Patent Publication Number: US-9403376-B2

Title: Thermal head and thermal printer equipped with the thermal head

Description:
TECHNICAL FIELD 
     The present invention relates to a thermal head and a thermal printer equipped with the thermal head. 
     BACKGROUND ART 
     Various types of thermal heads have been proposed to date as printing devices for use in facsimiles, video printers, and so forth. For example, there is known a thermal head comprising: a substrate; a heat generating portion disposed on the substrate; a driving IC which controls actuation of the heat generating portion; and a covering member which covers the driving IC, the covering member serving also as an ink ribbon guide, in which a recording medium is conveyed while making contact with the covering member (refer to Patent Literature 1, for example). Moreover, when the substrate is seen in a plan view, this thermal head is composed of a first region defined by extending an area where the driving IC is disposed in a sub scanning direction, and a second region being an area other than the first region. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Unexamined Patent Publication JP-A 01-281956 (1989) 
     SUMMARY OF INVENTION 
     Technical Problem 
     In the thermal head as above described, however, the height of the second region free of the driving IC is lower than the height of the first region, thus causing poor contacting condition between a recording medium and the thermal head, which gives rise to the possibility of occurrence of wrinkles in the recording medium. 
     Solution to Problem 
     A thermal head in accordance with one embodiment of the invention comprises: a substrate; a heat generating portion disposed on the substrate; a driving IC disposed on the substrate and controlling actuation of the heat generating portion; a covering member covering the driving IC; and a projection portion disposed on the substrate and making contact with a recording medium under conveyance. Moreover, the substrate comprises a first region and a second region in a plan view, the first region being defined by extending an area where the driving IC is disposed in a sub scanning direction and the second region being an area other than the first region. In addition, the projection portion is disposed on the second region closer to the heat generating portion than the area where the driving IC is disposed. 
     A thermal printer in accordance with one embodiment of the invention comprises: the thermal head as described above; a conveyance mechanism conveying the recording medium onto the heat generating portion; and a platen roller pressing the recording medium onto the heat generating portion. 
     Advantageous Effects of Invention 
     According to the invention, the possibility of causing wrinkles in a recording medium can be decreased. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a plan view showing a first embodiment of a thermal head according to the invention; 
         FIG. 2  is a sectional view taken along the line I-I shown in  FIG. 1 ; 
         FIG. 3  is an enlarged plan view of a vicinity of a projection portion of the thermal head shown in  FIG. 1 ; 
         FIG. 4  is a conceptual diagram illustrating a condition of contact between a recording medium and the thermal head shown in  FIG. 1 , wherein  FIG. 4( a )  shows the vicinity of a driving IC, and  FIG. 4( b )  shows the vicinity of the projection portion; 
         FIG. 5  is a view showing the general structure of the first embodiment of a thermal printer according to the invention; 
         FIG. 6  is a plan view showing a second embodiment of the invention; 
         FIG. 7  shows a thermal head in accordance with a third embodiment of the invention, wherein  FIG. 7( a )  is an enlarged plan view of the vicinity of the projection portion, and  FIG. 7( b )  is a plan view showing a modified example of the thermal head shown in  FIG. 7( a ) ; 
         FIG. 8  shows a thermal head in accordance with a fourth embodiment of the invention, wherein  FIG. 8( a )  is an enlarged plan view of the vicinity of the projection portion, and  FIG. 8( b )  is a plan view showing a modified example of the thermal head shown in  FIG. 8( a ) ; 
         FIG. 9  is an enlarged plan view of the vicinity of the projection portion in a thermal head in accordance with a fifth embodiment of the invention; and 
         FIG. 10  is a conceptual diagram illustrating a contacting condition in the vicinity of the projection portion of the thermal head shown in  FIG. 9 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     &lt;First Embodiment&gt; 
     Hereinafter, a thermal head X 1  will be described with reference to  FIGS. 1 to 4 . The thermal head X 1  comprises: a heatsink  1 ; a head substrate  3  placed on the heatsink  1 ; and a connector  31  connected to the head substrate  3 . In  FIG. 1 , the diagrammatic representation of the connector  31  is omitted, and, a region where the connector  31  is placed is indicated by alternate long and short dashed lines. 
     While the connector  31  will hereafter be described as a connecting member which makes external electrical connection, other members having flexibility such as a flexible printed wiring board, a glass epoxy substrate, or a polyimide substrate, can be used instead. In a case where external electrical connection is established by a flexible printed wiring board, a reinforcing plate made of resin such for example as a phenol resin, a polyimide resin, or a glass epoxy resin (not shown in the drawing) may be disposed between the flexible printed wiring board and the heatsink  1 . 
     The heatsink  1  has the form of a plate, and, in a plan view, the heatsink  1  is rectangular-shaped. The heatsink  1  is formed of a metal material such for example as copper, iron, or aluminum, and has the capability of dissipating, of heat generated by a heat generating portion  9  of the head substrate  3 , heat which is not responsible for printing. Moreover, the head substrate  3  is bonded to the upper surface of the heatsink  1  by means of double-faced tape, an adhesive, or otherwise (not shown). 
     In a plan view, the head substrate  3  has the form of a plate, and, constituent members of the thermal head X 1  are each disposed on a substrate  7  of the head substrate  3 . The head substrate  3  has the function of performing printing on a recording medium (not shown) in response to an electric signal issued from outside. 
     As shown in  FIGS. 1 and 2 , the connector  31  comprises: a plurality of connector pins  8 ; and a housing  10  which accommodates the plurality of connector pins  8 . The plurality of connector pins  8  have one sides left exposed outside of the housing  10 , and have other sides stored within the housing  10 . The plurality of connector pins  8  have the function of ensuring electrical conduction between each of various electrodes of the head substrate  3  and an externally-disposed power supply, and are electrically independent of each other. The connector pins  8  are required to have electrical conductivity, and are therefore formed of a metal or an alloy. 
     The housing  10  has the function of accommodating the respective connector pins  8  in a state of being electrically independent of each other, and is therefore formed of an insulating member. The housing  10  effects supply of electricity to the head substrate  3  by means of attachment and detachment of an externally-disposed connector (not shown). The housing  10  is made of, for example, a thermosetting resin, an ultraviolet-curable resin, or a photo-curable resin. 
     Hereinafter, each of members constituting the head substrate  3  will be described. 
     The substrate  7  is formed of an electrically insulating material such as alumina ceramics, or a semiconductor material such as single-crystal silicon. 
