JPS6045938A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having an excellent electromagnetic characteristics, running property, etc. by providing a coating type magnetic layer contg. magnetic alloy powder having a specified surface area by BET method and a specific back layer contg. two kinds of carbon having different average grain sizes. CONSTITUTION:Ferromagnetic alloy powder having >=48m<2>/g surface area by the BET method is dispersed in a resin binder to form a magnetic layer having >=1,000Oe coercive force and <=0.08mu surface roughness on the surface of a plastic film base. A thermosetting back layer consisting of a vinyl chloride/vinyl acetate/vinyl alcohol copolymer, polyurethane prepolymer and polyisocyanate or a radiation curable back layer having acrylic double bonds is formed on the rear of the base. Carbon black having respectively 10-60mmu and 60-500mmu average particle sizes are dispersed in the back layer to make surface roughness 0.05-0.6mu. Drop-out, scinting and the tack between the magnetic layer and the back layer are thus obviated.

Description

[Detailed description of the invention]

The present invention is directed to magnetic recording media, and is based on a magnetic recording medium having a magnetic recording density of 9.
Gate to the body. Conventionally, σ・1 amphoteric powders used as magnetic recording media include, for example, r -F a20H, Co-containing r
r-Fe203, Fe304, Co-containing F',
There were B 04 , Cr 02 , etc. However, the magnetic properties of these strong 1c% magnetic powders, such as force and maximum internal magnetic flux density, are insufficient for high-sensitivity, high-density recording, and signals with short recording wavelengths of about 17!m or less. It is not very suitable for magnetic recording with narrow track width.As the demands on magnetic recording media become more demanding, the 1"1" characteristic required for high-density recording is becoming more and more important.
41. ! I'm thinking about it. Such magnetic powders include Fe, Co, F-Crs. Examples include F@-Co-N I, C6-rTi 'J metals, and alloys of these with AI, Cr5S, etc. A magnetic recording medium using such an alloy powder must have a coercive force of 66 mm and a high residual magnetic flux density for the purpose of high-density recording, and various manufacturing methods or methods are used to make the magnetic powder meet these standards. It is necessary to change the alloy composition by j'. The present inventor manufactured magnetic recording media using various alloy powders, and found that the specific surface area by BET method was 48 m/g, the coercive force of the magnetic layer was 12000e or more, and the surface roughness of the magnetic layer was α08μ. It has been found that a magnetic recording medium having a sufficiently low noise level and suitable for high-density short-wavelength recording can be obtained when the following conditions are met. However, upon careful consideration, it turns out that magnetic recording p''P, the medium is wound as a video tape, etc.
Alternatively, when running, if the characteristics of the magnetic layer do not meet the above requirements, the effect of J41J cannot be achieved, and the magnetic layer 1
It has been found that the properties of the supporting plastic (usually polyester) film have a close relationship to the physical and mA properties of the magnetic recording PM body. Therefore, the present inventor further attempted to apply a back layer to the back surface of the plastic film substrate. As a result, it was found that the S/N of a magnetic recording medium is not only related to the specific surface area measured by the BET method of the alloy powder used in the magnetic layer and the surface roughness of the magnetic layer, but also to the surface roughness of the back layer. It was. Also, cinching phenomenon (squeezing when stopping rapidly)
, there are problems such as problems with the back layer, friction, and adhesion between the magnetic layer and the back layer, so a good back layer must be used.
It is not possible to provide a magnetic recording medium with excellent electromagnetic characteristics, runnability, and durability. Vinyl chloride and vinegar t'I on the back layer! Consisting of a thermosetting blend of vinyl/vinyl alcohol copolymer, polyurethane prepolymer, and polyisocyanate, or these and Etrucel ν-su (Q60. Ti compound: I compound) It's a big 1Ilt, changed to +￥
9, and it was found that Do had fewer lag outs every 4 times. However, when the tape F1 runs while still wound, the magnetic tri and the base r(ji; 4'll
Kite I1in ↑1 et al. becomes interpi. Therefore, by lowering the 71J%:l'f;
Drutsubu-out is less likely to occur. However, in the magnetic layer containing alloy magnetic powder mixed in the binder, the conventional Co-containing f -Fed OH and r -F @@
The surface properties must be much higher than those using OH powder. Moreover, as the plastic film used as the support material becomes thinner and thinner, the waist becomes softer (1
1 μn1 or less is currently being considered), and there is a tendency for frictional charging and exfoliation charging to become increasingly large. This drawback can be improved by incorporating guiding particles such as carbon black into the back layer, but if the particle size of carbon black is too small, it will roughen the surface of the back layer.
It was also found that the desired antistatic effect could not be obtained unless a large amount was used. On the other hand, carbon black with a large particle size can provide sufficient conductivity with a small number of particles.
