JPS60145523A - Magnetic recording medium and its manufacture - Google Patents

Abstract

PURPOSE:To raise outputs and resolution of a reproducing signal, and also to improve S/N by reducing noise of a recording medium, by controlling the surface roughness of the recording medium to a specified range, and bringing a quantitative decrease and a qualitative variation on the surface roughness. CONSTITUTION:Calender processing and lapping processing of a magnetic tape are executed so that a probability distribution in a 50% amplitude level of an Abbot load curve of surface roughness of a magnetic layer on a magnetic recording medium is 0.45-0.9, and also a value of a tertiary moment standardized by a value of the 2/3 power of a secondary moment of a surface roughness curve has a surface roughness distribution of +0.5--1.0. As for this lapping processing, a relative speed between a lapping tape and the magnetic tape is set to 0.1-1.0m/sec, and it is executed under the condition that a pressing force of the lapping tape is set to 2-200g/cm<2>, and the surface roughness is reduced quantitatively, and also its qualitative variation is induced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium. For more details, please refer to information processing or digital VTI? The present invention relates to a magnetic recording medium suitable for recording digital signals such as those for use in other applications, and a method for manufacturing the same.

Unconformed and open.

Conventionally, hard magnetic disks, magnetic tapes, flexible magnetic disks, and the like have been used as media for magnetic recording and reproduction. It can be said that the development goal in the development of these magnetic recording media is high density, specifically high output and high resolution, and a high signal-to-noise ratio (S/N).

In particular, in a recording/reproducing apparatus for digital signals for information processing, it is known that a high S/N ratio is the most important factor determining the signal quality of a recording medium. With the progress and development of these various magnetic recording devices, there has been a demand for magnetic recording media with excellent magnetic properties and medium surface smoothness.

In general, factors that limit the S/N of magnetic recording media include:
There are medium noise and so-called equipment noise caused by the active circuit of the first stage of the regenerative amplifier. Magnetic tape media noise is based on media discontinuities, e.g., J. C. Mallinson.
: ”Maximun Signal-to-Nois
Ellation of a Tape Record
r” + IEEE Trans,onMagn,,
It is described in literature such as HAG-5, pp. 182-186 (1979). In addition, magnetic tape media noise is
During signal recording and reproduction, the signal is modulated by differences in spacing loss caused by the state of contact with the magnetic head, that is, the unevenness of the surface of the magnetic layer, resulting in so-called modulation noise. General magnetic recording devices, especially devices using magnetic tape, are usually designed so that the above-mentioned modulation noise becomes a dominant factor.

Thus, it is desirable that the surface roughness of the magnetic recording medium, which causes magnetic tape modulation noise, be as small as possible.

Current typical magnetic tapes for information processing or flexible magnetic disks have unevenness (surface roughness) with a height of 0.1 to 0.4 μm, but magnetic tapes for high-density digital recording have a height of 0.2 μm in particular. High output and
This is desirable from the viewpoint of high resolution and high S/N.

There are two main methods for reducing the surface roughness of a coated magnetic tape: One of them is to increase the magnetic particle filling rate of the magnetic tape. In other words, coated tape is a so-called discontinuous medium obtained by dispersing magnetic particles in a polymer binder, and the occupancy rate of the magnetic particles and a non-magnetic substance called the polymer binder in the magnetic layer is determined by the volume density. 1/3 of each, the rest being holes.

Therefore, this method is an attempt to increase the volume density of magnetic particles to bring them closer to a continuous medium, thereby improving the surface roughness of the medium. The other method is called calendering, in which after the magnetic layer is applied, the medium is passed between heated metal rollers to flatten the unevenness, especially the convex portions, of the surface of the medium.

In the former method, since the amount of binder surrounding the magnetic particles is relatively reduced, the sliding durability with the magnetic head etc. is significantly deteriorated, and on the other hand, the degree of reduction in surface roughness is relatively small. . As is conventionally known, even in the latter method, the surface roughness of the medium is influenced by the properties of the coating liquid, specifically whether a thermoplastic resin, thermosetting resin, reactive resin, or a mixture thereof is used as the binder material. have different effects. In addition, the influence greatly differs depending on the filling rate of magnetic particles mixed in the coating liquid.