     A heat storage layer  13  is formed on the upper surface of the substrate  7 . The heat storage layer  13  comprises: an underlayer portion  13   a ; and a protuberant portion  13   b . The underlayer portion  13   a  is formed over the left half of the upper surface of the substrate  7 . The protuberant portion  13   b  extends in the form of a strip along a main scanning direction of a plurality of heat generating portions  9 , and has a substantially semi-elliptical sectional profile. The underlayer portion  13   a  is disposed near the heat generating portion  9  while being located below a protective layer  25  which will hereafter be described. The protuberant portion  13   b  acts to press a recording medium which is subjected to printing against the protective layer  25  formed on the heat generating portion  9  in a satisfactory manner. 
     The heat storage layer  13  is formed of glass having a low heat conductivity, and accumulates part of heat generated by the heat generating portion  9  temporarily. Accordingly, the heat storage layer  13  is able to shorten the time required for a temperature rise in the heat generating portion  9 , and thus acts to improve the thermal response characteristics of the thermal head X 1 . 
     For example, the heat storage layer  13  is formed by applying a predetermined glass paste, which is obtained by blending a suitable organic solvent in glass powder, onto the upper surface of the substrate  7  by means of heretofore known screen printing or otherwise, and subsequently firing the paste. 
     An electrical resistance layer  15  is disposed on the upper surface of the heat storage layer  13 , and, on the electrical resistance layer  15  are disposed a ground electrode  4 , a common electrode  17 , an individual electrode  19 , an IC-connector connection electrode  21 , and an IC-IC connection electrode  26 . The electrical resistance layer  15  is subjected to patterning so as to have the same shape as the ground electrode  4 , the common electrode  17 , the individual electrode  19 , the IC-connector connection electrode  21 , and the IC-IC connection electrode  26 , and has an exposed region serving as an exposed electrical-resistance layer  15  region lying between the common electrode  17  and the individual electrode  19 . 
     As shown in  FIG. 1 , there are arranged exposed regions of the electrical-resistance layer  15  in an array on the protuberant portion  13   b  of the heat storage layer  13 , and, each of the exposed regions constitutes the heat generating portion  9 . The plurality of heat generating portions  9 , while being illustrated in simplified form in  FIG. 1  for convenience in explanation, are arranged at a density of 100 dpi to 2400 dpi (dot per inch), for example. The electrical resistance layer  15  is formed of a material having a relatively high electrical resistance such for example as a TaN-based material, a TaSiO-based material, a TaSiNO-based material, a TiSiO-based material, a TiSiCO-based material, or a NbSiO-based material. Thus, upon application of a voltage to the heat generating portion  9 , the heat generating portion  9  is caused to generate heat under Joule heating effect. 
     The ground electrode  4 , the common electrode  17 , the individual electrode  19 , the IC-connector connection electrode  21 , and the IC-IC connection electrode  26  are formed of a material having electrical conductivity, for example, one metal material selected from among aluminum, gold, silver, and copper, or an alloy of these metals. 
     The common electrode  17  comprises: a main wiring portion  17   a ; a sub wiring portion  17   b ; a lead portion  17   c ; and a thick electrode portion  17   d . The main wiring portion  17   a  extends along one long side of the substrate  7 . The sub wiring portion  17   b  extends along each of one and the other short sides of the substrate  7 . The lead portion  17   c  extends from the main wiring portion  17   a  toward each of the heat generating portions  9 . The thick electrode portion  17   d , which is disposed on the main wiring portion  17   a  and the sub wiring portion  17   b , is made thicker than the other portions of the common electrode  17 . The common electrode  17  provides electrical connection between the connector  31  and each of the heat generating portions  9 . 
     The thermal head X 1  is configured so that an electric current fed from the sub wiring portion  17   b  located at each end thereof in the direction of arrangement of the heat generating portions  9  (hereafter also referred to as “main scanning direction”) passes through the main wiring portion  17   a , flows through each of the lead portions  17   c , and is thereby supplied to each of the heat generating portions  9 . On the main wiring portion  17   a , as well as on the sub wiring portion  17   b , there is provided the thick electrode portion  17   d  which acts to increase the current carrying capacity of the main wiring portion  17   a  and the sub wiring portion  17   b . Exemplary of the thick electrode portion  17   d  is an Ag paste. 
     A plurality of individual electrodes  19  provide electrical connection between each of the heat generating portions  9  and a driving IC  11 . Moreover, given that the heat generating portions  9  are bunched together in groups, the individual electrodes  19  allow the heat generating portions  9  in each group to make electrical connection with a corresponding one of the driving ICs  11  prepared for the heat generating portion groups, respectively. 
     A plurality of IC-connector connection electrodes  21  have one ends connected to the driving IC  11  and have other ends led out to an end face  7   a  of the substrate  7 . The led-out ends are electrically connected to the connector  31 , thereby permitting electrical connection between the driving IC  11  and the connector  31 . The plurality of IC-connector connection electrodes  21  connected to each of the driving IC  11  are configured by a plurality of wiring lines having different functions. 
     The ground electrode  4 , which is placed between the IC-connector connection electrode  21  and the main wiring portion  17   a  of the common electrode  17 , has a large area. The ground electrode  4  is grounded and maintained at a potential of 0 to 1 V. 
     A plurality of IC-IC connection electrodes  26  provide electrical connection between the driving ICs  11  arranged adjacent each other. The plurality of IC-IC connection electrodes  26  are disposed in correspondence to the IC-connector connection electrodes  21 , and transmit various signals to the adjacent driving ICs  11 . That is, an electric current is fed from the connector  31  to the driving IC  11  by way of the IC-connector connection electrodes  21  and the IC-IC connection electrodes  26 . 
     As shown in  FIG. 1 , the driving IC  11  is placed in correspondence to each of the groups including the plurality of heat generating portions  9 , and is connected to the individual electrode  19 , the IC-connector connection electrode  21 , and the ground electrode  4 . The driving IC  11  has the function of controlling the current-carrying state of each of the heat generating portions  9 . It is advisable to use a switching member having a plurality of built-in switching elements as the driving IC  11 . 
     As shown in  FIG. 1 , in a sub scanning direction S coincident with a conveying direction S in which a recording medium (not shown) is conveyed, in the thermal head X 1 , the substrate  7  comprises a first region R 1  and a second region R 2  in a plan view, the first region R 1  being defined by extending an area where the driving IC  11  is disposed in the sub scanning direction and the second region R 2  being an area other than the first region R 1 . 
