JPH06223353A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the recording medium whose durability and preservation property are good by a method wherein pillar-shaped ultrafine particles constituting a magnetic layer are formed in such a way that they are curve-shaped and that their thickness in the thickness direction is nearly definite. CONSTITUTION:The surface of a granular property is formed of inherent particles, surface coating particles on a polymer film 6 composed of polyethylene terephthalate or the like. Pillar-shaped particle groups 7 are observed, by a scanning electron microscope, on a face which has been fractured in the length direction and the width direction, and their particle size is preferably at 0.05 to 0.01mum. Their particle size is made nearly identical, e.g. in a face through a1-a2 and a face through b1-b2 which are parallel to a substrate face through P1-P2, the particle groups are curve-shaped, and the size of the pillar-shaped particles is controlled by combining a magnetic material, a temperature, a vapor-deposition speed, a vacuum degree and the like. Co-Cr, Fe, Co-Pt-O or the like is used as the magnetic material. Thereby, a magnetic recording material whose durability is good and whose S/N ratio is high can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium having a magnetic layer of a ferromagnetic metal thin film suitable for high density magnetic recording.

[0002]

2. Description of the Related Art With the progress of information society, the amount of information to be recorded is remarkably increasing, and it is required to increase the recording density of magnetic recording as much as possible. Development of magnetic recording media has been brisk. Although many proposals have been made, Co-Ni-O
Oblique vapor deposition film [JP-A-53-58206 and JP-A-5
6-15014, etc.] A magnetic recording medium having a ferromagnetic metal thin film as a magnetic layer, which is represented by a Co—O perpendicular magnetized film [JP-A-4-176015], is promising and has a laminated structure for improving noise. Magnetic layers [JP-A-4-229413 and JP-A-4-76813] have also been proposed.

A conventional magnetic recording medium will be described below. FIG. 2 shows an enlarged cross section of a conventional magnetic recording medium.

In FIG. 2, reference numeral 1 denotes a polymer film of polyethylene terephthalate, polyethylene naphthalate or the like, which has a so-called fine particle coating layer in which inorganic ultra fine particles such as SiO ₂ and ZnO and organic ultra fine particles such as imide are dispersed and applied. Often used. Reference numeral 2 denotes a Co—Ni—O single-layer or multi-layered ferromagnetic metal thin film formed by oblique vapor deposition with a continuously changing incident angle, Co—Cr, Co—O.
A magnetic layer such as a perpendicular magnetization film formed by tilted vapor deposition of 3 is a protective film such as an oxide film, a nitrogen film, and a plasma polymerization film, 4 is a fatty acid,
A lubricating layer made of fluorine oil or the like, and 5 is a back coat layer having good smoothness, which is often seen in thin magnetic tapes.
In the magnetic recording medium having the above-described structure, the magnetic layer is formed by moving along a rotating can or a rotating belt in an oxygen atmosphere on a polymer film on which a fine particle coating layer is formed by a solution coating method in a separate process. In many cases, Co, Co-Ni, etc. are deposited by electron beam evaporation at a certain incident angle.

The operation of the magnetic recording medium having the above structure will be described below. For example, a strip-shaped magnetic recording medium is stored in a cassette, and when access is required, a part of the cassette is released by releasing the hermeticity, moved at a constant speed and used for recording and reproduction. The extracted magnetic recording medium is a ring-type magnetic head mounted on a rotating cylinder that rotates at high speed to convert an electric signal into a residual magnetization pattern, which is recorded in a magnetic layer and reproduced by reverse conversion. It is required to endure repeated sliding in order to secure a high speed relative speed between the magnetic head and the tape because the principle of (3) is used. Therefore, the magnetic layer made of a ferromagnetic metal thin film has the purpose of making particles finer by the action of oxygen, achieving a higher coercive force, improving weather resistance, and mitigating friction with the sliding partner to prevent cohesive wear. Various protective lubrication systems have also been proposed in. Above all, attention has been paid to the prevention of adhesion by a carbon film having an increased hardness (Japanese Patent Laid-Open No. 53-143026). In order to improve the adhesiveness with a ferromagnetic metal thin film and to improve the still durability as a video tape, SiO is used. _{One in} which an amorphous carbon film is arranged through _two films (Japanese Patent Laid-Open No. 61-242323)
Amorphous carbon film disposed through an organic plasma polymerized film (JP-A-62-167616) A carbon film disposed through a carbon carbide film (JP-A-64-79)
No. 932) has been proposed.

[0006]

However, in the above conventional structure, the durability becomes insufficient as the carbon film becomes thinner, and the phenomenon becomes more remarkable as the thickness of the magnetic recording medium becomes thinner. In particular, in order to improve the recording density by narrowing the track, a magnetic recording medium with high output and good durability is required. Even if the carbon film is thickened to improve the durability, S /
There is a problem that the density is insufficient because the N ratio is lowered. Further, there is a problem that the weather resistance is not sufficient because the range of use is widened.

The present invention solves the above-mentioned conventional problems, and an object thereof is to provide a thin magnetic recording medium having both durability and high output characteristics, which enables narrow track high density recording.

[0008]

In order to achieve this object, the magnetic recording medium of the present invention is such that the columnar fine particles constituting the magnetic layer are curved and the thickness in the thickness direction is substantially constant. It is the one.

[0009]

With this structure, the magnetic field is saturatedly recorded with a small recording current (small recording magnetic field intensity) in the magnetic layer by the magnetic field formed by the ring head, so that re-erasing can be ignored, and the width of the transition region is narrow and high output is achieved. In addition to, in the thickness direction,
Since the magnetic interaction between the columnar particles becomes uniform, noise is improved, the S / N is significantly improved by both, and the durability of the magnetic layer itself is also improved. Even if the thickness is reduced, the durability is sufficiently ensured, and a thin magnetic recording medium having both the durability and the high S / N ratio can be realized.