For example, regarding the magnetic particle filling rate, in a magnetic tape for information processing or a flexible magnetic disk medium for information processing, the magnetic particle filling rate is approximately 70 wt% (binder and magnetic particle (% by weight of the entire coating liquid, including
Small as shown in the table. As can be seen from this example, in magnetic tape for information processing or flexible magnetic disk media for information processing, the surface roughness of the medium is determined as described above.
It is difficult to reduce the thickness to 0.2 μm or less.

In addition, for information processing tapes or flexible magnetic disk media that have such surface roughness and magnetic properties, electromagnetic conversion properties such as output and resolution, or S/N values will meet the requirements of future high-density magnetic recording devices. The value was not fully satisfied.

The purpose of the present invention is to achieve high output and resolution of the reproduced signal, S'/
An object of the present invention is to provide a magnetic recording medium with significantly improved nitrogen content, and a method for producing the same.

In order to solve the problems of the above-mentioned conventional method, the present inventors focused on the surface roughness of the magnetic recording medium and conducted various tests, and found that by controlling the surface roughness of the recording medium. That is, by bringing about a quantitative reduction and qualitative change in the surface roughness, the output and resolution of the reproduced signal are increased, and at the same time, recording medium noise is reduced and the S/N ratio is significantly improved, The present invention has now been completed.

That is, in the magnetic recording medium of the present invention, the 50% amplitude level of the Abbott load curve of the surface roughness of the magnetic layer [50% of the PV (Peak-to-valley) value of the surface roughness]
level] is 0.45 to 0.9, and
It is also characterized by having a surface roughness distribution in which the value of the third moment normalized by the value of the second moment of the surface roughness curve to the 3/2 power is in the range of +0.5 to -1.0.

By imparting the above characteristics to the magnetic layer of a magnetic recording medium, it is possible to obtain a magnetic recording medium of excellent quality, which is the object of the present invention, and completely solve the above-mentioned drawbacks of conventional products. .

The magnetic recording medium of the present invention can be used in magnetic recording media such as magnetic tape devices for information processing, flexible magnetic disk devices for information processing, audio decks, and VTRs.

The surface roughness was measured using a conventional surface roughness measuring instrument, such as a Kurisurf-4 type roughness meter and a Talinoha (both TAYLOI?+10).
(manufactured by BS ON) can be used to measure "ζ".

Surface here! 'JIS-BO6 is the method of expressing the degree of illumination.
0L (1982), and these are broadly classified into height information, pinch (phase) information, and distribution information. The height information ζ is Ra, Rmax, Rz, etc., the pitch information is the average interval of zero crossing points, and the distribution information is the n-th moment I・(n−) of the surface roughness curve y (χ).
2 represents the so-called rms value, n=3 represents the bias of the distribution), or a probability distribution curve, ie, the so-called Abbott load curve.

In the present invention, Ra and Rtm (average value of Rmax), and the third-order moment Rs normalized by the 3/2 power of the rms value
k: (L: measurement length) and the probability (P2O) of reaching the 50% amplitude level of the appointment load curve.

For example, if there is a surface 11th inverted that can be approximated by a Gaussian distribution, the normalized third moment 1- is (), apo.

The probability at the 50% amplitude level of the load curve is expressed as 0.5. Furthermore, the Rsk value corresponds to a positive or negative Rsk value for a surface roughness in which convexity or concaveness is dominant, respectively.

Therefore, from these values, the distribution shape of the original surface 1'11 curve can be determined.

The magnetic recording medium of the present invention has an Rsk value of 0.49 to
The P2O value is within the range of +0.5 to -1.0. If the values of Rsk and P2O are outside the above ranges, the high-density magnetic recording medium targeted by the present invention cannot be obtained.

The magnetic recording medium of the present invention can be manufactured according to the following method.

That is, a flexible plastic film such as ζ polyester, polyimide, or polyvinyl chloride is used as the base,
A magnetic particle coating liquid is applied onto the base film, and a magnetic tape is formed through a normal drying process.

The manufacturing method of this magnetic tape, the components and composition of the magnetic coating liquid, the manufacturing method thereof, etc. can be any known method and are not limited in any way. Magnetic tape is, for example, published by Shokodo, [Tigital Magnetic Recording jp, p.
It can be produced according to the method described in No. 59-166 (published October 25, 1978).

According to the method of the present invention, the thus prepared magnetic tape is then subjected to calendering and lapping processes to produce a magnetic tape having a predetermined surface thickness and surface I'll distribution.

The calendering process is, for example, hard chrome.

