JPH01102730A - Magnetic recording medium - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to magnetic recording media such as audio tapes, video tapes, and magnetic disks.

2. Description of the Related Art Generally, magnetic recording media for audio, video, or computers are manufactured by applying a magnetic paint containing magnetic powder and binder resin as main components onto a non-magnetic support such as polyethylene terephthalate and drying it. Ru. Recently, the demand for high-density recording has increased, and retention power (H
a) Magnetic recording media using ferromagnetic metal magnetic powder with high residual magnetic flux density (Br) have come into use.

It is thought that by making the ferromagnetic metal magnetic powder into finer particles and increasing its filling, even higher density recording becomes possible.

However, since the hardness of ferromagnetic metal magnetic powder is low, the running durability of the magnetic layer of a magnetic recording medium using it is not sufficient, and scratches may occur on the surface of the magnetic layer or the ferromagnetic metal magnetic powder may fall off from the magnetic layer. dropouts, clogging of the magnetic head due to magnetic powder falling off from the magnetic layer, and spacing loss due to abrasion particles adhering to the surface of the magnetic layer, resulting in recording and reproducing characteristics. The problem of a drop in energy levels quickly became a problem.

Therefore, conventionally, α-mu 120 is added to the magnetic layer of a magnetic recording medium.
3,0r205. TiO□fz has a large hardness
Contains an abrasive made of grains of rice grains, and this abrasive improves the wear resistance of the magnetic layer itself, and also appropriately polishes the surface of the magnetic head that makes sliding contact with the magnetic layer to prevent the adhesion of the above-mentioned abrasion particles. A method has been adopted to do so. However, when such abrasives are added, the amount and particle size of the abrasives to be added are difficult to select; for example, adding too much abrasives can cause significant wear on the magnetic head, and may also be unfavorable in terms of electromagnetic characteristics. I can't say that. On the other hand, if the amount added is small, the desired durability cannot be obtained. Regarding the particle size of the abrasive, if the particle size is small, the amount of wear on the head will be small, but the durability (still characteristics) will be poor. On the other hand, when the particle size is large, durability (still characteristics) is improved, but the amount of head wear increases. Therefore, when adding such an abrasive, for example,
It is proposed to use two types of abrasives as described in Japanese Patent Publication No. 162129, and to use one type of abrasives with different particle sizes as described in JP-A-62-16235. has been done.

Problems to be Solved by the Invention However, with the method described above, the variation in particle size of the abrasive is too large, making it impossible to fully satisfy both the amount of wear and the still characteristics. had. Furthermore, because the specific surface area of the abrasive is too small or the amount of water adsorbed to the abrasive particles is large, the dispersibility of the abrasive in the magnetic paint becomes poor, and the smoothness of the surface of the magnetic layer deteriorates. The problem was that the output decreased.

In view of the above-mentioned problems, the present invention has excellent durability (still characteristics) and suitable head polishing properties, and at the same time, high output and
The present invention provides a magnetic recording medium with a high C/N.

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 containing ferromagnetic metal magnetic powder and a binder resin is formed on a support. , specific surface area9. or/f/ or more, and the cumulative distribution of particles with an average particle size of 0.2 μm or less and 0.3 μm or less is 80% or more,
It is characterized in that an abrasive having an adsorbed moisture content of 0.1 wt % or less is added to the magnetic powder in an amount of 5 to 1 wt %.

Effect The inventor of the present invention conducted intensive studies on the specific surface area of the abrasive, the adsorbed moisture content, and the amount added, and found that the average particle size was 0-2μ.
5 to 10% of the abrasive particles with a particle cumulative distribution of 80% or less of 0.3 μm or less to the above ferromagnetic metal magnetic powder.
It has been found that by adding wt%, a magnetic recording medium with excellent durability (still characteristics) and appropriate head polishing properties can be obtained. Anything outside the above range cannot satisfy both characteristics at the same time.

Furthermore, the specific surface area of the abrasive is 9. ord／'! that's all,
By controlling the amount of adsorbed water to 0.1 wt% or less, agglomeration between abrasive particles is prevented, the dispersibility of the abrasive in the magnetic paint is improved, and an extremely smooth magnetic layer surface is obtained, which improves spacing. A magnetic recording medium with low loss, high output, and high C/H can be obtained. If the content is outside the above range, the dispersibility will deteriorate and this is not preferred.

EXAMPLES The following examples will be described in detail. In the examples and comparative examples, each part of the material is ferromagnetic metal magnetic powder'1
The number of parts by weight is shown based on i100.

