JPS59227026A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To offer a magnetic recording medium whose video characteristic is excellent and whose durability and running property are good by consituting so that a specific surface area of a ferromagnetic metallic powder is large, a surface roughness of a magnetic layer is small, and also a coefficient of friction of the surface of the magnetic layer and the back layer is small. CONSTITUTION:The surface of a magnetic layer is smoothed and a noise is lowered by constituting so that a specific surface area of a ferromagnetic metallic powder measured by an N2 gas adsorbing method by a BET system becomes >=35m<2>/gr. Also, in order to minimize a spacing loss, and in order to lower a noise, a surface roughness of the magnetic layer is set to <=0.04mu. In this regard, its surface roughness is a surface roughness measured by an average roughness of a center line of 0.25mm. cut-off value defined in the clause 5 of JIS-B0601. Also, durability in case the magnetic layer has been smoothed has a correlation to a coefficient of friction of a medium, and the durability and the running property are raised by setting the coefficients of friction of the surface of the magnetic layer and the back layer to <=0.25 and <=0.20, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium, and particularly to a 1ζ magnetic recording medium using ferromagnetic gold)FAa powder, which is useful for high recording densities.

As ferromagnetic powder, iron oxide-based fine powder, which has been used conventionally, and in recent years, because of its high saturation magnetization and coercive force (Jθ magnetic powder, which is used to improve recording density and reproduction output) Examples include magnetic metal powder.

Magnetic recording tapes using ferromagnetic metal powder (so-called metal tapes) can have higher recording densities than conventional iron oxide tapes.In recent years, Toyu et al. have been seriously considering commercialization for patented video applications. . VT using all metal tape
I('lr) A prototype device has been proposed that is ultra-compact and integrated with a camera.In the Katana/Karu system, the recording density is assumed to be more than twice that of the current VTII and β methods. ) diameter is the current approximately 1/2, and the head/tape relative speed is approximately 1/2. Along with this, the recording wavelength is also halved and is estimated to be less than lμ, about 0.1μ.

Even when recording and playing back under such conditions, the image G is still the same as that of a current VTR/β.
It is required to be as good as the system.

Therefore, when evaluated under the same conditions, CN ratio (ratio of street signal output and modulation noise when recording on FM carrier wave)
Therefore, a tape for VTR/β+AdB or more is required.

In order to meet this requirement, the wave body requires a unique adjustment,
Problems arise with this.

In other words, as the wavelength of recording wave technology becomes shorter, the coercive force of the tape (
) It is necessary to raise lcl to some extent.

Furthermore, the surface of the magnetic layer should be as smooth as possible in order to minimize the gap loss between the head and the magnetic layer.

In order to make the surface of the magnetic layer flat and blue, it is necessary to increase the dispersion rate of the magnetic particles and to carry out sufficient surface shaping. This is also effective in reducing noise. Furthermore, reducing the particle size of the magnetic particles is even more effective and important.

If the size is made smaller by % child size, the following drawback will occur.

That is, the running performance deteriorates and stick-slip '5r
-Prolongation of magnetic layer durability, VTI
(In the still mode, the head bulges out, the output decreases at peak times, and the surface of the foundation layer is scraped by the head.)

The object of the present invention is, firstly, to provide an image with excellent video characteristics.
Signal relationship 0! The second object is to provide a good magnetic recording medium for long-lasting songs, and the third object is to provide a magnetic recording medium with good running properties.

The present inventors measured the specific surface of powder on ferromagnetic gold using the BET method using the N2 gas adsorption method. We have found that i is an important index for improving the properties targeted by the present invention. In order to achieve all the objectives of the present invention, 31 m2/gr or more,
It is essential that the desired QμOm, 2/gr or more is required. That is, by using magnetic powder with a large specific surface area and a small particle size, the surface of the magnetic layer can be flattened, noise can be reduced, and the CN ratio can be increased.