     The first region R 1  has a width which is equal to the width of the driving IC  11  in the main scanning direction, and extends along the sub scanning direction S while maintaining the width. In other words, in a plan view, the first region R 1  is a region defined by virtual lines extending in the sub scanning direction S along side faces of the driving IC  11  that are perpendicular to the main scanning direction. 
     The electrical resistance layer  15 , the common electrode  17 , the individual electrode  19 , the ground electrode  4 , the IC-connector connection electrode  21 , and the IC-IC connection electrode  26  thus far described are formed by, for example, stacking layers of their constituent materials on the heat storage layer  13  one after another by a heretofore known thin-film forming technique such as a sputtering method, and subsequently working the resultant layered body into predetermined patterns by a heretofore known technique such as a photo-etching method. Note that the common electrode  17 , the individual electrode  19 , the ground electrode  4 , the IC-connector connection electrode  21 , and the IC-IC connection electrode  26  can be formed at one time through the same process steps. Meanwhile, the thick electrode portion  17   d  can be formed by means of printing before or after the process of working the different electrodes into predetermined patterns. 
     As shown in  FIGS. 1 and 2 , the protective layer  25  which covers the heat generating portion  9 , part of the common electrode  17 , and part of the individual electrode  19 , is formed on the heat storage layer  13  formed on the upper surface of the substrate  7 . In  FIG. 1 , for convenience in explanation, a region where the protective layer  25  is formed is indicated by alternate long and short dashed lines, and its diagrammatic representation is omitted. 
     The protective layer  25  is intended to protect the covered areas of the heat generating portion  9 , the common electrode  17 , and the individual electrode  19  against corrosion caused by adhesion of, for example, atmospheric water content, or against wear caused by contact with a recording medium which is subjected to printing. 
     The protective layer  25  can be formed from SiN, SiO, SiON, SiC, SiCN, diamond-like carbon, or the like, and, the protective layer  25  may either be of a single layer or be composed of a stack of layers. Such a protective layer  25  can be produced by a thin-film forming technique such as the sputtering method, or a thick-film forming technique such as a screen printing method. 
     Moreover, as shown in  FIGS. 1 and 2 , a cover layer  27  which partly covers the ground electrode  4 , the common electrode  17 , the individual electrode  19 , and the IC-connector connection electrode  21  is disposed on the substrate  7 . In  FIG. 1 , for convenience in explanation, a region where the cover layer  27  is formed is indicated by alternate long and short dashed lines. 
     The cover layer  27  is intended to protect the covered areas of the ground electrode  4 , the common electrode  17 , the individual electrode  19 , the IC-IC connection electrode  26 , and the IC-connector connection electrode  21  against oxidation caused by contact with air, or corrosion caused by adhesion of atmospheric water content, for example. 
     In order to provide more secure protection for the common electrode  17  and the individual electrode  19 , as shown in  FIG. 2 , it is preferable that the cover layer  27  is so formed as to overlie an end part of the protective layer  25 . The cover layer  27  can be formed from a resin material such for example as an epoxy resin or a polyimide resin using a thick-film forming technique such as the screen printing method. 
     The cover layer  27  is formed with an opening (not shown) for leaving the individual electrode  19 , the IC-IC connection electrode  26 , and the IC-connector connection electrode  21  connected to the driving IC  11  exposed, so that the wiring lines can be connected to the driving IC  11  through the opening. Moreover, the driving IC  11  is, in a state of being connected to the individual electrode  19 , the IC-IC connection electrode  26 , and the IC-connector connection electrode  21 , covered with a covering member  29  formed of resin such for example as an epoxy resin or a silicone resin for the sake of protection of the driving IC  11  and also protection of the area of connection between the driving IC  11  and the wiring lines. In the present embodiment, the covering member  29  is disposed so as to straddle over a plurality of driving ICs  11 . The height of the cover layer  27  from the substrate  7  can be determined as appropriate in accordance with the form of the thermal head X 1 , and, a desirable range of the height is from 200 to 500 μm. 
     As shown in  FIG. 2 , at that side of the cover layer  27  located toward the end face  7   a  of the main surface (not shown) of the substrate  7 , the ends drawn from the different electrodes are exposed from an exposed area where the different electrodes are left exposed (not shown) so as to be electrically connected to the connector  31 . 
     The connector  31  is disposed on the substrate  7 , and, the connector pin  8  is electrically connected to the led-out ends of the different electrodes by an electrically-conductive member  23 . In the thermal head X 1 , the connector  31  is disposed at each of the opposite ends and the midportion of the thermal head X 1  in the main scanning direction. Exemplary of the electrically-conductive member  23  are solder and an anisotropic conductive adhesive obtained by blending conductive particles in an electrically insulating resin. Note that a Ni-, Au-, or Pd-plating layer (not shown) may be disposed between the electrically-conductive member  23  and the led-out ends of the different electrodes. 
     The thermal head X 1  is provided with a protecting member  12  which protects, at least partly, the connector  31 . The protecting member  12  is disposed so as to cover the connector pin  8 , part of the upper surface of the housing  10 , and part of the cover layer  27 , as well as to cover the exposed area completely when seen in a plan view. 
     The protecting member  12  can be formed of a thermosetting resin, a thermosoftening resin, an ultraviolet-curable resin, or a visible light-curable resin, for example. Moreover, in a case where the different electrodes need to be electrically independent of each other, it is preferable that the protecting member  12  has an electrically insulating property. 
     Moreover, the protecting member  12  covers the connector pin  8  of the connector  31  which assures the electrical conduction, and, preferably, the protecting member  12  is disposed also on part of the upper surface of the housing  10 . By doing so, the connector pin  8  can be entirely covered with the protecting member  12 , thereby assuring the electrical conduction more positively. 
     Referring to  FIGS. 3 and 4 , a projection portion  2  will be described in detail.  FIG. 3  shows the vicinity of the projection portion  2  in an enlarged manner, and  FIG. 4  is a conceptual diagram illustrating a condition of contact between a recording medium P and the covering member  29 , as well as the projection portion  2 . A solid line drawn in  FIGS. 4( a ) and 4( b )  indicates a position of conveyance of the recording medium P in the present embodiment, whereas a broken line drawn in  FIG. 4( b )  indicates a position of conveyance of the recording medium P in a case where the projection portion  2  is assumed to be absent. 
     As shown in  FIG. 3 , the projection portion  2  is disposed at a center of the substrate  7  in the main scanning direction so as to lie in the second region R 2 . Moreover, the projection portion  2  is disposed in a position spaced downstream from the driving IC  11  in the conveying direction S of the recording medium P. Furthermore, the projection portion  2  is disposed on the second region R 2  closer to the heat generating portion  9  than the area where the driving IC is disposed. 
