leads which are not intended for electrical connection. 
     Incidentally, in this embodiment for concretely describing the present invention, the pair of end leads in terms of the abovementioned direction are dummy leads. However, the end leads do not need to be dummies. That is, the leads which are next to the projection  101  may be real leads, that is, electrical leads for electrical connection. 
     The projection  101  is between one of the end leads of the abovementioned group of leads  301  (inclusive of dummy leads  301   a ), and the edge  302  of the hole of the wiring board  300 , which accommodates the recording element chip  200 . The distance (d 1 ) from the edge of the recording element chip  200  to the projection  101  is desired to be as small as possible; the gap between the edge of the recording element chip  200  and the projection  101  is desired to be the smallest one which can be afforded based on the current level of precision at which the components of an ink jet recording head can be manufactured and assembled. Further, it is desired to be no more than the interval between the adjacent two leads  301 . 
       FIG. 3  is a schematic sectional view of the precursor of the ink jet recording head shown in  FIG. 2 , at Plane A-A in  FIG. 2 . As is evident from  FIG. 3 , from the standpoint of minimizing the difference in vertical distance between the highest and lowest points of the area to be coated with the second sealant  500 , the height of the projection  101  is desired to be as close as possible to the distance from the bottom  103   b  of the recess  103  to the surface (top surface) of the recording element chip  200 . 
       FIG. 4  is a schematic sectional view of the precursor of the ink jet recording head shown in  FIG. 2 , at Plane B-B in  FIG. 2 . As shown in  FIG. 4 , there is a space between each projection  101  and the adjacent lateral wall  103   a  of the recess  103 . This space is for ensuring that when the first sealant  400  is applied to the peripheries of the recording element chip  200 , there will be a passage which allows the first sealant  400  ( FIG. 5 ) to circumvent the recording element chip  200  to reach the underside of the leads  301 . 
       FIG. 5  is a schematic plan view of the adjacencies of the electrical junctions and projections  101 , and shows where and how the first sealant  400  circumvents the recording element chip  200 . The first sealant  400  is applied to the peripheries of the recording element chip  200 , more specifically, the gaps between the edges of the recording element chip  200 , which are perpendicular to the edges along which the metallic pads are arranged. It is applied with the use of a dispenser, which is moved along the abovementioned edges of the recording element chip  200 . After the first sealant  400  is applied, it flows into the under side of the leads  301  as shown by arrow marks in  FIG. 5 . That is, the body of first sealant  400 , which enters the underside of the leads  301  from one side of the recording element chip  200 , joins with the body of sealant  400 , which enters the underside of the leads  301  from the other side, filling up thereby the space under the leads  301 . As long as the first sealant  400  is allowed to flow into the underside of the leads  301  by an amount large enough to fill up the space under the leads  301 , the values for the distances (d 1 ) and (d 2 ) shown in  FIG. 3  are optional. For example, the testing of a recording head chip produced for testing, with the distances (d 1  and d 2 ) set to 0.14 mm and 0.5 mm, respectively, confirmed that the first sealant  400  flowed into the space under the leads  301  by an amount large enough to fill up the space. 
     As described above, when the recording head in this embodiment was manufactured, the gaps between the recording element chip  200  and wiring board  300  were filled with the first sealant  400  by applying the first sealant  400  into the gaps which are between the recording element chip  200  and the lateral walls  103   a  of the recess  103 , and which extend in the lengthwise direction of the recording head  200 . 
     Referring again to  FIG. 4 , from the standpoint of preventing the above described “edge touch”, the ink container  100  is designed so that after the fitting of the recording element chip  200  into the recess  103  of the bottom wall of the ink container  100 , there will be the difference  800  in height between the top surface of the recording element chip  200  and the top surface of the wiring board  300 . 
     Further, in order to prevent the problem that the electrical junctions between the recording element chip  200  and wiring board  300  corrode due to the adhesion of ink droplets or the like to the junctions, the second sealant  500  is applied in a manner to cover the electrical junctions after the peripheries of the recording element chip  200  are completely coated with the first sealant  400 . 
     The actual method used for applying the second sealant  500  is the same as the conventional method shown in  FIG. 16 . That is, as the first sealant  400  is applied to the peripheries of the recording element chip  200 , it moves into the space under the leads  301  of the wiring board  300 , and fills up the space, because of its generation of capillary force. Further, as the first sealant  400  enters the space between the adjacent two leads  301  (inclusive of dummy leads  301   a ), it is pulled up by its surface tension, high enough for its top surface to become level with the highest portion of the leads  301 . Thus, the body of first sealant  400  in the space between the adjacent two leads  301  is formed into, and remains in, a shape into which it is formed by the balance between its own weight and surface tension. The second sealant  500  is applied to the first sealant  400 , directly onto the layer of first sealant  400 , or with the presence of the leads  301  between the second sealant  500  and the layer of first sealant  400 , so that it airtightly adheres to the layer of first sealant  400  as well as the leads  301  ( FIG. 16 ). 
