JPS61133016A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the adhesion between a polyester film and an under-coat layer, to improve the adhesion between a magnetic layer and the undercoat layer, and to improve the adhesion between the magnetic layer and a base body by incorporating a vinyl chloride copolymer having <=200 polymerization degree and contg. >=2wt% OH group into the undercoat layer. CONSTITUTION:A vinyl chloride-vinyl acetate-vinyl alcohol copolymer, a vinyl chloride-vinyl propionate-vinyl alcohol copolymer, a vinyl chloride-acrylic ester copolymer, and a vinyl chloride-vinylidene chloride copolymer each having <=200 polymerization degree and contg. >=2wt% OH group are examplified as the vinyl chloride copolymer having <=200 polymerization degree and contg. >=2wt% OH group. A single compd. among the compds. or a mixture of >=2 kinds of the compds. are used. The vinyl chloride copolymers can be used jointly with a curing agent such as an isocyanate compd., an epoxy compd., and an ethyleneimine compd. When the curing agent is jointly used, a tough undercoat layer is formed, and the adhesion with a magnetic layer is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic recording medium in which a magnetic layer is provided on a substrate via an undercoat layer, and more specifically, the present invention relates to a magnetic recording medium in which a magnetic layer is provided on a substrate via an undercoat layer, and more specifically, the present invention relates to a magnetic recording medium in which a magnetic layer is provided on a substrate with an undercoat layer interposed therebetween. Related to magnetic recording media.

[Conventional technology]

Magnetic recording media are usually made by applying and drying a magnetic paint consisting of magnetic powder, a binder component, an organic solvent, and other necessary components onto a substrate such as a polyester film. Since the film has high crystallinity, the adhesion of the magnetic layer to the substrate is weak, and there is a risk that the magnetic layer will peel off during use.

Therefore, in order to improve this problem, conventional methods have been used to improve the adhesion of the magnetic layer by applying an undercoat to the substrate to provide an undercoat layer between the magnetic layer and the substrate. Attempts have been made to improve the adhesion of the magnetic layer to the substrate by using polyester resin as an effective undercoat (Japanese Patent Publication No. 58-9488).

[Problem that the invention seeks to solve]

However, in those using polyester resin as an undercoat, the composition of the compound is similar to that of the polyester film, so although the adhesion of the magnetic layer to the substrate is improved, it is still not fully satisfactory.

[Means for solving problems]

This invention has been made as a result of various studies in view of the current situation, and is made by incorporating a vinyl chloride copolymer with a degree of polymerization of 200 or less and containing 2% by weight or more of OH groups into the undercoat layer. , the adhesion between the polyester film and the undercoat layer is improved, the adhesion between the magnetic layer and the undercoat layer is improved, and the adhesion of the magnetic layer to the substrate is sufficiently improved.

In this invention, the degree of polymerization used in the undercoat layer is 20.
Vinyl chloride copolymers containing 0 or less OH groups and 2% or more by weight of OH groups have a small degree of polymerization and low viscosity, so they can form a thin and uniform undercoat layer.
Because it contains more than % by weight, this large amount of OH groups strongly bonds with the remaining COOH groups on the wide surface of the polyester base fill, and also has good compatibility with the magnetic layer surface (it also adsorbs well to the magnetic layer surface. The degree of polymerization of this type is 200
When a vinyl chloride copolymer containing 2% by weight or more of OH groups is included in the undercoat layer below, the undercoat layer becomes extremely thin and uniform, exhibiting excellent adhesion to the polyester base film, and is also suitable for the magnetic layer. A well-adsorbing subbing layer is formed between the polyester base film and the magnetic layer, which subbing layer further improves the adhesion of the magnetic layer to the substrate.

Such a vinyl chloride copolymer having a degree of polymerization of 200 or less and containing 2% by weight or more of OH groups is, for example, a vinyl chloride copolymer having a degree of polymerization of 200 or less and containing 2% by weight or more of OH groups.
Vinyl acetate-vinyl alcohol copolymer, vinyl chloride-
Examples include vinyl propionate-vinyl alcohol copolymer, vinyl chloride-acrylic acid ester copolymer, and vinyl chloride-vinylidene chloride copolymer, and these may be used alone or in combination of two or more. In addition, this kind of vinyl chloride copolymer having a degree of polymerization of 200 or less and containing 2% by weight or more of OH groups can be produced according to a conventionally known method for producing the same kind of copolymer having a degree of polymerization of more than 300. .