     The IC-connector connection electrode  21  and the IC-IC connection electrode  26  are arranged around the projection portion  2 , and thus the projection portion  2  is placed so as to be surrounded by the IC-connector connection electrode  21  and the IC-IC connection electrode  26 . 
     As shown in  FIG. 4 , a convexity  6  is disposed below the projection portion  2 , and, the cover layer  27  is situated over the convexity  6 . The cover layer  27  covers not only the convexity  6 , but also the vicinity of the convexity  6 . Thus, the projection portion  2  is composed of the convexity  6  and the cover layer  27 . Note that the convexity  6  is disposed so as not to make contact with the IC-connector connection electrode  21  and the IC-IC connection electrode  26 . That is, the convexity  6  is electrically isolated from the IC-connector connection electrode  21  and the IC-IC connection electrode  26 . 
     The convexity  6  can be formed of a material similar to the material constituting the thick electrode portion  17   d . Moreover, the convexity  6  can be formed by means of printing. Therefore, by forming the convexity  6  concurrently with the formation of the thick electrode portion  17   d , it is possible to achieve shortening of takt time, and thereby increase the manufacturing efficiency. Note that the convexity  6  may also be formed by raising part of the substrate  7 . 
     It is preferable that the height of the convexity  6  from the substrate  7  falls in the range of 15 to 30 μm. The projection portion  2  has a rectangular shape when seen in a plan view, and its height h 3  from the substrate  7  preferably falls in the range of 40 to 70 μm. Moreover, the projection portion  2  is preferably given a surface roughness greater than the surface roughness of other area of the cover layer  27  than the projection portion  2 . This makes it possible to render the recording medium P less slippery, and thereby improve the condition of intimate contact between the projection portion and the recording medium under conveyance. 
     A height h 1  of the covering member  29  from the substrate  7  in the first region R 1  is greater than a height h 2  of the covering member  29  from the substrate  7  in the second region R 2 . This is ascribable to the presence or absence of the driving IC  11  located in a lower part of the covering member  29 . Note that the height h 1 , h 2  of the covering member  29  from the substrate  7  refers to the level of the vertex of the covering member  29  situated above the driving IC  11 , namely the height of that part of the covering member which is contacted by the recording medium P from the substrate  7 . 
     It is preferable that the height h 1  of the covering member  29  from the substrate  7  falls in the range of 300 to 500 μm. Moreover, the height h 2  of the covering member  29  from the substrate  7  preferably falls in the range of 200 to 400 μm. This makes it possible to support the conveyance of the recording medium P. 
     In measurement of height from the substrate  7 , for example, with use of a contact type or non-contact type surface roughness meter, a distance from a reference point can be measured. For example, the vertex of the protuberant portion  13   b  of the heat storage layer  13  can be defined as the reference point. The surface roughness of the projection portion  2  and that of the cover layer  27  can be also measured by a similar method. 
     Among various members constituting the thermal head X 1 , and, particularly among the members disposed on the substrate  7 , the driving IC  11  has a noticeably large size. Therefore, the level of the surface of that part of the thermal head X 1  which is provided with the driving IC  11  and the level of the surface of that part of the thermal head X 1  which is free of the driving IC  1  differ greatly from each other. 
     Also in the case where the covering member  29  is so disposed as to straddle over the plurality of driving ICs  11  as shown in  FIG. 1 , the first region R 1  is greater in height than the second region R 2 . The recording medium P is conveyed while making contact with the covering member  29 , and, in the first region R 1 , the recording medium P is maintained at a predetermined level under the support of the covering member  29 . 
     However, in a conventional thermal head devoid of the projection portion  2 , since the height h 1 , h 2  of the covering member  29  from the substrate  7  varies depending on the presence or absence of the driving IC  11  located in a lower part thereof, it follows that the condition of conveyance of the recording medium P in the first region R 1  differs from that in the second region R 2 . That is, in the second region R 2 , as indicated by the chain-dotted line shown in  FIG. 4( b ) , the recording medium P may sag down, which leads to a difference in recording medium P-to-covering member  29  distance between the first region R 1  and the second region R 2 . Therefore, the first region R 1  and the second region R 2  differ from each other in the condition of conveyance of the recording medium P. This gives rise to the possibility of causing wrinkles in the recording medium P which is being carried over the second region R 2 . 
     In contrast, in the thermal head X 1 , the projection portion  2  is disposed on the second region R 2  closer to the heat generating portion  9  than the area where the driving IC  11  is disposed, and, the projection portion  2  can make contact with the recording medium P. Thus, as indicated by the solid line in  FIG. 4( b ) , the projection portion  2  is able to lift up the sagging recording medium P. This makes it possible to restrain the recording medium P against sagging motion, and thereby render the condition of conveyance of the recording medium P approximately uniform, wherefore the possibility of causing wrinkles in the recording medium P can be decreased. 
     Moreover, since the recording medium P makes contact with the covering member  29  and the projection portion  2 , the recording medium P is supported at two points. Therefore, even if the covering member  29  and the projection portion  2  are subjected to a stress when pressed by the recording medium P, the stress can be dispersed. 
     Moreover, in the process of performing sputtering of the protective layer  25 , there may be a case where a plurality of thermal heads X 1  are stacked while being displaced from each other by a predetermined distance so that their protective layers  25  can be formed at one time. In this case, the projection portion  2  acts to decrease the possibility of causing damage to the electrodes and so forth due to the overlapping arrangement of the thermal heads X 1 . More specifically, at the time of stacking the thermal heads X 1  one upon another, by placing each thermal head X 1  on the projection portion  2 , a space can be formed between the stacked thermal heads X 1 . This space helps protect the electrodes and so forth. 
     Moreover, the projection portion  2  is placed in a position spaced downstream from the driving IC  11  in the conveying direction S of the recording medium P. Accordingly, the recording medium P is brought into contact with the projection portion  2  after making contact with the covering member  29  located above the driving IC  11 . Thus, the recording medium P can be stably supported by the covering member  29 , and also, the recording medium P in a state of sagging down in a region between the driving IC  11  and the heat generating portion  9  can be upheld at a predetermined level by the projection portion  2 . As a result, the recording medium P can be conveyed smoothly to the heat generating portion  9 . 
