JPS6222233A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To enhance wear resistance, durability and non-electrostatic chargeability and to improve running stability and electromagnetic conversion characteristic by incorporating nonmagnetic material adsorbed with a specific carbon black into a backcoat (BC) layer. CONSTITUTION:The BC layer into which the nonmagnetic material adsorbed with the carbon black of <=100mum average particle size and about >=30m<2>/g specific surface area and having >=6 Mohs' hardness is incorporated is provided on the rear surface of a base on which a magnetic layer is provided. The electromagnetic conversion characteristic of Y-S/N, C-S/N, etc. is improved and the surface electric resistivity is improved by disposing such BC layer, by which the good antistatic characteristic, small coefft. of dynamic friction after repeated running and good runnability are obtd. Since the material having >=6 Mohs' hardness is used, the magnetic recording medium is highly resistant to flawing and is improved in the durability; in addition, the drop-out is decreased. Since the nonmagnetic material adsorbed with the carbon black has good dispersibility in the coating compd., the BC layer has high light shieldability. The magnetic powder packing density of the magnetic layer is thereby increased and the good electromagnetic conversion characteristic is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to magnetic recording media such as magnetic tapes and magnetic disks for use in video, audio, computers, etc., for example.

[Prior art and its problems]

In recent years, much research and development has been carried out on magnetic recording media such as video magnetic tapes, and as a result of this research, the electromagnetic conversion characteristics have been dramatically improved.

Generally, there is a close relationship between the electromagnetic conversion characteristics and the smoothness of the base film that is the support of the magnetic recording medium, and as the electromagnetic conversion characteristics improve, base films are becoming smoother.

However, magnetic recording media in which a magnetic layer is formed on a smooth base film have drawbacks such as poor wear resistance and poor running stability.

Therefore, in order to solve these problems, it has been proposed to provide a so-called back coat layer on the side of the base film opposite to the magnetic layer, and to mix carbon black or a non-magnetic substance into this back coat layer. has been done.

In other words, by mixing carbon black, it is possible to prevent static electricity charging, prevent the adhesion of dirt and dust, and prevent winding disorder, and by mixing non-magnetic substances, it is possible to prevent It is said that it is possible to improve abrasion resistance and durability.

However, it has been found that simply providing a back coat layer containing carbon black and a non-magnetic substance is insufficient.

For example, since carbon black has poor dispersibility, if the carbon black is not sufficiently dispersed in the paint for the back coat layer, carbon black agglomerates will form, and the paint with these agglomerates will be coated. If the back coat layer is made up of 30% carbon, the surface properties of the back coat layer will be significantly reduced, and a magnetic tape with such a back coat layer with poor surface properties will have a back coat on the surface of the magnetic layer in the wound state. The surface of the coating layer is transferred, resulting in a decrease in electromagnetic conversion characteristics.

[Disclosure of the invention]

While conducting research on the above-mentioned problems, the inventor of the present invention found that instead of incorporating carbon black and a non-magnetic substance independently as substances to be contained in the so-called back coat layer, carbon black was incorporated into a non-magnetic substance The carbon black to be contained and adsorbed in the back coat layer has an average particle size of about 10% by weight or more and a specific surface area of about 3 Or, t7 g or more, and By using a powder with a Mohs hardness larger than 6 as a non-magnetic substance, it is possible to provide a magnetic recording medium that has excellent wear resistance, durability, antistatic properties, and running stability, and has good electromagnetic conversion characteristics.

I found it.

That is, a magnetic layer is provided on one side of the support, and a resin layer containing a non-magnetic material with a Mohs hardness of more than 6, which adsorbs carbon black with an average particle size of 100 mμ or less and a specific surface area of about 30 m7 g or more, is provided on the other side. This magnetic recording medium has solved the above problems.

The amount of carbon black adsorbed to the non-magnetic material is
It is desirable that the ratio of the carbon black adsorbed nonmagnetic material to the nonmagnetic material is approximately 10% by weight or more, and the ratio of the carbon black adsorbed nonmagnetic material contained in the resin layer is approximately 1/1/2. It is desirable that the weight ratio be within the range of 10 to 10/1 (weight ratio).

The non-magnetic material to which carbon black is adsorbed preferably has an average particle size of about 0.01 to 2 μm, and the thickness of Barafco-14a, which is a resin layer containing a non-magnetic material to which carbon black is adsorbed, is is about 0.3~
It is desirable that the thickness is 4 μm.

[Example 1] 100 parts by weight of Co-containing r-Fetus, 1 part by weight of lecithin, 15 parts by weight of vinyl chloride-vinyl acetate-vinyl alcohol copolymer, 5 ita parts of polyurethane elastomer, and 320 parts by weight of a mixed solvent of methyl ethyl ketone and toluene. Thoroughly mix and disperse with a sand mill, add 5 parts by weight of a polyisocyanate curing agent to make a magnetic paint,
This magnetic paint is coated on one side of a 14.5 μm thick polyester film support and calendered to form a magnetic coating layer about 5 μm thick on one side of the polyester film support.

