JPS595421A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a video tape or the like having superior in traveling characteristics and long life, by forming a magnetic layer low in friction coefft. contg. an urethane resin having siloxane bonds in the molecule in a binder resin. CONSTITUTION:A urethane resin alone contg. 1-10% siloxane in the molecule, or a mixture of this resin and a resin conventionally used for magnetic tape or the like is incorporated as a binder of a magnetic metallic powder or the like in a magnetic layer, and this layer is formed on a support of polyester film or the like. The addition of the siloxane groups can form a tape having small friction coefft. without contg. a lubricant, superior traveling characteristics, and long life.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium such as a magnetic tape, and an object of the present invention is to provide a magnetic recording medium with a small friction coefficient on the surface of a magnetic layer and excellent running characteristics.

As video tape recorders and other devices become smaller, lighter, more efficient, and more dense, the magnetic recording media used are also required to have higher performance and reliability. . The present invention responds to the improvement of driving characteristics that are closely related to these performances.

The magnetic layer of a magnetic recording medium is usually formed by applying a magnetic paint containing magnetic powder dispersed in a binder resin onto a non-magnetic support such as a polyester film.

As the binder resin, vinyl chloride resin, urethane resin, nitrocellulose, phenoxy resin, epoxy resin, etc. are generally used alone or as a mixture thereof.

The coefficient of friction of these resins is about 0.4 to 0.6, and the coefficient of friction of a magnetic layer using these resins as a binder is also about 0.4 to 0.6, reflecting the coefficient of friction of the resin. Generally, it is about a certain degree. In magnetic tapes and the like, such a large coefficient of friction causes problems in tape running, head wear, etc. Therefore, in order to reduce the coefficient of friction, it is common to include lubricants such as fatty acids, esters, and silicone in the magnetic layer.

However, if the friction coefficient is improved by such means,
Problems arise such as head clogging due to the lubricant bulging out onto the surface, and furthermore, the coefficient of friction changes when running repeatedly, making running performance unstable.

An object of the present invention is to provide a magnetic recording medium that has a small coefficient of friction on the surface of a magnetic layer and has stable running performance. The present inventor investigated various resins that have properties as a binder for magnetic layers and have a small coefficient of friction, and as a result, found that urethane resins having siloxane bonds in the molecule produce extremely good results. That is, the magnetic recording medium of the present invention is characterized in that the binder resin forming the magnetic layer contains at least a urethane resin having a siloxane bond.

The present invention will be explained in more detail below.

The urethane resin having a siloxane bond in its molecule, which is a feature of the present invention, is obtained by reacting a polyester polyol or a polyether polyol with a hydroxyl-terminated polysiloxane, such as dimethylsiloxane, and an isocyanate. This urethane resin having siloxane bonds is characterized by a friction coefficient of % to % compared to urethane resins obtained from the reaction of incyanate with polyester polyols or polyether polyols that have been commonly used. .

In the urethane resin used in the present invention, the preferable siloxane content in the molecule is in the range of 1 to 10% by weight based on the entire resin. If the amount of siloxane is too low, the coefficient of friction will not be improved. Moreover, if it exceeds this, the adhesive strength will decrease.

Such a urethane resin containing a siloxane bond can be used alone as a binder, but if adjustment of Young's modulus is required, it can be used as a mixture with a conventionally used resin.

Further, a conventionally used lubricant may be appropriately added as necessary.

Furthermore, the present invention can be similarly applied to magnetic recording media using oxide-based magnetic powders and metal-based magnetic powders, and these magnetic recording media can be manufactured by conventional methods.

Hereinafter, the effects of the present invention will be specifically illustrated in Examples.

Each component was blended in the proportions shown below to 25 parts by weight of the binder resin having the composition shown in Tables 1 to 5 in the following table.
The mixture was mixed and dispersed for a period of time to obtain a magnetic paint.

Metallic iron magnetic powder ・・・・・・・・・・・・・・・・・・
... 100 parts methyl ethyl ketone ...
・・・・・・・・・・・・・・・ 200 parts cyclohexanone ・・・・・・・・・・・・・・・・・・
50 parts toluene ・・・・・・・・・・・・
・・・・・・・・・・・・ 150 parts oleic acid
・・・・・・・・・・・・・・・・・・ 2-part powder ・・・・・・・・・・・・・・・・・・
・・・・・・ 1 part Next, apply this paint to 1 part by the usual method.
Coated on a 5 μm thick polyester film, dried,
A magnetic recording medium was prepared by forming a magnetic layer with a thickness of 4 μm.

Tables 1 to A5 in the following table show the binder resins used in this example and the friction coefficients of the magnetic layer surfaces of magnetic recording media containing these binders.

To measure the friction coefficient, fix the measurement sample on a flat support stand with the measurement surface facing up, slide a still ball with a constant load applied over the measurement surface, and measure the frictional force acting on the still ball at that time. I asked for it. The stability was evaluated by setting the friction coefficient μ of 1 for the first slide and 100 for the friction coefficient μ of repeatedly sliding the same place 10ρ times.

These recording media were processed into video tapes, mounted on a video tape recorder, and the running characteristics were evaluated. The running characteristics are comprehensively evaluated based on tape squeal, jitter lateral fluctuation, tape winding appearance during fast forwarding and rewinding, etc.
A rating of 1 was given to those with definite problems, and a rating of 5 was given to those with excellent running characteristics without any problems in all respects, and the evaluation was made on a 6-level scale.

(Left below) ■- Comparative Example As is clear from the above table, the magnetic recording medium of the present invention using a urethane resin having a siloysan bond as a binder has the following characteristics:
The coefficient of friction is small, its change is small even after repeated friction, and it has excellent characteristics in terms of practical running.

Claims (1)

[Claims] A magnetic recording medium comprising a magnetic layer formed by dispersing magnetic powder in a binder resin on a non-magnetic support, and a urethane resin having a siloxane bond in the molecule contained in the binder resin.