JPS6218622A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve an electromagnetic conversion characteristic, runnability and durability by providing a magnetic layer on a non-magnetic base and forming the magnetic layer so as not to contain an org. silicone compd. therein. CONSTITUTION:The org. silicone compd. is not incorporated into the magnetic layer of a magnetic recording medium provided with the magnetic layer on the non-magnetic base. The glass part exposed to the contact surface of a magnetic head which maintains the sliding contact with the magnetic recording medium during running has always the same clean surface as in the initial period if the org. silicone compd. is removed from the magnetic layer of the magnetic recording medium. The magnetic recording medium having the excellent electromagnetic conversion characteristic and running durability is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to magnetic recording media such as magnetic tapes, magnetic sheets, and magnetic disks used in audio and video equipment, computers, and the like.

BACKGROUND OF THE INVENTION In recent years, there has been a demand for higher and higher recording densities in these various magnetic recording media. For this reason, efforts are being made to shorten the recording wavelength, narrow the track width, and reduce the thickness of the recording medium to reduce the minimum recording unit.

However, if you simply increase the recording density in this way,
Generally, S/N and output 1 frequency characteristics are disadvantageous. As a countermeasure, the saturation magnetic flux density (Br), which is a magnetic property,
Efforts have been made to improve the squareness ratio, smoothen the magnetic surface to reduce air gap loss, increase the packing density of magnetic particles, make the particles finer, etc. Among these, the most effective method is
This is a method to obtain high output by making the magnetic surface as smooth as possible, and to reduce modulation noise caused by surface roughness to a low frequency range.

However, on the other hand, the coefficient of friction of the magnetic surface increases, which is disadvantageous in terms of running durability.

Magnetic recording media, especially video tapes, have a coefficient of friction because they run stably while coming into contact with tape guides, posts, cylinders, fixed magnetic heads, etc., and because they are subjected to intense friction from the high-speed rotating video head. is low and wear resistant.

It is required to have excellent durability.

Therefore, for magnetic recording media aiming at high-density recording, high S/If, and high output, it is desirable to have a highly smooth magnetic surface and at the same time have a small coefficient of friction on both the front and back sides of the magnetic recording medium and excellent wear resistance. There is.

These prior art techniques include fatty acid esters in the magnetic layer,
Methods of incorporating lubricants such as fatty acids, silicone oils, and fluorine oils (Japanese Patent Publication No. 43-23889, Japanese Patent Publication No. 61-39081, Japanese Patent Publication No. 14249-1983) and application of a basque coat layer (Japanese Patent Publication No. 49-1989) It is known that the coefficient of friction of a magnetic recording medium can be lowered and the running performance and durability can be improved by methods such as Japanese Patent Publication No. 8321 and Japanese Patent Publication No. 51-29642.

Problems to be Solved by the Invention However, even with the above method, it has not been possible to obtain a magnetic recording medium that has sufficiently satisfactory electromagnetic conversion characteristics and durability.

As a result of intensive research into the above-mentioned problems, we found that if even a small amount of organic silicon compounds is present in the magnetic layer, the magnetic surface will be damaged by the frictional heat and contact pressure generated by the high-speed sliding contact between the magnetic surface and the magnetic head during travel. The existing organic silicon compound reacts mechanochemically with the silicon element on the glass surface that is partially exposed on the sliding surface of the magnetic head, and countless minute protrusions are generated on the glass surface, causing the surface to become I found it to be devastating.

Therefore, the above-mentioned minute protrusions grow with running time, which increases the air gap loss between the magnetic surface and the magnetic head, resulting in a decrease in output or S/N.At the same time, these minute protrusions cause scratches on the magnetic surface. It is thought that this causes an increase in powder shedding, dropouts, etc., and deteriorates durability.

In view of the above problems, the present invention provides a magnetic recording medium with excellent electromagnetic conversion characteristics, running properties, and durability.

Means for Solving the Problems In order to solve the above problems, the present invention provides a magnetic recording medium in which a magnetic layer is provided on a non-magnetic support, characterized in that the magnetic layer does not contain an organic silicon compound. This is a magnetic recording medium.

According to the above-described structure, when the organic silicon compound is removed from the magnetic layer of the magnetic recording medium, the surface of the glass portion exposed to the contact surface of the magnetic head that is in sliding contact with the magnetic recording medium is always maintained while the magnetic recording medium is running. It maintains the same clean surface as the initial one, and has the effect of preventing deterioration of electromagnetic conversion characteristics and the occurrence of head running scratches on the magnetic surface.

