JPH09161259A - Magnetic recording medium and magnetic recording method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium having excellent erasing characteristics and O/W characteristics by specifying the squareness ratio of the magnetic recording medium to >=0.8 and the squareness coercive force thereof to >=0.7. SOLUTION: A polyethylene terephthalate(PET) base film having 10μm thickness is coated with a magnetic coating material contg. alloy magnetic powder at 2.5μm thickness by gravure coating and the orientation magnetic field is adjusted in an orienting stage after the application, by which the squareness ratio is adjusted to >=0.8 and the squareness coercive force thereof to >=0.7. The squareness coercive force is expressed by the ratio of the distance 4 from a residual magnetic flux density 3 to a polygon 2 at the point of the coercive force and is a parameter determined as S*=H/Hc which indicates the uniformity of the magnetic characteristics near the coercive force of the medium. All of the particles within the medium are judged to be the same in the coercive force within the medium at the squareness coercive force of 1.0. The squareness coercive force is determined by the drawing of only the straight lines from the chart (BH loop and MH loop) of the magnetic characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating type magnetic recording medium used for recording audio, video or data storage.

[0002]

2. Description of the Related Art In recent years, information equipment including audio and video has been digitized along with the improvement in quality of information. Along with this, a medium suitable for digitization is also required for magnetic recording.

In order to handle digital information, a wider band is required than in analog information, so that a medium excellent in high density characteristics is required. As a method for increasing the density of a coating type magnetic recording medium, attention has recently been paid particularly to thinning of a magnetic layer for recording. For example, as disclosed in JP-A-5-54381 and JP-A-5-73883,
It has become possible to coat submicron magnetic layers, which was not possible with conventional coating media.

Further, miniaturization has been pursued as a digital recording device, and in the case of a device for recording / reproducing using a rotary cylinder, the cylinder diameter is designed to be small, so that the number of heads mounted on the cylinder is as large as possible. Is required to be reduced. Therefore, the recording medium is required to have excellent O / W characteristics in addition to the above high-density recording characteristics. Here, the O / W characteristic means a characteristic of how much remaining data is present when new data is directly recorded on the already recorded data.

Conventionally, this has been dealt with by using a medium having a low coercive force, or by increasing the number of heads and mounting an erasing head on a cylinder. Further, in digital recording, it is desired that the recording current be constant regardless of the data repetition frequency. However, in the conventional magnetic recording medium, the optimum recording current has frequency dependence. Therefore, the recording current is set at the most frequently used frequency in the used band, and in the frequency range higher or lower than that, the recording current is used while being deviated from the optimum recording current.

[0006]

In order to improve the high-density recording characteristics, generally, a method of increasing the coercive force is used. However, when the coercive force is increased, excellent O / W characteristics required for digital recording are obtained. There was a problem that it would be difficult to achieve. Further, when using metal magnetic powder with large magnetic energy to improve high density recording characteristics,
It also leads to an increase in noise. In digital recording, 1
It is convenient to always handle 1 as a high level and 0 as a low level in the circuit regardless of the height of the repetition cycle. However, in the case of magnetic recording, it is known that the reproduction voltage has the maximum value in terms of the relationship between the recording current and the reproduction voltage at a certain frequency (called the input / output characteristic at that frequency), and that maximum reproduction voltage is given. The optimum recording current value depends on the frequency.
That is, in digital recording, it is desirable that the optimum recording current is constant regardless of frequency. However, the conventional magnetic recording system has a problem that the value of the optimum recording current varies depending on the frequency.

In order to solve the above conventional problems, the present invention provides
An object of the present invention is to provide a coating type magnetic recording medium with improved erasing characteristics, O / W characteristics and noise characteristics while improving output characteristics. Another object is to provide a magnetic recording method including a recording / reproducing system whose input / output characteristics are suitable for digital recording.

[0008]

In order to achieve the above-mentioned object, the magnetic recording medium of the present invention is a magnetic recording medium prepared by coating a nonmagnetic support with magnetic powder together with a binder. The squareness ratio of the medium is 0.80 or more.

