JPS58166534A - Magnetic recording material - Google Patents

Abstract

PURPOSE:To enhance the durability and S/N ratio, by forming mutually cross- linkable network bond in a binder consisting of a flexible polymer and an oligomer having radiation sensitive groups by irradiation. CONSTITUTION:A resin component consisting of 30-90wt% flexible polymer having >=20,000 weight average mol.wt. and >=10% elongation at the time of breaking under tension and 70-10wt% oligomer having >=2 radiation sensitive groups in one molecule is used as a binder. A coating contg. the binder, dispersed particles of a magnetic body and an org. solvent is applied to a substrate, oriented in a magnetic field, and dried to remove the solvent. The resulting layer contg. the magnetic body is smoothened by pressurization and cross-linked by irradiation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording material that has excellent durability and a low S/N ratio.

In recent years, as the applications of magnetic recording materials have expanded, there has been a desire to develop magnetic recording materials with excellent durability and a high S/N ratio, especially in the fields of video, audio, and computer memory. There is a strong need to improve such quality.

For example, contact with a magnetic head can cause abrasion of the magnetic tape and deteriorate its magnetic properties.To improve this, it is necessary to improve the abrasion resistance of the magnetic binder and reduce the frictional resistance of the magnetic recording material. However, improvements in both abrasion strength and frictional resistance are often contradictory, and further improvements are desired in the running durability of magnetic recording materials such as magnetic tapes.

On the other hand, there is a constant demand for improvements in the S/N ratio in order to improve magnetic recording density, sound quality, and both picture quality.
Many attempts have been made to improve the properties of the magnetic particles, dispersion of the magnetic particles, selection of the binder, and surface smoothing treatments such as calendering. When trying to improve durability during repeated running, etc., smoothing in one calendering process tends to be defective, and it is often difficult to improve durability and S/
It has become difficult to simultaneously improve the N ratio.

The inventors of the present invention have made intensive studies to improve the drawbacks of the above-mentioned conventional techniques, and as a result have completed a magnetic recording material that is excellent in both durability and S/N ratio.

That is, in the present invention, (A) the weight average molecular weight is 20.0.
00 or more and a tensile elongation at break of 10 inches or more; and (B) 70 to 10% by weight of an oligomer having two or more radiation-sensitive groups in one molecule. An organic solvent-containing paint in which the resin component is Vicidar and one magnetic particle is dispersed is applied to the base material, and after being applied in a magnetic field, the solvent is dried and removed, smoothed by pressure, and the surface is irradiated with radiation. A magnetic recording material characterized in that it is produced by crosslinking a fragment-containing layer.

The above (A3) flexible polymers used in the present invention include 4/e, -, polyurethane resin, polyester I (fat), polycarbonate resin, polyamide II!, polyacrylate resin, polyvinyl butyral resin, polyvinyl chloride. Examples include pattern resin and phenoxy resin, and any of these flexible polymers may be used as long as the h-lid average molecular weight is 20.000 or more and the elongation at tensile break is 10 modulus or more. Particularly preferred are polyurethane resins having urethane bonds in the chain, and the polyurethane resin may also contain ester bonds, ether bonds, urea bonds, amide bonds, carbonate bonds, imide bonds, etc. in the main chain.

The weight average molecular weight of the flexible polymer (C) above is a polystyrene equivalent value determined by gel permeation chromatography, and it is particularly preferable that the weight average molecular weight is 40.000 F or less; If it is less than 0.000, the above-mentioned durability decreases and it is unsuitable for the present invention.

Moreover, the elongation at tensile break of the flexible polymer (A) above is:
This is the elongation when broken using a tensile tester for measuring tensile strength. A value of 20 inches or more is particularly suitable, and if it is less than 10 inches, cracks may occur due to bending or twisting when using a film-like base material. This is inappropriate.

The above (B) oligomer having a radiation-sensitive group used in the present invention is a low molecular weight resinous compound having two or more ethylenically unsaturated double bonds in one molecule, each having an unsaturated double bond. is preferably an acryloyl group or a methacryloyl group, and the molecular weight is preferably s, ooo or less, especially 5
It is preferable that it is 00-2000.

Preferred oligomers having a radiation-sensitive group (B) include, for example.