The magnetic layer surface may be smoothed by passing the magnetic tape between coated smooth rolls. Further, the wrapping process can utilize the process disclosed in Japanese Patent Publication No. 57-150139, No. 150139, etc. as a means of medium surface smoothing process. However, the published invention does not describe any changes in surface roughness distribution.

The lapping process in the method of the present invention is similar to the method of the invention in the above-mentioned publication, or the method of the present invention specifically reduces the surface roughness of the magnetic recording medium quantitatively and also induces a qualitative change in the surface roughness of the magnetic recording medium. The wrapping process is performed by limiting the wrapping direction, speed, pressing force, etc. to a specific range.

First, as an abrasive tape, for example, one coated with alumina powder with a particle size of O63 μn+ (product name: ■Machi+erialL
apping Film Roles #OG4.5c
(manufactured by otcl+) can be used.

In the lapping process, the calendered magnetic tape is placed on a flat plate, and the wrapping process is performed by pressing the lapping tape against the lamped surface of the magnetic tape each time. The relative speed between the 7-bing tape and the magnetic tape is in the range of 0.1 to 1.0 m/sec, and the pressing force is 2 to 200 g/crA, preferably 4 to 5 m/sec.
It is important to keep it in the range of 0 g/cn+.

If the relative speed and pressing force of the wrapping chive are outside the above ranges, it is impossible to obtain a magnetic recording medium with excellent properties and a long life, which is the object of the present invention and which contains the specified material. Can not.

Although it is possible to perform the wrapping process while rotating the magnetic tape, the wrapping tape, or both, it is generally difficult to rotate the magnetic tape in practice, so it is desirable to rotate the wrapping tape.

Furthermore, if the pusher number ζJ is too large, in addition to the above-mentioned problem, other inconveniences such as abrasion of the surface to be lamped will occur.

Furthermore, it is desirable that the pushing force be distributed within the above range so that it is higher at the center.

This is to increase the wrapping efficiency 6 in the center and at the same time to release generated dust to the outside.

It should be noted that in the method of the present invention, it will be clear to those skilled in the art that the calendering process can be omitted, and that similar effects can be achieved in this case as well, for the reasons described below. In other words, the primary purpose of calendering is usually to improve magnetic properties, and calendering can hardly be expected to bring about any qualitative changes in surface roughness, so it can significantly improve surface roughness and electromagnetic characteristics. I can't hope for that. Regarding this point,
In light of the purpose of the present invention, it is considered that the improvement of the surface brightness by the 2-pink treatment is the dominant factor in improving the electromagnetic conversion characteristics, and the omission of the calender treatment can be achieved by, for example, increasing the lapping pressure. One shield can be replaced.

EXAMPLE 1 Hereinafter, the present invention will be explained in more detail according to examples described together with comparative examples. The ingredients, proportions, order of operations, etc. mentioned below are merely illustrative and do not limit the present invention in any way.

Comparison Example 1 Magnetic particles (Co-rFe2O3) 100 (parts by weight)
Polyurethane resin (molecular weight 50,000-200,000)
32 (=) Diisocyanate-1-5 (〃) Fatty acid ester or aliphatic hydrocarbon i 5C~) Carbon blank 5 (〃) Lecithin 1 (/))'' Each component was mixed with toluene or tetrahydrofuran, etc. in the composition shown in 2. After thoroughly mixing and dispersing the mixture with an organic solvent in a ball mill, the mixture was coated on a polyester film substrate having a thickness of about 35 μm to produce a magnetic tape. This was subjected to a normal drying process without calendering or lapping to obtain a magnetic tape.

A magnetic tape obtained in the same manner as in Comparative Example 1 was subjected to one round of calendering to obtain magnetic tape B. Here, the surface roughness of the roll used for calendering is JIS-B
It is equivalent to 0.1 s according to the O601 (1982) standard.

A magnetic tape obtained in the same manner as in Comparative Example 1 was placed in a calender roll as shown in Comparative Example 2 and calendered 3 to 4 times to obtain a magnetic tape C.

The magnetic tape obtained by the same method as Comparative Example 1 was calendered 3 to 4 times using the calender roll shown in Comparative Example 2 (i.e., magnetic tape production mf & of Comparative Example 2), and then wrapped. A magnetic tape D was obtained.

In the wrapping process in this example, sheet 1-, which was produced by punching a sheet 1 into a disk of approximately 30 cm in diameter from the wide magnetic tape material produced as described above, is placed on a flat plate. - Apply Lasoleng tape (Product name: Imperial Lapping Film R) to the lamp surface.
While rotating (relative speed 0.2m/5ec) the center part 10g/cn
The outer periphery was pressed with a pushing force of 4 g/c.

