JPH04103020A - Mother magnetic recording medium - Google Patents

Abstract

PURPOSE:To increase the transfer efficiency of recording signals by specifying the aspect ratio, coercive force and volume content of hexagonal ferrite powder in a magnetic recording layer. CONSTITUTION:It is specified that the hexagonal ferrite powder in the magnetic recording layer has 3 - 6 aspect ratio, >= 1500, Oe coercive force and >= 40 % volume content. If the temp. coefft. of the coercive force Hc is positive (Hc increases with temp.), an equal effect of recording to a medium having larger coercive force Hc can be obtained with the medium of this invention by performing contact magnetic transfer at higher temp. than the recording temp. Moreover, if the temp. coefft. of coercive force of a slave tap is negative, difference of coercive force between the mother tape and the slave tape further increases. Thereby, the transfer efficiency of recording signals is increased and the reproduction output is extremely increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a mother magnetic recording medium suitable for duplicating (copying) required magnetic recording information using a high-speed contact transfer method.

(Prior Art) As an effective method for manufacturing (copying) video tapes, audio tapes, etc., the following contact transfer method is often used.

That is, the magnetic surfaces of a recorded mother magnetic recording medium (mother tape) and an unrecorded slave magnetic recording medium (slave tape) are run in close contact with each other, and an alternating current bias magnetic field, for example, is applied to the closely contacted area. As a result, a contact transfer method has been developed in which the magnetization pattern recorded on the mother tape is directly transferred to the slave tape, and it is becoming widely used because high-speed transfer is possible.

This contact transfer method includes, as described above, a method in which a sufficient signal magnetic field is transferred to the slave tape by applying a required bias magnetic field to the part where the mother tape and slave tape are in close contact with each other. , a method is known in which a signal magnetic field is transferred by applying heat above the Curie point to the close contact portion.

By the way, in the mother tape used in the magnetic transfer method that performs contact transfer using a bias magnetic field, the coercive force of the magnetic recording layer is adjusted to the magnetic field of the slave tape so that the magnetic field is not demagnetized by the bias magnetic field applied during contact transfer. It is necessary to make it thicker than the coercive force of the recording layer. Furthermore, since high-density recording is particularly performed on video tapes and digital audio (DAT) tapes, it is important that they have excellent recording and reproducing characteristics in the short wavelength region.

On the other hand, perpendicular magnetic recording media using hexagonal ferrite powder, which have relatively low coercive force but have excellent recording and reproducing characteristics in the short wavelength region, are attracting attention as slave tapes used in such contact transfer methods. There is. That is,
This is because the axis of easy magnetization of hexagonal ferrite powder is perpendicular to the plate surface, so that the demagnetizing field at the magnetization reversal boundary can be almost ignored in the short wavelength region.

However, simply using a magnetic recording medium constructed using hexagonal ferrite powder as the magnetic powder as a slave tape does not sufficiently improve the transfer efficiency in contact magnetic transfer.

Therefore, in order to deal with this problem, a proposal has been made to improve the transfer efficiency by increasing the vertical squareness ratio of the slave tape using the hexagonal ferrite powder to 0.7 or more (particularly). 63-268124), a mother tape whose magnetic flux density increases as the temperature decreases, and a slave tape whose coercive force decreases as the temperature decreases.
A proposal has been made to improve transfer efficiency by performing contact transfer at low temperatures (Japanese Patent Laid-Open No. 1-25e020).

(Issue 8 to be solved by the invention) However, as mentioned above, by increasing the vertical squareness ratio of the slave tape used for contact magnetic transfer,
If you try to improve the transfer efficiency, the playback output of the slave tape after transfer will improve;
For magnetic recording tapes, if the perpendicular squareness ratio becomes too high, the error rate during reproduction increases. As a result, the inventor's experiments have revealed that the reliability of the tape as a DAT magnetic recording tape is reduced.

In addition, in the case of the contact transfer method at low temperatures, the cooling device is complicated, which not only leads to increased costs, but also
There are technical problems such as easy moisture condensation.

