JPS62241127A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the S/N and travelling durability of the titled medium by specifying the range of the surface roughness of a magnetic layer consisting essentially of ferromagnetic metallic powder and the fundamental wavelength component in the cross-sectional waveform on the surface. CONSTITUTION:The magnetic recording medium is formed by providing the magnetic layer consisting essentially of ferromagnetic metallic powder and a binder on a nonmagnetic carrier. The surface roughness Rrms of the magnetic layer is controlled to <=0.018mum. Besides, the fundamental wavelength component in the cross-sectional waveform on the magnetic layer surface is adjusted to 60-120mum. Consequently, the modulation noise is reduced, namely the S/N is improved, and the friction coefficient is decreased, namely the traveling durability is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to the improvement of magnetic recording media such as so-called coated magnetic tapes and magnetic disks that use ferromagnetic metal powder as a magnetic material, and particularly relates to improvements in the S/N ratio. , relates to a coated magnetic recording medium with improved running durability.

2. Description of the Related Art Generally, magnetic tapes are used in video tape recorders, audio equipment, computers, etc.

Magnetic recording media such as magnetic disks are increasingly suited for high-density recording, and for this purpose, the trend is to shorten the recording wavelength, narrow the recording track width, and reduce the thickness of the recording medium to make the minimum recording unit smaller. As a result, the S/N ratio and sensitivity 1 frequency characteristics are generally disadvantageous, but countermeasures to this problem include improving the magnetic properties such as residual magnetic flux density and coercive force, and smoothing the magnetic surface to reduce air gap loss. Alternatively, higher packing of magnetic particles, finer particles, etc. are being taken. Among these methods, the most effective method is to obtain high output by making the magnetic surface as smooth as possible, and to reduce modulation noise caused by surface roughness. However, on the other hand, the friction coefficient of the magnetic surface increases, which is disadvantageous in terms of running durability.

Magnetic recording media are generally required to have a low coefficient of friction, excellent wear resistance, and durability. Therefore, for magnetic recording media aiming at high density recording, high S/N ratio, and high output, it is desirable to have highly smooth magnetic surfaces as well as a material with a small coefficient of friction on both the front and back surfaces and excellent wear resistance. There is.

These prior art techniques include fatty acid esters and magnetic layers 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. 49-14249) and providing a back coat layer (Japanese Patent Publication No. 49-1989) It is known that the friction coefficient of a magnetic recording medium is lowered and the running durability is 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, a magnetic recording medium that satisfies both the S/N ratio and running durability has not been obtained.

As a result of intensive research on the above problems, we found that when the surface roughness Rrms of the magnetic layer becomes 0.019 μm or more, the friction coefficient decreases and the running durability improves, but the output decreases due to increased air gap loss and the surface roughness increases. On the other hand, if the surface roughness Rrms of the magnetic layer is set to 0.018 μm or less, the S/N ratio will improve, but the friction coefficient will increase. ,
It was found that this was disadvantageous in terms of running durability. Therefore,
As a result of a detailed study of the relationship between this S/N ratio and surface roughness, we found that in the future mainstream recording wavelength range of 0.6 to 1.5 μm, surface roughness wave components significantly affect modulation noise. It was found that the wavelength was in the range of 3 to 60 μm. Therefore, by setting the fundamental wavelength component in the cross-sectional waveform of the magnetic layer surface to 60 μm or more, it is possible to reduce modulation noise, that is, improve the S/N ratio, and lower the coefficient of friction, that is, improve running durability. found.

In view of the above problems, the present invention provides a magnetic recording medium with excellent S/N ratio and running durability.

Means for Solving the Problems In order to solve the above problems, the present invention provides a magnetic layer mainly composed of ferromagnetic metal powder and a binder on a non-magnetic support, and the surface roughness Rtms of the magnetic layer is 0.018μ
m or less, and the fundamental wavelength component in the cross-sectional waveform of the surface of the magnetic layer is in the range of 60 to 120 Jjm.

Effects of the present invention With the above configuration, by limiting the surface roughness of the magnetic layer of a magnetic recording medium and the fundamental wavelength component in the cross-sectional waveform of the magnetic layer surface, the air gap loss and modulation noise can be reduced, and the running of the magnetic recording medium can be reduced. The reduction in the contact area for each sliding part has the effect of lowering the coefficient of friction.

