JPS62162226A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To improve the wear resistance and durability of the titled medium by coating a layer contg. an org. diamine, coating a layer contg. no org. diamine and contg. an isocyanate subsequently or simultaneously thereon to form a magnetic layer contg. polyurethane contg. a bisureylene group. CONSTITUTION:The bisureylene group is obtained by the reaction of an org. diamine with an isocyanate, and expressed as -HN.CO.NH.(R).NH.CO.NH-. The R stands for the residue of the org. diamine used. The org. diamine is incorporated into the first layer, and the second layer is formed subsequently or simultaneously without incorporating the org. diamine. The magnetic recording medium using polyurethane as the binder is thus produced. Besides, magnetic particles can be incorporated in the first layer or the second layer or in both the first layer and the second layer. To form the magnetic layer contg. polyurethane contg. a bisureylene group, the first layer is formed and dried and then the second layer is formed and dried, or the first layer and the second layer can be simultaneously coated, formed, and dried.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to magnetic recording media such as magnetic tapes and magnetic flexible disks, and particularly to magnetic recording media with excellent durability and a method for manufacturing the same.

(Prior art) Magnetic recording media are prepared using polyester, polyurethane, polyvinyl chloride, vinyl chloride:vinyl acetate copolymer, nitrocellulose, acrylic ester:styrene copolymer, etc. on a support such as a polyester film. Polyvinyl fluoride, styrene:butadiene copolymer, and various other synthetic rubber-based thermoplastic resins, as well as mixtures of these polymers and binders, along with magnetic powder, solvents, carbon black, abrasives, and polyfunctional isocyanate compounds. A magnetic layer is formed by applying a dispersion of the above-mentioned substances, drying, thermosetting, etc., and used as a magnetic recording medium. These mixed coating solutions contain water, regardless of the amount, and when an isocyanate compound is used, this water intervenes in the reaction between the isocyanate and the OH group in the binder component, and acts as a chain extender. However, not only the moisture in the coating solution fluctuates, but also the moisture in the atmosphere, so the reaction is not uniform.

Therefore, in order to eliminate these inconveniences, conventional efforts have been made to reduce moisture variations by controlling the moisture in the coating solution or the moisture in the atmosphere. However, it had disadvantages in terms of cost and equipment. Furthermore, the reaction between water and isocyanate was relatively slow, making it difficult to control the reaction. Therefore, there are also problems when used as an information storage material. For example, in the case of a flexible disk, a coating liquid is usually applied to both sides to form a magnetic layer. After coating on one side, the opposite side is coated, wound, and rolled. During this time, the reaction of isocyanate takes place. As the roll progresses, when the roll is rewound and punched into a flexible disc, it curls according to the curved surface of the roll, making it difficult to straighten the roll.

(Problems to be Solved by the Invention) An object of the present invention is to provide a magnetic recording medium with little variation as a product and excellent in durability and wear resistance. Normally, when a polymer containing an OH group at the end, such as polyester diol, polyester urethane diol, or polyether urethane diol, is used as a binder, in conventional technology, a polyfunctional isocyanate is used, and this isocyanate and These OI-
Chain extension and crosslinking reactions proceed due to the three-way reaction between the binder and water, forming a high molecular weight cross-linked V4!fi urethane, improving durability and abrasion resistance.

Needless to say, in the reaction of only the binder and the polyfunctional isocyanate without the presence of water, it is difficult to form a highly elastic polyurethane with a high molecular weight due to the small number of urea bonds.

In addition, if moisture is present, although high molecular weight polyurethane may be formed, the reaction is slow and it is difficult to control the moisture content, making it impossible to always obtain a constant product.
It has been difficult to obtain a material that can be titrated satisfactorily in terms of physical properties such as elasticity and abrasion resistance. The present invention solves the problems of magnetic recording media when using such an isocyanate crosslinked binder, has excellent abrasion resistance, can withstand repeated use over a long period of time,
It is an object of the present invention to provide a highly durable magnetic recording medium that does not reduce the recorded signal output and is error-free.

(Means for solving the problem) Magnetic recording media are rubbed at a high relative speed with the magnetic head and under a constant load during recording and reproduction, so the magnetic layer is likely to be worn out and a material with excellent wear resistance is required. Ru. Recently, polyurethane-based binders have been widely used as binders due to their excellent abrasion resistance, and it is thought that urea bonds contribute to the improvement in abrasion resistance.

