JP2002237027A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance dimensional stability of a magnetic recording medium. SOLUTION: In the magnetic recording medium having a belt-like non- magnetic supporting body consisting of a polyester based plastic film, a lower layer formed on a principal surface of the non-magnetic supporting body and a magnetic layer formed on the lower layer, a reinforcing film consisting of metal, semi-metal, alloy, oxide of them or composite of them and having 20-1,000 nm thickness is formed on at least one surface of the non-magnetic supporting body and the non-magnetic supporting body wherein the reinforcing film is formed has <=0.5% coefficient of thermal shrinkage at 100 deg.C for 30 min in both longitudinal and lateral directions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium in which signals are linearly digitally recorded in a longitudinal direction by a fixed head such as a digital linear tape (DLT).
More specifically, the present invention relates to a high-density magnetic recording medium having excellent dimensional stability and high reliability.

[0002]

2. Description of the Related Art In a digital magnetic recording medium of a type in which signals are recorded / reproduced by sliding a magnetic head on the surface of a medium, a high recording density can be attained by reducing a track width and a recording wavelength. It is planned. In such a magnetic recording medium, the magnetic layer tends to be thin in order to reduce the self-demagnetization loss at the time of recording and the thickness loss at the time of reproduction, so that the magnetic energy must be reduced. In order to solve these problems, the coercive force (H
There is a tendency to increase the saturation magnetic flux density (Bs) in order to increase c) and increase the magnetic energy.

However, when the density of a magnetic recording medium is increased based on the above-described design concept, it is difficult to secure high electromagnetic conversion characteristics because the magnetic layer becomes thinner and thinner. Therefore, in recent years, it has been proposed that it is effective to use a magnetoresistive head (hereinafter, referred to as an MR head) as a recording signal reproducing head in order to achieve a higher recording density of a magnetic recording medium. I have.

[0004]

On the other hand, as the track of the magnetic recording medium becomes narrower, the influence of the dimensional change increases. Since the polyester plastic film is used as the non-magnetic support, the dimensional change of the magnetic recording medium over time or depending on the storage environment due to the strain inherent in the non-magnetic support and the strain accumulated during the magnetic tape manufacturing process May occur. Some of the recorded data may not be able to be read due to dimensional changes,
This effect is greater as the track becomes narrower. Therefore, dimensional stability is very important to achieve a high recording density.

Usually, polyethylene terephthalate (PET) and polyethylene-2,6-naphthalene dicarboxylate (PE) are used as the non-magnetic support of the magnetic recording medium.
Non-magnetic supports such as polyester-based plastic films such as N) are used, but polyamide films are used in some thin-film high-density recording media requiring high strength and dimensional stability.

[0006] However, since the amount of the polyamide film currently produced is much smaller than that of the conventional polyester film, there are restrictions such as a limit on the quantity expansion and a high price. On the other hand, if PET or PEN is used as it is, the dimensional stability is low, and there is a limit in increasing the track density.

The present invention has been proposed in view of such conventional circumstances, and has as its object to provide a magnetic recording medium with improved dimensional stability.

[0008]

The magnetic recording medium of the present invention comprises a belt-shaped non-magnetic support made of a polyester plastic film, a lower layer formed on one main surface of the non-magnetic support, A magnetic recording medium having a magnetic layer formed thereon, wherein at least one surface of the non-magnetic support has a reinforcing film made of a metal, a metalloid, an alloy, or an oxide or a composite thereof having a thickness of 20 nm or more. 1000n
m in the longitudinal direction and the width direction of the nonmagnetic support on which the reinforcing film is formed,
The heat shrinkage rate in 30 minutes is 0.5% or less.

In the magnetic recording medium according to the present invention as described above, a reinforcing film made of a metal, metalloid, alloy, or an oxide or composite thereof is formed on at least one surface of the non-magnetic support. Since the heat shrinkage rate at 100 ° C. for 30 minutes in both the longitudinal direction and the width direction of the non-magnetic support on which the reinforcing film is formed is 0.5% or less after storage, In this case, the shrinkage and deformation of the nonmagnetic support are suppressed, and the dimensional stability is excellent.

