KR930009767B1 - Magnetic recording medium for slave and manufacturing method of it - Google Patents

Abstract

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Description

Slave magnetic recording medium and manufacturing method thereof

1 is a graph showing the relationship between the vertical angular ratio and the error rate of a slave magnetic recording medium.

2 is a graph schematically showing the relationship between the vertical square ratio and the reproduction output spectral characteristics in the DAT.

3 is a graph showing the relationship between the average number of existing blocks and an error rate having a undulation of not less than 0.03 μmpp in height per 1 mm of travel direction of a slave magnetic recording medium.

4 is a graph showing the relationship between the vertical square ratio and the transfer efficiency of the slave magnetic recording medium.

The present invention relates to a magnetic recording medium for a slave, in which a digital recording signal, in particular, a digital audio signal is transferred by a contact magnetic transfer method, and a method of manufacturing the same.

As a manufacturing method of DAT soft tape or the like, the master magnetic recording tape and the slave magnetic recording tape are closely adhered to each other in lieu of the direct recording transfer method of recording at a constant speed of 1: 1 from the master tape recorder to the slave tape recorder. For example, the contact transfer method for transferring a magnetization pattern as it is by applying a bias magnetic field to the part is widely used because high speed transfer is possible.

In this contact transfer method, a bias magnetic field is applied to the close contact between the master magnetic recording tape and the slave magnetic recording tape to transfer the signal magnetic field to the slave magnetic recording tape.

However, the slave magnetic recording tape used for the self-transfer method by performing connection transfer using the above-mentioned bias magnetic field has a correction magnetic force for the master so that the magnetic field of the master magnetic recording tape is not reduced by the bias magnetic field during contact transfer. It is required to be about 1 / 2-1 / 3 of the coercive force of the magnetic recording tape.

In the case of DAT, high density recording of 1 μm or less of the shortest wavelength is required, so recording characteristics are important in the short wavelength region.

However, in the normal vertical magnetic recording method, the magnetic field reduction can be ignored in the magnetization reversal area, so that high density recording is possible in the region of relatively low coercive force (Hc).

Here, a vertical magnetic recording medium in which a hexagonal ferrite powder whose axis is easy to magnetize in a direction perpendicular to the crystal plate surface is oriented so that its plate surface is parallel to the magnetic plane attracts attention as a magnetic recording tape for slaves of the magnetic transfer method. have.

However, it is known that the transfer efficiency in contact magnetic transfer is not as good as expected only by using a magnetic recording medium using a regular hexagonal ferrite powder in a magnetic recording tape for slaves.

Here, in order to improve the transfer efficiency of the magnetic recording medium using hexagonal ferrite powder, the angular ratio in the vertical direction is set to 0.7 or more, the coercive force (Hc) in the vertical direction is 800Oe or less, and the surface roughness Ra of the magnetic layer is 0.01. A method of um or less has been proposed (Japanese Patent Laid-Open No. 63-268124).

It was confirmed by the experiments of the present inventors that the transfer reproduction output can be increased as shown in FIG. 4, and has a good characteristic as a magnetic recording medium for slaves of analog signals.

However, according to the experiments of the present inventors, in the case of transferring a recording tape on which a digital signal such as a DAT is recorded, if the vertical angle ratio is too high, the error rate increases during reproduction and the reliability of the recording tape for the DAT is lowered. lost.

In the case of producing the DAT copy tape by the contact magnetic transfer method, it is also important to improve the reproduction output of the slave tape by increasing the transfer efficiency, but it is necessary to suppress the error rate within the correction allowance range by the error correction code.

In order to solve such a conventional difficulty, the inventors of the present invention have found that the vertical angular ratio of the magnetic recording medium for slaves is limited to 0.58 or more and less than 0.7, and at the same time, the number of convex portions on the surface is reduced to replicate the DAT. It has been found that the error rate of the tape can be reduced.

