JPH01236424A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To enhance the transfer efficiency in a short wavelength region of <=1mum and to assure the interchangeability of the long-sized medium with ring head recording in terms of electromagnetic conversion characteristics by specifying the average grain size and platy ratio of hexagonal ferrite magnetic powder and further specifying the perpendicular coercive force Hc and perpendicular squareness ratio of the magnetic recoding medium. CONSTITUTION:The average grain size of the hexagonal ferrite magnetic powder used in the magnetic recording medium which is formed with the magnetic layer essentially consisting of the hexagonal ferrite magnetic power and a binder on a nonmagnetic base and is transferred with signals by a magnetic field transfer system is specified to <=0.08mum and the perpendicular coercive force Hc as the magnetic recording medium is specified to <=800 oersted and the perpendicular squareness ratio to 0.65-0.8. The platy ratio of the hexagonal ferrite magnetic powder is specified to 3-4 if the signal to be subjected to the magnetic field transfer in particular is an analog signal. The platy ratio of the hexagonal ferrite magnetic powder is specified to 3-5 if said signal is a digital signal. The interchangeability with the long-sized recording medium is thereby obtd. in terms of the electromagnetic conversion characteristics such as transfer output, frequency characteristics, C/N and phase charac teristic.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a magnetic recording medium for a slave in which a recording signal recorded on a magnetic recording medium for a master is transferred by a magnetic field transfer method. It exhibits its characteristics particularly for high-density recording applications.

[Summary of the invention]

The present invention provides a magnetic recording medium that uses hexagonal ferrite powder as a magnetic powder and is used as a slave medium in a magnetic field transfer method. Furthermore, by specifying the perpendicular coercive force Hc and perpendicular squareness ratio of the magnetic recording medium, the transfer efficiency in the short wavelength region of 1 μm or less can be improved, and the ring head recording on conventional so-called longitudinal media can be improved. The aim is to maintain compatibility with electromagnetic conversion characteristics.

[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. The reason for this is that the master magnetic recording medium is demagnetized by the bias magnetic field during transfer.
This is because there is a proportional relationship between the coercive force of the slave magnetic recording medium and the bias magnetic field required for 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 2,000 yen.
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 Oe or less as a slave magnetic recording medium.

Therefore, what has been put into practical use as a magnetic recording medium for a slave is, for example, a magnetic recording medium that has a coercive cuff around 00000000 and uses Co-coated y-Fe3O3 as a magnetic powder.

By the way, in recent years, there are devices that have been put into practical use9, such as digital audio tape recorders (hereinafter referred to as DAT),
For 8m video tape recorders, etc., the shortest recording wavelength is 1. High-density recording below um is being performed. When trying to transfer such a short wavelength signal, the residual magnetic flux density Br
, Co-coated y-Fe with low coercive force Hc, 03. 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, it is used to transfer the recording signals of the above-mentioned DAT, 8-inch video tape recorder, etc.

As a magnetic recording medium for a slave, there is a demand for a magnetic recording medium that has high output characteristics even at a recording wavelength of ltIm or less, despite having a low coercive force Hc.

Under these circumstances, in recent years, plate-shaped hexagonal ferrite 1 whose axis of easy magnetization is perpendicular to the plate surface has been developed by actively utilizing the magnetization component in the perpendicular direction of the magnetic powder and using a magnetic field transfer method. Various attempts have been made to increase the recording density of slave magnetic recording media for transfer.

[Problem to be solved by the invention]

By the way, while ring head recording/reproduction records longitudinal magnetization using the trailing edge magnetic field of the ring head,
In magnetic transfer, an alternating current bias is superimposed on the leakage magnetic field generated from the surface of a mother tape on which longitudinal recording has been previously performed, and residual magnetization remains in the perpendicular magnetic recording medium, so these are completely different recording methods in principle.

Therefore, although the magnetic recording medium using the aforementioned hexagonal ferrite magnetic powder has excellent short wavelength characteristics, it is difficult to use a system using a metal tape, such as DA
If you try to use it as is at T, the phase characteristics will be asymmetrical due to the contribution of the vertical component, unlike that of a longitudinal medium.
If the equalizer does not match, the error rate will worsen, making it difficult to maintain compatibility.