     After the application of the first and second sealants  400  and  500 , the two layers of sealants  400  and  500  are thermally hardened. 
     The ink jet recording head, in this embodiment, manufactured through the steps described above, has a portion in which a part of the top surface of the wiring board  300 , a part of each of the electrical junctions, a part of the top surface of the recording element chip  200 , and multiple parallely positioned leads  301 , are sealed with the layer of first sealant  400  and/or the layer of second sealants  500 . It also has the four projections  101 , which are in the four corner portions of the recess  103 , one for one; more specifically, each projection  101  is between one of the two walls of the recording element chip accommodating hole of the wiring board, which is parallel to the lengthwise direction of the recording element chip  200 , and one of the lengthwise edges of the recording element chip  200 . The difference in height (relative to bottom surface  301   a  of recess  301 ) between the top surface of the projection  101  and the top surface of the recording element chip  200  is less than that between the top surface of the recording element chip  200  and the top surface of the wiring board  300 . 
     The recording head in this embodiment is provided with a recording element chip unit attached thereto through the above described steps. 
     As will be evident from the above given description of this embodiment, the recording head in this embodiment has the multiple projections  101 , which are on the outward side of the dummy leads  301   a  which makes up the outermost leads of the group of leads, in terms of the direction perpendicular to the lengthwise direction of the recording element chip  200 . The difference in height (relative to bottom surface  301   b  of recess  301 ) between the top surface of the recording element chip  200  and the top surface of the projection  101  is smaller than that between the top surface of the recording element chip  200  and the top surface of the wiring board  300 . That is, the ink jet recording head in this embodiment is designed so that in terms of its thickness direction, the top surface of the projection  101  is between the top surface of the recording element chip  200  and the top surface of the wiring board  300 . 
       FIGS. 6A and 6B  show the results of the experiment in which the sealants were applied to seal the electrical junctions of a conventional ink jet recording head, which were made by ILB, whereas  FIGS. 7A and 7B  show the results of the experiment in which the sealants were applied to seal the electrical junctions of the ink jet recording head in this embodiment, which were made by ILB. Incidentally, the experiments were carried out under the following conditions: 
     &lt;Conditions&gt; 
     Sealant: thermally curable epoxy resin (250 Pa·s/25° C.) 
     Application speed: 8.0 mm/s 
     Line of Application: straight line parallel to direction in which leads are arranged in parallel. 
     Referring to  FIG. 6B , there is a substantial difference  800  in height (relative to bottom surface  301   b  of recess  301 ) of roughly 0.1-0.15 mm (within roughly 0.1 mm) between the edge of the top surface of the wiring board  300 , which is adjacent to the point at which the application of second sealant  500  is started to seal the electrical junctions made by ILB, and the edge of the top surface of the recording element chip  200 . As the second sealant  500  is applied in the direction indicated by an arrow mark in  FIG. 6A , it is affected by the abovementioned difference  800  in height. That is, it was confirmed that the body of second sealant  500  reduced in width on the downstream side (in terms of the direction in which the second sealant  500  is applied) of the edge of the wiring board  300 ; in other words, the body of second sealant  500  became “narrow”, as it was applied. 
     In comparison, referring to  FIGS. 7A and 7B , in the case of the recording head in this embodiment, it was confirmed that even when the second sealant  500  was applied under the same condition as that under which the second sealant  500  is applied to the electrical junctions of a conventional ink jet recording head, the narrowing  700  of the body of applied second sealant  500 , as shown in  FIG. 6A , did not occur. Incidentally, it was confirmed by this experiment that even when there was a height difference of roughly 20 μm-70 μm between the top surface of the projection  101  and the top surface of the recording element chip  200 , the narrowing  700  of the body of applied second sealant  500  did not occur. 
     It is reasonable to think from the above given description of this embodiment that as long as the requirement that the ink container  100  is to be provided with the abovementioned projections  101  before the starting of the application of the sealant, and the requirement that the sealants are to be applied from the side where one of the projection  101  is located, in the direction parallel to the direction in which the multiple leads are disposed in parallel, are satisfied, the body of applied second sealant  500  does not locally narrow. 
     Embodiment 2 
     Next, the recording head in the second embodiment of the present invention will be described. The recording head in this embodiment is the same in structure as the recording head in the first embodiment. Therefore, the structural components of the recording head in this embodiment, which are the same as the counterparts in the first embodiment, are given the same referential symbols as those given to the counterparts, and will be described. 