[0010]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 6 is a polymer film of polyethylene terephthalate, polyethylene naphthalate, polyether ether ketone, polyimide or the like, which has a grainy surface formed by internal particles or surface-coated particles. Numeral 7 is a group of columnar particles in units of a state in which grain boundaries can be observed by observing a surface broken in a longitudinal direction and a width direction with a scanning electron microscope, which constitutes a magnetic recording layer.
The particle size is preferably 0.05 μm or less and 0.01 μm or more. It is not an aggregate of columnar particles grown in a straight line shape or a shape close to a straight line with respect to the substrate surface, but that the growth direction is changed and bent, and the particle diameter is, for example, a ₁ a ₂ surface as shown in the figure. a requirement that either about the same in a plane parallel to the b ₁ b ₂ side substrate surface p ₁ p ₂ side, such as, the easy magnetization axis direction, of course, the material is particularly limited production method Although it is not a thing, the belt transportation method is adjusted and optimized to reduce the dependence of the deposition rate on the incident angle, and the oxygen gas introduction position is separated from the substrate position.

The columnar particle diameter can be controlled by a combination of magnetic materials, temperature, vapor deposition rate, vacuum degree and the like.

Magnetic materials include Co--Cr, Fe, N,
Co-Pr-O, Co-Tb-Fe, Co-Cr-Ta
Etc. can be used.

The effects of this embodiment will be further clarified below by comparing the concrete example with the conventional example.

A polyimide film having a thickness of 6.8 μm, a Young's modulus of 740 and 790 [kg / mm ² ] in the longitudinal direction and a width direction of 30 Å and a mean roughness of 30 Å was used.
An average of 30 / μ ^{2 of} 80 Å SiO ₂ was applied and fixed, and a magnetic layer was formed thereon. The vapor deposition machine was a winding vapor deposition machine in which a rotary support (−20 ° C.) consisting of an endless belt and an electron beam evaporation source were combined, and Co was vapor-deposited by changing Co from 75 ° to 37 °. The position of the evaporation source is directly above and the distance to the belt is adjusted between 35 and 60 cm, and the angle of the belt is adjusted to 16 to 24 degrees with respect to the normal line to the evaporation source, and The amount of introduction and the vapor deposition rate were adjusted within the range of 0.1 to 3.3 μm / sec to change the particle diameter, and a magnetic layer composed of an aggregate of curved particles having a constant diameter in the thickness direction was formed. In the conventional example, vapor deposition was performed from the tangential direction along a rotary can (-15 ° C.) with a diameter of 1 m, and the minimum incident angle was set to 50 degrees under the condition that the incident angle continuously changed, and the oxygen gas and the vapor deposition rate were adjusted. To form a magnetic layer. The particle diameter was examined by observing the fracture surfaces in the longitudinal direction and the width direction with a high-resolution scanning electron microscope, and in the conventional example, the particle diameter becomes smaller as it gets closer to the substrate surface and the state of the incident angle is reflected. The shaft is bent,
The particle size is expressed by the maximum value. Common thickness is 0.15μ
And In the example and the conventional example, coercive forces in the vertical direction and the in-plane direction are 1600 to 1660 [Oersted] and 13 respectively.
70 to 1410 [Oersted] compared with each other.

A diamond-like carbon film is disposed on the magnetic layer by a plasma CVD method in an amount of 60 Å in the embodiment, and in the conventional example,
60 Å and 140 Å are placed, and perfluoropolyether as a lubricant is further placed on it by a 40 Å solution coating method, a back coat layer is formed 0.45 μm, and a 1/4 inch width magnetic tape is trial-produced to compare the characteristics. went. The characteristics of the respective magnetic tapes are compared with each other by using a prototype digital VTR and comparing the error rates at a recording wavelength of 0.4 μm and a track pitch of 9 μm with a ring head having a gap length of 0.18 μ and a magnetic flux density of 1 Tesla. It was The length of the magnetic tape was 100 m, 5 rolls were randomly selected, and the average value of 5 rolls was displayed. The still characteristics were compared at 40 ° C. and 5% RH by increasing the tension to 25 g. Still characteristic is 40
Comparison was made before and after storage at 85 ° C. and 85% RH for 1 month. The characteristics of the magnetic recording medium according to this example and the characteristics of the magnetic recording medium of the comparative example are shown in comparison with each other (Table 1).

[0017]

[Table 1]

As is clear from (Table 1), the magnetic recording medium according to the present embodiment exhibits good characteristics in high-density digital recording in narrow track recording by the ring head, and also has excellent durability and storage characteristics. It is understood that it is a thing.

As described above, according to this embodiment, the columnar fine particles forming the magnetic layer are curved and the thickness in the thickness direction is substantially constant, so that the track width is narrowed and the height is increased. Excellent characteristics can be stably obtained in density recording, together with durability and storage stability.

[0020]

As described above, according to the present invention, the columnar fine particles constituting the magnetic layer disposed on the polymer film are curved and have a substantially constant thickness in the thickness direction. As a result, it is possible to stably obtain excellent characteristics in high density recording with a narrowed track, together with durability and storability.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view of a magnetic recording medium according to a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a conventional magnetic recording medium.

[Explanation of symbols]

 6 Polymer film 7 Columnar fine particles

Claims (1)

[Claims] 1. A magnetic recording medium, wherein the columnar fine particles constituting the magnetic layer are curved and have a substantially constant thickness in the thickness direction.