Alternatively, the output of a medium using hexagonal ferrite becomes lower than that of a metal tape as the wavelength of the recording signal becomes longer, and as a result, the frequency characteristics differ from those of a metal tape, etc., so compatibility is still not guaranteed. This may cause the problem to occur. This is because the longitudinal magnetization component becomes dominant in the long wavelength region, and the residual magnetic flux density in the longitudinal direction of the hexagonal ferrite is 10
This is because, while it is less than 00 Gauss, that of metal tape is more than 2000 Gauss. The reason why the residual magnetic flux density in the longitudinal direction of hexagonal ferrite is so small is due to the fact that it is an oxide and has less than half the magnetization, and the basic characteristics of hexagonal ferrite that magnetization tends to be oriented in the perpendicular direction. It is something to do.

The present invention has been proposed in view of such circumstances, and aims to provide a magnetic recording medium that has high transfer efficiency in the short wavelength region and is compatible with longitudinal media recorded and reproduced by ring heads. This is the purpose.

[Means to solve the problem]

The inventors of the present invention have made extensive studies to achieve the above-mentioned objective, and have conducted various magnetic field transfer experiments using magnetic recording media that use hexagonal ferrite as magnetic powder. Despite the differences in electromagnetic conversion characteristics,
We have found that compatibility with longitudinal media can be ensured by specifying the hexagonal ferrite magnetic powder used and the perpendicular magnetic properties.

The present invention was completed based on the above knowledge, and a magnetic layer mainly composed of hexagonal ferrite magnetic powder and a binder is formed on a non-magnetic support, and signals are transferred by a magnetic field transfer method. In the magnetic recording medium, the average particle size of the hexagonal ferrite magnetic powder is 0.08 am or less, the perpendicular coercive force Hc of the magnetic recording medium is 800 Oe or less, and the perpendicular squareness ratio is 0.08 am. 65～
0.8, and especially when the signal to be transferred by the magnetic field is an analog signal, the plate ratio of the hexagonal ferrite magnetic powder is 3 to 4. In the case of digital signals, the plate ratio of the orthogonal ferrite magnetic powder is 3 to 5.

First, regarding the perpendicular magnetic properties of a magnetic recording medium, in recording with a normal magnetic head, if the perpendicular squareness ratio is 0.55 or more, the head recording and reproduction in the short wavelength region is possible due to the relationship with the saturation magnetic flux density. However, in recording by magnetic field transfer, if the vertical squareness ratio is less than 0.65, as shown in Figure 1, the output will not improve much, especially in the short wavelength region (4.7MHz in this figure). ), the transfer output becomes low. Therefore, in consideration of recording by magnetic field transfer, the vertical squareness ratio is preferably set to 0.65 or more.

However, if the vertical squareness ratio exceeds 0.80, the longitudinal squareness ratio will decrease, and as shown in Figure 2, the residual magnetic flux density in the longitudinal direction will decrease and the longitudinal magnetization component will decrease. A disadvantage arises in that the transfer output in the dominant long wavelength region (130 kHz in this figure) becomes low.

In addition, especially in the case of digital recording, if the vertical squareness ratio is too large, not only will the output drop, but the phase characteristics will differ greatly from the waveform recorded and reproduced by a head on metal tape, for example, so even if the same equalizer circuit The 0-phase characteristic, which causes problems such as not being able to extract data and causing problems such as degraded error rate and unusability, is a characteristic unique to digital recording (square wave direct recording), and the shape of the reproduced waveform obtained in the isolated magnetization reversal region. (Half width, symmetry) When obtaining digital data, if the reproduced waveforms are not similar, the error rate will be poor and compatibility will not be achieved.

Note that the above-mentioned vertical squareness ratio indicates a value after demagnetizing field correction.

Next, the perpendicular coercive force of the magnetic recording medium is set to 800 Oe or less. - Generally, in a slave magnetic recording medium, the higher the perpendicular coercive force Hc, the more bias magnetic field is required during transfer, but this bias magnetic field acts as an erase magnetic field for the master magnetic recording medium.

In particular, when the perpendicular coercive force Hc is greater than 800 Oe, demagnetization of the master magnetic recording medium due to the bias magnetic field becomes large, and the transfer efficiency decreases.
The transfer output in repeated transfers will be reduced. Therefore, it is preferable that the perpendicular coercive force Hc of the slave magnetic recording medium is 800 Oe or less.

More preferably, it is 750 oersted or less.

