JPH0620273A - Field orienting method for magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having high rectangularity ratio by performing orientation while setting the range in the traveling direction of low field region applying high intensity field five times or more of the range in the traveling direction for applying field of specific intensity. CONSTITUTION:Maximun intensity of field being applied by a high field coil 2 is Hmax and the range in the traveling direction of high field region for applying field intensity of 90% or above is L1. Field to be applied by a low field coil 3 in post-stage is set at 20% or below of Hmax and the range in the traveling direction of low field region being applied with field through the coil 3 is L2. The range L2 is set five times or more of the range L1. When a nonmagnetic support 4 is subjected to coating and then subjected to orientation through the coil 2 generating a strong field, magnetic powder once oriented by passing weak field generated from the coil 3 for sufficiently long time can be oriented again at random. This method provide an inexpensive coil 3, realizes low cost high efficiency orientation, and produces a magnetic recording medium having high rectangularity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic field orientation direction of a magnetic recording medium, and in particular, a magnetic coating mainly composed of magnetic powder and a binder is applied to a running non-magnetic support and then a magnetic field is applied by an electromagnet. The present invention relates to a magnetic field orientation method for a magnetic recording medium, which aims to reduce the processing cost and improve the orientation efficiency in the method of magnetic field orientation processing by applying the magnetic field.

[0002]

2. Description of the Related Art Conventionally, as a method of magnetic field orientation treatment of a coating type magnetic recording medium, for example, a non-magnetic support coated with a magnetic coating is run in a cylindrical or square solenoid coil, and A method has been proposed in which a magnetic field is applied while the magnetic support passes through the inside of the solenoid coil so that the magnetic powder is oriented in a desired direction.

[0003]

In the magnetic field orientation treatment using the solenoid coil, the magnetic powder is oriented in the range where the magnetic field is applied, but the applied magnetic paint passes through the coil in an undried state. If it does, a part of the oriented magnetic powder will be randomized. Therefore, in order to obtain a high orientation ratio, it is necessary to set the length of the coil over the entire range until the applied magnetic paint dries. However, since the magnetic field strength of 3 to 7 kOe is usually required in the orienter using the solenoid coil, the equipment is not installed in order to install the coil having such a magnetic field strength in a long range until the magnetic paint dries. It has the drawback of being extremely expensive and using a huge amount of power.

For this reason, in an ordinary orienter, the length of the coil is not set in such a range that the magnetic paint after application is completely dried, but a strong magnet is provided in several places. Therefore, the squareness ratio indicating the degree of orientation of the obtained magnetic recording medium is 0.80 to 0.90.
It was not a value that was sufficiently satisfactory.

The present invention solves the above-mentioned conventional problems, and in a method of applying a magnetic coating on a running non-magnetic support and then applying a magnetic field by an electromagnet to perform a magnetic field orientation treatment, at a lower cost, Alignment treatment with extremely high alignment efficiency,
An object of the present invention is to provide a magnetic recording medium magnetic field orientation method for obtaining a magnetic recording medium having a high squareness ratio.

[0006]

A magnetic field orientation method for a magnetic recording medium according to the present invention comprises applying a magnetic field after applying a magnetic coating mainly composed of magnetic powder and a binder onto a running non-magnetic support. In the magnetic field orientation method of a magnetic recording medium in which the magnetic field orientation treatment is performed with
and _max, the running direction of the length range of the high magnetic field region providing a magnetic field more than 90% of the field strength of said maximum field strength H _max and L _1, the maximum magnetic field strength H 0 below 20% _max
If% the running direction of the length range of the low magnetic field region providing a magnetic field of greater field strength than the L _2, together with the L ₂ to 5 times or more of the L _1, said high and low magnetic field region It is characterized in that it is provided on the rear side of the traveling direction with respect to the magnetic field region.

[0007]

In the magnetic field orientation method of the magnetic recording medium of the present invention, a high strength magnetic field is applied to the magnetic coating material in a high magnetic field area to perform an efficient orientation, and then in a low magnetic field area in a subsequent stage, A weak magnetic field is applied for a sufficiently long time to prevent the oriented magnetic powder from being randomized and to dry the magnetic paint.