Further, the amount of adsorbed moisture in the present invention refers to the amount measured using the principle of moisture measurement by the Karl Fischer method.

Example 1 Ferromagnetic metal magnetic powder 100 parts [average major axis diameter 0.20 μm, average axial ratio 1:10] Polyurethane resin 8 parts (trade name TS-53, manufactured by Dainippon Ink Co., Ltd.) Vinyl chloride-vinyl acetate type co-polymer Polymer 12
Part (Product Master Craftsman Slekman manufactured by Block Chemical Co., Ltd.) Abrasive
Part 6 carbon black
2 parts [average particle size 25 μm] Lubricant 3 parts (n-butyl stearate) Solvent MEK 130 parts Toluene 130 parts Cyclohexanone 60 parts The above composition was cross-dispersed in a ball mill for 24 hours to obtain a magnetic paint. Next, 5 parts by weight of a curing agent (Coronate L manufactured by Nippon Polyurethane Co., Ltd.) is added and stirred with a disper.

After filtering the paint through a filter with an average pore size of 1 μm,
Coated on 10 μm thick polyethylene terephthalate,
Orientation, drying.

Performed calendar processing. After the curing reaction was completed, a back coat layer was provided on the polyethylene terephthalate on the opposite side from the magnetic layer, and the tape was slit into 8 mm width to produce an 8 mm videotape.

Example 2 An 8H videotape was produced in the same manner as in Example 1 except that the amount of abrasive was changed to 7 parts by weight.

Example 3 An 8-game videotape was prepared in the same manner as in Example 1 except that the amount of abrasive was changed to 1 part by weight.

Comparative Example 1 A videotape for 8 friends was produced in the same manner as in Example 1 except that 7 parts of the abrasive was used instead of the abrasive.

Comparative Example 2 An 8H videotape was produced in the same manner as in Example 1 except that 7 parts of the abrasive was used instead of the abrasive.

Comparative Example 3 An 8H videotape was produced in the same manner as in Example 1 except that 15 parts of the abrasive was used.

The following measurements were performed on each of the BMM video tapes obtained in the above Examples and Comparative Examples.

Magnetic layer surface roughness: The centerline surface roughness (Ra value) of the magnetic layer surface of each 8-game videotape was measured using a stylus type surface roughness meter.

C/'H (5MH2/4.5MHz); 5MHz
The ratio of the signal at 4.5 MHz to the noise at 4.5 MHz was measured. The 9MN tape recorder for C/N measurement is MVS-
5000 (KOI) manufactured by AK Company) was used. An amorphous alloy was used for the recording/reproducing head, and the C/N of the 8-home video tape of Comparative Example 3 was used as a reference (odB), and relative values are shown.

Reproduction output: The output during reproduction of a signal recorded at 5 MHz with an 8-way video tape recorder is shown as a relative value with the output of the 8-way video tape of Comparative Example 3 as a reference (odB).

Still Life: Using a videotape recorder modified for still measurement, play back still images that have been recorded in advance at -10°C and 30 copies and 7 loads.The time required for the image signal to drop by 6 dB is Indicated.

Scratch test; We used our prototype steel ball sofranch tester.

(&t25±1℃) The results are shown below.

In the above examples, the abrasives used were α-A1203 and IJ SiC, 0r20. , TiO
The same applies to other commonly used abrasives such as No. 2.

Effects of the Invention As described above, the present invention has a specific surface area of 9.0 d/9 or more, an average particle diameter of 0.211 m or less, a particle cumulative distribution of 0.3 μm or less of 80% or more, and an adsorbed water content of 0.
5 to 10 ft% of abrasive, which is 1 wt% or less, is added to the magnetic layer.
By including it, it has excellent durability (still characteristics) and appropriate head polishing properties, and at the same time, it provides a magnetic recording medium with high output and high C/H due to improved dispersibility and smoothness of the magnetic layer surface. can do.

Claims (1)

[Claims] A magnetic recording medium in which a magnetic layer containing ferromagnetic metal magnetic powder and a binder resin is formed on a support, and the magnetic layer has a specific surface area of 9.0 m^2/g or more and an average particle size of 0. Particle cumulative distribution of 2 μm or less and 0.3 μm or less is 8
A magnetic recording medium characterized in that an abrasive having an adsorbed moisture content of 0% or more and 0.1wt% or less is added to the magnetic powder in an amount of 5 to 10wt%.