However, if it is less than 600 oers, the short wavelength output becomes low regardless of head recording or magnetic field transfer recording, which is not practical.

Hexagonal ferrite magnetic powder is used as the magnetic powder for the slave magnetic recording medium having the above characteristics. The hexagonal ferrite magnetic powder has the general formula % (1) [wherein M represents at least one of Ba, Sr, and Ca, and n is 5 to 6. ] These are microparticles of macrogonal ferrite. - In this case, Co and 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 % (2) [However, the formula Medium X is Co, Ti, Ni, Mn, and Cu.

Represents at least one of Zn, In, Ge, and Nb,
m is 0-0.2, and n is 5-6. ].

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

The above-mentioned hexagonal ferrite magnetic powder needs to be fine particles with an average particle size of 0.08 μm or less, especially 0.08 μm or less.
．． Fine particles of about 0.05 to 0.06 am are good in terms of dispersibility, saturation magnetic flux density, etc.

The average particle size of the macrogonal ferrite magnetic powder is 0.08μm
When the value exceeds 1, particle noise becomes high and C/N deteriorates.

In addition, the plate ratio of hexagonal ferrite magnetic powder is
As the plate ratio increases, the porosity of the magnetic layer increases, and as a result, the C/N deteriorates as shown in FIG. This is noise generated from inside the magnetic layer due to increased magnetic non-uniformity.

This is thought to be due to an increase in so-called tape noise.

Therefore, the plate ratio may be determined based on the C/N tolerance range, but the tolerance range differs slightly depending on the signal transferred to the magnetic recording medium. For example, in the case of a digital signal, if the plate ratio exceeds 5, Affects error rate. In the case of analog signals, if the plate ratio exceeds 4, a problem arises in that the image quality deteriorates. Therefore, if the signal to be transferred is a digital signal, the plate ratio is 5. In the case of analog signals, the plate ratio of 4 is the upper limit.

On the other hand, regarding the lower limit of the plate-like ratio, if the plate-like ratio is less than 3, it is not possible to stably obtain a vertical squareness ratio of 0.65 or more even if vertical alignment processing is performed. Even in the case of , this plate ratio of 3 would be the lower limit.

When the above-mentioned hexagonal ferrite magnetic powder is used as magnetic powder for magnetic recording media, it is kneaded with a resin binder and an organic solvent to prepare a magnetic coating material, which is then coated on a non-magnetic support to form a magnetic layer. becomes.

Here, as the resin binder, various commonly used resin binders can be used, such as vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer,
Vinyl chloride-acrylonitrile copolymer, acrylic acid ester-acrylonitrile copolymer, thermoplastic polyurethane elastomer, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivative, Polyester resin, synthetic rubber resin such as polybutadiene, phenol resin, epoxy resin, polyurethane curable resin, melamine resin, alkyd resin, silicone resin, acrylic reaction resin, epoxy-polyamide resin, nitrocellulose-melamine resin, high molecular weight polyester Examples include mixtures of resins and isocyanate prepolymers, mixtures of polyester polyols and polyisocyanates, urea formaldehyde resins, mixtures of low molecular weight glycols/high molecular weight diols/triphenylmethane triisocyanate, polyamine resins, 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.

(In the formula, M represents a hydrogen atom or an alkali metal, and Mo
represents a hydrogen atom, an alkali metal or a hydrocarbon group)
Polyurethane resins with hydrophilic polar groups introduced, polyester resins, vinyl chloride-vinyl acetate copolymers, vinylidene chloride copolymers, acrylic ester copolymers, butadiene copolymers, etc. are used. It is possible.

In addition, ordinary organic solvents can be used, such as ketone solvents such as acetone, methyl ethyl ketone, and cyclohexanone, ester solvents such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and glycol acetate monoethyl ether, and glycols. Glycol ether solvents such as dimethyl ether, glycol monoethyl ether, and dioxane; aromatic hydrocarbon solvents such as benzene, toluene, and xylene; methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, dichlorobenzene, etc. General-purpose solvents such as chlorinated hydrocarbon solvents can be used.

In addition to these resin binders, a lubricant or the like may be added internally or top coated to the magnetic layer, and an abrasive or a dispersant may also be added as necessary.

The magnetic coating material kneaded with the hexagonal ferrite magnetic powder, resin binder, etc. is applied onto a non-magnetic support to form a magnetic layer. , polyolefins such as polyethylene and polypropylene, and 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 ceramics such as alumina glass. etc. are used. The nonmagnetic support may be in the form of a tape, film, sheet, disk, card, drum, or the like.

