JPH0261824A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain excellent reproduction output particularly in a short wavelength region by specifying the saturated magnetic flux density of a magnetic layer to a specified Gausses or less in the magnetic recording medium in which signals are recorded by a magnetic field transfer system. CONSTITUTION:The magnetic recording medium is composed of a nonmagnetic supporting substance and the magnetic layer formed thereon comprising hexagonal ferrite magnetic powder and a binder, in which signals are recorded by a magnetic field transfer system. The saturated magnetic flux density of the magnetic layer is specified to <=1,800 Gauss. The hexagonal ferrite magnetic powder consists of fine particles of hexagonal ferrite expressed by general formula MO.n(Fe2O3), the particles of which are hexagonal plate type. In the formula, M represents at least one of Ba, Sr and Ca, and n is 5-6. In this case, at least one of Co, Ti, Ni, Mn, Cu, Zn, In, Ge and Nb can be added so as to control the coercive force by substituting these elements for part of the Fe which constitutes the hexagonal ferrite.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a magnetic recording medium for a slave in which a recording signal recorded on a so-called master magnetic recording medium is also transferred by an illumination transfer method. This invention relates to improving the transfer and reproduction output in the short wavelength region of a slave magnetic recording medium using hexagonal ferrite magnetic powder.

[Summary of the invention]

The present invention provides a magnetic recording medium that uses hexagonal ferrite powder as a magnetic 451 powder and is used as a slave medium in the non-n-field transfer method, by specifying the value of the saturation magnetic flux density of the magnetic layer. The objective is to improve transfer efficiency in the wavelength range and obtain excellent transfer and reproduction output.

[Conventional technology]

Due to the characteristics of the above-mentioned transfer method, the coercive force of the slave magnetic recording medium used when the recording signal recorded on the master magnetic recording medium is transferred by the magnetic field transfer method is the same as the coercive force of the master magnetic recording medium. It is preferable that it is 1/2.5 or less. The reason for this is that the master magnetic recording medium is biased by the bias magnetic field during transfer, and there is a proportional relationship between the coercive force of the slave magnetic recording medium and the bias magnetic field required during transfer.

Conventionally, ferromagnetic metal powder has been used as magnetic powder in master magnetic recording media. The use of so-called metal tape is being considered, but its coercive force is still 2000.
The limit is about the level of construction. Therefore, it is currently necessary to use a magnetic recording medium with a low coercive force of 800 oersted or less as a slave magnetic recording medium.

Therefore, what has been put into practical use as a slave magnetic recording medium is, for example, a magnetic recording medium using Co-coated T-Fe203 as a magnetic powder and having a coercive cuff around 00 mm.

By the way, there are 5 types of devices that have been put into practical use in recent years, such as digital audio tape recorders (hereinafter referred to as DAT),
In 8 mm video tape recorders and the like, high-density recording is performed with a shortest recording wavelength of 1 μm or less. When attempting to transfer such a short wavelength signal, the residual magnetic flux density B'
Co-coated 1-Fe2O, with low coercive force Hc, Cry,
In a longitudinal magnetic recording medium using magnetic powder, the output decreases due to an increase in self-demagnetization loss in the short wavelength region.

There is a possibility that both the C/N ratio will be insufficient and the product cannot be used.

Therefore, as a slave magnetic recording medium used for transferring recording signals of the above-mentioned DAT, 8 mm video tape recorder, etc., even though the coercive force Hc is low, it has a high output even at a recording wavelength of lam or less. The emergence of something with these characteristics is desired.

Under these circumstances, in recent years, plate-shaped hexagonal ferrite whose axis of easy magnetization is perpendicular to the plate surface has also been developed using the magnetic field transfer method, actively utilizing the perpendicular magnetization component of n-type powder. Various attempts have been made to achieve high-density recording on slave recording media for transfer.

[Problem to be solved by the invention]

By the way, while νF" recording/reproducing to a ring records firstborn magnetization using the trailing edge magnetic field of a ring head, magnetic field transfer applies an alternating current bias to a leakage magnetic field generated from the surface of a mother magnetic recording medium that has been longitudinally recorded in advance. These recording systems are completely different in principle because they are superimposed and leave residual magnetization in a perpendicular magnetic recording medium that uses hexagonal ferrite powder as the magnetic powder.

Therefore, in terms of the electromagnetic conversion characteristics of a magnetic recording medium for a slave, the characteristics are thicker (it is not uncommon for them to differ, and there are some It is not yet clear whether a slave magnetic recording medium having such characteristics can obtain good reproduction output in magnetic field transfer.

Therefore, the present invention was proposed in view of the conventional situation, and an object of the present invention is to provide a magnetic recording medium for a slave that can obtain good reproduction output in Le 11 field transfer, and particularly in the short wavelength region. An object of the present invention is to provide a magnetic recording medium that exhibits excellent reproduction output.