[0010]

Embodiments of the present invention will be described below.

FIG. 1 shows a configuration example of a magnetic recording medium according to the present invention. The magnetic recording medium 1 is provided with a magnetic or non-magnetic lower layer 3 on one main surface 2a of a strip-shaped non-magnetic support 2, and a magnetic layer as an uppermost layer (hereinafter referred to as an upper magnetic layer) on the lower layer 3. 4) are provided. A back coat layer 5 is provided on the other main surface 2b of the non-magnetic support 2.

The non-magnetic support 2 is made of a polyester plastic film and has a thickness of 2 μm to 10 μm.
Range.

Here, as the polyester-based plastic, polyethylene terephthalate (PET), polyethylene-2,6-naphthalene dicarboxylate (PE)
N), polytetramethylene terephthalate, poly-1,
4-cycloheximethylene terephthalate, polyethylene-p-oxybenzoate, and the like. Particularly, PET and PEN are preferable. These polyesters may be homopolyesters or copolyesters.

The polyester plastic film may be a single layer or a laminated film of two or more layers. Further, an adhesive layer is provided on the surface of the non-magnetic support 2,
The adhesiveness with the lower layer 3 and the back coat layer 5 may be enhanced.

Further, the durability and running property of the magnetic recording medium 1,
In order to improve the handling at the time of tape formation, particles may be included in the film. As the particles,
Examples thereof include, but are not limited to, calcium carbonate, silica, alumina, and polystyrene.

In the magnetic recording medium 1 according to the present invention, a reinforcing film 6 made of a metal material is formed on at least one surface of the nonmagnetic support 2.

The reinforcing film 6 is made of a metal material selected from metals, metalloids or alloys, and oxides or composites thereof. Specifically, Al, Cu, Zn, Sn, Ni,
Ag, Co, Fe, Mn, Cr and other metals, Si, G
e, As, Sc, Sb, and other semimetals. Alloys of these metals and metalloids include Fe-Co, Fe
-Ni, Co-Ni, Fe-Co-Ni, Fe-Cu,
Co-Cu, Co-Au, Co-Y, Co-La, Co
-Pr, Co-Gd, Co-Sm, Co-Pt, Ni-
Cu, Mn-Bi, Mn-Sb, Mn-Al, Fe-C
r, Co-Cr, Ni-Cr, Fe-Co-Cr, Ni
—Co—Cr and the like. Also, these metals,
Oxides of semimetals or alloys can be easily obtained, for example, by introducing oxygen gas during vapor deposition. Also, these metals,
As a composite of a metalloid and a composite metal, Fe-Si-O,
Si-C, Si-N, Cu-Al-O, Si-NO,
Si-CO is mentioned.

The method of forming the reinforcing film 6 is not limited.
A vacuum evaporation method is generally used, and other methods such as a sputtering method and an ion plating method can be used.

The thickness of the reinforcing film 6 is preferably in the range from 20 nm to 1000 nm. If the thickness of the reinforcing film 6 is less than 20 nm, the thickness is insufficient, so that the thermal shrinkage of the nonmagnetic support 2 cannot be suppressed.
On the other hand, when the thickness of the reinforcing film 6 exceeds 1000 nm, the thermal shrinkage of the non-magnetic support 2 can be almost completely suppressed, but on the other hand, the curl becomes large, and the magnetic head may not be easily shrunk. The hit will be insufficient. Therefore, by setting the thickness of the reinforcing film 6 in the range of 20 nm or more and 1000 nm or less, the thermal shrinkage of the nonmagnetic support 2 can be sufficiently suppressed. The more preferable thickness of the reinforcing film 6 is in the range of 100 nm to 500 nm.

Although the reinforcing film 6 is provided on both surfaces of the nonmagnetic support 2, it is provided on one of the main surface 2a on which the upper magnetic layer 4 is provided or the other main surface 2b on which the back coat layer 5 is provided. Although it may be provided, the magnetic recording medium 1 is preferably provided on both sides for the purpose of reducing the curl.
The reinforcing film 6 may be a single layer or a multilayer.

