JPH04206023A - 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] Industrial applications The present invention relates to audio tapes and video tapes.

The present invention relates to a magnetic recording medium that has excellent electromagnetic conversion characteristics and running durability and is used in floppy disks, magnetic disks, etc.

Conventional technology A coated magnetic recording medium is obtained by coating a magnetic paint made by dispersing magnetic powder in a binder and an organic solvent on a support such as polyester and drying it. In order to improve properties, durability, etc., additives such as lubricants, abrasives, hardeners, etc. are generally added.

In recent years, there has been an increasing demand for higher density magnetic recording media, and efforts are being made to achieve higher output and lower noise. These are mainly achieved by improving the surface properties of magnetic recording media. In other words, by improving the surface properties, it is possible to improve output by reducing spacing loss and to reduce modulation noise.

Problems to be Solved by the Invention However, with the conventional magnetic recording media, as the surface properties improve, the Wt friction coefficient on the sliding surface of the magnetic recording medium and the signal reproducing device increases, resulting in a decrease in running performance. occurs.

In order to prevent such a decrease in runnability, liquid lubricants such as higher fatty acids, fatty acid esters, and fluorine-based esters, or solid lubricants such as carbon black and molybdenum disulfide may be added to the magnetic layer alone or in combination. Common.

However, although adding a liquid lubricant improves runnability, there is a problem that the mechanical strength of the magnetic layer decreases and durability deteriorates.Additionally, adding a solid lubricant reduces the dispersibility of the magnetic powder. There is a problem in that the surface properties of the magnetic layer are deteriorated, and the filling properties of the magnetic powder are also deteriorated, resulting in deterioration of magnetic properties, that is, deterioration of electromagnetic conversion characteristics.

The present invention solves the above problems and is excellent! The object is to provide a magnetic recording medium having magnetic conversion characteristics and durability.

Means for Solving the Problems In order to achieve the above object, the present invention includes iron carbide in a magnetic layer in an amount of 1 part by weight or more and 5 parts by weight or less per 100 parts by weight of magnetic powder.

Therefore, according to the present invention, by containing iron carbide in an amount of 1 part by weight or more and 5 parts by weight or less per 100 parts by weight of magnetic powder in the magnetic layer, the solid lubricating effect on the surface of the iron carbide and the spontaneous magnetization of the iron carbide can be achieved. Therefore, the running properties of the magnetic recording medium can be improved without deteriorating the durability and magnetic properties.

Example An embodiment of the present invention will be described below.

It is common to add lubricants to magnetic recording media to improve their running properties, but adding lubricants tends to reduce durability and electromagnetic conversion characteristics, thus reducing running properties and durability. It is extremely difficult to obtain a magnetic recording medium for high-density recording that has both properties.

Iron carbide is generally a compound represented by the chemical formula FenC (n is 2 or more), but in the state of fine particles, the C atoms on the surface do not bond with Fe atoms and exist in the form of carbon black. I understand and do G.

As a result, the surface of the fine particles of iron carbide became carbon blank, and it was revealed that it had a solid lubricating effect. Moreover, the internal iron carbide itself has a spontaneous magnetization higher than that of iron oxide magnetic powder, so even if it is added to the magnetic layer, the decrease in saturation magnetization is very small compared to when a general solid lubricant is added (high electromagnetic Conversion properties can be maintained.Also, durability does not decrease like when a liquid lubricant is added.If the content of iron carbide is less than 1 part by weight per 100 parts by weight of magnetic powder, the lubricating effect is small. The running properties are poor.If the amount exceeds 5 parts by weight, the dispersibility of the magnetic paint becomes poor.

The BET specific surface area of iron carbide used in the present invention is 40nf/
If the BET specific surface area of iron carbide is less than 40 nf/g, the surface area exhibiting a solid lubricating effect is small, so the runnability is not improved, and the particle size increases, so magnetic The surface properties of the recording medium decrease,
When the BET specific surface area exceeds 80 rrf/g, the dispersibility of iron carbide decreases, resulting in a decrease in output and an increase in noise.

Furthermore, the superparamagnetic component increases and the spontaneous magnetization becomes extremely small, resulting in a decrease in magnetic properties and a decrease in electromagnetic conversion properties.

The present invention will be explained below based on specific examples.

The iron carbide used in this example is a compound represented by the chemical formula FenC, where n is a number with a minimum of 2.

The magnetic powder used in this example is magnetic iron oxide, cobalt-containing magnetic iron oxide, and cobalt-coated magnetic iron oxide.

The binder can be either chromium oxide or metal powder, and is used to bind isocyanate compounds to thermoplastic resins such as fiber resins, polyurethane resins, polyvinyl chloride resins, polyester resins, acrylic resins, and rubber resins. A wide variety of conventionally known compounds can be used, such as a combination of these and a combination of #A fats (compounds) having a radiation-functional unsaturated double bond.

As the polishing agent, alumina, red iron oxide, chromium oxide, etc. can be used alone or in combination.

As lubricants, higher fatty acids and fatty acid esters are used.

Liquid lubricants such as unsaturated aliphatic hydrocarbons and solid lubricants such as carbon black can be used alone or in combination with iron carbide.

As a solvent, MEK, MIBK, toluene.

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

To control the crosstalk fraction of magnetic paint, various crosstalk machines and dispersion machines, such as kneaders, attritors, and sand mills, are used singly or in combination.

This embodiment will be further explained in detail below.

