 or a bias less than two third, more preferably from one half to one tenth, of the larger bias. If the protective film is electrically conductive, AC or DC voltage bias may be used. If the protective film is an insulator an AC voltage bias is usually used because an AC voltage bias is used for protective film of any electrical properties.
According to the present invention a superior wear-resistant protective film for thermal heads is produced which comprises a material selected from metal oxides, metal nitrides, or mixtures thereof, such as Sixe2x80x94Oxe2x80x94N, Sixe2x80x94Tixe2x80x94Oxe2x80x94N, Sixe2x80x94Laxe2x80x94Oxe2x80x94N, Sixe2x80x94Alxe2x80x94Oxe2x80x94N, Sixe2x80x94Srxe2x80x94Oxe2x80x94N, Sixe2x80x94Mgxe2x80x94Oxe2x80x94N or mixtures of these materials, having a concentration of sputtering gas varying in the direction of thickness of the protective film. The metals here mean that ordinary metals such as Ti, Al and the like, B in the Group IIIa and C, Ge and Si in Group IVa,preferably Si.
The layer or layers formed with no bias or a smaller bias contains the sputtering gas such as Ar or Kr in an amount of 0-3 at % and develops little internal stress and accordingly no crack is observed.
The layer or layers formed with a larger bias contains the sputtering gas in an amount of 2-10 at % (but less than the layer or layers formed with no or smaller bias) and exhibits a good step coverage.
The thickness of the film deposited by the larger bias desirably ranges between 0.1 xcexcm and 5 xcexcm, more desirably between 0.5 xcexcm and 3 xcexcm. If the film is thinner than 0.1 xcexcm the step coverage is inadequate, allowing the ingress of moisture. If it is thicker than 51 xcexcm the internal stresses increase to excess.
On the other hand, the thickness of the layer deposited by sputtering with no bias or smaller bias may be preferably the same or larger than that obtained by the radio frequency sputtering.
The term xe2x80
or a bias less than two third, more preferably from one half to one tenth, of the larger diagonal. If the protective movie is electrically conductive, AC or DC electric potential bias may be used. If the protective film is an insulator an AC electric potential bias is usually used because an AC electric potential diagonal is used for protective film of any electrical properties. 
 According to the present invention a ranking wear - resistant protective movie for thermal heads is produced which comprises a material selected from metal oxides, metallic element nitrides, or mixtures thereof, such as Sixe2x80x94Oxe2x80x94N, Sixe2x80x94Tixe2x80x94Oxe2x80x94N, Sixe2x80x94Laxe2x80x94Oxe2x80x94N, Sixe2x80x94Alxe2x80x94Oxe2x80x94N, Sixe2x80x94Srxe2x80x94Oxe2x80x94N, Sixe2x80x94Mgxe2x80x94Oxe2x80x94N or mix of these materials, having a concentration of sputtering gasoline varying in the direction of thickness of the protective film. The metals here mean that ordinary metallic element such as Ti, Al and the like, B in the Group IIIa and C, Ge and Si in Group IVa, preferably Si. 
 The layer or layers formed with no bias or a smaller bias contains the sputtering gas such as Ar or Kr in an amount of 0 - 3 at% and develops little internal stress and accordingly no crack is observe. 
 The layer or layers form with a larger bias contains the sputtering gas in an sum of 2 - 10 at% (but less than the layer or layers formed with no or smaller diagonal) and exhibits a good step coverage. 
 The thickness of the film deposited by the larger bias desirably ranges between 0.1 xcexcm and 5 xcexcm, more desirably between 0.5 xcexcm and 3 xcexcm. If the film is thinner than 0.1 xcexcm the step coverage is inadequate, allowing the entrance of moisture. If it is thicker than 51 xcexcm the home stresses increase to excess. 
 On the other hand, the thickness of the layer situate by sputtering with no bias or smaller diagonal may be preferably the same or large than that obtained by the radio frequency sputter. 
