JPS5832232A - Double layer coated magnetic recording medium - Google Patents

Abstract

PURPOSE:To reduce the fluctuation of an output and to eliminate a slump at a middle sound frequency range, by forming the 1st and 2nd magnetic layers using a radiation polimerizing binder on a nonmagnetic supporter. CONSTITUTION:A binder composed of the 20-80wt% radiation-sensitive resin or thermoplastic resin which has the radiation-sensitive unsaturated double coupling and the 80-20wt% radiation-sensitive unsaturated double coupling, having crosslinked and polimerized with irradiation of radiant rays plus the >=81.8% magnetic powder are coated on a nonmagnetic supporter. Then the radiant rays are irradiated to this supporter in a inert gas atmosphere and by means of an electron beam accelerator. Thus the 1st magnetic layer is obtained with 350-630Oe coercive force and 2.1-2.8mum thickness. A magnetic coating material containing the above-mentioned binder and magnetic powder is coated on the 1st magnetic layer along with the irradiation of radiant rays under the same conditions as mentioned above. Thus the 2nd magnetic layer is obtained with 510-800Oe coercive force and >=2.1mum thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a two-layer coated magnetic recording medium, and more particularly to a magnetic recording medium having first and second magnetic layers using a binder that is cured or polymerized by radiation. It is something.

In recent years, in audio cassette tapes.

There is a growing demand for better high frequency characteristics. Also, for low-speed running, such as half-speed decks and micro cassettes, more favorable high frequency characteristics are required. Generally, magnetic powder with high coercive force is required to improve high frequency characteristics, but high coercive force alone degrades low frequency characteristics, so it is necessary to have two upper and lower layers that share high frequency and low frequency characteristics. Two layer coated magnetic recording media have been developed.

Conventional two-layer coated tape uses a magnetic paint in which magnetic powder having a coercive force in a range corresponding to the assigned frequency is dispersed in a thermoplastic or thermosetting resin binder for both the upper layer and the lower layer. Magnetic coatings that use such thermosetting binders are produced by a chemical reaction between a crosslinking agent, typically a compound containing a polyvalent isocyanate group, and a reactive functional group, such as a hydroxyl group or an amino group, in the binder. A three-dimensional network structure is formed between the binders, and as a result, audio cassette tapes with two-layer coating and excellent high frequency characteristics have been produced.

However, the use of such thermosetting binders poses quality problems such as output fluctuations at low frequencies, output decreases and fluctuations at high frequencies, and constraints on rationalization and automation of production methods. Problems in product management have been recognized, and while constant efforts are being made toward the goal of manufacturing high-quality products at low cost, major limitations or obstacles have been encountered.

Specific problems include the following: (a) Isocyanates, etc., are highly reactive.
Since a compound is used, there is a problem with the pot life of the magnetic paint. It has been found that as the pot life becomes longer, the reaction of the magnetic paint progresses, and this fact greatly affects the output fluctuations in the low frequencies of peaks 1 to 3 and the output decrease in the high frequencies. There is a restriction that surface treatment and other steps after coating the magnetic layer must be carried out before the three-dimensional network structure is formed in the magnetic layer as much as possible.

(b) Prevents reduction in dimensional stability due to thermal deformation of polyester film, which is widely used as a base material for magnetic recording media, and prevents transfer between magnetic layers in non-uniform areas, and prevents leaching of components in the magnetic coating film. In order to prevent blocking effects caused by this, there are upper limits on the temperature of the curing furnace and the temperature of the hot air, infrared rays, and far infrared rays used as heat sources, and there are also limits on the amount of low molecular weight components such as curing agents used.

(c) The energy efficiency is poor because thermal energy is used to promote the curing reaction, and the binder is mainly made of high molecular weight polymer to prevent adhesive force during first layer roll coating (due to line speed, etc.) Dissection usage was high, resulting in high energy and solvent costs.

(d) Smoothening of the surface of the Japanese sulfuric layer as the density increases
An important problem is that in the process of forming a magnetic ampere, D transition occurs in the magnetic layer due to the surface roughness of the back surface of the paste material due to close contact between the back surface of the paste base material used and the surface of the magnetic layer during winding around the roll. The surface became rough due to the drying process and the high amount of solvent used, which caused the surface to become uneven during drying.

(E) During thermosetting, the surface roughening effect due to the tightness of the first magnetic layer is unavoidable. Uniform winding tb occurs, and stress is applied again to the paste and magnetic surface, causing large distortion in the repainting process, which is undesirable because it causes deformation of the paste, deformation of the magnetic film, and blocking force.

Furthermore, since the paste surface and the magnetic layer surface were in close contact at the start of thermosetting, the magnetic layer was sometimes chipped while the coating was still weak.

(f) This is related to the above, but with the increasing density of brass, which seems to be progressing more and more, it is difficult to maintain a balance between high density and other characteristics in terms of quality. It has become to.

On the other hand, conventional two-layer coated tape has a large difference in coercive force between the first magnetic layer and the second magnetic layer, so the frequency characteristics in the low and high ranges are good, but the frequency characteristics in the middle range are poor. 5 becomes distorted, resulting in the so-called sagging phenomenon.

As a result, the original sound is not faithfully reproduced in the midrange, where the main components of ordinary music are located, resulting in a highly distorted sound. In addition, there was also the drawback that the coating thickness of the second magnetic layer was relatively small, resulting in large output fluctuations.

It is an object of the present invention to overcome these drawbacks of conventional two-layer coated magnetic recording media.

The present inventor uses a material that can be cured or polymerized by radiation as a binder in the first and second magnetic layers of a two-layer coated magnetic recording medium. By using radiation curing technology to harden the binder, and by controlling the thickness of the first and second magnetic layers and the coercive force of the magnetic material contained therein, the above problems can be solved all at once. We found that it was improved.

The improvements made possible by radiation curing technology are as follows.

(A) The chemical and physical stability of the magnetic paint and the magnetic paint film after coating/coating is high, and there are no restrictions in processes such as pot life in the paint state and surface treatment of the paint film until radiation irradiation is performed. I don't accept it. Therefore, the conventional effects of fluctuations in output in the low range and lowering of the output image in the high range due to the progress of the pot life of the paint are avoided.

(B) Since radiation curing occurs instantaneously, it is extremely advantageous to streamline and automate the production process and ensure quality stability by combining the process of postmortem radiation irradiation without performing the necessary treatments. Become.

(C) The crosslinking and polymerization drying of the binder according to the present invention is carried out by radiation irradiation (which generates radicals in the binder), which instantly crosslink and polymerize, thereby curing and drying the magnetic coating film. Therefore, it is only necessary to instantaneously irradiate a maximum of 2Q Mraa of radiation only to generate radicals, and in this case, the polyester film, which is widely used as a base material, does not remain in a static state, and the system In addition, because irradiation is carried out online in a sheet form, the yield decreases due to interlayer transition of the non-uniform magnetic layer during heat curing after being rolled up. This is advantageous in preventing a drop in S/N in the wavelength region.