Moreover, if it exceeds 300 mμ, it becomes difficult to disperse, and the particle size tends to be transferred to the magnetic surface side, deteriorating the electromagnetic properties. As for the scraping of the back layer, under high temperature and high humidity conditions, there was no problem with the carbon black particle size of 1o~soomμ at relatively low humidity (40'C, 160%RH), but at 40℃ and 80%RH, the coating film It became brittle and the back layer was scratched. The present invention provides a back layer on the back side of a recording medium having a magnetic layer with very good surface properties, and a binder made of vinyl chloride/vinyl acetate/vinyl alcohol copolymer, polyurethane, and polyisocyanate, or a A thermosetting binder containing nitrocelluose or a radiation-curing binder mixed therein is formed;
Moreover, by setting the surface roughness to 105 to 0.6 μm, a magnetic recording medium with unexpectedly excellent characteristics is provided.
It's W. According to the present invention, even though the degree of interpolation of the magnetic surface is small, the electrostatic charge is small, and dirt and dust do not adhere to it.
Electrical characteristics also improve. Furthermore, in the case of using a radiation-curable binder, the surface roughness of the back layer was difficult to transfer to the magnetic layer, and the electrical properties were further improved. The magnetic layer in the magnetic recording medium of the present invention has a coercive force (Il
e) 10000e or more, BE of the alloy magnetic powder contained
The specific surface area measured by the T method is 4 om"/g or more, and the surface roughness is
, 20 measurements at 17mm (R snow.)・
(hereinafter the same) is 1108 μm or less. The preferable range of coercive force is 1000 to 20[+[10e]; if the coercive force exceeds this range, the magnetic head will be saturated during recording and demagnetization will be difficult. The larger the specific surface area of the magnetic powder, the more 8/
Although there is a tendency to modify the N ratio, it has been found that if the specific surface area is too large, the dispersion of the magnetic powder into the binder becomes poor and the effect tends to be saturated. On the other hand, when the surface roughness is small, the short wavelength recording sensitivity increases. Co, F are examples of magnetic alloys that can satisfy the above characteristics.
e-Co SFs-Co-Ni, Co-N1, etc.
Further, a fine powder to which Cr5Al, 81, etc. are added is used. These are Kinzuki Salt BH. Fine powder obtained by wet reduction with a reducing agent such as, fine powder obtained by shielding the surface of iron oxide with 81 compound and then dry reduction in Ti gas, or fine powder obtained by exploding an alloy in low pressure argon, etc. It has an axial ratio of 1:5 to 1:1o, and a residual magnetic flux density B r
-2,000 to 3,000 Gauss, and satisfies the above winter cropping requirements for coercive force and surface area. The alloy magnetic powder can be made into a magnetic paint using various binders, but thermosetting resin binders and electron beam curing binders are generally preferred, and other additives include dispersants, abrasives, and moisturizers. , an antistatic agent can be used according to a conventional method. oB) i3T surface area ratio is 48
m! /g of magnetic powder, and if there is a problem with dispersibility, a surfactant, an organic titanium coupling agent, or the like may be used as a dispersant. As a binder, a binder consisting of vinyl chloride/vinyl acetate/vinyl alcohol copolymer, a polyurethane prepolymer and a polyisocyanate, a binder further containing nitro-heptylulose, other known thermosetting binders, or a binder sensitive to ionization energy can be used. A radiation-curable binder containing an acrylic double bond, a maleic double bond, or the like as a fl fat group can be used. According to the usual method, the alloy magnetic powder is mixed with a binder, a specified solvent, and various additives to form a magnetic coating, which is applied to a substrate such as a polyester base, and then thermally cured or electron beam cured to form a magnetic film. Further, a back layer is formed in the same manner, and each or the whole is subjected to supercalendering to give a predetermined surface roughness. In the present invention, the back layer formed on the back side of a thin film substrate such as polyester paste can be roughly divided into two types: one is a thermosetting compound containing any of the following compounds, and the other is a radiation-reactive compound as shown below. (ionizable) resin composition. Note that the radiation-curable resin shown below can also be used for the magnetic layer. The thermosetting fi # fat mixture used for the back layer is vinyl chloride/vinyl acetate with carbon black added.
-H= Lua A/Ko-/Ll cofg combination, a thermosetting binder consisting of a polyurethane prepolymer and a polyisocyanate, or further nitro-7-a
It has been found that thermosetting with addition of -sulfur has an excellent effect. The radiation-curable resin mixture used for the back layer is an acrylic, maleic or allyl double bond-containing resin binder to which carbon black is added. The carbon black used in the present invention must be selected from two types having different average particle sizes.
,belongs to. Such a combination of carbon black improves the charging properties of the back layer and at the same time improves the surface properties of LTC.