The present invention has been made to address these conventional problems, and it not only has high transfer efficiency of recording signals by the contact magnetic transfer method, but also enables the slave magnetic recording medium to fully demonstrate its functions. The object of the present invention is to provide a mother magnetic recording medium that has excellent magnetic properties and exhibits stable and high performance even after repeated contact transfer.

[Structure of the Invention] (Means for Solving the Problems) A magnetic recording medium for a mother according to the present invention is a mother magnetic recording medium in which a magnetic recording layer is provided by applying hexagonal ferrite powder together with a binder component onto a non-magnetic substrate. In the magnetic recording medium, the hexagonal ferrite powder in the magnetic recording layer has a plate ratio of 3 to 6, a coercive force of 1500 Oe or more, and a volume content of 40% or more.

In the mother magnetic recording medium (mother tape) of the present invention, the volume content of the ferromagnetic powder in the magnetic recording layer is set to be higher than that of ordinary magnetic recording media by <40x or more for the following reasons. In other words, unlike normal slave magnetic recording media (slave tapes), mother tapes are recorded and reproduced only once by a magnetic head, and do not require much durability for the head, so they usually contain large amounts of additives. This is because the amount of additives such as abrasives, antistatic agents, and lubricants added can be kept to the necessary minimum.

By using the mother tape according to the present invention in which ferromagnetic powder is contained in the magnetic recording layer at a high rate of 40% or more,
When contact magnetic transfer is performed, there is a sharp upward trend in the reproduction output of the manufactured slave tape.

In addition, in order to form a magnetic recording layer containing such a high volume content of ferromagnetic powder, acicular magnetic powder with a large aspect ratio is not suitable, and the particle size/plate thickness ratio (plate ratio) A hexagonal ferrite powder such as Ba-ferrite, which has a large coercive force and can be vertically aligned, is suitable.

The plate ratio of such hexagonal ferrite powder is about 3 to 6, more preferably 3.
5 to 4.5. That is, as the plate ratio increases, the filling rate (content rate) of the magnetic powder decreases, so it is necessary to suppress the value to 6 or less. Conversely, if this value becomes smaller, the orientation of the magnetic powder will decrease, and if it is less than 3, a high orientation ratio (squareness ratio) cannot be expected.

Further, in the mother tape according to the present invention, the vertical squareness ratio (orientation ratio) of the magnetic recording layer is as follows for the reason shown below.
It is preferably 0.7 or more, more preferably 0.75 or more. In other words, the playback output of a Ba-ferrite tape (slave tape) subjected to contact magnetic transfer using a metal tape as a mother tape depends on the vertical squareness ratio of the magnetic recording layer, as a result of the combination of the effects of vertical bias and vertical alignment. However, it is known that as the vertical squareness ratio increases, it improves significantly.
- By using a ferrite tape, the transfer efficiency under a vertical bias magnetic field is greatly improved, and the reproduction output of the slave tape after transfer is further improved. Furthermore, as a slave tape for performing contact magnetic transfer at this time, the magnetic recording layer contains hexagonal ferrite powder such as B ne ferrite, and preferably 0.6 or more,
．． It is desirable to use a magnetic recording medium with a perpendicular squareness ratio of 7 or more. The reason for this is that if the perpendicular squareness ratio of the magnetic recording layer is less than 0.6, sufficient transfer efficiency cannot be obtained in the short wavelength region, and the reproduced output spectrum characteristics shift to the long wavelength side, resulting in digital signal This is undesirable because the error rate during reading increases.

Note that the vertical squareness ratio here is calculated by demagnetizing field correction (4π field correction)
Indicates the value obtained by

Further, in the mother tape according to the present invention, the above-mentioned Ba
- The coercive force He of the magnetic recording layer containing ferromagnetic powder such as ferrite is at least 2 of the coercive force He of the slave tape.
It is required to be more than double.