(D)L? ) As I have already mentioned, the reaction is a radical reaction), unlike conventional static curing chemical reactions, it does not require long heating to accelerate the reaction, and the degree of crosslinking and degree of dryness due to polymerization can be controlled by the radiation dose. Since this can be easily controlled, problems such as sticking due to seepage of low molecular weight components in the magnetic layer can be prevented. It is also advantageous as a means of saving energy required for the curing process and as an energy saving measure.

According to the present invention, the binder in each of the first and second layers of the two-layer coated magnetic recording medium is capable of crosslinking and polymerization by the above-mentioned irradiation with radiation. Acrylic double bonds such as acrylic acid, methacrylic acid or their ester compounds, maleic double bonds such as maleic acid and maleic acid derivatives, and allyl-based compounds such as sialyl phthalate, which exhibit double bonds. The radiation-sensitive soft resin acid having the double bond or its prepolymer, oligomer or telomer is mixed with the radiation-sensitive modified resin having the radiation-sensitive unsaturated double bond of the double bond group and plasticized. Preferably large. Thermoplastic resins can also be combined, which is beneficial in imparting flexibility.

Radiation-sensitive modified resins, radiation-sensitive soft resins, their prepolymers, and oligos! - to mixed feeding ratio with telomer,
In order to satisfy the properties shown below, it is preferable that the ratio of the former to the latter is in the range of 8:2 to 2:8.

The radiation-sensitive modified resin obtained here has a dynamic elastic modulus of 1.0 in the temperature range of 20 to 60°C for 100 hours before radiation-sensitive modification. OX 1. It is desirable to have a value of O"dyn/am" or more.

On the other hand, radiation-sensitive soft resins, their prepolymers, oligomers, and telomers have rubber elasticity as synthetic rubber,
It has excellent flexibility and adhesion to the polyester paste surface, and has round properties, and has a dynamic elastic modulus of 20 to 6 in blueolz.
It exhibits mechanical properties of less than 1, OX 10"a711/(@) in the range of 0°C and is soluble in solvents.

These radiation-sensitive modified resins, radiation-sensitive soft resins, and their prepolymer! -, oligomers, and telomers are subjected to radiation-sensitive modification, which generates diradicals and forms crosslinked structures when exposed to radiation.

From the standpoint of improving the dispersion of the radiation-sensitized resin component and the soft resin or its prepolymer, Oligo ff-, Telomer Co., Ltd., magnetic fine particle powder, it is desired that the compatibility be excellent.

By combining such a radiation-sensitive modified resin component with a soft resin or its prepolymer, oligomer, or telomer, and by utilizing a binder that is formed into a tertiary nanostructure (by radiation irradiation), the above-mentioned method can be achieved. Problems caused by the pot life of conventional binders are solved. As mentioned briefly above, until now the first layer had a problem of output fluctuation in the low frequency range from 1st to 8th due to the pot life of the magnetic paint, but with the binder of the first layer, This problem can be solved by replacing it with a radiation-sensitive resin. By replacing the second layer with a radiation-sensitive resin, it is possible to suppress a decrease in output due to pot life in the paint at high frequencies, for example, 16 outputs. In addition, there is no curling distortion during the heat curing treatment of the layer, and it is also possible to prevent a decrease in dimensional stability due to thermal deformation of the polyester film and blocking formations in the magnetic coating film. By using a radiation-sensitive resin for the first and second layers, it is possible to manufacture a magnetic recording medium with a stable production process and stable and improved quality.

In addition to the electromagnetic conversion characteristics of magnetic recording media used for various applications such as audio, video, memory, and metering, this binder is also effective in various physical properties required for magnetic coatings, such as hardness. flexibility, abrasion resistance, moderate friction coefficient and stick-slip, no phenomenon, surface moldability, adhesiveness with paste, elastic modulus, and various physical properties such as low to high temperature, low to high humidity. It is extremely effective in maintaining stability under various environmental conditions across humidity.

The thermoplastic resins effective for radiation sensitivity modification used in this paper include the following synthetic resins for paints: (D Vinyl chloride copolymer a) Vinyl chloride-vinyl acetate-vinyl Alcohol copolymer, vinyl chloride-vinylalco”2I-1 polymer, vinyl chloride-vinylaluminum-vinyl propionate copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer,
Vinyl chloride-vinyl acetate-terminated OH1m chain alkyl group copolymer, e.g. UCC VROH% VYNC, VYE
Examples include Ucc's VgRR manufactured by G-X.

Add 20Mra of radiation-sensitive modified vinyl chloride copolymer to the bag.
When used at a low dose of less than a, the reaction mechanism is not clear, but in addition to radical reactions generated from radiation functional groups such as acrylic double bonds, radicals are generated by some reaction due to radiation irradiation, and the crosslinked structure It was confirmed that it is effective as an inder for magnetic recording media.

b) The above copolymer is subjected to radiation-sensitive modification by introducing an acrylic double bond, a maleic acid double bond, or an ester double bond by the method described later.

(Saturated polyester resin a) Saturated polybasic acids such as phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, and sepacic acid, and ethylene glycol, diethylene glycol, glycerin, trimethylolprono(n), 1,2-propylene Glycol, 1,3-buta/diol, diethylene glycol%
Saturation obtained by ester bonding with polyhydric alcohols such as 1,4-buta/diol, 1,6-hexanediol, pentaerythritol, norbitol, glycerin, neopentyl glycol, 1,4-cyclohequinane dimethanol. A resin (Pylon 53S) that has improved affinity with polyester resins or magnetic particles obtained by modifying these polyester resins with 80 s Na or the like.

b) Perform radiation sensitivity modification using the method described in vk.

(1) Unsaturated polyester resin A polyester compound containing a curable unsaturated double bond in its molecular chain, such as an ester bond between a polybasic acid and a polyhydric alcohol as described as a thermoplastic resin in item (1). Examples include unsaturated polyester resin prepolymers and oligomers containing radiation-curable unsaturated double bonds in which part of the polybasic acid is maleic acid.

Examples of the polybasic acid and polyhydric alcohol components of the saturated polyester resin include the compounds listed in Section 1.
Examples of the radiation-curable unsaturated double bond include maleic acid and hexamaric acid.

The radiation-curable unsaturated polyester-fat is produced by a conventional method, that is, by adding maleic acid, 7''V acid, etc. to one or more polysalt or base acid components and one or more polyhydric alcohol components, that is, in the presence of a catalyst.
After dehydration or dealcoholization reaction in a nitrogen atmosphere at 80 to 200°C, the temperature is raised to 240 to 280°C, and 0.5 to 1
A polyester resin can be obtained by a condensation reaction of Hg under reduced pressure. The content of maleic acid and 7 fathoms of malic acid is
In view of crosslinking during production, radiation curability, etc., the amount of brewing ingredients is 1 to 407 mol, preferably 10 to 30 mol.

