Abstract:
A recording head includes a first ejection outlet array having a plurality of ejection outlets for ejecting liquid; a second ejection outlet array having a plurality of ejection outlets for ejecting liquid, the second ejection outlet array extending along a direction in which the first ejection outlet array extends such that second ejection outlet array is not overlapped with the first ejection outlet array in the direction or a direction perpendicular to the direction, wherein an end portion of the first ejection outlet array is disposed to an end of the second ejection outlet array; and a plurality of supplementing ejection outlets disposed close to at least one of the end portions or the first ejection outlet array and the second ejection outlet array such that supplementing ejection outlets are overlapped with another one of the end portions in the direction in which the first ejection outlet array extends, wherein the supplementing ejection outlets are disposed at an interval which is different from an interval at which the ejection outlets of the first ejection outlet array are disposed.

Description:
FIELD OF THE INVENTION AND RELATED ART 
     The present invention relates to a recording head which ejects recording liquid onto the recording surface of recording medium to carry out a recording operation, and a recording apparatus equipped with such a recording head. 
     Ink jet recording head units can be categorized into roughly two types: a “side shooter type” as shown in  FIG. 23 , and an “edge shooter” type as shown in FIG.  26 .  FIG. 23  shows a part of an ink jet recording head unit of the “side shooter” type, which is disposed in such a manner that the surface having ejection orifices squarely faces the recording surface of the recording medium. 
     The ink jet recording head unit has a supporting member  2 , a set of head chips  6 A, and a set of head chips  6 B. The supporting member  2  is positioned on the main assembly side of a recording apparatus. Each of the heads chips  6 A and  6 B has a plurality of ink ejection orifices. The head chips  6 A are disposed on one side of the flat surface of the supporting member  2 , and the head chips  6 B are disposed on the other. 
     More specifically, the plurality of head chips  6 A are aligned, for example, in the direction perpendicular to the direction, indicated by an arrow mark S, in which the ink jet recording head, which carries out a recording operation, is moved, and so are the plurality of head chips  6 B. The head chips  6 A are disposed with the provision of a predetermined interval between the adjacent two head chips  6 A, and so are the head chips  6 B. The line in which the head chips  6 A are aligned is roughly parallel to the line in which the head chips  6 B are aligned. Further, the set of head chips  6 A and the set of head chips  6 B are positioned so that the position of each head chip  6 B corresponds to the position of the interval between the two head chips  6 A adjacent to this head chip  6 B, while the position of each head chip  6 A corresponds to the position of the interval between the two head chips  6 B adjacent to this head chip  6 A. In other words, the set of head chips  6 A and set of head chips B are offset relative to each other in the direction in which the head chips are aligned, so that the head chips  6 A and head chips  6 B are arranged in the zigzag fashion. Further, the head chips  6 A and head chips  6 B are disposed in the recesses, one for one, of the aforementioned flat surface of the supporting member  2 , being fixed thereto. In each recess, there is the opening of one of the ink supply paths leading to the common ink chamber, from which ink is supplied to the head chips  6 A and head chips  6 B. 
     Essentially, each of the head chips  6 A and  6 B comprises: an ejection clement substrate, and a grooved plate. The ejection element substrate has a plurality of electrothermal transducers, as an ejection energy generation member, arranged with the provision of predetermined intervals. The grooved plate has a plurality of grooves and a recess, which are precisely positioned across one of its surfaces. As the grooved plate is laid on the ejection element substrate, a plurality of branches of liquid paths leading one for one to the ejection orifices, and the common liquid chamber from which the plurality of branches of liquid paths originate, are formed. 
     Each of the head chips  6 A and  6 B is relatively precisely positioned with the use of the image processing technologies, for examples. Each head chip  6 A ( 6 B) has a plurality of electrothermal transducers disposed, one for one, in the liquid paths leading to the ink ejection orifices, one for one, for example, and are electrically connected to the wiring substrate  4 A ( 4 B) surrounding the ejection element substrate. 
     The grooved plate has a plurality of ejection orifices, which squarely oppose, one for one, the electrothermal transducers on the ejection element substrate, in terms of the direction parallel to the thickness direction of the electrothermal transducers. Each head chip  6 A has ejection orifices  8   ai  (i=1−n, n being integer), and each head chip  6 B has ejection orifices  8   bi  (i=1−n, n being integer). The ejection orifices are aligned, for example, in two lines which are approximately parallel to each other, so that the ejection orifices in one line are offset relative to the corresponding ejection orifices in the other line; in other words, they are positioned in the zigzag manner, as shown in FIG.  24 (A). 
     With the provision of the above described structural arrangement, as a driving signal is supplied to any of the electrothermal transducers on the ejection element substrate, through the wiring substrates  4 A or  4 B, the body of ink surrounding this electrothermal transducer, in the corresponding branch of ink path, instantly boils, generating pressure. As a result, liquid droplets are ejected from the ejection orifice  8   ai  or  8   bi , corresponding to this electrothermal transducer, in the direction indicated by the arrow marks in  FIG. 23 , forming image regions GA and GB on the recording surface of recording medium, as shown in FIG.  25 (A). The image region GA. In FIG.  25 (A) is formed by the Ink droplets ejected from one of the head chips  6 A as it is moved relative to the recording surface of the recording medium in the arrow direction S, and the image region GB is formed by the ink droplets ejected from one of the head chips B as it is moved relative to the recording surface of the recording medium in the arrow direction S. The image region GA is made up of a set of a plurality of picture elements (dots) IDA, each of which was formed by the ink droplet which landed on, and adhered to, one of the predetermined points on the recording surface of the recording medium, and the image region GB is made up of a set of a plurality of picture elements (dots) IDB, each of which was formed by the ink droplet which landed on, and adhered to, one of the predetermined points on the recording surface of the recording medium. 
     On the other hand,  FIG. 26  shows a portion of an ink jet recording head of the “edge shooter” type, which is disposed in such a manner that its surface having the ejection orifices squarely faces the recording surface of the recording medium. 
     The ink jet recording head unit has a supporting plate  10 , a plurality of head chips  12 A, and a plurality of head chips  12 B. The supporting plate  10  is mounted into the main assembly of a recording apparatus, being accurately positioned therewith. Each of the head chips  12 A and  12 B has a plurality of ink ejection orifices. The head chips  12 A are disposed on one of the larger flat vertical surfaces of the supporting plate  10 , being flush with the top surface of tile supporting plate  10 , and the head chips  12 B are disposed on the other of the larger flat surfaces of the supporting plate  10 , being also flush with the top surface of the supporting plate  10 . More specifically, the plurality of bead chips  12 A are aligned, for example, In the direction perpendicular to the direction, indicated by an arrow mark S, in which the ink jet recording head, which carries out a recording operation, is moved, and so are the plurality of head chips  12 B. The head chips  12 A are disposed with the provision of a predetermined interval between the adjacent two head chips  12 A, and so are the head chips  12 B. The line in which the head chips  12 A are aligned is parallel to the line in which the head chips  12 B are aligned. In terms of the positional relationship between the head chip  12 A and head chip  12 B, the head chips  12 A and head chips  12 B are disposed so that, in terms of the direction perpendicular to the moving direction of the ink jet recording head unit, each head chip  12 B faces the interval between the two head chips  12 B adjacent to this head chip  12 A; in other words, the head chips  12 A and head chips  12 B are disposed in the so-called zigzag pattern. The head chips  12 A and head chips  12 B are relatively precisely positioned with the use of image processing technologies, for example. 
     Since a head chip  12 A and a head chip  12 B are the same in structure, only the head chip  12 A will be described; the head chip  12 B will not be described. 
     For example, each head chip  12 A comprises an ejection element substrate  14 A, a liquid path formation member  16 A, and a top plate  18 A. The top plate  18 A will be described later. The ejection element substrate  14 A has a plurality of electrothermal transducers, which will be described later, and is attached to one of the aforementioned larger vertical flat surfaces of the supporting plate  10 . The liquid path formation member  16 A forms, in cooperation with the top plate  18 A, a plurality of ink paths leading, one for one, to the plurality of the ejection orifices of the recording element substrate  14 , and a common liquid chamber. The top plate  18 A is attached to the top surface of the liquid path formation member  18 A to cover the liquid path formation member  16 A. 
     The recording element substrate  14 A is formed of a plate of silicon (Si), glass, ceramic, aluminum, aluminum alloy, or the like. On the surface of the recording element substrate  14 , there are a plurality of heater layers, as electrothermal transducers, which correspond in position to the plurality of ink paths, one for one, and a plurality of wiring layers. The heater layers and wiring layers are formed in the form of film, in predetermined patterns, with the use of photolithographic technologies. The heater layers, etc., on the recording element substrate  14 A are in electrical connection with the control section, which sends out drive control signals to the heater layers. 
