JPH06290442A - Magnetic tape - Google Patents

Abstract

PURPOSE:To provide a magnetic tape capable of using for the tape, etc., for receding digital data. CONSTITUTION:In the magnetic tape where a direction of easy magnetization is in the longitudinal direction of the tape, the squareness ratio of the direction of easy magnetization is 0.5 or above and 0.8 or below. Further, this tape is constituted of a magnetic layer where the ratio between remanence coersive force in the direction of orienting the tape and the remanence coersive force in the direction orthogonally intersecting with the direction of orienting the tape satisfies 1<Hr(TD)/Hr(MD)<1.5 and 0.8<Hr(PD)/Hr(MD)<1.2 in the sectional direction of the tape surface and in the sectional direction of the tape thickness respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-performance magnetic tape capable of achieving a high recording density in the recording wavelength submicron region, and particularly for data storage corresponding to digital recording and digital VTR. It concerns magnetic tape.

[0002]

2. Description of the Related Art Generally, attempts have been made to improve the characteristics of magnetic tapes by increasing the coercive force, making the magnetic powder particles ultrafine, increasing the packing ratio, and making the surface of the magnetic tape smooth. Has been implemented. For example, in the case of iron oxide tape, SVHS tape that has achieved low noise and high density packing has appeared, and metal tape having high magnetic energy has been put to practical use for 8 mm VTR. Further, in the industry, a VTR tape or an audio tape having a multi-layered magnetic layer, which has a high output over a low frequency range to a middle and high frequency range and is rich in luminance signal, color signal, and audio signal characteristics, has been developed and already put on the market. Has been done. In addition, current magnetic recording is generally a method of using in-plane magnetization of a recording medium. Therefore, if an attempt is made to increase the recording density, the demagnetizing field in the recording medium increases, and a high recording density above a certain level is obtained. Things are difficult. In order to exceed such a recording density limit, a perpendicular magnetic recording system has recently been proposed which uses magnetization in a direction perpendicular to the surface of the recording medium. This perpendicular magnetic recording system has a characteristic that the demagnetizing field in the recording medium is reduced at high recording density, and can be said to be essentially a recording system suitable for high-density recording. Recording media used in the perpendicular magnetic recording system include continuous films such as Co—Cr vapor deposition films and coating films in which hexagonal plate-shaped barium ferrite fine particles are dispersed in a resin. However, in the case of a perpendicular recording medium, although the improvement in the short wavelength reproduction output due to the perpendicular magnetization component, which is a characteristic of the perpendicular recording medium, can be expected, the distortion of the reproduced waveform caused by it causes peak shift and jitter, which is fatal in the world of digital VTR. It becomes a problem. Recently, coating film type perpendicular magnetic recording media and obliquely oriented tapes have been attracting attention from the viewpoint of coating type cost merit and practicality such as durability. In the latter case, they have already been marketed as high band 8mm VTR tapes. There is. Also, barium ferrite magnetic powder is
Since it has a plate-like shape and has an easy axis of magnetization in the direction perpendicular to the plate surface, it has been spotlighted as a material suitable for the perpendicular magnetic recording method capable of achieving high recording density as described above. On the other hand, barium ferrite magnetic powder is ultrafine particles that cut below 0.1 μm, and its plate thickness is 1/3 to 1/1 of the particle diameter.
Since it is 10, there is a possibility that a sufficiently high recording density can be achieved even with a longitudinally oriented medium similar to the conventional one, and its trend is drawing attention. Furthermore, as a recent trend, for magnetic tapes for digital data recording, improved tapes of conventional chromium oxide tapes, metal tapes for DAT,
Alternatively, there is an active movement to actively adopt a coated metal tape for high band 8 mm VTR.