However, the larger the coercive force 1 (c), the less demagnetized it is during contact transfer, but the problem is that it is difficult to write signals, so in the master tape of the present invention, the coercive force H
c is 1500 Oe or more at room temperature, saturation magnetization Ms is 14 Oe
It is desirable that it be at least mu/cc.

(Function) In the mother tape according to the present invention, 40% of ferromagnetic powder such as hexagonal ferrite powder is contained in the magnetic recording layer.
Since it is contained at such a high volume percentage, it is possible to achieve high transfer efficiency of recording signals by the contact magnetic transfer method and mass-produce copying and manufacturing of slave tapes with extremely high reproduction output.

Therefore, in the mother tape according to the present invention, the coercive force H
If the temperature coefficient of e is positive (He increases as the temperature increases), by performing contact magnetic transfer at a temperature higher than the temperature at which the signal was recorded, it is possible to increase the It is possible to achieve the same effect. For example, if a mother tape with a temperature coefficient of +5 Oe/°C is used and signals are recorded at -50°C and contact magnetic transfer is performed at +70°C, the same effect as an increase in coercive force He by 600 Oe can be obtained. It will be done.

Furthermore, at this time, if the temperature coefficient of the coercive force He of the slave tape is negative, the difference between the coercive force He of the mother tape and the coercive force He of the slave tape becomes even larger, so that the demagnetization of the master tape is It becomes extremely unlikely to occur. In addition, as a magnetic powder with a positive temperature coefficient of coercive force He, Co
, Ba-ferrite powder represented by Ti-substituted Ba-ferrite is known, while magnetic powder having a negative temperature coefficient includes Ba-ferrite containing Sn as a substituent element, 7-Fe2 03 , Co substitution-
Examples include Fe203 and Fe powder.

In this way, if an information signal is recorded at a low temperature on a mother tape with a positive temperature coefficient of coercive force He, and contact magnetic transfer is performed at a much higher temperature, the coercive force H of the mother tape at the time of transfer is
It is possible to substantially increase c to around 3000 Oe, and the coercive force tic of the slave tape used can also be increased accordingly, which is expected to improve the characteristics. That is, if the mother tape according to the present invention in which the temperature coefficient of the coercive force He is positive is used, the coercive force He of the slave tape, which was conventionally suppressed to about 650 Oe, can be reduced to 750 Oe to 750 Oe.
It will be possible to increase the power by 1,500 Oe.

Furthermore, when the mother tape of the present invention is used, regardless of the type of magnetic powder contained, the slave tape may contain magnetic powder with a particle size smaller than that of the ferromagnetic powder of the mother tape. It is desirable to use it. For example, when Ba-ferrite powder is used for both media, the magnetic powder constituting the magnetic recording layer of the mother tape should have a specific surface area of less than 80 rrr/g, and the magnetic powder of the slave tape should have a specific surface area of less than 80 rrr/g. It is desirable to use a material having a specific surface area of 30rrr/sr or more, preferably with a specific surface area difference of 5rIf/g or more from the magnetic powder of the mother tape. By performing contact magnetic transfer using both of these tapes, a slave tape with better S/N characteristics than the mother tape can be obtained.

(Example) The present invention will be described in detail below. Before explaining specific examples, a general explanation will be given of the structure of the mother tape according to the present invention.

Examples of the ferromagnetic powder used in the mother tape of the present invention include hexagonal ferrite powders as shown below. In other words, the hexagonal ferrite powder may be uniaxially anisotropic hexagonal Ba-ferrite, X-type (Magnetopluibltetype) or V-type, in which the axis of easy magnetization is perpendicular to the particle plate surface, Sr-ferrite, Pb- Ferrite, Ca-Ba like ferrite
- Part of Ba in ferrite is replaced with other elements S', PbSCa
Examples include those substituted with , or ion-substituted products of these represented by the following general formula.

General formula: AO・n f(Fe M )l 20
3T1 ■ (In the formula, A is at least one element selected from Ba5Sr, Ca, Pb, M is T1, Co, Zn, I
n, Mn, Tj.

