JPS6262420A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To eliminate the sticking of a material constituting a back layer to the surface of a magnetic layer and to lessen the output decrease and drop out by clogging of a head by using a material having >=50 deg.C glass transition temp. as a binder. CONSTITUTION:A thin ferromagnetic metallic film is formed on one face of a base and the back layer constituted by dispersing nonmagnetic material powder into the binder is formed on the other face. The material for the magnetic layer to be utilized is preferably Co, Fe, Co-Ni, Co-Sn, Co-Cu, etc. The nonmagnetic material powder which can be used is graphite, carbon black, SiO2, etc. The amt. of said powder to be used is adequately 20-200pts.wt. by 100pts.wt. binder. The binder is not only important in the wear of the back layer but also important in the sticking of the material constituting the back layer to the surface of the magnetic layer. The binder which can be used is a polyurethane resin, nitrocellulose, etc. having >=50 deg.C glass transition temp. These resins may be used alone or in combination of >=2 resins.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to magnetic recording media such as audio tapes, video tapes, and computer tapes.

Conventional technology Conventionally, as a magnetic recording medium, γ-F is recorded on a non-magnetic support.
e203. γ-Fe20 doped with Fe3O41Co
3. Fe5o4. Bell of γ-Fe203 and Fe3O4!
- A powder magnetic material such as a ride compound, an oxide magnetic powder such as Cr 02, or a ferromagnetic back alloy powder is dispersed in an organic binder such as a vinyl chloride-vinyl acetate copolymer, an epoxy resin, a polyester resin, or a urethane resin, Coated magnetic recording media, which are coated and dried, are widely used.

However, in recent years, with the increasing demand for high-density recording, metal thin film magnetic recording media that use ferromagnetic metal thin films formed by vacuum evaporation, sputtering, ion blating, electroplating, electroless plating, etc. have attracted attention. It has been put into practical use.

However, in the above method, when a ferromagnetic metal thin film is formed, the surface condition of the ferromagnetic metal thin film is greatly influenced by the surface condition of the support. It is desirable that the surface of the magnetic surface be as smooth as possible in order to reduce spacing loss with the magnetic head. Therefore, the support is also required to be smooth. If the support becomes smooth, when the magnetic tape is run on a deck, it will stick to posts and guide rollers, resulting in poor running.

For this purpose, it has been proposed to provide a back layer on the back side of the support.

The formation of the bank layer lowers the coefficient of friction on the bank surface and eliminates sticking to posts and guide rollers when running on a deck, greatly improving running performance.

Problems to be Solved by the Invention These techniques basically have a ferromagnetic thin film layer on one side of the support and a bank layer on the other side, and the bank layer is made of non-magnetic powder. It can be said to be dispersed in a binder. However, in a magnetic recording medium having such a back layer, a different problem was recognized compared to one without a back layer. That is, the constituent material of the back layer adheres to the surface of the magnetic layer. If the degree of adhesion of the constituent material of the back layer to the surface of the magnetic layer is large, it becomes a problem in the manufacturing process as a so-called blocking phenomenon. In addition, if the degree of damage is small, it may cause a decrease in output or dropout due to head clogging during recording and reproduction of the magnetic tape.

The present invention provides a magnetic recording medium which prevents the constituent materials of the back layer from adhering to the surface of the magnetic layer, and which reduces output drop and dropout due to head clogging.

Means for Solving the Problems In order to solve the above problems, the present invention provides a support having a thin ferromagnetic metal film on one side and a non-magnetic powder dispersed in a binder on the other side. In the magnetic recording medium having a back layer, the binder has a glass transition temperature of 50° C. or higher.

Function: By configuring the present invention as described above, there is no adhesion of the bank layer constituent material to the surface of the magnetic layer, thereby reducing output reduction and dropout due to head clogging.

Examples Examples of the present invention will be described below. In addition, in this invention, a support body is not specifically limited. As the support, a plastic film of polyethylene terephthalate, polyethylene naphthalate, polyimide or the like is used.

The material of the magnetic layer used in the present invention is not particularly limited, but includes Co, Fe, Co-Ni, Co
-Fe, Fe-8i, Co-3i, Co-Cr
, Fe-Cr, Co-Rh, Co-Mo,
Co-W, Co-T i, Co-8n
, Co-Cu, etc. are preferred.

The back layer is formed by applying a coating liquid in which non-magnetic powder is dispersed in a binder to the surface of the support opposite to the ferromagnetic thin film layer.Coating methods include gravure coating, reverse roll coating. Conventional coating methods such as coating methods can be used.