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

In addition, the magnetic powder used in the master magnetic recording medium is a ferromagnetic metal powder or alloy powder having a coercive force Hc of 1800 degrees or more.

A so-called metal magnetic recording medium or a ferromagnetic metal thin film was deposited by a method such as vacuum deposition. Preference is given to using so-called vapor-deposited magnetic recording media.

In particular, in terms of transfer efficiency, one frequency characteristic, nine phase characteristics, demagnetization of the master magnetic recording medium, etc., a metal magnetic recording medium having a coercive force Hc of about 2,000 millimeters and a residual magnetic flux density Br of 2,700 Gauss or more is preferable.

(Function) In order to ensure compatibility between the magnetic recording medium for magnetic field transfer and the longitudinal recording medium, output in the frequency range used.

Frequency characteristics and C/N are important characteristics, and especially when the transferred signal is a digital signal, phase characteristics (symmetry of reproduced waveform) also become a problem.

In the magnetic recording medium of the present invention, the vertical squareness ratio is 0.65.
~0.8, so the transfer output is balanced from the long wavelength region to the short wavelength region, and it exhibits good frequency characteristics, especially since the vertical squareness ratio is kept below 0.8. , deviations from the phase characteristics when recording on a longitudinal medium with a ring head are also suppressed.

Further, by setting the vertical coercive force to 800 Oe or less, the magnetic field acts as an erase magnetic field for the master tape (the bias magnetic field is suppressed, and a decrease in the transfer output of the master tape is suppressed).

On the other hand, the average particle size and plate ratio of the hexagonal ferrite magnetic powder used have a large effect on the C/N, but - the type of signal transferred by magnetic field (digital signal).

By setting these within the range according to the analog signal (analog signal), deterioration of C/N can be suppressed, and the problem of deterioration of error rate and image quality can be solved.

〔Example〕

Hereinafter, specific examples of the present invention will be described, but it goes without saying that the present invention is not limited to these examples.

First, a composition having the following composition was heated in a ball mill for 20 minutes.
After kneading for a period of time, 3 parts by weight of a curing agent (manufactured by Nippon Polyurethane Co., Ltd., trade name: Coronate L) was added, and the mixture was filtered through a filter with an average particle size of 1 μm to obtain a magnetic paint.

Magnetic coating composition Barium ferrite magnetic powder 100 parts by weight Polyurethane resin 15 parts by weight Vinyl chloride-vinyl acetate copolymer resin 15 parts by weight Abrasive (Cr
y Os) 5 parts by weight Dispersant (lecithin) 1 part by weight Methyl ethyl ketone 110 parts by weight Toluene
50 parts by weight cyclohexane
50 parts by weight of this magnetic paint was then applied to a thickness of 9
After coating on a μm polyester film and performing vertical alignment treatment, the surface of the magnetic layer is processed using a super calender that allows for drying and extremely smooth surface treatment.
Magnetic layer thickness 3. Got a roll of Oam. Then, this was cut into a width of 3.81 mm to produce a sample tape.

According to the above-mentioned method, various sample tapes (Examples 1 to 4) were prepared using different barium ferrite magnetic powders.
Comparative Examples 1 to 3) were obtained.

Note that all of the sample tapes other than Comparative Example 2 were subjected to vertical alignment treatment, and the vertical squareness ratio was controlled by adjusting the coating speed.

For each sample tape obtained as above,
Magnetic flux density (Bm) and vertical squareness ratio (Rsz
), the perpendicular coercive force (Hc) was measured, and magnetic field transfer was performed to obtain the transfer output (4.7MHz and 130klk).
), C/N, error rate, and phase characteristics were investigated.

