JPS63268124A - Magnetic recording medium for slave - Google Patents

Abstract

PURPOSE:To improve transfer efficiency in a short wavelength region below a specific wavelength by specifying the squareness ratio in the perpendicular direction of a magnetic recording medium at a specific value or above, the coercive force in the perpendicular direction at a prescribed value or below and the surface roughness of a magnetic layer at a specified value or below. CONSTITUTION:The squareness ratio in the perpendicular direction of the magnetic medium for slave by a magnetic field transfer method which is formed with the magnetic layer essentially consisting of hexagonal ferrite magnetic powder and binder on a nonmagnetic base is specified at >=0.7, the coercive force Hc in the perpendicular direction at <=800oersted and the surface roughness Ra of the magnetic layer at <=0.01mum. Air is fed in an arrow A direction from the rear 1b side of a bias head 1 in the transfer of an air press contact system. This air A is blown out by a prescribed pressure from the side face of the head on the front 1a side of the head 1 to the side face of a transfer drum 2 so that the magnetic recording medium 3 for master and the magnetic recording medium 4 for slave are brought into pressurized contact with the side face of the drum 2. A bias magnetic field is impressed to the media 3a, 4 by the air blown out to the head 1 side while the media are brought into pressurized contact in such a manner, by which the transfer is satisfactorily executed in a short wavelength region of <=1mum.

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 for high-density recording applications.

[Summary of the invention]

The present invention provides a slave magnetic recording medium in which a recording signal recorded on a master magnetic recording medium is transferred by a magnetic field transfer method, and provides a vertical squareness ratio, a vertical coercive force Hc, and a vertical coercive force Hc of the slave magnetic recording medium. By defining the surface roughness Ra of the magnetic layer, it is intended to improve the transfer efficiency in a short wavelength region of 1 μm or less.

[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 coercive force of the master magnetic recording medium is demagnetized 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. It's for a reason.

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 200
The limit is about 0 mill steps. Therefore, at present, it is necessary to use a magnetic recording medium with a low coercive force of 800 Oe or less as a usable slave magnetic recording medium. For this reason, what has been put into practical use as a slave magnetic recording medium is Co-coated -F2O3 having a coercive cuff around 000000000000000000000000000000000000000000000.

By the way, there are some technologies that have been put into practical use in recent years, such as digital audio tape recorders (hereinafter referred to as DAT),
In 8fi video tape recorders and the like, high-density recording is performed with a shortest recording wavelength of 1 μm or less. When such a short wavelength signal is used for transcription, the residual magnetic flux density Br,
Co-adhered with low coercive force Hc - Fezos, Cr
In a longitudinal magnetic recording medium using magnetic powder such as O□, the increase in self-demagnetization loss in the short wavelength region causes the output
Both C/N were insufficient and it could not be used.

Therefore, as a slave magnetic recording medium used for transferring recording signals in the above-mentioned DAT, 8-Yu video tape recorder, etc. that perform high-density recording, magnetic recording media with a recording wavelength of 1 μm or less are suitable despite having a low coercive force Hc. There is a demand for the emergence of something with even higher output characteristics.

On the other hand, in recent years, there have been various attempts to achieve high-density recording by actively utilizing the magnetization component in the perpendicular direction using plate-shaped hexagonal ferrite fit powder whose easy axis of magnetization is perpendicular to the plate surface. It is being done.

In general, in the perpendicular magnetic recording method, the demagnetizing field at the magnetization reversal boundary can be ignored due to the magnetization distribution, so it is said that it can be used for high-density recording from a relatively low coercive force (c). .

Therefore, a magnetic recording medium using the above-mentioned hexagonal ferrite magnetic powder is used not only in the field of head recording and reproduction, but also as a magnetic recording medium for a slave used when transferring high-density recorded signals by a magnetic field transfer method. It is proposed that.

[Problem that the invention seeks to solve]

However, even if the above-mentioned hexagonal ferrite magnetic powder is used as a slave magnetic recording medium under normal conditions,
It has become clear that although the transfer efficiency is somewhat higher than that of a slave magnetic recording medium using CO-coated r-Fetos or crow, sufficient transfer efficiency cannot be obtained.

Therefore, the present invention has been proposed in view of such a situation, and has a short wavelength fiIJ of 1 μm or less! It is an object of the present invention to provide a slave magnetic recording medium that can improve transfer efficiency in i.

c. Means for Solving Problems] In order to achieve the above-mentioned object, the inventors of the present invention have conducted extensive research, and as a result of their intensive research, the present inventors have developed a method for applying a transfer bias magnetic field by press-bonding a master magnetic recording medium and a slave magnetic recording medium. In the magnetic field transfer method in which the recording signal on the master magnetic recording medium is transferred to the slave magnetic recording medium by applying a magnetic field, the perpendicular squareness ratio of the slave magnetic recording medium, the perpendicular coercive force He, and the surface roughness of the magnetic layer are By defining Ra within a predetermined range,
We have found that this method improves transfer efficiency in the short wavelength region.