     The liquid path formation member  16 A has a plurality of ejection orifices  16   ai  (i=1−n, n being integer), which are in connection to the ink paths, one for one, and which open at the top surface of the liquid path formation member  16 A, being aligned in the direction roughly perpendicular to the direction indicated by an arrow mark S. The top plate  18 A is in connection to one end of each of the ink supply paths, which is not shown in the drawing. With the provision of the above described setup, the ink supplied through the ink supply path is supplied to the common liquid chamber connected to each of the ink paths. 
     The liquid path formation member  16 A and top plate  18 A placed in layers on the recording element substrate  14 A are made with the use of a photolithographic means, the method for airtightly adhering a molded top plate having nozzles, onto the recording element substrate  1 , or the like, as shown in Japanese Laid-open Patent Application 62-253457. 
     With the provision of the above described structural arrangement, as driving signals are supplied to the heater layers of recording element substrate  14 A, the body of ink surrounding each healer layer, in the corresponding ink path, instantly boils, generating pressure. As a result, liquid droplets are ejected from the ejection orifice  16   ai  in the direction indicated by the arrow-marks in  FIG. 26 , forming image regions GA and GB on the recording surface of recording medium, as shown in FIG.  28 (A). The image region GA in FIG.  28 (A) is formed by the ink droplets ejected from one of the head chip  12 A as this head chip  12 A is moved in the arrow direction S, and the image region GB is formed by the ink droplets ejected from one of the head chips B as this head chip B is moved in the arrow direction S. The image region GA is made up of a plurality of picture elements (dots) IDA, each of which was formed by the ink droplet which landed on, and adhered to, one of the predetermined points on the recording surface of the recording medium, and the image region GB is made up of a plurality of picture elements (dots) IDB, each of which was formed by the ink droplet which landed on, and adhered to, one of the predetermined points on the recording surface of the recording medium. 
     However, when a large number of recording head units of the “side shooter” type, or the “edge shooter” type, are manufactured with one of the above mentioned methods, manufacture errors sometimes occur due to various causes, resulting in the production of such recording head units in which the distance PG between the last (first) ejection orifice of a given head chip  6 A ( 12 A) on one side of the supporting member (plate), and the first (last) ejection orifice of the head chip  6 B ( 12 B) on the other side of the supporting member (plate), in terms of the direction ill which the ejection orifices are aligned, is different from the predetermined distance (pitch) PR, that is, the correct distance. 
     The correct distance (pitch) PR shown In FIG.  24 (A), and the correct distance (pitch) PR shown in FIG.  27 (A), are the same as the distance (pitch) P 1  between the adjacent two ejection orifices of tile head chip  6 A ( 12 A), and the distance (pitch) P 1  between the adjacent two ejection orifices of the head chip  6 B ( 12 B), respectively. Thus, the recording density per unit length in the direction perpendicular to the scanning direction of the recording head unit is determined by the ejection orifice density in the same direction. In other words, it becomes identical to the pitch P 1 . 
     When the PG is different from the correct distance PR, for example, when the distance PG is greater than the correct distance PR (PG&gt;P 1 ) as shown in FIG.  24 (B), a gap, that is, a white streak WL, the width of which is proportional to the difference between the distance PG and correct distance PR, is sometimes formed between the image region GA made up of the set of dots IDA formed by a given head chip  6 A, and the image region GB made up of the set of dots IDB formed by the head chip  6 B adjacent to the given head chip  6 A, as shown in FIG.  25 (B). 
     The above described phenomenon also occurs to a recording head unit of the “edge shooter” type having the head chips  12 A and  12 B. That is, when the aforementioned distance PG is greater than the correct distance PR (PG&gt;P 1 ), as shown in FIG.  27 (B), a gap, that is, a white streak WL, the width of which is proportional to the difference between the distance PG and correct distance PR, is sometimes formed between the image region GA made up of the set or dots IDA formed by a given head chip  12 A, and the image region GB made up of the set of dots IDB formed by the head chip  12 B adjacent to the given head chip  12 A, as shown in FIG.  28 (B). In other words, the ink droplets deviate in terms of landing spot, significantly contributing to the formation of an inferior image. 
     On the other hand, when the distance PS is smaller than (PS&lt;P 1 ) as shown in FIG.  24 (C), the image region GA″ made up of the set of dots IDA formed by a given head chip  6 A, and the image region GB″ made up of the set of dots IDB formed by the head chip  6 B adjacent to the given head chip  6 A, slightly overlap with each other, creating a black streak BL, as shown in FIG.  25 (C). 
     This phenomenon also occurs to a recording head unit of the “edge shooter” type having the head chips  12 A and  12 B, creating the so-called black streak. 
     Obviously, the above described black streak also significantly contributes to the formation of an inferior image. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is a principal object of the present invention to provide a recording head and a recording apparatus, wherein even if there is a deviation between an array of liquid ejection outlets and another array of liquid ejection outlets, the quality of the image provided by the ejection outlets is not deteriorated. 
     According to an aspect of the present invention, there is provided a recording head and a recording apparatus which includes a first ejection outlet array having a plurality of ejection outlets for ejecting liquid; a second ejection outlet array having a plurality of ejection outlets for ejecting liquid, the second ejection outlet array extending along a direction in which the first ejection outlet array extends such that second ejection outlet array is not overlapped with the first ejection outlet array in the direction or a direction perpendicular to the direction, wherein an end portion of the first ejection outlet array is disposed to an end of the second ejection outlet array: and a plurality of supplementing ejection outlets disposed close to at least one of the end portions of the first ejection outlet array and the second ejection outlet array such that supplementing ejection outlets are overlapped with another one of the end portions in the direction in which the first ejection outlet array extends, wherein the supplementing ejection outlets are disposed at an interval which is different from an interval at which the ejection outlets of the first ejection outlet array are disposed. 
     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 perspective view of an example of a recording apparatus equipped with a recording head in accordance with the present invention, for showing the general structure thereof. 
         FIG. 2  is an enlarged plan view of the essential portion of the first embodiment of a recording head in accordance with the present invention. 
         FIG. 3  is a block diagram for showing the control section of the recording head in FIG.  2 . 
         FIG. 4  is a perspective view of the essential portion of the first embodiment of a recording head in accordance with the present invention. 
         FIG. 5  is a plan view of a part of one of the head chips of the recording apparatus in FIG.  1 . 
         FIG. 6  is a sectional view of a part of the portion of the head chip in FIG.  5 . 
         FIG. 7  is a sectional view of another part of the portion of the head chip in FIG.  5 . 
         FIG. 8  is a drawing for describing the operation of the recording apparatus in FIG.  1 . 
         FIG. 9  Is a plan view of the essential portion of the second embodiment of a recording head in accordance with the present invention. 
         FIG. 10  is a sectional view of a part of the portion of the head chip in FIG.  9 . 
         FIG. 11  is a drawing for describing the operation of the recording head in FIG.  9 . 
         FIG. 12  is an enlarged plan view of the essential portion of the third embodiment of a recording head in accordance with the present invention. 
         FIG. 13  is a drawing for describing the operation of the embodiment in FIG.  12 . 
         FIG. 14  is a perspective view of the fourth embodiment of a recording head in accordance width the present invention. 
         FIG. 15  is a perspective view of one of the head chips shown in  FIG. 14 , for showing the structure thereof. 
         FIG. 16  is a plan view of a part of one of the head chips in  FIG. 14 , for showing the structure of the recording element substrate of the head chip. 
         FIG. 17  is a sectional view of a part of the head chip in  FIG. 16 , at the plane XVII—XVII in FIG.  16 . 
         FIG. 18  is a plan view of the essential portion of the head chip shown in  FIG. 14 , as seen from the outward side of the ejection orifices. 
         FIG. 19  is a drawing for describing the operation of the head chip shown in FIG.  18 . 
         FIG. 20  is a plan view of the essential portion of the fifth embodiment of a recording head in accordance with the present invention, as seen from the outward side of the ejection orifices. 
         FIG. 21  is a drawing for describing the operation of the head chip in FIG.  20 . 
         FIG. 22  is a perspective view of another example of a recording apparatus equipped with a recording head in accordance with the present invention, for showing the general structure thereof. 
         FIG. 23  is a perspective view of a part of a typical conventional recording head of the side shooter type, for showing the structure thereof. 
       FIGS.  24 (A),  24 (B), and  24 (C) are enlarged plan views of a part of the head chip in FIG.  23 . 
       FIGS.  25 (A),  25 (B), and  25 (C) are drawings for describing the operations of the head chips in FIGS.  24 (A),  24 (B), and  24 (C), respectively. 
         FIG. 26  is a perspective view of a part of a typical conventional recording head of the edge shooter type, for showing the structure thereof. 
       FIGS.  27 (A) and  27 (B) are enlarged plan views of a part of the head chip in FIG.  26 . 