It is something to do IJ. The ratio of the former to the latter is 1:10~1
It has been found that o: 3 degree is suitable, and carbon black total loss is preferably contained in an amount of about 20 to 40% based on the total weight of the back layer. It has been found that when carbon black of such combination 1 is used, the chargeability and surface properties are better than when carbon black having a particle size of one of these or an intermediate particle size is used. It is desirable that the surface roughness of the back layer of the present invention is 0.05 to 0.6 μm. The surface roughness not only improves the running properties and abrasion resistance of the tape in conjunction with the material of the back layer, but also reduces the adhesion and scinning phenomenon with the magnetic layer, and also has a phase difference with the surface roughness of the magnetic layer. The surface roughness of the back layer is (L
It was found that 87N was maintained well when the pressure was 6 Is m or less. It has been found that when the surface roughness is less than IIL05 μm, problems occur in scintching, adhesion, and runnability. When the back layer is a thermosetting type, the ratio of each component of the binder can be varied within a wide range. 80% by weight, the latter being the remainder, and 5 to 80 parts of polyisocyanate, based on the total amount of the resin as 100, is added. When further adding nidotetracellulose to the above binder composition, 15 to 60% by weight of nidotetracellulose, 10 to 7% by weight of vinyl chloride/vinyl acetate/vinyl alcohol copolymer
0% by weight and polyurethane in a range of 10 to 70% by weight (however, the total amount is 100%). When the total amount of the resin is 100, 5 to 80 parts of polyisocyanate are added. Note that addition of nitrocellulose further reduces tackiness and further improves abrasion resistance. In the case where a radiation-curable binder is used in the back layer of the present invention, the following are examples of resins having a radiation-polymerizable double JA bond, a maleic double bond, or an allylic double bond. You can use duck meat. (1) Vinyl chloride copolymer 341 vinyl acetate/vinyl alcohol copolymer, vinyl chloride/vinyl alcohol copolymer, vinyl chloride/vinyl alcohol/propion 13v vinyl copolymer, vinyl mide/vinegar 6 ■Vinyl-maleic acid copolymer,
Vinyl chloride/acid 6! Vinyl/terminated OH@chain alkyl group copolymers, such as UCC VROHSVYNC, VYE
GX etc. and U CCtl:VEItR etc. can be mentioned. The above copolymer was subjected to radiation M-sensitive modification by adding four acrylic double bonds, maleic double bonds, allyl di- and ilt bonds using the method described later (n) Saturated polyester resin phthalic acid, Isophthalic acid, terephthalic acid, maleic acid,
Saturated polybasic acids such as maleic acid derivatives, succinic acid, adipic acid, sebacic acid, and ethylene glycol, diethylene glycol, glycerin, trimethylolpropane, t2 propylene glycol, 1.3 butanediol, dipropylene glycol, t4 butanediol,
1.6 Saturated polyester resins obtained by ester bonding with polyhydric alcohols such as hexanediol, pentaerythritol, sorbitol, glycerin, neopentyl glycol, and t4 cyclohexanedimethanol, or modification of these polyester resins at 801 N m, etc. resin (Baishin 55S). Those subjected to radiation-sensitivity modification by the method described later (1) Unsaturated polyester resin A polyester compound containing a radiation-curable unsaturated double bond in the molecule 1, for example, described as a g(it) term thermoplastic resin A saturated polyester resin consisting of an ester bond of a polybasic acid and a polyhydric alcohol, and includes unsaturated polyester resins, prepolymers, and oligomers containing radiation-curable unsaturated double bonds in which part of the polybasic acid is maleic acid. be able to. Examples of the polybasic acid and polyhydric alcohol components of the saturated polyester resin include the compounds listed in item (1), and examples of the radiation-curable unsaturated double bond include maleic acid,
Examples include fumaric acid. The radiation-curable unsaturated polyester resin is produced by a conventional method, in which 1 m or more of the polybasic acid component and 111 m of the polyhydric alcohol component are added with maleic acid, fumaric acid, etc. in the presence of a catalyst.
After dehydration or dealcoholization reaction in a nitrogen atmosphere at 80-200°C, the temperature is raised to 240-280°C, and a5-15B
A polyester resin can be obtained by a condensation reaction under 2O3 pressure. The amount of needles containing maleic acid, fumaric acid, etc. is 1 to 40 moles, preferably 10 to 30 moles, in the acid component due to crosslinking during production, radiation curability, etc. (IV) Polyvinyl alcohol resin polyvinyl alcohol, butyral resin, ateptal resin, formal resin, and copolymers of these components. The hydroxyl groups contained in these resins have been subjected to radiation sensitization modification using the method described later. Epicote 152.154.828.1001.1004.1oo
7) Dow Chemical [(DEN431, DER7!52,
DIR511, DER331), Dainippon Ink (Ebikuron 400, Ebikuron-8oo), and the above
High polymerization degree of xylene W II! UCC? ! l: W phenoxy resin (PKHA, PKIIC, PKH)
Copolymer of odor-accumulating bisphenol A and epichlorohydrin, Dainippon Ink Chemical Co., Ltd. (Evicron 145.1)
52.153.1120) etc. These resins are subjected to radiation-sensitivity modification using epoxy groups (■) Cellular conductors Cellulose-based derivatives of various molecular weights are also effective as 44-column plastic components. It is. Among them, particularly effective ones include nitrified cotton, cellulose aptopylate, ethylcellulose, butylcellulose, and acetylcellulose.The hydroxyl groups in the N fat are activated and radiation-sensitized modification is performed using the method described later. Other resins that can be used for radiation-sensitive modification include polyfunctional polyester resins, polyether ester resins, and polyvinylpyrrolidone 4i! ! Fats and derivatives (p
(vp olefin copolymer), polyamide resin, polyimide resin, phenol resin, black tetraacetal resin, acrylic ester and methacrylic ester containing hydroxyl group as a polymerization component.
