JPH02143914A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To form a magnetic alumite (anodized aluminum) layer which is hardly peelable from a substrate and to obtain good perpendicular magnetic characteristics by specifying the layer thickness, pore size and the ratio of the pore size and the average distance between the pores and pores of the alumite layer. CONSTITUTION:The film thickness of the alumite layer of the magnetic recording medium plated and packed with Fe into the fine pores of the alumite layer on a nonmagnetic substrate is below 0.5mum and the pore size Dp is below 400Angstrom . The pore size Dp and the average distance Dc between the centers of the pores and the pores simultaneously satisfy the relation 0.4<=Dp/Dc<=0.7. Namely, flexibility can be maintained as the film thickness of the magnetic alumite layer is below 0.5mum. The breakage of the pores and the peeling of the magnetic layer arise hardly even if the medium is bent as the pore size is below 400Angstrom . On the other hand, the pore size and the cell size has the relation 0.4<=Dp/Dc<=0.7 and, therefore, the good perpendicular magnetic characteristics are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium. More specifically, the present invention relates to a flexible magnetic recording medium in which peeling of an alumite magnetic layer is less likely to occur.

[Prior Art] A magnetic recording medium in which a ferromagnetic material is plated and filled into the fine pores of an alumite layer formed by anodizing the surface of aluminum or an aluminum alloy has corrosion resistance,
It is a new material that is highly durable and has been attracting particular attention recently.

In this type of magnetic recording medium, the saturation magnetization (MS) of the film is
It is a value obtained by multiplying the ratio of the area of the entire membrane to the total area of all pores (porosity, α) by the saturation magnetization (ms) of the metal to be filled. Alumite forms regular hexagonal cells with a diameter DC,
Assuming that the film has a micropore with a diameter Dp at its center, the saturation magnetization (Ms) of the film is expressed by the following equation.

Ms=ms *yr/213 (Dp/Dc) 2 Generally, there is DI between Dp and Dc! =f1/3・
There is a relationship of D c. Therefore, Ms of the alumite magnetic film
is Ms = ms e yr/ 18v'3, and further h to calculate the constant term, Ms = 0.1 ms.

Therefore, iron, which has a large saturation magnetization, is used as the magnetic metal to fill the alumite magnetic film.

[Problems to be Solved by the Invention] However, since a magnetic recording medium in which the fine pores of an alumite magnetic layer are plated and filled with a ferromagnetic metal such as Fe has high rigidity, it has conventionally been possible to use a substrate made of aluminum or glass. It was only applied to rigid disks using .

Attempts were made to apply this to flexible media such as magnetic tape, but the alumite magnetic layer easily peeled off, so it was not put to practical use.

In addition, even when plated with Fe, the saturation magnetization of the plated film (
Ms) is about 170 emu/cc, and the saturation magnetization used in CoCr alloy thin film is 350 emu/cc-5.
This is extremely small compared to 50 emu/cc. If the saturation magnetization is small (and the magnetostatic properties of the plated film are equivalent to CoCr,
There is a problem with low playback output.

Therefore, an object of the present invention is to determine the structure of anodized aluminum that makes it easy to peel off from the substrate and provides good perpendicular magnetic properties when the alumite magnetic layer is applied to flexible media such as tape or floppy disks. .

[Means for Solving the Problems] In the present invention, as means for achieving the above object,
F in the micropores of the alumite layer of non-magnetic substrate-L
In a magnetic recording medium filled with pores, the thickness of the alumite layer is less than 0.5 μm, and the pore diameter (
Dp) is less than 400, and the pore diameter (DI))
and the center SV average rough distance cell diameter, Dc) between pores is 0
．． To provide a magnetic recording medium characterized in that drops are simultaneously deposited in a relationship of 4≦Dp/Dc≦0°7.

It is preferable that 0.48≦Dp/Dc≦0.60.

Preferably, the magnetic recording medium is a magnetic tape.

[Function] As described above, in the magnetic recording medium of the present invention, the thickness of the alumite magnetic layer is less than 0.5 μm, so that flexibility can be maintained. Furthermore, since the pore diameter is less than 400 mm, even if the medium is bent, pore destruction and magnetic layer peeling hardly occur. On the other hand, the pore diameter and cell diameter are 0.4≦Dp/Dc≦0
．． 7, good perpendicular magnetic properties are achieved.

[Example] When DI)/Dc is less than 0.4, the film is excellent as a perpendicularly magnetized film, but the saturation magnetization (Ms) is too small, resulting in insufficient reproduction output. On the other hand, when Dp/Dc exceeds 0.7, the porosity (α) becomes large and approaches that of an in-plane magnetized film, and the characteristics as a perpendicular medium are lost.

In the case of flexible media such as magnetic tape and floppy disks, the thickness of the magnetic layer is 0.5 μm in consideration of flexibility.
The thickness should preferably be 0.25 μm or less.

Therefore, the length of the Fe pillars filling the alumite micropores is also 0.
5 μm ungrooved 1 preferably 0.25 μm or less.

The pore diameter is less than 400, but preferably about 220 to 280.

Referring to the magnetic properties of the CoCr perpendicular magnetization film, the saturation magnetization of the alumite magnetic film of the present invention is 350 to 550.
emu/cc1 500 to 100 as coercive force in the vertical direction
A magnetostatic property of 00e is required. As described above, the saturation magnetization of the alumite magnetic film is the value obtained by multiplying the porosity (α) by the saturation magnetization of Fe filled with In (1714 emu/cc). Therefore, in order to obtain a saturation magnetization of 350 to 550 emu/cc, if porosity (α) is 0.20 to 0.
It is preferably within the range of 32.