       FIGS.  28 (A) and  28 (B) are drawings for describing the operations of the head chips in FIGS.  27 (A) and  27 (B), respectively. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows the first embodiment off a recording head in accordance with the present invention, and the general structure of the recording apparatus compatible with each of the embodiments of the present invention, which will be described later. 
     In  FIG. 1 , the recording apparatus essentially comprises: a recording head Unit  50 , which will be described later; a carriage  40  on which a plurality of ink containers  48 Y,  48 M,  48 C, and  48 B are removably mountable; a pair of conveyance roller units  32  and  42 , which intermittently convey a recording paper Pa, as a recording medium, to a location below the recording head unit  50  in the direction indicated by an arrow mark B; and a guide shaft  34 , on which the carriage  40  is set, being enabled to be slidingly guided in the direction roughly perpendicular to the direction of the arrow B. 
     The guide shaft  34  is inserted in the end portion of the base portion of the carriage  40 , supporting the carriage  34  in such a manner that the carriage  40  can be shuttled in the direction indicated by an arrow mark A. The guide shaft  34  is solidly fixed to the housing  30  by its lengthwise ends. The carriage  40  is attached to a timing belt  36  by the back side The timing belt  36  is fitted around a pair of pulleys  38 A and  38 B disposed a predetermined distance from each other. The pulley  38 B is simply supported by the housing  30 , being enable to freely rotate, whereas the pulley  38 A is rotationally supported by the housing  30 , and is connected to the output shaft of a driving motor  51 . Thus, as the motor  51  is rotated forward or in reverse, the carriage  40  is moved forward or backward a predetermined distance by the timing belt  36 . 
     The ink containers  48 Y,  48 M,  48 C, and  48 B are assumed to contain yellow, magenta, cyan, and black inks, respectively, by predetermined amounts. The internal pressure of each of the ink containers  48 Y,  48 M,  48 C, and  48 B is kept at a predetermined negative level. 
     The conveyance rollers  32  and  42  are attached to the housing  30 , being thereby rotationally supported, by their lengthwise ends. The conveyance roller unit  32  is disposed on the upstream side of the conveyance roller unit  42 , with the presence of a predetermined distance between two roller units  32  and  42 , in terms of the direction in which the paper Pa is conveyed. To one end of each of the conveyance roller units  32  and  42 , a conveyance roller unit driving portion  46 , inclusive of a motor for driving the conveyance roller units  32  and  42 , is connected. Thus, as the driving portion  46  is driven, the recording paper Pa is intermittently conveyed in the arrow B direction while remaining nipped by the conveyance roller units  32  and  42 . Thus, while the recording paper Pa is conveyed in the above described manner, it is kept under a predetermined amount of tension, assuring that it is kept flat, across the area facing the recording head, as will be described later. 
     At one end of the internal space of the housing  30 , the home position is located, at which the carriage  40  bearing the plurality of ink containers  48 Y- 48 B is temporarily stopped, or is kept on standby, as necessary, with a predetermined timing, for example, at the beginning of a recording operation, or during a recording operation, and also, at which a capping member  44  for carrying out a recovery process for the recording head is located. To the capping member  44 , a suction type recovery means is connected, which is for preventing the ejection orifices of the recording head unit from becoming plugged, by forcefully suctioning ink from the ejection orifices. 
     Each ink container is provided with its own recording head unit  50  shown in  FIG. 4 , and is mounted on the carriage  40  in such a manner that the ejection orifices of its recording head unit  50  squarely face the recording surface of the recording paper Pa located below the carriage  40 . 
     The recording head unit  50  has a holder  56 , a set of head chips  52 A, a set of head chips  52 B, a set of wiring substrate  54 A, and a set of wiring substrates  54 B. The holder  56  is precisely positioned by being engaged with a predetermined portion of the carriage  40 . The set of head chips  52 A is disposed along one edge of the top surface of the holder  56 , and the set of head chips  52 B is disposed along the other edge. The two sets of wiring substrates  54 A and  54 B are electrically connected to the set of head chips  52 A and set of head chips  52 B, respectively. 
     The head chips  52 A are arranged in a straight line roughly perpendicular to the moving direction of the carriage  40 , that is, the direction indicated by an arrow mark A, with the provision of a predetermined interval between adjacent two head chips  52 A, arid so are the head chips  52 A, with provision of the predetermined interval between the adjacent two head chips  52 B. Further, the set or head chips  52 A and set of head chips  52 B are attached to the top surface of the holder  56 , being disposed relative to each other in such a manner that the mid point of the interval between given two adjacent head chips  52 A aligns with the center of the head chip  52 B on the other side of the holder  56 ; in other words, the two sets of head chips  52 A and  52 B are disposed so that the head chips  52 A and head chips  52 B are disposed in the so-called zigzag fashion. Further, the two sets of head chips  52 A and  52 B are positioned with the use of a predetermined jig, with a positional tolerance of approximately ±0.1 mm. 
     Referring to  FIGS. 5 and 7 , each head chip  52 A essentially comprises an ejection element substrate  58 , and a grooved plate  64 . The ejection element substrate  58  has a plurality of electrothermal transducers  58   ai  (i=1−n, n being integer), as heaters, that is, ejection energy generating portions, arranged across one of its surface, with the presence of predetermined intervals the grooved plate  64  is attached to the ejection element substrate  58  so that the heaters  59   ai , are aligned one for one with the plurality of the grooves of the top plate  64 , forming thereby a plurality of liquid paths  60   ai , and a common liquid chamber  62  connected to each of the liquid paths  60   ai.    
     The flat top surface of the holder  56  is provided with a plurality of recesses  56   a , each of which is predetermined in position and depth, and to the bottom surface of each of which one ejection element substrate  58  is attached. Further, at the bottom surface of each recess  56   a , there is the opening of one end of an ink supply path  62 . The other end of the Ink supply path  62  leads into the corresponding ink container. The ejection element substrate  58  has a liquid path  58   b , which coincides in location with the end of the ink supply path  62 . 
     Referring to  FIG. 6 , the grooved plate  64 , which is attached to the top surface of the ejection element substrate  58 , is provided with the common ink chamber  62 , which is on the inward side of the grooved plate  64 . The common ink chamber  62  is connected to all of the ink paths  64   bi , in which the plurality of heaters  58   ai  are disposed one for one. Referring to  FIGS. 2 and 5 , the grooved plate  64  is also provided with a plurality of ejection orifices  52   ai  (i=1−n, n being integer), which correspond one for one with the plurality of heaters  58   ai , being disposed in the zigzag fashion, with the provision of a predetermined pitch. 
     The holder  56  is provided with plural wiring substrates  54 A, each of which is disposed in a manner to surround the corresponding grooved plate  64 . Each of wiring substrate  54 A is formed with the use of ILB (Inner Lead Bonding), or the like method, being in electrical connection with the terminal of the corresponding heater  58   ai , through the terminal of its lead. In other words, the grooved plate  64  is placed in the opening  54   h  of the corresponding wiring substrate  54 A. The junction between the terminal of each heater and the terminal  54   a  of the lead wire  54   a  of the corresponding wiring substrate  54 A is covered with a body of sealing resin  68  coated in a manner to cover the edge of the wiring substrate  54 A and the edge of the grooved plate  64 , as well as the junction. Thus, plural bodies of sealing resin  68  are aligned in the same direction as the direction in which the head chips  52 A are aligned. Further, there is a gap SP between the edge of the head chip  52 A, perpendicular to the head chip alignment direction, and the edge of the opening  54   h , perpendicular to the head chip alignment direction. 
     On the other hand, each head chip  52 B is, provided with a plurality of compensatory ejection orifices  52   bm , which are aligned at one, both ends, of one, or both lines, of the ejection orifices  52   bi , in a manner to extend the line, or lines, of the ejection orifices  52   bi , as shown in FIG.  2 . For example, there are three compensatory ejection orifices  52   bm  per line of the ejection orifices  52 B, or the normal ejection orifices. In other words, there are compensatory ejection orifices  52   bm   1 ,  52   bm   2 ,  52   bm    3 ,  52   bm   4 ,  52   bm   5 , and  52   bm   6 , which are arranged in the zigzag fashion, with the provision of predetermined intervals. The compensatory ejection orifices  52   bm   1 ,  52   bm   2 , and  52   bm   3  are aligned in a manner to extend one of the lines of the normal ejection orifices  52   bi , and the compensatory ejection orifices  52   bm   4 ,  52   bm    5 , and  52   bm    6  are arranged in a manner to extend the other line of the normal ejection orifices  52 B. In terms of the ejection orifice alignment direction, the distance PD between the compensatory ejection orifices  52   bm   3  and  52   bm   4  is set to be approximately half the distance PE between the two adjacent normal ejection orifices  52   bi  in the same line. The compensatory ejection orifices  52   bm   1 - 52   bm   6  are made smaller in diameter than the normal ejection orifices  52   bi , in proportion to the distance PD. 
