JPS589487B2 - Jikiki Rokubaitai - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium having excellent properties, and is particularly characterized by a binder for obtaining such a magnetic recording medium.

Conventionally, when applying a magnetic recording layer onto a polyester film, various types of undercoat layers have been provided if sufficient adhesion between the two is required.

Recently, attempts have been made to omit the undercoat layer and ensure sufficient adhesion.

For example, Japanese Patent Publication No. 44-18222 describes a method for improving the adhesion of a magnetic recording layer to a polyester film using a binder that is a combination of a polyester resin and a vinylidene chloride-acrylonitrile copolymer.

However, the combination of a polyester resin and vinylidene chloride-acrylonitrile copolymer as a binder has poor dispersibility of magnetic powder, and sufficient magnetic properties cannot be obtained, making it unsuitable for practical use.

As a result of repeated various experiments, the present inventors discovered a new combination of binders, and succeeded in obtaining a magnetic recording layer with good magnetic properties and good adhesion to polyester film. The present invention was achieved by discovering that the magnetic recording medium has good running stability.

The binder used in the present invention is composed of 30 to 70% by weight of a copolymer mainly composed of vinyl chloride and vinyl acetate, 5 to 40% by weight of a polyester resin, and 5 to 45% by weight of a vinylidene chloride-acrylonitrile copolymer. It is.

As a copolymer mainly composed of vinyl chloride and vinyl acetate,
For example, VAGH, VMC manufactured by Union Carbide Company in the United States
H, VYHH, etc. can be used.

As the polyester resin, an amorphous linear saturated polyester resin having the following physical properties is used.

Average molecular weight 10,000-30,000, solubility parameter 8.9-1
1.1, tensile breaking strength 20-1000 kg/cm2,
Those having a softening point of 100 to 200°C and a melting temperature of 120 to 250°C, for example, those made mainly of isophthalic acid, terephthalic acid, sebacic acid, and ethylene glycol, triethylene glycol, etc., can be used.

The vinylidene chloride-acrylonitrile copolymer has a softening point of 120 to 150°C and a nitrogen content of 1.0 to 6.
．． A range of 0% can be used.

In the present invention, a magnetic recording medium is obtained by kneading such a binder and magnetic powder and applying the mixture onto a nonmagnetic substrate.

Magnetic powders include γ-Fe2O3 and Co-containing γ-Fe.
2O3, Fe3O4, Co-containing Fe3O4, r-Fe
Bertolide compound of 2O3 and Fe3O4 (FeOx,
1.33<x<1.50), Co-containing γ-Fe203
and a bertolide compound of Fe304 (FeOx, 1.3
3<x<1.50), CrO2, Co-Ni-P alloy,
Co-Ni-Fe alloy, CO-Ni-Fe-B alloy, F
e-Ni-Zn alloy, Fe-Mn-Zn alloy, Fe-C
Known ferromagnetic fine powders such as o-Ni-P alloy and Ni-Co alloy can be used.
No. 45-18372, No. 47-22062, No. 47-22513, No. 46-28466, No. 46-
No. 38755, No. 47-4286, No. 47-1242
No. 2, No. 47-17284, No. 47-18509,
No. 47-18573, No. 39-10307, No. 48
-396.39, U.S. Patent No. 3026215;
No. 31341; No. 3100194: No. 3242005
No. 3389014: British Patent No. 752659; No. 782762; No. 1007323; French Patent 1
No. 107654: West German published patent OL8128133
It is stated in No. 4 etc.

It is desirable to use polyester film as the nonmagnetic substrate.

Examples 1 to 14 VAGH as vinyl chloride-vinyl acetate copolymer, Pylon 200 (Toyobo trade name) as polyester resin,
Saran F-310 (Asahi Dow product name) is used as a vinylidene chloride-acrylonitrile copolymer, and these are mixed at various mixing ratios within the range specified in the present invention to form a binder and magnetic recording by the following method. Created media.

The results are shown in Table 1.

300 parts by weight of γ-Fe203 magnetic powder 100 parts by weight of the above binder mixture Carbon black 10 Lecithin 3 Methyl ethyl ketone-methyl isobutyl ketone 900 (1:1 weight ratio mixture) These compositions were thoroughly kneaded in a ball mill, Coated on a 20 μ thick polyester film, dried, and the dry thickness was 10 μm.
It was set to μ.

Comparative Examples 1 to 4 Table 1 shows the characteristics of magnetic recording media prepared by the same operations as in Examples 1 to 14 but with different mixing ratios of binder components.

Comparative Example 5 Binder composition: VAGH 50 parts by weight, Pylon 200: 2
Magnetic recording media were prepared in the same manner as in Examples 1 to 14, except that 2.5 parts by weight of the copolymer and 27.5 parts by weight of butadiene-acrylonitrile copolymer (Nitsupol 1032, trade name) were used.

Its characteristics are shown in Table 1.

In Table 1, vinyl chloride-vinyl acetate copolymer, vinylidene chloride-acrylonitrile copolymer, and polyester resin are all expressed in parts by weight.

The squareness ratio is measured with an external magnetic field of 10000e,
Adhesive strength is determined by performing 180° peeling using 3M Scotch A41 splicing tape and expressing the force required at that time in gram weight.

Running performance was determined by running with a tape handler at 19 cm/sec.
Observations were made for abnormal noises and uneven running at each guide roll and contact area.

Examples 1 to 14 and Comparative Examples 1 to 4 are summarized in FIG. 1 and FIG. 2, and the reason for limiting the binder component ratio of the present invention is shown.

FIG. 1 shows the relationship between the component ratio and the squareness ratio, and the squareness ratio changes according to the curve shown in the figure.

FIG. 2 shows the relationship between the component ratio and the adhesive strength, and in the figure, the inside of the curve is the part with good adhesiveness.

Considering these results as a whole, the vinyl chloride-vinyl acetate copolymer does not have sufficient adhesive strength at 70% by weight or more, and does not have a sufficient squareness ratio at 30% by weight or less.

As for the polyester resin, if it is less than 5% by weight, the adhesive strength is insufficient, and if it is more than 40% by weight, the squareness ratio and adhesive strength are insufficient.

Furthermore, if the vinylidene chloride-acrylonitrile copolymer is less than 5% by weight, the adhesive strength will not be sufficient, and if it is 50% by weight, the tape runnability will be poor.

It was confirmed that these results also applied when the vinyl chloride-vinyl acetate copolymer was changed to VYHH and when the polyester resin was changed to Pylon 300.

[Brief explanation of drawings]

FIG. 1 shows the relationship between the binder composition ratio and the squareness ratio of the present invention. FIG. 2 shows the relationship between the binder composition ratio and adhesive strength of the present invention.

Claims (1)

[Claims] Copolymer mainly composed of vinyl monochloride and vinyl acetate 30-7
0% by weight, 5-40% by weight of polyester resin and 5-45% by weight of vinylidene chloride-acrylonitrile copolymer.
Create a magnetic paint using as the main binder,
A magnetic recording medium obtained by applying the magnetic paint onto a non-magnetic substrate.