The surface roughness, electromagnetic conversion characteristics, and S/N of the various magnetic tapes prepared above were investigated and shown in Table 2.

In addition, these magnetic media were cut into sheets with a diameter of approximately 30 cm, and Takeda et al.'s 1-Spherical cant-shaped head for high-density magnetic recording, 1981 IEICE Comprehensive National Conference Lectures (Volume 1), 517- Signals were recorded and reproduced using a monolithic magnetic head as detailed in No. 5,272-273, and the output of the reproduced signal (2F), 2F/IF resolution, and S/N were measured. Signal < S) is Op (zero-
The noise (N) is defined as the rms value of the medium noise component from direct current (DC) to 20 MHz (noise wave length component of 1.5 pm or more) and expressed in dB.
As shown in FIG. 1, which will be described later, the media noise power spec I.
Since it has almost no component at a wavelength of 1.5 μm or less, it is sufficient to consider the band from DC to 20 MH2. In addition, the rms value of the medium noise is obtained by calculating the noise power from the power spectrum of the immediately observed (equipment noise → -medium 11C sound) using the usual method, and subtracting the power of the equipment noise obtained in the same way from this. .

The trunk width of the recording head is 80 μm, the forward track width is 50 μm, and the relative speed of the medium and head is approximately 30 μm.
m/sec, the spacing between the medium and the head is approximately 0.
It is 2 μm. Moreover, the linear density was set to 800 hiso l-/unit.

Table 2 From Table 2, the following can be seen regarding the value and distribution of the medium surface roughness.

(a) For magnetic tape A (comparative example 1) after coating, the average value of Rmaχ of the surface roughness: Rtm and Ra are both large, the normalized third moment (Rsk) is positive, and it is at the 50% level of the Abbott load curve. Probability distribution (P2O) is 0.1 to 0.5
It has an extremely protruding surface shape.

(b) Magnetic tape B (comparative example 2) after calendering has Rtm and Ra of 0.2810, respectively, compared to magnetic tape 8.
35 = 0.8.0.05010.065 = 0.77 times smaller, but Rsk and P2O hardly change, only slightly I) 50 is 0.1 to 0.6, and the range is increasing. be.

In other words, when compared with magnetic tape 8, Table i+i 'I'll
The distribution of protrusions remains almost the same, with fewer protrusions throughout.

(C) Magnetic tape C (comparative example 3) subjected to calendering 3 to 4 times has a higher Ru content than magnetic tape B (comparative example 2).
m and Ra are 0.3010.28 = 1.07 and 0
．． On the contrary, it became larger, 05610.050 = 1.12 times. However, the surface roughness distribution (similar to bl) hardly changes.

(d) In contrast to the above comparative example, in the example according to the present invention, R
tm and Ra are 0.1810.35 = 0.51 C vs. magnetic tape A) and 0.03210.065 = 0.49
(vs. magnetic tape A), R
sk from +1.0 to 0 to +0.5 to -1.0, P2O
changed significantly from 0.1-0.5 to 0.45-0.9. That is, in magnetic tape D, the medium protrusion was shaved off, and the surface was significantly smoothed.

Further, from the electromagnetic conversion characteristics and S/N results shown in Table 2, it was found that the example of the present invention (magnetic tape D) achieved significant improvements in each item of output, resolution, and effective medium noise value. In other words, in improving surface roughness by calendering, S/
Although the amount of improvement in H is only 2 dB at most, in magnetic tape D subjected to wrapping processing, °ζ S/N is +6.5 dB compared to Comparative Example 1 due to quantitative and qualitative changes in surface roughness.
This was significantly improved by +4.8 dB compared to Comparative Example 2 which was subjected to calendar processing.

FIG. 1 shows the noise power spectrum observed at the output end of the regenerative amplifier. In FIG. 1, 1 represents equipment noise (noise observed when the tape is not running), and 2 and 3 represent magnetic tape B (comparative example 2) and magnetic tape D (invention example), respectively. The noise power spectrum is 1iII'r
% Subek I-Ram Analyzer (Y HP-8568A
) was used for observation. As can be seen from the figure, a decrease in the medium noise component is observed over a wide band.