In the above structure, the rectangular coercive force of the medium is preferably 0.7 or more. Further, in the above configuration, the maximum value of the dc remanence characteristic of the magnetic recording medium and the maximum value of the delta M plot obtained from the ac remanence characteristic is
It is preferably 0.5 or less.

In the above structure, the thickness of the magnetic layer on the non-magnetic support is preferably 0.5 μm or less. Further, in the above structure, a magnetic layer having a thickness of 0.5 μm or less is provided on the non-magnetic support, and the coercive force of the medium is 200
0 oersted or more, a rectangular coercive force of 0.7 or more, a maximum value of Delta M plot obtained from dc remanence characteristics and ac remanence characteristics of 0.5 or less, and the magnetic layer is a medium surface. It is preferable to orient in an oblique direction from the inner direction to the vertical direction.

Next, the magnetic recording method of the present invention has a magnetic layer having a thickness of 0.5 μm or less on a non-magnetic support, the coercive force of the medium is 2000 oersted or more, and the square coercive force is 0.7. The above is the magnetic recording medium having a maximum value of 0.5 or less in the delta M plot obtained from the dc remanence characteristic and the ac remanence characteristic, and 1.5 in the gap portion.
Magnetic recording is performed by combining heads including members having a saturation magnetic flux density of T or less.

In the above, if the squareness ratio of the magnetic recording medium is 0.80 or more, preferably 0.85 or more and the square coercive force is 0.7 or more, the recording density characteristic is improved and the O / W characteristic is improved. Can be improved. Also,
In addition to the above characteristics, the peak of the Delta M plot obtained from the dc remanence characteristics and the ac remanence characteristics is set to 0.5 or less. Furthermore, in order to improve the O / W after environmental preservation, the thickness of the magnetic layer on the non-magnetic support is 0.5 μm.
In addition to the above, the squareness ratio is 0.80 or more, preferably 0.85 or more, and the square coercive force is 0.7 or more.
In the above-mentioned means of the present invention, the thickness of the magnetic layer is 0.5 μm.
To achieve the following, a nonmagnetic layer and 0.5μ on a nonmagnetic support
The structure may have a magnetic layer of m or less, or a single magnetic layer having a thickness of 0.5 μm or less on a non-magnetic support.

Further, in order to obtain a recording / reproducing characteristic suitable for digital recording, the above structure is adopted and the squareness ratio is set to 0.
The coercive force is 20 or more, the square coercive force is 0.7 or more, and the maximum value of the Delta M plot is 0.5 or less.
At least a recording head is a head having a medium of at least 00 Oersted and a material having a maximum saturation magnetic flux density of 1.5 Tesla or less in the gap portion.

Further, the magnetic layer of the medium is oriented obliquely from the plane of the magnetic layer toward the direction perpendicular to the film.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Increasing the squareness ratio increases the reproduction output because the orientation of particles is aligned in one direction and the amount of magnetic flux leaked from the medium in the recorded direction is increased. It becomes effective. The effectiveness of this orientation becomes remarkable when the squareness ratio of the medium exceeds 0.8. Further, increasing the square coercive force S * makes the distribution of particles in the vicinity of the coercive force uniform, reducing the bleeding of the magnetization in the transition region which is the boundary portion of the recorded signal, and Sharpen the boundaries. This helps improve the output when the recording wavelength becomes small, and improves the recording density characteristic.
Further, increasing S * means that the area determined by the recording magnetic field of the head is clearly determined.
When recording is performed with a sufficiently large head magnetic field, the signal rewriting effect is reduced and the O / W characteristic and the erasing characteristic are improved.
The present inventors have found that when the squareness ratio is 0.8 or more and the square coercive force is 0.7 or more, this effect is remarkably exhibited.