G is also valid. Furthermore, by blending a thermoplastic elastomer or prepolymer with the radiation-sensitive modified thermoplastic resin,
Even more Ii! It is possible to create a lI@ coating film. Even,
As discussed below, these elastomers or prepolymers also emit radiation 41! It is more effective if it is modified to be sensitive. Listed below are elastomers or prepolymers that can be combined with the radiation-sensitive resin. (I) Polyurethane elastomer, prepolymer, and telomer Polyurethane elastomer is particularly effective in terms of good abrasion resistance and good adhesion to PET film. Examples of such urethane compounds include 2,4-toluene diisocyanate, 2,6
-tolunin diisocyanate), t3-xylene diisocyanate, 1,4-xylene diisocyanate, t5-
naphthalene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate), &5'-
Dimethyl-4゜4'-diphenylmethane diisocyanate, 4.4'-diphenylmethane diisocyanate, 3
+S'-dimethylbiphenylene diisocyanate 441-Biphenylene diisocyanate, hexamethylene diisocyanate, isophonyl diisocyanate, dicyclohexylmethane diisocyanate, various polyvalent isocyanates such as Desmodur L1 Desmodur N, and linear saturated polyesters (ethylene glycol, diethylene glycol, Polyhydric alcohols such as glycerin, trimethylalpropane, 1,4-butanediol, 1t6-hexanediol, pentaerythritol, sorbitol, neopentyl glycol, t4-Schifftetrahexane dimetatool, phthalic acid, isophthalic acid, (by condensation polymerization with saturated polybasic acids such as terephthalic acid, maleic acid, adipic acid, sepacic acid, etc.), linear saturated polyethers (polyethylene glycol, polypropylene glycol, polytetraethylene glycol) and caprolactam, human tetraxin-containing acrylic ester,
Each 4ifl of hydroxy-functionalized methacrylic acid ester, etc.
Polyurethane elastomers, prepolymers, and telomers made of condensation products of polyesters #, ', and 1 are effective. These nidistomers were exposed to various types of heat nJ for radiation-sensitive denaturation.
'ilJ plastics may be combined as is, but by further reacting with a monomer having an acrylic double viscosity or allylic double bond that reacts with the terminal incyanate group or hydroxyl group of the urethane elastomer. , it is very effective to modify the radiosensitivity. (1) Acrylonitrile-butadiene copolymer elastomer An elastomer such as an acrylonitrile-butadiene copolymer prepolymer with a terminal hydroxyl group, which is commercially available as PolyBD liquid range manufactured by Sinclair Petrochemical Co., Ltd., or No1 Car 1452J manufactured by Nippon Shichion Co., Ltd. In particular, the double bond in butadiene is suitable as an elastomer component in which radicals are generated by radiation and crosslinked and polymerized. (1) Polybutadiene elastomer Sinclair Vetrochemical Polymer BD Liquid Resin R-15 and other low molecular weight prepolymers having hydroxyl terminals are particularly suitable in terms of compatibility with thermoplastics. Since the R-15 prepolymer has a hydroxyl group at the end of the molecule, it has the ability to increase radiation sensitivity by adding a bond to the acrylic unsaturated end of the molecule, making it even more advantageous as a binder. becomes. In addition, polybutadiene cyclized product Nippon Synthetic Rubber Co., Ltd. CBR-
M901 also exhibits excellent performance when combined with thermoplastics. In particular, the increased polybutadiene has better efficiency in cross-V4 polymerization by radiation than the radical coercion of unsaturated bonds inherent in polybutadiene, and has excellent properties as a binder. Suitable geothermal plastic elastomers and (prepolymer) systems include styrene-butadiene rubber, chlorinated rubber, acrylic rubber, isoprene rubber and its cyclized products (Japan Synthetic Rubber% + 5CIR701), epoxy-modified rubber, internally plasticized saturated Elastomers such as linear polyester (Toyobo Baytan #+300) can also be effectively used by applying the radiation-sensitive modification treatment described below.Next, an example of synthesis of a radiation-sensitive binder will be explained. Manufacturing method of adduct -> Synthesis of acrylic modified vinyl chloride/vinyl acetate copolymer resin (radiation sensitive modified resin) 750 parts of vinylite VAGH, 1250 parts of toluene, 500 parts of citalohexanone, 57 parts
Pour 4 pieces into a flask, heat and dissolve, raise the temperature to 80°C, add 61.4 parts of ditolylene diisocyanate-hydroxyethyl methacrylate duct, and further add 0.012 parts of tin octylate and 0.012 parts of hydroquinone. 8
The reaction was carried out at 0° C. under N gas flow until the NGO reaction rate reached 90%. After the reaction is completed, cool and methyl ethyl lactone 12
Dilute 50 copies. *Production method of 2-hydroxyethyl methacrylate (2HEMA) adduct of tolylene diisocyanate (TDI) Add 348 parts of tolylene diisocyanate to N! 80 ° Ck in a 4-hole flask in a stream of air: ) After J11 heat, 2-
260 parts of hexaethylene methacrylate, 07 parts of tin octylate, and 0.05 parts of hydroquinone were added dropwise at 80°C for 5 hours while controlling the cooling so that the temperature inside the reaction vessel was 80 to 85°C. Stir to complete the reaction. After the reaction is complete, take it out and cool it down to a white paste-like TD.