Such a vinyl chloride copolymer having a degree of polymerization of 200 or less and containing 2% by weight or more of OH groups can be used for conventional magnetic recording, which has relatively good compatibility with this type of vinyl chloride copolymer. It may be used in combination with the binder resin used for the medium, for example, vinyl chloride resin, vinylidene chloride resin, vinyl acetal resin, cellulose resin, polyurethane resin, polyester resin, acrylonitrile-butadiene copolymer. Polyethylene resins, polyamide resins, epoxy resins, polyether resins, acrylic resins, and the like are preferably used in combination. Among these, conventionally known vinyl chloride resins are particularly preferably used in combination because they are of the same type and have extremely good compatibility. When used in combination with these conventionally known binder resins, the blending ratio should be the ratio of these conventionally known binder resins to a vinyl chloride copolymer with a degree of polymerization of 200 or less and containing 2% by weight or more of OH groups. The weight ratio of the vinyl chloride copolymer having a degree of polymerization of 200 or less and containing 2% by weight or more of OH groups is preferably in the range of 100 to 80 to 20 by weight. Adhesion to the base film cannot be sufficiently improved.

Furthermore, this type of vinyl chloride copolymer with a degree of polymerization of 200 or less and containing 2% by weight or more of OH groups may be used in combination with a curing agent such as an isocyanate compound, an epoxy compound group, or an ethyleneimine compound. When used together with a hardening agent,
Since the OH groups remaining without being adsorbed on the surface of the polyester base film in the vinyl chloride copolymer are crosslinked with the functional groups of these curing agents, a strong undercoat layer is formed and the adhesion with the magnetic layer is improved. The adhesion of the magnetic layer to the polyester base film is sufficiently improved through this undercoat layer. Specific examples of such curing agents such as isocyanate compounds, epoxy compounds, and ethyleneimine compounds include Coronate, a trifunctional low molecular weight isocyanate compound (manufactured by Nippon Polyurethane Industries, Ltd.), Epiclon 800 (manufactured by Dainippon Ink Chemical Co., Ltd.), Company-made, bifunctional bisphenol type.
epoxy resin), PAZ33 (manufactured by Nippon Shokubai Kagaku Co., Ltd., a trifunctional modified tyrene imine compound), and the like. The amount used is preferably within the range of 1 to 40% by weight based on the total amount of the undercoat resin; if it is too little, the desired effect will not be obtained, and if it is too much, the viscosity of the undercoat layer paint will increase significantly. .

In order to form an undercoat layer on a substrate in the present invention, the above-mentioned vinyl chloride copolymer having a degree of polymerization of 200 or less and containing 2% by weight or more of OH groups is used, if necessary, with other binder resins and curing agents. In addition, cyclohexanone, methyl ethyl ketone, toluene, tetrahydrofuran, or a mixed solvent thereof may be dissolved in a welding agent to prepare a solution with a desired concentration and coated on the substrate, with a dry coating thickness of 0. If the thickness is less than 0.05μ, the adhesion of the magnetic layer to the substrate will not be sufficiently improved; If it becomes thicker than θμ, the thickness unevenness of the undercoat layer will increase the thickness unevenness of the magnetic layer and have a negative effect on the magnetic recording medium, so the dry thickness should be 0.05 to 3.
．． It is preferable to apply the coating in a range of 0μ.

The magnetic layer on the undercoat layer is formed using r-Fe203 powder, Fe3O4 powder, Co-containing r-Fe203 powder, C
O-containing Fe3O4 powder, Fe powder, co powder, Fe
- A magnetic paint containing various conventionally known magnetic powders such as Ni powder and barium ferrite, a binder resin, a mechanical solvent, and other additives is formed on a substrate by any means such as spraying or roll coating. Apply on top of the undercoat layer,
It is formed by methods such as drying.

〔Example〕

Next, embodiments of the invention will be described.

Example 1 Vinyl chloride-vinyl acetate-vinyl alcohol copolymer (degree of polymerization 200, OH group content 2% by weight) Cyclohexanone 100 This composition was mixed and dispersed with a disperser for 5 hours to form an undercoat layer paint. This undercoat layer paint was applied onto a polyester base film with a thickness of 12μ and dried to form an undercoat layer with a thickness of about 0.3μ.

Next, on this undercoat layer, a magnetic paint having the following composition was applied to a dry thickness of 6 μm, and dried to form a magnetic layer.
A magnetic tape was made by cutting it to a width of 3.81 mm.

