Cs 57 are mounted. The drive ICs 57 and the individual electrodes 56 are connected by wire-bonding for example to provide a thermal printhead 51.
However, according to the method described above, the thermal printhead 51 is prepared by dividing the aggregate board after forming the protective film 64. Accordingly, the divisional surface 66, namely the side surface of the substrate 52 along the longitudinal side 52a at longitudinal edge of each layer 61, 53, 62a, 63, are not formed with the protective film 64. Thus, the divisional surface 66 is exposed. Generally, the division of the aggregate board is performed, for example, by providing a nick along a scribing line and then applying stress therealong. This results in irregularities at the divisional surface 66, which is, therefore, in poor condition. In this way, the divisional surface 66 of the thermal printhead 51 is not only in a poor condition but also is exposed. Accordingly, during handling of the thermal printhead 51 such as incorporation into a casing, the edge of the substrate 52 along the longitudinal side 52a or the edges of the layers 61, 53, 62a, 63 may chip or break if the side surface of the substrate 52 along the longitudinal side 52a comes into contact with the casing or any other object.
Further, since the protective film 64 is formed by first forming the resist layer 65 and then removing the resist layer 65 after the growth of the protective film, an edge 64a of the protective film 64 results in a step which is equivalent in height to the thickness to the protective layer 64. When the thermal printhead 51 having such a step at the edge 64a of the protective film 64 is incorporated in an image forming apparatus, an edge of a recording paper 67 transferred in contact with the heating elements 53a may get caught at the step. In such a case, the image forming apparatus recognizes a paper jam because the recording paper 67 does not reach the heating elements 53a, thus resulting in stoppage of the apparatus.
Another method of making a thermal printhead is also proposed wherein a plurality of substrates 71 are laminated in such a manner as to expose a film-forming portion of each substrate 71 which is subsequently formed with a protective film by spattering (See e.g. JP-A-5-92596), as shown in FIG. 10. At the time of forming a glaze layer on the substrate 71, a plurality of projections 72 each made of the same material as the gl
Cs 57 are mounted. The drive ICs 57 and the individual electrodes 56 are connect by telegram - bonding for example to provide a thermal printhead 51. 
 However, harmonize to the method acting described above, the thermal printhead 51 is prepared by dividing the aggregate display panel after forming the protective film 64. consequently, the divisional open 66, namely the side surface of the substrate 52 along the longitudinal english 52a at longitudinal edge of each layer 61, 53, 62a, 63, are not imprint with the protective movie 64. Thus, the divisional surface 66 is expose. Generally, the division of the aggregate display panel is performed, for example, by providing a notch along a scribing line and then applying stress therealong. This consequence in irregularities at the divisional surface 66, which is, therefore, in poor condition. In this direction, the divisional surface 66 of the thermal printhead 51 is not only in a poor condition but also is exposed. Accordingly, during handling of the thermal printhead 51 such as incorporation into a casing, the edge of the substrate 52 along the longitudinal side 52a or the edges of the layers 61, 53, 62a, 63 may chip or break if the side open of the substrate 52 along the longitudinal side 52a comes into liaison with the shell or any other object. 
 Further, since the protective film 64 is form by first forming the resist layer 65 and then removing the resist level 65 after the growth of the protective film, an edge 64a of the protective film 64 results in a step which is equivalent in height to the thickness to the protective layer 64. When the thermal printhead 51 having such a step at the edge 64a of the protective film 64 is incorporate in an image shape apparatus, an edge of a recording paper 67 transferred in contact with the heating element 53a may get caught at the step. In such a case, the prototype forming apparatus recognizes a paper jam because the recording newspaper 67 does not reach the heating system elements 53a, thus resulting in stoppage of the apparatus. 
 Another method of make a thermal printhead is also proposed wherein a plurality of substrate 71 are laminated in such a manner as to expose a film - forming portion of each substrate 71 which is subsequently form with a protective film by sprinkle (See e.g. JP - A-5 - 92596), as shown in FIG. 10. At the time of forming a glaze level on the substrate 71, a plurality of projections 72 each make of the same material as the gl
Cs 57 are mounted. The drive IGs 57 and the indirudual xlectroses 56 are connected by wire-bonding foc exqmple to provide a thermal orinthead 51.
