JPS59210533A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent the shaving of a thin back layer by using carbon black of a specified average particle size in the back layer so as to reduce the coefft. of friction without deteriorating the electromagnetic transducing characteristics. CONSTITUTION:A magnetic recording layer is formed on the surface of a nonmagnetic support, and a back layer of <=2mum thickness contg. carbon block of 50-150mmu average particle size and a binder in 1:<=3.0 weight ratio is formed on the reverse side to obtain a magnetic recording medium. A thermoplastic resin, a thermosetting resin, a reactive resin or a mixture thereof is used as the binder, and it is required to have >=40 deg.C glass transition temp. Tg. The nonmagnetic support is made of acid cellulose, polyamide, an alpha-olefin polymer or copolymer, polyester or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium, and particularly to a magnetic recording medium that reduces the coefficient of friction without degrading electromagnetic characteristics, improves running durability, and provides excellent magnetic recording without scratching of the tape pack surface. Regarding the medium.

In general, there are magnetic recording tapes for audio, video, and computer use, and as the demand for high-density recording has increased recently, there are various methods such as vacuum deposition, sputtering, ion blating, etc., or electroplating. Ferromagnetic metal thin film magnetic recording media formed by plating methods such as electroless plating are attracting attention and have been put into practical use.
Alternatively, in magnetic recording tapes for computers, the surface of the magnetic recording layer is finished to be smooth in order to improve sensitivity (particularly output in a high frequency range). However, when such a smooth magnetic recording tape is wound up or rewound, it is not phased and wound easily, resulting in irregular winding. When such a magnetic tape is used, running properties deteriorate due to tension fluctuations, etc., and output fluctuates. Furthermore, the tape is easily deformed and damaged. In order to prevent this drawback, a magnetic recording tape has been proposed in which a back layer is provided on the side of the support opposite to the magnetic recording layer.

However, conventionally used back layers are prone to shearing, an increase in the coefficient of friction, and tape folding, and there is still room for further improvement.

In general, for the purpose of improving running characteristics and running durability, when a back layer is provided, when a magnetic recording medium (especially in tape form) is rolled up or stacked in sheet form, the back layer It is known that the unevenness is reflected on the surface of the magnetic layer, impairing the surface properties of the magnetic layer, thereby impairing the electromagnetic properties, particularly the S/N characteristics, of the magnetic layer medium.

The reason why the S/N characteristic deteriorates is because too much emphasis is placed on the running characteristics of the backing layer, which results in its surface becoming rough, and for this reason, when magnetic media are stored or left in a state where they are rolled up or piled up, the backing layer deteriorates. This is because the unevenness of the layer is reflected on the surface of the magnetic layer.

In addition, the major problems with metal thin film magnetic recording media, which will be described later, are (1) The frictional resistance between the magnetic head, guide poles, and other members during the process of recording, reproducing, and erasing signals is large, resulting in poor wear resistance. (2) Usually, a smooth support is used for high-density, high-S/N ratio recording, so the coefficient of friction against the traveling system members is large (which causes unstable traveling, etc.).Specifically. The reason for this is that there is a large amount of jitter when driving.

An object of the present invention is to provide a magnetic recording medium that does not increase the coefficient of friction and has good running durability.

Still another object of the present invention is to provide a magnetic recording medium having a back layer that does not impair the S/N characteristics of the magnetic medium and is compatible with both general coating type tapes and metal thin film type magnetic tapes.

The above object of the present invention is to provide a magnetic recording medium having a magnetic recording layer on the surface of a non-magnetic support and a back layer containing carbon black and a binder on the opposite side and having a thickness of 2μ or less. The average particle size of
0 mμ, and is achieved by a magnetic recording medium characterized in that the ratio of the carbon black to the binder is 1:3.0 or less by weight.

The carbon black used in the present invention has an average particle size of 50
It is preferably 150 mμ, particularly preferably 6
0-120 mμ, most preferably 80-120 mμ.

As a specific example of the above-mentioned carbon black used in the present invention, 5TERLNe (R, NS
) ko y hi' y carho y company gRAVEN 41
0, Dia Black G manufactured by Mitsubishi Chemical Industries, Ltd.; Asahi Carbon Asahi +60, etc.