Sn, Ge, V, Nb, 5bSTa, Cr,
At least one element selected from No, W, n is a number from 5.4 to 6.0, and - is a number from 0 to 2. However, M
The average number of weights is set to 3 in order to match the valence of Fe to be replaced. ) As shown in the above general formula, in the hexagonal ferrite powder used in the present invention, by substituting a part of the constituent Fe with various metal elements, the coercive force Hc can be adjusted to an appropriate value. has been reduced.

That is, in the mother tape according to the present invention, the coercive force He is 1200 to 3500 Oe, more preferably 20
It is desirable to use a hexagonal ferrite powder controlled to have a coercive force of 400 to 1,500 Oe, more preferably 600 to 1,500 Oe in a slave tape to which such a master medium is transferred by contact magnetic transfer.
It is desirable to use hexagonal ferrite powder controlled to 1000 Oe.

The hexagonal ferrite powder used in the mother tape has an average particle size of 0.02 to 0.08 μm and a particle size/plate thickness ratio (plate ratio) of 3 to 6. . In this way, by limiting the coercive force, average grain size, plate ratio, etc. of the hexagonal ferrite that constitutes the magnetic recording layer, as well as the amount of the binder component to be described later, to a certain range, the perpendicular It becomes possible to control the squareness ratio to a desired value of 0.7 or more.

The binder component to be applied on the non-magnetic substrate together with the ferromagnetic powder includes acrylic resin, vinyl chloride resin, vinyl acetate resin, polystyrene, polyurethane resin, polyester resin, polycarbonate resin, epoxy resin, melamine resin, polyamide resin, etc. resin, polybutadiene resin, polyacrylonitrile resin, phenolic resin,
Examples include polyvinyl butyral resin, phenoxy resin, urea resin, furan resin, and copolymer resins and modified resins thereof. In addition, in order to improve the dispersibility of magnetic powder, sulfonic acid groups,
Phosphoric acid group, carboxyl group, or these alkali metal bases or alkaline earth metal bases, or amino groups,
Resins into which hydrophilic groups such as alkylamino groups, ammonium bases, alkylammonium bases, and hydroxyl groups have been introduced may also be used.

When using these binder components, appropriate curing agents, curing accelerators, catalysts, etc. are used depending on the type.
A polyisocyanate compound having two or more functionalities is preferred as the curing agent. Furthermore, a method may be adopted in which a resin into which unsaturated double bonds are introduced is used as a binder component and is cured with ultraviolet rays or electron beams.

In the mother tape of the present invention, the blending ratio of the hexagonal ferrite powder and the binder component is 10 parts of the ferromagnetic powder.
The binder component shall be blended at a ratio of 4 to 15 parts by weight relative to 0 parts by weight. On the other hand, a slave tape using this mother tape as a transfer tape has a ferromagnetic powder of 100%.
Preferably, the magnetic recording layer is formed by blending a binder component in a range of 10 to 20 parts by weight.

In addition to the above-mentioned components, the magnetic recording layer of the mother tape according to the present invention may contain lubricants, dispersants, abrasives,
Or antistatic agents such as carbon black, etc.
The volume content of the ferromagnetic powder in the magnetic recording layer is 40%.
They may be added and blended as appropriate so as not to fall below. Usually, the amount of these additives added is 2 parts by weight or less for lubricant, 2 parts by weight or less for dispersant, 6 parts by weight or less for abrasive, and 2 parts by weight for antistatic agent, per 100 parts by weight of ferromagnetic powder. It is preferable to keep the amount added to the minimum necessary amount.

The lubricant used here has a carbon number of 14 to 40.
Dispersants include lecithin, anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants. and so on. In addition, as abrasives, TlO2, Cr2O3, A/203
, SjC5Zr02 and the like having a Mohs hardness of 5 or more are preferably used.