Conventionally, the urea bond with was formed by the water contained in the coating solution, but as mentioned above, the reaction was slow.
In addition to drawbacks such as difficulty in controlling moisture, moisture-chain-extended polyurethanes have inferior abrasion resistance and other physical properties compared to diamine-chain-extended polyurethanes. Furthermore, in the case of chain extension using diamines, the reaction rate is too fast, making it difficult to control the reaction. In order to solve this problem and provide a durable magnetic recording medium with excellent abrasion resistance, the present inventor conducted extensive studies and arrived at the present invention.

That is, the present invention relates to a magnetic recording medium whose main components are a support and a magnetic layer, in which the magnetic layer contains a polyurethane containing a Bisraleyleff group, and the support contains an organic diamine. apply a layer,
This is a method of applying a magnetic recording medium having a polyurethane-containing magnetic layer to a Bislareyref base, which includes subsequently or simultaneously applying a layer containing no organic diamine but containing an isocyanate compound.

In the present invention, the bislareilev group is 1HN・CO・NH formed by the reaction of an organic diamine and an isocyanate.
・(R)・NH-Co・NH-, where R represents the organic residue of the organic diamine used. In the present invention, the first! ! The second r! This magnetic recording medium uses a polyurethane-based binder as a binder, and its manufacturing method is performed without blending organic diamine with J.

In the present invention, the first layer or the second A! Magnetic particles may be added to the first layer, or magnetic particles may be added to both the first and second layers.

The method for forming a magnetic layer containing polyurethane according to the Bisra Lelev Foundation of the present invention is to form and dry the first layer, then dry the second layer.
A layer may be formed and dried, or the first EJ and the second layer may be formed, formed, and dried at the same time. 1st A! The coating solution for the first layer contains an organic diamine, the coating solution for the second layer contains an isocyanate compound and does not contain diamine, and the coating solution for the first layer contains an isocyanate compound. The liquid contains an isocyanate compound and does not contain an organic diamine, and the coating liquid for mQB may be a liquid containing an organic diamine. It is carried out by containing a diamine and a small amount (or an isocyanate compound without containing an organic diamine in other agricultural coating liquids.)
Each coating solution contains one amount each of magnetic powder, abrasive, lubricant, and antistatic agent as needed! l or 2! i or more may be added to form each layer.

Examples of organic diamines used in the present invention include ethylene diamine, propylene diamine, hexamethylene diamine, diphenylmethane 4,4' diamine, and methylene bis-diamine.
4-cyclohexylamine: /, i, 4-diaminocyclohexane, diphenyldiamine, phenylenediamine,
Examples include, but are not limited to, chlorinated products of diphenylmethane 4.4 diamine. The polyfunctional isocyanate used in the present invention includes tolylene diisocyanate, trimerized tolylene diisocyanate, methylene bis-4-phenyl isocyanate, isoporone diisocyanate, adjunct of tolylene diisocyanate of trimethylolpropano, Examples include, but are not limited to, hexamethylene diisocyanate adducts of trimethylolpropane.

Examples of the lubricant used in the present invention include various fatty acids, their esters, silicon compounds, etc. Typical specific examples include n-butyl oleate, n-butyl stearate, n-octyl myristate, etc. , incetyl stearate, tridecyl steflate, oleyl oleate, butyl selotur palmitate, butyl seron rub stearate, oleic acid, lauric acid, myristic acid, valmitic acid, dimethylpolysiloxane, fatty modified silicone oil, etc. However, particularly preferred in the present invention are butyl cellosolve palmitate and butyl seron rubstearate.

The magnetic particles used in the present invention include 7-Fat O
s, Co-containing -7Fe, Os, CrO*, le
aCo-containing-FetQ, and the like.

As the binder of the present invention, a thermoplastic resin having a hydroxyl group as a terminal group is used, and polyester, polyether polyester, polyester urethane diol, and polyether urethane diol are particularly preferably used as the binder. Furthermore, polyester
Among polyether polyesters and polyester urethane diols, these polymers containing sulfonic acid metal bases are particularly preferably used. This polymer containing a sulfonic acid metal base has excellent properties in dispersing inorganic fine particles.

In the present invention, alumina, 5iC1:
z Random % a- Fine particles such as Few Os, Crt Os, etc., particularly fine particles of 1 μm or less, are used.

Furthermore, in the present invention, carbon black, graphite, or a surfactant may be added and used as an antistatic agent, if necessary.

The coating method of the present invention includes a two-stage coating method in which the first layer coating solution is coated and then the second layer coating solution is coated after drying, as well as a two-stage coating method in which the first layer and the second layer are coated simultaneously. A one-stage coating method can be used, and in this case, the extrudigon coating method can be used to simplify the manufacturing process. However, the method is not limited to the method described here.