That is, after applying a magnetic coating material to a non-magnetic support, it is passed through a coil that generates a large magnetic field for orientation, and then a coil that generates a weak magnetic field is passed for a sufficiently long time to perform orientation once. Randomization of the magnetic powder can be prevented. To prevent this randomization, a very small magnetic field is sufficient, so the coil and power supply in the low magnetic field region will be much cheaper, and the current to be carried will be less, and therefore the power consumption will be much less, It is extremely economical.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 (a) is a schematic sectional view showing an example of a magnetic field orientation apparatus suitable for the magnetic field orientation method for a magnetic recording medium of the present invention, and FIG. 1 (b) is a running line of this magnetic field orientation apparatus. It is a graph which shows a magnetic field distribution.

In the figure, 1 is a magnetic paint coating device, 2 is a coil for generating a high magnetic field (hereinafter referred to as "high magnetic field coil"), 3 is a coil for generating a low magnetic field (hereinafter referred to as "low magnetic field coil"). 4 is a non-magnetic support which is fed from a feeding device (not shown) and runs in the direction of arrow A.

In the method shown, the traveling non-magnetic support 4
After applying a non-magnetic coating material mainly composed of magnetic powder and a binder by the coating device 1, first, in the high magnetic field coil 2,
After applying a high intensity magnetic field to orient the magnetic powder, a weak magnetic field is applied by the low magnetic field coil 3 to prevent randomization of the magnetic powder and dry the magnetic paint here.

In this embodiment, as shown in FIG. 1 (b), the maximum strength of the magnetic field applied by the high magnetic field coil 2 is H _max, and a high magnetic field strength of 90% or more of H _max is applied. When the length range L ₁ of the region in the traveling direction is set, the magnetic field applied by the low-field coil 3 in the subsequent stage is set to H
20% or less of _max , and the length range L ₂ in the running direction of the low magnetic field region to which the magnetic field is applied by the low magnetic field coil 3.
Is 5 times or more, preferably 10 times or more of L ₁ .

In the present invention, the maximum strength H _max of the applied magnetic field varies depending on the required characteristics of the magnetic recording medium to be manufactured, the type of magnetic powder, etc.
Therefore, it is preferable to use a coil that generates such a magnetic field as the high magnetic field coil.
As the low magnetic field coil, one generating a magnetic field of 50 to 1000 Oe is preferable.

The present invention will be described more specifically below with reference to experimental examples and examples.

Experimental Example 1 Using the experimental apparatus shown in FIG. 2, the sensitivity of the magnetic paint to the magnetic field was examined. In this apparatus, a sample containing the magnetic paint 11 is placed in a hole piece 13A, 1 around which a coil 12 is wound.
3B, a pulsed magnetic field is applied, and the temporal change of the magnetization of the sample at that time is examined. 14, 15
Is a Hall element for measuring the magnetization and magnetic field of the sample and the strength of the magnetic field, and the strength of the magnetization is determined by (measured value of element 14-measured value of element 15). Magnetic paint 1
Since the magnetic powder can rotate freely in 1, the intensity of the measured magnetization is considered to be proportional to the degree of orientation of the magnetic powder,
The degree of orientation can be estimated from the change over time in the strength of magnetization.
In addition, 16 is a power supply and 17 is a digital recorder.

FIG. 3A is a graph showing a magnetic field generated by the coil 12 having a pulse width of 200 ms and a maximum intensity of 5 kOe. This magnetic field was applied to a sample of the magnetic paint 11 containing Co-γFe ₂ O _3. FIG. 3B shows the change over time in the strength of the magnetization in the case of In this state, when the traveling speed of the non-magnetic support is 2 m / s, the magnetic field strength near the center is 5 k.
This is almost the same as the magnetic field received by the magnetic paint on the non-magnetic support when passing through the orientation coil having a distance of 30 to 50 cm in the web running direction at Oe. As is clear from FIG.
The magnetization intensity of the sample due to the pulsed magnetic field gradually decreases after the magnetic field intensity becomes zero. This indicates that the magnetic powder once oriented by the magnetic field becomes randomized again.

FIG. 4 (a) gives exactly the same pulsed magnetic field as shown in FIG. 3 (a), after which 100 Oe is applied.
4B shows the magnetic field strength distribution when a very weak constant magnetic field of 1 is continuously applied to the sample, and FIG. 4B shows the change over time of the magnetization strength when the magnetic field is applied to the sample. As is clear from FIG. 4, when the weak magnetic field is continuously applied after the pulse magnetic field as shown in FIG. 3, the decrease of the magnetic field strength of the sample is extremely small.

FIG. 5 shows the change over time in the strength of magnetization when only a constant magnetic field of 100 Oe was applied to the magnetic paint sample. As is clear from FIG. 5, at such a weak magnetic field strength, It can be seen that the magnetic powder is hardly oriented.