(1) Ethylene glycol, diethylene glycol, polyethylene glycol, flopylene glycol, dipropylene glycol, polypropylene glycol, butanediol, polytetramethylene glycol, hexanediol, tecanediol, neopentyl glycol, trimethylbentanediol, trimethylol Ester compounds of polyhydric alcohols and unsaturated carboxylic acids such as ethane, trimethylolpropane, pentaerythritol and trishydroxyethyl isocyanurate, succinic acid, adipic acid, sebacic acid, dodecanoic acid, phthalic acid, trimellitic acid, Maleic acid, fumaric acid, itaconic acid, pyromellitic acid, tetrahydrophthalic acid, hexahydrophthalic acid, methyltetrahydrophthalic acid, methylhexahydrophthalic acid, hymic acid, methylnasic acid, butanetetracarboxylic acid and tricarboxyethyl Polybasic acids such as isocyanurates, hydroxy-containing unsaturated monomers such as hydroxyalkyl acrylates, hydroxyalkyl methacrylates, glycidyl acrylate, glycidyl methacrylate, β-methylglycidyl acrylate, β-methylglycidyl methacrylate, etc. Ester compounds obtained by reaction with glycidyl-containing monomers, reaction of terminal hydroxy or terminal carboxyl group oligomers obtained by esterification reaction of the above polyhydric alcohol and polybasic acid with the above monomers (2) Ester compounds obtained by the reaction of polyhydric phenols such as bisphenol A, novolac phenol, cresol novolac phenol, impropenylphenol, and resorcinol with epichlorohydrin. an addition compound of a polyvalent epoxy resin and an unsaturated carboxylic acid, an addition compound of a polyvalent epoxy resin and an unsaturated carboxylic acid obtained from the reaction of the above-mentioned polyhydric alcohol and epichlorohydrin, an addition compound of the above-mentioned polybasic acid and epichlorohydrin; Addition compounds of polyhydric epoxy resins and unsaturated carboxylic acids/acids that can be reacted with; Addition compounds of polyvalent epoxy resins with epoxidized double bonds and unsaturated carboxylic acids, addition compounds of polyvalent epoxy resins and unsaturated carboxylic acids that can react with incyanuric acid and epichlorohydrin, aniline, xylylene diamine , meta-xylene diamine, meta-phenylene diamine, an addition compound of a polyvalent epoxy resin obtained from the reaction of an aromatic amine with epichlorohydrin, and an unsaturated carboxylic acid, haloxybenzoic acid, aminophenol, etc. Addition compounds of polyhydric epoxy resins and unsaturated carboxylic acids obtained by the reaction of epichlorohydrin with active hydrogen compounds (these are referred to as epoxy radiation-sensitive oligomers), (ro) tolylene diisocyanate, metaphenylene diisocyanate, naphthylene diisocyanate. Isocyanate, hexamethylene diisocyanate, inphorone diisocyanate, hydrogenated metaphenylene diisocyanate, terminal polyincyanate compound obtained by polycondensation with polyvalent incyanate, obtained by reaction of the above polyvalent incyanate compound with water A compound obtained by reacting a polyvalent incyanate such as a terminal polyvalent incyanate compound with a hydroxy content lid such as hydroxyalkyl acrylate or hydroxyalkyl methacrylate (the above is referred to as a urethane-based radiation-sensitive oligomer), be.

Examples of the unsaturated carboxylic acid monomers used in (1) and (2) above include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, and cinnamic acid. Acids are preferred.

In the present invention, the above flexible polymer (A) and the upper R pipe (B
) The mixing ratio of the oligomer Σ having a radiation-sensitive group is
Assuming that the total resin component is 100% by weight ((transition) is 60 to 90
% by weight, (B) is 70 to 10% by weight, especially (A
) is preferably 40 to 80% by weight and (B) is preferably 60 to 20% by weight. When (A) is 10% or less (that is, B is 90% or more by weight), the surface is smooth and has a good S/
If the N ratio is not obtained and the adhesive strength to the base material is poor, resulting in defects in durability, it is inappropriate, or if A is 90 or more (that is, B is 10 or less), It is unsuitable due to poor running durability in terms of wear resistance and friction coefficient.

The above flexible polymer (A) used in the present invention and (B)
When an oligomer having a radiation-sensitive group is irradiated with radiation such as an electron beam, only (B) reacts together, and (A) and (
B) do not react with each other, and therefore, by forming so-called mutually invaginating network connections in the form of paper chains, the effects of excellent durability and excellent S/N ratio, which are the characteristics of the present invention, can be realized. can.

In carrying out the present invention, the above (A
) The flexible copolymer (B) and the oligomer having a radiation-sensitive group (B) are mixed with the above-mentioned (A) and (B) soluble organic solvents, and in a wet state, for example, a sand mill, a ball mill, a pebble mill, etc. An organic solvent-containing paint is produced by kneading with a dispersion machine such as a roll mill and loosening the agglomeration of magnetic particles.

The ratio of the magnetic particles and the resin components (A) and (B) above is usually 10 to 50 parts by weight, particularly preferably 15 to 30 parts by weight of the total resin component per 100 parts by weight of the magnetic particles. be.