It is therefore an object of the present invention to provide a magnetic recording medium for a slave which can sufficiently obtain the transfer efficiency of a digital signal by the contact magnetic transfer method and can suppress the error rate low when reproducing the transferred digital signal.

Other objects of the present invention are apparent from the following description.

The slave magnetic recording medium of the present invention has a magnetic recording layer formed by applying a hexagonal ferrite magnetic component together with a binder component on a nonmagnetic substrate, and is recorded on a master magnetic recording medium by a contact magnetic transfer method. In the magnetic recording medium for slaves to which the signal is transferred, the above-described vertical angular ratio of the magnetic recording layer is 0.58 or more, less than 0.7 (more preferably, 0.59 or more and 0.68 or less), and its centerline average roughness Ra is 0.01 μm or less. In addition, the number of block portions having a undulation of a height of 0.03 탆 pp (height from the bottom of the valley to the peak of the mountain) at a pitch of 10-90 탆 is 10 or less per 1 mm of travel direction.

The above-mentioned "vertical square ratio" is a value of anti-magnetic field correction (4 pi M correction). In addition, "center line average roughness (Ra)" is a measurement method of roughness prescribed | regulated to JIS B0601, and shows the surface roughness on a chard with the measuring machine of the stylus tip radius of 2 micrometers, and measured length (l) more than 3 times the cut-off value (l When a center line is formed so that the area of the top and bottom is the same over), and the center line is the x-axis, the roughness curve is represented by f (x).

Is displayed.

The "block portion having a height of 0.03 µmpp or more at a pitch of 10-90 µm '' corresponds to the unevenness to be measured when measuring the" ten point average roughness Rz "of JIS B 0601.

That is, the "10-point average roughness Rz" is the average value of the height from the bottom of the recess of the five unevenness larger than the other unevenness within a predetermined reference length to the peak of the mountain, or the "10-point average roughness Rz". Corresponds to the height of a undulating block portion with a height of 0.03 μmpp or more at a pitch of 10 to 90 μm.

In the magnetic recording medium for slaves of the present invention, the vertical angular ratio is limited to the range of 0.58 or more and less than 0.7, as shown in FIG. 1, even if the vertical angular ratio is less than 0.58 and 0.7 or more, respectively. This is because the error occurrence rate of readout increases rapidly.

In general, in a magnetic recording medium on which a digital signal such as a DAT is recorded, for example, in a DAT, a predetermined reproduction output spectral characteristic (equivalent curve A) with respect to the frequency when a metal tape is recorded with a constant current head as shown in FIG. It is necessary.

If the vertical angular ratio of the magnetic recording medium for the slave is 0.7 or more, the transfer efficiency of the short wavelength region is improved in the contact magnetic transfer, and the reproduction output frequency characteristic is shifted toward the short wavelength region (equivalent diagram-curve B).

The reproduction output spectral characteristics are determined almost by the vertical square ratio.

As described above, when the reproduction output spectrum characteristic moves toward the short wavelength region, the reproduction output level in the long wavelength region decreases.

In the DAT, the waveforms are equalized by using an equalizer, so that their frequency characteristics do not cause inter-signal interference during reproduction.However, as described above, when the output decreases in a long wavelength region, a sufficient waveform equalization effect can be obtained. There is no error, and the error occurrence rate at the time of reading a digital signal increases.

This increases as the vertical angle ratio becomes 0.7 or more.

If the vertical angular ratio is less than 0.58, in the short wavelength region, sufficient transfer efficiency is not obtained at the time of contact magnetic transfer, and the reproduction output spectral characteristic is shifted to the long wavelength side (FIG. 2-curve C), so that the digital signal can be read in the same manner. Error rate increases.

That is, in the slave magnetic recording medium, the vertical angular ratio is adjusted within the range of 0.58 or more and less than 0.7, so that both the transfer efficiency during contact magnetic transfer and the suppression of the error generation rate during reproduction can be satisfied.