2nEMAe of I? It was. b) Synthesis of butyral W fat acrylic peelable body (radiation sensitive modified resin) Butyral resin seed water chemistry? , 4BM-8, 1,912 parts of toluene, 71 parts of cyclohexanone. 574 parts were placed in a round flask in Part A, heated to 80'C, and then 7.4 parts of 2-hydroxyethyl methacrylate adduct of tolylene diisocyanate was added. , hydroquinone (101
5 parts of the mixture was added, and the reaction was increased at 80° C.rN in an air stream until the j-I CO reaction rate reached 90% or more. Anti-Li; 4 parts % solution, cooled and root-grown with methyl ethyl ketone. C) Synthesis of saturated polyester resin acrylic material (
Radiation! ! ! Sensitive modified resin) 100 parts of Toyobo Vylon RV-200 was mixed with 11 parts of toluene.
6 parts, dissolved in 116 parts of methyl ethyl ketone at f8 and heated to 80
After raising the temperature to
Add 07 parts and N! NGO reaction rate 90 at 80℃ in air flow
% or more. d) Synthesis of acrylic modified epoxy resin (radiation-sensitive modified resin) 400 parts of Ebihut 1007 manufactured by Shell Chemical Co., Ltd. was heated and dissolved in 50 parts of toluene and 50 parts of MEK for 78 hours, and then N,N-dimethylbenzylamine 0.0061i5, hydroquinone o,
Add 1 part of o s to 80°C, add 69 parts of acrylic acid, and stir at 80°C until the fermentation temperature reaches 5 or less. -) Synthesis of acrylic modified urethane elastomer (radiation 1; I-sensitive elastomer) 250 parts of terminal isocyanate (diphenylmethane diisocyanate) (MDI) based urethane prepolymer (Niboran 4040 manufactured by Nippon Polyurethane), 2HIMA3
2.5 parts of hydroquinone, 0.07 parts of hydroquine, and 009 parts of tin octylate were placed in a reaction vessel, heated to 80°C, and then T
43.5 parts of DI was added dropwise while cooling the reaction vessel to a temperature of 80 to 90°C, and after the dropwise addition was completed, the reaction was allowed to proceed at 80°C until the NGO reaction rate reached 95% or more. f) Synthesis of polyether-based terminal urethane U tl'-elastomer acrylic modified product (radiant lIF compatible etchelastomer one piece polyether PTG-50025 manufactured by Polyurethane Co., Ltd.)
0 parts, 2 HEMA 32.5 parts, hydroquinone [1
007 parts and 0.009 parts of tin octylate were placed in a reaction can and heated to 80°C to dissolve the fa, then 43.5 parts of 'rDI was cooled to a temperature of 80 to 90''C in the reaction can! 3] L, 7
: After dropping, react at 80"C until the N00 warpage rate reaches 95% or more.g) Synthesis of polybutadiene elastomer acrylic open material (radiation reaction elastomer)' Manufactured by Sinclair Petrochemical Co. Low molecular weight hydroxyl end butadiene polyBD liquid resin R-15250 parts, 2 IfEMA 52.5 parts, Hyde p-quinone 0.0
07 parts and 0.009 parts of tin octylate were placed in a reaction can.
After the heating bath W1 was heated to 80°C, 45.5 parts of TDI was added dropwise while cooling so that the temperature inside the reaction vessel was 80 to 90''C.