The mother tape for contact magnetic transfer according to the present invention is generally manufactured as follows. That is, the above-mentioned ferromagnetic powder and binder components, and the various additives as necessary, are mixed into toluene, xylene, tuclohexane, methyl ethyl ketone, methyl isobutyl ketone, nitropropane,
A magnetic paint is first prepared by thoroughly mixing and dispersing it with a solvent such as isopropyl alcohol.

Next, after filtering this magnetic paint,
After adding a hardening agent such as a magnetic compound and coating it on a non-magnetic substrate such as a polyester film or a polyamide film, the magnetic coating film is sequentially subjected to an orientation treatment, a drying treatment, a smoothing treatment using a calendar, etc. It is obtained by

In such a manufacturing process, for example, by controlling the strength of the vertical alignment magnetic field, coating speed, drying conditions, etc. in the coating and drying process, or by controlling pressure, temperature, speed, etc. in the calendering process, A mother tape having a magnetic recording layer with a high volume content of ferromagnetic powder and good characteristics can be produced.

Next, specific examples of the present invention will be described.

Examples 1 to 5 Average particle size 0.05 μm, plate ratio 3.5, specific surface area 3]r
rf/g, coercive force Hc 2400 Oe, temperature coefficient of coercive force Hc 5.3 Oe/'C Ba-ferrite powder 10
0 parts by weight, poly-11 urethane resin was added from 4 parts by weight to 1 part by weight so that the volume content of the Ba-ferrite powder in the magnetic recording layer was <62 to 40% as shown in Table 1.
Chromium oxide (average particle size 03 μrn) was added to each of these formulations by changing the amount in 5 steps up to 6 parts by weight.
Add 2 parts by weight of palmitic acid, add 2 parts by weight of methyl ethyl ketone/methyl isobutyl ketone/toluene, and grind with a sand grinder.
Five types of magnetic paints were prepared by time mixing and dispersion.

Each of the magnetic paints obtained above was filtered through a 3 μm filter, 3 parts by weight of curing agent C-3041 (trade name 9 Nippon Polyurethane Co., Ltd. TA) was added thereto, and coated to a thickness of 9.1 μm using a reverse coater. Each layer was applied onto the surface of a polyester film, vertically oriented in a BKOe magnetic field, and then dried.After that, surface smoothing treatment using a calender and slitting were performed in order to reduce the thickness to 3.
3,81 m+w width D with μm magnetic recording layer
Each mother tape for AT was produced.

[Example 6 ~] [] In place of the Ba-ferrite powder used in Examples ~5 above, Ba-ferrite powders with slightly different average particle diameters, plate ratios, and coercive forces were used, and the others were Mother tapes were produced in the same manner as in Example 3 above.

Example 11.12 In place of the Ba-ferrite powder used in Examples 1 to 5 above, Ba-ferrite powder in which part of Fe was replaced with Sn was used, and the other conditions were the same as in Example 3. Mother tapes each having a magnetic recording layer having a different temperature coefficient of coercive force He from those in Examples 1 to 10 were prepared.

Comparative Example 1.2 The amount of polyurethane resin was 20 parts by weight (Comparative Example 1)
and 30 parts by weight (Comparative Example 2), in the same manner as in Example 1, a mother tape having a different volume content of magnetic powder from each of the above Examples was produced.

Comparative Example 3.4 A mother tape was used under the same conditions as in the above Examples, except that Ba-ferrite powder with a different plate ratio was used, and the amount of polyurethane resin was the same as in Example 5. Created.

Next, for each of the mother tapes according to these Examples and Comparative Examples, the volume content of the magnetic powder, the coercive force Hc of the tape magnetic recording layer, the temperature coefficient of the coercive force He, and the vertical squareness ratio were measured. The transfer efficiency (transfer output of the obtained slave tape) by contact magnetic transfer and the block error rate when the transferred pre-DA recording signal was reproduced were measured.