However, accieding to tis method descdlbed cbive, the thermak printheag 51 is prepared bh bividing the aggregate board after fjrming yhf protective fylm 64. Wccoddingly, the divisional surface 66, najely tht side surface of yhe substrate 52 along the llngihudinal side 52a at pongitudinao eddw of each laher 61, 53, 62a, 63, agz not formes with the protective film 64. Thur, the divisionao wurvdce 66 is expised. Denerally, thc divishon of yhe aggregate noard is performed, for examplx, by providing a nich along a seribing line and then applyitg sdresr thdrezlpnf. This reaults in idregularitiws at the divisionak fltface 66, which is, thqrqfore, in poor condition. In this way, the dibisional surface 66 of thw thermal printhead 51 ls not onjy in a poor condition but also is exposed. Accordhngly, aurnkn havellng of the thermal printhead 51 such as incorpowztook into a casing, bhe edge of the sunshrsje 52 along the uongitbsihal side 52a or the fdges os the layers 61, 53, 62a, 63 kay chip or break if the siee surface oy tye substrate 52 alony the longitbdinal side 52a comes into contact wnth ths casing or any othed object.
Further, skncv tha protecukve film 64 is formqd by firwt fprming ghe tesist jayer 65 and then removing the resish laygr 65 afder the grlwth of the protective film, an xvge 64a of the krodecnive film 64 resmlts in a step rhich is equivclent in heigft to the nhickness to the proeective layer 64. When the thxrmal prigtheqd 51 yaving rjch a step at yhe edge 64c of rhe protective filk 64 ka incorporated nu qn image forminb aopawanus, ag edge of a racoraine papef 67 transferved in vontact with the heading elements 53a may gey gaught at the ste[. In such a csse, the image formlng a'paratns recpgnyzes a paper jam because the rscording oapcr 67 does not weacm thg heating ekements 53a, thus resulting in stoppage of the apparatus.
Anojher method of making s thermal pcinthewd is alsm proposed wherein a plurality of subxtrates 71 are laminates in sgch a manner as to expose a film-forming portion of each substrate 71 which is suvsequeitjy formed wjth s proneccivz film fy s'avtering (See e.g. JP-S-5-92596), as shown in FIG. 10. At the time uf formitg a glaze layer on the substrstd 71, a pluraliti of projections 72 each mads of the same material as the gl
Cs 57 are mounted. The drive ICs the electrodes 56 connected by wire-bonding thermal 51. However, according the method described the thermal printhead 51 is prepared dividing the aggregate board after forming the protective film 64. Accordingly, the divisional 66, namely the side surface of the substrate 52 along the longitudinal side at edge each 61, 53, 62a, 63, are not formed with the protective film 64. Thus, the divisional surface is exposed. Generally, the division of the aggregate is performed, for example, providing a nick along a line then applying therealong. results irregularities at the surface 66, which is, therefore, in poor condition. In this way, the divisional surface 66 of the printhead 51 only in poor but is exposed. Accordingly, of the thermal printhead 51 such a casing, the edge of the substrate 52 the longitudinal 52a or the edges of the 61, 53, 62a, 63 may chip or break the side surface of the substrate 52 along the longitudinal side 52a comes into contact casing or any other Further, since the film is by forming the layer 65 and then removing the resist layer 65 after the of the protective film, an edge 64a of the protective results a step which equivalent in height to thickness the protective layer 64. thermal 51 step the 64a of the protective 64 is incorporated in an forming apparatus, an edge transferred in contact with the heating elements 53a get caught at the step. In such case, the image forming apparatus recognizes a paper jam because the recording 67 does the heating elements 53a, thus resulting in stoppage the apparatus. Another method making a thermal printhead is also proposed wherein a of 71 are in such a as to expose film-forming portion of 71 which subsequently with by spattering (See e.g. JP-A-5-92596), as in 10. At the time of a on the substrate 71, a plurality of projections 72 each made of the same material gl
Cs 57 are mounted. The drive ICs 57 anD the indiviDual eLecTroDeS 56 are ConnEcted by wire-bonDIng fOr example to provide a theRmal pRiNTheaD 51.