After the dropwise addition is completed, the reaction is allowed to occur at 80"C until the Nco reaction rate reaches 95% or more. In addition, some polymers are known to disintegrate when exposed to radiation, while others cause crosslinking between molecules. Examples include pyriethylene, polypropylene, pyristyrene, polyacrylic acid ester, polyacrylic ester, polyvinyl chloride, polyester, polyvinylpyrrolidone rubber, polyvinyl alcohol, and polyactetralein. Since the crosslinking reaction occurs without any particular modification, it can be used as a backcoat resin for radiation crosslinking as it is.Furthermore, according to this method, it is a solvent-free resin that does not use a solvent. Since the resin can be cured in a short time, such a resin can also be used as a back coat.Furthermore, as the t8m energy beam used for crosslinking the back coat of the present invention, a radiation Electron beams used as the source, r-Azusa using CO@0 as the M source, !- rays using Sr.O as the source, and X-rays using an X-ray generator as the #i source are used.In particular, As a splitting radiation source, it is advantageous to use radiation using a radiation heater from the viewpoints of controlling the absorbed dose, introducing it into the foil manufacturing process line, and blocking ionizing radiation.Used when curing the back layer. As for radiation characteristics,
From the viewpoint of penetrating power, it is convenient to irradiate using a radiation accelerator with an acceleration of 1 n pressure of 100 to 750 KV, preferably 150 to 300 KV, so that the absorbed dose is 0.5 to 20 Megaland. In order to harden the back layer of the present invention, a low culm pi type i-ray m manufactured by Energy Sciences, Inc. in the United States is used.
M! a (Elect A Curtain System) etc. seeping into the tape coating processing line, blocking secondary X-rays inside the accelerator? (・``This is a good idea.'' Of course, a van de Graaf accelerator, which has been widely used as a radiation accelerating material, may also be used. Also, for radiation crosslinking, N, gas, He gas, etc.) can be used. It is important to irradiate the backing layer with radiation in an inert gas stream, and irradiating the back layer with radiation in the air will remove the 03, etc. generated in the polymer due to the effects of radiation irradiation during crosslinking of the binder component. This is extremely disadvantageous because it inhibits the radicals from working favorably in the crosslinking reaction.Therefore, the atmosphere of the area to be irradiated with active energy rays is
In particular, it is important to maintain an inert gas atmosphere such as N@ or H@sCO snow with a maximum oxygen concentration of 1%. A portion of the binder of the binder, hack layer, or magnetic layer may contain a radiation-curable monomer such as acrylic acid, methacrylic acid, acrylamide, methacrylamide, or the like. Radiation-curable resins are also used to improve abrasion resistance and adhesion. urethane elastomer and polyurethane prepolymer, acryl tetranitrile butadiene ffi
A combined estomer, a polyptadiene estomer, etc. can also be used in combination. The fact that the back layer is of the radiation curing type means that it is possible to form a more uniform and tougher back layer than that of the thermosetting type. The presence of one back layer tends to increase jitter. Here, jitter means slight phase modulation around the recording 1n wave. This phenomenon seems to be related to the smooth running of the tape. Calculation can be solved by the presence of a very small amount of fatty acid or fatty acid ester lubricant. These acids or esters preferably have 10 to 22 carbon atoms, such as lauric acid, stearic acid, myristic acid, or mixtures thereof. It has also been found that it is sufficient that the amount used is 3 or less of the total weight of the back layer. Examples of the present invention will be described in detail below. Magnetic Layer 1 A 43-layer powder was prepared using the wet J-olfactory method. These are made up of acicular particles with an axial ratio (minor axis/long axis) of 115 to 1/10, and a residual magnetic flux density of 2000 to 3000 Gauss.
Coercive force 1000~20000e, BET surface area ratio 4
5 to 70 m" and 7 g. These magnetic powders were mixed in the following blending ratio in a conventional manner. mouth) 250
Myristic acid 2 Sorbitans dealate 2 To this mixture, polyisocyanate (Bayer Desmodur L) was added to obtain 6Bt! It was made into a paint, formed on a polyester film to a thickness of &5μ, and calendered. Example 1 The following resin composition was mixed as a back layer. A: Methyl ethyl ketone/) Luene (50150) 200
Carbon black (15-100 mμ) 70 Add 3 parts of polyisocyanate (Desmodur L) to this mixture.
0 parts by weight were added and mixed, coated to a thickness of 15 μm on the back side of the polyester film provided with the above magnetic layer, dried, calendered, heat cured, and cut into video tapes. The surface roughness of the magnetic layer and back layer can be adjusted to 0.01 to 0.01 by adjusting the calendering process in various ways.
0.08μ271, 0.05~0 for the back layer
．． A sample having a diameter of 8 μm was obtained. When we investigated the surface resistance of the above tape, we found the following. Table 1 Based on this, when carbon black in the above composition was replaced with a mixture of 21ff1μ and 300mμ, the following results were obtained. The results in Table 2 can be explained as follows. That is, the combination of two types of carbon black improves the surface roughness, thereby reducing the influence of deterioration in electromagnetic properties. It was found that the te1 of the two types of carbon black was improved by 0.4 dB in total, whereas there was a decrease of -0.4 dB or more in the case of carbon black alone. This is probably because the back layer imparts appropriate flexibility and improves surface properties. Based on the above facts, in the following examples, the average particle size is 10~
A combination of do*7< and 60 to 5001 nμ was used. Example 2 The surface roughness of the magnetic layer was 0.01 in the same process and under the same conditions as in Example 1, except that the composition of the magnetic layer was changed as follows.