[0003]

However, in the development of current coating type magnetic recording media, particularly tape-shaped media, barium ferrite magnetic powder having a plate-like shape and having uniaxial anisotropy as disclosed in the prior art. Although the perpendicularly-oriented medium contributes to higher recording density and higher performance, the perpendicular magnetization component of the tape in practice causes the reproduction waveform to become an asymmetric reproduction waveform with a large undershoot. There was a flaw. In addition, the output in the long wavelength region is undeniably small compared to existing longitudinal recording media, and the improvement in the degree of orientation that has been made to increase the magnetization component in the longitudinal direction is barium, which is a plate-shaped magnetic powder. The ferrite magnetic powder has a drawback that it causes a drastic increase in cohesiveness between the two and causes the characteristics of the ultrafine particles originally possessed by the barium ferrite magnetic powder to disappear, causing an increase in noise. Therefore, there is no almighty magnetic tape which satisfies compatibility while improving the tape characteristics of the conventional longitudinal recording medium, and coating using hexagonal ferrite magnetic powder such as barium ferrite magnetic powder. In the case of type media, magnetic recording of high output from long wavelength to short wavelength is achieved by simply producing perpendicularly oriented media in order to achieve higher performance magnetic recording media while satisfying compatibility with conventional AV equipment. The medium could not be realized.

[0004]

The magnetic tape of the present invention comprises:
In order to solve the above problems, in a magnetic tape comprising hexagonal ferrite magnetic powder particles dispersed and coated on one surface of the non-magnetic base film and a resin binder, and the easy magnetization direction is the tape longitudinal direction, the easy magnetization Direction squareness ratio is 0.5 or more and 0.8 or less, and the ratio of the remanence coercive force in the tape orientation direction and the remanence coercive force in the tape orientation direction and the direction orthogonal to the tape orientation direction is the tape longitudinal direction and the tape thickness. A magnetic tape configured to satisfy 1 <Hr (TD) / Hr (MD) <1.5 (1) and 0.8 <Hr (PD) / Hr (MD) <1.2 (2) in each direction. is there. Further, the hexagonal ferrite magnetic powder particles of the present invention are more preferably a barium ferrite substitution product, but there is no problem as long as they belong to the magnetoplumbite structure. More preferably, part of the iron element is a combination of cobalt, zinc and niobium metal elements.

[0005]

The present invention has been found as a result of an examination from the viewpoint of magnetic properties peculiar to the magnetoplumbite-type hexagonal ferrite magnetic powder, particularly from the viewpoint of micromagnetics. As a result, it is possible to obtain recording density characteristics that surpass conventional longitudinal recording media, and it is possible to increase the recording density of existing tapes from the past, and to plan tapes that match new digital recording. can do. Further, according to the present invention, it is possible to improve the occurrence of the increase in medium noise, which has been conventionally observed in the orientation medium using barium ferrite magnetic powder, without causing any problem in digital recording and reproduction. This means that the magnetic characteristics of the magnetic tape of the present invention are 3
Dimensionally optimized, that is, the ratio of the remanence coercive force of the tape is defined in the longitudinal direction and the thickness direction of the tape in the tape orientation direction and the direction orthogonal to the tape orientation direction. A high output value is obtained as a result of the effect that the magnetization reversal peculiar to particles becomes steep in the reversal region and the effective remanent magnetization component in the direction orthogonal to the tape orientation direction increases. Here, the remanence coercive force indicates the strength of the magnetic field when the magnetization of the magnetic powder particles is irreversibly reversed. Although the value of the remanence coercive force in the tape orientation direction is limited to the range in which recording and reproduction are possible, the rapid progress of magnetic heads in recent years has made it possible to record and reproduce even with high coercive force without sufficient head saturation. The squareness ratio in the easy magnetization direction of the tape is 0.
When it is less than 5, the effective remanent magnetization component becomes small, and 0.
If it is 8 or more, the degree of magnetic agglomeration becomes severe and noise increases more than the output increases, so this range is desirable.
In the magnetic tape of the present invention, the coercive force is not limited in any way, and any recording / reproducing can be performed based on the principle of magnetic recording. The remanence coercive force is preferably 75.5 KA / m or more and 160 KA / m or less. On the other hand, when the saturation magnetic flux density of the tape is small, the required reproduction output cannot be obtained, and in the case of the present invention, the squareness ratio in each direction does not have to be so high. A high packing density of magnetic powder particles is required, and it is necessary to secure at least 170 mT or more. Further, in the constitution of the present invention, since the orientation directions of the particles are three-dimensionally isotropic, the increase of the noise component due to the strong interaction between the particles of the plate-shaped magnetic powders should be reduced. Is possible. As described above, in the present invention, by utilizing the characteristics of the hexagonal ferrite magnetic powder particles and controlling the physical properties of the coating type magnetic tape, the mass productivity, the running property, and the stability obtained by the conventional coating type are stable. It is possible to supply a magnetic tape capable of further increasing the recording density and the performance of the existing tape, while ensuring the performance.