In the slave magnetic recording medium of the present invention, the surface roughness of the magnetic recording layer is defined as described above. When the center-to-coarse roughness exceeds 0.01 μm, the overall spacing with the master magnetic recording medium increases, and as a result, the transfer loss increases. In addition, if there are more than 10 block portions having a undulation of 0.03 μmpp or more in height per mm in the direction of travel in units of tens of micrometers, the loss increases again, resulting in a decrease in transfer efficiency and errors in digital signal reading during reproduction. This is because the rate increases.

Branch characteristics approximately the same as in FIG. 3

(Hc-640 ± 10Oe, Ms = 135 ± 5emu / cc, SQR = 0.66 ± 0.01)

The relationship between the average number of existences of the convex portions having the undulation of the above-described height of 0.03 μmpp or more and the error rate in the magnetic recording medium for the vertical slave is shown.

The hexagonal ferrite magnetic component used in the present invention is a compressed anisotropic hexagonal Baferite, Sr ferrite, Pb ferrite, Ca ferrite, M-type (Magnetoplumbite type) and W-type easy-to-magnetize axes perpendicular to the particle plate surface Or a portion of Ba of ferrite Ba substituted with other Sr, Pb, or Ca, or ion substituents thereof represented by the following general formulas.

General formula: M ₁ 0 · n (Fe _1-m M _2m ) ₂ O ₃ wherein M _{1 is} at least one selected from Ba, Sr, Ca, and Pb, and M ₂ is Ti, Co, Zn, In, Mn, At least one element selected from Ti, Sn, Ge, V, Nb, Sb, Ta, Cr, Mo, W, and the like, n represents 5.4-6.0, and m represents 0-0.2.

However, M ₂ has an average number of 3 to match the valence of Fe to be substituted.

As shown in the above general formula, the coercive force can be reduced by substituting a part of Fe which is a constituent element of hexagonal ferrite with various metals.

It is preferable that the coercive force of the hexagonal ferrite to be used is 400Oe-800Oe, the average particle diameter is 0.03 μm-0.08 μm, and the platelet ratio (particle size / thickness) is 3-5.

By satisfying the coercive force, average particle diameter, plate-ratio, and ratio of the binder component and the magnetic component described later, the vertical angular ratio can be controlled to a predetermined value.

In addition, as the binder component used in the present invention, polyacrylic resin, vinyl chloride resin, vinyl acetate resin, polystyrene resin, polyurethane resin, polyester resin, polycarbonate resin, epoxy resin, melamine resin, polyamide resin, polybutadiene resin, Polyacrylonitrile resins, phenol resins, polybutyral resins, epoxy resins, phenoxy resins, synthetic resins such as urea resins, and franin resins, and copolymerized resins thereof.

In addition, in order to improve the dispersibility of hexagonal ferrite magnetic components, resins containing sulfone groups, phosphoric acid groups, carboxyl groups or groups of alkali metal salts or alkaline earth metal salts thereof, or amino groups, alkyl amino groups, ammonium groups, alkylammonium groups, and hydroxyl groups You may add and use resin containing hydrophilic groups, such as these.

Among the components of these binders, a polyamine-based or polyisocyanate-based curing agent is usually added in order to increase the mechanical strength of the coating film when applied with a hexagonal ferrite magnetic component.

As for the compounding ratio of the above-mentioned hexagonal ferrite magnetic component and these binder components, 20 weight part or less, especially 8-16 weight part of binder components are suitable with respect to 100 weight part of hexagonal ferrite magnetic components.

The magnetic recording layer of the slave magnetic recording medium of the present invention may contain an appropriate amount of additives such as a lubricant, a dispersant, an abrasive, or carbon black, as necessary.

As a lubricant, various things, such as an anionic surfactant, a cationic surfactant, and a nonionic surfactant, can be used as a dispersing agent, such as fatty acid, fatty acid ester acid type silicone type, etc., for example.

In abrasive as _{TiO 2, Cr 2 O 3,} Al 2 O 3, it is appropriate to Mohs hardness of 5 or more, such as SiC, ZrO _2.