The present invention has been proposed based on the above-mentioned findings, and is for a slave device using a magnetic field transfer method, in which a magnetic layer mainly composed of hexagonal ferrite magnetic powder and a binder is formed on a non-magnetic support. The magnetic recording medium is characterized in that the perpendicular squareness ratio of the slave magnetic recording medium is 0.7 or more, the perpendicular coercive force Hc is 800 Oe or less, and the surface roughness Ra of the magnetic layer is 0.01 μm or less. That is.

In recording with a normal magnetic head, if the vertical squareness ratio is 0.55 or more, the recording efficiency will not improve much 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 0.7, the transfer output will be lower and the transfer efficiency will be lower, even though the short wavelength output in head recording regeneration is the same. This will lead to the inconvenience of being inferior. That is, in the case of recording by magnetic field transfer, as shown in FIG. 1, the relationship between the vertical square ratio and the transfer efficiency is such that the higher the vertical square ratio, the higher the transfer efficiency. This is because the transferred vector magnetization pattern has a smaller demagnetizing field coefficient at a shorter wavelength than the vector magnetization pattern created by head recording, and the contribution of the perpendicular magnetization component is larger, resulting in self-demagnetization. This is thought to be because the loss can be kept low. It is also conceivable that a large vertical squareness ratio strengthens the magnetic coupling between the master magnetic recording medium and the slave magnetic recording medium. That is, in the present invention, it is preferable that the squareness ratio in the vertical direction of the slave magnetic recording medium is 0.7 or more, in view of the fact that it is 0 or more, which can be said to be an effect unique to magnetic field transfer. The above-mentioned vertical squareness ratio indicates a value after demagnetizing field correction.

Also, the perpendicular coercive force Ha of the slave magnetic recording medium
is larger than 800 oersteds, the demagnetization of the master magnetic recording medium due to the bias magnetic field increases,
This results in a decrease in transfer efficiency and a decrease in transfer output in repeated transfers. Therefore, the perpendicular coercive force Hc of the slave magnetic recording medium is preferably 800 Oe or less. It is preferable that the coercive force in the vertical direction is not less than 600 Oe. If the coercive force in the perpendicular direction is less than 600 Oe, the short wavelength output will be low regardless of head recording or magnetic field transfer recording, making it impractical. Not.

Furthermore, the surface roughness Ra of the slave magnetic recording medium is 0.
If it is larger than 0.01 μm, the spacing loss between the re-magnetic recording media increases during transfer from the master magnetic recording medium to the slave magnetic recording medium, resulting in a disadvantage that the transfer efficiency decreases. It is preferable that the slave magnetic recording medium has a surface roughness Ra of 0.01 μm or less. Note that the surface roughness Ra is the centerline average roughness shown in Japanese Industrial Standards (JIS) BO601.

Orthogonal ferrite magnetic powder is used as the magnetic powder for the slave magnetic recording medium having the above characteristics. The hexagonal crystal monocrystalline powder used as the magnetic powder of the above-mentioned slave magnetic recording medium has the general formula % formula % (1) [However, in the formula, M represents at least one of Ba, Sr, and Ca. and n is 5-6. ] These are hexagonal ferrite particles.

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 magnetic brambite 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, C
u.

represents at least one of Zn, In, Go, and Nb,
m is θ~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 hexagonal ferrite described above must be fine particles with an average grain size of 0.1 μm or less,
In particular, fine particles of about 0.05 to 0.07 μm are preferable. Further, the plate ratio is preferably a high plate ratio of about 4 to 6. By satisfying the conditions of the average particle size and plate-like ratio, the value of the squareness ratio in the vertical direction can be set to a predetermined value.

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, Synthetic rubber resins such as polyester resins and polybutadiene, phenolic resins, epoxy resins, polyurethane curable resins, melamine resins, alkyd resins, silicone resins, acrylic reaction resins, epoxy-polyamide resins, nitrocellulose-melamine resins,
Mixtures of high molecular weight polyester 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, etc. can be mentioned.

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

M represents a hydrogen atom, an alkali metal or a hydrocarbon group; polyurethane resins, polyester resins, vinyl chloride-vinyl acetate copolymers, vinylidene chloride copolymers, Acrylic acid ester copolymers, butadiene copolymers, etc. can be used.

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

The magnetic layer may be internally added or top-coated with a geothermal lubricant such as these resin binders, and further may have an abrasive or a dispersant added thereto as necessary.

