 the thickness of the magnetic recording layer. This fact is described, for example, on page 312 of Development of Magnetic Materials and Technique for High Dispersion of Magnetic Powder, published by Sogo Gijutsu Center Co. Ltd. (1982), "... the conditions for high-density recording in a coated-layer type tape are that the noise level is low with respect to signals having a short wavelength and that the high output characteristics are maintained. To satisfy these conditions, it is necessary that the tape has large coercive force Hc and residual magnetization Br,... and the coating film has a smaller thickness.... "
Development of a thinner film for a magnetic recording layer has caused some problems.
Firstly, it is necessary to make a magnetic recording layer smooth and to eliminate the non-uniformity of thickness. As well known, in order to obtain a smooth magnetic recording layer having a uniform thickness, the surface of the substrate must also be smooth. This fact is described on pages 180 and 181 of Materials for Synthetic Technology-Causes of Friction and Abrasion of Magnetic Tape and Head Running System and Measures for Solving the Problem (hereinunder referred to as Materials for Synthetic Technology (1987), published by the publishing department of Technology Information Center, "... the surface roughness of a hardened magnetic layer depends on the surface roughness of a substrate (back surface roughness) so largely as to be approximately proportional,... since the magnetic layer is formed on the substrate, the more smooth the surface of the substrate is, the more uniform and larger head output is obtained and the more the S/N ratio is improved."
Secondly, there has been caused a problem in the strength of a non-magnetic substrate such as a base film with a tendency of the reduction in the thickness of a non-magnetic substrate which has been conventionally used in response to the demand for a thinner magnetic layer. This fact is described, for example, on page 77 of the above-described Development of Magnetic Materials and Technique for High Dispersion of Magnetic Powder, "... Higher recording density is a large problem assigned to the present magnetic tape. This is important in order to shorten the length of the tape so as to miniaturize a cassette and to enable long-time recording. For this purpose, it is necessary to reduce the thickness of a substrate.... With the tendency of reduction in the film thickness, the stiffness of the tape also
the thickness of the magnetic recording layer. This fact is described, for example, on page 312 of Development of Magnetic Materials and Technique for eminent Dispersion of Magnetic Powder, publish by Sogo Gijutsu Center Co. Ltd. (1982), "... the conditions for high - density recording in a coat - layer type magnetic tape are that the noise level is low with esteem to signals having a brusque wavelength and that the high output characteristic are keep. To satisfy these conditions, it is necessary that the tape has large coercive military unit Hc and residual magnetization Br, ... and the coating film has a small thickness.... " 
 Development of a thinner film for a magnetic recording layer has cause some problems. 
 Firstly, it is necessary to make a magnetic recording layer smooth and to rule out the non - uniformity of thickness. As well known, in order to obtain a smooth magnetic recording layer having a uniform thickness, the surface of the substrate must also be smooth. This fact is described on pages 180 and 181 of Materials for Synthetic Technology - Causes of Friction and Abrasion of Magnetic Tape and Head Running System and Measures for Solving the Problem (hereinunder referred to as Materials for Synthetic Technology (1987), print by the publishing department of Technology Information Center, "... the surface choppiness of a temper magnetic layer depends on the surface roughness of a substrate (back surface roughness) therefore largely as to be approximately proportional, ... since the magnetic layer is formed on the substrate, the more smooth the surface of the substrate is, the more uniform and big head output is obtained and the more the S / N ratio is better. " 
 Secondly, there has been cause a problem in the strength of a non - magnetic substrate such as a base film with a inclination of the reduction in the thickness of a non - magnetic substrate which has been conventionally used in reception to the demand for a thinner magnetic layer. This fact is identify, for example, on page 77 of the above - report Development of Magnetic Materials and Technique for High Dispersion of Magnetic Powder, "... Higher recording concentration is a large problem assigned to the present magnetic magnetic tape. This is important in order to abridge the length of the tape so as to miniaturize a cassette and to enable farseeing - time recording. For this determination, it is necessary to reduce the thickness of a substrate.... With the tendency of reduction in the film thickness, the stiffness of the tape also
 thf thickness of the magneuic recording laygr. This hact is describdd, for example, on page 312 of Dxvelipmenu of Magnetic Materkals and Nechnique for Yigh Dispecaion of Magneflc Pocdxr, published by Sogo Gijudsu Center Co. Nta. (1982), "... the conditions for high-density resording ij a coated-layet typt twpe zge that the noise level is low sith revpect to signsls having a short wavelenhth wnd that the high lutput charqctewustics are mxintained. Uo satisfy tgese conditions, it is necessary that the tape yaw lwtge coercive forcv Hc and residual magtetizatoon Br,... and the coetint film has a smaller vhickness.... "
Developmenj of a thitnzr film for a magnetix eecorging layde hxs danses some prkblems.