The heat shrinkage of the nonmagnetic support 2 on which the reinforcing film 6 is formed at 100 ° C. for 30 minutes is 0.5% or less in both the longitudinal direction and the width direction. preferable. If the heat shrinkage exceeds 0.5%, the dimensional change after storage for a certain period of time after reading the data becomes large, so that a track shift occurs and a part of the data becomes unreadable or the tape width changes. Data cannot be read at all. Therefore, by setting the heat shrinkage of the non-magnetic support 2 to 0.5% or less, dimensional change can be suppressed even after storage, and data reading failure due to track shift, tape width change, and the like can be prevented. it can.

The upper magnetic layer 4 is mainly formed of a ferromagnetic powder and a binder, and is formed by applying and drying a coating material in which these components are dispersed and dissolved in a solvent.

As the ferromagnetic powder, any of conventionally known ferromagnetic powders can be used and is not limited at all. For example, Co-containing γ-Fe ₂ O ₃ , Fe-based acicular magnetic powder, B
Examples include plate-like magnetic powder such as a-Ferrite, and iron nitride. Further, even if an appropriate amount of a metal element such as Al, Si, Y, P, or B used for the purpose of preventing sintering during reduction or maintaining the shape is included, the effect of the present invention is not impaired. Also, the shape is not particularly limited, such as a needle shape and a plate shape.

As the binder, any of the binders used in ordinary coating type magnetic recording media can be used. Specific examples include organic binders such as vinyl copolymers, polyester polyurethanes, polycarbonate polyurethanes, and nitrocellulose.

Further, in addition to the ferromagnetic powder and the binder, additives such as a lubricant, an abrasive, and an antistatic agent may be added to the upper magnetic layer 4 as needed. Any of conventionally known materials can be used as these additives, and there is no particular limitation.

The back coat layer 5 provided on the other main surface 2b of the non-magnetic support 2 is formed by applying a known back coat paint containing carbon black, a binder and the like onto the non-magnetic support 2 and drying it. Is formed.

In the magnetic recording medium 1 according to the present invention having the above-described structure, a metal, a metalloid, an alloy, an oxide or a composite thereof is formed on at least one surface of a non-magnetic support 2 made of a polyester plastic film. A reinforcing film 6 made of a material having a thickness of 20 nm to 1000 nm;
Since the non-magnetic support 2 on which the reinforcing film 6 is formed has a heat shrinkage of 0.5% or less in both the longitudinal direction and the width direction at 100 ° C. for 30 minutes, the dimensional stability is excellent.
It has high reliability and is suitable for high recording density.

For example, when recording / reproducing the magnetic recording medium 1 of the present invention by a fixed head system, the track width is preferably 30 μm or less, more preferably 2 μm to 30 μm.
And more preferably in the range of 2 μm to 10 μm. Further, the linear recording density is preferably 100 k
FCl or more, more preferably 100 kFCl to 250 k
FCl range, more preferably 150 kFCl to 25
It can be in the range of 0 kFCl.

When the magnetic recording medium 1 is used in a recording / reproducing system in which a recording signal is reproduced by a magnetoresistive magnetic head, the effect of the present invention can be sufficiently exhibited, and in particular, It is suitable.

[0030]

Next, examples and comparative examples performed to confirm the effects of the present invention will be described. In the following description, specific numerical values are described, but it goes without saying that the present invention is not limited to these examples.

Example 1 First, on both sides of a polyethylene terephthalate film having a thickness of 6 μm as a nonmagnetic support, Al was deposited to a thickness of 120 nm to form an Al-reinforced film having a total thickness of 240 nm. . The deposition conditions at this time were a maximum incident angle of 60 °, a film running speed of 1.5 m / min, an electron gun power of 10 kw, and an oxygen gas flow rate of 10 sccm.