     Moreover, since the projection portion  2  is located between the covering member  29  and the heat generating portion  9 , it follows that the recording medium P is brought into contact with the projection portion  2  after making contact with the covering member  29 . Accordingly, the recording medium P which is being carried toward the heat generating portion  9  can be upheld at a predetermined level, with consequent accomplishment of smooth conveyance of the recording medium P to the heat generating portion  9 . In addition, the projection portion  2  ensures more stable conveyance of the recording medium P to the heat generating portion  9 . 
     The height h 3  of the projection portion  2  from the substrate  7  is shorter than the height h 1 , h 2  of the covering member  29  from the substrate  7 . Thus, the recording medium P is supported by the taller covering member  29 , thereby achieving stable conveyance of the recording medium P. This is because the covering member  29  is greater in volume and strength than the projection portion  2 . 
     Moreover, in the conveying direction S, the height h 3  of the projection portion  2  located on the downstream side from the substrate  7  is shorter than the height h 2  of the driving IC  11  located on the upstream side in the second region R 2  from the substrate  7 . Accordingly, also in the second region R 2 , the recording medium P can be supported by the covering member  29 , and the projection portion  2  is able to convey the recording medium P smoothly to the heat generating portion  9 . 
     Moreover, it is preferable that the distance between the projection portion  2  and the heat generating portion  9  is 0.3 to 0.8 time the distance between the covering member  29  and the heat generating portion  9 , and that the height h 3  of the projection portion  2  from the substrate  7  is 0.05 to 0.3 time the height h 1 , h 2  of the covering member  29  from the substrate  7 . 
     By fulfilling the above prescribed ranges, it is possible to suppress an excessive increase in the area of contact between the recording medium P and the projection portion  2 , and thereby permit adequate contact of the recording medium P with the projection portion  2 . Accordingly, conveyance of the recording medium P can be effected satisfactorily. Moreover, it is more preferable that the distance between the projection portion  2  and the heat generating portion  9  is 0.4 to 0.6 time the distance between the covering member  29  and the heat generating portion  9 , and that the height h 3  of the projection portion  2  from the substrate  7  is 0.1 to 0.2 time the height h 1 , h 2  of the covering member  29  from the substrate  7 . 
     The distance between the covering member  29  and the heat generating portion  9  refers to a distance between the covering member  29  and the heat generating portion  9  arranged on a straight line extending along the sub scanning direction, and more specifically a distance between a side of the covering member  29  nearest the heat generating portion  9  and a virtual line extending along the main scanning direction while passing through the center of the heat generating portion  9 . 
     For example, the condition of contact of the covering member  29  and the projection portion  2  with the recording medium P can be checked by the following method. To begin with, a coating of paint is applied to the surfaces of the covering member  29  and the projection portion  2 , and then conveyance of the recording medium P is effected. Whether or not the covering member  29  and the projection portion  2  have made contact with the recording medium P can be checked by examining the presence or absence of the paint coating on the surfaces of the covering member  29  and the projection portion  2 . 
     The projection portion  2  is, as exemplified, composed of the convexity  6  and the cover layer  27 , but it is not so limited. For example, the projection portion  2  may be composed solely of the convexity  6  without providing the cover layer  27  over the convexity  6 . In another alternative, the projection portion  2  may be formed by laminating several cover layers  27  one after another. In this case, the projection portion  2  can be composed solely of the cover layer  27 . 
     Next, a thermal printer Z 1  will be described with reference to  FIG. 5 .  FIG. 5  is a view showing the general features of the thermal printer Z 1 , wherein the thermal head X 1  is illustrated as being larger than its actual size. 
     As shown in  FIG. 5 , the thermal printer Z 1  of the present embodiment comprises: the thermal head X 1  thus far described; a conveyance mechanism  40 ; a platen roller  50 ; a power-supply device  60 ; and a control device  70 . The thermal head X 1  is attached to a mounting surface  80   a  of a mounting member  80  disposed in a casing (not shown in the drawing) for the thermal printer Z 1 . 
     The conveyance mechanism  40  comprises: a driving section (not shown); and conveying rollers  43 ,  45 ,  47 , and  49 . The conveyance mechanism  40  is intended to convey the recording medium P such as thermal paper or ink-transferable image-receiving paper in a direction indicated by arrow S shown in the drawing so that the recording medium P can be conveyed onto the protective layer  25  situated on the plurality of heat generating portions  9  of the thermal head X 1 . The driving section has the function of driving the conveying rollers  43 ,  45 ,  47 , and  49 , and, for example, a motor may be used as the driving section. The conveying roller  43 ,  45 ,  47 ,  49  can be constructed of, for example, a cylindrical shaft body  43   a ,  45   a ,  47   a ,  49   a  formed of metal such as stainless steel covered with an elastic member  43   b ,  45   b ,  47   b ,  49   b  formed of butadiene rubber or the like. Although not shown in the drawing, in a case where the recording medium P is ink-transferable image-receiving paper or the like, an ink film is interposed between the recording medium P and the heat generating portion  9  of the thermal head X 1 , and thus the recording medium P and the ink film are conveyed together. 
     The platen roller  50  has the function of pressing the recording medium P onto the protective layer  25  situated on the heat generating portion  9  of the thermal head X 1 . The platen roller  50  is disposed so as to extend along a direction perpendicular to the conveying direction S of the recording medium P, and is fixedly supported at its ends so that it is able to rotate while pressing the recording medium P onto the heat generating portion  9 . For example, the platen roller  50  can be constructed of a cylindrical shaft body  50   a  formed of metal such as stainless steel covered with an elastic member  50   b  formed of butadiene rubber or the like. 
     The power-supply device  60  has the function of supplying electric current for allowing the heat generating portion  9  of the thermal head X 1  to generate heat, as well as electric current for operating the driving IC  11 . The control device  70  has the function of feeding a control signal for controlling the operation of the driving IC  11  to the driving IC  11  in order for the heat generating portions  9  of the thermal head X 1  to generate heat in a selective manner. 
     In the thermal printer Z 1 , as shown in  FIG. 5 , the recording medium P is conveyed onto the heat generating portions  9  of the thermal head X 1  by the conveyance mechanism  40  while being pressed onto the heat generating portions  9  by the platen roller  50 , and, the heat generating portions  9  are caused to generate heat in a selective manner by the power-supply device  60  and the control device  70 , whereby predetermined printing can be performed on the recording medium P. In a case where the recording medium P is image-receiving paper or the like, printing is performed on the recording medium P by effecting thermal transfer of the ink of an ink film (not shown) which is being conveyed together with the recording medium P onto the recording medium P. 