     Further, the ejection element substrate  58  is provided with additional heaters  58   ai , which are disposed in a manner to correspond in position to the compensatory ejection orifices  52   bm   1 - 52   bm   6 , and the groove plate  56  is provided with additional ink paths  64   bi , which correspond in position to the compensatory ejection orifices  52   bm   1 - 52   bm   6 , being arranged at a predetermined pitch. 
     The distance PE between two adjacent ejection orifices of the head chip  52 A is the same as that of tile head chip  52 B. 
     In terms of structure, the head chip  25 B is different from the head chip  52 A only in the portion of the grooved plate  64  corresponding to the compensatory ejection orifices  52   bm  and the portion of the ejection orifice substrate  58  corresponding to the compensatory ejection orifices  52   bm . In other words, except for the portion other than the portion of the grooved plate  64  corresponding to the compensatory ejection orifices  52   bm  and the portion of the ejection element substrate corresponding to the compensatory ejection orifices  52   bm , the head chip  52 B is the same in structure as the head chip  52 A. 
     Referring to  FIG. 3 , an example of a recording apparatus in accordance with the present invention has a control section. 
     The control section essentially comprises: a central processing unit (which hereinafter will be referred to as CPU)  74 , which will be described later; an input/output interface  72 ; a read-only memory (which hereinafter will be referred to as ROM)  78 ; and a random access memory (which hereinafter will be referred to as RAM)  80 . The CPU  74  controls the recording operation of the recording head unit  60 , the operation of the carriage  40 , and the operation of the driving portion  46 . The input/output interface  72  inputs into the CPU  74 , the recording operation data DG made up of the image formation data from a host computer  70  and the control data, and the compensatory operation data DS, which will be described later, and outputs to the host computer  70 , the data from the CPU  74 , which shows the state of the recording operation. The ROM  78  stores the control programs, and the RAM  80  stores the image formation data from the host computer  70 , control data, compensatory operation data DS, address data for each of the compensatory ejection orifices of the recording head unit  50 , and the like data. 
     The compensatory data DS are created by the host computer  70  based on the deviation in the positional relationship between a given head chip  52 A and the head chip  52 B adjacent to the given head chip  52 A. More specifically, the actual distance between the given head chip  52 A and the head chip  52 B adjacent thereto is measured with the use of a microscope or the like. Referring to  FIG. 2 , when the extension of a referential line JL tangential to the endmost ejection orifice of the head chip  52 A is tangential to the compensatory ejection orifice  52   bm   6  of the head chip  52 B, the compensatory data DS are created so that the compensatory ejection orifices  52   bm   1  and  52   bm   6 , in addition to the normal ejection orifices  52   bi , are used during image forming operation, in order to ensure that a gap greater than a predetermined value is not created between the rightmost ejection orifice of the head chip  52 A and the leftmost ejection orifice of the head chip  52 B in terms of the ejection orifice alignment direction. On the other hand, if the extension JL, represented by the two-dot chain line, of the referential line JL is tangential to the compensatory ejection orifice  52   bm   5 , the compensatory data DS are created so that the compensatory ejection orifices  52   bm   1 ,  52   bm   2 ,  52   bm   5 , and  52   bm   6  are used. 
     The number of the compensatory ejection orifices to be enabled to be activated may be increased or decreased based on the quality of the images created by the actual recording operations involving the head chips  52 A and head chips  52 B. This also applies to the following embodiments. 
     Thus, the compensatory data DS, inclusive of the identities of the compensatory ejection orifices enabled to the activated based on the results of the above described observations, are inputted into the host computer  70 , and then, are sent to the input/output interface  72  through the bidirectional transmission path. 
     The CPU  74  creates the control data for making the carriage  40  shuttle a predetermined distance based on the recording operation data DGM, and also, for intermittently conveying the recording paper Pa in synchronism with the recording operation. Then, it supplies the control data to the motor driver  82 . 
     The motor driver  82  creates drive control signals based on the data from the CPU  74 , and supplies the driving control signals to the driving motor  51  and conveyance roller unit driving portion  46 . 
     Further, the CPU  74  carries out a predetermined image conversion process, based on the recording operation data DGM read from the RAM  80 , creating a set of data corresponding to the head chips  52 A and head chips  52 B of the recording head unit  50 , and supplies these data correspondent to the head chips  52 A and head chips  52 B, to the head driver  76 . 
     While carrying out the predetermined image conversion process, the CPU  74  also uses the compensatory data DSM read from the RAM  80 , and the image formation data, to create a set of data for making the chosen compensatory ejection orifices carry out recording operations, and supplies the created data to the head driver  76 . Based on these sets of data supplied from the CPU  74 , the head driver  76  creates a plurality of sets of drive control pulse signals, and supplies them to the recording head unit  50 . 
     Thus, as the recording head unit  50  is driven with the controlled timing, an image is formed on the recording surface of the recording paper Pa as shown in  FIG. 8 , for example. 
       FIG. 8  represents a part of the image region formed by a single head chip  52 A as the head chip  52 A was moved in the arrow A direction, add a part of the image region formed by a single head chip  52 B as the head chip  52 B was moved also in the arrow A direction. 
     The region GGA is made up of a set of dots IDA formed by the ink droplets ejected from the ejection orifices  52   ai  of the head chip  52 A as they adhered to the recording surface of the recording paper Pa, and the region GGB is made up of a set of dots IDB formed by the ink droplets ejected from the ejection orifices  52   bi  of the head chip  52 B as they adhered to the recording surface of the recording paper Pa. The region GGC is made up of a set of dots IDC formed by the ink droplets ejected from the compensatory ejection orifices  52   bm   6  and  52   bm   1  of the head chip  52 B. The dot IDA, dot IDB, and dot IDC each is a picture element formed by a single ejection. 
     Therefore, it is possible to obtain an image which does not have the so-called white or black streak traceable to the deviation of the positional relationship between the head chip  52 A and head chip  52 B, across the area correspondent to the interval between the head chip  52 A and head chip  52 B, in terms of the head chip alignment direction, or across the area corresponding to the portions of the recording head unit where the head chip  52 A and head chip  52 B partially overlap with each other, in terms of the direction perpendicular to the head chip alignment direction. 
     However, in the case of this embodiment, the compensatory ejection orifices  52   mb  are made greater in dot density, and therefor, are made smaller in ink droplet volume, compared to the normal ejection orifices  52   bi . The volume by which ink is ejected by each compensatory ejection orifice  52   mb  may be the same as the volume by which ink is ejected by each normal ejection orifice  52   bi . It is obvious, however, that when each compensatory ejection orifice is smaller in ink ejection volume, by an amount proportional to recording density, than each normal ejection orifice, the amount of the image defects traceable to the deviation of the positional relationship between the head chip  52 A and head chip  52 B will be smaller than otherwise. 
     This embodiment of a recording head in accordance with the present invention is an example of a recording head having a plurality of head chips which are arranged in two straight lines so that the head chips in one line are offset relative to the head chips in the other lines; in other words, they are arrange in the zigzag fashion. It is characterized in that one end, or both ends, of each head chip, in terms of the alignment direction, in one line is provided with a plurality of compensatory ejection orifices which are aligned in such a manner that they extend the line formed by its normal ejection orifices, and also that the portion of the head chip, which has the compensatory ejection orifices, overlaps with the portion of the corresponding head chip in the other line, which has the last (or first normal ejection orifice. According to another characteristic aspect of this embodiment, the compensatory ejection orifices are disposed in a manner to increase the recording density of the recording head across the portion corresponding to the border portion between two adjacent head chips in terms of the head chip alignment direction. Thus, the size and intensity of the streaks formed by a recording head unit can be reduced by selecting, in number and configuration, the compensatory ejection orifices, according to the accuracy in the positional relationship between a given head chip in one line of the head chips and the corresponding head chip in the other line. 
     (Embodiment 2) 
       FIG. 9  shows the essential portion of the second embodiment of a recording head in accordance with the present invention. 
     Also in the case of the embodiment shown in  FIG. 9 , a set of head chips  92 A and a set of head chips  92 B are arranged in a manner similar to the above described first embodiment. That is, a plurality of head chips  92 A are arranged in a manner to form a straight line roughly perpendicular to the moving direction of the carriage  40 , that is, the direction indicated by an arrow mark A, along one edge of one of the flat surfaces of a holder, whereas a plurality of head chips  92 B are arranged in a manner to form a straight line roughly parallel to the line formed by the plurality of head chips  92 A, along the other edge of the same flat surface of the holder. Further, the set of head chips  92 A and set of head chips  92 B are attached, along with the set of wiring substrates  90 A and set of wiring substrate  90 B electrically connected thereto, one for one, to the flat surface of the supporting member in the zigzag fashion, with the provision of a predetermined interval, between two adjacent head chips. Further, the two sets of head chips  92 A and  92 B are positioned with the use of a predetermined jig, with a positional tolerance of approximately ±0.1 mm 
     Each head chip  92 A has the same internal structure as the head chip  52 A in the above described embodiment. It has a plurality of ejection orifices  92   ai  (i=n, n being integer), which are open at the ejection surface of the head chip  92 A, being arranged in two roughly parallel two straight lines, with the provision of a predetermined interval PE in the line direction. In terms of the arrow A direction, the ejection orifices in one line are offset from the corresponding ejection orifices in the other line: in other words, the ejection orifices  92   ai  of the head chip  92 A are arranged in the zigzag fashion. 