The nonmagnetic powder is selected from one or more of those commonly known as pigments or fillers. These powders are added to adjust the surface unevenness and further enhance the reinforcing effect of the back layer. The unevenness of the back layer affects the running properties of the tape and is effective in reducing the coefficient of friction. However, if the back layer is too uneven, it will cause unevenness on the surface of the magnetic layer when it is rolled up and stored.
Causes output fluctuations. For this purpose, it is necessary to form appropriate surface irregularities on the back layer. The unevenness of the back layer is determined by the particle size, content, dispersion state, etc. of the nonmagnetic powder used.

Graphite is an example of non-magnetic powder that can be used.

Car phone black, Sio2. These include TiO2, A12o3°Cr OSiC, CaCO3, ZnO, talc, kaolin, boron nitride, graphite fluoride, and molybdenum disulfide.

The appropriate amount to be used is 20 to 200 parts by weight per 100 parts by weight of the binder. If too much is used, the bank layer becomes brittle and dropouts occur more frequently. Carbon black, CaCOs, is commonly used.

The binder is important not only in wear of the band layer, but also in adhesion of the constituent materials of the back layer to the surface of the magnetic layer.

Examples of the binder that can be used in the present invention include polyurethane resins, polyester resins, vinyl-chloride-acetyl-picopolymers, and nitrocellulose having a glass transition temperature of 50° C. or higher. These resins may be used alone or in combination of two or more.

The glass transition temperature of the binder as used in the present invention is the glass transition temperature of the entire resin constituting the binder, and when a plurality of resins are used, it is the glass transition temperature of the entire mixed resin.

If the glass transition temperature of the binder is less than 50°C, part or all of the constituent materials of the back coat layer will adhere to the surface of the magnetic layer when it is wound up into a roll after coating, resulting in the formation of foreign matter on the surface of the magnetic layer. remain. In this case, when recording and playing back on tape, the head may become clogged, causing a drop in output or dropouts. Furthermore, after application,
When left in high temperature for annealing treatment, the film will be accelerated, and in severe cases, the film will adhere firmly, causing a so-called blocking phenomenon, which may cause the film to tear when it is unrolled in the next process. There is.

(Example 1) An example of a continuous vacuum oblique vapor deposition method on a polyethylene terephthalate biaxially stretched film with excellent surface smoothness.
A Ni ferromagnetic metal thin film (Nf=20 weight film thickness 1000 layers) was formed.

On the opposite side of the film on which the magnetic layer was formed, a paint prepared by thoroughly cross-dispersing the composition shown in Table 1 in a ball mill was applied by a reverse roll method, and after drying, a back coat layer was formed. The glass transition temperature of the sample A-DO binder was determined by preparing a film-like sample containing all the constituent materials of the binder and measuring the temperature change in dynamic elastic modulus using a Rheovipron manufactured by Toyo Baldwin ■. The results are shown in Table 1.

In addition, after coating, the film was wound up into a roll, and foreign matter adhering to the surface of the magnetic layer was removed using ESCA (Electron spectroscopy for chemical
Analysis) was used to measure the amount of carbon on the surface. The results are shown in Table 1.

...4) Samples A and C were slit into 8-width pieces to form magnetic tapes.

A practical test was carried out by recording and reproducing tape samples using a testing machine with the same functions as a commercially available video tape recorder. The results are shown in Table 2.

Table 2 As is clear from the results in Table 1 above, by setting the glass transition temperature of K and the binder to 50'C or higher, the adhesion of the back coat material to the surface of the magnetic layer could be reduced to a large or medium extent. Furthermore, as is clear from Table 2, it was possible to reduce the number of times of clogging and dropouts in practical tests.

Although the above example shows the case where polyurethane-nitrocellulose was used as the binder, similar effects could be obtained by setting the co-transition temperature of polyester, nitrocellulose, and vinyl chloride to vinyl acetate to 50°C or higher. .

Effects of the Invention Table 19 As is clear from Table 2, the magnetic tape of the present invention does not have the constituent materials of the back coat attached to the magnetic layer made of a ferromagnetic metal thin film layer, and thus does not suffer from decreased output or dropouts due to head clogging. There are few.

Claims (1)

[Claims] A magnetic recording medium having a ferromagnetic metal thin film layer on one side of a support and a back layer formed by dispersing non-magnetic powder in a binder on the other side, wherein the binder has a glass transition temperature of 50 A magnetic recording medium characterized by using a magnetic recording medium having a temperature of ℃ or higher.