~Q, 08μm, and back layer surface roughness 0.05~0
．． Made 11,111 8μ wing video tapes. Part by weight Mixed solvent (MIBK/)Luene-1/1) 300 Example 3 Part by weight Carbon black (20m#/450t+t#=1/1
) 50 acrylic modified polyurethane elastomer e)
20 mixed solvent (MIBK/) luene = 1/1) 300
The above mixture was dispersed in a ball mill for 5 hours, and a dry thickness of 15 mm was applied to the back side of the polyester film on which the magnetic surface was formed.
μ, and irradiate the back layer with an electron beam using an electrocurtain type electron beam accelerator at an acceleration voltage of 150 K@V, an electrode current of 10 mA s, and an absorbed dose of 1° Mrad z N* gas. After curing, it was calendered, rolled up, and cut into 1/21 video width. Example 4 Parts by weight Carbon black (25 mμ 7450 mμ) 5° Acrylic modified polyester resin e) 6° Mixed solvent 500 The above mixture was prepared in the same manner as in Example 3 to obtain a sample. Example 5 Part by weight Carbon bra walk (50 pm 1550 pm) 50 Acrylic modified polyurethane elastomer e) g. Mixed solvent 300 The above mixture was prepared in the same manner as in Example 3 to obtain a sample. Magnetic layer 2.3 was prepared in order to study the effect of the formation order of the magnetic layer and back layer.□Magnetic layer 2 Using the same magnetic alloy powder and base as magnetic layer 1, the following mixture weight part Fe-Go- N1 alloy powder 100 Polyvinyl butyral t! Jlllff) 1゜Acrylic double bond-introduced urethane e) 10 Methyl edyl ketone/toluene (so, "so) 250 was coated on a polyester film to a thickness of &5μ, and subjected to electron beam curing and calendering. (i7 ?11 mihazo) 3 (

[Make a recording medium using the same method as for ζi1'11M2 and the following composition! ! II! Built. Part by weight Fe-Go-N% alloy powder 100 Saturated polyester tree 111a 5 Acrylic double bond-introduced polyether urethane elastomer f) 10 IL@solvent 250 These magnetic M2.3 and the above-mentioned af, 14 layer 1 and ,
Example 1 (carbon black was 4otnμ/35
0 mμ = 1/1), 3.4.5 pack layers were formed by changing the order appropriately to prepare a videotape. The formation order including the examples is as follows. In either case, calendering was performed at the time of forming each layer. In the table, ■ and ■ indicate that the layers were formed in that order. In addition, as a comparative example, magnetic layer 1 (without a pack layer) (comparative example 1), the one in Example 3 in which carbon black with an average particle diameter of 3 oom was used as a hack layer, and the magnetic layer 2 was used as a magnetic layer. (Comparative Example 2) is also shown in the table. Further, Table 3 shows various characteristics of these magnetic recording media. The measurement method will be described later. Moreover, all the surface roughnesses shown in the table fall within the scope of the present invention. Examination of Results The surface roughness of the videotape of Example 1 above was examined. Figure 1 shows 8I when a videotape is driven at 5.8 m/sec and recorded and played back at a center frequency of 5MH1.
Shows the N ratio (relative value). However, the subscript of the curve is the surface roughness of the magnetic layer. As can be seen, the surface roughness of the magnetic layer is αo e pm or less, and the surface roughness of the back layer is α6μ
m or less, the 8/N ratio can be kept high. The same was true for Examples 2.3.4.5. Next, when running friction was examined, it was found that friction was large when the surface roughness of the back layer was 0.05 μm or less. Regarding Example 1, the surface roughness of the magnetic layer was α08/l f
i1 or less and the surface roughness of the back layer is 0.05 to a6/
When the relationship between the BIT specific surface area of the alloy powder and 8/N was investigated for those in the range of jm, the results shown in FIG. 2 were obtained. However, the standard was 55 dB. From this, it can be seen that excellent characteristics are obtained when the BET value is a8m"79 or more. The same was true for other examples. Also, the data in the table above summarizes the Ni tJtl of the above surface roughness. To put things in order, we can see that: 1) Rolling under high temperature and humidity (40°C 80% It) 1) L comb running: 1 t Comparative example 1: IL! 1 friction and 100 under high temperature and humidity
High friction after rotation. Sinching occurs because it does not contain carbon. There are also many dropouts, and the high friction on the back surface causes the bank surface to be scraped. Among 2, A, and 11, B is better because it contains nitrocellulose. For AC and D, the back side is made of electronic cotton 1. '+i4 conversion? ('L's ~, there is less back mold transfer during stationary curing / [Retrotube out is reduced. 4, E is 11ε child pure 1i1ji on both sides):, 2