Next, in the following formulation, a powder such as an abrasive was put into a planetary mixer together with a binder and a part of a solvent and preliminarily mixed to prepare a mixture. Next, this was subjected to a high-shear dispersion treatment with a biaxial continuous stiffening device. After adding a solvent to the mixture and performing a dilution treatment with a stirrer such as a dissolver, and then performing a fine dispersion treatment with a sand mill, the solvent is added to adjust the viscosity appropriately to obtain an absolute filtration accuracy of 1.
Filtration was performed using a μm filtration filter. Thereafter, a curing agent was added to obtain a lower layer paint.

Lower layer coating composition Acicular α-Fe ₂ O ₃ (average particle diameter 100 μm) 100 parts α-alumina (abrasive, average particle diameter 70 nm) 6 parts Carbon black (average particle diameter 17 nm) 15 parts Vinyl chloride 14 parts of copolymer (binder) [MR104 made by Nippon Zeon] 10 parts of polyurethane resin (binder) [UR8300 made by Toyobo] 2 parts of stearic acid 2 parts of polyisocyanate (curing agent) [coronate HX made by Nippon Polyurethane Industry] methyl ethyl ketone ( Solvent) 117 parts Toluene (solvent) 117 parts Cyclohexanone (solvent) 39 parts In the following formulation, powders such as ferromagnetic powder and abrasives are put into a planetary mixer together with a binder and a part of a solvent. Premixing was performed to produce a mixture.
Next, this was subjected to a high-shear dispersion treatment with a biaxial continuous stiffening device. After adding a solvent to the mixture and performing a dilution treatment with a stirrer such as a dissolver, and then performing a fine dispersion treatment using a sand mill, the solvent is added to adjust the viscosity appropriately, and a filtration filter having an absolute filtration accuracy of 1 μm is used. Filtration was performed. Thereafter, a curing agent was added to obtain a paint for the upper magnetic layer.

Coating composition of upper magnetic layer Acicular ferromagnetic metal powder 100 parts α-alumina (polishing agent, average particle diameter 70 nm) 12 parts Vinyl chloride copolymer (binder) 10 parts [Nippon Zeon MR104] Polyurethane Resin (binder) 7 parts [Toyobo UR8300] Polyisocyanate (curing agent) 1 part [Nippon Polyurethane Industry Coronate HX] Methyl ethyl ketone (solvent) 221 parts Toluene (solvent) 221 parts Cyclohexanone (solvent) 73 parts Back coating The coating material TB6001 was sufficiently stirred with a dissolver, and then filtered using a filtration filter having an absolute filtration accuracy of 1 μm, and a curing agent was added to obtain a coating for a back coat layer.

100 parts of coating composition for back coat layer TB6001 100 parts [Toyo Ink] Polyisocyanate (curing agent) 2 parts [Coronate HX manufactured by Nippon Polyurethane Industry Co., Ltd.] Next, a lower layer is formed on the non-magnetic support on which the reinforcing film is formed. The paint for the upper layer and the paint for the upper magnetic layer are simultaneously coated in a wet-on-wet manner by a die coater so that the dry thicknesses of the lower layer and the upper magnetic layer are 1.5 μm and 0.13 μm, respectively. The respective coating films were formed.

Then, while these coating films were in a wet state, they were passed through a solenoid having a magnetic force of 0.5 T, subjected to a magnetic field orientation treatment and a drying treatment in the longitudinal direction, and wound up. Next, at a temperature of 80 ° C. and a speed of 80 m / min using a seven-stage calender
Per minute. Thereafter, a backcoat paint was applied on the back surface of the nonmagnetic support to a dry thickness of 0.6 μm.
And dried and wound up.

Finally, 12.7 mm (1
/ 2 inch) and wound around a cartridge with a loader to obtain a magnetic tape.

Example 2 2 μm thick nonmagnetic support
m, except that a polyethylene-2,6-naphthalene dicarboxylate film (PEN film) was used.
A magnetic tape was produced in the same manner as in Example 1.

Example 3 One Side (Back Side) of Film
Then, Al is deposited to a thickness of 100 nm to a total thickness of 200 nm.
A magnetic tape was manufactured in the same manner as in Example 1 except that an Al-reinforced film having a thickness of nm was formed.