A magnetic paint made by kneading Eft powder, a resin binder, etc. is applied onto a non-magnetic support to form a magnetic layer.The material for the non-magnetic support is polyester such as polyethylene terephthalate. polyolefins such as polyethylene and polypropylene, cellulose derivatives such as cellulose triacetate, cellulose diacetate and cellulose acetate butyrate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, plastics such as polycarbonate, polyimide and polyamideimide, aluminum alloys, Light metals such as titanium alloys, ceramics such as alumina glass, etc. are used. The form of this non-magnetic support is a film sheet disk,
It may be a card, a drum, etc.

In the slave magnetic recording medium according to the present invention, magnetic signals are transferred from the master magnetic recording medium by a magnetic field transfer method. The transfer device used for transferring the magnetic signal is, for example, one based on a roller pressure bonding method or an air pressure bonding method.

The master magnetic recording medium used was formed with a ferromagnetic metal thin film having a coercive force Hc of 1800 (Oe) or more as a magnetic layer. 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, transfer efficiency.

A metal magnetic recording medium having a coercive force He of about 2000 (Oe) and a residual magnetic flux density Br of 2700 G or more is preferable in terms of frequency characteristics, phase characteristics, demagnetization of the master magnetic recording medium, and the like.

[Effect]

By using hexagonal ferrite I powder as the magnetic powder of the slave magnetic recording medium, and specifying its vertical squareness ratio, vertical coercive force Hc, and surface roughness Ra of the magnetic layer to predetermined values, Transfer efficiency can be improved in the short wavelength region of 111 m or less.

〔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.

Example 1 Magnetic coating composition Barium ferrite magnetic powder 100 parts by weight (average particle size 0.07, plate ratio 4) Polyurethane resin 15 parts by weight Vinyl chloride-vinyl acetate copolymer resin 15 parts by weight Abrasive (
Crt Ox) 5 parts by weight Dispersant (lecithin) 1 part by weight Methyl ethyl ketone 110 parts by weight Toluene
50 parts by weight cyclohexane
After kneading 50 parts by weight of the above composition in a ball mill for 20 hours, 3 parts by weight of a curing agent (manufactured by Nippon Polyurethane Co., Ltd., trade name: Coronet L) was added, and the magnetic paint was filtered through a filter with an average particle size of 1 μm. Obtained.

This magnetic paint was applied onto a polyester film with a thickness of 9 μm, vertically aligned, dried, and the surface of the magnetic layer was processed using a super calender that can produce an extremely smooth surface. A roll of 0 μm was obtained. Then, this was cut to a width of 3.81 fins to prepare a sample tape.

Example 2 In the composition of Example 1, instead of the barium ferrite magnetic powder with an average particle size of 0.07 and a platelet ratio of 4, an average particle size of 0.07,
A sample tape was prepared in the same manner as in Example 1, except that barium ferrite magnetic powder with a plate ratio of 5 was used.

Comparative Example 1 In the composition of Example 1, instead of the barium ferrite magnetic powder with an average particle size of 0.07 and a platelet ratio of 4, an average particle size of 0.05,
A sample tape was produced in the same manner as in Example 1 except that barium ferrite magnetic powder with a plate ratio of 2 was used and no vertical alignment treatment was performed.

Comparative Example 2 In the composition of Example 1, instead of the barium ferrite magnetic powder with an average particle size of 0.07 and a platelet ratio of 4, an average particle size of 0405,
A sample tape was prepared in the same manner as in Example 1 except that barium ferrite magnetic powder with a plate ratio of 2 was used.

Comparative Example 3 In the composition of Example 1, instead of the barium ferrite magnetic powder with an average particle size of 0.07 and a platelet ratio of 4, an average particle size of 0.05,
A sample tape was prepared in the same manner as in Example 1 except that barium ferrite magnetic powder with a plate ratio of 2 was used and the calender treatment was performed using a normal calender roll with a rough surface.

Comparative Example 4 Same average particle size as the barium ferrite magnetic powder used in Example 2, 0.0? A sample tape was prepared in the same manner as in Example 1, except that barium ferrite magnetic powder having a platelet ratio of 5 and a powder coercive force 150 (Oe) higher than that of barium ferrite magnetic powder was used.

For each sample tape obtained as above,
Magnetic flux density (Bm) and vertical squareness ratio ′
(R3Z) + Coercive force (llc) and surface roughness (Ra) were measured, head recording/reproduction and magnetic field transfer were performed, reproduction output was measured, and transfer efficiency was determined.