Note that the transfer efficiency by contact magnetic transfer was determined as follows. That is, each mother tape has a DAT
Using mirror master machine (relative speed 3.133rn
/sec), a frequency of 4.7M1 (a square wave of z was recorded in advance as a mirror pattern, and this mother tape and a slave tape obtained in Example 14, which will be described later, were brought into close contact with each other using an air pressure bonding method, and the transfer output was increased to the maximum. The signal magnetic field was transferred by applying a bias magnetic field so that , DAT during playback
Table 1 shows the block error rate measured using an error changer.

(Left below) Magnetic powder Magnetic powder particle size/volume plate thickness ratio Content rate (%) 1 3.5 [i2 2 3.5 56 3 3.5 51 4 3.5 45 Actual 5 3.5 40 Implementation 8 3. ．． 1 52 Example 7 3.4 51 g 4J 49 9 5.7 47 10 3.5 51 +1 3.3 52 12 3.2 52 Ratio 1 3.5 38 Comparison 2 3.5 30 Example 3 2.7 42 4 7.4 34 Mother tape He (Oe) Table 1 Mother Mother tape Chee C Vertical Temperature coefficient squareness ratio (Oe/”C) 0.75 5.3 0.77 5.3 0.75 53 0.74 5. 3 0.74 5.3 0.70 5.1 0.78 5.2 0.79 5.2 0.83 5.4 0.74 5.3 0.73 4.1 0.71 3.4 0 .76 5.3 0.76 5.3 0.63 5.0 0.84 4.4 Slave tape transfer output (dB) +24 +1.8 +1.2 +06 +0.2 +0.9 +1.6 +11 +0. 8 +03 0.2 =1,6 3.3 Slave tape block error rate 0.9 cut 0-4 1,.2XlO-'1.4X10-'2.11X10"4.8X10-' t, gxto-' 2 .6X10-'2.5XIO-'2.1X10-'4.1XIO-'4.8XIO-'5.6XIO-'4.4XIO-' 3.2XIO゛2 2.5XIO-'9.6X10' Examples 13~]8 Ba-ferrite powder having the same shape as the Ba-ferrite powder used in Example 3, but with a different amount of Co-Ti substitution and only a different coercive force He, was used in the same manner as in Example 3. Slave tapes were prepared for each.

Next, the coercive force He of the tape magnetic recording layer, the temperature coefficient of the coercive force He, and the perpendicular squareness ratio of the obtained slave tape were measured. Further, contact magnetic transfer was performed at 70°C using the masser tape obtained in Example 7,
Table 2 shows the results of measuring the transfer characteristics (transfer output and block error rate during signal reproduction) of the transferred slave tape.

Comparative Examples 5 to 7 In the case of Example 5, except that Ba-ferrite powder with different temperature coefficients of coercive force lie and coercive force He was used, the resin compounding amount and composition were the same, and the orientation magnetic field strength was A slave tape was prepared by subjecting the tape to vertical alignment using 2 KOe. Also, in the same way, the magnetic field strength is 3 KO
A mother table was prepared by performing vertical alignment in step e.