     Except for one, or both, of the lengthwise end portions, each head chip  92 B is the same in structure as each head chip  92 A. That is, it has a plurality of ejection orifices  92   bi  (i=n, n being integer), which are open at the ejection surface of the head chip  92 B, being arranged in two roughly parallel straight lines, with the provision of a predetermined interval PE in the line direction. In terms of the arrow A direction, the ejection orifices in one line are offset from the corresponding ejection orifices in the other line; in other words, the ejection orifices  92   bi  of the head chip  92 B are arranged in the zigzag fashion. However, one, or both, of the lengthwise ends of each head chip  92 A are provided with a plurality of compensatory ejection orifices  92   bm  aligned in a predetermined direction. These compensatory ejection orifices, for example,  92   bm   1 ,  92   bm   2 ,  92   bm   3 , and  92   bm   4  are positioned across the portion of each head chip  92 B, which corresponds to the portion of the corresponding head chip  92 A, across which the first and second ejection orifices, counting from the lengthwise end of the head chip  92 A, are positioned. 
     More specifically, the compensatory ejection orifices  92   bm   1 ,  92   bm   2 ,  92   bm   3 , and  92   bm   4  are aligned roughly in parallel to the line connecting the centers of the first and second normal ejection orifices  92   bi , counting from the lengthwise end of the head chip  92 B; in other words, they are diagonally aligned. Referring to  FIG. 9 , in terms of the lengthwise direction of the head chips  92 B, the distance PF between the two vertical lines which coincide, one for one, with the centers of the two adjacent compensatory ejection orifices among  92   bm   1 - 92   bm   4 , is approximately half the distance PE between the two vertical lines which coincide, one for one, with the center of a given normal ejection orifice  92   ai  and the ejection orifice  92   bi  adjacent thereto. Further, in terms of diameter, the compensatory ejection orifices  92   bm   1 - 92   bm   4  are the same as the normal ejection orifice  92   ai  and normal ejection orifice  92   bi.    
     Referring to  FIG. 10 , the grooved plate  94  of each head chip  92 B has a plurality of ink paths  94   bi  which correspond one for one to the plurality of ejection orifices  92   bi . The grooved plate  94  of each head chip  92 B also has a common ink supply path  94   d , which runs through the center of the grooved plate  94 , being connected to all of the ink paths  94   bi . The common ink supply path  94   d  is closed at both ends. Further, the grooved plate  94  of each head chip  92 B has a plurality of ink paths  94   fi  leading one for one to the aligned compensatory ejection orifices  92   bm . Each ink path  94   fi  is connected to a common ink supply path  94   e.    
     The FI ejection element substrate of each head chip  92 B has a plurality of heaters corresponding one for one to the plurality of ink paths  94   bi  and plurality of ink paths  94   fi.    
     When a recording operation is carried out by a recording head unit comprising the set of head chips  92 A and set of head chips  92 B structured as described above, the host computer  70  creates the compensatory data DS, based on the deviation in the positional relationship between a given head chip  92 A and the head chip  92 B adjacent thereto. More specifically, the actual distance between the given head chip  92 A and the head chip  92 B adjacent thereto is measured with the use of a microscope or the like. Referring to  FIG. 9 , when the extension of a referential line JL tangential to the endmost ejection orifice of the head chip  92 A is also tangential to the compensatory ejection orifice  92   bm   3  of the head chip  92 B, the compensatory data DS are created so that the compensatory ejection orifice  92   bm   3  are activated, in addition to the normal ejection orifices  92   bi , in order to ensure that a gap greater than a predetermined value is not created between the rightmost ejection orifice of the head chip  92 A and the leftmost ejection orifice of the head chip  92 B, in terms of the ejection orifice alignment directions in FIG.  9 . On the other hand, if the extension JL′, represented by the two-dot chain line, of the referential line JL is tangential to the compensatory ejection orifice  92   bm   4 , the compensatory data DL are created so that the compensatory ejection orifices  92   bm   3  and  92   bm   4  are activated. 
     The CPU  74  supplies to the head driver  76 , the data obtained by carrying out the above described processes. 
     While carrying out the above described processes, the CPU  74  also uses the compensatory data DSM read from the Ram  80 , and the image formation data, to create a set of data for making the chosen compensatory ejection orifices carry out recording operations, and supplies tile created data to the head driver  76 . 
     Based on these sets of data supplied from the CPU  74 , the head driver  76  creates a plurality of sets of drive control pulse signals, and supplies them to the recording head unit. 
     Thus, as the recording head unit is driven is with the controlled timing, an image is formed on the recording surface of the recording paper Pa as shown in  FIG. 11 , for example. 
       FIG. 11  represents a part of the image region formed by a single head chip  92 A as the head chip  92 A was moved in the arrow A direction, and a part of the image region formed by a single head chip  92 B as the head chip  92 B was moved also in the arrow A direction. 
     The region GGE is made up of a set of dots IDA formed as the ink droplets ejected from the head chip  92 A adhered to the recording surface of the recording paper Pa, and the region GGD is made up of a set of dots IDB formed by the ink droplets ejected from the head chip  92 B as they adhered to the recording surface of the recording paper Pa. The region GGF is made up of a set of dots IDF formed by the ink droplets ejected from the compensatory ejection orifices  92   bm   3  of the head chip  92 B as they adhered to the recording surface of the recording paper Pa. 
     Therefore, it is possible to obtain an image which does not have the so-called white or black streak traceable to the deviation of the positional relationship between the head chip  92 A and head chip  92 B, across the area correspondent to the interval between the head chip  92 A and head chip  92 B, or the overlapping portions of the head chip  92 A and head chip  92 B, respectively. 
     Also in the case of this embodiment, the head design may be such that the compensatory ejection orifices  92   mb  are the same as or different from, the normal ejection orifices, in terms of ink droplet volume. 
     (Embodiment 3) 
       FIG. 12  shows the essential portion of the third embodiment of a recording head in accordance with the present invention. 
     The embodiment in  FIG. 12  is provided with a plurality of head chips  102 A arranged in a manner to form a straight line roughly perpendicular to the moving direction of the carriage  40 , that is, the direction indicated by an arrow mark A, with the provision of a predetermined interval between the two adjacent head chips, and a plurality of head chips  102 B arranged in the same manner as the plurality of head chips  102 A. The line formed by the head chips  102 A and the line formed by the head chips  102 B are roughly parallel to each other. Further, the set of head chips  102 A and set of head chips  102 B are attached, along with the set of wiring substrates  100 A and set of wiring substrate  100 B electrically connected thereto, one for one, to the flat surface of the supporting member in the zigzag fashion, with the provision of a predetermined interval between two adjacent head chips. The head chips  102 A and head chips  102 B are positioned with the use of a predetermined jig, with a tolerance of approximately ±0.1 mm. 
     Each head chip  102 A has the same internal structure as the above described head chip  52 A. It has a plurality of ejection orifices  102   ai  (i=n, n being integer), which are open at the ejection surface of the head chip  102 A, being arranged in the zigzag fashion, with the provision of a predetermined interval PE between the two adjacent ejection orifices, in terms of the line direction. The internal structure of each head chip  102 B is similar to that of each head chip  102 A. 
     More specifically, except for one, or both, of the lengthwise end portions, each head chip  102 B is the same in structure as each head chip  102 A. That is, it has a plurality of ejection orifices  102   bi  (i=n, n being integer), which are open at the ejection surface of the head chip  102 B, being arranged in the zigzag fashion, with the provision of a predetermined interval PE, in terms of the lengthwise direction of the head chip  102 B. However, one, or both, of the lengthwise ends of each head chip  102 B are provided with a plurality of compensatory ejection orifices  102   bm.    
