JPS6049972B2 - magnetic recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium, and an object thereof is to provide a magnetic recording medium with excellent durability by improving the wear resistance of a magnetic layer.

The wear resistance of a magnetic layer formed by applying a magnetic paint consisting of magnetic powder, a binder, an organic solvent, and other necessary components onto a substrate such as a polyester film is determined by
It is well known that improvements can be made by including a lubricant in the magnetic layer, depending on the type of resin used as a binder.

Among these types of lubricants, liquid paraffin is one of the lubricants that has a relatively good effect on improving wear resistance. (more than 3% by weight)
need to be used.

However, when such a large amount of lubricant is contained in the magnetic layer, a larger amount than necessary tends to seep out onto the surface of the magnetic layer due to sliding contact with the magnetic head during recording and reproduction. Therefore, the lubricant disappears quickly, which not only makes it impossible to maintain stable durability over a long period of time, but also has the drawback that it stains the magnetic head etc. and tends to cause adhesion to objects in contact with it. I understood. As a result of intensive research in light of the above circumstances, the inventor attempted to improve the wear resistance of the magnetic layer by using a specific resin as a binder.
In addition, when phthalate ester is contained in the magnetic layer along with liquid paraffin, even if the amount of liquid paraffin added is increased, no excessive seepage into the magnetic layer surface occurs, and an excellent lubricating effect can be obtained stably over a long period of time. They discovered that the abrasion resistance was further improved, and came up with the present invention. That is, the present invention relates to a magnetic recording medium in which a magnetic layer containing a mixture of a vinyl chloride-vinyl acetate copolymer and a urethane prepolymer as a binder for magnetic powder contains liquid paraffin and a phthalate ester. It is something.

Examples of the vinyl chloride-vinyl acetate copolymer used in this invention include vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-fluor vinyl alcohol copolymer, and vinyl chloride-vinyl acetate-maleic acid copolymer. Examples of commercially available products include polymers, etc., and examples of these commercially available products include
, C, C, VYHHNVAGH, and VMCH manufactured by the company.

The urethane prepolymer 5- used in this invention is
It is a urethane resin having free isocyanate groups, preferably at both straight chain ends, and usually has a molecular weight of about 1,000 to 10,000, and is usually in a liquid state. This urethane prepolymer has good compatibility with the above-mentioned vinyl chloride-vinyl acetate copolymer, and plays a role as a plasticizer for the copolymer, giving the magnetic layer appropriate flexibility. Therefore, it has the function of increasing the strength of the magnetic layer by crosslinking with the copolymer, and both effects improve the wear resistance of the magnetic layer. Specific examples of such urethane prepolymers include Takenate L-1007 manufactured by Takeda Pharmaceutical Company Limited;
Takenate L-1006sCoronate #408 Hecoronate #4090, Coronate #4095 manufactured by Nippon Polyurethane Industries. Examples include Hypren #10 and Hypren #167 manufactured by Mitsui Toatsu Chemical Co., Ltd.

The binder used in this invention is a mixture of a vinyl chloride-vinyl acetate copolymer and a urethane prepolymer, and both are mixed in an appropriate ratio, for example, vinyl chloride-vinyl acetate copolymer to 40 to 9 parts by weight. A urethane prepolymer is used in combination at a ratio of 10 to 6 parts by weight to provide a binder suitable for improving wear resistance.

The liquid paraffin used in this invention refers to a hydrocarbon oil obtained by refining a relatively light lubricating oil fraction, such as a spindle oil fraction, and is mainly composed of alkylnaphthenes.

Its usage ratio is usually 0.5 parts per 10 parts of magnetic powder.
~1 weighing part is sufficient. Examples of phthalate esters to be contained in the magnetic layer together with the liquid paraffin include dibutyl phthalate, dioctyl phthalate, dihebutyl phthalate, and butyl lauryl phthalate. The ratio is preferably 111 to 1110.

When liquid paraffin and phthalate ester are contained in the magnetic layer in the above ratio, even if the amount of liquid paraffin is increased, an excessive amount of liquid paraffin will not seep out to the surface of the three magnetic layers, resulting in long-term stability. This provides an excellent lubrication effect and further improves the wear resistance of the magnetic layer.

In order to incorporate this liquid paraffin and phthalate ester into a magnetic layer using a mixture of a vinyl chloride-vinyl acetate copolymer and a urethane pre-polymer as a binder of magnetic powder, a conventional method may be used. A method in which liquid paraffin and phthalate ester are added to a magnetic paint containing the above mixture as a binder and kneaded to form a magnetic layer, or a magnetic paint containing the above mixture as a binder is applied onto a substrate and dried. A method in which a pre-formed magnetic layer is impregnated with liquid paraffin and a phthalate ester in the presence or absence of a suitable solvent, or either liquid paraffin or a phthalate ester is added to the paint when preparing the magnetic paint. However, after forming the magnetic layer, a method may be adopted in which the other layer is impregnated into the magnetic layer.

Next, this invention will be explained in more detail by giving examples of the invention.

In addition, in the following, parts mean parts by weight. Example 1 75 parts of r-Fe2O3 powder, 15 parts of VAGH (vinyl chloride-vinyl acetate-vinyl alcohol copolymer, mentioned above), 1 part of Takenate L-1007 (urethane prepolymer, mentioned above), 1.4 parts of carbon black A magnetic coating material was prepared by thoroughly mixing 1 part, 3 parts of dioctyl phthalate, 3 parts of liquid paraffin, 65 parts of toluene, and 65 parts of methyl isobutyl ketone in a ball mill.

This magnetic paint is applied onto a 21μ thick polyester film to a dry thickness of 10μ and dried to form a magnetic layer.The surface of this magnetic layer is calendered to give it a mirror finish, and then shaped into a tape. I cut it down and obtained magnetic tape.

Example 2 A magnetic tape was obtained in the same manner as in Example 1 except that butyl phthalate was used instead of dioctyl phthalate.

Comparative Example Only VAGH was used as the binder component in Example 1.
A magnetic tape was obtained in the same manner as in Example 1, except that the addition of dioctyl phthalate was omitted.

For each magnetic tape obtained in the above Examples and Comparative Examples, we evaluated the wear resistance by measuring the abrasion loss, and also observed the surface condition of the magnetic layer at the time of measurement to determine whether liquid paraffin had soaked into the surface. The results of examining the presence or absence of release were as shown in the table below.

In addition, the wear loss is the wear loss after connecting a fixed length of magnetic tape in a loop shape and running it for 1 hour while slidingly contacting the magnetic head at a running speed of 3807 TL/sec, with the comparison example being 100. As is clear from the table above, the magnetic saturation tape according to the present invention does not seep out of the lubricant onto the surface, and the loss of wear due to abrasion is smaller than that of the magnetic tape of the comparative example. It can be seen that the wear resistance has been greatly improved.

Claims (1)

[Claims] 1. A magnetic recording medium comprising a magnetic layer containing a mixture of vinyl chloride-vinyl acetate copolymer and urethane prepolymer as a binder for magnetic powder and liquid paraffin and phthalate ester.