Example 4 A nonmagnetic support having a thickness of 10
μm PET film, on both sides of the film,
Al is deposited to a thickness of 100 nm each to give a total thickness of 2
Example 1 except that a 00 nm Al-enhanced film was formed.
A magnetic tape was produced in the same manner as described above.

Example 5 Al was vapor-deposited on both sides of a film to a thickness of 500 nm to give a total thickness of 1000 n.
A magnetic tape was manufactured in the same manner as in Example 1 except that an m-thick Al reinforcing film was formed.

Example 6 Example ₂ was repeated except that SiO ₂ was used instead of Al, and SiO ₂ was deposited on both surfaces of the film to a thickness of 120 nm to form a reinforced film having a total thickness of 240 nm. In the same manner as in Example 1, a magnetic tape was produced.

<Example 7> Cr was used instead of Al.
A magnetic tape was produced in the same manner as in Example 1, except that Cr was deposited on both surfaces of the film to a thickness of 120 nm to form a 240 nm-thick reinforcing film.

Example 8 A film having a total thickness of 20 nm was formed on both surfaces of a film by depositing Al to a thickness of 10 nm.
A magnetic tape was produced in the same manner as in Example 1 except that a 1-strengthened film was formed.

Example 9 One side (back side) of a film
Then, Al is deposited to a thickness of 1000 nm to a total thickness of 10 nm.
Example 1 except that a 00 nm Al-enhanced film was formed.
A magnetic tape was produced in the same manner as described above.

Comparative Example 1 A magnetic tape was manufactured in the same manner as in Example 1 except that the Al-reinforced film was not formed.

<Comparative Example 2> 2 μm thick nonmagnetic support
A magnetic tape was produced in the same manner as in Example 2 except that an m-thick PEN film was used and an Al-reinforced film was not formed on the film.

Comparative Example 3 A nonmagnetic support having a thickness of 10
A magnetic tape was produced in the same manner as in Example 1 except that a μm PET film was used and no Al-reinforced film was formed on the film.

Comparative Example 4 A nonmagnetic support having a thickness of 10
μm PET film, on both sides of the film,
Al is deposited to a thickness of 5 nm each to a total thickness of 10 n.
A magnetic tape was manufactured in the same manner as in Example 1 except that an m-thick Al reinforcing film was formed.

Comparative Example 5 A nonmagnetic support having a thickness of 10
A film was formed in the same manner as in Example 1, except that a PET film having a thickness of 120 μm was used to deposit a 1200 nm-thick Al film on one side (back surface) of the film using a μm PET film. A magnetic tape was produced.

Then, the magnetic tape produced as described above was subjected to an evaluation test for storage stability.

First, a modified DLT7000 drive is provided with a recording head (Metal In Gap, gap 0.15).
μm, 1.8T) and MR head for reproducing head (optimum B
rt: 0.0035 T · μm). These heads are fixed heads. Using this drive, a magnetic tape has a track width of 25 μm and a linear recording density of 100 k.
A signal was recorded in FCl and stored for 100 hours in an atmosphere of 40 ° C. and 80% RH. Then, the data was reproduced, and the preservability of the tape was evaluated from the reproduction state of the data.

The evaluation was ○ when the tape was reproduced normally without any track deviation on the tape. In addition, a case where there was no abnormality in the tape width, but some parts were unreadable, was evaluated as Δ. When the tape width was changed and reading was impossible, it was evaluated as x.

Further, the heat shrinkage of the tape was measured.

The method for measuring the heat shrinkage rate is JIS-C2318.
Followed. The sample size in this case was 10 mm in width and 200 mm in mark interval. The measurement conditions were as follows: temperature was 100 ° C., processing time was 30 minutes,
No load was applied.

Then, the heat shrinkage of the tape at 100 ° C. was determined by the following equation.

Heat shrinkage (%) = {(L ₀ −L) / L ₀ } × 100 In the above formula, L ₀ is a reference line interval before the heat treatment, and L is
This is the interval between marked lines after the heat treatment.