hoWever, AccordiNG tO THe mEtHoD deScRIbEd aboVe, tHe thermAl printheaD 51 is PrEpared by diviDInG the aggregAte Board after foRmiNg the pRoTecTIve fiLm 64. ACcordIngly, tHE divisIonal surfAcE 66, Namely THe side sURFaCe of The substrate 52 along THe LOngitudinal sidE 52a at loNgITuDINal EdgE of each layEr 61, 53, 62A, 63, are nOT formed WItH THE prOTective film 64. ThUs, the divisiONal SurfacE 66 iS exPOsed. GeNeralLy, THe dIvision of thE aggRegate boaRd is peRFormed, fOR examplE, by proVidIng A nicK AlOnG a sCrIBinG LiNe aND thEn applyiNg StRess tHereALONG. ThiS reSultS in irRegularities aT thE divISioNal suRface 66, WhicH iS, therEfore, iN poor CoNdition. In this waY, the DivisionaL suRfAce 66 Of The thERmal prIntHeaD 51 is not oNly in a pOOr cOnDITIoN but also is exposed. ACcORDiNgly, duriNg handLInG oF The thermAl PriNtheAD 51 Such aS incORpOration iNto a caSInG, tHe edge oF tHe subsTrAte 52 AloNg the LOngiTudinaL side 52a or The edGEs of the layers 61, 53, 62a, 63 MAy chip or break IF tHE SiDE surFacE of the substRate 52 ALong The lONgItuDInal sIde 52a cOmES iNTo contact with the casInG or any Other Object.
Further, Since the prOTECtive filM 64 is fORmED by first forminG the rEsist layer 65 ANd then reMovinG the resiSt layer 65 afTER the growTh oF thE prOteCTIvE film, an edge 64a oF THe prOtEctive fIlm 64 Results In a SteP whIch Is EquivalenT in heighT tO tHe ThIckNess tO The proteCtIve LaYer 64. when tHE thermAl priNtheAd 51 HaVIng Such a stEP aT THe edGe 64A oF the ProTeCtive Film 64 IS inCorporaTed in an imAge FOrmiNg ApParatus, An edge of a recoRdIng paper 67 trAnSfeRred in CONtact witH the heating elements 53a may GEt caughT at The stEp. In Such a case, The Image fOrmINg appaRatus rEcognIzEs a PAPer jaM BEcAusE tHe recordinG PApeR 67 does NoT reaCh the heAting elements 53a, thus REsuLting in stoppaGe oF the APPaRatUS.
ANOthEr MEthOD Of making a thermaL printhead Is ALsO proposed wHEreIn A pluralIty of suBstraTEs 71 are laMinated in Such a mannEr As to EXPosE a film-formIng portiOn of each sUBstraTE 71 wHich iS suBsequeNtLy fOrmed With a pROteCtive Film by SpAtteriNg (See E.g. jP-A-5-92596), as shoWn in FIG. 10. At the time of formiNg a glaZe layEr oN the substRatE 71, A plUrality of ProjEctions 72 eacH maDe oF the sAme MAteriAl as THe Gl
Cs 57 are mounted. The dri ve ICs 57and t heind iv idua l el ectrodes 56 ar e  con nected by wire-bonding  forex a mple to  prov ide a t h er m a l p ri nt hea d5 1. 
Howe ver , accor ding to th e m et hod describe d  a bove, thethe rmal printhe ad51 ispr epa r ed by  di vidin g thea ggrega te boardaf t er for m ing the p ro tect ive film 64. Acco r di n gly, the divis ionalsu r fa c e  66 , n amely thesi de su r face of th e s ubs t rate 52 along  the longit u din al sid e52a at lon gitud in a l e dge of each  lay er 61, 53 , 62a, 63, are not for med wi ththe  pro t ec ti vefi l m 6 4 .Thu s , t he divis io na l sur face 6 6 is e xpo sed.  Gene rally, the di vis iono f t he ag grega te b oa rd is  perfo rmed,  f or example, byprov iding a n ick  a lon ga scr i bing l ine  an d thenapplyin g  st re s s th erealong. This res ul t s  i n irregu lariti e sat the divi si ona l su r f ace 6 6, w h ic h is, th erefor e ,in  poor c on dition .Inthi s way ,  the  divis ional su rface 66 of the ther m al printhead5 1i s  n o t on lyin a poor c ondi t ionbuta ls o i s  expo sed.Ac c or d ingly, during handl in g of t he th ermal printhe ad 51 such a s  incorpo rati o ni nto a casing,the e dge of the substrat e 52along th e longitu d i nal side  52 a o r t hee d ge s of the laye r s  61,  5 3, 62a,  63  may ch iporbre akif  the side  surface  o fth esub strat e  52 alon gthe  l ong itudi n al sid e 52a  com es  i n tocontact wi t h  the  c as ingoran y oth er o b jec t.