In addition, for head recording and playback, the trunk width is 20 μm,
Using a metal head with a gap length of 0.25 μm, a square wave with a frequency r = 4.7 Mllz was recorded and reproduced at a relative speed of 3 m/sec, and the output level at that time was measured using a spectrum analyzer.

In addition, magnetic field transfer uses coercive force Hc-20 as a mother tape.
A mirror pattern was previously recorded on a 00 (Os) metal tape 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.1. Transfer was performed at a speed of Om/sec.

Note that 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 sent from the rear (1b) side of the bias head (1) as shown by arrow A in Figure 2, and this air A is sent to the head located on the front (1a) side of the bias head (1). The master magnetic recording medium (3) and the slave magnetic recording medium (4) are blown onto the side surface of the transfer drum (2) by blowing with a predetermined pressure from the side surface of the transfer drum (2) facing the side surface of the transfer drum (2). ). In this way, the pressure of the air blown out from the bias head (1) side causes the master magnetic recording medium (3) and slave magnetic recording medium (
Transfer is performed by applying a bias magnetic field using the bias head (1) while pressing the 4). After the transfer is completed, reproduction at a frequency f = 4.7 MHz is performed using the same reproduction device used for head recording and reproduction. The output level was measured using a spectrum analyzer.

Furthermore, the transfer efficiency was determined using the following relational expression.

The measurement results are shown in Table 1.

(Left below) Table 1 As is clear from Table 1, Examples 1 and 2 are as follows:
Since the perpendicular squareness ratio, magnetic flux density, coercive force 1 and surface roughness satisfy predetermined conditions, the transfer efficiency in the short wavelength region of 1 μm or less is extremely excellent.

In addition, Comparative Example 1 and Comparative Example 2 have a low vertical squareness ratio,
Comparative Example 3 had poor surface roughness, and Comparative Example 4 did not satisfy the conditions required for a slave magnetic recording medium, such as the high coercive force of the magnetic recording medium, so the master magnetic recording medium had large demagnetization. , all have low transfer efficiency in the short wavelength region of 1 μm or less.

〔Effect of the invention〕

As is clear from the above explanation, in a slave magnetic recording medium to which a recording signal recorded on a master magnetic recording medium is transferred by a magnetic field transfer method, the vertical squareness ratio of the slave magnetic recording medium is coercive force Hc
Since the surface roughness Ra of the magnetic layer is defined to a predetermined value, it is possible to improve the transfer efficiency in a short wavelength region of 1 μm or less.

Therefore, it has great industrial value in that, for example, so-called soft tapes can be reproduced in large quantities at high speed.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram showing the relationship between vertical squareness ratio and transfer efficiency. FIG. 2 is a schematic diagram illustrating the air pressure bonding method used in magnetic field transfer. Tari V mei l! ! Form Rs Figure 1 Figure 2 Procedural Amendment Cap) July 3, 1985 1, Indication of the case 1988 Patent Application No. 102808 2, Name of the invention Slave magnetic recording medium 3, Make amendments Relationship with the case Patent applicant address: 6-7-35, Kitashina-yo, Tokyo Parts-Yo-ku Name (2
18) Sony Corporation Representative Ohga
Norio Voluntary 6, "Detailed Description of the Invention" column 7 of the specification to be amended, page 2, line 18 to line 19 of the specification of contents of the amendment, "Maser Magnetic Recording Medium Maintenance" The magnetic force is demagnetized,
'' has been corrected to ``The master magnetic recording medium is demagnetized.'' On page 6, line 5 of the specification, the statement "transfer efficiency is improved" is corrected to "transfer efficiency is improved." From line 17 to line 18 of page 6 of the specification, the statement ``The recording efficiency does not improve much due to the relationship with the saturation magnetic flux density'' is replaced by ``short wavelength due to the relationship with the saturation magnetic flux density''. The head recording and playback output in this area will not improve much.'' The description "high plate-like ratio" on page 10, line 15 of the specification is amended to read "plate-like ratio." From line 2 to line 3 of page 18 of the specification, the statement ``barium ferrite magnetic powder with an average particle size of 0.05 and a plate-like ratio of 2'' was replaced with ``a barium ferrite magnetic powder with an average particle size of 0.07 and a plate-like ratio. The barium ferrite powder with a ratio of 5 is corrected as ``. In the second line from the bottom of No. 21 of the specification, the statement "The demagnetization of the master magnetic recording medium is large" is deleted. that's all

Claims (1)

[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 recording signals are transferred by a magnetic field transfer method, and the magnetic recording medium has a vertical rectangular shape. Ratio is 0.7 or more, vertical coercive force H
1. A magnetic recording medium for a slave, characterized in that c is 800 Oe or less, and the surface roughness Ra of the magnetic layer is 0.01 μm or less.