[Means to solve the problem]

The inventors of the present invention have conducted intensive studies to find out whether or not the above-mentioned object can be achieved.As a result, the inventors have found that, when the squareness ratio and coercive force are the same, the larger the saturation magnetic flux density Bm, the higher the saturation magnetic flux density Bm. While the recording and reproducing output of the head tended to increase, in the case of a stove recording medium using hexagonal ferrite (magnetic $5), if the saturation magnetic flux density Bm is too large, it will shorten. The inventors discovered the fact unique to magnetic field transfer that the magnetic field transfer output in the wavelength region conversely decreases, leading to the completion of the present invention.

That is, the magnetic recording medium of the present invention is a magnetic recording medium in which a magnetic layer mainly composed of hexagonal ferrite (11-type powder) and a binder is formed on a non-magnetic support, and recorded signals are transferred by a magnetic field transfer method. , the saturation magnetic flux density of the magnetic layer is 1
One special feature is that it is 800 Gauss or less.

Hexagonal ferrite (11-dimensional powder is a hexagonal tabular particle, - Formula % Formula % () [However, in the formula, M represents at least one type of Ba, Sr, Ca, and n is 5 to 6.] These are fine particles of hexagonal ferrite.

In this case, Co, Ti are used to control the coercive force.

At least one of Ni Mn, Cu, Zn, In, Ge, and Nb may be added to replace a part of Fe constituting the hexagonal ferrite with these elements. For example, in a magnetobrambite barium ferrite in which M in formula (1) is Ba, when a part of Fe is replaced by the above element, the composition is expressed by the general formula % formula % () [However, in the formula X is Co, Ti, Ni, Mn, C
It represents at least one of uZn, In, Ge, and Nb, m is O-0.2, and n is 5-6. ).

In addition, methods for producing the above-mentioned hexagonal ferrite magnetism include, for example, the Franks method, glass crystallization method, hydrothermal synthesis method, coprecipitation method, etc., but are of course not limited to these. Any conventionally known method may be used.

The tH diameter of the hexagonal ferrite is 0.03 to 0.
．． Preferably, the thickness is 1 μm. Particle size is 0.03μm
If it is less than this, it becomes difficult for particles to orient in the vertical direction in the coating film, and there is a tendency that short wavelength output cannot be obtained. On the contrary, 0.1
If it exceeds .mu.m, the particles are too large and tend to be unable to produce short wavelength output due to deterioration of surface properties and the like.

The plate ratio of the hexagonal ferrite magnetic powder is preferably 3 to 6. If the plate ratio is less than 3, it is difficult to orient the hexagonal ferrite magnetic powder particles vertically in the coating film, and if it exceeds 6, it is difficult to disperse them uniformly in the coating film, and in any case, transfer at short wavelengths is difficult. Indicates a tendency to lose output.

When using the above-mentioned hexagonal ferrite (FF magnetic powder) as a magnetic powder for recording media, it is kneaded with a resin binder and an organic solvent, prepared into a magnetic paint, and then coated on a non-magnetic support. It is coated to form a magnetic layer.

Here, various commonly used resin binders can be used as the resin binder, such as vinyl chloride vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic Synthetic rubber resins such as acid ester-acrylonitrile copolymer, thermoplastic polyurethane elastomer polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivative, polyester resin, polybutadiene, etc. , phenolic resin, Evogin resin, polyurekun hardening resin, melamine resin, alkyd resin,
silicone resins, acrylic reactive resins, epoxy-polyamide resins, di-cellulose-melamine resins, mixtures of high molecular weight polyester resins and isocyanate prepolymers, mixtures of polyster polyols and polyisonanates, urea-formaldehyde resins, low Examples include molecular weight glycol/high molecular weight diol/triphenylmethane triisocyanate resin and mixtures thereof.

Alternatively, in order to improve the dispersibility of the magnetic powder, a resin binder having a hydrophilic polar group may be used.

Specifically, SOJ, OS (h gate, -COOM
, P(OM')z (in the formula, M represents a hydrogen atom or an alkali metal, and M represents a hydrogen atom, an alkali metal or a hydrocarbon group). A polyurethane resin into which a hydrophilic polar group is introduced. , polyester resin, vinyl chloride-vinyl acetate copolymer, vinylidene chloride copolymer,
Acrylic acid ester copolymers, butadiene copolymers, etc. can be used.

In addition to these resin binders, the magnetic layer contains a lubricant.

Plasticizers, molecular IT agents, abrasives, antistatic agents, etc. may be added internally or top coated.