In addition, in order to minimize the spacing loss by reducing the gap with the head, and to reduce noise and increase the CN ratio, the surface roughness (Ra) of the magnetic layer is set to θ, 01
It needs to be 1 μ or less, preferably 0.03 lt or less. Incidentally, the surface roughness (Ra) is the surface roughness measured using a central gland average roughness with a cut-off value of 0.23 mm defined in Section 5 of JIS-BO O/.

As described above, if the particle size is made smaller and the surface of the magnetic layer becomes smoother, the durability will be reduced, and the amount of deposits on the head surface will increase, making the head more likely to become clogged. As a result of detailed studies, the inventors found that the durability when the particle size becomes smaller and the magnetic layer becomes smoother is correlated with the friction coefficient of the medium. Specifically, 4i)i The coefficient of friction on the surface of the other layer is O9λj1, and the coefficient of friction on the surface of the back layer is 0. ．． I found out that J'L should be 20 or less.

1:l''+'Measure the above friction coefficient with the loading shown in the figure.In the figure, l is connected to the motor and is made of 1ζ stainless steel.
(1G diameter 23 mm), 2 is a magnetic recording tape piece fixed with Uniroll/KO so that the same magnetic j~ as the sample to be subjected to a+++ W is on the surface, 3 is a magnetic recording tape piece where the magnetic layer surface of the tape piece λ and the pack surface are in contact A sample (magnetic recording tape) is suspended on a roll l as shown, l is attached to one end of the sample i''
Lf-4 load M! Ogr, J' is U whose base is fixed
Gauge, t depends on U gauge? This is a routine, automatic recording diagnosis. Under such arrangement if, roll /f
Rotate in the direction shown by the arrow, and measure the tension T1 between the roll l and the load and the roll / and U gauge! The friction coefficient μ of the back layer surface was determined by measuring the tension T2 between the two.

Although the method for producing the ferromagnetic metal powder used in the present invention is not particularly limited, it can be produced, for example, by the following method.

(11 A method of thermally decomposing an organic salt of a ferromagnetic metal and reducing it with a reducing gas.

(2) Acicular oxyhydroxide or Shinkin PA
A method of reducing acicular iron oxide obtained from all iron oxides or these oxyhydroxides (iron oxide reduction method).

(3) A method in which a ferromagnetic gold coating is evaporated in a low-pressure inert gas (low-vacuum evaporation method).

(4) A method of thermally decomposing metal carbonyl compounds.

(5) A method of electrodepositing ferromagnetic metal powder using a mercury shadow and then separating it from mercury.

(6) Reducing substances in aqueous solutions of metal salts that form ferromagnets! A method of obtaining ferromagnetic powder by reduction using a borohydride compound, hypophosphite, hydrazine, etc.

In the present invention, ferromagnetic metal powder produced by the above methods (21, (31, Furthermore, when producing the ferromagnetic gold 11 powder of the present invention by JAi, it is desirable to provide an oxide film on the particle surface in order to improve the chemical stability of the fine metal powder.

The composition of the magnetic powder is Fe, Fe-Ni, ]';
Pure iron and alloys such as e-Ni-Co, and B, C, N, Al, Si, P, S-Ti for the 7ζ stage to further improve properties.
It is also possible to contain a small amount of non-magnetic or non-metallic elements such as -Cr, Mn, Cu, and Znd. The shape of the particles is generally difficult to determine, as they may be the remains of needle-like particles, consisting of a necklace of n100 angstrom spherical particles. That's why! The magnetic size can also be generally defined as 71 I/1°, and the neutralized magnetization of the magnetic material is /, 20 emu/gr.
The above is preferably /-2Je+nu/gr or more. By using a magnetic material with high saturation magnetization, the residual magnetization (Br) of the magnetic layer can be increased and a magnetic recording medium with high video electric shock can be obtained.

1, the coercive force ()1 c ) of the magnetic recording medium is 100o
o! That's all, preferably / / 00 Q! Above, it is particularly desirable that 1xooα or more is required. By increasing the coercive force to a certain degree or more, it is possible to completely reduce each bolt μ loss (self-demagnetization, recording demagnetization) that accompanies the shortening of the recording wavelength, and to achieve high output recording.