In the magnetic recording medium for slaves of the present invention, the above-mentioned six-orbital ferrite magnetic component, a binder component, and various additives as described above are sufficiently mixed with a solvent if necessary, and a curing agent such as a polyisocyanate compound is required if necessary. In addition, the hexagonal ferrite magnetic component and the binder component are prepared to have a ratio of 100: 8-16 (solid weight ratio), and the magnetic coating is preferably 5 μm (non-dried) on a nonmagnetic gas made of polyester, polyolefin, or the like. More preferably, after coating in the range of 2-4 μm (after drying), the magnetic coating film is subjected to an orientation treatment in a vertical magnetic field of 2-7 kOe, followed by drying, smoothing, etc. by a calender. .

In addition, the roughness conditions such as drying area temperature and coating speed, and the pressure, temperature and speed in the calendering process also affect the surface properties of the magnetic recording layer. Optimal conditions are different.

Therefore, it is better to obtain the optimum conditions for drying beforehand experimentally.

The slave magnetic recording medium of the present invention has an output characteristic suitable for the reproduction of digital signals such as for the DAT, and a higher transfer efficiency is obtained by a contact magnetic transfer method having a low error occurrence rate during reproduction.

Next, the Example of this invention is described.

Example 1

100 parts by weight of Ba ferrite powder (magnetic force = 630 Oe, average particle diameter = 0.05 μm, plate ratio = 3.5)

6 parts by weight of polyurethane resin

8 parts by weight of vinyl chloride-vinyl acetate copolymer resin

Alumina (average particle size = 0.3μm) 3 parts by weight

2 parts by weight of stearic acid

Methyl ethyl ketone / toluene / cyclohexanone 1: 1: 1 mixture 180 parts by weight

The above materials were mixed and then dispersed in a sand grinder for 2 hours.

After adding 3 weight part of hardening | curing agents and coronate L (brand name, the product made by Japan Polyurethane Co., Ltd.) to the obtained magnetic material, it apply | coated on the 10 micrometer-thick polyethylene de-lever film with a reverse coater.

Then, after vertically oriented in a 6kOe magnetic field and dried at a drying speed of 80m / min at 85 ℃, calendering at 200kg / cm linear pressure in a pressure roll of 70 ℃ cured at 40 ℃ for 3 days and then slitting A 3.81 mm wide DAT magnetic recording tape with a 3 μm magnetic recording layer was produced.

Example 2-7

Six types of magnetic recording tapes for slaves were produced under the same conditions as in Example 1 except that Ba ferrite powders having slightly different average particle diameters and platelet ratios were used instead of the Ba ferrite powder of Example 1.

EXAMPLE

[Comparative Example 1-4]

In Example 1, four types were used under the same conditions as in Example 1 except that the magnetic field strength during vertical alignment was changed to 10 kOe magnetic field strength (Comparative Examples 1 and 2) and the magnetic field strength was 0 (Comparative Examples 3 and 4). A magnetic recording tape for slaves was produced.

[Comparative Example 5-7]

In Example 1 described above, two types of magnetic recording tapes for slaves having different surface roughness patterns were produced under substantially the same conditions except that the drying conditions (temperature and speed of the drying zone) were changed.

[Comparative Example]

For each of the magnetic recording tapes of the slaves of the Examples and Comparative Examples thus obtained, the corrected magnetic force and the vertical angular ratio surface roughness (Ra and the average number of convex portions of the undulation of the undulation of 0.03 μmpp or more per 1 mm of running direction) were measured and contacted. The transfer efficiency by magnetic transfer and the error rate (block error rate) when reproducing the DAT recording signal transferred by contact magnetic transfer were measured.

The above measurement results are shown in the following table.

In addition, the average number of undulation blocks of 0.03μm or more per 1mm running direction in tens of μm length was measured using a three-dimensional unfolding machine (2μm stylus tip radius), and the tape surface roughness was measured. Obtained by taking the average of

Moreover, the transfer efficiency was calculated | required as follows by contact magnetic transcription.