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

Note that all parts in the component ratios shown in the examples are parts by weight.

Example 1 The magnetic paint was prepared as follows.

Ferromagnetic metal iron powder 100 parts Average particle size Length 0.2 μm Acicular ratio = 8/1 Coercive force = = 16500e Polyurethane resin 10 parts Vinyl chloride, vinyl acetate copolymer resin 10 parts Aluminum oxide (α-A12o3) 6 Part average particle size = 0.2 μm Carbon black 1 part Lecithin
1 part myristic acid
1 part butyl stearate
1 part methyl ethyl ketone (MEK)
150 parts toluene
100 parts cyclohexanone 60 parts After mixing and dispersing the above composition in a ball mill for 24 hours, 6 parts of a hardening agent (Coronate L) was added and the resulting mixture was filtered through a filter with an average pore size of 1 μm to obtain a magnetic coating liquid. Got ready. Next, this coating solution was applied to a polyester film (10 μm thick, with a surface roughness Rrms of 0.012 μm).
After coating on PET, magnetic field orientation, and drying, a calendering machine (surface treatment machine) with three stages of alternating pressure elastic rolls and metal mirror-finished rolls made by placing a nonwoven fabric outer cylinder over an iron core is used to make it magnetic. The layer was subjected to surface treatment and cut into pieces with a width of 3.2 μm to produce a videotape with a magnetic layer thickness of 3.2 μm.

Example 2 The elastic press roll used in Example 1 was replaced with an elastic press roll with a polyamide resin outer cylinder covering the iron core, and the surface roughness of the 10 μm thick polyester film, Rr.
ms is 0.017 μm, and the surface cross-sectional waveform is 100
A videotape was produced in the same manner as in Example 1, except that the pitch was changed to one having a pitch of μm.

Comparative Example 1 A videotape was produced in the same manner as in Example 1, except that the surface roughness of the polyester film of Example 1 was changed from 0.012 μm to 0.020 μm.

Comparative Example 2 The elastic pressurizing roll used in Example 1 was replaced with an elastic pressurizing roll in which a polyamide resin outer cylinder was covered with an iron core, and this elastic pressurizing roll and a metal mirror roll were alternately used for 6
A videotape was produced in the same manner as in Example 1 except that the tapes were arranged in stages.

The characteristics of each sample are shown in the table below.

In addition, in the above table, the surface roughness of the magnetic layer and the wavelength.

The friction coefficient, S/N ratio, and tape damage will be explained.

(A) Surface roughness of the magnetic layer, Wavelength Using a Talistesop stylus type surface roughness meter manufactured by Teena Sunpun, the fundamental wavelength component in the cross-sectional waveform of the surface of the magnetic layer and the root mean square of the height are measured in the roughness chart. Rough Rr
ms) was calculated.

(To) Coefficient of friction: Wrap the cylinder around a stainless steel cylinder with a polished surface with a diameter of 4 cm at an angle of 180° with the magnetic layer inside, and set the entrance tension to 2.
The tension on the exit side was measured when running at 3α/sec, and the friction coefficient was determined from the following equation.

(CI S/N ratio Video S/N is determined by using a VH8 system VTR (NV-8200, manufactured by Kishita Denki Co., Ltd.) whose recording/reproducing head has been modified with a Sendust alloy, and by using a specified luminance signal (
5% white-white level device) was recorded for 3 minutes at the optimum recording current of the reference tape, and the ratio of signal to noise contained in the demodulated signal during playback was measured using a video color noise meter.

p Tape damage (Using the same VTR as used in q above, record the specified color bar signal from the TV signal generator for 120 minutes, then run 10 passes in an environment of 401:80% RH. After that , visually determine tape damage.

Effects of the Invention As described above, according to the present invention, the surface roughness Rrm of the magnetic layer
A magnetic recording medium in which s is 0.018 μm or less and the fundamental wavelength component in the cross-sectional waveform of the magnetic layer surface is in the range of 60 to 120 μm has a high S/N ratio, a low friction coefficient, and excellent running durability. It has great practical value.

Claims (1)

[Claims] A magnetic layer mainly composed of ferromagnetic metal powder and a binder is provided on a non-magnetic support, and the surface roughness of the magnetic layer is Rrms.
0.018 μm or less, and the fundamental wavelength component in the cross-sectional waveform of the surface of the magnetic layer is in the range of 60 to 120 μm.