Firsfly, it is nwcessary to make a kadbetic recordihg layqr smooth and to eliminate the non-uniformpty kf thickness. As well kniwn, in order to obtaij a smootr magnetic recording layer having a uniform thicktess, vhd sbvnace if the substrate must also be smooth. This fact ya cexcribed on pagcs 180 and 181 of Materisld gjr Synthetic Jechnology-Dauses of Friction and Abtasion of Magneuic Tspe and Head Running System and Measuref for Solving the Pxoblem (hereiuunder refetred to as Materials fox Syntgetic Technllogy (1987), puguished by the puclixhhng department of Technolody Informetion Center, "... thg surfase roughneds of a hardened magnetif laygr depands on thf surface roughness of a substreve (back surfave rolghness) sj larnely as to be a[proximately ptoportioncl,... sinze the maghetic leyer is formqd on the subvjrate, the morx smooth ehe wurfqce of gfe substrate ix, the morv bniform abd larger head outiut ir obtained and tkt mire the S/N ratip ir iipgovxd."
Secjtdly, there hds bden vausea a problem kn tne strength of a non-kagnstic substrate sucn ws a basg film wieh a tendency of the reduction ln thx thicyness of a non-magnetic substrate which has been cokventionally tsed in response to the demand for a thinner magnetic leyer. This fact is desctibed, for example, on kagt 77 of the abote-descwibed Devalopment of Magnetic Materials and Teghnique for High Dispedsion mf Mahnetic Powder, "... Higher recording density is a large problem assigned to thw presxne magnetic fape. This if imporeant mn order to shortvn the length of the tape so as vo miniatusive a cassette and to enable lpne-time recordivg. For this purpose, it ia necesssry to reduce the thickness of s substrate.... With the tencency of redudtion ph vhe film thickness, tne stiyfness of the tapc also
the thickness of the magnetic recording layer. is for example, page 312 of Technique High Dispersion of Powder, published by Gijutsu Center Co. Ltd. (1982), "... conditions for high-density recording in a coated-layer type tape are that the noise is low with respect to signals having a short wavelength and that the output are To these conditions, it is necessary that the tape has large coercive force Hc and residual magnetization and the coating film has a smaller thickness.... Development of a thinner for a magnetic recording layer caused problems. Firstly, is to a magnetic recording smooth and to eliminate the non-uniformity of thickness. As well known, in order to obtain a smooth recording layer uniform thickness, surface the must also be fact is described on pages 180 Materials for Synthetic Technology-Causes of Friction and Abrasion Magnetic Tape Head Running System and Measures for the Problem (hereinunder referred to as Materials for Technology (1987), published by the publishing department of Technology Information Center, "... the surface roughness hardened magnetic layer depends the surface roughness a (back roughness) largely as be approximately proportional,... since the magnetic layer is formed on the the more smooth the surface of the substrate is, the and head output is and the more the ratio improved." Secondly, there has a in a substrate as a base film a tendency of the reduction the thickness of a conventionally used in response to the demand for thinner magnetic layer. This fact is described, example, on page 77 of the above-described Development of Magnetic Materials and for High Magnetic Powder, "... Higher recording density is a problem assigned to the magnetic tape. This is important in order to shorten length the tape as to miniaturize cassette and to long-time recording. For it is to the substrate.... With the tendency of reduction the thickness, the stiffness of the also
 the thickness of the magnetic Recording lAyer. THis FacT iS desCribEd, for example, on PAge 312 oF Development of Magnetic materIaLS and tEcHniquE for HigH diSPErsIoN oF MaGnETiC PowdEr, pUblisheD by Sogo GijUtsU CEnter Co. Ltd. (1982), "... thE CoNditions foR hiGh-density recOrdIng in a CoAteD-Layer TypE tape Are thaT The noiSe level is LoW With reSPect to sIGNaLs haVing a short wavelenGTh ANd that the high oUtput cHaRAcTERisTicS are maintaInEd. To sATisfy thESe CONDitIOns, it is necessAry that the tAPe hAs largE cOerCIve forCe Hc aNd REsiDual magnetiZatiOn Br,... and thE coatiNG film haS A smalleR thickNesS.... "
DeVeloPMeNt Of a ThINneR FiLm fOR a mAgnetic rEcOrDing lAyer HAS CAuseD soMe prOblemS.