       FIG. 8  is a schematic plan view of a part of the bottom of the ink container  100  of the recording head in this embodiment, and shows the general structure thereof.  FIG. 9  is a schematic plan view of the same portion of the ink container  100  of the recording head in this embodiment as that shown in  FIG. 8 , after the wiring board  300  was bonded to the preset wiring board attachment area  102  of the ink container  100 , the recording element chip  200  was bonded to the bottom surface of the recess  103 , and electrical connection was made, by ILB, between the wiring board  300  and recording element chip  200 .  FIG. 10  is a schematic sectional view of the precursor of the recording head, which is in the state shown in  FIG. 9 , at Plane A-A in  FIG. 9 . 
     As will be evident from these drawings, the recording head in this embodiment also is provided with the projections  101 , which are on the bottom surface  103   b  of the recess  103  of the ink container  100 . However, it is different from the recording head in the first embodiment in that it is provided with only one projection  101 , per lengthwise end of the recording element chip  200 , which is located on the outward side of the recording head relative to the end lead (which in this embodiment is dummy lead  301   a , that is, leftmost lead in  FIG. 9 ) in terms of the direction in which the leads are arranged in parallel. 
     In the sealant application step in the manufacturing of the recording head in this embodiment, the unshown second sealant is applied in the direction indicated by an arrow mark in  FIG. 10 . That is, the application of the sealant is started from the side where the projection  101  is located. 
     It should be noted here that there is a space between the lateral wall  103   a  of the recess  103  and the projection  101  as shown in  FIG. 10 . Also, it is desired that the distance (d 1 ) between the recording element chip  200  and projection  101  is as small as possible; the gap between the edge of the recording element chip  200  and the projection  101  is desired to be the smallest one which can be afforded based on the current level of precision at which the components of an ink jet recording head can be manufactured and assembled. Further, it is desired to be less than the interval between the adjacent two leads  301 . 
     Also in the case of the recording head in this embodiment, the presence of the projection  101  reduces the difference in height between the edge of the wiring board  300 , which is in the adjacencies of the second sealant application starting point, and the recording element chip  200 . Therefore, it prevents the problem that the body of applied second sealant becomes locally narrow as it is applied. 
     Further, the wiring board  300  in this embodiment is provided with overhangs  303  which extend in a manner to cover the corresponding corner portions of the recess  103 . More specifically, referring to  FIGS. 9 and 10 , the overhang  303  is located on the opposite side of the recess  103  from where the projection  101  is present. It extends toward the projection  101 . 
     Incidentally, the wiring board  300  may be provided with four overhangs  303 , which extend over the four corners of the recess  103 , one for one, as shown in  FIGS. 11A-11B . In this case, the ink container  100  is provided with four projections  101 , which protrude from the four corner areas of the bottom surface  103   b  of the recess  103  of the ink container  100 . Further, referring to  FIG. 11C , each overhang  303  partially overlaps with the top surface of the corresponding projection  101 , although the bottom surface of the overhang  303  is not in contact with the top surface of the projection  101 . 
     Also referring to  FIG. 11C , the distance (d 4 ) between the projection  101  and recording element chip  200  is smaller than the distance (d 3 ) between the overhang  303  and recording element chip  200 . That is, in terms of the direction in which the leads  301  are arranged in parallel, the projection  101  is closer to the recording element chip  200  than the overhang  303  (d 4 &lt;d 3 ). Further, the height of the projection  101  relative to the bottom surface  103   b  is roughly the same as that of the recording element chip  200  after the bonding of the chip  200  to the ink container  100 . More specifically, the height of the projection  101  is such that the difference in height between the top surface of the recording element chip  200  and the top surface of the projection  101  is smaller than that between the top surface of the recording element chip  200  and the top surface of the wiring board  300 , and also, such that the height of the top surface of the projection  101  is as close as possible to that of the recording element chip  200 . 
       FIG. 11B  shows the precursor of the recording head in the condition in which the precursor will be after the application of the first and second sealants  400  and  500  to the peripheries of the recording element chip  200 . The second sealant  500  has been applied so that it extends from the application start point, which is on one of the overhangs  303  of the wiring board  300 , to the application ending point, which is on the other overhang  303 , so that all the real leads  301  and dummy leads  303   a , which are between the two overhangs  303  ( FIG. 11A ), are completely covered with the second sealant  500 . 