     More specifically, referring to  FIG. 12 , the plurality of compensatory ejection orifices  102   bm  are located so that, in terms of the moving direction of the carriage, the portion of the head chip  102 B, across which the compensatory ejection orifices  102   bm   1  are located, overlaps with the portion of the head chip  102 A, across which the first to eighth ejection orifices  102   ai , counting from the right edge of the head chip  102 A, are located. That is, the compensatory ejection orifices  102   bm  are arranged in a manner to form two extensions of the two straight lines, one for one, formed by the normal ejection orifices  102   bi  in the lengthwise direction of the head chip  102 B; for example; the compensatory ejection orifices  102   bm   1 ,  102   bm   2 ,  102   bm   3 ,  102   bm   4 ,  102   bm   5 ,  102   bm   6 , and  102   bm   7  form the above described one extension, and the compensatory ejection orifices  102   bm   8 ,  102   bm   9 ,  102   bm   10 ,  102   bm   11 ,  102   bm   12 , and  102   bm   13  form the other extension. Further, in terms of the lengthwise direction of the head chip  102 B, the compensatory ejection orifices  102   bm  in the above described one extension are offset from the corresponding compensatory ejection orifices  102   bm  in the other extension; in other words, in terms of the lengthwise direction of the head chip  102 B, the compensatory ejection orifices  102   bm   1 - 102   bm   13  are arranged in the zigzag fashion. Also referring to  FIG. 12 , the compensatory ejection orifice  102   bm   1  is positioned so that the vertical line CL tangential to the right side of the compensatory ejection orifice  102   bm   1  is also tangential to the left side of the first normal ejection orifice  102   bi , counting from the left end of the head chip  102 B, positioned diagonally above the compensatory ejection orifice  102   bm   1  in the drawing. 
     The distance PG between the centers of the two numerically consecutive compensatory ejection orifices among  102   mb   1 - 102   mb   13 , is set to a smaller value compared to the distance PE between the centers of the two numerically adjacent normal ejection orifices  102   bi . Further, the compensatory ejection orifices  102   bm   1 - 102   bm   13  are made smaller in diameter than the normal ejection orifices  102   bi.    
     The unshown groove plate of each head chip  102 B has a plurality of ink paths which correspond one for one to the aligned compensatory ejection orifices  102   bm   1 - 102   bm   13 . Further, the unshown ejection element substrate of each head chip  102 B has a plurality of heaters corresponding one for one to the plurality of compensatory ejection orifices aligned compensatory ejection orifices  102   bm   1 - 102   bm   13 . 
     When a recording operation is carried out by a recording head unit comprising the set of head chips  102 A and set of head chips  102 B structured as described above, the host computer  70  creates the compensatory data DS, based on the deviation in the positional relationship between a given head chip  102 A and the head chip  102 B adjacent thereto. More specifically, for example, when a referential line JL tangential to one of the normal ejection orifices  102   ai . located on one of the lengthwise end portions of the head chip  102 A is also tangential to the compensatory ejection orifices  102   bm   5  and  102   bm   10  of the head chip  102 B, the compensatory data DS are created so that the compensatory ejection orifices  102   bm   1 - 102   bm   4 , and  102   bm   10 - 102   bm   13 , which are located between the normal ejection orifices of the head chip  102 A, in contact with the referential line JL in  FIG. 12 , and the leftmost normal ejection orifice  102   bi  of the head chip  102 B, in terms of the lengthwise direction of a head chip, are enabled to be used for compensation during a recording operation. In this case, the ejection orifices  102   ai  of the head chip  102 A, on the left side of the referential line JL, are not used. 
     On the other hand, if the extension JL′, of the referential line JL is tangential to the compensatory ejection orifice  102   bm   7 , as represented by the two-dot chain line, the compensatory ejection orifices  102   bm   1 - 102   bm   13  are used in entirety. 
     The CPU  74  supplies to the head driver  76 , the data obtained by carrying out the above described processes. 
     While carrying out the above described processes, the CPU  74  also uses the compensatory data DSM read from the RAM  80 , and the image formation data, to create a set of data for making the chosen compensatory ejection orifices carry out recording operations, and supplies the created data to the head driver  76 . Based on these sets of data supplied from the CPU  74 , the head driver  76  creates a plurality of sets of drive control pulse signals, and supplies them to the recording head unit. 
     Thus, as the recording head unit is driven with the controlled timing, an image is formed on the recording surface of the recording paper Pa as shown in  FIG. 13 , for example. 
       FIG. 13  represents a part of the image region formed by a single head chip  102 A as the head chip  102 A was moved in the arrow A direction, and a part of the image region formed by a single head chip  102 B as the head chip  102 B was moved also in the arrow A direction. 
     The region GGI is made up of a set of dots IDA formed by the ink droplets ejected from the head chip  102 A as they adhered to the recording surface of the recording paper Pa, and the region GGH is made up of a set of dots IDB formed by the ink droplets ejected from the head chip  102 B as they adhered to the recording surface of the recording paper Pa. The region GGJ is made up of a set of dots IDJ formed by the ink droplets ejected from the compensatory ejection orifices  102   bm   1 - 102   bm   4 , and  102   bm   10 - 102   bm   13 , of the head chip  102 B as they adhered to the recording surface of the recording paper Pa. 
     Therefore, it is possible to obtain an image which does not have the so-called white or black streak traceable to the deviation of the positional relationship between the head chip  102 A and head chip  102 B, across the area correspondent to the range in which the head chip  102 A and head chip  102 B partially overlap with each other in terms of the moving direction of the carriage, that is, the arrow A direction. 
     Also in the case of this embodiment, the head design may be such that the compensatory ejection orifices  102   mb  are the same as, or different from, the normal ejection orifices, in terms of ink droplet volume. 
     (Embodiment 4) 
       FIG. 14  shows the essential portion of the third embodiment of a recording head in accordance with the present invention. 
     The embodiment in  FIG. 14  has a supporting plate  110 , a set of head chips  112 A arrange on one of the two largest vertical flat surfaces of the supporting plate  110 , and a set of head chips  112 B arranged on the other of the two largest vertical flat surface of the supporting plate  110 . Each of the head chips  112 A and  112 B has a plurality of ink ejection orifices The head chips  112 A are arranged in a straight line roughly perpendicular to the moving direction of the carriage  40 , that is, the direction indicated by an arrow mark A, with the provision of a predetermined interval between adjacent two head chips  112 A, and so are the head chips  112 A, with the provision of the predetermined interval between the adjacent two head chips  112 B. Thus, the lines which the set of head chips  112 A form and the which the set of head chips  112 B form are roughly parallel to each other. In terms of the ordinal number, inclusive of both sets of the head chips, determined based on the distance from one of the lengthwise ends of the supporting plate  110 , the head chips are arranged in the zigzag fashion, with the provision of a predetermined interval between a given head chip  112 A and the head chip  112 B adjacent thereto. Further, the two sets of head chips  112 A and  112 B are positioned with the use of a predetermined jig, with a tolerance of approximately ±0.1 mm, for example. 
     Referring to  FIGS. 15 and 17 , each head chip  112 A comprises an ejection element substrate  114 A, a liquid path formation member  116 A, and a top plate  118 A. The ejection element substrate  114 A has a plurality of electrothermal transducers, which will be described later, and is attached to one of the aforementioned two larger vertical flat surfaces of the supporting plate  110 . The liquid path formation member  116 A forms, in cooperation with the top plate  118 A, a plurality of ink paths leading, one for one, to the plurality of the ejection orifices of the recording element substrate  114 A, and a common liquid chamber  116 R. The top plate  118 A is attached to the top surface of the liquid path formation member  116 A to cover the liquid path formation member  116 A. 
     The recording element substrate  114 A is formed of a plate of silicon (Si), glass, ceramic, aluminum, aluminum alloy, or the like. Referring to  FIG. 16 , on the surface of the recording element substrate  114 A, there are a heater layers  114 H, as electrothermal transducers, which correspond in position to the plurality of ink paths, one for one, wiring layers  114 EI connected to the plurality of the heater layers  114 H, one for one, and a wiring layers  114 EC comprising the common electrode. The healer layers and wiring layers are formed in the form of film, in predetermined patterns, with the use of photolithographic technologies. The heater layers, etc., on the recording element substrate  114 A are in electrical connection with the control section, through a common electrode pad  114 PC, and an individual electrode pad  114 PI. The control section sends out drive control signals to the heater layers. Referring to  FIG. 17 , each healer layer  114 H is covered with a protective layer PL and an anti-cavitation layer CL, whereas each individual wiring layer  114 EI and each common electrode layer  114 EC are covered with a protective layer PL and an insulating layer SL. 
     The liquid path formation member  116 A and top plate  118 A placed in layers on the recording element substrate  114 A are made with the use of a photolithographic means, the method for airtightly adhering a molded top plate having nozzles, onto the recording element substrate  114 A, or the like. 
     Referring to  FIG. 15 , the liquid path formation member  116 A has a plurality of ejection orifices  116   ai  (i=1−n, n being integer), which are in connection to the ink-paths  116   bi  (i=n, n being integer), one for one, and which are aligned in the direction roughly perpendicular to the moving direction of the recording bead unit indicated by an arrow mark A. The top plate  118 A is in connection to one end of the unshown ink supply path. With the provision of the above described setup, the ink within an ink container is supplied to the common liquid chamber  116 R through the ink supply path. 