First, using a DAT mirror master device of a coercive force 2000Oe (relative speed 3.13m / sec), a rectangular wave with a frequency of 4.7MHz was recorded in a mirror pattern in advance to make a master tape, and this master tape and each slave described above. The magnetic recording tape was brought into close contact with the air compression method, and a bias magnetic field was applied to maximize the transfer output, thereby transferring the signal magnetic field.

Then, using the slave tape obtained as described above, the transfer reproduction output was measured by using a spectrum analyzer with a DAT deck.

In addition, at the time of reproduction, the DAT error rate was measured by using an error detector.

TABLE 1

Claims (7)

A slave magnetic recording medium having a magnetic recording layer obtained by applying a nonmagnetic gaseous hexagonal ferrite magnetic component together with a binder component, wherein digital signals recorded on a master magnetic recording medium are transferred by a contact magnetic transfer method. The above-described angular ratio of the magnetic recording layer is 0.58 or more and less than 0.7, and its centerline average roughness Ra is 0.01 μm or less and the number of wave-shaped convex portions having a height of 0.03 μmpp or more at a pitch of 10-90 μm is 10 or less per 1 mm of driving direction. The hexagonal ferrite magnetic component has an average particle diameter of 0.03 to 0.08 μm, and the mixing ratio of the hexagonal ferrite magnetic component and the binder component is 100: 8 to 16 (parts by weight). Record carrier. The method of claim 1, wherein the hexagonal ferrite magnetic component is a general formula: M ₁ O · n (Fe _1-m M _2m ) ₂ O ₃ , General formula: M ₁ On (Fe _1-m M _2m ) ₂ O ₃ ( Wherein M ₁ is at least one selected from Ba, Sr, Ca, and Pb, and M ₂ is Ti, Co, Zn, In, Mn, Ti, Sn, Ge, V, Nb, Sb, Ta, Cr, Mo, W At least one element selected from the back and the like, n denotes a number of 5.4 to 6.0, and m denotes a number of 0 to 0.2, except that an average singer of M ₂ is 3.). . The magnetic recording medium for a slave according to claim 1, wherein the vertical angular ratio of the recording layer is 0.59 or more and 0.68 or less. The magnetic recording medium for a slave according to claim 1 or 2, wherein the hexagonal ferrite magnetic component has a sheet ratio of 3 to 5 and a coercive force of 400Oe to 800Oe. The magnetic recording medium for a slave according to claim 1 or 2, wherein the binder component is made of synthetic resin. 6. The binder component according to claim 5, wherein the binder component is mainly polyacryl resin, vinyl chloride resin, vinyl acetate resin, polystyrene resin, polyurethane resin, polyester resin, polycarbonate resin, epoxy resin, melamine resin, polyamide resin, poly Butadiene resin, polyacrylonitrile resin, phenol resin, polybutyral resin, phenoxy resin, urea resin, furan resin, such as synthetic resins and copolymerized resins thereof, characterized in that it comprises one or two or more resins Magnetic recording medium for slave. A process of applying a magnetic paint containing a hexagonal ferrite magnetic component and a binder component in a ratio of 100: 8 to 16 (weight ratio) on a nonmagnetic gas, and in a magnetic field of 2 to 7 kOe to a nonmagnetic gas to which the magnetic paint is applied. In the method of manufacturing a magnetic recording medium for a slave, which is a step of forming a magnetic recording layer by drying and a calendering process on the magnetic recording layer, the step of forming the magnetic recording layer by drying is the magnetic recording layer. Contact line transfer, characterized in that the center line average roughness Ra is 0.01μm or less, and the temperature and speed are controlled so that the number of wave-shaped convex portions having a height of 0.03μmpp or more at a pitch of 10 to 90μm is 10 or less per 1mm of driving direction. A method of manufacturing a magnetic recording medium for a slave, in which a digital signal recorded on the master magnetic recording medium is transferred by a method.

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