In addition, magnetic field transfer uses coercive force Hc = 2 as a mother tape.
A mirror pattern was recorded in advance on a metal tape of 000 (Oe) using a mother recorder head, and after air pressure bonding with the sample tape, a bias magnetic field was applied to maximize the transfer output, and the transfer was performed at a speed of 1.0 m/sec. Transcription was performed. An air pressure type transfer device was used for the transfer. As shown in Fig. 2, the air pressure bonding type transfer device described above has the following features:
A bias head (1) and a transfer drum (2) are arranged facing each other. In the air crimping method, air is fed from the rear (1b) side of the bias head (1) as shown by arrow A in Figure 2, and this air A is fed into the bias head (1).
Master magnetic recording is recorded on the side surface of the transfer drum (2) by blowing air with a predetermined pressure from the side surface of the head located on the front (la) side of 1) to the side surface of the opposing transfer drum (2). The medium (3) and the slave magnetic recording medium (4) are pressed together. In this way, the master magnetic recording medium (3) and slave magnetic recording medium (4) are separated by the pressure of the air blown out from the bias head (1) side.
) was pressed while applying a bias magnetic field using a bias head (1) to perform transfer. After the transfer was completed, the transfer output levels at frequencies of 4.7 MHz and 130 kHz were measured using a spectrum analyzer. Note that when measuring the transfer output level, the metal tape for R-DAT was used as a reference (OdB), and the output of each sample tape was subjected to track pitch correction 1.5 times that of the metal tape.

C/N is the output level when recording and reproducing the highest frequency f,... (MHz) is C(dB), f,...-1
When the noise level of (M1hi) is N (dB), C/N
−C−N, and in this example, f
, , -4.7MHz.

The results are shown in Table 1. Table 1 also shows the average particle diameter of the barium ferrite magnetic powder used.

The plate ratio is also shown.

(The following is a blank space) As is clear from Table 1, Examples 1 to 4 to which the present invention is applied exhibit good electrical characteristics.

However, as for Example 4, since the C/N is low, it can be used for digital signals, but it is difficult to use for analog signals.

On the other hand, in Comparative Example 1, the vertical squareness ratio Rsz was 84% (0
, 84), it can be understood from the high error rate that the phase characteristics do not match and compatibility cannot be achieved.

Comparative Example 2 corresponds to the non-oriented tape of Example 2, and has a low vertical squareness ratio Rsz and low short wavelength output, so there is a problem in compatibility for high-density recording medium applications.

In Comparative Example 3, the barium ferrite magnetic powder had a particle size of 0.
Since the diameter is as large as 0.09 μm, there is a problem in that the C/N ratio is poor.

〔Effect of the invention〕

As is clear from the above description, in the magnetic recording medium of the present invention, the perpendicular magnetic properties (vertical squareness ratio, perpendicular coercive force) and the average grain size of the hexagonal ferrite magnetic powder used are The diameter is set to a predetermined value, and the plate ratio of the hexagonal ferrite magnetic powder is also selected within a predetermined range depending on whether the signal transferred by the magnetic field is a digital signal or an analog signal. Therefore, it is possible to achieve compatibility with longitudinal recording media in terms of electromagnetic conversion characteristics such as transfer output frequency characteristics, C/N, and phase characteristics.

Therefore, the magnetic recording medium of the present invention can be directly reproduced by a magnetic recording and reproducing apparatus that performs recording and reproducing with a ring head, although the recording principle is greatly different.
It is extremely useful for manufacturing so-called soft tapes at high speed and in large quantities using magnetic transfer technology.

[Brief explanation of the drawing]

Figure 1 is a characteristic diagram showing the relationship between vertical square ratio and transfer output (4,7MHz), Figure 2 is a characteristic diagram showing the relationship between vertical square ratio and transfer output (130kHz), and Figure 3 is a characteristic diagram showing the relationship between vertical square ratio and transfer output (130kHz).
The figure is a characteristic diagram showing the relationship between the plate ratio and C/N of hexagonal ferrite magnetic powder. FIG. 4 is a schematic diagram showing an example of an air compression type magnetic field transfer device.

Claims (2)

[Claims] (1) In a magnetic recording medium in which a magnetic layer mainly consisting of hexagonal ferrite magnetic powder and a binder is formed on a non-magnetic support, and analog signals are transferred by a magnetic field transfer method, the hexagonal ferrite magnetic The average particle size of the powder is 0.08
μm or less, a plate ratio of 3 to 4, a perpendicular coercive force Hc of 800 Oe or less, and a perpendicular squareness ratio of 0.65 to 0.8. . (2) 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 digital signal is transferred by a magnetic field transfer method, wherein the hexagonal ferrite magnetic The average particle size of the powder is 0.08
μm or less, a plate ratio of 3 to 5, a perpendicular coercive force Hc of 800 Oe or less, and a perpendicular squareness ratio of 0.65 to 0.8. .