The organic solvent used may be any organic solvent as long as it dissolves (A) and (B) and easily evaporates in the subsequent drying process (e.g., toluene, xylene, methyl ethyl ketone, cyclohexanone, vinegar t' s! -c f le,
Butyl acetate, Impropatool, Butanol, Ethylene glycol monoethyl ether, Ethylene glycol monoethyl ether acetate, Dimethyl formamide,
Tetrahydrofuran, methylpyrrolidone, etc. may be used alone or in combination.

Further, a wetting agent, a surfactant, an antistatic agent, a lubricant, etc. may be appropriately used in combination to improve the dispersion of magnetic particles in the paint.

The plated solvent-containing paint produced as described above can be used as a base material for, for example, polyester films such as polyethylene terephthalate and polybutylene terephthalate, plastic films such as polyamide films and polyimide films, plastic sheets, cut sheets, etc. coated rope,
After the magnetic particles are oriented in a certain direction by passing through a magnetic field of an electromagnet or a permanent magnet, usually 6 to 20 kiloersted, they are dried in a drying oven using hot air, infrared rays, etc. in order to volatilize the organic solvent they contain. Next, in the process of smoothing with a calender roll or a press with a mirror surface at room temperature or 150°C, the oligomer having a radiation functional group (B) above hardly undergoes a crosslinking reaction, and the resin layer becomes smooth. In the oxidation process, extremely good smoothing is possible even at room temperature, which is an important factor in showing an extremely good S/N ratio.

Next, the magnetic recording material of the present invention is produced by irradiating the smoothed material with radiation such as electron beams and gamma rays to completely crosslink the oligomer (B).

As the radiation, electron beam is most suitable for handling, and the acceleration voltage is usually 100.000ev to 5.000.000.
Irradiation is carried out with an electron beam of 1.5 volts under conditions such that the total irradiation dose is 2 megarads or more, preferably 5 to 20 megarads.

The radiation irradiation is preferably carried out in an atmosphere of an inert gas such as nitrogen so that the oxygen concentration is below 1%. Excellent durability and extremely good S/N
The ratio was shown.

Hereinafter, the present invention will be specifically explained with reference to Examples. Weight average molecular weight 120.000, elongation at break 460%) 233 g of 30 modulus methyl methyl ketone solution, 30 g of trimethylolpropane triacrylate (B), 1 g of octylic acid amide as a dispersion aid, methyl ethyl ketone, toluene,
Mix 300y of a mixed solvent of ethylene glycol/monoethyl ether acetate with a mW ratio of 1:1:1, disperse it in a sand mill for 4 hours, and filter it with a cartridge type filter.
A magnetic paint (1) was obtained. It was applied to a polyester film with a thickness of 12μ using a gravure coater so that the dry coating film was about 5μ, and after being oriented in a magnetic field of 5000 oersted, it was passed through a drying oven at an ambient temperature of 120°C for 1 minute. to remove the solvent and depressurize 50 kg/c
After smoothing through a calender roll heated to 50°C, a curtain beam type electron beam irradiation machine←
The magnetic recording material (1) of the present invention was obtained by irradiation under conditions such that the exposure dose was 8 megarads at a current density of 20-7 LA and an applied voltage of 180 to 4 V).

The evaluation results are shown in Table 1.

Example 2 Urea bond-containing polyurethane resin (A) consisting of 450 g of reduced iron-based magnetic particles used in Example 1, polycaprolactone, metaphenylene diisocyanate, and inphorondiamine (weight average molecular weight 180,000, elongation at break 28096) ) of 60 dimethyl ethyl ketone solution night 20
0g, urethane oligomer (B) having an average of 2.8 double bonds per molecule consisting of trimethylolpropane, 1,4-butanediol, isophorone diisocyanate and hydroxyethyl acrylate (B) 4 of
i. 1 g of oleic acid amide as a dispersion aid, and a mixed solvent 2 of methyl ethyl ketone, toluene, and ethylene glycol monoethyl ether acetate in a weight ratio of 1=1=1.
50 g were mixed together, dispersed for 4 hours using a sand mill, and filtered through a cartridge type filter to obtain a magnetic paint (2). 1
The dry coating film is about 5μ on a 2μ thick polyester film.
After coating with a gravure coater so that Irradiation was performed using a curtain beam type electron beam irradiation machine through a 35 kg 7 cm calender roll under the same conditions as in Example 1 to obtain a magnetic recording material (2) of the present invention. The evaluation results are shown in Table 2.

Example - Reduced iron-based magnetic particles used in Example 1 450! j, copolymer (A) of ethyl acrylate and methyl methacrylate (
Weight average molecular weight 230,000, elongation at break 25%) in 30-thimethyl ethyl ketone 9250 & ) lyacrylisocyanurate (B) 25.9, 1 g of oleic acid amide as a dispersion aid, methyl ethyl ketone, toluene, ethylene glycol 600 g of a mixed solvent of ethyl ether acetate in a weight ratio of 1=1=1 was mixed, dispersed in a sand mill for 4 hours, and filtered with a cartridge type filter to obtain a magnetic paint (6). The coating was applied to a polyvarnish film having a thickness of 0.012 μm using a gravure coater so that the dry coating film had a thickness of approximately 5 μm, and subjected to magnetic field orientation, drying, and smoothing treatment using a calendar roll under the same conditions as in Example 1. Next, using the same apparatus as in Example 1, electronic irradiation was carried out under conditions such that the exposure dose was 12 megarads to obtain a magnetic recording material (3) of the present invention.