Next, the mother tape and slave tape thus obtained were combined, contact magnetic transfer was performed at 70° C., and the transfer output and block error rate of the transferred slave tape were measured. The measurement results are shown in Table 2. (Left below) Table 2 Slave Slave Motherte Slave Motherte
Slave Blotte One C Tape - Butare Chi'
;Qle -':]c tape ri (Oe)
Right angle ratio Right angle ratio Temperature coefficient Temperature coefficient Transfer output error (Oe/'C) (Qe/'C)
(dB) Rate actual 13 540 0.61
1 0.78 3. :l 5.2 +0
．． 6 2. IXIF'S147110 0.65
/3.4 〃+1.71. ．． 9XIO-
'Example 15 1040 0.71 3.
4 〃+2.1 1. lX10-'18 99
0 0.72 / 1.4
/l+1.9 (1,8xlo-'171230
0.75 〃 -1,8
〃 +2.61.2XIO-'181080
0.73 〃-OJ l+2.2
0.7×IO-' ratio 5770 0.48 0,61
3.4 5.0 -0.54.7XIO-'Comparison 6
g20 0,49 0,64 5.4 -
1.2 -1.8 7.9 mowing o-1 example 710 [io
0.55 0,58 5.2 -1.2 -2.
9 1. lXl0'Magnetic powder particle size Magnetic powder specific surface area Example 19 0.045μm 37rrf/g〆-
200,046μm 44i/g Comparative example 8007μr
n 23M/g Table 3 Slave tape relative (S/N) +0.8 dB ÷1.6dB 0.9dB Slave tape block error rate 1.2XIO-' 89 cut 0-5 3.3XIO-' Example 19 .20, Comparative Example 8 Average particle size 0.06 μm, platelet ratio 3.6, specific surface area 26 Ho/g, coercive force Hc 2350 Oe, temperature coefficient of coercive force He 32 Oe/''C to 100 parts by weight of Ba-ferrite powder To this, 12 parts by weight of polyurethane resin UR-8300 (manufactured by Toyobo Co., Ltd.), 1.5 parts by weight of chromium oxide, 2 parts by weight of stearic acid, and a 12-part mixed solution of tsucrohexanone/methyl ethyl ketone were added and mixed to give a solid content ratio of 40%. Mix and disperse the adjusted mixture for 2 hours using a sand grinder.
Various magnetic paints were prepared.

Next, each of the magnetic paints obtained above was filtered through a 3 μm filter, and 2 single parts of curing agent C-3041 were added.
It was coated to a thickness of 3 μm on the surface of a 91 μm thick polyester film using a reverse coater.

Thereafter, the tape was vertically aligned in a magnetic field of 6 KOe, dried, calendered, and slit to have a width of 381 mm to produce a mother tape.

On the other hand, as shown in Table 3, the average grain size is 0.045 μm, the plate ratio is 3.4, the specific surface area is 37rd/g, and the coercive force is 1c67.
0 Oe Ba-ferrite powder (Example 19), average particle size 0046 μ, plate ratio 37, specific surface area 44rd/g, coercive force Hc 750 Oe Ba-ferrite powder (Example 2)
0), ■ Using Ba-ferrite powder (Comparative Example 8) with an average particle size of 0.07 μm, a plate ratio of 33, a specific surface area of 23 I/g, and a coercive force of 11 c Oc, the composition was the same as that of the above-mentioned Mazatar tape, and the same composition was used. Each slave tape was manufactured using a similar process.

A frequency of 4゜7MH was applied to the mother tapes obtained above.
After recording Z rectangular waves in advance as mirror patterns, these were brought into close contact with the corresponding slave tapes, and contact magnetic transfer was performed by applying a perpendicular bias magnetic field.

The S of the thus transferred slave tape was measured and compared with the S of the original mother tape (expressed as OdB). Further, Table 3 shows the results of measuring the block error rate of the slave table when reproducing the recorded signal.

From this table, it can be seen that in Example 9.20, the magnetic powder of the slave tape has a smaller particle size than the magnetic powder of the master tape, so the S/N of the slave tape is lower than that of the master tape. It can be seen that the S/N is significantly improved.

[Effects of the Invention] As is clear from the above description, the mother magnetic recording medium according to the present invention has good transfer efficiency and can provide sufficient transfer output to the slave tape. Therefore, the error rate during reproduction after transfer is low, and high-quality copies of digital or analog signals can be obtained with good reproducibility.

Applicant: Toshiba Corporation Agent: Patent Attorney Su Yamasa

Claims (1)

[Claims] In a mother magnetic recording medium in which a magnetic recording layer is provided by applying hexagonal ferrite powder together with a binder component onto a non-magnetic substrate, the hexagonal ferrite powder in the magnetic recording layer is: A mother magnetic recording medium characterized by having a plate ratio of 3 to 6, a coercive force of 1500 Oe or more, and a volume content of 40% or more.