However, even if the squareness ratio is 0.8 or more and the square coercive force is 0.7 or more, if the particles inside the medium interact with each other and do not behave as individual particles, O / W
Not only the characteristics are not improved, but the noise characteristics are also deteriorated. The interaction between particles in this medium can be clearly determined by reading the so-called Henkel-Plot and seeing the Delta-Plot, which can be shown more quantitatively. It can be explained that this interparticle interaction means that one particle does not react to an external magnetic field according to its own magnetic characteristics, but to react according to the inversion behavior of particles around it. Therefore,
Despite the lack of homogeneity of the individual particles, they seem to be uniform particles in terms of magnetic characteristics, because the particles perform magnetization reversal at the same time. However, in such a medium, there are many portions where the magnetization reversal behavior of particles does not pass through the head magnetic field in the transition region which is the boundary between signals,
Not only is it ineffective in improving the output and O / W, but also the noise characteristics are deteriorated.

In addition, in the medium structure in which the thickness of the magnetic layer is thinned to 0.5 μm or less, the squareness ratio is 0.8 or more and the square coercive force is 0.
O / W due to reduction of film thickness by adding 7 or more characteristics
In addition to the characteristics being further improved, the magnetic field generated by the particles magnetized by recording makes it difficult to magnetize nearby particles due to the effect of clearly determining the recording area, and the magnetization when stored at high temperature Penetration is reduced. Therefore, the O / W characteristics after weatherproof storage do not deteriorate.

If the coercive force is 2000 oersteds or more and the material of 1.5 T or less is used for the head gap portion, the head cannot perform sufficient recording on the medium.
Therefore, recording demagnetization does not occur, and recording can be performed with the same recording current regardless of whether the recording wavelength is long or short. Also, in a medium in which the orientation direction of magnetic particles is slanted, the magnetic field is determined by the head magnetic field generated by the leading edge, so the re-recording effect due to the trailing edge is reduced, and a good overwrite characteristic is produced. By setting it to 0.7 or more, the overwrite characteristic can be further improved.

[0019]

Next, the present invention will be described specifically with reference to examples.

[0020]

Example 1 First, a method of preparing a sample will be described. Table 1 shows the composition of the magnetic paint used in the experiment.

[0021]

[Table 1]

In Table 1, among these materials, the magnetic powder and the total amount of the resin-based binder and methyl ethyl ketone,
30 parts by weight of a mixed solution of toluene and cyclohexanone (the mixing ratio is 3: 3: 1 by weight) was kneaded with a continuous kneader. Two types of magnetic powder, A and B, were prepared. Table 2 shows various characteristics of the magnetic powder used.

[0023]

[Table 2]

In Table 2, A and B are the same alloy metal magnetic powders, but A is made of goethite as a starting material for preparing the alloy magnetic powders, and is then passed through a fine filter to omit large ones. , The particle size distribution was improved, and then the alloy magnetic powder was used.

Then, the kneaded material, the abrasive, the lubricant, and the remaining mixed solvent were dispersed in a sand mill for 5 hours, and finally the hardener was mixed while stirring with a disper to obtain a final coating material. The magnetic paints made from the magnetic powders A and B were designated as a and b, respectively.

The above magnetic paints a and b are gravure coated,
10 μm thick polyethylene terephthalate (PET)
The base film was applied in a single layer having a thickness of 2.5 μm, the orientation magnetic field was adjusted in the orientation step after application, and four samples were prepared for each of the coating materials a and b in which the squareness ratio was adjusted. Sample No. in order of weak orientation magnetic field. 1, 2,
3 and 4.

Each sample was calendered and 60 ° C.
After the curing treatment for 24 hours, a back coat layer mainly composed of carbon black is formed with a thickness of 0.7 μm on the surface of the non-magnetic support opposite to the magnetic layer, and the width is ¼ inch. I slit.

Samples prepared with paints a and b are referred to as samples TA and TB, respectively, and the above-mentioned numbers, which are given in order of weak orientation magnetic field, are added to the end of the sample name to distinguish them. The magnetic properties of these samples are shown in Table 3.

[0029]

[Table 3]

As is clear from Table 3, the coercive force and the saturation magnetic flux density are almost the same in the samples TA and TB,
The rectangular coercive force of the sample TB is 0.65 at the maximum, while the sample TA shows a high value of 0.73. The rectangular coercive force is represented by the ratio of the coercive force Hc1 and the magnetic field H4 from the residual magnetic flux density 3 to the tangent line 2 at the point of the coercive force 1 shown in FIG. 1, and is a parameter obtained as S * = H / Hc. It shows the uniformity of magnetic properties near the magnetic force. Therefore, it is different from SFD which is well known in the related art. A square coercive force of 1.0 determines that the coercive force of particles in the medium is uniform. The square coercive force is a magnetic characteristic chart (BH
Loops and MH loops) are obtained by drawing only straight lines, and there are few errors and good reproducibility.