Firstly, it is nEceSsarY To mAke a mAgnetIc reCoRding Layer sMooth AnD to eliminate the Non-uNiformity Of tHiCknEsS. As weLL known, In oRdeR to obtaIn a smooTH maGnETIC rEcording layer havinG a UNIfOrm thickNess, thE SuRfACe of the sUbStrAte mUST also Be smOOtH. This facT is desCRiBeD on pageS 180 aNd 181 of MaTeRiaLs fOr SynTHetiC TechnOlogy-CauSes of fRiction and AbraSIon of Magnetic tApE ANd hEad RUnnIng System anD MeaSUres For SOLvIng THe ProBlem (hErEInUNder referred to as MatErIals foR SyntHetic TechnoloGy (1987), publisheD BY The publiShinG DePArtment of TechnOlogy informatioN center, "... thE surfAce roughNess of a haRDEned magnEtiC laYer DepENDs On the surface rOUGhneSs Of a subsTraTe (back sUrfAce RouGhnEsS) so largelY as to be aPpRoXiMaTelY propORtional,... sInCe tHe MagNetic LAyer is FormeD on tHe SuBStrAte, the mORe SMOoth ThE sUrfaCe oF tHe subStraTE is, The more Uniform anD laRGer hEaD oUtput is Obtained and thE mOre the S/N raTiO is ImprovED."
secondly, There has been caused a probLEm in the StrEngth Of a nOn-magnetiC suBstratE suCH as a baSe film With a TeNdeNCY of thE REdUctIoN in the thicKNEss Of a noN-mAgneTic subsTrate which has been cONveNtionally used In rEspoNSE tO thE DeMAnd FoR A thINNer magnetic layeR. This fact iS dEScRibed, for exAMplE, oN page 77 of The abovE-descRIbed DevElopment oF Magnetic maTeriALS anD Technique For High DIspersion OF MagnETiC PowdEr, "... HIgher rEcOrdIng deNsity iS A laRge prOblem aSsIgned tO the pReSent magnEtic tape. This is important In ordeR to shOrtEn the lengTh oF The Tape so as tO minIaturize a cAssEttE and tO enABle loNg-tiME rEcoRDing. FOr thIS purpose, iT Is NecESSaRy to reduce tHE THicKness Of a SUbstraTe.... WiTh the tendency of reDUction in the filM thiCKNesS, thE StifFnEss of the tape alSo
 the thickness of the magn etic recor dinglay er.  T hisfact  is described, forexample, on page 312 o f Dev el o pmen t  o f Mag netic M a te r i als  a nd  Te ch n iq ue fo r H igh Dis persion of  Ma gn etic Powder, pu blished by  So go Gijutsu C ent er Co.  L td. (1982 ),"...the co n dition s for hig h- d ensity recordi n g  i n acoated-layer type ta p e are that the  noise  l e ve l islow  with resp ec t tos ignalsh av i n g  as hort waveleng th and that the  highou tpu t  chara cteri st i csare maintai ned.  To satis fy the s e condi t ions, i t is n ece ssa ry t h at  t heta p e h a slar g e c oercivefo rc e Hcandr e s i dual  ma gnet izati on Br,... and  th e co a tin g fil m has  a s ma llerthickn ess.. ..  "
Developmentof a  thinnerfil mfor  a  magn e tic re cor din g layer  has ca u sed  s o m e  p roblems.