(Example) Examples 1 to 6, Comparative Examples 1 to 2 m1Affl! was applied on a polyester film with a thickness of 75μ by a reverse kiss method. 2! A cloth liquid was applied. The first layer coating liquid was 50 g of Vylon 200 (manufactured by Toyobo Co., Ltd., copolymerized polyester resin) and 475 g of methyl ethyl ketone.
Various diamides were added to a mixture of 475 g of toluene and 475 g of toluene, and the compositions shown in the table below were prepared.

Table 1 Composition of 1st IA coating solution (representing parts by weight) Each first layer solution shown in the table above was applied, and the coating was carried out so that the dry film thickness was 0.1 to 0.4μ, and the coating was carried out at approximately 90°C. It was dried.

The coating liquid for the second layer was applied to a ball mill pot to deposit Co on the ball mill pot.
50 parts of Fct's (manufactured by Toda Kogyo Co., Ltd.) (hereinafter the same weight parts are expressed), 4 parts of α-alumina, and carbon black (
Lion Akzosha i! ! 3 parts of polyurethane resin (manufactured by Toyobo Co., Ltd.: 30% solution of 1-7 acid base-impregnated polyester polyurethane), 40 parts of methyl ethyl ketone, 40 parts of toluene.
After adding 40 parts of cyclohexano/ and kneading for 60 hours, 5 parts of Coronate E) I (manufactured by Nippon Polyurethane Co., Ltd.) and 3 parts of butylceron rubstearate were further added and mixed uniformly. The second layer coating solution prepared in this way was coated on top of each of the first layers described above using a doctor blade with a 25μ gap at a temperature of about 80°C/1if.
The film was left standing in a fl dryer to remove the solvent, and then coated on the back side in the same manner, dried, and hardened the magnetic layer in the open air at 50°C. The thickness of the second layer obtained is 2
It was ~3μ. Thereafter, it was punched out into a disk shape with a diameter of 5 inches, and its performance was evaluated.

Comparative Example-1 = A disc-shaped disk was prepared in the same manner as in the example except that the f1\1 layer was not provided.

Comparative Example-2 = Example 5 without using diamine in the first layer
A disk-shaped disk was prepared by forming the first layer and forming the second layer in the same manner, except that methyl ethyl ketone containing 50% water was used. Above, created Examples 1 to 6, Comparative Example 1
The durability of the magnetic disks No. 2 to 2 was measured.

The durability was measured by carrying out a continuous running test on track 0 with the head load of the floppy disk drive at 30g, measuring the current consumption value of the drive motor of the disk drive as a substitute value for torque, and making sure that the output voltage was the initial value. The number of baths until it became 75% or less was measured as the final bath.

The results are shown in Table-2.

Table 2 The results in Table 2 show that the one hour cure in the oven was all 5 hours, and in each example, even if the one hour cure was 2 hours, the results were not much different from the 5 hour cure. However, the durability of each of the comparative examples gradually changed to better after 48 hours of curing and 72 hours of curing, but even after 72 hours of curing, the results were inferior to the results of 5 o'clock curing of each of the examples. Indicated. From the results shown in the table above, by adding diamine to the first layer according to the method of the present invention, the curing speed of the second layer is suitably fast, and the durability is also improved due to the formation of the hisurein bond-containing polyurethane.

Further, from surface infrared spectral analysis, a Bisraleilev group was confirmed in the second layer in each of the Examples, but was not substantially observed in the Comparative Examples.

Furthermore, in the comparative example without diamine, the curing time was abnormally slow and the durability was also insufficient.

(Effects of the Invention) As an effect obtained as a result of the present invention, for example, the playback output does not decrease even when a flexible disk is used 10 million to 30 million times, and it has excellent durability with no error rate. It has become clear that it is possible to obtain a product that produces offspring. Furthermore, it has been found that by using an organic diamine in the first layer, it is possible to control the curing time of the second layer, shorten the curing time, and obtain a magnetic recording medium with excellent durability. .

Claims (1)

[Scope of Claims] (1) A magnetic recording medium whose main components are a support and a magnetic layer, characterized in that the magnetic layer contains a bisureylene group-containing polyurethane (2) The polyurethane is a sulfonic acid A magnetic recording medium according to claim 1 containing a metal base (3) A magnetic recording medium according to claim 1 which also includes a magnetic layer that does not substantially contain a bisureylene group (4) Support A layer containing an organic diamine is applied to the
A method for producing a magnetic recording medium having a magnetic layer containing a bisureylene group-containing polyurethane, which comprises subsequently or simultaneously applying a layer containing an isocyanate compound but not containing an organic diamine.