JPH0444633A - 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 a magnetic recording medium that can be used for audio tapes, video tapes, floppy disks, magnetic disks, and the like.

Conventional technology A magnetic recording medium of the fallen type is obtained by coating a non-magnetic material such as polyester with a magnetic paint made by dispersing fine ferromagnetic powder with a binder during cutting. In order to improve running properties, durability, etc., additives such as lubricants, abrasives, and hardening agents are generally added to magnetic paints.

In recent years, there has been an increasing demand for higher density magnetic recording media, and efforts are being made to increase output and reduce noise.
These are mainly achieved by atomization of ferromagnetic fine powder. In other words, the surface of the magnetic layer is made highly smooth by making the magnetic powder particles finer, resulting in higher output due to reduced spacing loss, reduction in modulation noise, and reduction in particulate noise due to uniform distribution of magnetic powder particles. be done.

Problems to be Solved by the Invention However, as magnetic powder becomes finer, it becomes extremely difficult to disperse it in a binder. In addition, even after the magnetic powder has been made into micro-particles, it tends to agglomerate and changes significantly over time.It is extremely difficult to produce a magnetic recording medium with a high C/N using such finely divided magnetic powder. Furthermore, since the surface of the produced magnetic recording medium is very smooth, the coefficient of friction is high, the running properties are unstable, and the durability is poor.

Means for Solving the Problems In order to solve the problems, the present invention provides a magnetic recording medium in which a magnetic layer is formed by spreading a paint in which fine ferromagnetic powder is dispersed in a binder onto a non-magnetic material. and the specific surface area of the ferromagnetic fine powder is 50 nf/g or more and less than Rom2/g,
and the ferromagnetic fine powder is 0.3 wt% or more and 0.8 wt%
It has an adsorbed water content of less than

By the way, the magnetic powders currently in use are roughly divided into oxide-based, metal-based, and alloy-based powders, and metal and alloy powders also have oxide films on their surfaces to improve their oxidation and corrosion resistance. It is being Therefore, the surface of any magnetic powder becomes an oxide, exhibiting strong hydrophilicity, and water is strongly adsorbed to the surface of the magnetic powder. As a result, the amount of moisture adsorbed by the magnetic powder has a large effect on the wettability of the magnetic powder to the binder, dispersant, and lubricant.

0.8 wt% on the surface of the ferromagnetic fine powder used in the present invention.
When more water is adsorbed, a monomolecular film of water is formed on almost the entire surface of the ferromagnetic fine powder, and the binder.

The number of sites where the dispersant can be adsorbed is very small, resulting in poor wettability and difficulty in dispersion. On the other hand, the amount of water adsorption is 0.
When it is less than 3 wt%, the number of sites to which the binder 9 dispersant can be adsorbed is very large on the surface of the ferromagnetic fine powder, and therefore the wettability becomes very good and dispersion becomes easy.

However, even when all the binder and the like are adsorbed and dispersion is complete, there remain a large number of active sites that can be adsorbed. For this reason, lubricants do not perform their original function if they are adsorbed to ferromagnetic fine powder.

Hardeners and other substances are also adsorbed to magnetic powder. The resulting magnetic recording medium has a high coefficient of friction, unstable running properties, and poor durability.

Furthermore, if the paint is left unattended after being made into a paint, water in the paint and in the atmosphere will be adsorbed to vacant sites, causing the paint to change over time and dispersing.

When the specific surface area of the ferromagnetic fine powder is less than 50 rrr/g, the particle size is large, resulting in poor surface smoothness of the resulting magnetic recording medium, resulting in low output and high noise.

In addition, when the specific surface area of the ferromagnetic fine powder becomes more than Sod/g, the superparamagnetic component increases and the saturation magnetization decreases.
The magnetic properties of the resulting magnetic recording medium are poor and the output is reduced.

Effect of the present invention With the above-described configuration, the amount of adsorption of the binder to the surface of the ferromagnetic fine powder is increased, and the adsorption of additives such as lubricants to the surface of the ferromagnetic fine powder is suppressed, so that electromagnetic conversion characteristics,
A magnetic recording medium with excellent running durability can be provided.

Example Examples of the present invention will be described below.

The ferromagnetic fine powder used in the present invention may be any of magnetic iron oxide, cobalt-adhered iron oxide, chromium dioxide, metal alloy magnetic powder, barium ferrite magnetic powder, and the like.

As the binder, conventionally known thermoplastic resins and thermosetting resins can be used. or reactive resins or mixtures thereof.

Examples include polyurethane resins, vinyl chloride and its copolymers, nitrocellulose, polyester resins, phenoxy resins, butyral resins, and the like.

Examples of dispersants include higher fatty acids, higher fatty acid metal salts, higher alcohols, phosphoric acid esters, and silane coupling agents, which are added as necessary.

As abrasives, α-Aρ203-, αFe203,
Cr203 etc. can be used.

As the lubricant, higher fatty acids, fatty acid esters, unsaturated aliphatic hydrocarbons, etc. can be used.

As a curing agent, polyfunctional low-molecular isocyanates, low-molecular polyamines, low-molecular polyamides, etc. can be used when heat curing is used, and polyfunctional low-molecular polyepoxy, etc. can be used when electron beam curing or radiation curing is used. Can be used.

As a solvent, MEK, MIBK, ) luene.

Cyclohexanone and the like can be used alone or in combination.

For crosstalk dispersion of magnetic paint, various crosstalk machines and dispersion machines, such as Nigoo, attritor, and sand mill, are used singly or in combination.

In addition, ferromagnetic fI-fine powder book (9.2. Warm convulsions of ferromagnetic powder powder manufacturing king culm) -yo-) makes it easy to realize 1.; = realization C.