(g) Polyvinyl alcohol resin a) Polyvinyl alcohol, butyral resin, acetal resin, formal resin, copolymers of these components, etc. are mentioned, and □ these have good affinity with magnetic powder.

b) The hydroxyl groups contained in these resins are subjected to radiation sensitization modification by the method described later.

(V) Epoxy resin % phenoxy resin a) Epoxy resin by reaction of bisphenol chlorohydrin, methyl chlorohydrin 97C). Shell chemistry!
1 (Epicote 152,154°828.1001.1
007) Manufactured by Dow Chemical (DgNn 31.DER73
2, DRR511゜DM le 331) Dainippon Ink Ik (Ebikuron 400. Ebikuron 80
0). j! The above epoxy has a degree of I11 fat U.
Phenokine fat (PKHA, PKHC) manufactured by CC.

PKHH), Jl Copolymer of bulked bisphenol and epichlorohydrin Manufactured by Dainippon Ink (Evicron 1
4.5, 152, 153.1120) etc. are also effective.

CVDII fiber derivatives a) Am ligation derivatives of various molecular weights are also effective as the thermoplastic resin component of the present invention. Among them, particularly effective are nitrified cotton, cellulose acetophthylate, ethyl cellulose, methyl cellulose, acetyl cellulose and the like.

b) Activate the hydroxyl group in WIiI and perform radiation sensitization by the method described later.

(VI) Polyether resin Examples include ADEKABORIETHER P-700 and ADEKABORIETHER P as compounds containing one or more hydroxyl groups.
There are polyfunctional polyethers such as -1000, ADEKABORIETHER G-1500 (manufactured by Jiryuka Co., Ltd.), Polymeg 1000, and Polymeg 650 (manufactured by Forker Suit Co., Ltd.).

α-button polycaprolactone Examples thereof include polyfunctional polyesters such as polycaprolactone PCP-2000, polycaprolactone PCP-0240, and polycaprolactone PCP-0300 (manufactured by Chisso Corporation).

(IX), a) The low thermoplastic resins include thermoplastic rigid polyurethane resin, polyethereste lambda resin, polyvinylpyrrolidone resin, and 114 resin (PVP
The object of the present invention is also acrylic resins containing at least one kind of olefin copolymer), boria-bride arm, polyimide resin, phenol resin, spiroacecool resin, acrylic ester and methacrylic ester containing hydroxyl groups as one component. It is valid for ″.

b) The effect can be further enhanced by radiation sensitivity modification.

On the other hand, thermoplastic resins W&, or their polymers, oligomers,
Examples of telomers are as follows.

(I), N urethane resins and prepolymers and esters Examples of such urethane compounds include, as isocyanates, 2.4-) luene diisocyanate, 2.6-
tolunin diincyanate, 1.3-xylene diisocyanate, 1.4-xylene diisocyanate, 1,5
-Naphthalene diisocyanate, m-phenylene diisocyanate, P-phenylene diisocyanate, 3,3
'-dimethyl-4,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 3,3'-dimethylbiphenylene diisocyanate,
4.4'-biphenylene diisocyanate, hexamethylene diisocyanate, influorone diisocyanate, dicyclohexylmethane diisocyanate, Deromodul L, Desmodyl Ni, J' each polyvalent isocyanenite, linear saturated polyester (ethylene glycol, diethylene glycol, chrycerin) , trimethylol prepane, 1,4-butanediol, 1,6-hexanediol, pe/taerythritol, nluhitol, -neopentyl glycol, 1,4-cyclohexane dimetatool, and phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, condensation polymerization with saturated polybasic acids such as adipic acid, sebacic acid), linear saturated polyethers (polyethylene glycol, polypropylene glycol, polytetramethylene glycol) and cabbage. Polyurethane resins, prepolymers, and polymers made of condensation products of various polyesters such as polyester, hydroxyl-containing acrylonitrile, and hydroxyl-containing methacrylic ester are effective.

These soft resins may be directly combined with the radiation-sensitive modified thermoplastic resins, but j! It is very effective to modify the urethane resin to be radiation sensitive by reacting it with a monomer having an acrylic double bond or allylic double bond that reacts with the incyanate group or hydroxyl group at the * end of the urethane resin. be.

(II) Acrylonitrile-butadiene copolymer prepolymer with a terminal hydroxyl group, commercially available as polyBD liquid resin manufactured by Sinclair Petrochemical Co., Ltd., or manufactured by Nippon Cemen Co., Ltd. Hyker 14325 and the like are particularly suitable as a soft resin component in which the double bonds in Putaj and 2/M generate reradicals by radiation, resulting in crosslinking and polymerization. Further, those having a terminal hydroxyl group are effective in further increasing the radiation 1w sensitivity by adding an acrylic unsaturated double bond via diisocyanate or the like.

(To) Polybutadiene elastomer A prepolymer having a low molecular weight terminal hydroxyl group such as PolyBD Liquid Resin 几-15 manufactured by Sinclair Vetro Chemical Co., Ltd. is particularly suitable in terms of compatibility with thermoplastic resins and affinity with magnetic powder. be. Since the Ordinary 15 prepolymer has a hydroxyl group at the end of the molecule, it is possible to increase the radial arm sensitivity by adding an acrylic unsaturated double bond to the end of the molecule, and it can be used as a binder. It becomes even more advantageous.

In addition, polybutadiene cyclized product Nippon 5 Synthetic Rubber CBR
-M9 and Ol also exhibit excellent performance when combined with thermoplastic resins. In particular, cyclized polybutadiene is highly efficient in cross-polymerization by radiation due to radicals of unsaturated bonds inherent in polybutadiene, and has excellent properties as a binder.

Suitable low thermoplastic soft resins and prepolymers thereof include chlorinated rubber, acrylic rubber, isoprene rubber, and cyclized products thereof (ClR701 manufactured by Nippon Synthetic Rubber Co., Ltd.)
, epoxy-modified rubber, internally plasticized saturated linear polyester (Toyobo Byronna 300), and other soft XW resins are also more effective in the present invention if they are subjected to the radiation-sensitive modification treatment described below.

Specifically, radiation-sensitive modification is applied to acrylic double bonds such as acrylic acid, methacrylic acid, or their ester compounds, which have an unsaturated double bond with fusical polymerizability, and allylic double bonds such as diallyl fucrate. Radiation of heavy bonds, maleic acid, unsaturated bonds in maleic acid derivatives, etc.
It involves introducing into the molecule a group that undergoes cross-linking or polymerization and drying by M-rays.

In addition, any unsaturated double bond that undergoes cross-linking polymerization upon irradiation with radiation may be used.

As a method for radiation sensitivity modification with good KA, it is carried out as follows: 2) The above-mentioned thermoplastic resin or thermoplastic soft resin having one or more hydroxyl groups in one molecule, Prepolio-11C in one molecule.
I react the isocyanate groups of seven polyisocyanate compounds after the I molecule, and then react with one or more molecules of a monomer having a group that reacts with the isocyanate group and an unsaturated double bond having radiative hardening properties, for example, A salt obtained by reacting one molecule of toluene diisocyanate with one hydroxyl group of a saponified salt-vinyl acetate copolymer (VAGH manufactured by UCC), and then reacting one molecule of 2- with droxyethyl methacrylate. One example is wWiI, which is a vinyl acetate copolymer resin with an acrylic double bond in a bender shape.