N It's getting even better. 5. Is Comparative Example 2 carbon 300/lF? I (/,
)No 4. '>ji'lj is R3°α70 μm. Therefore, the deterioration of the electric current #j characteristics is large. In addition, because the particle size is large, it becomes non-uniform on the back surface, resulting in
It does not take any anti-resistance countermeasures, and cinching, back scratching, and adhesion occur, and dropouts are also large. (2) As it becomes a radial leg curing type, the influence of back mold transfer decreases and the properties become better. t Coefficient of friction: 4 mm Diameter: Wrap the magnetic tape around an aluminum cylinder with a polished surface at an angle of 180 degrees with the back direction inward, and run it in 2.7 seconds, then take it up from the feeding side. The tension on the side was measured and calculated by nl (running initiator and 10
(after 0 runs). 2. Scinching phenomenon The tape was run 100 times at 40° C. and 80% Itll using a commercially available V HS system V T It. The scintillating lily (R4) was visually observed. A case where the rolled portion was good with no gap between the tape layers was considered good, and a case where there was a gap 6 between the tape layers was judged as poor. 5. Using a commercially available VHS type VTII with 91 h etc. (back), observe the dirt inside the rear 7-t case after running it 100 times at a temperature of 40 ° C and 80% relative 974 jj (1 boundary). 4. Adhesion between magnetic layer and back layer V) Rolled up onto 181J-R, 60°'G (1) fi
t + jp, and the adhesion status after 5 days of dispersion was evaluated by one observation. 5. Surface roughness TAYLOR-TTOBSI Company N-1
! ) from the chart obtained using the 20-point average method (1Lzo
) was successful. Cutoff 0.17m? n,fl
Pressure 2119, needle 0.1X 2.571m was used. 6. Electromagnetic characteristics■Center frequency 5Ml1. (I;・1T1 happened!)
(The BlN ratio (relative I1a) is shown for 1.
It has been made possible to set up IT z up to 1. ■Dropout is the value at 15/18, 11・“
4/M%N. 1. Electron microscopy method ■Extraction method from tape using transmission electron microscopy. The average particle size is thereby measured. ■Scan! I! Photographed using a 1m microscope using the surface photography method. In this case, the particles may be aggregated, so if the variation is large, the minimum particle diameter is set to 11 diameters.

[Brief explanation of drawings]

(Figure H1 is a magnetic record? ≠ A graph showing the p-surface roughness of the magnetic layer and pack layer of the medium and the 1 engineering ratio of 87H, and Figure 2 is the alloy 1it) Fried powder, car BET ratio surface tan and 87N It is a graph showing the relationship between Figure 1 Continued from page 1 0 Inventor: Hiroshi Yu Oka, Type 1 Company, Chuo-ku, Tokyo Inventor: Kubo 1) Yu - 1-1, Yohonbashi, Type 1 Company, Chuo-ku, Tokyo, No. 1 Tee DK Stock 1 Honbashi 1-1 1-1 TDC Stock Procedures Amendment 1980 7 JJS Japan Patent Office Commissioner Manabu Shiga Incident Indication 1982 Characteristics Application No. 152558 Name of Invention Magnetic Recording Media Amendment Relationship with the patent applicant's name (306) TDC Co., Ltd. Agent 10 "1FW- at -λ-+ '+,!;-'-11 ・-111-"-" lI I, uu ++J J
Jr7DTT"'□--1■1': τ ) R1 Runo・
L-wa - Invention of sub-number subject to amendment Nagisa Z application - Salary = 0 inventors in the specification - Scope of fee request - Column for detailed explanation of the invention = 1 Correct contents As shown in the attached sheet L 1ltj Hoso IIO Tei Line 10 says "Carbon black (15-100mμ) 70", then break the line and add as follows. “Stearic acid 5 Myristyl myristate 2” 2. “Mixed solvent (MIBK/
Toluene = 1/1) SOO", then add a line break and add as follows. "Stearisoic acid 5 Myristyl myristate 2"

Claims (1)

[Claims] 1. P with ferromagnetic alloy powder dispersed in resin binder
In a magnetic recording medium in which a magnetic layer is adhered to a plastic film base, the alloy powder has a thickness of 48 m by the BET method.
"It has a surface area of 711 or more, and the coercive force of the magnetic layer is 100.
00e or more, and the surface of the magnetic layer! I'li roughness is α08
μm or less, and furthermore, on the back side of the heath, there is a thermosetting pack layer or acrylic double bond consisting of vinyl chloride/vinyl acetate/vinyl alcohol copolymer, polyurethane prepolymer, polyisocyanate, or these and Nido Tashichi lulose. , a radiation-cured back layer made of a resin having a maleic double bond, or an allylic double bond, and has an average particle size of 10 to 60 mm inside. nμ carbon black and average particle diameter 60-5 D Ontμ carbon black are uniformly dispersed and the surface roughness is 0.05-0.05.
A magnet 1 C≠Q magnet 11 body, characterized in that the back layer is α6 μnt.