With respect to the magnetic tapes of Examples 1 to 9 and Comparative Examples 1 to 5, the results of evaluation of the storage stability and the heat shrinkage are shown in Table 1.

[0059]

[Table 1]

From Table 1, it can be seen that Examples 1 to 3 in which a reinforced film was formed on a non-magnetic support made of a polyester film and Comparative Examples 1 to 3 in which no reinforced film was formed.
In Comparative Examples 1 to 3, since the heat shrinkage of the non-magnetic support was large in Comparative Examples 1 to 3, data could not be read due to deformation of the tape width or track deviation after storage. On the other hand, in Examples 1 to 3, the heat shrinkage of the non-magnetic support was suppressed, the tape width was not deformed or the track was not shifted even after storage, and data could be read well.

In Comparative Example 4, the thickness of the Al-reinforced film was 10 nm.
However, since the thickness was insufficient, the thermal shrinkage of the nonmagnetic support was so large that data could not be read due to track deviation.

In Comparative Example 5, the thickness of the Al reinforcing film formed on the back surface side was 1200 nm. In this case, the heat shrinkage can be suppressed almost perfectly, but on the other hand, the curl becomes large and the contact with the head cannot be obtained, so that the recording / reproduction becomes impossible.

From the above results, a reinforcing film made of a metal, a metalloid, an alloy, or an oxide or a composite thereof has a total thickness of 20 nm to 1000 nm on at least one surface of the nonmagnetic support made of a polyester plastic film.
The dimensional stability is excellent by setting the heat shrinkage at 100 ° C. for 30 minutes in the longitudinal direction and the width direction of the non-magnetic support having the reinforcing film formed thereon in the range of 0.5% or less to 0.5% or less. It was found that a highly reliable magnetic tape with high recording density could be obtained.

[0064]

According to the present invention, a reinforcing film made of a metal material selected from metals, metalloids and alloys and oxides and composites thereof is provided on at least one surface of a non-magnetic support made of a polyester plastic film. Since the heat shrinkage of the formed non-magnetic support after forming the reinforcing film at 100 ° C. for 30 minutes is suppressed to 0.5% or less, a magnetic recording medium having excellent dimensional stability and high reliability is realized. be able to.

Such a magnetic recording medium has, for example, a track width of 30 μm or less and a linear density of 1
It is particularly suitable when used in a recording / reproducing system in which recording and / or reproduction is performed by a fixed head method such as 00 kFCl or more, or a recording / reproducing system in which a recording signal is reproduced by a magnetoresistive head, A higher recording density can be realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration example of a magnetic recording medium according to the present invention.

[Explanation of symbols]

1 magnetic recording medium, 2 non-magnetic support, 3 lower layer,
4 Upper magnetic layer, 5 Back coat layer, 6 Reinforcing film

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) G11B 5/78 G11B 5/78 F term (reference) 4F100 AA17B AA17C AA33B AA33C AB01B AB01C AB10 AK41A AK42 BA02 BA03 BA07 BA10A BA10B BA10C EH66 GB41 JA03 JL04 YY00B YY00C 5D006 CA01 CA05 CB01 CB07 CC01 CC03

Claims (3)

[Claims] 1. A magnetic recording comprising: a strip-shaped non-magnetic support made of a polyester-based plastic film; a lower layer formed on one main surface of the non-magnetic support; and a magnetic layer formed on the lower layer. In the medium, on at least one surface of the nonmagnetic support, a reinforced film made of a metal, a metalloid, an alloy, or an oxide or a composite thereof is formed with a thickness of 20 nm to 1000 nm, and the reinforced film is formed. The heat shrinkage at 100 ° C. for 30 minutes in the longitudinal direction and the width direction of the non-magnetic support was
A magnetic recording medium, wherein both are 0.5% or less. 2. A recording / reproducing system in which recording and / or reproducing is performed by a fixed head system having a track width of 30 μm or less and a linear density of 100 kFCl or more. The magnetic recording medium according to the above. 3. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is used in a recording / reproducing system in which an information signal is reproduced by a magnetoresistive head.