Conventional organic solvents can be used to prepare magnetic paints, such as ketone solvents such as acetone, methyl ethyl ketone, and cyclohexanone, methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and glycol monoethyl acetate. ester type) carrier, glycol ether type solvents such as glycol dimethyl ether, glycol monoethyl ether, and dioxane, aromatic hydrocarbon type solvents such as Hensen 5 toluene and xylene, methylene chloride, ethylene chloride, carbon tetrachloride. General-purpose solvents such as chlorinated hydrocarbon solvents such as chloroform, ethylene chlorohydrin, and dichlorohenzene can be used.

On the other hand, the materials for the non-magnetic support to which the magnetic paint is applied include polyesters such as polyethylene terecrate,
Polyolefins such as polyethylene and polypropylene,
Cellulose triacetate.

Cellulose derivatives such as cellulose diacetate and cellulose acetate butyrate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, plastics such as polycarbonate, polyimide, and polyamideimide, light metals such as aluminum alloys and titanium alloys, and alumina glass, etc. Ceramic 7x etc. are used. The forms of this non-magnetic support include tape, film, sheet, and disk.
It may be a card, a drum, etc.

The vertical squareness ratio of the created magnetic recording medium was 0.65.
~0. ．． Preferably, it is 85. If the vertical squareness ratio is less than 0.65, the transfer output in the short wavelength region tends to be low. In addition, if the vertical squareness ratio exceeds 0.85, for example, when transferring a digital signal with a rotating head type DAT, the phase characteristics will differ greatly from the waveform recorded and reproduced by the head on a longitudinal medium such as a metal tape. ,
Problems arise, such as not being able to extract data using the same equalizer circuit, and the error rate worsening, making it unusable.

Further, the perpendicular coercive force of the medium is preferably 600 to 800 oersteds. If the vertical coercive force is less than 600 degrees, the transfer output tends to deteriorate due to self-demagnetization. On the other hand, if it exceeds 800 oersteds, a large bias magnetic field is required to perform magnetic field transfer, which increases the demagnetization of the master magnetic recording medium due to the bias magnetic field, lowers the transfer efficiency, and reduces the transfer output during repeated transfers. will decrease.

In the magnetic recording medium of the present invention, it is further necessary that the medium has a saturation magnetic flux density Bm of 1800 Gauss or less, preferably 1400 to 1800 Gauss.

When the saturation magnetic flux density Bm exceeds 1800 Gauss, the transfer output in the short wavelength region deteriorates. The details of this cause are unknown, but in slave CD recording media using hexagonal ferrite, the perpendicular magnetization mode is used in a vi-polar manner when recording and reproducing signals at short wavelengths. It is presumed that this is because the perpendicular demagnetizing field of the magnetic layer acts in a direction to reduce the transfer output. In any case, in the head recording/reproducing output of conventional longitudinal magnetic recording media, as the value of the saturation magnetic flux density Bm increases, the BH product of the hysteresis loop in the direction of the axis of easy magnetization increases, and the reproduction output tends to improve. However, the playback output of magnetic recording media for slaves in which signals are recorded by magnetic field transfer tends to decrease even when the squareness ratio and coercive force are the same, This means that magnetic recording media are required to have different characteristics from those of magnetic recording media that have been considered for conventional heads for recording/reproducing. However, if the value of the saturation magnetic flux density Bm is less than 1400 Gauss, the absolute amount of magnetic flux is small, so the transfer output also decreases, which is not practical.

A magnetic signal is transferred from a master magnetic recording medium to the magnetic recording medium according to the present invention by a magnetization transfer method.

As the transfer device used for transferring the magnetic signal, any type of transfer device, such as one using a roller pressure bonding method or an air pressure bonding method, can be used.

The master magnetic recording medium to be used is a so-called metal magnetic recording medium in which magnetic powder is a ferromagnetic metal powder or alloy powder with a holding force (n force 1 (c) of 1,800 degrees or more), or a ferromagnetic metal thin film is coated under vacuum. It is directly deposited on a nonmagnetic support by a method such as vapor deposition.It is preferable to use a so-called metal thin film type magnetic recording medium.

In particular, in terms of transfer efficiency, 5 frequency characteristics, 2 phase characteristics, and 21 && 53 of the master magnetic recording medium, the coercive force Hc is 2.
000 millsted, residual magnetic flux density Br is 2700
Metal magnetic recording media with Gauss or higher are preferred.

[Example] The present invention will be explained below using specific examples.

Toluene cyclohexane 5 parts 1 part 50 parts by weight Actual image LfLL After kneading a composition having the following composition for 20 hours in a ball mill, 3 parts by weight of a curing agent (manufactured by Nippon Polyurethane Co., Ltd., trade name Coronate) was added, and the average pore size was A magnetic paint was obtained by filtration through a 1 μm filter.

Magnetic coating composition Hexagonal ferrite magnetic powder 100 parts by weight Polyurethane resin Vinyl chloride-vinyl acetate copolymer resin Abrasive agent (CrzO*) Dispersant (lecithin) Methyl ethyl ketone 15 parts by weight 15 parts by weight 5 parts by weight 110 parts by weight In the above composition, the average particle size and platelet ratio of the hexagonal ferrite l-1 powder are values actually measured by electron microscopy.