On the other hand, when Ms is within the range of 350 to 550 emu/cc,
In addition, the coercive force in the %iα direction is 500 to 10000e, and in order to exhibit characteristics as a perpendicular magnetization film, the filled Fe
An axial ratio of ~10 is required. If the preferred alumite film thickness (corresponding to the long axis length of Fe) is 0.25 μm in consideration of applications such as magnetic tape, the diameter (Dp) of the alumite micropores will be 220 to 280 μm.

Also, from α=π/2f311(Dp/Dc)2, considering the value of α, 0.20 to 0.32, and the preferable value of Dp, 220 to 280 people, the difference between the pores and the pores. The center average distance or cell diameter Dc is 400 to 50
Preferably, the number is within the range of 0 people.

The magnetic recording medium of the present invention includes magnetic tapes and magnetic disks having synthetic resin films such as polyester films and polyimide films as their bases, but magnetic tapes are most preferred.

Hereinafter, the present invention will be explained in more detail by giving specific examples.

Jitton LLL Using a continuous winding type vacuum evaporation device, PE with a thickness of 20 μm is
A film of 0.3 μm of AI was formed on the T film. The substrate temperature was room temperature, the vacuum level during evaporation, and the film formation rate were 3xlO.
""'Torr, 35 people/seC.

The prepared Aλ membrane was placed in 1 mol/Jl of sulfuric acid,
Anodization was carried out at 2°C for 1 minute at a current density of IA/d/. The thickness of the alumite film produced was 0.25 μm, and the cell diameter
Pore diameters are 0.046 μm and 0.015 μm, respectively.
It was m. Next, the sample was immersed in a 1 wt % phosphoric acid solution at 30° C. to enlarge the pore diameter.

FIG. 1 shows the relationship between the pore diameter I)p and the square porosity α.

From this figure, in order to set the porosity to 0.20 to 0.32,
It can be seen that the pore diameter should be set to 0.022 to 0.02811 m.

L Master 1 Alumite having various pore diameters prepared in Example 1 was filled with Fe by plating. Fe plating bath composition: Mohr salt 15g/300mJ, glycerin 0.8mJ/300m
The pH was adjusted to 3.0 with 2N sulfuric acid.

The power supply used for plating was 5 AC, 500 Hz *
Apply DC bias at 15 V p-p to the + side (
1Ov was applied to the 5V1- side (alumite) on the carbon electrode).

Figure 2 shows the relationship between pore diameter and saturation magnetization (MS)% perpendicular coercive force (Hc). Pore diameter 0゜022μm~0
．． By setting it to 028 μm, Ms is 350 to 550 em
It is possible to make it u/cc. In addition, the pore diameter is 0.
In the region larger than 027μm, Hc is ~10000e
A magnetic film is obtained.

Real part'' 11 A, l' film prepared in Example 1 was 22゛C13wt5G
Anodization was performed at 40 V in an oxalic acid bath to form an alumite layer of 0.35 μm. The cell diameter and pore diameter at this time were 0.098 μm and 0.030 μm, respectively.

Thereafter, the pores were enlarged in a 11 wt % phosphoric acid bath at 30° C. to prepare samples with pore diameters ranging from 0.03 μm to 06 μm. Next, by the method described in Example 2, Fe was filled into the fine pores of the alumite by plating.

1 c of alumite/Fe plating membranes with various pore diameters
A reciprocating sliding test was performed on the sample by cutting it into a rectangular shape of m x 10 ca and using a stainless steel pin with a diameter of 2 ma+. The load and sliding speed during the test were 18g + 5c, respectively.
m/see, and the test was carried out by bringing the PET film into contact with a stainless steel pin. Cracks in the magnetic surface were observed using a light microscope, and the number of sliding movements until cracks occurred was determined.

FIG. 3 shows the relationship between the number of sliding movements at which cracks occur and the pore diameter of alumite. As is clear from the figure, the pore diameter is 400
It can be understood that cracks on the magnetic VI surface are more likely to occur in the reciprocating sliding test when the test time exceeds that of a person.

[Effects of the Invention] 1. As explained above, in the magnetic recording medium of the present invention, since the layer thickness of the aluminum layer is less than 0.5 μm, the lJ jA property can be maintained.

Furthermore, since the pore diameter is less than 400 mm, even if the medium is bent, pore destruction and magnetic layer peeling hardly occur. On the other hand, since the pore diameter and the cell diameter have a relationship of 0.4≦Dp/I) c≦0.7, good perpendicular magnetic properties are achieved.

Due to these characteristics, the magnetic recording medium of the present invention is particularly suitable for long media such as magnetic tape.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram showing the relationship between pore diameter and square porosity, showing an example according to the present invention. FIG. 2 is a characteristic diagram showing the relationship between pore diameter, saturation magnetization, and perpendicular coercive force, showing one embodiment of the present invention. FIG. 3 is a characteristic diagram showing the relationship between the pore diameter and the number of reciprocating sliding movements.

Claims (3)

[Claims] (1) In a magnetic recording medium in which the fine pores of an alumite layer on a nonmagnetic substrate are filled with Fe by plating, the layer thickness of the alumite layer is less than 0.5 μm, and the pore diameter (Dp)
is less than 400 Å, and the pore diameter (Dp) and the average distance between pores (cell diameter, Dc) are 0.4≦Dp
A magnetic recording medium characterized in that it simultaneously satisfies the relationship: /Dc≦0.7. (2) The magnetic recording medium according to claim 1, wherein 0.48≦Dp/Dc≦0.60. (3) The magnetic recording medium according to claim 1 or 2, which is a magnetic tape.