Next, the erase characteristics of each sample were examined. These tapes have a cylinder diameter of 20 mm and a rotation speed of 9
The measurement was performed using a deck equipped with a full erase head and a fixed head in a 1/4 inch traveling system in which single heads were mounted one at a position facing each other at 000 rpm and 180 degrees. The running speed of the tape is about 2 cm / sec. The fixed head is an audio head made of permalloy and having a track width of 100 μm and a gap length of 0.7 μm. With this head, the signal of 1 kHz is reduced to 0 by the bias current at which the reproduction outputs of sample TB-1 at 1 kHz and 8 kHz become almost the same.
Record to VU level and set it to gap length 6
An erasing current of 50 mA was applied to a 0 μm full erase head to erase, and the remaining 1 kHz signal was measured. The results are shown in Table 3 with the value of sample TB-1 set to 0 dB. As is clear from Table 3, the erasing property becomes low for the case where the squareness ratio is 0.80 or more and the square coercive force is 0.7 or more.

Furthermore, a head mounted on the cylinder is used to record a sine wave signal having a wavelength of 30 μm with an optimum recording current for a signal having a wavelength of 0.5 μm, and 0.5 is recorded on the sine wave signal.
The signal of μm was overwritten, and the remaining amount of the signal of wavelength 30 μm was measured as the O / W amount.

The relative velocity of the measuring system is about 9.42 m / sec.
The signal of 0.5 μm is 18.8 MHz and the signal of 30 μm is 314 kHz. Similar to the case of the erasing rate, this result is shown in Table 3 with the O / W value of sample TB-1 set to 0 dB. Also in this case, it is understood that the O / W is very good when the squareness ratio is 0.8 or more and the square coercive force is 0.7 or more.

In this embodiment, in order to increase S *, the particle size distribution of the magnetic powder was made uniform by passing it through a filter at the time of preparation, but by performing some treatment in the manufacturing process of the magnetic powder, when the magnetic powder was oriented You may obtain the magnetic powder which shows high S *.

[0035]

Example 2 A sample TC was prepared by using barium ferrite, which is a hexagonal hexagonal ferrite shown in Table 4, instead of the magnetic powder used in the sample TA of Example 1. The magnetic properties of these samples are shown in Table 5.

[0036]

[Table 4]

[0037]

[Table 5]

Similar to Example 1, the orientation magnetic field was adjusted to prepare samples having different squareness ratios. 1, in order of weak orientation magnetic field,
Number them a few. The sample TC-3 has a squareness ratio of 0.83, which is lower than that of the sample TA-4 of Example 1, but has a very high squareness coercive force of 0.90. The maximum of the Delta M plot of these two samples was then examined. First, a specific method of obtaining the Delta M plot will be shown.

As a concrete procedure, the DC remanence (dc
demagnetization remanence) and AC remanence (isot
Hermal remanence) characteristic is obtained, and a Henkel plot is obtained from the two characteristics. Further, a Delta M plot is obtained from the Henkel plot.

FIG. 2 shows the magnetic characteristics in the orientation direction of a general magnetic recording medium. Unlike FIG. 1, the vertical axis represents the magnetization M. Reference numeral 5 in FIG. 2 represents the point of maximum magnetization of the medium. The sample to be measured is once magnetized to this maximum magnetization point and the external magnetic field is reduced to a residual magnetization of 3. Further, an external magnetic field is applied up to a certain magnetic field strength 6 in the opposite direction to the maximum magnetization 5. Then, the magnetic field is set to zero and the residual magnetization amount at this point is 7
Is called DC remanence at this magnetic field strength. When measuring the DC remanence at the next magnetic field strength of 8, the external magnetic field is applied again up to the maximum magnetization of 5, and the same procedure is repeated. The graph in which the relationship between the magnetic field strength and the DC remanence is obtained in this manner is called the DC remanence characteristic and is represented by the curve 9 in FIG.