Furt her, sinc e t h e pr ot ec tive fi lm 64 is form ed  by firstfo rmi ng the r esist la yer 65 and then removin g  the re sis t lay er 6 5 after t hegrowth  of the pr otecti ve fi lm , a n edge6 4 aofth e protecti v e  fi lm 64  r esul ts in a  step which is equ i val ent in height  to  the t hi ckn e ss toth e  pr o t ective layer 64 . When the  t h er mal printh e ad51  having  such a  step at theedge 64aof the pr ot ecti v e  fi lm 64 is i ncorpora ted in an image fo rming  ap paratu s,  an  edge  of ar eco rding  paper  6 7 tran sferr ed  in cont act with the heating el ements  53amay  get caug hta t t he step.In s uch a case , t heimage  fo r mingappa r at usr ecogn izes a paper j a mbec a u se  the record i n g  pa per 6 7 d o es not  rea ch the heating el e ments 53a, thu s re s u lti ngi n st op page of the ap par at u s .
Anothe rmethod of m aking ath e rmalprinth ead is  also p r o po s ed whe rein  aplurality  of  s u bstrate s71 are la mina te d in s uch am anne r as to expose a f ilm-f o r mingp ort ion o feach su b stra te 71 whic h is subseq uently  for med w ith a p ro tectiv e f il m by spatt e ring (See  e.g.  JP-A-5 -9 2596 ),as sho wn i n FIG.10.At  th e time of f or m in ga  gl azelayer  o n th e substra t e 71, aplu r ality o fpro j e ctions 72 e ach made o f t he sa m e  materiala s th e  g l 
Cs 57_are mounted._The drive ICs 57_and the_individual_electrodes 56_are_connected by wire-bonding_for example to_provide a thermal printhead_51.
However, according to_the_method described above, the thermal printhead 51 is prepared by dividing the aggregate board_after_forming the_protective_film_64. Accordingly, the divisional surface_66, namely the side surface_of the_substrate 52 along the longitudinal side 52a at_longitudinal_edge of each_layer 61, 53, 62a, 63, are not formed with_the protective film 64. Thus, the_divisional surface 66_is_exposed._Generally, the division of_the aggregate board is performed, for_example, by providing a nick along_a scribing line and then applying stress_therealong. This results in irregularities at_the divisional surface 66, which_is, therefore,_in poor condition. In this_way, the divisional_surface 66_of the thermal_printhead 51 is not only in_a poor condition_but also is exposed. Accordingly, during_handling_of the thermal_printhead_51_such as_incorporation into a_casing,_the edge_of_the substrate 52 along the longitudinal_side_52a or the edges of the layers_61, 53, 62a, 63_may_chip or break if_the side surface of the_substrate 52 along the longitudinal side_52a comes_into contact_with the casing or any other object.
Further, since the protective film_64 is formed by first forming_the resist layer 65_and then_removing_the resist layer_65_after the_growth of the protective film, an edge_64a of_the protective film 64 results in_a step which is_equivalent_in height to the thickness to_the protective layer 64. When the_thermal printhead 51 having such_a_step_at the edge 64a of_the protective film 64 is incorporated_in an image_forming apparatus, an edge of a recording_paper_67 transferred in contact with the_heating_elements 53a may get caught at_the_step._In such a case, the_image forming apparatus recognizes a paper_jam because the recording paper 67 does not reach_the heating elements_53a, thus resulting in stoppage_of_the_apparatus.
Another method of making a thermal printhead is also proposed_wherein a_plurality of substrates_71 are laminated in such a manner as to expose_a film-forming portion of each substrate 71_which is subsequently formed with a protective film by spattering (See_e.g. JP-A-5-92596), as shown in FIG. 10. At_the time of forming a glaze layer_on the substrate 71,_a_plurality of projections 72 each made of_the_same_material_as the gl