Example Examples of the present invention will be specifically described below.

It should be noted that all parts in the component ratios described in the examples are parts by weight.

The magnetic paint was prepared as follows.

CO-containing magnetic iron oxide powder・・・・・・・・・・・・・・・
・100 parts polyurethane resin ・・・・・・
... 10 parts vinyl chloride-vinyl acetate copolymer
... 1 part alumina oxide (α-1!zOs)
...... 2 parts average particle size = 0.2μ
m Carbon black ・・・・・・・・・・・・Yamakawa・
・・・・1 part lecithin ・・・・・・・・・
・・・・・・・・・・・・・・・・・・ 1 part myristic acid ・・・・・・・・・・・・・・・・・・・・・
・・・ 2 parts methyl ethyl ketone (MICK) ・
・・・・・・100 parts toluene ・・・・・・・・・・
・・・・・・－・・・・・・・・・・・・・・・100
Clohexanone・・・・・・・・・・・・・・・
After mixing and dispersing 60 parts of the above composition in a ball mill for 24 hours, adding 5 parts of a curing agent (Coronet L), the resulting kneaded product was filtered through a filter having an average pore size of 1 μm. A magnetic coating solution was prepared. Next, this coating solution was applied onto a 16 μm thick polyester film (PET), oriented in a magnetic field, and after drying, the surface of the magnetic layer was treated using a super calender (surface treatment machine) K, and the film was shredded into A inch width pieces. A videotape with a magnetic layer thickness of 5 μm was produced.

(Comparative Example 1) A videotape was produced in the same manner as in the example except that 0.1 part of silicone oil (Toray Silicone 5F-8427) was further added to the magnetic paint of the above example.

(Comparative Example 2) A videotape was produced in the same manner as in the example except that a polyurethane resin containing S atoms in the molecular chain was used in place of the polyurethane resin in the magnetic paint of the above example.

The characteristics of each sample above are shown in the table below. Moreover, the characteristics in the table were measured as follows.

(1) Roughness of magnetic surface Measure the surface roughness of the sample using a Talystep surface roughness meter (LPF: 25Hz) manufactured by Taylor Hobson Co., Ltd., and calculate the root mean square of the height in the obtained roughness chart. The roughness was calculated.

(2) Coefficient of friction The back side of the tape is in contact with an aluminum alloy drum with a diameter of 126 mm over half its circumference, and the output tension when the input tension on the drum is set to 35 g and the tape running speed is set to 3.20 mm. The friction coefficient was determined from the following equation.

(3) Video tape recorder with output variation VH3 system, NY-8200
(manufactured by Matsushita Electric Industrial ■) to attach aMtl to the sample tape.
A single signal of z is recorded for 3 minutes and the reproduction output of that portion is first measured. Next, the tape is allowed to play for 30 minutes and rewound, and the playback output of the first 3 minutes recorded portion is measured in the same manner, and the difference from the above playback output is defined as the output change.

(4) Variation in the number of dropouts Record a video signal on a sample tape for 10 minutes using the same video tape recorder used in (3) above, and measure the dropout (15 μsec, 16 dB instantaneous playback output) of that portion. ) is measured using a dropout counter. Next, after repeatedly running the recorded portion 100 times, the number of dropouts is similarly measured, and the difference from the above-mentioned initial value is taken as the amount of change in the number of dropouts. The dropout value is the average value per minute of the recorded portion.

(5) Rough condition of the head sliding surface glass part The sliding surface of the video head of the same video tape recorder used in (3) above was confirmed to be clean using a differential interference microscope, and then After the sample tape has been cured for 30 minutes, the roughness of the head sliding surface, especially the glass surface, is also observed using a differential interference microscope.

Effects of the Invention From the results of the Examples and Comparative Examples described above, it has been found that the magnetic recording medium according to the present invention, which does not contain an organic silicon compound in the magnetic layer, impairs the surface properties of the glass portion on the sliding surface of the magnetic head during running. However, it has excellent electromagnetic conversion characteristics and running durability, and has great practical value.

Claims (1)

[Claims] It is constructed by providing a magnetic layer on a non-magnetic support,
A magnetic recording medium characterized in that the magnetic layer does not contain an organic silicon compound.