Example 1 The following composition A was kneaded in a pressurized knead, then the composition A was diluted and mixed and dispersed with other materials in a sand mill to obtain composition B, and finally the composition C was mixed in a disper. It was made into a magnetic paint.

Composition A Co coating 7-Fe20s 100 parts by weight BET
52bo/g Saturation magnetization 766mu/g Coercive force 8000e Iron carbide 4 parts by weight BE7
55 Bo/g Saturation magnetization 95 emu/g Vinyl chloride resin 11 parts by weight! Solvent 49 parts by weight (MEK: 3:2:1 mixture of luene:cyclohexanone) Composition Composition A Kneaded product 164 parts by weight Urethane resin 11 parts by weight Solvent
210 parts by weight (Mixture of MEK: toluene: cyclohexanone - 3:2:1) Composition C Composition dispersion 385 parts by weight Myristic acid 1 part by weight Polyisocyanate 5 parts by weight (Made by B Polyurethane ■
Coronate L) 14.5μm thick PET after magnetic paint adjustment
After the curing process, a back coat layer with a thickness of 0.7 μm was formed on the PET on the opposite side from the magnetic layer, and slits were made to a width of 172 inches. A videotape for 5-VH3 was created.

Example 2 A magnetic tape was obtained in the same manner as in Example 1 except that the amount of iron carbide added was changed to 2 parts by weight.

Example 3 In Example 1, the value of BET specific surface area of iron carbide was set to 7 Or
A magnetic tape was obtained in the same manner as in Example 1 except that +f/g was used.

Comparative Example 1 A magnetic tape was obtained in the same manner as in Example 1 except that 4 parts by weight of the following carbon black was added instead of iron carbide.

Carbon black BET specific surface area 20 On'r/g Average particle size 25 nm Comparative Example 2 A magnetic tape was obtained in the same manner as in Example 1 except that 4 parts by weight of the following carbon black was added instead of iron carbide in Example 1. .

Carbon black BET specific surface area: 30 po/g Average particle diameter: 80 nm Comparative Example 3 A magnetic tape was prepared in the same manner as in Example 1 except that 2 parts by weight of stearic acid was added in composition C without adding iron carbide. Obtained.

Comparative Example 4 A magnetic tape was obtained in the same manner as in Example 1 except that the amount of iron carbide added was changed to 10 parts by weight.

Comparative Example 5 A magnetic tape was obtained in the same manner as in Example 1 except that the amount of iron carbide added was changed to 0.5 parts by weight.

Comparative Example 6 In Example 1, the value of BET specific surface area of iron carbide was changed to 90n.
A magnetic tape was obtained in the same manner as in Example 1 except that f/g was used.

Comparative Example 7 In Example 1, the value of BET specific surface area of iron carbide was changed to 201
A magnetic tape was obtained in the same manner as in Example 1 except that Tr/g was used.

Each of the above samples was evaluated as follows.

a, Ta bundle density Br (G) Samples were cut out into a 6×6 plate shape, six pieces were stacked one on top of the other, and the magnetic properties were measured using a VSM.

After once applying a maximum magnetic field of 5 kOe to the sample, the residual magnetic flux density Br was determined when the magnetic field was returned to zero.

51 Surface roughness (nm) The surface roughness of the magnetic layer was measured using a Crystep stylus type surface roughness 80 manufactured by Rank T.Hupson. The measured value was obtained by calculating the root mean square of the peak height shown on the roughness chart (Reference: National Technical Review) (National Technica
l Report) vol, 28 Ni13 Jun
e 1982 P520).

c, **Coefficient The surface of the magnetic layer is in contact with a 5US303 metal pin with a diameter of 4 cm over half the circumference of the metal pin, the input tension is 20 g, and the tape running speed is 3.3 CI.
The tension χg on the exit side when set at 1/sec was measured, and the friction coefficient was determined from the following equation.

Friction coefficient = (1/K) fn (X/20) d, electromagnetic conversion characteristic C/N (dB) The ratio of 7 MHz signal to 5 MHz noise is C/N. 5-VHS video deck N manufactured by Matsushita Electric Industrial ■ ,V-FS
It was measured using I. The reference tape was the tape obtained in Example 1, and the relative values are shown.

e, dropout D, O, (pieces/m1n) using the above video deck NV-FS I, 23°C, 60%RH
After 200 passes running test under the environment, the playback signal was missing (
15μsec.

-16 dB) was measured using a dropout counter, and the average value per minute was calculated. This was used as an index of wear of the magnetic layer of the magnetic recording medium, that is, durability.

The results of the above evaluation are shown in the table below.

As is clear from the above table, according to this example, a magnetic recording medium with excellent electromagnetic conversion characteristics, running properties, still characteristics, and durability can be obtained.

Similar effects can be obtained when applied to tapes, floppy disks, etc.

Effects of the Invention As is clear from the above examples, the present invention improves electromagnetic conversion characteristics by containing 1 part by weight or more and 5 parts by weight or less of iron carbide having spontaneous magnetization in the magnetic layer.

A magnetic recording medium with excellent durability and running properties can be provided.

Claims (2)

[Claims] (1) A magnetic recording medium in which a magnetic layer is formed by coating a paint in which magnetic powder is dispersed in a binder on a non-magnetic support, wherein the magnetic layer is made of iron carbide based on 100 parts by weight of the magnetic powder. 1
A magnetic recording medium characterized in that it contains 5 parts by weight or more and 5 parts by weight or less. (2) BET specific surface area of iron carbide is 40m^2/g or more8
Claim (1) characterized in that it is 0 m^2/g or less.
The magnetic recording medium described.