In addition, the present invention 1::O (Iru adsorption water)・fLC;t,
Karl, No. Isher Method: Cool Moisture Measurement 11
71? X:, measured using I7, Ta-Ranowo Tsuru,).

Hereinafter, the present invention will be described as follows.

Example 1 Add the composition of A in C in the interval (1. sound 5.]・disperse 1, then °rdisba・
・The composition of C was mixed to form a magnetic paint.

Composition A Cobalt-coated magnetic iron oxide 100fi Lid salt, vinyl acetate beer copolymer S-Laric acid 11 parts by weight 1 part Kabongrak 1 City, 1 Ibe '44-IN J'll II
49 jl”, t aJ! (M) K:
I. Luko, N. Nijikuro jj Sanon: 2=1
) Composition 11 Composition A 1 Pass 162 parts by weight 1 = 1. = Tan resin 111
Heavy part (l-albeni i-p)
7 parts organic solvent
210! Sakabe (MEK: Tor) "N: CycloΔ, A linone = = 3: 2: 1 mixture a) Composition'] Composition 1 Dispersion myristic acid polyisocyanate (1゛1 polyurethane■ After preparing the magnetic paint, apply it to PET soil of 15μrrnFJ 1-
,,Drying after orientation L71. Apply force 1/under treatment. After the curing reaction is complete, turn the surface opposite to the magnetic layer) P E
A coating layer of 390 parts by weight, 3 parts by weight, and 7 parts was applied to T,...k, and the tape was slit to a width of ζ1/2 inch to produce a videotape for S-V 14 S. I5 8 Example 2 Implementation In place of the cobalt-coated iron oxide of Example 1, the alloy magnetic powder of No. 1 was used, and the other conditions were the same as in Example 1, and S-
1. Preparation of video 1 for V HS 1. 8 alloy magnetic powder example (leaved for 1 week after completion of dispersion using the composition in Example 1) Comparative Example 1 The cobalt/magnetic iron oxide of Example 1 was mixed with water 1 to 0.
15 wt%, the same rainbow search as in Example 1 was carried out to prepare a chive.

Comparative Example 2 Implementation f! AI's cobalt-coated magnetic iron oxide reduces moisture content to O
, e8wt% was used, except that a cheese was prepared in the same manner as in Example J.

Comparative Example 3 A chive was produced using the same machine as in Example 2 except that the alloy magnetic powder of Example 2 was used and the water content was 0.18 wt%.

Comparative Example 4 E L,'Ci'-pumps were prepared in the same manner as in Example 2 except that the platinum magnetic powder of Example 2 and the water content were reduced to 1.25w1%.

Ta.

Comparative Example 5 Same as Example except that using the alloy magnetic powder of Example 20, the specific surface area was set to 40 d/g. The surface area is 9h&/”g
Example 1 was prepared in the same manner as in Example 2 except for the following.

Comparative Example 7 The cobalt-magnetized iron oxide of Example 3 had a moisture content of 0.0.
A tape was produced in the same manner as in Example 3 except that the content was 8 wt%.

Each of the above samples was evaluated as follows, and the results shown in Table 1 were obtained.

■Surface roughness rank Measured with Taylor Hobson Talysurf, Ra
It was shown in Ra means the arithmetic mean of the deviations of surface roughness from the center line.

■Residual magnetic flux density Using a vibrating sample type magnetometer manufactured by Toei Kogyo, the maximum magnetic field is 5 to 6.
The residual magnetization Br was determined using e.

(2) C/N The ratio C/N between a 7 MHz signal and 5 MHz noise was measured using a 5-VH8 video deck NV-FSX manufactured by Matsushita Electric Industrial (2). The reference tape was the tape obtained in Example 1, and the values are shown in relative values.

■The surface of the magnetic layer is in contact with a 5uS303 metal bottle with a friction coefficient of 4-diameter over half the circumference, and when the WA tension is set to 20g and the tape running speed is set to 3.3■/sec. The tension Xg on the output side was measured, and the friction coefficient was determined from the following equation.

■ Using dropout NV-Psi, 100% at 23°C and 60% RH environment.
After the bus running test, the playback signal was missing (15gm, 1
6 dB) and the average value per minute of measurement was determined using a dropout counter. This is used as an index of the scratching of the magnetic layer of the magnetic recording medium, that is, the durability.

(The following is a blank space) As is clear from Table 1, according to the examples of the present invention, magnetic recording media with excellent electromagnetic conversion characteristics and excellent running durability can be obtained.

In the embodiment, only the 5-VH8 video tape has been described, but it goes without saying that the present invention can be applied to 8-video tapes, floppy disks, and the like.

Effects of the Invention As detailed above, according to the present invention, the specific surface N is 5C.
) J/ct yen 1 - QtW /σ 彀逼ME ugliness m company quantity Since the amount of adsorbed moisture on the ferromagnetic fine powder surface is specified, the binder can be firmly adsorbed on the surface of the ferromagnetic fine powder. In addition, since it is possible to suppress the adsorption of additives such as lubricants to the surface of the ferromagnetic fine powder, it is possible to provide a magnetic recording body excellent in both electromagnetic conversion characteristics and running durability.

Agent Hiroshi Mori Moto

Claims (1)

[Claims] 1. A magnetic recording medium in which a magnetic layer is formed by coating a paint in which ferromagnetic fine powder is dispersed in a binder on a non-magnetic material, and the specific surface area of the ferromagnetic fine powder is 50 m^2/g. Above 8
0 m^2/g, and the ferromagnetic fine powder has a particle diameter of 0.
A magnetic recording medium having an adsorbed moisture content of 3 wt% or more and less than 0.8 wt%.