Next, the sample is put into the demagnetized state shown by 10 in FIG. Specifically, the sample can be brought into this state by applying a magnetic field for reducing the cross domain. From this state,
An external magnetic field is applied up to point 11. The magnetization increases along the initial magnetization curve of 13. After that, the external magnetic field is set to zero. The magnetization of the sample is then in some residual state 12.
This magnetization 12 is called AC remanence at the magnetic field strength 11. In order to obtain the AC remanence of the next magnetic field strength 14, the magnetization state of the sample is set to the demagnetization state again, and the same procedure is repeated. The relationship between the magnetic field strength and the magnetization thus obtained is called the AC remanence characteristic, and is represented by the curve 15 in FIG.

The ordinates of the DC and AC remanence characteristics thus obtained are normalized by the residual magnetization amount, and the DC remanence characteristic is converted to a value of -1 to 1 and the AC remanence is converted to a value of 0 to 1. The values of both remanences at a certain magnetic field strength are plotted with the AC remanence on the horizontal axis and the DC remanence on the vertical axis, which is called a Henkel plot, and is as shown in FIG.

DC = 1-2 * A in this Henkel plot
A straight line 17 that is C is drawn, and the difference between this straight line and the Henkel plot is plotted again with the horizontal axis being the applied magnetic field, which is called a delta M plot and is shown in FIG. Therefore, the Delta M plot takes values between -2 and 2. When 19 in FIG. 4 is plotted by this delta M, it becomes 21 in FIG. 5, and 18 in FIG. 4 becomes 20 in FIG.

The meaning of the Henkel plot represents the degree of interparticle interaction inside the medium. If the plot is on the straight line 17 in FIG. 4, there is no interparticle interaction and if it is above the straight line (for example, 18), positive interaction, and if it is below the straight line (for example, 19), it can be judged that there is a negative interaction. This can be read more prominently in the Delta M plot, and if it is 0, there is no interparticle interaction, and the direction and strength can be judged from the peaks in the positive and negative directions.

This Delta M plot was examined for each sample and its peak value was examined. In addition, the erasing characteristics, O / W characteristics, and noise characteristics of these samples were examined. The erasing characteristics and the O / W characteristics were the same as in Example 1.
The noise characteristics of the cylinder system used in Example 1 is 10M.
A single signal with a frequency of Hz was recorded, and the noise level at a point 1 MHz away from the signal when the reproduced waveform was observed with a spectrum analyzer was compared. The results of the peak value, the erase characteristic, the O / W characteristic, and the noise characteristic by the Delta M plot are shown in Table 6 with the sample TC-3 set to 0 dB.

[0046]

[Table 6]

From the results shown in Table 6, even if the squareness ratio is 0.80 or more and the square coercive force is 0.7 or more, when the peak value of the Delta M plot exceeds 0.5, the erasing characteristic and the noise characteristic are deteriorated. I can see it.

[0048]

Example 3 As a practical sample, a sample having a two-layer structure in which a non-magnetic lower layer was added to a magnetic upper layer was prepared. As the lower layer, red iron oxide having a particle size of 0.06 μm was coated with the composition shown in Table 7.

[0049]

[Table 7]

First, among these materials, a mixed solution of red iron oxide and the total amount of the resinous binder and methyl ethyl ketone, toluene, and cyclohexanone (mixing ratio 3: 3:
1) 30 parts by weight were kneaded with a continuous kneader. Then, this kneaded material and the remaining mixed solvent were dispersed in a sand mill for 2 hours to obtain a final coating material.

This lower layer paint and the paint a of Example 1 were applied to a thickness of 1
The thickness of the upper layer was 0.2, 0.
5, 0.8 μm, and the lower layer was 1.8 μm. At this time, the coating film was sufficiently oriented in the longitudinal direction before being dried. The sample was calendered and cured at 60 ° C. for 24 hours, and then a back coat layer mainly composed of carbon black was formed to a thickness of 0.7 μm on the surface of the non-magnetic support opposite to the magnetic layer. It was provided and slit to a quarter inch width.