From these results, in the magnetic paint,
It is presumed that the magnetic powder is hard to rotate only in a small magnetic field, but once the magnetic powder moves in a large magnetic field, the magnetic powder becomes easy to move immediately after that and easily moves even in a small magnetic field. Therefore, in the orientation of the magnetic recording medium, first, a coil that generates a large magnetic field is first passed through, and then a coil that generates a weak magnetic field is installed at the subsequent stage side of the coating line, and this is passed to efficiently It is clear that it can be oriented.

Example 1 Using the device shown in FIG. 1, Co-γF was formed on a non-magnetic support.
A magnetic recording medium was manufactured by applying a magnetic coating material containing e ₂ O ₃ and then subjecting it to orientation treatment according to the present invention.

That is, a coil for generating a magnetic field of 5 kOe was used as the high magnetic field coil, and a coil for generating a magnetic field of 100 Oe was used as the low magnetic field coil.

Further, with respect to the length range L ₁ of the high magnetic field region to which a magnetic field of 90% or more of the maximum intensity of the magnetic field (that is, 4.5 kOe or more) is applied, the length range of the low magnetic field region by the low field coil is set. L ₂ was set to be about 10 times as large as L ₁ .

As a result, the squareness ratio of the obtained magnetic recording medium was 0.93, which was remarkably high.

On the other hand, when a high magnetic field coil was used instead of a low magnetic field coil and the same orientation treatment was performed, the obtained magnetic recording medium had a squareness ratio of 0.81. According to the invention, it was confirmed that the squareness ratio can be significantly improved as compared with the conventional one.

Since the low magnetic field coil is much cheaper than the high magnetic field coil in terms of the cost of the coil and the power consumption, the cost increase by providing the low magnetic field coil is negligible, and the high magnetic field coil alone has the same degree. Compared with the case of achieving the squareness ratio of 1), a significant cost reduction was achieved.

[0027]

As described in detail above, according to the magnetic field orientation method for a magnetic recording medium of the present invention, randomization of magnetic powder once oriented is prevented by optimizing the distribution of the magnetic field strength in the running direction. To improve the orientation efficiency and suppress the applied magnetic field strength to reduce equipment cost and power cost.
A magnetic recording medium having a high squareness ratio can be obtained at low cost.

The highly oriented magnetic recording medium manufactured by the method of the present invention has a high output and also has a good surface property of the medium, which reduces noise and can be effectively used as a medium for high recording density. In addition, since the error rate is extremely low, it is extremely useful industrially.

[Brief description of drawings]

1A is a schematic sectional view showing an example of a magnetic field orientation apparatus suitable for a magnetic field orientation method for a magnetic recording medium of the present invention, and FIG. 1B is a running line of the magnetic field orientation apparatus. 3 is a graph showing the magnetic field distribution of

FIG. 2 is a configuration diagram showing an outline of an experimental device used in Experimental Example 1.

FIG. 3 (a) is a graph showing a pulsed magnetic field,
FIG. 3B is a graph showing the change over time of the magnetization intensity of the sample when the magnetic field of FIG.

FIG. 4 (a) is a graph showing a pulsed magnetic field and a weak magnetic field thereafter, and FIG. 4 (b) is a time change of the magnetization intensity of the sample when the magnetic field of FIG. 4 (a) is applied. It is a graph which shows.

FIG. 5 is a graph showing the change over time of the magnetization intensity of a sample when only a weak magnetic field is applied.

[Explanation of symbols]

 1 coating device 2 high magnetic field coil 3 low magnetic field coil 4 non-magnetic support

Claims (1)

[Claims] 1. A magnetic field orientation method for a magnetic recording medium, which comprises applying a magnetic coating mainly composed of magnetic powder and a binder onto a running non-magnetic support and then applying a magnetic field to perform magnetic field orientation treatment. The maximum strength of the magnetic field on the coating surface of the coating material is H _max, and the length range in the running direction of the high magnetic field region that gives a magnetic field of 90% or more of the _maximum magnetic field strength H _max is L ₁ , and the maximum magnetic field is If the running direction of the length range of the low magnetic field region providing a magnetic field of greater field strength than 0% below 20% strength H _max was L _2, and the L ₂ 5 times or more of the L ₁ At the same time, the magnetic field orientation method for a magnetic recording medium is characterized in that the low magnetic field region is provided on a rear side of the high magnetic field region in the traveling direction.