     &lt;Second Embodiment&gt; 
     A thermal head X 2  in accordance with a second embodiment will be described with reference to  FIG. 6 .  FIG. 6  is a plan view showing an electrode pattern of the thermal head. The diagrammatic representations of the protective film, the cover layer, and the connector are omitted, and, the covering member  29  is indicated by alternate long and short dashed lines. In  FIG. 6 , except for a projection portion  102 , the other constituent components are similar to those of the foregoing embodiment, and thus the description thereof will be omitted. In what follows, similar reference characters are used to denote like members. 
     The projection portion  102  comprises a first projection portion  102   a  and a second projection portion  102   b . The first projection portion  102   a  is located at a center of the thermal head X 2  in the main scanning direction, and has the same configuration as that of the projection portion  2  of the thermal head X 1 . The second projection portion  102   b  is located at each end of the thermal head X 2  in the main scanning direction. The second projection portion  102   b  is formed integrally with a thick electrode portion  117   d  provided on a sub wiring portion  17   b.    
     In this construction, printing is performed on the recording medium P in a state of being pressed against the thermal head X 2  by the platen roller  50  (refer to  FIG. 5 ). The platen roller  50  exhibits a greater pressing force at its ends than at other area in the main scanning direction, because the shaft body  50   a  of the platen roller  50  is fixed at its ends in the main scanning direction. Therefore, chances of occurrence of wrinkles in the recording medium P are increased in the second region R 2  located at each end of the thermal head X 2  in the main scanning direction. 
     However, in the thermal head X 2 , The projection portion  102  comprises the first projection portion  102   a  and the second projection portion  102   b . Since the second projection portion  102   b  acts to support the recording medium P so as to restrain the recording medium P against sagging motion, it is possible to decrease the possibility of causing wrinkles in the recording medium P. Moreover, the second projection portion  102   b  also acts to lessen the pressing force of the platen roller  50 , wherefore the pressing force distribution in the main scanning direction can be rendered approximately uniform. 
     The first projection portion  102   a  is placed in a region formed on the substrate  7  by extending the region bearing an array of the heat generating portions  9  in the sub scanning direction S. On the other hand, the second projection portion  102   b  is placed in a region other than the region formed on the substrate  7  by extending the region bearing an array of the heat generating portions  9  in the sub scanning direction S. Therefore, in the main scanning direction, the distance between the second projection portion  102   b  and the heat generating portion  9  is greater than the distance between the first projection portion  102   a  and the heat generating portion  9 . 
     The thermal head X 2  is configured so that a distance Lb between the heat generating portion  9  and the second projection portion  102   b  in the sub scanning direction is shorter than a distance La between the heat generating portion  9  and the first projection portion  102   a  in the sub scanning direction. Accordingly, the second projection portion  102   b  is located close to the heat generating portion  9 , and is therefore able to support the recording medium P which is being carried in the vicinity of the heat generating portion  9 . In this way, the recording medium P can be conveyed smoothly to the heat generating portion  9 . 
     It is preferable that the distance La between the heat generating portion  9  and the first projection portion  102   a  falls in the range of 3 to 5 mm, and that the distance Lb between the heat generating portion  9  and the second projection portion  102   b  falls in the range of 2.5 to 4.5 mm. This makes it possible to support the recording medium P which is being conveyed in the vicinity of the heat generating portion  9 . 
     Moreover, the thermal head X 2  is configured so that a width Wb of the second projection portion  102   b  is greater than a width Wa of the first projection portion  102   a . This makes it possible to increase the area of the second projection portion  102   b  when seen in a plan view which is subjected to a great pressing force exerted by the platen roller  50 . Accordingly, the second projection portion  102   b  is able to lessen the pressing force of the platen roller  50 , wherefore the possibility of causing wrinkles in the recording medium P can be decreased. Note that the width Wb of the second projection portion  102   b  coincides with the length of the second projection portion  102   b  in the main scanning direction, and the width Wa of the first projection portion  102   a  coincides with the length of the first projection portion  102   a  in the main scanning direction. 
     It is preferable that the width Wa falls in the range of 0.5 to 1.5 μm, and that the width Wb falls in the range of 2 to 6 μm. This makes it possible to suppress variations in the condition of conveyance of the recording medium P in the main scanning direction, and thereby decrease the possibility of causing wrinkles in the recording medium P. 
     Moreover, the thermal head X 2  is configured so that the length of the second projection portion  102   b  in the sub scanning direction is greater than the length of the first projection portion  102   a  in the sub scanning direction. This makes it possible to increase the area of the second projection portion  102   b  when seen in a plan view which is subjected to a great pressing force exerted by the platen roller  50 . Accordingly, the second projection portion  102   b  is able to lessen the pressing force of the platen roller  50 , wherefore the possibility of causing wrinkles in the recording medium P can be decreased. 
     It is preferable that the length of the second projection portion  102   b  falls in the range of 1.5 to 2.5 μm, and that the length of the first projection portion  102   a  falls in the range of 0.5 to 1.5 μm. This makes it possible to suppress variations in the condition of conveyance of the recording medium P in the main scanning direction, and thereby decrease the possibility of causing wrinkles in the recording medium P. 
     It is noted that the distance La between the heat generating portion  9  and the first projection portion  102   a  in the sub scanning direction may be shorter than the distance Lb between the heat generating portion  9  and the second projection portion  102   b  in the sub scanning direction. In fact, in the process of forming various electrode patterns, there may be a case where a region capable of placement of the first projection portion  102   a  is smaller than a region capable of placement of the second projection portion  102   b.    
     In this case, the first projection portion  102   a  cannot be made larger than the second projection portion  102   b , wherefore the volume of an Ag paste forming the first projection portion  102   a  is smaller than the volume of an Ag paste forming the second projection portion  102   b.    
     Accordingly, the first projection portion  102   a  is less heat storable than the second projection portion  102   b , and can therefore be placed closer to the heat generating portion  9 . As a result, the first projection portion  102   a  is able to convey the recording medium P smoothly to the heat generating portion  9 . 
     Moreover, in the thermal head X 2 , the width Wa of the first projection portion  2  may be shorter than the width Wb of the second projection portion  2 . In this case, the second projection portion  2  is able to lessen the pressing force of the platen roller  50  effectively, wherefore the possibility of causing wrinkles in the recording medium P can be decreased. 
     &lt;Third Embodiment&gt; 
     A thermal head X 3  in accordance with a third embodiment will be described with reference to  FIG. 7 . 