This sample was designated as TD-1, -2, -3 and compared with sample TA-4. Table 8 shows the magnetic characteristics of each tape.

[0053]

[Table 8]

These tapes have coercive force, saturation magnetic flux density,
It exhibits almost the same characteristics as the squareness ratio, the square coercive force, and the peak value of the Delta M plot, and only the tape structure is different. The output characteristics, noise characteristics, erasure rate, and O / W characteristics of these tapes at a wavelength of 0.5 μm were examined. Moreover, after recording a signal of 1 kHz at the time of measuring the erasing rate, the erasing property was left for 100 hours in an environment of 60 ° C. and 80%, and then the erasing property was examined. The results are shown in Table 9 assuming that the sample TA-4 is 0 dB.

[0055]

[Table 9]

As is clear from Table 9, by making the thickness of the magnetic layer having the magnetic characteristics of the present invention 0.5 μm or less, not only the electromagnetic conversion characteristics, the noise characteristics and the erasing characteristics are excellent, but also in the environment. The erasing property after leaving for 100 hours can also be lowered. This is because the interaction between particles is small and the coercive force distribution is sharp, so that the penetration of magnetization by heat is small. Furthermore, by thinning the magnetic layer, the area itself that penetrates is small, and therefore the erasing rate after being left in the environment does not deteriorate.

[0057]

Example 4 A magnetic tape shown in Table 10 was used in place of the magnetic powder of Example 3 to prepare a sample tape TF in the same manner. The characteristics of this sample are shown in Table 11.

[0058]

[Table 10]

[0059]

[Table 11]

This sample has a coercive force of 2050 Oersted, and the squareness ratio, the square coercive force, and the peak value of the Delta M plot satisfy the conditions of the present invention. With respect to this tape, an MIG head in which a Fe-Tr-N-based metal having a saturation magnetic flux density of 1.5 T (Tesla) is sandwiched in the gap portion and an MIG in which Fe having a saturation magnetic flux density of 1.7 T is sandwiched The head was used to examine the input / output characteristics at recording wavelengths of 0.5 μm and 30 μm. The thickness of the metal layer in the gap is 3 μm. These results are shown in FIG. In the case of the wavelength of 30 μm, the recording demagnetization did not occur in both the case 22 using the 1.5T head and the case 23 using the 1.7T head. But,
When the wavelength is 0.5 μm, the input / output characteristic 24 with respect to the head having the saturation magnetic flux density of 1.5T does not cause the recording demagnetization, whereas the input / output characteristic with respect to the head having the saturation magnetic flux density of 1.7T. No. 25 has a clear recording demagnetization. From this, as in the configuration of this example, the squareness ratio, the square coercive force, and the Delta M plot satisfy the conditions of the present invention, the coercive force is 2000 eslutted or more, and the saturation magnetic flux density is 1.5 T or less in the medium. It was confirmed that by performing recording / reproducing using a head having the material of (1) in the gap portion, it is possible to realize a tape / head combination capable of constant current recording without the need to change the recording current depending on the frequency.

[0061]

Example 5 A tape obtained by further obliquely orienting the sample TD-1 of Example 4 was used as a sample TG. This was prepared by applying a magnetic field in the direction perpendicular to the film surface from the inside of the medium in a direction of about 30 degrees while the film was not dried after coating the upper magnetic layer until the orientation was achieved. The isolated reproduced waveforms of the sample TG and the sample TF were examined. In the sample TG, the avant-garde portion of the isolated reproduction waveform was broadly distorted, and distortion characteristics very close to those of the vapor deposition tape could be obtained. When the input / output characteristics were examined using the 1.5T head used in Example 4, recording demagnetization did not occur as in the sample TF of Example 4. Furthermore, the output of this sample at a wavelength of 0.5 μm,
Table 12 shows the noise, the erasing characteristics, the O / W characteristics, and the erasing characteristics after being left in an environment of 60 ° C. and 80% for 100 hours.