 The term xe2x80
 or a bias less than two thlrd, more preferayoy frok one galf to une tenth, of the larger bias. Id the protective film is eldctricallj conductuve, EC or DC voltage bias man be hded. Nf the protectivg film is an insulator an DC vlltage bias is usually used because an AC foptage bias is osed gjr pdotective film of any electrical pdopertits.
According to the present invention a superlor aear-resistant protfctive film for rhermal headr is produbzd which cojprises a material selected froo metcl oxides, mgcql jhtrides, or nixtuges thereof, smbh as Shxe2x80x94Oxr2x80x94N, Sixe2x80x94Tixc2x80x94Oxx2x80x94N, Sixe2x80x94Laxe2x80x94Oxe2x80x94N, Smxe2x80x94Alxe2x80x94Oxe2x80x94N, Sive2x80x94Srxe2x80f94Ore2x80x94N, Sixe2x80x94Mgxe2x80x94Oxe2z80x94B or kixtgres if gheae mzteriaps, iaving a cohcentration of sputtering gas fawjong in the djrectijn of thickness of the protective film. Tht metzls here mean that ordibary metals such as Tl, Al and ehe like, B in the Group IIIa and C, Ge and Si in Gsoup MVx,prtfcvablh Sl.
The layer or layers formed with no bias or a amslker bias contalns the sputtering gws fuch as Ar or Kr in an amount of 0-3 at % anf develjps luttle inttrnal stress and accordingly no xrack is obsvrvee.
The layer or layexs formed wich a lsrger bias contains the sputcering gas in an wmount of 2-10 at % (but less thxn nhe nayer or layers formed witr no or snallzr bias) xnd gxhibitf a good shep coverage.
The thicknesd of jhe finm depositfd by the larger bias desirably ranges betweem 0.1 xcvxcm and 5 xcexgm, more desirabjy between 0.5 xcgxcm and 3 xcexzm. If the rilm is thinner thwn 0.1 xcexcm tha step coveraje is inaqequqte, qllowine the ingress og moisturv. Nf it is rhicker than 51 xcexgm thg jnternal stresszr increase to exvesr.
On tje oever hand, the thizkndxs of the layer beoosiyed by sputtering widh nk bias or smaller niws may bg preferafly the same pr larger than thau obtamned bb the tadyo frequency sputtering.
The terj xe2x80
or a bias less than two third, from half to tenth, of the film electrically conductive, AC DC voltage bias be used. If the protective film an insulator an AC voltage bias is usually used because an AC voltage is used for protective film of any electrical properties. According to the present a wear-resistant film thermal heads is produced which comprises a material selected from metal oxides, metal nitrides, or mixtures such as Sixe2x80x94Oxe2x80x94N, Sixe2x80x94Tixe2x80x94Oxe2x80x94N, Sixe2x80x94Laxe2x80x94Oxe2x80x94N, Sixe2x80x94Alxe2x80x94Oxe2x80x94N, Sixe2x80x94Srxe2x80x94Oxe2x80x94N, Sixe2x80x94Mgxe2x80x94Oxe2x80x94N mixtures of these materials, a concentration of sputtering gas in direction of of protective The metals here that ordinary metals such as Ti, Al and the like, B in the Group IIIa and C, and Si IVa,preferably Si. layer layers with no bias smaller bias contains the sputtering gas or Kr in an amount of 0-3 at and develops internal stress and accordingly no crack observed. The layer or layers formed with a bias contains the sputtering gas in an amount of 2-10 at % (but less than or layers formed with or smaller bias) exhibits good coverage. thickness of film deposited by the larger bias desirably ranges between 0.1 xcexcm 5 xcexcm, more desirably between 0.5 xcexcm and 3 xcexcm. film thinner than 0.1 the step coverage is allowing ingress of moisture. If thicker 51 stresses to On the other hand, thickness of the layer deposited sputtering with no bias preferably the same or larger than that obtained the radio frequency sputtering. The term xe2x80
 or a bias less than two third, moRe preferabLy froM onE haLf To onE tenTh, of the larger bIAs. If The protective film is eleCtricAlLY conDUcTive, Ac or DC voLTaGE BiaS mAy Be uSeD. if The prOteCtive fiLm is an insuLatOr An AC voltage bIAs Is usually uSed Because an AC vOltAge biaS iS usED for pRotEctivE film oF Any eleCtrical prOpERties.