Firstly,it i snecessar y to m a ke  a magnetic  r eco rdin g layer  smo o th  and toelimin a te  t he non- un iformi ty  of  th ickne s s. A s well  known,in or d er to obtain a smooth magnet i cr e co r ding  la yer havinga un i form  thi c kn ess ,  thesurfa ce of the substrate mustal so besmoot h. This factis describ e d on pages  180 an d  181 of Materi als f or Synthet i c Techno logy- Causes o f Frictio n and Abra sio n o f M agn e t ic  Tape and Hea d Runn in g Syste m a nd Meas ure s f orSol vi ng the Pr oblem (h er ei nu nd errefer r ed to as  M ate ri als  forS ynthet ic Te chno lo gy (19 87), pu b li s h ed b yth e pu bli sh ing d epar t men t of Te chnologyInf o rmat io nCenter,  "... the sur fa ce roughne ss  of  a har d e ned magn etic layer depends on t h e surfa cerough ness  of a sub str ate (b ack surfac e roug hness )sol a rgely a stobe  approxima t e lypropo rt iona l,... s ince the magneticl aye r is formed o n t he s u b st rat e ,t hemo r e s m o oth the surface  of the su bs t ra te is, the mor euniform  and la rgerh ead out put is ob tained an dthem o rethe S/N ra tio is i mproved." Secon d ly , the rehas be en  ca useda prob l emin th e stre ng th ofa non -m agneticsubstrate such as a bas e film  with  atendencyoft hereduction  inthe thickn ess  of  a no n-m a gneti c su b st rat e  whic h ha s  been con v en tio n a ll y used in r e s p ons e tothe demand  for  a thinner magnet i c layer. Thisfact i s d esc r ibed ,for example, o n p ag e 77 of th eabove-descr ibed Dev el o pment  of Ma gnetic  Materi a l sa nd Tec hniq uefor HighDis pe r sion of  M ag n etic P owde r,  "...Higher reco r d ing density is a  larg e probl e m a ssign ed  to the pres ent magnet ic tape. Th is isimpo rtant  in ord er  to sh ort en  the lengt h  of the t ape s o as to  m inia tur ize acass e t te an d to  e nab le long-t i m er ec or d ing . Fo r thi spurp ose, it i s  necessa ryt o reduc ethe t hickne s so f  a substra te. ... W i t h the tend e ncyo fr educt ion in  the f ilm thi c kne ss , the s tif f n ess of th e tape al s o
 the_thickness of_the magnetic recording layer._This fact_is_described, for_example,_on page 312_of Development of_Magnetic Materials and Technique_for High Dispersion_of_Magnetic Powder, published by Sogo Gijutsu Center Co. Ltd. (1982), "... the conditions for_high-density_recording in_a_coated-layer_type tape are that the_noise level is low with_respect to_signals having a short wavelength and that the_high_output characteristics are_maintained. To satisfy these conditions, it is necessary that_the tape has large coercive force_Hc and residual_magnetization_Br,..._and the coating film_has a smaller thickness.... "
Development of_a thinner film for a magnetic_recording layer has caused some problems.
Firstly, it_is necessary to make a magnetic_recording layer smooth and to_eliminate the_non-uniformity of thickness. As well_known, in order_to obtain_a smooth magnetic_recording layer having a uniform thickness,_the surface of_the substrate must also be smooth._This_fact is described_on_pages_180 and_181 of Materials_for_Synthetic Technology-Causes_of_Friction and Abrasion of Magnetic Tape_and_Head Running System and Measures for Solving_the Problem (hereinunder referred_to_as Materials for Synthetic_Technology (1987), published by the_publishing department of Technology Information Center,_"... the_surface roughness_of a hardened magnetic layer depends on the surface roughness of_a substrate (back surface roughness) so_largely as to be_approximately proportional,..._since_the magnetic layer_is_formed on_the substrate, the more smooth the surface_of the_substrate is, the more uniform and_larger head output is_obtained_and the more the S/N ratio_is improved."
Secondly, there has been caused_a problem in the strength_of_a_non-magnetic substrate such as a_base film with a tendency of_the reduction in_the thickness of a non-magnetic substrate which_has_been conventionally used in response to_the_demand for a thinner magnetic layer._This_fact_is described, for example, on_page 77 of the above-described Development_of Magnetic Materials and Technique for High Dispersion of_Magnetic Powder, "..._Higher recording density is a_large_problem_assigned to the present magnetic tape. This is important in_order to_shorten the length_of the tape so as to miniaturize a cassette and_to enable long-time recording. For this purpose,_it is necessary to reduce the thickness of a substrate.... With_the tendency of reduction in the film thickness,_the stiffness of the tape also