Next, this magnetic paint was applied onto a 9 μm thick polyester film, vertically aligned using a 5 kOe perpendicular magnetic field, dried, and the surface of the magnetic layer was processed using a super calender that can produce an extremely smooth surface. ,
A roll with a magnetic layer thickness of 3.0 μm was obtained. Then, this was cut into a width of 3.8M to prepare a sample tape.

The vertical coercive force Hc of the obtained sample tape was 680
The vertical squareness ratio was 76%.

Actual picture Itsuλ Hexagonal ferrite if magnetic powder average particle size is 0.053
A sample tape was prepared in the same manner as in Example 1, except that the thickness was 3.8 μm, the plate ratio was 3.8, and the saturation magnetization was 55 emu/g.

The vertical coercive force Hc of the sample tape obtained was 710.
The vertical squareness ratio was 76%.

” The average particle size of the hexagonal ferrite magnetic powder per film is 0.055 μm.
, the plate ratio is 3.4, the saturation magnetization is 56 emu/g,
Otherwise, a sample tape was prepared in accordance with the previous Example I.

The vertical coercive force Hc of the sample tape obtained was 710.
The vertical squareness ratio was 76%.

The average particle size of the hexagonal ferrite magnetic powder is 0.050 μm.
, fff-like ratio was 5.0, saturation cn conversion was 62 emu/g, and a sample tape was prepared in the same manner as in Example 1 above.

The vertical coercive force Hc of the sample tape obtained was 660.
The vertical squareness ratio was 76%.

The average particle size of this 1 stone λ hexagonal crystal I powder is 0.051 μm.
A sample tape was prepared in the same manner as in Example 1 except that the plate ratio was 3.2 and the saturation magnetization was 62 emu/g.

The vertical coercive force Hc of the sample tape obtained was 660.
The vertical squareness ratio was 76%.

Here ■ The average particle size of the hexagonal ferrite magnetic powder is 0.051 μm.
, the plate ratio is 3.5, the saturation magnetization is 63 emu/g,
A sample tape was prepared in the same manner as in Example 1 except for the above.

The vertical coercive force Hc of the obtained sample tape was 680
The vertical squareness ratio was 76%.

For each sample tape obtained, the saturation magnetic flux density Bm
, surface roughness, and transfer output level were measured.

The saturation magnetic flux density Bm was measured using a vibrating sample magnetometer (manufactured by Toei Kogyo Co., Ltd., P-1s type VSM) under an external magnetic field of 15 kO.
Measured at e.

Surface roughness was measured using a two-dimensional surface roughness meter (manufactured by Kosaka Laboratory,
ET-10 model).

The transcription output level was measured by the following method.

That is, a mirror pattern was previously recorded on the mother tape with a head, and after air pressure bonding with the sample tape, a bias magnetic field was applied so as to maximize the transfer output, and transfer was performed. The magnetic field transfer conditions and mother tape recording conditions are as follows.

Magnetic field transfer conditions Mother tape Metal tape with in-plane coercive force 2000 (Oe) Transfer speed 1.0 m/sec method Air compression method Mother tape Recording conditions Relative speed Frequency Head gap Trunk width Recording current 3, 133 m / 5ee 4.7 MHz 0 .25 μm 20 μm For each tape, the maximum i1M current was used at 4.7 MHz.Then, the carrier output was measured using a spectrum analyzer. The settings of the spectrum analyzer are as follows.

Spectrum analyzer setting values R, B, W = LOkHz V, 8. W = 100 Hz When measuring the transfer output level, the reference (OdB
), and the output of each sample tape is 1. of the metal tape.
A 5x track pinch correction was performed.

The results are shown in the table below.

Table [Effects of the Invention] As is clear from the above explanation, in a slave magnetic recording medium in which signals are recorded by the magnetic field transfer method, playback can be improved by specifying the saturation magnetic flux density of the magnetic layer. The transfer output can be improved, especially in the short wavelength region, and its industrial value can be said to be very large.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram showing the dependence of transfer output on saturation magnetic flux density. Based on this result, the relationship between the saturation magnetic flux density Bm and the transfer output is plotted in FIG. 1. From this figure 1, the transfer output is the saturation magnetic flux density Bm of the medium.
The great thing about this is that it surpasses metal tape when the pressure is 1800 Gauss or higher.

Claims (1)

[Scope of Claims] A magnetic recording medium in which a magnetic layer mainly composed of hexagonal ferrite magnetic powder and a binder is formed on a non-magnetic support, and a recording signal is transferred by a magnetic field transfer method, wherein saturation of the magnetic layer is provided. A magnetic recording medium having a magnetic flux density of 1800 Gauss or less.