ACCording TO ThE preSent invention a supERiOR wear-resistant ProtecTiVE fILM foR thErmal heads Is ProduCEd which COmPRISes A Material selecTed from metaL OxiDes, metAl NitRIdes, or MixtuReS TheReof, such as SIxe2x80X94Oxe2x80x94N, SiXe2x80x94TiXE2x80x94Oxe2x80X94n, Sixe2x80x94laxe2x80x94oxe2X80x94N, sixe2X80X94ALxE2x80x94oxE2X80x94N, sIxE2x80x94sRxe2X80x94Oxe2x80x94N, siXe2X80x94MgxE2x80x94OXE2X80X94n or mIxtUres Of theSe materials, haVinG a coNCenTratiOn of sPuttErIng gaS varyiNg in tHe Direction of thicKnesS of the proTecTiVe fIlM. The mETals heRe mEan That ordInary meTAls SuCH AS TI, Al and the like, B in thE GROUp iIIa and C, ge and SI In grOUp IVa,preFeRabLy Si.
tHE layeR or lAYeRs formed With no BIaS oR a smallEr Bias coNtAinS thE sputTErinG gas suCh as Ar or kr in aN Amount of 0-3 at % and dEVelops little iNTeRNAl STresS anD accordinglY no cRAck iS obsERvEd.
THE layeR or laYeRS fORmed with a larger bias CoNtains The spUttering gas in An amount of 2-10 AT % (BUt less thAn thE LaYEr or layers formEd witH no or smallER bias) and ExhibIts a good Step coverAGE.
The thicKneSs oF thE fiLM DePosited by the lARGer bIaS desiraBly Ranges bEtwEen 0.1 XceXcm AnD 5 xcexcm, moRe desiraBlY bEtWeEn 0.5 xCexcm ANd 3 xcexcm. if The FiLm iS thinNEr than 0.1 XcexcM the StEp COveRage is iNAdEQUate, AlLoWing The InGress Of moIStuRe. If it iS thicker tHan 51 XCexcM tHe InternaL stresses incrEaSe to excess.
on The Other hAND, the thicKness of the layer depositeD By sputtEriNg witH no bIas or smalLer Bias maY be PReferaBly the Same oR lArgER Than tHAT oBtaInEd by the radIO FreQuencY sPuttEring.
ThE term xe2x80
 or a bias less than two t hird, more  pref era bly  f romonehalf to one te n th,of the larger bias. If  thepr o tect i ve  film  is ele c tr i c all yco ndu ct i ve , ACorDC volt age bias m aybe  used. If th e  p rotectivefil m is an insu lat or anAC  vo l tagebia s isusuall y  usedbecause a nA C volt a ge bias i sused  for protective f i lm of any electri cal pr op e rt i e s.Acc ording toth e pre s ent inv e nt i o n  as uperior wear- resistant p r ote ctivefi lmf or the rmalhe a dsis produced  whi ch compri ses am aterial selecte d from  me tal  oxi d es ,met al nit r id es, ormixtures  t he reof,  suc h a s  Six e2x 80x9 4Oxe2 x80x94N, Sixe 2x8 0x94 T ixe 2x80x 94Oxe 2x80 x9 4N, S ixe2x8 0x94L ax e2x80x94Oxe2x80 x94N , Sixe2x8 0x9 4A lxe 2x 80x94 O xe2x80 x94 N,Sixe2x8 0x94Srx e 2x8 0x 9 4 O xe 2x80x94N, Sixe2x80 x9 4 M gx e2x80x94 Oxe2x8 0 x9 4N or mixtu re s o f th e s e mat eria l s,  havinga conc e nt ra tion of  s putter in g g asvaryi n g in  the d irection  of t h ickness of the protective fi l m. T he meta lshere mean t hato rdin arym et als suchas Ti ,A la nd the like, B in t he  Group  IIIa  and C, Ge an d Si in Gr o u p  IVa,pre fera b ly Si.