In addition, the polyisocyanate compounds used here include 2.4-) toluene diisocyanate, 2.6-toluene diisocyanate, 1.3-xylene diisocyanate, 1.4-xylene diisocyanate, m-phenylene diisocyanate, and P-phenylene diisocyanate. Diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, desmodur L, fsmodur I
L (auto)” (manufactured by Izbayer), etc.

Monomers having a group that reacts with an isocyanate tote group and a radiation-curable unsaturated double bond include 2-hydroxyethyl ester of acrylic acid or methacrylic acid;
Esters with hydroxyl groups such as 2-hydroxyglobyl ester, 2-hydroxy, dioctyl colored ester; acrylamide, methacryl fumide, N-menalor! A monomer containing a strong acrylic double bond and has an active hydrogen that undergoes a 1.1 reaction with the isocyanation of lylamide, etc.! In the vine, allyl alcohol, Karein-polyhydric alcohol ester compound, substance, long 1I with unsaturated double bond
Also included are monomers containing unsaturated double bonds that have active hydrogen that reacts with iscyanate groups and have radiation curability, such as mono- or diglycerides of iIN fatty acids.

■A reaction product of one molecule of a substance containing one or more epoxy groups in its molecule and one or more molecules of a monomer having a group that reacts with epoxy groups and a radiation-curable unsaturated double bond, such as glycidyl methacrylate. A thermoplastic resin containing an epoxy group obtained by combining 1 radical is reacted with acrylic acid, and 1#! of a carboxyl group and an epoxy group is reacted. Through a ring reaction, resins, prepolymers, or oligomers with pendant acrylic double bonds are formed in the molecule, and radiation-curable unsaturated diamides are formed in the molecular skeleton through reaction with maleic acid and a chit-opening reaction between carboxyl groups and epoxy groups. Examples include myrit, prepolymers, and oligomers having multiple bonds.

Here, compounds containing one or more epoxy groups in the molecule include homopolymers of acrylic esters or methacrylic esters containing epoxy groups, such as glycidyl acrylate and glycidyl methacrylate, or copolymers with other monopolytic heptanomers. Thermoplastic - & (V)
11, Epicor) 828, Epicort 1001
．． There are various other types of epoxy resins such as Epicoat 1007 and Ebiko 1009 (manufactured by Shell Chemical Co., Ltd.).

Examples of monomers having groups that react with epoxy groups and radiation-curable unsaturated double bonds include acrylic polymers containing carboxyl groups such as acrylic acid and methacrylic acid, methylaminoethyl acrylate, and methylaminoethyl acrylate. In addition to acrylic polymers having primary or secondary amine groups such as methacrylate, maleic acid, fumaric acid and croton-1
Polybasic acid monomers having radiation-curable unsaturated binary bonds, such as polybasic acid/decylenic acid, can also be used.

One molecule of a compound containing 111 or more carboxyl groups in the melon molecule, a group that reacts with carboxyl groups, and radiation saponifiable property 1
A reaction product with one or more molecules of a monomer having an unsaturated double bond,
For example, glycidyl methacrylate is reacted with a thermoplastic resin containing carboxyl groups obtained by solution polymerization of methacrylic acid, and as in item Examples include Il fats, prepolymers, and oligomers with modified bonds.

Examples of compounds containing one or more carboxyl groups in the molecule include polyesters in the resins mentioned above that contain carboxyl groups in the molecular chain or at the end of the molecule; radicals such as acrylic alcohol, methacrylic acid, maleic anhydride, and foric acid; These include homopolymers of polymerizable monomers having carboxyl groups or copolymers with other polymerizable heptamers.

Examples of monomers having a group that reacts with a carboxyl group and a radiation-curable unsaturated double bond include glycidyl acrylate and glycidyl methacrylate.

In the present invention, the active energy source used to cross and enrich the first and second magnetic layers and the electron beam sourced from an electron beam accelerator are particularly useful for the reasons described below. Advantageously, it is also possible to use gamma-rays with a CO6@ source, I-strings with a 5rso source, and X-ray rings with an X-ray generator as a source.

As an irradiation source, electron beam accelerators are suitable for controlling the absorbed dose, self-shielding ionizing radiation for introduction into the production line, and ease of connection with sequence control with process line equipment. It is advantageous to use it.

Conventional electron beam accelerators include Kotscroft type,
Various types of accelerators have been put into practical use, mainly due to the difference in the method of obtaining high voltage, such as the punch graph type, resonant transformer type, iron core insulated transformer type, and linear accelerator type.

However, magnetic recording media can be used for general purpose applications with a
Electron beam accelerators with a low accelerating voltage of 300 KV or less are unnecessary, and the high accelerating voltage of 100 OKV' or more normally used in the above-mentioned accelerator is unnecessary. is sufficient. Such a low accelerating voltage accelerator is advantageous not only in the reduction of the current of the system itself, but also in terms of the 1 m shielding of ionizing radiation. The standards as shown in the table below have been reported regarding whether the shielding film should be made of lead or concrete, and its shielding thickness (Received Radiation Axis Utilization Study Group Report 8, 1979 August 9th). Japan Atomic Energy Association wk).

As shown in the table 5 above, at Shimako beam accelerating voltages of 300 KV or less □, leakage
- can be sufficiently blocked.

For this reason, there is no need to separately provide an expensive electron beam irradiation chamber, and one irradiation system can be incorporated into the magnetic recording media manufacturing line/I system, thus allowing the drying and curing process of magnetic recording media using electron beams. Bring it online =
-It becomes possible to

Examples of such specific systems include the low-volume electron beam accelerator (Lectro Curtain System) manufactured by Energy Sciences, Inc. of the United States, and the self-closing scanning type accelerator manufactured by Hori-Murphysics of Germany. A dose type Kiko anti-accelerator is a suitable example.

In addition, for radiation crosslinking, N, gas, Hθ gas, ■
It is important to irradiate the recording medium with radiation in an inert gas flow such as magnetic gas, and the magnetic coating film has a very high degree of magnetic filling. Since 11~・ms is extremely porous, irradiation with radiation in the air is effective because radicals generated in the polymer due to the influence of Ol etc. generated by radiation irradiation are effective when concentrating the binder components. It inhibits the structural reaction.

Since the surface of the magnetic layer is, of course, porous, the inside of the coating is also affected by the surface of the magnetic layer.

Therefore, the atmosphere of the area to be irradiated with active energy rays is
% with an oxygen concentration of up to 1% N,,Nθ.

It is important to maintain an inert gas atmosphere such as CO1.