     When the thermal head X 3  is seen in a plan view, a projection portion  202  has a triangular shape. Moreover, in a plan view, two oblique sides thereof define inclined parts  214 . The projection portion  202  is placed, with its base located on the upstream side in the conveying direction S. That is, the projection portion  202  is so shaped that its area when seen in a plan view becomes narrower gradually toward the downstream side in the conveying direction S. In other words, the projection portion  202  is so shaped that the area of contact with the recording medium P becomes narrower gradually in the same direction. 
     Thus, the projection portion  202  is so shaped that the area of contact with the recording medium P becomes narrower gradually toward the downstream side in the conveying direction S. This makes it possible to lessen a frictional force developed between the recording medium P and the projection portion  202 , and thereby achieve smooth conveyance of the recording medium. 
     In particular, since the projection portion  202  has a triangular shape, and the two oblique sides thereof define the inclined parts  214 , it is possible to achieve a gradual decrease in the area of contact between the recording medium P and the projection portion  202 . Accordingly, the frictional force developed between the recording medium P and the projection portion  202  can be reduced gradually without causing a sharp decrease in the area of contact between the recording medium P and the projection portion  202 . This helps decrease the possibility of occurrence of a sticking phenomenon. 
     It is sufficient that, when the substrate  7  is seen in a plan view, the inclined part  214  is inclined with respect to the sub scanning direction S, and, the angle which the inclined part  214  forms with the conveying direction S preferably falls in the range of 40 to 140°. Moreover, by configuring the projection portion  202  to have a triangular shape when seen in a plan view, it is possible to make efficient use of a space between the IC-IC connection electrodes  26 , and thereby achieve downsizing of the thermal head X 3 . 
     Referring to  FIG. 7( b ) , a modified example of the thermal head X 3  will be described. When the thermal head X 3  is seen in a plan view, a projection portion  302  has a C-shape which is obtained by cutting a small trapezoid from a large trapezoid. The projection portion  302  comprises three sides, namely two oblique sides  314  and one side  315 . A space surrounded by the two oblique sides  314  and the one side  315  is free of the projection portion  302 . 
     The one side  315  is disposed along the main scanning direction, and, the inclined part  314  is located at each end of the one side  315 . The angle which one of the inclined parts  314  forms with the one side  315  and the angle which the other one of the inclined parts  314  forms with the one side  315  are equal to each other. Accordingly, the configuration of the projection portion  302  is line-symmetrical about a centerline of the projection portion  302  in the main scanning direction. 
     The projection portion  302  is configured to support the recording medium P in a manner such that the sagging recording medium P can be upheld gradually from each end in the main scanning direction by the projection portion  302 . Accordingly, as conveyance of the recording medium P proceeds, a central part of the recording medium P in the main scanning direction in a state of sagging down most deeply can be gradually lifted up by the projection portion  302 . This makes it possible to smooth wrinkles while decreasing the possibility of occurrence of a large stress in the recording medium P without rapid elimination of wrinkles. 
     It is possible to dispose the IC-IC connection electrode  26  in the projection portion  302 -free space surrounded by the two oblique sides  314  and the one side  315 . That is, by providing the IC-IC connection electrode  26  in the space surrounded by the two oblique sides  314  and the one side  315 , it is possible to increase the area of the IC-IC connection electrode  26 , and thereby decrease interconnection resistance. 
     &lt;Fourth Embodiment&gt; 
     A thermal head X 4  in accordance with a fourth embodiment will be described with reference to  FIG. 8 . 
     The thermal head X 4  includes a third projection portion  402   a , a fourth projection portion  402   b , and a fifth projection portion  402   c . Moreover, the projection portion  402  is disposed on each of the IC-IC connection electrodes  26  that are electrically independent of each other. 
     In the projection portion  402 , the third projection portion  402   a , the fourth projection portion  402   b , and the fifth projection portion  402   c  are arranged sequentially in the order named from the upstream side in the conveying direction S. In a plan view, the third projection portion  402   a , the fourth projection portion  402   b , and the fifth projection portion  402   c  are rectangular-shaped and have substantially the same size. 
     In the projection portion  402 , the recording medium P is brought into contact with the third projection portion  402   a , the fourth projection portion  402   b , and the fifth projection portion  402   c  one after another in the order named. It is therefore possible to smooth wrinkles gradually from the third projection portion  402   a  toward the fifth projection portion  402   c . Moreover, the third projection portion  402   a , the fourth projection portion  402   b , and the fifth projection portion  402   c  are each disposed on the IC-IC connection electrode  26 , wherefore the current carrying capacity of the IC-IC connection electrode  26  can be increased. 
     Moreover, the recording medium P is brought into contact with the projection portion  402  several times, wherefore a stress developed between the recording medium P and the projection portion  402  can be dispersed. Furthermore, since the third projection portion  402   a , the fourth projection portion  402   b , and the fifth projection portion  402   c  are disposed on their respective different IC-IC connection electrodes  26 , it follows that the third projection portion  402   a , the fourth projection portion  402   b , and the fifth projection portion  402   c  are thermally independent of each other. 
     Accordingly, it is possible to increase the quantity of heat absorbed into the projection portion  402  from the recording medium P when the recording medium P is brought into contact with the projection portion  402 . That is, in the case where the third projection portion  402   a , the fourth projection portion  402   b , and the fifth projection portion  402   c  are disposed on their respective different IC-IC connection electrodes  26 , as compared with a case where the recording medium is brought into contact with the projection portion  402  in a single-piece form, improved heat dissipation capability can be attained. 
     While the thermal head X 3  is, as exemplified, configured so that the third projection portion  402   a , the fourth projection portion  402   b , and the fifth projection portion  402   c  are disposed on their respective different IC-IC connection electrodes  26 , alternatively, the third projection portion  402   a , the fourth projection portion  402   b , and the fifth projection portion  402   c  may be disposed on a single IC-IC connection electrode  26 . Also in this case, the current carrying capacity of the IC-IC connection electrode  26  can be increased. 
     Referring to  FIG. 8( b ) , a modified example of the thermal head X 4  will be described. A projection portion  502  comprises a third projection portion  502   a , a fourth projection portion  502   b , and a fifth projection portion  502   c  that are arranged sequentially in the order named from the upstream side in the conveying direction S. In a plan view, the third projection portion  502   a , the fourth projection portion  502   b , and the fifth projection portion  502   c  are arranged in order of decreasing area. 