     If the overhang  303  of the wiring board  300  overlaps with the projection  101 , it is possible that when the first sealant  400  flows into the space under the leads  301  by circumventing the recording element chip  200 , bubbles will collect in the corners of the recess  103 . This problem occurs because as the first sealant  400  applied to the peripheries of the recording element chip  200  flows into the closed space surrounded by the lateral walls of the recess  103 , corresponding lateral surfaces of the projection  101 , the bottom surface of the overhang  303 , and the advancing body of first sealant  400 , while swallowing air, by circumventing the recording element chip  200 . If bubbles collect in the abovementioned corners, it is possible that when the layer of first sealant  400  is thermally cured, the layer of the first sealant  400  will be disturbed in shape by the expansion of the bubbles. 
     In this embodiment, therefore, if the recording head is designed so that the overhang  303  of the wiring board  300  overlaps with the projection  101 , it is desired that the recording head is also designed so that there is no space between the projection  101  and the corresponding lateral wall  103   a  of the recess  103 . As long as there is no space between the projection  101  and the corresponding lateral wall  103   a  of the recess  103 , that is, as long as no space is present between the projection  101  and the lateral wall  103   a  of the recess  103 , the advancing body of first sealant  400  does not create the abovementioned closed space, and therefore, no bubble collects in the corners. 
     Incidentally, choosing a point on the smooth top surface of one of the overhangs  303  of the wiring board  300 , which, as the first sealant application starting point, and a point on the smooth top surface of the other overhang  303 , as the first sealant application ending point, has a merit in that it makes it easier to determine the position and shape of the body of the applied sealant, when examining the position and shape of the body of applied sealant by detecting the position of edges using an image processing method. 
     Embodiment 3 
     Next, referring to  FIGS. 13A ,  13 B,  13 C and  13 D, the recording head in the third embodiment of the present invention will be described. 
       FIG. 13A  is a schematic plan view of a part of the downwardly facing side of the ink container  100  of the recording head in this embodiment.  FIG. 13B  is a schematic plan view of the downwardly facing side of the ink container  100  after the bonding of the wiring board  300  to the wiring board attachment area  102  of the ink container  100 , bonding of the recording element chip  200  to the bottom surface  103   b  of the recess  103 , and electrical connection of the wiring board  300  to the recording element chip  200  by ILB.  FIG. 13C  is a schematic sectional view of the electrical junctions between the wiring board  300  and recording element chip  200 , and their adjacencies, at Plane E-E in  FIG. 13B .  FIG. 13D  is a schematic sectional view of the ink container  100 , at Plane F-F in  FIG. 13B . 
     The basic structure of the recording head in this embodiment is the same as that of the recording head in the above described first embodiment. Therefore, the structural features of the recording head in this embodiment, which are the same as those of the recording head in the first embodiment, will not be described; only the different features of this recording head from those of the recording head in the first embodiment will be described below. 
     The recording head in this embodiment is different from the recording head in the first embodiment only in the shape of the top surface of the projection  101 . More concretely, referring to  FIG. 13D , the top surface of the projection  101  in this embodiment is partially curved in such a form that its curvature matches the curvature of each lead  301  and each dummy lead  301   a  ( FIG. 13C ), which extend from the edge  302  of the recording element chip accommodating hole of the wiring board  300 . Incidentally, in this embodiment, in order to prevent the edge  302  of the recording element chip accommodating hole of the wiring board  300  from overlapping with the top surface of the projection  101 , the overhang  303  is rendered shorter than the overhang  303  in the second embodiment. 
     In this embodiment, the top surface of the projection is curved in such a form that its curvature matches those of each lead  301  and each dummy lead  301   a . Therefore, as the second sealant  500  (unshown) is applied to cover the group of leads  301 , it smoothly flows, being therefore unlikely to become locally narrow. From the standpoint of allowing the second sealant to flow smoothly (flatly), the projection  101  may be formed so that the top surface has an angle which approximates the curvatures of the lead  301  and dummy lead  301   a.    
     The projection  101  shaped as described above can be easily formed by one of the known methods, for example, injection molding. Further, the projection  101  can be easily modified in the shape of its top surface by modifying in shape the metallic mold for the projection  101 . 
     As described above, the recording heads in the above described first to third embodiments are significantly smaller in the difference in height (relative to bottom surface of recording element chip placement recess of ink container) between the surface area of the wiring board, to which sealant is to be applied, and the surface area of the recording element chip, to which sealant is to be applied, than a recording head in accordance with the prior art. Therefore, after sealant is applied to the abovementioned area, it remains stable in shape. In other words, the present invention makes it possible to more reliably apply the sealant at a higher speed, making it thereby possible to improve an ink jet head manufacturing process in productivity. 
     While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth, and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claims. 
     This application claims priority from Japanese Patent Application No. 096408/2007 filed Apr. 2, 2007, which is hereby incorporated by reference.