As the binder for the back layer, there may be used binders conventionally known in the art, such as thermoplastic resins, thermosetting resins, reactive resins, or mixtures thereof. For example, the following binders can be selected, but one type or a mixture of two or more types has a glass transition temperature Tg of 40.
The temperature is preferably 60°C or higher, and particularly preferably 60°C or higher.

Examples of thermoplastic resins include vinyl chloride-vinylacetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, and acrylic ester-vinylidene chloride copolymer. , acrylic ester-styrene copolymer, methacrylic ester-acrylonitrile copolymer, methacrylic ester-vinylidene chloride copolymer,
Methacrylic acid ester-styrene copolymer, urethane elastomer, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose resin (cellulose acetate phthalate, (cellulose diacetate, cellulose propionate, nitrocellulose, etc.), styrene-butadiene copolymers, polyester resins, chlorovinyl ether-acrylic acid ester copolymers, amino resins, and various rubber resins.

Examples of thermosetting resins or reactive resins include phenolic resins, epoxy resins, polyurethane curable resins, urea resins,
Melamine resin, alkyd resin, acrylic reactive resin,
These include polyisocyanates and polyamines.

The ratio of carbon black to binder in the back layer used in the present invention is preferably 1:3.0 or less by weight. The thickness of the back layer of the present invention is preferably 2μ or less, particularly preferably 0.3 to 1.5μ, and most preferably 0.5 to 1.0μ.

Polymeric supports used in the present invention include acid cellulose; cellulose nitrate; ethyl cellulose; methyl cellulose; polyamide; polymethyl methacrylate; polytetrafluoroethylene; polytrifluoroethylene; polymers or copolymers of precious vinyl chloride; polyvinylidene chloride; polycarbonate; polyimide; polyesters such as polyethylene terephthalate.

In the examples for explaining the implementation of the present invention, (parts) indicate parts by weight.

Example 1 A magnetic layer containing Co-containing iron oxide was provided on the surface of a polyethylene terephthalate base having a thickness of 14 μm, and a magnetic layer was provided on the opposite side. The back layer was coated using the following composition and varying the average particle diameter of carbon black so that the thickness after drying was 1 μm.

The obtained sample is designated as sample 7g61~/166.

Nitrocellulose 25 parts (manufactured) Methyl ethyl ketone 480 parts Various tests were conducted on each sample of the above magnetic recording tape, and the results shown in the following table were obtained.

Example 2 Go-Ni (Ni 20 wt%) was deposited on the surface of a 12 μn thick polyethylene terephthalate film by oblique vapor deposition.
) A magnetic film (film thickness 0.15 μn) was provided, and a back layer was provided on the opposite side.The back layer was coated using the composition used in Example 1 so that the thickness after drying was 1 μm. The obtained samples are designated as /167 and /168.

The following tests were performed on each sample obtained in Examples 1 and 2, and the results are shown in Table 1.

Test Method 1 ■Variations in the way the tape comes out after running the virgin tape 100 passes on an S-type vTR were examined.

Test Method 2 The coefficient of dynamic friction T2/'rl of the stainless steel pole was investigated on the magnetic layer side and the back coat side using a virgin tape and a tape made by running the virgin tape 1002 times.

Test Method 3 The state of scratches on the batter coated surface was examined after 100 passes using a VH3 type VTR.

As is clear from Table 1, by using a back layer carbon black with an average particle size of 50 to 150 mμ in a magnetic tape with a thin layer, the electromagnetic conversion characteristics are not deteriorated. It is possible to obtain a magnetic tape with a low coefficient of friction and good temperature and without back coat shearing.

(3 others) Procedural amendment 1981/　Mon-7th 1984 Patent Application No. 84074 No. 2 Title of the invention magnetic recording medium 3. Person who makes corrections Relationship to the case: Patent applicant

Claims (1)

[Claims] In a magnetic recording medium having a magnetic recording layer on the surface of a non-magnetic support and a back layer containing carbon black and a binder on the opposite side and having a thickness of 2μ or less, the average particle size of carbon black is 50 to 150mμ. Also, the ratio of carbon black and binder is 1:3 by weight. A magnetic recording medium characterized in that the magnetic recording medium is 0 or less.