[0006]

EXAMPLE An example of the magnetic tape of the present invention will be described below.

Thickness of 10 μm as non-magnetic base film
The magnetic coating shown below was applied to one surface of the polyethylene terephthalate film of 1. by a nozzle type coater, magnetic field orientation treatment was applied in an undried state, and dried in an atmosphere of 80 ° C. for 2 minutes (Example 1). Magnetic tape was manufactured. First, the following materials were used as a coating material for the magnetic coating material applied to the base film to form a coating material. Barium ferrite --- 100 parts by weight Vinyl chloride resin ------- 6 parts by weight Polyurethane resin --- 5 parts by weight Alpha-alumina ----- 2 parts by weight Stearic acid- ------------- 3 parts by weight Butyl stearate -------- 1 part by weight Carbon black -------- 1 part by weight MIBK ----------- 81 parts by weight Toluene- ---------- 81 parts by weight Cyclohexanone ----------- 50 parts by weight After mixing the above materials, they were dispersed for a certain period of time with a kneader, a mixer and a sand mill. The barium ferrite magnetic powder particles used had a particle size of 0.045 μm and a plate ratio of 3.
5, a coercive force of 80 KA / m and a coercive force controlled by a substitution element (a combination of Co--Zn--Nb) was used. Apply the mixed, dispersed and diluted magnetic paint at a coating speed of about 100 m / min using a die-type nozzle coater. First, face the tape running direction in two directions, the thickness direction and the width direction. The magnetic powder particles were oriented isotropically in the longitudinal direction of the tape by passing through the installed permanent magnets facing the same pole and then passing between the solenoid magnet aligning devices facing the same pole. After that, the obtained coating film was dried and cured, and then a 0.7 μm back coat layer was provided on the side opposite to the magnetic layer coated surface to prepare a magnetic tape of (Example 1).
In Example 1, the magnetic layer had a thickness of 2.0 μm. Here, the film thickness is not regulated at all and may be changed according to the recording length, but it is practically 2 to 3 μm.
A degree is preferable. On the other hand, a plurality of magnetic layers may be present, and it is desirable to set the coercive forces of the upper and lower magnetic layers in a well-balanced manner. In this embodiment, Hc of both upper and lower layers is not distributed for the purpose of improving recording sensitivity. In this way, when the easy axis of magnetization of the upper layer is set in the film thickness direction, sufficient recording can be performed even at low Hc, and therefore it may be controlled by the film thickness of the upper layer and the coercive force configuration of both magnetic layers.

(Example 2) In Example 1, the hexagonal ferrite magnetic powder particles used for coating the magnetic layer were prepared by adding excessive spinel layer to barium ferrite with Hc of 95 KA / m. A magnetic tape was produced in the same paint format except that the plate ratio was 3.1. At that time, the thicknesses of the magnetic layer and the back coat layer were 2.5 μm and 0.6 μm, respectively, to obtain the magnetic tape of (Example 2).

(Comparative Example 1) A barium ferrite-substituted plate-like magnetic powder having a plate ratio of 5 and an excessive spinel layer added to the magnetic layer was used in the same manner as in (Example 1) except that it was made into a paint ( According to Example 1), a magnetic coating was prepared by mixing and dispersing with a kneader and a grind mill, and then a predetermined amount of a lubricant and a curing agent were added with stirring, and then the magnetic coating was formed on the base film. Was applied at a coating speed of about 100 m / min using a die-type nozzle coater to obtain 2.5 μm
After coating, a magnetic coating film was prepared without magnetic field orientation immediately after coating, and after sufficient drying and curing, a 0.7 μm back coat layer was applied in the same manner as in Example 1 (Comparative Example 1). A film was obtained.