     Referring to  FIG. 18 , on the other hand, the liquid path formation member  116 B of each head chip  112 B is provided with a plurality of ejection orifices  116   di  (i=1−n, n being integer) arranged, approximately at the middle in terms of the widthwise direction of the liquid formation member  116 B, in a straight line in the lengthwise direction of the liquid formation member  116 B, with the provision of a predetermined interval PPE between the centers of the adjacent two ejection orifices  116   bi , as is the liquid path formation member  116 A of each head chip  112 A. Thus, the liquid path formation member  116 B contains the plurality of ink paths leading one for one to the plurality of ejection orifices  116   bi , and a common liquid chamber. Further, the recording element substrate  114 B is provided with a plurality of heater layers correspondent one for one to the plurality of ink paths, a plurality of the aforementioned individual electrode layers, and a plurality of the aforementioned common electrode layers, etc., which are on the surface of the recording element substrate  114 B. 
     Further, each head chip  112 B is provided with a plurality of compensatory ejection orifices  116   bm , which are located across one, or both, end portions of the head chip  112 B in terms of the direction in which is the normal ejection orifices  116   a   1  are aligned. More specifically, referring to  FIG. 18 , the plurality of compensatory ejection orifices  116   bm , for example, the compensatory ejection orifices  116   bm   1 ,  116   bm   2 ,  116   bm   3 ,  116   bm   4 ,  116   bm   5 , and  116   bm   6 , are aligned across the portion of the head chip  112 B, which overlaps, in terms of the moving direction of the recording head, with the portion of the head chip  112 A between the lengthwise edge and where the second ejection orifice, counting from the same lengthwise edge, of the head chip is. Further, the recording element substrate  114 B is provided with a plurality of heater layers, similar to the heater layers for the normal ejection orifices  116   bi , being positioned corresponding to the plurality of ink paths leading one for one to the compensatory ejection orifices  116   bm   1 - 116   bm   6 . 
     Referring to  FIG. 18 , the compensatory ejection orifice  116   bm   1  is positioned so that there is a distance of PPH between its center and the center of the leftmost normal ejection orifice  116   bi , and also so that the distance PPI between the centers of the adjacent two compensatory ejection orifices  116   bm  in terms of the their alignment direction is approximately half the interval PPE between the center of the adjacent two normal ejection orifices  116   ai  or  116   bi . Further, the compensatory ejection orifices  116   bm   1 - 116   bm   6  are made smaller in diameter than the normal ejection orifices  116   bi.    
     When a recording operation is carried out by a recording head unit comprising the set of head chips  112 A and set of head chips  112 B structured as described above, the host computer  70  creates the compensatory data DS, based on the deviation in the positional relationship between a given head chip  112 A and the head chip  112 B adjacent thereto, as in the above described preceding embodiments. More specifically, each recording head unit is measured with the use of a microscope or the like. Then, for example, when the extension of a referential line JL tangential to one of the normal ejection orifices  116   ai  located oil one of the lengthwise end portions of the head chip  112 A is also tangential to, for example, the compensatory ejection orifices  116   bm   3 , the compensatory data DS are created so that the compensatory ejection orifices  116   bm   1  and  116   bm   2  are used during a recording operation, in order to prevent the phenomenon that a gap wider than a predetermined value, in terms of the alignment direction of the ejection orifices  116   ai  or orifices  116   bi , occurs between the ejection orifice of the head chip  112 A in contact with the referential line JL, in  FIG. 18 , and the leftmost normal ejection orifice  116   bi  of the head chip  112 B. 
     On the other hand, if the extension JL′, of the referential line JL is tangential to, for example, the compensatory ejection orifice  116   bm   4 , as represented by the two-dot chain line, the compensatory ejection orifices  116   bm   1 - 116   bm   4  are used. 
     The CPU  74  supplies to the head driver  76 , the data obtained by carrying out the above described processes. 
     While carrying out the above described processes, the CPU  74  also uses the compensatory data DSM, based on the compensatory ejection orifices selected as described above, and read from the RAM  80 , and the image formation data, to create a set of data for making the selected compensatory ejection orifices carry out recording operations, and supplies the created data to the head driver  76 . Based on these sets of data supplied from the CPU  74 , the head driver  76  creates a plurality of sets of drive control pulse signals, and supplies them to the recording head unit. 
     Thus, as the recording head unit is driven with the controlled timing, an image is formed on the recording surface of the recording paper Pa as shown in  FIG. 19 , for example. 
       FIG. 19  shows a part of the image region formed by a single head chip  112 A as the head chip  112 A was moved in the arrow A direction, and a part of the image region formed by a single head chip  112 B as the head chip  112 B was moved also in the arrow A direction. 
     The region GRA is made up of a set of dots IDA formed as the Ink droplets ejected from the head chip  112 A adhered to the recording surface of the recording paper Pa, and the region GRB is made up of a set of dots IDB formed by the ink droplets ejected from the head chip  112 B as they adhered to the recording surface of the recording paper Pa. The region GRC is made up or a set of dots IDC formed by the ink droplets ejected from the compensatory ejection orifices  116   bm   1  and  116   bm   2  of the head chip  112 B as they adhered to the recording surface of the recording paper Pa. 
     Therefore, it is possible to obtain an image which does not have the so-called white or black streak traceable to the deviation of the positional relationship between the head chip  112 A and head chip  112 B, across the area correspondent to the range in which the head chip  112 A and head chip  112 B partially overlap with each other in terms of the moving direction of the carriage, that is, the arrow A direction. 
     Also in the case of this embodiment, the head design may be such that the compensatory ejection orifices  102   mb  are the same as, or different from, the normal ejection orifices, in terms of ink droplet volume. 
     (Embodiment 5) 
       FIG. 20  shows the essential portion of the third embodiment of a recording head in accordance with the present invention. 
     Like the fourth embodiment, this fifth embodiment in  FIG. 20  has a supporting plate  110 , a set of head chips  122 A arranged on one of the two largest vertical flat surfaces of the supporting plate  110 , and a set of head chips  122 B arranged on the other of the two largest vertical flat surfaces of the supporting plate  110 . The head chips  122 A are arranged in a straight line roughly perpendicular to the moving direction of the carriage  40 , that is, the direction indicated by an arrow mark A, with the provision of a predetermined interval between adjacent two head chips  122 A, and so are the head chips  122 A, with the provision of the predetermined interval between the adjacent two head chips  122 B. In terms of the ordinal number, inclusive of both sets of the head chips, determined based on the distance from one of the lengthwise ends of the supporting plate  110 , the head chips are arranged in the zigzag fashion, with the provision of a predetermined interval between a given head chip  122 A and the head chip  122 B adjacent thereto. Further, the two sets of head chips  122 A and  122 B are positioned with the use of a predetermined jig, with a tolerance of approximately ±0.1 mm, for example. 
     The head chip  122 A is similar in internal structure to the head chip  112 A of the fourth embodiment described above. The liquid path formation member  126 A has a plurality of ejection orifices  126   ai  (i=1−n, n being integer), which are open, being aligned, at one of the end surfaces, with the provision of a predetermined interval PPH between the two adjacent ejection orifices. The head chip  122 B is similar in internal structure to the head chip  122 A. 
     Referring to  FIG. 18 , however, not only is the liquid path formation member  126 B of each head chip  122 B provided with a plurality of ejection orifices  126   bi  (i=1−n, n being integer) arranged on one of the end surfaces, approximately at the middle in terms of the widthwise direction of the liquid formation member  126 B, with the provision of a predetermined interval PPH between the centers of the adjacent two ejection orifice  126   bi , as is the liquid path formation member  126 A of each head chip  122 A, but also it is provided with a plurality of compensatory ejection orifices  126   bm , which are located across one, or both, end portions of the head chip  122 B in terms of the direction in which the normal ejection orifices  126   ai  are aligned. 
     More specifically, referring to  FIG. 20 , the plurality of compensatory ejection orifices  126   bm , for example, the compensatory ejection orifices  126   bm   1 ,  126   bm   2 ,  126   bm   3 ,  126   bm   4 ,  126   bm   5 ,  126   bm   6 ,  126   bm   7 , and  126   bm   8 , are aligned across the portion of the head chip  122 B, which partially overlaps, in terms of the moving direction of the recording head, with the portion of the head chip  122 A between the right edge and where the twelfth ejection orifice, counting from the same lengthwise edge, of the head chip is. 
     There is a distance of PPH between the center of the compensatory ejection orifice  126   bm   1  and the center of the leftmost normal ejection orifice  126   bi . The distance PPG between the centers of the adjacent two compensatory ejection orifices  126   bm  in terms of their alignment direction is greater than the distance PPH. Further, the compensatory ejection orifices  126   bm   1 - 126   bm   8  are made the same in the area size of their openings as the normal ejection orifices  126   bi , for example. 