Polymerization of 'Ik film by electron beam, crosslinking density is 10 Mrad
However, the absorbed dose in the second layer is 5 MrB (
If it exceeds 1, the amount of magnetic film deposits on the head will increase, which is not very preferable. At an absorbed dose of 0.5 to 5 Mrad, the density of polymerization and crosslinking by the electron beam is appropriate, so the magnetic coating has an appropriate balance between flexibility and rigidity, and the wear resistance between the magnetic layer heads is also improved. However, there is no head adhesion, vibrator/roller adhesion, or other adhesion, making it an excellent magnetic recording medium.

In the combination of the above-mentioned radiation-sensitive modified resin and radiation-sensitive soft resin or its prepolymer, radiation-sensitized modification of the resin component with a high elastic modulus increases the degree of crosslinking of the binder and increases the hardness of the magnetic coating film. High and rigid, the coating film becomes brittle, resistance, purity, roughness, etc. is low, and a thermoplastic resin suitable for 6° magnetic cape has the appropriate flexibility required. It is effective in that it
As a result of the above, the polymerization/crosslinking density becomes appropriate, and the material has a balance between flexibility and leakage property. On the other hand, since thermoplastic resin has appropriate flexibility, it is of course possible to combine it with radiation-sensitive soft resin.

In this case, in order to satisfy the above requirements, the mixing ratio of the thermoplastic resin and the radiation-sensitive resin should be 8:2 to 2:8.
A ratio of is particularly desirable.

As substrates used for coating, polyethylene terephthalate films, which are currently widely used as substrates for magnetic recording media, and for applications requiring further heat resistance, polyimide films, boria-imide films, etc. are active, and in particular In the case of polyester-based films, uniaxial abrasive stretching or biaxial abrasive elongation processing is often applied to thin films.

The magnetic fine powder used in Himi 11 is γ-Fe, 0.
, Fe・Oa, Co-doped r-Fe coating 0. , Co doped r-Fe Dew Om-Faρ4 solid solution, Cry,
CO-based compound adhesion reservoir y -Fe@0B, Co-based compound adhesion type F6J104 (r -F・Also includes an intermediate state with 0. Also, the CO-based compound mentioned here refers to cobalt oxide, cobalt oxide, Cobalt ferrite, cobalt ion@9!i products, etc. show the use of cobalt's magnetic anisotropy to improve coercive force.) This radiation-curable binder for magnetic recording media is also commonly used in such applications. Various antistatic agents,
It is effective to use dispersants, coating strength additives, etc. as appropriate depending on the application.

In the binder of the present invention, even a solvent-free resin that does not use a solvent can be used because it can be cured in a short time, but generally a solvent is used. When using a solvent, heat curing isocyanates such as esters, ethyl acetate, butyl acetate, ethyl acetate, butyl acetate, methanol, ethanol, isopropanol, butanol, etc. Alcohols that cannot be used in the conventional method, those having an ether bond such as tetrahydropone and dioxane, solvents such as dimethylformamide and vinylpyrrolidone, and aromatic hydrocarbon diluents or solvents such as toluene and xylene are used.

As explained above, in the first layer of the present invention, magnetic powder having a coercive force within a specified range is mixed with appropriate additives if necessary, and a binder that crosslinks and polymerizes by irradiation with radiation. A magnetic paint is prepared. To prepare these components for the magnetic coating material, various apparatuses such as a ball mill, a compact grind mill, a roll mill, a high-speed impeller disperser, a homogenizer, and an ultrasonic disperser may be used.

The magnetic paint thus prepared is coated on a substrate according to the conventional method, and after alignment of magnetic particles, solvent drying, and surface smoothing treatment, the thickness of the first magnetic layer is 2.1 to 2.2 mm, as described below.
．． It is irradiated with Kt rays to make it 8μ fake.

After forming the first magnetic layer, a second magnetic layer is formed in the same manner.

In the present invention, the thickness and coercive force range of the irises and second magnetic MK formed as described above, as well as the magnetic powder content of the first magnetic layer, are determined by the advantages of radiation curing of the first and second layers. In addition, there is little output fluctuation in the midrange, and there is no output fluctuation or drop in the low or high range! The fabric magnetic recording medium should be 6300a and the thickness should be 2.1 to 2.8 μm, and the magnetic powder content should be 81.8% or more. The second magnetic layer has a thickness of 2.1 μm or more and a coercive force range of 516 to 8
000e.

When the second magnetic layer on the first magnetic shoulder is applied to a certain degree of thickness, the shadow 1 of the surface unevenness on the first magnetic layer is reduced.
It has been confirmed by the present applicant regarding conventional two-layer coated magnetic recording media that a two-layer coated magnetic recording medium with less output fluctuation at high frequencies can be obtained. The applicant of this case has informed the official that (!) at a low frequency of 8 KHz, the second magnetic layer thickness is 1.5 μm or more, and at a high frequency of 16 Kt (z), the output fluctuation is 0.5 (at a high frequency of 2.1 μm or more) IB or less, it is desirable to select the second magnetic layer thickness to be 2.1 μm or more (if the content of magnetic powder in the magnetic layer is 81.8≦ or more, the thickness 2.1~2゜8μ
Sufficiently good low frequency characteristics were obtained in the wind range, with a rating of 2.8
If the value exceeds μm, the overall holding power will decrease, and the low frequency response will improve, but if the midrange becomes distorted, there will be a drawback, so it has already been established that it is desirable to set the value to 2.1 to 2.8 μm. I've confirmed it. In the present invention, it has been found that it is good to follow the above proposal.

In addition, in the present invention, the binder in the first magnetic layer is cured or polymerized by radiation, so that the coercive force that could previously be used only up to 5900e has increased to 63.
It turned out that it can be used up to 00e. Therefore, the range in which the coercive force of the first magnetic layer can be used is expanded further than in the past, and therefore a magnetic recording medium with even less distortion in the low frequency range can be obtained. This is thought to be due to the fact that the network structure of the binder polymerized by radiation irradiation is different from that of conventional binders.

Thus, the present invention provides, in combination with the use of a radiation-curable binder in the first and second magnetic layers and the control of the coating thickness, coercivity, etc. of the first and second magnetic layers,
It is possible to manufacture a high-quality magnetic recording medium with less output fluctuation or decrease than before and no sagging in the middle range under a streamlined production process. This is because conventional tapes that use isocyanate compounds to undergo a crosslinking reaction by heating are mixed with the isocyanate compound as a hardening agent and begin to react with the hydroxyl groups in the binder. After drying, the crosslinking reaction in the binder rapidly progresses, and the paint film hardens over time due to the progress of the framework reaction, causing output fluctuations due to a decrease in surface formability. Although radiation-sensitive resin is used') K: t+l゛?t! After surface molding-1, crosslinking by radicals generated by electron beam irradiation progresses, resulting in output fluctuation due to decrease in surface shelf life due to pot life of magnetic paint. This is due to the fact that it does not cause deterioration and also removes the restriction on output nutation due to the deterioration of surface shelf life due to the time left after application.