(Comparative Example 2) The magnetic layer has a coercive force of 65 KA /
m, using barium ferrite magnetic powder particles with a plate ratio of 6,
A magnetic tape was produced in the same manner as in (Example 1) according to the same format as in (Example 1) except that the total amount of resin was 18 parts by weight, and a magnetic layer of 2.5 μm was applied and immediately applied. Immediately after passing the magnetic field orientation through an opposing solenoid magnet that emits magnetic flux in the same direction as the direction of travel of the coating film, a so-called in-plane longitudinal orientation magnetic coating film is produced, and after drying and curing, 0.8 μm A back coat layer was applied to obtain a coating film of (Comparative Example 2).

(Comparative Example 3) A commercially available MP tape for Hi8VTR (manufactured by Fuji Photo Film Co., Ltd.) was used as (Comparative Example 3).

The obtained coating film was slit into a width of 8 mm, and the electromagnetic conversion characteristics were measured using a modified Hi8VTR deck. The electromagnetic conversion characteristics were evaluated by mounting a superstructure nitride film laminated type head with a gap length of 0.19 μm and a track width of 10 μm on the deck and recording / reproducing at a relative speed of 3.8 m / sec between the tape and the head. The RF output at a recording frequency of 10 MHz is representative. C / N is 10MHz ±
It was measured and evaluated at RBW 30 KHz at 0.1 MHz. The squareness ratio and remanence coercive force of the tape were evaluated using a digital vibration sample type magnetometer (Model 1660 manufactured by DMS). The surface property of the tape was measured and evaluated with a root-mean-square roughness using a non-contact optical type three-dimensional surface roughness meter (manufactured by WYKO), but all samples showed the same level value. The above measurement results are
Each is shown in (Table 1), and RF relative output and C / N are shown as relative values with (Comparative Example 3) being 0 dB.

[0013]

[Table 1]

In Table 1, Sq is the squareness ratio in the orientation direction, Hr (TD) / Hr (MD), Hr (PD) / Hr.
(MD) indicates the ratio of the remanence coercive force between the orientation direction and the direction orthogonal thereto. MD is the orientation direction,
TD indicates the tape width direction, and PD indicates the tape thickness direction. From (Embodiment 1) and (Embodiment 2), by making the physical properties of the magnetic tape satisfy the expressions (1) and (2) as in the present invention, high reproduction output and low noise can be achieved. I see that it will be achieved. As a result, as shown in (Table 1), the effect of the tape structure disclosed in the present invention is clear. On the other hand, in the case of (Comparative Example 1), the filling rate of the magnetic powder in the magnetic layer was insufficient, and a sufficient reproduction output could not be obtained. In (Comparative Example 2), in the case of the tape using the hexagonal ferrite magnetic powder particles, the reproduction output was comparatively improved, but the noise was much higher than that. That is, it was found that (Comparative Example 1) and (Comparative Example 2) were inferior in either RF output or C / N, and the magnetic tape characteristics were not balanced as a whole. As can be seen from the above results, the example using the present invention can achieve a high level of both output improvement and noise reduction in the short wavelength region as compared with the sample of the comparative example which does not use this. became. In the examples, in the case of having a plurality of magnetic layers, if the uppermost layer satisfies the conditions of the present invention, the layers below it are needle-shaped ferromagnetisms such as iron oxides, metal alloys, and iron nitrides. It may be carried out in combination with a powder or a plate-like ferromagnetic powder such as barium ferrite, and is not limited to these.

[0015]

As described above, according to the present invention, by optimizing the configurations of the magnetic powder particles and the medium, a balanced reproduction output can be realized at a high level, and the noise can be reduced. A good magnetic tape can be obtained. Therefore, the present invention can provide a magnetic recording medium which is not only compatible with the conventional magnetic tape but also sufficiently compatible with future digital recording and which is suitable for higher density recording. , A very useful invention.

Claims (1)

[Claims] 1. A magnetic tape comprising hexagonal ferrite magnetic powder particles dispersed and coated on one surface of a non-magnetic base film and a resin binder, wherein the easy magnetization direction is the longitudinal direction of the tape. The squareness ratio is 0.5 or more and 0.8 or less, and the ratios of the remanence coercive force in the tape orientation direction and the remanence coercive force in the tape orientation direction and the direction orthogonal to the tape orientation direction are respectively in the tape longitudinal direction and the tape thickness direction. In the following, the following equations 1 <Hr (TD) / Hr (MD) <1.5 (1) and 0.8 <Hr (PD) / Hr (MD) <1.2 (2) tape.