Co-containing Fe203 powder 80 parts by weight VAGH
(Manufactured by U, C, C, USA, vinyl salt 12-vinyl acetate-vinyl alcohol copolymer) Takene 1-L (manufactured by Narita Pharmaceutical Co., Ltd. 7, polyurethane prepolymer) Coronet H, (Japan Polyurethane 1) Trifunctional low molecular weight isone anate compound (manufactured by N Kogyo Co., Ltd.) Methyl isobutyl ketone 60〃Toluene
60 Example 2 In the composition of the undercoat layer paint in Example 1, instead of the vinyl chloride-vinyl acetate-vinyl alcohol copolymer with a polymerization degree of 200 and an OH group content of 2% by weight, a polymer with a polymerization degree of 200 was used.
An undercoat layer was formed in the same manner as in Example 1, except that the same amount of vinyl chloride-vinyl propionate-vinyl alcohol copolymer containing 2% by weight of OH group-containing N was used to prepare a magnetic tape.

Example 3 In the composition of the undercoat layer paint in Example 1, in place of the vinyl chloride-vinyl acetate-vinyl alcohol copolymer with a polymerization degree of 200 and an OH group content of 2% by weight, a polymer with a polymerization degree of 200 was used.
An undercoat layer was formed in the same manner as in Example 1, except that the same amount of vinyl chloride-acrylic acid ester copolymer having an OH group content of 2% by weight was used, and a magnetic tape was produced.

Example 4 In the composition of the undercoat layer paint in Example 1, instead of the vinyl chloride-vinyl acetate-vinyl alcohol copolymer with a polymerization degree of 200 and an OH group content of 2% by weight, a polymer with a polymerization degree of 200 was used.
A magnetic tape was produced by forming an undercoat layer in the same manner as in Example 1, except that the same amount of vinyl chloride-vinylidene chloride copolymer containing 2% by weight of OH groups was used.

Example 5 An undercoat layer was formed in the same manner as in Example 1, except that 0.5 parts by weight of Coronate L was further added to the composition of the undercoat layer paint in Example 1, and a magnetic tape was produced.

Example 6 In the composition of the undercoat layer paint in Example 1, the amount of vinyl chloride-vinyl acetate-vinyl alcohol copolymer with a degree of polymerization of 200 and an OH group content of 2% by weight was varied from 5 parts by weight to 2.5 parts by weight. An undercoat layer was formed in the same manner as in Example 1, except that 2.5 parts by weight of amorphous linear saturated polyester resin was added, and a magnetic tape was produced.

Comparative Example 1 In the composition of the undercoat layer paint in Example 1, VAGH (manufactured by U, C, C, USA) was used instead of the vinyl chloride-vinyl acetate-vinyl alcohol copolymer with a degree of polymerization of 200 and an OH group content of 92% by weight. Vinyl chloride-vinyl acetate-vinyl alcohol copolymer, degree of polymerization 400, OH group content 92% by weight
A magnetic tape was produced by forming an undercoat layer in the same manner as in Example 1, except that the same amount of (1) was used.

Comparative Example 2 In the composition of the undercoat layer paint in Example 1, an amorphous linear saturated polyester resin [isophthalic acid , sebacic acid, terpolymer of ethylene glycol, average molecular weight: 1700
An undercoat layer was formed in the same manner as in Example 1, except that the same amount of 0.0, intrinsic viscosity (30 ° C, 0.5% solution of phenol/tetrachloroethane-6/4: 0.54) was used,
I made magnetic tape.

The magnetic tapes obtained in each Example and each Comparative Example were tested for adhesion of the magnetic layer to the substrate. In the adhesion test, a 10 m
After pasting adhesive tape of m width and length of 10 cm, 1 m
The magnetic layer was peeled off instantly at a speed of 1/sec, and the adhesion was evaluated based on the magnitude of the load at which the magnetic layer peeled off.

The table below shows the results.

〔Effect of the invention〕

As is clear from the above table, the magnetic tapes obtained according to the present invention (Examples 1 to 6) have a lower load when the magnetic layer peels off than the conventional magnetic tapes (Comparative Examples 1 and 2). is large, which indicates that the magnetic recording medium obtained by the present invention has improved adhesion of the magnetic layer to the substrate.

Claims (1)

[Claims] 1. An undercoat layer containing a vinyl chloride copolymer having a degree of polymerization of 200 or less and containing 2% by weight or more of OH groups is formed on the substrate, and a magnetic layer is provided on this undercoat layer. magnetic recording media