     When a recording operation is carried out by a recording head unit comprising the set of head chips  122 A and set of head chips  122 B structured as described above, the host computer  70  creates the compensatory data DS, based on the deviation in the positional relationship between a given head chip  122 A and the head chip  122 B adjacent thereto, as in the above described preceding embodiments. More specifically, each recording head unit is measured with the use of a microscope or the like. Then, for example, when the extension of a referential line JL, which is the extension of the center line between any two ejection orifices located in one of the lengthwise end portions of the head chip  122 A, coincides with, for example, the centerline between the compensatory ejection orifices  122   bm   6  and  122   bm   7 , the compensatory data DS are created so that the compensatory ejection orifices  126   bm   1 - 126   bm   6 , which are between the ejection orifice of the head chip  122 A next to the referential line JL, and the leftmost normal ejection orifice  126   bi  of the head chip  112 B, in  FIG. 20 , are used during a recording operation. In this case, none of the ejection orifices  126   ai  located in the right portion of the head chip  122 A, with respect to the referential line JL, is used. 
     On the other hand, if the extension JL′, of the referential line JL coincides with, for example, the center line between the compensatory election orifices  122   bm   7  and  122   bm   8 , as represented by the two-dot chain line, all of the compensatory ejection orifices  126   bm   1 - 126   bm   7  are used. 
     The CPU  74  supplies to the head driver  76 , the data obtained by carrying out the above described processes. 
     While carrying out the above described is processes, the CPU  74  also uses the compensatory data DSM, based on the compensatory ejection orifices selected as described above, and read from the RAM  80 , and the image formation data, to create a set of data for making the selected compensatory ejection orifices carry out recording operations, and supplies the created data to the head driver  76 . 
     Based on these sets of data supplied from the CPU  74 , the head driver  76  creates a plurality or sets of drive control pulse signals, and supplies them to the recording head unit. 
     Thus, as the recording head unit is driven with the controlled timing, an image is formed on the recording surface of the recording paper Pa as shown in  FIG. 21 , for example. 
       FIG. 21  shows a part of the image region formed by a single head chip  122 A as the head chip  122 A was moved in the arrow A direction, and a part of the image region formed by a single head chip  122 B as the head chip  122 B was moved also in the arrow A direction. 
     The region GRA′ is made up of a set of dots IDA formed by the ink droplets ejected from the head chip  122 A as they adhered to the recording surface of the recording paper Pa, and the region GRB′ is made up of a set of dots IDB formed by the ink droplets ejected from the head chip  122 B as they adhered to the recording surface of the recording paper Pa. The region GRC′ is made up of a set of dots IDC formed by the ink droplets ejected from the compensatory ejection orifices  126   bm   1  and  126   bm   6  of the head chip  122 B as they adhered to the recording surface of the recording paper Pa. 
     Therefore, it is possible to obtain an image which does not have the so-called white or black streak traceable to the deviation of the positional relationship between the head chip  122 A and head chip  122 B, across the area correspondent to the range in which the lengthwise end portions of the head chip  122 A and head chip  122 B partially overlap with each other in terms of the moving direction of the carriage, that is, the arrow A direction. 
     Also in the case of this embodiment, the head design may be such that the compensatory ejection orifices  126   mb  are different from the ejection orifices  126   bi , in terms of ink droplet volume. When the value of the distance PPE is close to the value of the distance PPG, a desirable image, that is, an image free of density irregularity, can be obtained by not making the compensatory ejection orifices  126   bm  excessively different in ink droplet volume from the ejection orifices  126   bi.    
     In this embodiment, if the pitch of the ejection orifices  126   ai  and the pitch of the ejection orifices  126   bi  are set to 600 dpi (PPH=42.5 μm); the pitch of the compensatory ejection orifices  126   bm  is set to 41.5 μm; and the deviation in the positional relationship between the two sets of head chips, 10/(42.5−41.5)=10. Thus, the deviation in the positional relationship between the adjacent two (lots formed on the portion of a recording paper corresponding to the portion of a recording head unit where the end portion of one head chip partially overlaps with the end portion of another chip in terms of the moving direction of the recording head can be reduced to less than 1 μm, with the use of 10 compensatory ejection orifices. 
     This embodiment was described with reference to such a head design that the pitch of the ejection orifices  126   ai  of each head chip  122 A was the same as the pitch of the ejection orifices  126   bi  of each head chip  122 B. 
     However, when the pitch of the ejection orifices  126   ai  of a head chip  122 A is very close in value to the pitch of the compensatory ejection, orifices  126   bm  of a head chip  122 B, the pitch of the ejection orifices  126   bi  of the head chip  122 B may be made equal to the pitch of the compensatory ejection orifices  126   bm . Such an arrangement can provide the same effects as those described above. 
     Of course, the present invention includes such an arrangement. As described above, according to this embodiment, the pitch of the head chips in one of the two straight lines, in which they are arranged, is made slightly different from that of the head chips in other line, and the ejection orifices to be used are optimally selected in accordance with head chip usage, making it possible to obtain an image, which is drastically smaller in the irregularities associated with the portion of a recording unit where the end portion of a given head chip in the aforementioned one line, and the end portion of the head chip in the other line, adjacent thereto, overlap with each other, in terms of the moving direction of the recording head unit, compared to an image formed with the use of a conventional recording head unit. 
       FIG. 22  shows the essential portion of another example of a recording apparatus compatible with any of the above described embodiments of a recording head unit in accordance with the present invention, for describing the general structure thereof. 
     The example of a recording apparatus shown in  FIG. 1  is a serial printer, whereas this example of a recording apparatus is a full-line printer. This example of a recording apparatus is also provided with a control block such as the one shown in FIG.  3 . 
     This apparatus has yellow, magenta, cyan, and black ink supply portions  137 Y,  137 M,  137 C, and  137 B (which hereinafter will be generically referred to as ink supply portions  137 ), and four ink jet heads  111 Y.  111 M,  111 C, and  111 B (which hereinafter will be generically referred to as ink jet heads  111 ) connected to the ink supply portion  137 , one for one. 
     Each of the heat-generating resistors (electrothermal transducers) is individually turned on or off by the head driver  40  connected to a controlling apparatus  139 . The ink jet heads  111  are arranged in the conveyance direction of a conveyance belt  141 , with the provision or predetermined intervals, opposing a platen  142  with the interposition of a conveyance belt  141 . They are enabled to be moved vertically, that is, perpendicular to the platen  143 , by a head moving means  143  for the recovery process controlled by the controlling apparatus  139 . Next to one of the side walls of each ink jet head  111 , a head cap  145  for ejecting the bodies of stagnant ink in the ink paths from the ejection orifices, to recover the performance of the ink jet head  111 , is disposed, being offset from the ink jet head by half the ink jet head arrangement pitch. In operation, it is moved by a cap moving means  146  controlled by the controlling apparatus  139 , so that it is positioned directly below the corresponding ink jet head  111  to catch the waste ink ejected from the ejection orifices  124 . 
     The conveyance belt  141  for conveying a printing paper  144  is wrapped around, being thereby suspended by, a driving roller connected to a belt drive motor  147 , Its movement is switched by a motor driver  149  connected to the controlling apparatus  139 . On the upstream side of the conveyance belt  141 , a charging device  150  is disposed, which charges the conveyance belt to adhere the printing paper  144  to the conveyance belt  141 . This charging device  150  is turned on or off by a charging device driver  151  connected to the controlling apparatus  139 . To the pair of feeding rollers  152  for feeding the printing paper  144  onto the conveyance belt  141 , a motor  153  for rotationally driving this pair of paper feeding rollers  152  is connected. The movement of this motor  153  is switched by a motor driver  154  connected to the controlling apparatus  139 . 
     Thus, before the actual process of printing an image on the printing paper  144  begins, the ink jet heads  111  are moved upward away from the platen  142 , and then, the head caps  145  are moved to the positions directly below the ink jet heads  111 , one for one, to restore the performance of the ink jet heads  111 . After the completion of the ink jet head performance recovery process, the head caps  145  are returned to their original locations, that is, their standby positions. Then, the ink jet heads  111  are moved toward the platen  142 , back to their printing positions. 
     Next, the conveyance belt  141  is driven, with the charging device  150  turned on. Then, the printing paper  144  is fed onto the conveyance belt  141 , by the pair of paper feeding rollers  152 . Then, an intended image is printed on the printing paper  144  by the ink jet heads  111 . 
     As is evident from the above description of the preferred embodiments of the present invention, according to the present invention, which relates to a recording head unit having two sets of head chips arranged in two straight lines, one for one, and a recording apparatus equipped with such a recording head, each head chip in at least one of the two lines is provided with a single or plurality of compensatory ejection orifices, which are located in one, or both, of the end portions of the head chip, by which the head chip partially overlaps with the end portion of the corresponding head chip in the other line, in terms of the direction perpendicular to the direction in which the head chips are aligned. Therefore, even if the positional relationship between the two sets of head chips in the recording head unit is deviant, it is possible to prevent the formation of an inferior image on the recording surface of recording medium 
     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.