In order to smooth the surface of the magnetic layer and reduce the surface roughness, it is necessary to reduce the particle size of the ferromagnetic metal powder, or to perform sufficient cross-dispersion treatment between the ferromagnetic metal powder and the binder. Alternatively, a molding treatment using a super calender or the like after forming the magnetic layer is effective.

Aritsuki lysed pancreas and 17 used for application include ketones such as acetone, methyl ethyl ketone-methyl isodutyl ketone, and cyclohexanone; alcohols such as methanol, ethanol, propatool, and butanol; methyl acetate,
Ester systems such as ethyl acetate, butyl acetate, ethyl lactate, glycol acetate, and monoethyl ether; 1) Col ether systems such as ether, glycol dimethyl ether, glycol monoethyl ether, and thiophylsan; tars such as benzene, toluene, and xylene; System (aromatic hydrocarbons); methylene chloride, ethylene chloride, 4jh
If chlorinated hydrocarbons such as chlorinated carbon, chloroform, ethylene chlorohydrin, and dichlorobenzene are used alone,
Can be mixed and used. Of these, methyl ethyl ketone, methyl ibutyl ketone, cyclohexanone, butyl acetate, toluene, xylene, etc. are preferred because they are easy to use.

As the particle size of the ferromagnetic metal powder is reduced or the surface of the magnetic layer is made smoother, the durability of the magnetic layer decreases, and VT
The output may drop during recording and playback in R, or the head
The output may not be output due to failure. In addition, the parts inside the RAD cylinder, guide pole, and cassette will be contaminated (and smeared).This problem is unavoidable in order to obtain sufficient characteristics of the metal tape using ferromagnetic metal powder. One effective way to solve 'i''L is to lower the friction coefficient of the tape, and as a result of detailed study, it was found that the friction coefficient of the magnetic layer surface is 0.2jt or less, and the friction coefficient of the back layer surface is 0.20. It was found that the following.

To reduce the coefficient of friction, for the magnetic layer side,
It is effective to modify the type of lubricant, select the amount, overcoat, and apply a back layer to the pack surface to adjust the surface roughness of the base surface.

The above ferromagnetic powder is kneaded with a binder to form a magnetic coating liquid. The binder used in the present invention is not particularly limited; conventionally used thermosetting resins, thermoplastic resins, reactive resins, and mixtures thereof can be used. For example, vinyl chloride copolymer, various cellulose resins, acrylic +,) 1 resin, poly-11 amide resin, butadiene (
There are hardening resins, urethane elastomers, and hardening resins.

Mixing ratio d of ferromagnetic metal powder and binder, binder g ~, 2. It is t.

Various fatty acids and fatty acid esters are added to completely reduce the coefficient of friction between the magnetic layer and VTR guide parts, head cylinder, and cassette mechanism parts, and to ensure running performance. Silicone oil (e.g. polysiloxane) if necessary
, inorganic powders such as graphite, binary molybdenum, and molybdenum disulfide, fine plastic powders such as polyethylene, polytetrafluoroethylene, lubricants such as fluorocarbon materials, molten alumina, silicon carbide, and chromium oxide (Cr203). ), corundum, abrasives such as diamond, and mixtures thereof, as well as various surfactants, plasticizers, rust preventives, and mixtures thereof, as required.

Examples of the non-magnetic support include synthetic resins (for example, Fol ester, hinyl-based F177-, cellulose derivatives),
Non-magnetic metal, paper, etc. can be used, and the form is a film, tape, sheet, etc.

The magnetic layer coated on the support is subjected to smoothing treatment (for example, smoothing treatment before drying or calendering treatment after drying) in order to improve magnetic properties such as S/N.

The additives, supports and manufacturing methods exemplified above are described in Japanese Patent Publication No. 56-26-20.

In the case of high recording density where the recording wavelength is 1μ or less, the thickness of the magnetic layer is preferably ≠μ or less, preferably 3μ or less.

Hereinafter, the present invention will be specifically explained with reference to Examples. In addition, "part" indicates "1 part by weight" and "cold" indicates "weight part".