The upper limit of the coercive force of the first magnetic layer is expanded to 6300e by using the axillary radiation sensitive resin, thereby eliminating the sagging in the midrange.

Furthermore, it is advantageous for the magnetic recording medium to be used to select a combination within the coercive force range H of the first layer and the second layer in which the IK% is determined. In that case, the first layer and the second layer are formed such that the coercive force range of each of the first layer and the second layer is proportionally lowered depending on the coercive force of the magnetic tape used. For example, in a recording device of 3500e or higher, the following combinations are used.

1st layer 2nd layer (11400~6300e 590~8000s (
21380~6000e 560~7600e (3
) 3'50-5500e 510-7000e Examples of the present invention will be shown below, but first a synthesis example of a radiation-sensitive binder will be presented.

&) Synthesis of acrylic modified resin of vinyl chloride and vinyl acetate (radiation sensitive modified resin) VINYLITE VAGH7
50 parts and 1250 parts of toluene, cyclohexanone soo
Pour 514 grams into a Lough flask, heat and dissolve, and raise the temperature to 80°C Ditolylene diisocyanate-human 0J? Diethyl methacrylate adduct (see notes below for manufacturing method) at 61
．． Added 4 parts of tin octylate, further added 0.012 parts of tin octylate, 0.012 parts of hydroquinone, and heated at 80°C.
The reaction is allowed to occur until the CO reaction rate reaches 90% or higher.

After the reaction is completed, the mixture is cooled and diluted with 1250 parts of methyl ethyl ketone.

(Note:) Preparation of 2-hydroxyethyl methacrylate (21 (gMA) adduct of lylene diisocyanate) (TDI) 348 parts of nitrilene diisocyanate was heated to 80°C in a 4-lj flask in an air stream of N. After □, 2-hexaethylene methacrylate 260s, tin octylate 06
After dropping 0.07 parts and 0.05 g of Hydroquino Y while keeping a cooling condenser so that the temperature inside the reaction vessel is 80 to 85'', the mixture is stirred at 80°C for 3 hours to complete the reaction. After taking it out and cooling it, 2H of TDI becomes a white paste.
Obtained HMA. ) Buti Tool Resin Sekisui Chemical BM-81
00 parts toluene 191.2s, cyclohexano 771
．． Pour 4 parts into 514 Lof flasks and heat to dissolve at 80°C.
After raising i1, 7.4 parts of 2-hydroxyethyl methacrylate adduct of the tolylene diinocyanate was added, and further 0.015 s of tin octylate, hydroquinoyo, 01
Add 5 parts of NCO at 80°C, and the reaction rate of NCO in the air stream is 90%.
Let it react until it reaches the above level.

After the reaction is completed, it is cooled and diluted with methyl ethyl ketone.

Add 100 parts of Toyobo's Vipun RV-200 to 11 parts of toluene.
6 parts, 1 tam of methyl ethyl ketone <dissolved by heating at 80°C
After raising the temperature, add 3.55 parts of the TDI ZHEM Muaduct, add 0.007 parts of tin octylate, and 0.0 parts of heidoshiquinone.
07 parts was added and the NCO reaction rate was 90% at 80°C in a N6 stream.
Let it react until it reaches the above level.

Epicoat 1007 4008 manufactured by C.L. Chemical was added to 50 parts of toluene and 50' parts of MEK and dissolved, followed by 0.006 parts of NN-dimethylbenzylamine and 0.00 parts of hydroquinone.
003 parts were added, the temperature was raised to 80°C, 69 parts of acrylic acid was added dropwise, and the mixture was allowed to react at 80°C until the oxidation level was 5 or less.

Terminal incyanate diphenylmethane diisocyanate (MDI) group urethane prepoly! - (Nipporan 4040 manufactured by Nippon Polyurethane) 250 m.

2HEMmu 3245 parts, Hydrokino 70.07 parts,
Put 0.0-09 parts of tin octylate into a reaction can, heat and dissolve at 80°C, then drop 43.5 parts of TDI into the reactor while cooling to a temperature of 80-90°C. The reaction was allowed to occur at ℃ until the NCO reaction rate reached 95% or higher.

f) Polyether yarn end urethane modified elas) Madomer) Polyether PTG-50025 manufactured by Nippon Polyurethane Co., Ltd.
0 parts, 2HEMA 32.5ftB, high)" Loki/70.007 parts and 0.009 parts of tin octylate were placed in a reaction can and heated to 80°C and dissolved, then 43.5 parts of TDI was added until the temperature inside the reaction can was 80-90. The solution was added dropwise while cooling to a temperature of 1.5°C, and after the addition was completed, the reaction was allowed to proceed at 80°C until the NCO reaction rate reached 95 or higher.

Low molecular weight terminal hydroxyl group polybutadiene polybutadiene BD liquid resin R-15250 parts, manufactured by Sinclair Petrochemical Co., Ltd. (2) (gMA 32.5 parts, hydride tetraquinone 0.00
Put 7 parts and 0.009 parts of octyltin into a reaction can, and add 80 parts of octyl tin.
After heating and dissolving 43.5 parts of TDI at ℃, the temperature inside the reaction vessel was 8.
It is added dropwise while cooling to a temperature of 0 to 90°C, and after the dropwise addition is completed, the reaction is allowed to occur at 80°C until an NC0 reaction and a reaction rate of 95 or higher are achieved.

(TDI-allyl alcohol adduct) TDI
348@fj (N, after heating at 80"CK in an air stream, add 1161 m of allyl alcohol, 0.07 part of soot octylate, and 0.02 part of Hydreki 1F to a temperature of 80 to 85° in the reaction vessel.
The mixture was added dropwise while controlling the cooling so that the reaction temperature was 30° C. After the addition was completed, the mixture was stirred and reacted at 80° C. for 3 hours.

(* Lipid synthesis example) 2-human-xyethyl acrylate (2HEA) 15s
, 35 parts of butyl methacrylate, 37.5 g of toluene,
Put 37.5 parts of MEK into a reaction can, heat to 80'C, and add 105 g of ZHE Mu 45s1 (butyl methacrylate).
, 6 parts of benzoyl peroxide BPO, 11 parts of toluene
2.5 parts were added dropwise and reacted at 80 to 790°C for 4 hours, and 195 parts of the reaction product kTDI-allyl alcohol adduct: 46.611 parts were added, followed by 0.01 tin octylate.
Add 70.01 parts of hydroquino and allow to react at 80°C until the NCO reaction rate reaches 90% or more.

1) Unsaturated polyester, 1EBC resin synthesis example Dimethyl sepatate 13611, Dimethyl adipate 12.2
1, 64.8 parts of dimethyl maleate, 73 parts of neopene glycol, 74 parts of 1,6-hexanediol, and 10 parts of tetra-n-butyl titanate were charged into a reaction vessel and N3
240-260 after demethanol reaction at 180″C in air flow
The temperature was raised to 'C, and a condensation reaction was carried out under reduced pressure of 0.5 to 1 Hg to obtain a resin similar to an elastomer with internal layer formation.