In addition, carbon black with an average particle size of 15 mμ and a specific surface area of 3 oom"7 g was mixed with α-ALzO3 with an average particle size of 0.3 μm.
(Mohs hardness 9) Carbon black adsorption α-A t20 s (carbon black adsorption amount 30
% by weight), 5 parts by weight of nitrified cotton, 10 parts by weight of polyurethane elastomer, 70 parts by weight of methyl ethyl ketone, and 30 parts by weight of cyclohexanone were thoroughly mixed and dispersed in a sand mill, and this paint was applied to the other side of the polyester film support. The coating is dried to form a resin layer containing carbon black adsorbed α-A Lx Os with a thickness of about 1 μm.

Thereafter, the material is allowed to stand for 48 hours at 40.degree. C. for a curing reaction, and then slit to obtain a magnetic recording medium such as a magnetic tape for video.

[Example 2] In Example 1, carbon black adsorption α-A At
Instead of Os, carbon black adsorption Tio2 (Ti
Average particle size of ES: 0.25 ttm, Mohs hardness: 6
A magnetic recording medium is obtained by carrying out the same procedure using 30% by weight of adsorbed carbon black.

[Example 3] In Example 1, carbon black adsorption α-A t2
νζ instead of 0 s, carbon black adsorbed CrtOx (
A magnetic recording medium is obtained in the same manner using Cr2's (average particle size 0.4 Am1, Mohs hardness 9, carbon black adsorption amount 30% by weight).

[Comparative Example 1] In Example 1, carbon black adsorption α-A L
A magnetic recording medium is obtained by carrying out the same procedure without providing the tOs-containing resin layer.

[Comparative Example 2] In Example 1, carbon black adsorbed α-At20
A magnetic recording medium is obtained by carrying out the same procedure using 5 parts by weight of carbon black and 35 parts by weight of α-Azt0 in place of 10 parts by weight of s.

[Comparative Example 3] Same as Example 1, male-bon black adsorption α-A A
A magnetic recording medium is obtained by carrying out the same procedure using α-A At Os instead of t 03 .

〔Characteristic〕

Regarding the magnetic recording media on each side above, Y-5/N, C-5
/N, surface electrical resistance of the surface opposite to the magnetic layer, initial and 5
The coefficient of dynamic friction after repeated running 00 times, the degree of damage on the surface opposite to the magnetic layer after repeated running 500 times, and the dropout were examined as shown in the table below.

Table I (Measured using a noise meter when recorded and reproduced using an R-2200 VTR.

・The coefficient of dynamic friction indicates the coefficient of friction between the base film surface and the chrome-plated surface of the bottle on the travel path.

・The degree of damage is BR-6400 type V manufactured by Victor Japan.
The judgment was made by repeatedly running using a TR and observing the degree of scratches on the surface opposite to the magnetic layer, where O marks indicate no scratches and X marks indicate scratches.

- Dropout is a count of the number of times the reproduced output signal drops by 20 dB or more for 15 μsec or more.

According to this, for example, in Comparative Example 1 without a back coat layer, although Y-3/N and C-5/N are comparable to those of this example, the surface electrical resistance is large;
It is easy to be charged with static electricity, and repeated running tests have shown that the coefficient of dynamic friction increases, resulting in poor running performance, and there are also many dropouts.
Carbon black and α-A Ax with a Mohs hardness of approximately 9
Even if a resin layer containing Os is provided, Comparative Example 2, which is not of the type in which carbon black is adsorbed to α-A Ax Os, has Y-5/N, C-S/N, etc. The magnetic properties of Comparative Example 1 without such a resin layer
In addition, as shown by the coefficient of dynamic friction in the repeated running test, the running performance is poor, and there are also many dropouts, and there is no carbon black included. Comparative Example 3, which only contained Y-5/N and C-5/N, had good magnetic properties such as Y-5/N and C-5/N, but had a large surface electrical resistance.
There are drawbacks such as easy static electricity build-up and frequent dropouts.

On the other hand, the magnetic recording medium of this example has Y-5/N
, C-5/N, surface electrical resistance, runnability, degree of scratching, and dropout.

〔effect〕

In the present invention, on the side opposite to the magnetic layer, an average grain size of approximately Loom is formed.
Since we provided a resin layer containing a non-magnetic substance with a Mohs hardness of more than 6 and adsorbing carbon black with a specific surface area of about 3077 L'/g or more, Y-3/N and C-5/
It has good electromagnetic conversion characteristics such as N, has a low surface electrical resistance and is difficult to be charged with static electricity, has a small dynamic friction coefficient after repeated running and has good running properties, and has a Mohs hardness of more than 6. is used, making the magnetic recording medium scratch-resistant and highly durable.
In addition, there is little dropout, so regeneration is good, and since the carbon black adsorbed non-magnetic material has good dispersibility in the paint, the carbon black adsorbed non-magnetic material-containing layer has high light-shielding properties, and carbon black is contained in the magnetic layer. Even if it is included, the amount thereof can be reduced, and therefore the packing density of the magnetic powder can be improved, so that the electromagnetic conversion characteristics can be improved accordingly.

Procedural amendment August 2'6, 1985

Claims (1)

[Claims] A magnetic layer is provided on one side of the support, and an average particle size of approximately 100 is provided on the other side.
1. A magnetic recording medium comprising a resin layer containing a non-magnetic material having a Mohs hardness of more than 6 and adsorbing carbon black having a specific surface area of about 30 m^2/g or more and a specific surface area of about 30 m^2/g or less.