JPH03137817A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve traveling stability by incorporating ribbon-like carbon fibers into a magnetic layer when the magnetic layer is formed by applying magnetic powder and a binder resin on a supporting body. CONSTITUTION:The ribbon-like carbon fibers to be incorporated into the magnetic layer have a specific microstructure in which carbon mesh layers are laminated substantially perpendicular to the longitudinal direction of the fiber with 3.354 - 3.380Angstrom distance between mesh planes. The fiber has substantially no hollow structure with rectangular or ellipse cross section with the aspect ratio of >3, showing ribbon-like form as a whole. The fiber has preferably several mum - several tens mum long and 0.05 - 0.7mum wide. The source material of the fiber is carbon monoxide, which is made to react with fine particles of transition metal such as iron, cobalt, nickel, etc., or compds. of these as a catalyst in the presence of hydrogen. The catalyst is, for example, an org. metal compd. such as metallocene, chloride, and carbonyl compd. By this method, the obtd. magnetic layer has good properties such as graphitization rate, electric conductivity, thermal conductivity and lubricating property.

Description

Detailed Description of the Invention [Industrial Application Field 1] The present invention relates to a magnetic recording medium, and more specifically to a magnetic recording medium that has excellent conductivity of a magnetic layer, surface smoothness, wear resistance, and durability. It is related to.

[Prior Art] Conventionally, magnetic recording media for audio, video, information recording media, etc. are made of iron tetroxide (Fe304), Y-pig iron trioxide (Y-Fe203), or chromium dioxide (Cr02).
, cobalt-containing pig iron trioxide (Co-Fe304), iron, barium ferrite, strontium ferrite, and other ferromagnetic powders are combined with a binder resin, such as an epoxy resin,
The magnetic layer is formed by diluting and mixing with an organic solvent together with a thermoplastic resin such as polyurethane resin, or a thermosetting resin such as nitrocellulose or polyvinyl compound, coating it on a support, and drying or curing it with hot air. Furthermore, carbonaceous substances such as carbon black are added to improve charging control, running stability, and wear resistance.

In recent years, along with the increasing demand for high-density recording, high reliability, wear resistance for repeated use, charging performance, durability, etc. have also been required.

For high-density recording, improvements have been made to the magnetic powder itself, and ferromagnetic powders such as the aforementioned iron, barium ferrite, and strontium ferrite have been developed. In addition, improved binder resins have been developed that are compatible with the alkali orientation of such magnetic powders. For example, carboxyl group-containing polyurethane, sulfonic acid group-containing polyurethane, carbogylic group-containing polyvinyl chloride resin, sulfonic acid group-containing polyvinyl chloride resin, phosphoric acid group-containing polyvinyl chloride resin, carboxyl group-containing polyester resin, sulfonic acid group-containing polyester Examples include resins, carboxyl group-containing nitrocellulose resins, and the like.

[Problem to be Solved by the Invention 1] However, even if the relationship between the magnetic powder and the binder resin is improved, carbonaceous materials such as carbon black must be added in order to control charging and impart wear resistance. However, there is a problem in that it is difficult to obtain a magnetic recording medium that can satisfy the stricter requirements for reliability, especially surface smoothness, abrasion resistance, and durability, by simply adding it. Ta.

[Means for Solving the Problem 1] Therefore, the inventors of the present invention have made extensive studies to solve these conventional problems, and have found that these problems can be solved by containing carbon fibers having a specific shape. We have discovered this and arrived at the present invention.

That is, the gist of the present invention is a magnetic recording medium formed by coating a magnetic powder together with a binder resin on a support to form a magnetic layer, which is characterized in that the magnetic layer contains ribbon-shaped fine carbon fibers. Exists in magnetic recording media.

The present invention will be explained in detail below.

The ribbon-like fine carbon fibers contained in the magnetic layer of the present invention are
It has a unique microstructure in which the carbon network planes are stacked substantially perpendicular to the length direction of the fiber, and the distance between the planes (d
(002)) is 3.354 to 3.380, and the cross section of the fiber is flat and rectangular or elliptical, with the ratio of the major axis to the minor axis being 3 or more. It is a fine fiber with an overall ribbon-like shape. In addition, the length of carbon fiber is several to several tens of μm.
1 width is preferably about 0.05 to 0.7 μm.

Such ribbon-shaped carbon fibers can be obtained, for example, by using carbon monoxide as a carbon raw material and reacting it in the presence of hydrogen with fine particles of a transition metal such as iron, cobalt, nickel, or a compound thereof as a catalyst. Compounds suitable as catalysts include organometallic compounds such as metallocenes, chlorides, carbonyl compounds such as (C5H5)2Fe,
Examples include FeCl3 and Fe(Co)5. The reaction temperature is 450-1000°C, preferably 550-800°C.
It is °C.

Ribbon-shaped carbon fibers obtained by such a manufacturing method have a high degree of graphitization, and have excellent electrical conductivity, thermal conductivity, and lubricity.

To obtain a magnetic recording medium that improves running stability such as smoothness, abrasion resistance, and durability while maintaining good electric signal stability by containing the ribbon-like carbon fiber of the present invention in a magnetic layer. Can be done.

The magnetic powder used in the present invention includes Fe3O4,7-F
Examples include e2O3, CrO2, Co-Fe2O3, iron, barium ferrite, and strontium ferrite.

As the binder resin, urethane resins, epoxy resins, vinyl resins, cellulose resins, etc., which are usually used in coated magnetic recording media, can be used.

In addition, as necessary, carbon black 12 dispersant, lubricant, abrasives such as aluminum oxide, chromium oxide particles, etc.
Additives such as resin curing agents such as polyisocyanate compounds can also be used.

The amount of carbonaceous material added is not particularly limited as long as it provides an antistatic effect, but it is usually in the range of 0.5 to 30 parts by weight, preferably 1 to 20 parts by weight, per 100 parts by weight of magnetic powder. Selected appropriately. As the carbonaceous material, the above-mentioned ribbon-like carbon fiber alone may be used, but a mixture of carbon black and ribbon-like carbon fiber may be used to control conductivity, and the ratio of the ribbon-like carbon fiber in the carbonaceous material is 10 to 10.
It is appropriately selected from a range of 100 parts by weight.

The above components are mixed and dispersed in a coating solvent using a dispersing machine such as a ball mill, sand mill, or three-roll mill to obtain a paint-like composition, and then the composition is coated on a support such as a polyethylene terephthalate film. A magnetic layer is formed by drying, etc., and the magnetic recording medium of the present invention can be obtained.

Examples of the coating solvent include methyl ethyl ketone, methyl isobutyl ketone, toluene, cyclohexanone, and tetrahydrofuran.

Further, the magnetic recording medium of the present invention may be provided with a back coat layer in order to further improve charging control, running stability, and abrasion resistance. The back coat layer consists of the above-mentioned binder resin, carbonaceous material, and, if necessary, a lubricant and an abrasive.

[Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to the examples unless it goes beyond the gist thereof.

Example I Iron pentacarbonyl as M medium raw material, mixed gas of -carbon oxide l hydrogen = 50150 (feed rate 60e, 7 hours)
The carbon fibers were continuously charged into a reaction tube with an inner diameter of 90 mm placed in an electric furnace set at 700° C. at a feeding rate of 4.5 g for 7 hours to perform a carbon fiber growth reaction.

As a result of electron microscopic observation, it was confirmed that the obtained carbon fibers had a rectangular or flat elliptical cross section, and were flat ribbon-like as a whole.

The width of the carbon fibers ranges from 0.05 to 0.7 μm, with 0
．． Most of them are 1 to 0.41 Jm, and 17 is 0.01 to 0.01 Jm.
The particle diameter was in the range of 0.3 μm, and most of the particles were in the range of 0.02 to 0.1 pmg. Moreover, the length was in the range of several to several tens of μm.

Furthermore, from the results of X-ray diffraction, the interplanar distance d(00
2) is 3.366 people, Mering and Maire
The degree of graphitization was calculated from the formula and was estimated to be 86%.

Also, the specific surface area calculated from the BET formula is 110cm2/
It was g.

The carbon fiber thus obtained and carbon black "#3250B" (manufactured by Mitsubishi Kasei Corporation) were mixed at a weight ratio of 2:1 and used as the carbon layer. Calculated from the BET formula of the carbon black. The specific surface area was 237m2/
It was g.

Carbonaceous powder, magnetic powder, binder resin, dispersant, curing agent, etc. are mixed in the proportions shown below, and the mixture is coated on a 75 μm thick polyethylene terephthalate film to a thickness of 1.5 μm. After drying, randomization and surface smoothing are performed. A floppy disk was obtained by punching out 3.5 inches in diameter.

a-Fe (He:14000e) 10
0 parts by weight Polyurethane resin 15 parts by weight ("N2304" manufactured by Nippon Polyurethane Co., Ltd.) Vinyl chloride-vinyl acetate resin 15 parts by weight ("VAGH" manufactured by Union Carbide Corporation) Curing agent 5 parts by weight "Coronate" manufactured by Tamoto Polyurethane Company L″) lecithin
1 part by weight alumina (average particle size: 0.5
μm) 5 parts by weight butyl stearate
5 parts by weight Carbon black 2 parts by weight (Mitsubishi Kasei ■ "13250B") Carbon fiber 4 parts by weight Methyl ethyl ketone 150 parts by weight Toluene
Table 1 shows the mixing ratio of 150 parts by weight of carbon fiber and carbon black as well as the measurement results of surface properties and abrasion characteristics as floppy disk data.

Gloss: The surface gloss after smoothing the coating surface at an incident angle of 6
The total reflectance at a reflection angle of 0° and a reflection angle of 60° was measured using a standard photometer.

Static friction: The maximum torque at the initial stage of disk rotation was measured using a torque meter attached to the disk unit.

Hardness = (Measured using a dynamic ultra-micro hardness meter DUH-50 manufactured by Shimadzu Corporation.

Example 2 The mixing ratio of carbon fiber and carbon black was 1.29:
The same procedure as in Example 1 was carried out except that the temperature was set to 4.71. The results are shown in Table 1.

Comparative Example 1 Comparative example 1 was carried out in the same manner as in Example 1 except that 6 parts by weight of carbon black 13250B alone was used without using carbon fiber. The results are shown in Table 1.

[Effects of the Invention] According to the present invention, a magnetic recording medium can be obtained which has increased conductivity by 1 and has excellent surface smoothness, rigid abrasion resistance, and durability, and is therefore industrially useful.

Claims (1)

[Claims] (1) A magnetic recording medium comprising a magnetic layer formed by applying magnetic powder together with a binder resin onto a support, the magnetic recording medium containing ribbon-shaped carbon fibers in the magnetic layer.