Example 1 Cobalt-coated acicular γ-Fe, O @ 100 parts Acrylic double bond-introduced salt-vinyl acetate copolymer 10 parts (solid content equivalent)
Acrylic double bond-introduced polyether phrethane elastomer 10s (2) (converted to form) Dispersant (refined soybean lecithin) 4 parts Methyl ethyl ketone 80 parts Methyl isobutyl ketone 8011 Toluene 80 parts A mixture of the above composition was heated in a ball mill for 24 hours. The mixture was kneaded, spread on a bodaester film, and after orientation of the magnetic particles, solvent drying, and surface smoothing treatment, the mixture was heated so that the thickness of the magnetic layer was 2.1 μIIIK. The content of magnetic powder is 83.41 and the coercive force is 5900.
It was e. The coating film was cured by irradiation with an electron beam in a N gas atmosphere using a telecurtain type electron beam accelerator under the conditions of an acceleration voltage of 150 KsV, an electrode current of 10 m, and an absorbed dose of 5 Mrad.

Next, a magnetic paint with the following composition was applied to coat the second magnetic layer: Cobalt-coated acicular 1-Fa @ 0.100 parts Salt-vinyl acetate copolymer with acrylic double bonds introduced Acrylic double bonds Introduction Urethane Ethstomer-10 partial dispersant (refined soybean lecithin) ls Methyl ethyl ketone 10011 Toluene 150s This magnetic paint was coated on the first layer under the same conditions as for the first layer and irradiated to form a two-layer coated magnetic coating. Got the tape. The coercive force of the second magnetic layer is 68008 mm [thickness is 2.2
It was a μ proverb.

Comparative Example 1-1 To coat the Kllll layer on the first radiation-cured magnetic layer in Example 1, the following thermosetting magnetic coating was prepared: Cobalt coated 7Fe, 0. 100 parts Vinyl chloride-vinyl acetate copolymer (Vjin GH manufactured by UCC) 15 parts Utsutangre polymer (manufactured by Nippon Urethane Co., Ltd. -2304) 1
016 Dispersant (refined soybean lecithin) 1 part methyl ethyl ketone 100 parts methyl imbutyl ketone 100% toluene A mixture of 100 parts or more was kneaded in a ball mill for 48 hours, and then 4 parts of Nippon Polyurethane Co., Ltd. (Ronate L) was mixed as a crosslinking agent. After coating this paint, orientation treatment of magnetic particles, solvent drying treatment, and surface treatment, the thickness was 2.5 mm. ．． I ran a 5K that was worth 2μ. The coercivity of the second magnetic layer was 68QOe.

Comparative Example 1-2 Cobalt-umbral needle-like y-Fe, 0.
100s vinyl chloride-vinyl acetate copolymer (V
AG&) 10 parts urethane polymer (Japan Polyurethane (
Co., Ltd.2304) 10i1i Dispersant (purified soybean lecithin) 4
Part Methyl Ethyl Ketone 80 parts Methyl Isobutyl Keto 7 80s Toluene 80 parts The mixture of the above composition was mixed for 24 hours, then 3 parts of Coronet) L was mixed as a cross-crossing agent, and heated at a temperature of 0°C for 48 hours after increasing Kmm as before. A first thermoset magnetic layer was formed. Thereafter, a thermosetting magnetic layer was also formed using the same coating material for the second magnetic layer as in Comparative Example 1-1.

High range output reduction test due to pot life Example 1 and Comparative Example 1 - Output at high range 16KI-11 due to pot life of paint for IK, that is, those whose second magnetic layer is radiation curing type and thermosetting type. We investigated the decline.

The results are shown in Figure 1 (roll). As shown in Figure 1, the use of a binder that is cured or polymerized by radiation eliminates the problem of low output at high frequencies.

Output fluctuation test at low range due to pot life Regarding Example 1 and Comparative Example 1-2, the first magnetic layer was of radiation curing type and thermosetting type, and the output fluctuation test at low range of IKHz and 3 & A test was conducted on output fluctuations, and the results shown in Figure 1(b) were obtained. As the pot life of the magnetic coating material progresses, the magnetic recording medium using the thermosetting binder of Comparative Example 1-2 exhibits similar output fluctuations at both IKHz and jKH2, whereas the radiation output of Example 1 The magnetic recording medium of the present invention using a hardened binder does not exhibit any problems with output fluctuations.

Head adhesion test by pot life In the case of conventional isocyanate-based binders, if the pot life of the magnetic paint is too long, the surface moldability will decrease and the amount of head adhesion will increase when actually running on an audio deck, which is not desirable. It became clear that there was no such thing. The head adhesion status of Actual Example 1 and Comparative Example 1-1 was determined by visual inspection using a 5-point scale as shown in the following table: After storage for one week in an environment of 60°C and 80% relative humidity. When measuring the tension of the samples of Example 1 and Comparative Example 1-1, if the former is taken as 100%, the latter has a pot life of 2.
It was 150≦ for hours. Therefore, it can be seen that the present invention causes less curling phenomenon. It has the highest stability against environmental conditions such as temperature, which is caused by the leaching of low-molecular components contained in the magnetic coating film. III indicates good results.

Example 2 Cobalt-coated acicular r Fe40.100 parts Acrylic double bond-introduced butyral resin 8 parts (in terms of solid content) Acrylic double bond-introduced urethane elastomer) 12 parts (-
) Dispersant (refined soybean lecithin) 5 parts methyl ethyl) y 120 parts toluene
When a mixture having a composition of 100 parts or more was irradiated with an electron beam in a N gas atmosphere under the conditions of acceleration 11 = OKV, N voltage detection R 20 mA, and absorbed dose 10 Mrad in the same manner as in Example 1-1. The coating film was cured with K and K to form a first magnetic layer. The coercive force of the first magnetic layer was 5600e, and the thickness of the first magnetic layer was 2.8μ.

Next, a paint for the second magnetic layer was prepared with the following composition: Cobalt-coated acicular γFe, Ogioo part, acrylic surface, double bond-introduced epoxy resin 13 (converted to m-type part)
Acrylic double bond introduced polybutadiene elastomer 12
Part (l) Dispersant (refined soybean lecithin) 1 part methyl ethyl ketone 150 parts toluene
After applying 100 copies of this paint onto the magnetic layer, it was irradiated with an electron beam using an electron AT accelerator under the conditions of an acceleration voltage of 150 KV, an electrode current of 10 m, and an absorbed dose of 5 Mrad in a N,J atmosphere. , the coating was cured. The coercive force of the irises dimagnetic layer was 6500θ, and the coating thickness was 2.1μ rich.

Example 3 In this example, one of the second magnetic layers is made of thermoplastic resin.

2. Using the same magnetic paint as the first required magnetic paint in Example 2.
After forming the first layer of 3 μm 1 lk thickness and 6300e coercivity, the coating for the second magnetic layer of the following setup was prepared and applied over the first layer.