The evaluation results are shown in Table 1.

Leprosy Example 4 450 g of reduced iron-based magnetic particles used in Example 1, 3 of polycarbonate resin (A) having a bisphenol skeleton (weight average molecular weight 100.000, elongation at break 18%)
267 Il of dimethylformamide solution, 20 g of epoxy oligomer (B) which is an adduct of bisphenol A digcryl ether and acrylic ether
, 1 g of oleic acid amide as a dispersion aid and methyl ethyl ketone, toluene, N-methylpyrrolidone in a weight ratio of 1
:1: Mix 400g of mixed solvent in a sand mill.
Time dispersion was performed and the mixture was passed through a cartridge type filter once to obtain a magnetic paint (4). This magnetic paint was applied to a polyester film having a thickness of 12 μm so that the dry film thickness was about 5 μm, and the magnetic coating was oriented in a magnetic field, dried, and smoothed using a calendar roll in the same manner as in Practical Example 1.

Next, use the same equipment as in Example 1 to break the radiation. The magnetic recording material (4) of the present invention was obtained by performing electron-like irradiation under conditions such that the fM amount was 10 megarads.The evaluation results are shown in Table 1.

Comparative example 1 Reduced iron-based magnetic particles 45 (1/.

610 g of a 30% methyl ethyl ketone solution of the polyurethane resin (A) used in Example 1, 1 g of octyl amide as a dispersion aid, and 600 g of the mixed solvent used in Example 1 were mixed together and dispersed in a sand mill for 4 hours, and then mixed with trimethylolpropane. After adding and mixing 9.37 g of a common solution of isocyanate-terminated prepolymer, which is an adduct of tolylene diisocyanate,
A magnetic paint (5) used in a comparative example was obtained. This magnetic paint was applied, magnetically oriented and dried in the same manner as in Example 1, and smoothed using a 100'O calender roll with a linear pressure of 70 kg and 70 m to obtain a magnetic recording material of Comparative Example (1). Ta. The evaluation results are shown in Table 1.

Comparison chestnut 2 reduced iron-based magnetic particles 450. ! 9.1.4 Polyurethane resin with double bonds at the ends synthesized from butanediol, polyester of adipic acid, tolylene diisocyanate and hydroxyethyl methacrylate (double bond acid is 0.50 equivalent per 1000 g) 60-thimethyl ethyl ketone solution 233 p.

trimethylolpropane triacrylate) (B) 30y
, a mixed solvent of octylic acid amide 11 and methyl ethyl ketone, toluene, and ethylene glycol monoethyl ether acetate in a tt ratio of 1:1:1 as a dispersion aid 3o
oy, dispersed in a sand mill for 4 hours, passed through a cartridge type filter twice, and used as a comparative example.Magnetic paint (6)
I got it.

This magnetic paint was applied under the same conditions as in Example 1, oriented in a magnetic field, dried, smoothed with a calendar roll, and irradiated with an electron beam to obtain a hemi-lining material of Comparative Example (2).

The evaluation results are shown in Table 1.

The magnetic recording materials of Examples (1) to (4) and Comparative Examples (1) and (2) were cut into tape shapes and used in the above evaluation tests.

*1 Running test conditions 2 Each tape obtained as above was glued in a loop shape and rotated endlessly for 24 hours while contacting the head using a metal compatible deck in a 40°C 180q6 relative temperature environment. After that, the characteristics were evaluated after driving.

*2 Measured using Sokuei Kogyo VSMI (H = 10000 oe).

*3 Measured using Surfcorder 5E-8F.

(JIS BO601) *4 Measurement was performed using reference tape BASF 401R.

patent applicant Mitsui Toatsu Chemical Co., Ltd.

Claims (1)

[Scope of claims] (30 to 90% by weight of a flexible polymer having a weight average molecular weight of 20.000 or more and an elongation at tensile break of 10% or more)
and (B) an all agent-containing paint containing a resin component consisting of 70 to 10% by weight of an oligomer having two or more radiation-sensitive groups in one molecule as a binder and magnetic particles dispersed therein is applied to the base material, and a magnetic field is applied. It is manufactured by drying and removing the solvent after orientation, subjecting it to smoothing treatment by applying pressure, and crosslinking the magnetic material-containing layer by irradiating the material with radiation.
1) Magnetic recording material.