Examples and comparative examples! A black ferromagnetic metal powder was obtained by hydrogen reduction of α-F6203 obtained by thermal decomposition of cobalt-containing acicular α-F e OO). A gradual oxidation treatment was performed by gradually raising the oxygen partial pressure of the powder.Table 1 shows the magnetic properties and specific surface area of the powder thus obtained.

300 parts of the above ferromagnetic metal powder and the following composition were cross-dispersed using a ball mill. The processing time for crosstalk distribution is shown in Table 2.

1] Ester polyurethane (reaction product of ethylene adipate and 2)-tolylene diincyanate, styrene equivalent average molecular weight approx./30,000) 3 parts vinyl chloride-vinyl acetate-maleic anhydride copolymer (maleic acid content 3) .0 ratio, degree of polymerization approximately≠θ 0) 30 parts α-alumina
lj part carbon black
Tripartite butyl acetate
300 parts methyl isobutyl ketone
E o o part: 3 parts of oleic acid, 3 parts of palmitic acid
part and amyl stearate << part (sample /, //)
-Ovitic acid/, part, palmitin (qV/,
! Part & 3 parts of Guamyl Stearate (Sample/2)
The mixture was kneaded for about 30 minutes.

Furthermore, 5.2.2 parts of a triisocyanate compound [an adduct of 3 mol of tolylene diinocyanate and 1 mol of trimethylolpropane (molecule tJr7i,o, NCO Mui-I 13.3 part, trade name: A 7J ethyl thiolate solution (Desmodule, L, -7JJ) manufactured by Bayer A, G, Co., Ltd. was added and dispersed under high speed shearing for 1 hour to prepare magnetic (s% blood). It was coated on a polyethylene terephthalate film of 3.0 μm to a dry thickness of 3.0 μm.

Next, the film was oriented in an IF magnetic field and then dried.

After drying, apply calendaring treatment! 72 inch I
1 km of magnetic tape for video with a J slit. The final coating layer is 3. It was lt.

In addition, in Sample 13, instead of applying force to the lubricant, a magnetic tape was obtained, and then palmitic acid was applied to the surface of the magnetic layer. 7/m”
(This is an overcoat.

The magnetic properties were measured using a vibrating sample magnetometer (trade name manufactured by Toei Kogyo I).
These are the measured values using the "VSM-1n type").

The video characteristics are VH8 type VTR (Matsushita Electric Manufacturing Co., Ltd., product name rNV-
This is the value obtained by measuring the playback output of ≠MH7 using ``gzaOO''). Standard tape is V) 18 tape 'l'/JOE
(Fuji Photo Film (TJ9 Flu).

The CN ratio is the CN ratio when a 41 MHz carrier signal is recorded and the level at 3.0MT4z of the reproduced oscillation 11]i tone signal is taken as the noise level.

Surface roughness: J I 5-Bo 1. This is the measured value at the center line roughness of the cutoff value o, 2sH, which is determined and scaled by the term O1tns.

In addition, the above v'f is used for fζ to evaluate the durability of the magnetic layer.
Run the tape under the high humidity of Rf30'C-If ORI-14, and measure the time for the output to drop to /dB (1 time, with a limit of 10 minutes).

[Brief explanation of the drawing]

FIG. 1 shows an apparatus for measuring the coefficient of friction. In the figure, / indicates a stainless steel rod, 2 indicates the surface of the magnetic layer, 3 indicates the pack layer of the measurement sample, and l indicates the load. Patent 14J (4 people Fuji Photo Film Co., Ltd.
1 Figure 142

Claims (1)

[Claims] In a magnetic recording medium having a magnetic layer containing ferromagnetic metal powder and a binder on one surface of a nonmagnetic support and a back layer on the other surface, the specific surface area of the ferromagnetic metal powder is 3 j ?
712/gr or more, and the surface roughness of the magnetic layer is
0.04 tBm or less, and the friction coefficient of the magnetic layer surface is 0.04 tBm or less. λj or less, friction coefficient force on the surface of the pack layer 50.2θ
A magnetic recording medium characterized by the following: