JPS63306523A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve a traveling property and durability by allowing a carbon having specific particle sizes to exist at a specific area ratio in the surface of a magnetic layer contg. magnetic powder, binder and carbon on a nonmagnetic base. CONSTITUTION:This magnetic recording medium is constituted by forming the magnetic layer contg. the magnetic powder, the binder and the carbon on the nonmagnetic base. The carbon having 100-400nm particle size is made to exist at 0.006-0.04(mum)<2> total area at each 1(mum)<2> of the magnetic layer in the surface of the magnetic layer of said medium. As to the size and area of the carbon existing in the surface of the magnetic layer, the spacing of a head and the magnetic recording medium increases as the size of the exposed particles is large and a decrease in the output is resulted if the size of the carbon exceeds 400nm. The good S/N is not obtainable if the exposing area exceeds 0.04(mum)<2>. The magnetic recording medium having the excellent traveling property and durability is thereby obtd.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Application Field) The present invention relates to a magnetic recording medium in which a magnetic layer is formed on a non-magnetic support, and in particular a magnetic recording medium with excellent running properties and durability. Regarding recording media.

(Prior Art) Magnetic recording media have recently come to be used as recording media for recording large amounts of information in a wide range of fields such as audio, video, and computers. Progress is being made in developing magnetic recording media that have excellent running properties against heads and magnetic pads, and are resistant to abrasion caused by these and have excellent durability.

In order to improve durability, improve surface smoothness, and improve electromagnetic conversion characteristics, methods of incorporating carbon, graphite, etc. into the magnetic layer are also being considered.

However, the carbon used in the past was mainly used to impart conductivity, and its particle size was small, making it unable to sufficiently improve runnability. It is inappropriate because it causes

(Problems to be Solved by the Invention) As described above, conventional magnetic recording media have had the problem of insufficient runnability and durability, particularly in the case of high-density recording.

In order to solve these conventional difficulties, the present inventor conducted intensive research on the relationship between the particle size of carbon, its state on the surface, and running performance and durability. When protruding at a specified density,
It was discovered that running performance and durability were significantly improved, and the present invention was completed.

Therefore, an object of the present invention is to provide a magnetic recording medium with excellent running properties and durability.

[Structure of the Invention] (Means for Solving the Problems) The magnetic recording medium of the present invention is a magnetic recording medium in which a magnetic layer containing magnetic powder, a binder, and carbon is formed on a non-magnetic support. In this case, carbon having a particle size of 100 to 400 nm is deposited on the surface of the magnetic layer at 1(μn+
) per 2, total area o, oos ~ 0.04 (μm)
It is characterized by the presence of 2.

The carbon used in the present invention may have a particle size within the above range and may be used alone, but for example, a particle size of 30 nm may be used.
A certain amount of conductive carbon may also be used.

In the present invention, the size and area of the carbon present on the surface of the magnetic layer are limited as described above because if the carbon size exceeds 400 nm, the exposed particles are large. The pacing becomes large and the output decreases, and the exposed area becomes 0.04 (
μm) If it exceeds t, a good S/N ratio cannot be obtained,
On the other hand, if the thickness of the carbon is less than 10 On1 or the protruding area is less than 0.006 (μm)2, the effects of the present invention cannot be obtained.

Carbon in the present invention is usually blended in the magnetic layer in an amount of 2 to 5% by weight.

Commercially available carbon that can be used in the present invention includes RAVE
N MTP (DD Nbia Carhon Co., Ltd.), TII
Examples include ER, WAXN-990, TRHAX up (manufactured by Cancarb), and HTCI (manufactured by Sepacab).

Curable resins, particularly polyurethane resins, are suitable as the binder used in the magnetic layer of the present invention. Examples of such polyurethane resins include N-2301, N-2304, and B manufactured by Nippon Polyurethane Industries.

Erasen 5F03 manufactured by F. Gutdrich can be mentioned. It is also preferred to use Nido0 cellulose together with these polyurethane resins. Examples of such nitrocellulose include FM-20 manufactured by Daicel Corporation.
I can list 0. As the curing agent used for these curable resins, isocyanate-based curing agents are preferred.

Examples of isocyanate-based hard and other agents include Coronate L1 Takeda Pharmaceutical manufactured by Nippon Polyurethane Kogyo Co., Ltd. and Takenate XL-10007 manufactured by Shina Kogyo Co., Ltd. Note that the binding material used in the present invention is not limited to such a curable resin, and a non-curable resin may be used as necessary.

The ferromagnetic powder used in the magnetic layer of the present invention includes CO
-7re20, etc., acicular iron oxides, CrO2, Fe-C
It is also possible to use metal powder such as o, but it is flat root-like and has a plate-like ratio in the range of 1 to 15, and the particle size is o, oos~
Coercive force (Hc) is 200 to 2000 Oe at 0.03μ garden
Uniaxially anisotropic hexagonal ferrite powder is suitable;
In particular, it has the above-mentioned plate diameter and thickness and the above-mentioned coercive force, general formula % formula %) (wherein H represents any one element of Ba1Sr, Pb, Ca, and n represents a number from 5 to 6. .However, Fe
Some of them are Ti, Co, Zn, In1Hn, Cu
1Ge, Nb, Zr.

It may be substituted with a metal such as vl ^β or Sn. )
A uniaxially anisotropic hexagonal ferrite powder shown in is suitable. Note that the magnetic layer contains aluminum oxide, Crz0
An abrasive such as No. 3, a lubricant such as stearic acid, butyl stearate, etc. can also be blended.

Further, as the non-magnetic support used in the present invention, known ones used as bases for various magnetic tapes, floppy disks, etc. can be used. For example, as a tape base, polyester film etc. but,
Polyester sheets and aluminum substrates are also used as floppy disk bases.

The magnetic recording medium of the present invention includes the above-described carbon, a binder,
It is manufactured by applying a magnetic paint containing magnetic powder or the like onto a non-magnetic support, drying it, and then calendering if necessary and then molding it into a predetermined shape.

(Function) In the magnetic recording medium of the present invention, since a portion of carbon is partially exposed on the surface of the magnetic recording medium, *m is reduced and good runnability and durability are exhibited.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples. Note that "parts" in the following examples indicate parts by weight.

Example 1 3a ferrite (Co, Ti substituted) powder (average particle size 0,
08μ, Hc 700Oe) 100 parts Nitrocellulose 12 parts Polyurethane resin 18 parts Carbon
3.0 parts [THERHAX up (manufactured by Cancarb, average particle size 270 rv)] Lecithin 2.1 parts Stearin! 1.2 parts Butyl stearate 2.5 parts Solvent
225 parts of the above composition were mixed in a sand grinder. [After preparing the magnetic paint, it was filtered, and 5 parts of a trifunctional low-molecular isocyanate compound as a hardening agent was added and mixed.
This paint was applied to both sides of polyethylene terephthalate with a thickness of 75 μm so that the thickness after drying was 2.5 μm.
A magnetic layer was formed by drying and hardening, mirror-finished with a calendar, and punched into a disk shape to produce a magnetic disk.

Example 2 A magnetic disk was produced in the same manner as in Example 1 except that the amount of carbon used in Example 1 was changed to 2.0 parts by weight.

Example 3 A magnetic disk was produced in the same manner as in Example 1, except that the amount of carbon used in Example 1 was changed to 4.0 layers.

Comparative Example 1 A magnetic disk was produced in the same manner as in Example 1 except that carbon was removed from the formulation in Example 1.

Comparative Example 2 A magnetic disk was produced in the same manner as in Example 1 except that the carbon content n used in Example 1 was changed to i and o parts by weight.

Comparative Example 3 A magnetic disk was produced in the same manner as in Example 1 except that the amount of carbon used in Example 1 was changed to 8.0 parts by weight.

Example 4 Instead of the carbon used in Example 1, H manufactured by Sepacab Co., Ltd.
A magnetic disk was produced in the same manner as in Example 1, except that 3.0 parts by weight of Ding CI (average particle size: 350 nll) was blended.

Example 5 A magnetic disk was produced in the same manner as in Example 1 except that the amount of carbon used in Example 4 was 2.0 parts by weight.

Example 6 A magnetic disk was produced in the same manner as in Example 1 except that the carbon blend m used in Example 4 was changed to 4.0 min.

Comparative Example 4 A magnetic disk was produced in the same manner as in Example 1, except that the blend m of carbon used in Example 4 was changed to 1.0 parts by weight.

Comparative Example 5 A magnetic disk was produced in the same manner as in Example 1 except that the amount of carbon used in Example 4 was 6.0 parts by weight.

Example 7 In place of the carbon used in Example 1, T manufactured by Cancarb was used.
hermax up was experimentally classified and the average particle size was 2G0.
A magnetic disk was produced in the same manner as in Example 1, except that a 3.0-type opening was mixed with a magnetic disk having the same composition as Example 1.

Comparative Example 6 In place of the carbon used in Example 1, T manufactured by Cancarb was used.
herlaX tll) was experimentally classified and the average particle size was 1.
A magnetic disk was produced in the same manner as in Example 1, except that 3.0 parts by weight of 50rv) was added.

Comparative Example 7 Instead of the carbon used in Example 1, H manufactured by Sepacab Co., Ltd.
A magnetic disk was prepared in the same manner as in Example 1, except that 3.0 parts by weight of TCI which had been experimentally classified and had an average particle size of 450 nm was added.

Comparative Example 8 Cabot's S was used instead of the carbon used in Example 1.
tering NS) (75 nm) 3,
A magnetic disk was produced in the same manner as in Example 1 except that 0 part by weight was added.

Table 1 shows the average particle size of carbon used in the above Examples and Comparative Examples, the addition M, and the projected area of carbon per 1 (μm) 2 of the media surface, the friction coefficient of the media, the durability,
and the playback output are shown in Table 2.

Durability is determined by loading each magnetic recording medium into a recording/reproducing device and sliding the magnetic head against it with a pad pressure of 400/d until the reproduction output becomes 10% of the initial output. The output is headgear! ? The recording current using a ferrite head with a 0.4 μm fog is shown as a relative value when the reproduction output of Comparative Example 3 is expressed as OdB using the optimum value for each magnetic recording medium.

(The following is a blank space) Table 1 Table 2 [Effects of the Invention] As is clear from the above examples, the magnetic disk of the present invention has excellent running performance and durability.

Claims (4)

[Claims] (1) In a magnetic recording medium in which a magnetic layer containing magnetic powder, a binder, and carbon is formed on a non-magnetic support, carbon having a particle size of 100 to 400 nm is coated on the surface of the magnetic layer. per 1 (μm)^2, the total area is 0.
006 to 0.04 (μm)^2. (2) The magnetic recording medium according to claim 1, wherein the magnetic layer contains 2 to 5% by weight of carbon having a particle size of 200 to 350 nm. (3) The magnetic powder is plate-shaped, and the plate-like ratio is 1 to 1.
3. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is a uniaxially anisotropic hexagonal ferrite powder having a grain size of 0.005 to 0.3 μm. (4) Coercive force of uniaxially anisotropic hexagonal ferrite powder (
The magnetic recording medium according to any one of claims 1 to 3, wherein Hc) is 200 to 2000 Oe.