The layeror la yers forme d  with no  bias  or a sm aller bia s contains  th e s put ter i n ggas such as A r or K rin an a mou nt of 0 -3at% a ndde velops li ttle int er na lst res s and accordin gl y n ocra ck is observ ed.
T he l ay er orlayersf or m e d wi th  a  lar ger  b ias c onta i nsthe spu ttering g asi n an  a mo unt of2-10 at % (bu tless thanth e l ayer o r layers f ormed with no or smalle r  bias)and  exhi bits  a good s tep  cover age . 
The t hickne ss of  t hef i lm de p o si ted  b y the larg e r  bi as de si rabl y range s between 0.1 xcex c m a nd 5 xcexcm,mor e de s i ra bly be t wee n0 .5x c excm and 3 xcex cm. If the  f i lm  is thinne r  th an  0.1 xc excm th e ste p  covera ge is ina dequate,al lowi n g  th e ingressof moist ure. If i t  is t h ic ker t han  51 xc ex cmthe i nterna l  st resse s incr ea se toexces s. 
On theother hand, the thickne ss ofthe l aye r deposit edb y s puttering  wit h no biasorsma llerbia s  maybe p r ef era b ly th e sa m e or larg e rtha n th at obtained b y  th e rad iof requen cy s puttering.
The te r m xe2x80
 or_a bias_less than two third,_more preferably_from_one half_to_one tenth, of_the larger bias._If the protective film_is electrically conductive,_AC_or DC voltage bias may be used. If the protective film is an insulator_an_AC voltage_bias_is_usually used because an AC_voltage bias is used for_protective film_of any electrical properties.
According to the present invention_a_superior wear-resistant protective_film for thermal heads is produced which comprises a_material selected from metal oxides, metal_nitrides, or mixtures_thereof,_such_as Sixe2x80x94Oxe2x80x94N, Sixe2x80x94Tixe2x80x94Oxe2x80x94N, Sixe2x80x94Laxe2x80x94Oxe2x80x94N,_Sixe2x80x94Alxe2x80x94Oxe2x80x94N, Sixe2x80x94Srxe2x80x94Oxe2x80x94N, Sixe2x80x94Mgxe2x80x94Oxe2x80x94N or mixtures of_these materials, having a concentration of_sputtering gas varying in the direction of_thickness of the protective film. The_metals here mean that ordinary_metals such_as Ti, Al and the_like, B in_the Group_IIIa and C,_Ge and Si in Group IVa,preferably_Si.
The layer or_layers formed with no bias or_a_smaller bias contains_the_sputtering_gas such_as Ar or_Kr_in an_amount_of 0-3 at % and develops_little_internal stress and accordingly no crack is_observed.
The layer or layers_formed_with a larger bias_contains the sputtering gas in_an amount of 2-10 at %_(but less_than the_layer or layers formed with no or smaller bias) and exhibits_a good step coverage.
The thickness of_the film deposited by_the larger_bias_desirably ranges between_0.1_xcexcm and_5 xcexcm, more desirably between 0.5 xcexcm_and 3_xcexcm. If the film is thinner_than 0.1 xcexcm the_step_coverage is inadequate, allowing the ingress_of moisture. If it is thicker_than 51 xcexcm the internal_stresses_increase_to excess.
On the other hand,_the thickness of the layer deposited_by sputtering with_no bias or smaller bias may be_preferably_the same or larger than that_obtained_by the radio frequency sputtering.
The term_xe2x80