Cobalt-coated acicular γ-Fe, 01 1
00 parts acrylic di-I bonded polyether cretan elastomer - 12 parts powder (soybean purified lecithin) 1 part methyl ethyl ketone 120 parts toluene
The coating film was cured by irradiation with an electron beam in a town gas atmosphere under Mrad's conditions. The first magnetic layer formed had a thickness of 2.6 μm and a coercive force of 720 Oe.

(Note) The vinyl chloride-vinyl alcohol copolymer used as a raw material in the above examples was prepared as follows: The vinyl chloride group/vinyl acetate group ratio was 75/25, and the vinyl chloride/vinyl alcohol copolymer was
xt+degree n=4Qo vinyl chloride-fhl! A vinyl copolymer is used as a raw material, and this is suspended in a mixed dispersion medium of water and a liquid agent such as MIBK (methyl inobutyl ketone), and then mechanically dispersed using a stirrer or the like, resulting in a suspension similar to a slurry in which the resin is swollen. create turbidity.

Next, sodium sodium methylate is added as a catalyst, and the temperature is maintained at around 80°C to saponify the acetyl groups of vinyl acetate to hydroxyl groups.

In addition, a stabilizer to prevent dehydrochlorination or a suspending agent to uniformly suspend the solution may be used.

Next, acetic acid and catalyst generated from the released acetyl groups are removed by washing the saponified slurry with water,
Increase the stability of resin. In this case, if necessary, a decoloring step for removing chlorine ions and the like may be added in order to eliminate the coloration during saponification.

The vinyl chloride-vinyl alcohol copolymer obtained by the saponification method 1m described above had the following properties.

Vinyl chloride group 87% Vinyl acetate group 03% or less Vinyl alcohol group 12.6≦ Degree of polymerization 330 When a thermoplastic resin is used in combination as in Example 3 of the running durability test, K
It has been confirmed that it is beneficial in terms of running durability, especially at high temperatures, because it imparts a more appropriate level of flexibility. Figure 2 shows the test results, and Example 3 in which a thermoplastic resin was combined was compared to Example 1 in which only a radiation-sensitive resin was used.
It can be seen that the running durability is more excellent. However, when compared with Comparative Example 1-1, Example 1 also has much better running durability. In Comparative Example 1-1, the one with a pot life of 10 hours had poor runnability, and the run became streaky in the middle. This may also be due to environmental conditions such as temperature and leaching of low molecular weight components contained in the magnetic coating film due to excessive pot life.

In Example 3, it was found that head adhesion was good at 5 Mrad or less.

As shown in the characteristic test fJh3 in the wave number range for all Examples 1 to 3, all had remarkable improvement in frequency characteristics at all frequencies and showed excellent results. 1.3K)
L! The output fluctuation in the low range was not affected by the paint pot life and was within 0.5 aB.

Example 4 In the second magnetic layer, radiation-sensitive W resin, thermoplastic*m
and a radiation-sensitive soft wN.

Cobalt deposition ri;'e, o, 100
Radiation sensitivity of polyvinyl alcohol resin
7 parts epoxy [316 parts acrylic double bond introduced urethane elastomer]
12-part powder (refined soybean lecithin)
1 part methyl ethyl ketone 12
0 parts Toluene 100 parts Example 3 and the first and second layers were prepared in the same manner. In this case, running durability was also superior to the combination of only radiation-hg responsive resins, and there was no problem with output fluctuations in the low range of 1.3 KI (z), making it excellent over the entire frequency range.

As explained above, the present invention makes it possible to further automate and speed up the production process, and also to
This product solves the quality problems associated with coated tapes, such as fluctuations in low-frequency output, decreased high-frequency output, and sagging in the midrange, and makes an important contribution to this industry.

[Brief explanation of the drawing]

Figure 1(a) is a graph showing the relationship between pot life and high frequency output reduction, Figure 1(b) is a graph showing the relationship between pot life and low frequency output fluctuation, and Figure @2 is a graph showing the relationship between pot life and low frequency output fluctuation. FIG. 3 is a graph showing running durability in Examples and Comparative Examples, and FIG. 3 is a graph showing overall frequency characteristics of Examples 1 to 3 of the present invention. Inventor Masaharu Nishimatsu, Tokyo Denki Kagaku Kogyo Co., Ltd., 13-1 Nihonbashi-chome, Chuo-ku, Tokyo Inventor Yukihiro Isobe □ Tokyo Tokyo Denki Kagaku Kogyo Co., Ltd., No. 1, 13 Nihonbashi-chome, Chuo-ku, Tokyo Inventor: Osamu Shinoura. Tokyo Denki Kagaku Kogyo Co., Ltd., 13-1 Nihonbashi-chome, Chuo-ku, Tokyo Inventor Hiroshi Kawahara Tokyo Denki Kagaku Kogyo Co., Ltd. 13-1 Nihonbashi-chome, Chuo-ku, Tokyo Inventor Toyo Ink Mfg. Co., Ltd. Tokyo 2-3-13 Kyobashi, Chuo-ku

Claims (1)

[Claims] 1) A first magnetic layer on a non-magnetic support and a second magnetic layer provided on the first magnetic layer, wherein both the first and second magnetic layers are free from radiation. A magnetic recording medium characterized in that it uses a binder that crosslinks and polymerizes upon irradiation. 2) The binder is a radiation-sensitive resin having a radiation-sensitive unsaturated double bond and (also Fi) thermoplastic**, and a radiation-sensitive soft resin having the double bond or its prepolymer, oligomer, or hysteromer. A magnetic recording medium according to claim 1, comprising: 3) The magnetic recording medium according to claim 2, wherein the radiation-sensitive unsaturated double bond is an acrylic double bond, a maleic double bond, or an allylic double bond. 4) The magnetic recording medium according to claim 1, wherein the content of magnetic powder in the first magnetic layer is 81.8 or more. 5) The magnetic recording medium according to claim 1, wherein the radiation irradiation is carried out in an inert gas atmosphere using an electron acceleration amount of 150 to 300 kY. 6) The first magnetic layer is 350 kY. Patent r# seeking having a coercivity in the range of ~6300s and a thickness of 2.1-2.8μm, and the second magnetic layer having a coercivity in the range of 510-8000e and a thickness of more than 2.1μm. The magnetic recording medium according to claim 1. □7) *-The magnetic recording medium according to claim 6, wherein the magnetic layer has a coercive force of 400 to 6,300e, and the second magnetic layer has a coercive force of 590 to 80,000. Magnetic recording medium/body. 8) The magnetic recording medium 0 according to claim 6, wherein the first magnetic layer has a coercive force of 380 to 6000 s, and the second magnetic layer has a coercive force of 560 to 7600 s. 9) The magnetic recording medium according to claim 6, wherein the magnetic layer has a coercive force of 350 to 5,500 Oe, and the second magnetic layer has a coercive force of 510 to 700 Oe.