     Thus, the thermal head is configured so that the area of contact between the recording medium P and the projection portion  502  becomes smaller gradually from the upstream side in the conveying direction S. In this construction, the third projection portion  502   a  where the recording medium P is most strongly pressed against the projection portion  502 , has the largest area of contact with the recording medium, and, the fourth projection portion  502   b  and the fifth projection portion  502   c  act to disperse a pressing force which diminishes gradually as the recording medium moves forward in the conveying direction S. As a result, the contacting area is adjusted in conformity with the pressing force exerted on the recording medium P, wherefore the recording medium P can be fed smoothly to the heat generating portion  9 . 
     Moreover, in this construction, the fifth projection portion  502   c  has the smallest area of contact with the recording medium P, wherefore the frictional force developed between the fifth projection portion  502   c  and the recording medium P can be kept small. Accordingly, the recording medium P can be separated from the fifth projection portion  502   c  smoothly. 
     &lt;Fifth Embodiment&gt; 
     A thermal head X 5  implemented as the fifth embodiment will be described with reference to  FIGS. 9 and 10 . 
     The thermal head X 5  differs from the thermal heads X 1  to X 4  in that a ground electrode  604  is disposed along the end face  7   a  of the substrate  7  so as to be surrounded by the end face  7   a  of the substrate  7 , an IC-connector connection electrode  521 , the individual electrode  19 , and the IC-IC connection electrode  26 . 
     A convexity  606  is disposed on the ground electrode  604 . A ground electrode  604  disposed below the convexity  606  is electrically connected to the ground electrode  604  extending along the end face  7   a  of the substrate  7  via a coupling electrode  614 . The convexity  606  has a trapezoidal shape when seen in a plan view, and is made of the earlier described Ag paste. Therefore, the convexity  606  has electrical conductivity, and is maintained at a ground potential. 
     The convexity  606  is disposed so as to protrude from the cover layer  27 , and the upper surface of the convexity  606  is left exposed from the cover layer  27 . That is, the projection portion  602  is configured to have the exposed convexity  606 . The recording medium P under conveyance is brought into contact with the upper surface of the convexity  606  left exposed from the cover layer  27 . 
     Thus, even if static electricity is generated in the recording medium P, it is possible to eliminate the static electricity through the projection portion  602  maintained at a ground potential that is contacted by the recording medium P. This makes it possible to decrease the possibility of causing electrostatic damage to the heat generating portion  9  or the recording medium P. 
     Moreover, it is advisable to apply a plating layer formed of Au, Ni, Pd, or the like onto the convexity  606  for suppressing corrosion of the convexity  606 . This helps enhance the corrosion resistance of the convexity  606 . 
     Furthermore, an electrically-conductive protective film (not shown) may be provided on the convexity  606 . In this case, the convexity  606  and the electrically-conductive protective film constitute the projection portion  602 . 
     While several embodiments of the invention have been described heretofore, it should be understood that the application of the invention is not limited to the embodiments thus far described, and that many modifications and variations of the invention are possible within the scope of the invention. For example, the thermal printer Z 1  employing the thermal head X 1  according to the first embodiment has been shown herein, but this does not suggest any limitation, and thus the thermal heads X 2  to X 5  may be adopted for use in the thermal printer Z 1 . Moreover, the thermal heads X 1  to X 5  according to several embodiments may be used in combination. 
     Moreover, the process of printing an Ag paste has been described as a way to form the thick electrode portion  17   d  and the convexity  2  following the formation of various electrodes, but this does not suggest any limitation. For example, it is possible to print an Ag paste in a predetermined position prior to the formation of the electrical resistance layer  15 , and subsequently form the electrical resistance layer  15  and various electrodes. 
     Moreover, in the thermal head X 1 , the protuberant portion  13   b  is formed in the heat storage layer  13 , and the electrical resistance layer  15  is formed on the protuberant portion  13   b , but this does not suggest any limitation. For example, the heat generating portion  9  of the electrical resistance layer  15  may be placed on the underlayer portion  13   b  of the heat storage layer  13  without forming the protuberant portion  13   b  in the heat storage layer  13 . In another alternative, the heat storage layer  13  may be formed over the entire area of the upper surface of the substrate  7 . Also in this case, the protecting member  12  finds its way through the second exposed part  16  to the surface of the heat storage layer  13 , wherefore the strength of adhesion between the substrate  7  and the protecting member  12  can be enhanced. 
     The protecting member  12  and the covering member  29  which covers the driving IC  11  may be formed of the same material. In this case, the covering member  29  and the protecting member  12  can be formed together at one time by performing printing also on the protecting member  12 -forming region during the printing process for forming the covering member  29 . Moreover, while the covering member  29  is, as exemplified, disposed so as to straddle over a plurality of driving ICs  11 , the covering member  29  may be provided for each of the driving ICs on an individual basis. In this case, the difference in height between the first region R 1  and the second region R 2  becomes more noticeable, wherefore it is possible to utilize the invention efficiently. 
     Moreover, while the flat-type head in which the heat generating portion  9  is disposed on the main surface of the substrate  7  has been shown by way of exemplification, the invention is applicable to an edge-type head in which the heat generating portion  9  is disposed on the end face of the substrate  7 . Furthermore, the invention may adopt a turned-back pattern in which adjacent heat generating portions  9  are connected to each other by a turned-back electrode (not shown). 
     Moreover, the driving IC  11  is, as exemplified, flip-chip mounted on the substrate  7 , but this does not suggest any limitation. For example, the driving IC  11  may be disposed on the substrate  7  so as to be electrically connected to various electrodes by means of wire bonding. Moreover, the head substrate  3  may be electrically connected to an external substrate without providing the connector  31 , and thus, also in a case where an external substrate having the driving IC  11  disposed on an upper surface thereof is abutted on the head substrate  3  so that the head substrate  3  and the external substrate can be juxtaposed, and then the driving IC  11  is electrically connected to various electrodes by means of wire bonding, it is possible to utilize the invention efficiently. 
     REFERENCE SIGNS LIST 
     X 1 -X 5 : Thermal head 
     Z 1 : Thermal printer 
     R 1 : First region 
     R 2 : Second region 
       1 : Heatsink 
       2 : Projection portion 
       3 : Head substrate 
       4 : Ground electrode 
       6 : Convexity 
       7 : Substrate 
       8 : Connector pin 
       9 : Heat generating portion 
       10 : Housing 
       11 : Driving IC 
       13 : Heat storage layer 
       15 : Electrical resistance layer 
       17 : Common electrode 
       19 : Individual electrode 
       21 : IC-connector connection electrode 
       23 : Electrically-conductive member 
       25 : Protective layer 
       26 : IC-IC connection electrode (IC connection electrode) 
       27 : Cover layer 
       29 : Covering member