The fact that S/N can be improved by improving surface roughness can be seen in, for example, Iijima, "Influence of Magnetic Tape Noise on Pulse Jitter", Proceedings of the 1980 IEICE Comprehensive National Conference (Volume 1), S. ] As stated in 3-6°285-286, it is thought that a part of the media surface 1 acts as noise, and suppressing the surface roughness is a
This can be explained by saying that this is equivalent to reducing the execution spacing between heads.

As mentioned above, it is clear that the 11WM improvement in S/H was achieved by quantitatively reducing the medium surface roughness and qualitatively changing the medium surface roughness. This means that microprotrusions have been significantly reduced.

On the other hand, 13. R, Becker: “8 Dropo
ut Model for a old digital tape
Recorder”, IEEE, Trans, on
Magn.

MAG-13+no, 5+pp, 1196-1198
(1977), there is a correlation between the S/N and the bit error rate, so it is possible to improve the S/H and at the same time significantly reduce the error rate caused by minute protrusions on the surface of the medium. can be easily concluded.

As explained above, according to the present invention, by controlling the distribution of the surface roughness of the magnetic recording medium, it is possible to reduce the medium surface roughness to 0.03 μm R, which was difficult to achieve with conventional calendaring.
Not only can it be reduced to less than about a or 0.2 pm Rmax, but also the normalized third moment of surface roughness t
l? sk to the negative side from +1.0~O to +0.5~-1.0, and the probability distribution P50 at the 50% amplitude level of the Ahosoto load curve changes from 0.1~0.5 to 0.45~0.9.
There is a qualitative change in the surface roughness distribution, which is a shift towards a larger one (1-), and the effective spacing between the medium and the head, which governs the electromagnetic conversion characteristics, becomes smaller (as the number of minute protrusions on the surface of the medium decreases significantly). . Therefore, it is clear that the higher the density, the less the electromagnetic conversion characteristics and S/H, and the greater the improvement effect. Furthermore, since there is a correlation between the S/N and the Pino 1 error rate, there is an advantage that the Hino I error rate can also be significantly reduced at the same time.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the sharpening tape medium noise power spectrum shown in the present invention example and comparative example 2, and the equipment noise type cass vector when the magnetic tape is not running. Both were observed using the regenerative amplifier output θill. (Main reference number) ■...Equipment noise power spectrum I/Le 2... (Equipment noise) + (Magnetic tape 3 medium 11C
Sound) power spectrum 3... (equipment noise) → - (media noise of magnetic tape D)
Voluntary writing of amendments to the power spectrum procedures) March 12, 1980) FJr Governor's Palace 1, Incident Display In 1988, Application No. 0 (11355)
No. 2, Title of the invention Relationship between the magnetic recording medium and its manufacturing method 3, and the person making the amendment 4'1 112f Applicant's address 1-1-6 Uchisaiwai-cho, Chiyoda-ku, Tokyo Name
(422) Nippon Telegraph and Telephone Public Corporation Representative Tsune Shinto 4, Agent 5, Date of amendment order Voluntary 6, Subject of amendment Detailed explanation of the invention in the specification *
,,Formula 4rL\7, Contents of correction (1) Although it is possible to process ``'' in page 13, lines 11 to 12 of the specification, in practice, the part ``'' should be corrected as follows. "However, in the case of magnetic tape (long material), it is practically possible to treat it."
Diisocyanate,” he said, correcting himself. (3) In the 13th line of page 22 of the same book, the part ``'execution between the medium and the rad'' is changed to ``Reduce the medium noise and correct the effective j and a1 between the medium, the head, and the nod.

Claims (2)

[Claims] (1) 50% of the Abbott load curve for the surface roughness of the magnetic layer
The probability distribution at the amplitude level is 0.45 to 0.9, and the value of the third moment normalized by the value of the second moment of the surface roughness curve to the 3/2 power is +0.5 to 1.0. A magnetic recording medium characterized by having a surface roughness distribution within a range. (2) A magnetic particle coating solution comprising a step of applying a magnetic particle coating liquid onto a flexible plastic film substrate, drying it to obtain a magnetic recording medium, then calendering the magnetic recording medium if necessary, and further subjecting it to a lapping treatment. In the method for manufacturing a recording medium, the lapping process is performed at a relative speed of 0.1 to 1.0 m/sec between the wrapping chive and the magnetic tape, and at a pressing force of 2 to 200 m/sec.
The method for manufacturing a magnetic recording medium as described above, characterized in that it is carried out under conditions in the range of g/cJ.