[0062]

[Table 12]

From this result, it can be seen that the output of short wavelength is further improved by the oblique orientation, and the erasing characteristics and the O / W characteristics are further improved as compared with the sample TF. In the above examples, as the material of the magnetic powder, the non-magnetic support, the binder, and the additives such as carbon and abrasive which can be used in the present invention, those generally known can be used. For example, the materials disclosed in JP-A-5-73883 can be used.

[0064]

As described above, according to the present invention, it is possible to provide a magnetic recording medium having good erasing characteristics and O / W characteristics, high output and low noise. In addition, the thickness of the magnetic layer is 0.5μ.
By setting the thickness to m or less, the erasing property after being left in high temperature and high humidity does not deteriorate. Furthermore, by setting the coercive force to 2000 oersted or more and combining with a head having a saturation magnetic flux density of 1.5 T or less, it is possible to provide a medium suitable for digital recording, which has no frequency dependence on the recording current.

[Brief description of the drawings]

FIG. 1 is a diagram showing a method of measuring a square coercive force.

FIG. 2 is a diagram illustrating DC remanence.

FIG. 3 is a diagram illustrating AC remanence.

FIG. 4 is a diagram illustrating a Henkel plot.

FIG. 5 is a diagram illustrating a Delta M plot.

FIG. 6 is a diagram showing input / output characteristics at wavelengths of 30 μm and 0.5 μm when heads having different characteristics of the sample tape of one embodiment of the present invention are used.

[Explanation of symbols]

1 Point showing coercive force on BH loop 2 Tangent at point of coercive force 3 Point showing residual magnetic flux density on BH loop 4 Magnetic field strength showing distance from residual magnetic flux density to tangent 2 5 Maximum on MH loop Point indicating magnetization 6 Magnetic field for measuring DC remanence 7 DC remanence at applied magnetic field 8 8th measured magnetic field 9 Curve showing DC remanence characteristics 10 Demagnetized state 11 AC magnetic field for measuring remanence 12 AC at applied magnetic field 11 Remanence 13 Initial magnetization curve 14 Next measured magnetic field 15 AC Curve showing the remanence characteristics 17 Straight line where DC = 1-2 * AC on Henkel plot 18 Example of positive interaction 19 Case of negative interaction Example 20 Delta M plot corresponding to 18 21 Delta M plot corresponding to 19 22 Using a 1.5T head at a wavelength of 30 μm Input / output characteristics when using a 1.7T head at a wavelength of 30 μm 23 Input / output characteristics when using a 1.5T head at a wavelength of 0.5 μm 23 Input / output characteristics at a wavelength of 0.5 μm Input / output characteristics when using a 7T head

Claims (6)

[Claims] 1. A magnetic recording medium prepared by coating magnetic powder with a binder on a non-magnetic support, wherein the squareness ratio of the medium is 0.80 or more. Medium. 2. The magnetic recording medium according to claim 1, wherein the square coercive force of the medium is 0.7 or more. 3. A dc demagnetization remanen of a magnetic recording medium.
ce, hereinafter “dc remanence characteristic”) and the maximum value of the Delta M plot obtained from isoma remanence (hereinafter “ac remanence characteristic”),
The magnetic recording medium according to claim 1, which is 0.5 or less. 4. The thickness of the magnetic layer on the non-magnetic support is 0.5.
The magnetic recording medium according to claim 1, which has a thickness of not more than μm. 5. A magnetic layer having a thickness of 0.5 μm or less on a non-magnetic support, the coercive force of the medium is 2000 oersteds or more, and the rectangular coercive force is 0.7 or more, and d
The maximum value of the delta M plot obtained from the c remanence characteristic and the ac remanence characteristic is 0.5 or less, and further, the magnetic layer is oriented in an oblique direction from the in-plane direction of the medium to the vertical direction. Magnetic recording medium. 6. A magnetic layer having a thickness of 0.5 μm or less on a non-magnetic support, the medium has a coercive force of 2000 oersteds or more, and a rectangular coercive force of 0.7 or more, and d
Magnetic recording by combining a c-remanence characteristic and a magnetic recording medium having a maximum Delta M plot of 0.5 or less obtained from the ac remanence characteristic with a head including a member having a saturation magnetic flux density of 1.5 T or less in the gap portion A magnetic recording method comprising: