JPH1049852A - Magnetic recording media - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium which is hard to be bent, wrinkled, and deformed, has good compatibility with conventional magnetic recording media, has good electromagnetic conversion characteristics, and has a running property, and is capable of long-time recording. Provide media. SOLUTION: In a magnetic recording medium 1 in which a magnetic layer 3 is formed on a non-magnetic support 2, the non-magnetic support 2 is an aromatic polyamide film, and the thickness of the non-magnetic support 2 is 1
0 μm or less, Young's modulus in the vertical direction is 1000 kg / mm ²
As described above, the configuration is such that the Young's modulus in the width direction is 1300 kg / mm ² or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic recording medium having a magnetic layer formed on a non-magnetic support.

[0002]

2. Description of the Related Art In recent years, as a support for a magnetic recording medium,
Mainly polyethylene terephthalate (PET) is used. In particular, a polyethylene terephthalate film having a thickness of about 7 to 10 μm is used for a video tape for home video, for example, an 8 mm tape, and a thickness of about 1 to 10 μm is used for a VHS tape.
A polyethylene terephthalate film of about 0 to 16 μm is used.

[0003]

In order to use these video tapes for home video for a long time, it has been considered to reduce the thickness of the support film to about 2/3. It is conceivable to use a re-stretched polyethylene terephthalate film for the purpose of increasing the strength or Young's modulus in the transverse or transverse direction. However, in practice, it has been found that even with the polyethylene terephthalate film treated in this way, a trouble occurs on a video tape recorder (VTR). For example, when using a film having a high strength or Young's modulus in the longitudinal direction, wrinkles and breaks in the width direction are less likely to occur,
As the strength in the width direction and the Young's modulus are increased, the strength and the Young's modulus in the length direction are reduced, and the tape is likely to be deformed during fast-forwarding and rewinding.

On the other hand, a magnetic recording medium in which the magnetic layer is formed of a ferromagnetic metal thin film is suitable for a long-time magnetic recording medium because the magnetic layer is as thin as about 0.1 to 0.3 μm. Because the magnetic layer is thin, it is susceptible to the surface properties of the non-magnetic support underneath, and the surface state of the non-magnetic support, that is, the unevenness of the surface of the non-magnetic support is directly expressed as unevenness on the surface of the magnetic layer. There is a drawback that causes noise. Therefore, from the viewpoint of reducing noise, it is preferable that the surface state of the nonmagnetic support is as smooth as possible.

Further, from the viewpoint of electromagnetic conversion characteristics,
The surface of the non-magnetic support is required to be flat.

On the other hand, from the viewpoint of handling such as unwinding and winding of a film, it is required that the surface of the film is rough. When the film is flat, the film-to-film mutual slippage is poor, and a blocking phenomenon occurs. Further, the film may be cut or may not be a product.

There is a need for a non-magnetic support that simultaneously satisfies these conflicting properties.

Further, there is a demand that the output waveform has no abnormality even when the data is reproduced by a conventional magnetic head running on a magnetic recording medium, and that the recording medium has compatibility.

In view of the above problems, the present invention provides:
An object of the present invention is to provide a magnetic recording medium which is hard to be bent, wrinkled, and deformed, has good compatibility with a conventional magnetic recording medium, has good electromagnetic conversion characteristics and running properties, and can record for a long time.

[0010]

In the magnetic recording medium of the present invention, the nonmagnetic support forming the magnetic layer is made of an aromatic polyamide film, and the thickness of the nonmagnetic support is 10 μm.
Hereinafter, the Young's modulus in the vertical direction is 1000 kg / mm ² or more,
In this configuration, the Young's modulus in the width direction is 1300 kg / mm ² or more.

According to the structure of the present invention described above, the aromatic polyamide film is used as the non-magnetic support, and has a thickness of 10 μm.
m or less, the Young's modulus in the longitudinal direction is 1000 kg / mm ² or more, and the Young's modulus in the width direction is 1300 kg / mm ² or more.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The magnetic recording medium of the present invention is a magnetic recording medium having a magnetic layer formed on a non-magnetic support, wherein the non-magnetic support is an aromatic polyamide film, the thickness of which is 10 μm or less. Young's modulus in vertical direction is 1000kg /
mm ² or more, Young's modulus in the width direction is 1300 kg / mm ²
The configuration is as described above.

Further, the present invention is configured such that the magnetic layer is formed by vapor deposition in the above magnetic recording medium.

Further, according to the present invention, there is provided the magnetic recording medium, wherein inert particles having an average particle size of 0.02 to 0.3 μm are added to the non-magnetic support to form a magnetic layer of the non-magnetic support. and 10,000 / mm ² or more 20 million / mm ² was formed following projection arrangement on the surface.

An embodiment of the magnetic recording medium of the present invention will be described below with reference to the drawings. The magnetic recording medium 1 shown in FIG.
A magnetic layer 3 is formed on a non-magnetic support 2 made of an aromatic polyamide film, and a back layer 4 is formed on the back side.

The aromatic polyamide film used for the nonmagnetic support 2 is preferably formed by using a polyamide resin represented by the following general formula (1) or (2) or a polyamide resin having a copolymer thereof. .

[0017]

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[0018]

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In the above formulas ( ₁ ) and (2), the alkyl groups R ₁ , R ₂ and R ₃ are aromatic (groups) described in the following formulas ( ₃ ) to (7), or their hydrogen atoms are halogen, methyl,
It is selected from those substituted with functional groups such as ethyl, methoxy, nitro, and sulfone groups. Further, m and n are average degrees of polymerization, and are set to about 50 to 100.

[0020]

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[0021]

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[0022]

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[0023]

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[0024]

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Of the above-mentioned aromatic polyamides, particularly preferred is poly (p-phenylene terephthalamide) or poly (p-benzamide).

The aromatic polyamide used for the film of the nonmagnetic support 2 may contain a polymer of another component in an amount of about 20% or less.

For producing a film of a non-magnetic support from a copolymer of these aromatic polyamides, for example, dimethylacetamide, dimethylformamide, n-methylpyrrolidone, hexamethylphosphamide, γ-butyrolactone, tetramethylurea, dioxane Or a mixed solvent thereof, or a solvent obtained by adding an inorganic salt such as lithium chloride, calcium chloride, lithium carbonate, or lithium nitrate as a neutralized product of the polymerization stock solution. Using such a solvent for film formation, p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 2-nitro-p-phenylenediamine, 2-chloro-p-phenylenediamine, 4,4 ′ Aromatic diamines such as diaminobiphenyl and 3,3′-chlorobenzidine, and aromatic compounds such as terephthalic acid chloride, 2-chloroterephthalic acid chloride, terephthalic acid hydrazide, p-aminobenzoic acid hydrazide and p-aminobenzoic acid chloride; An aromatic polyamide resin obtained by polymerization or bonding with an aromatic dicarboxylic acid is melt-molded or solution-molded to form a film.

The thickness of the film of the non-magnetic support 2 is preferably 10 μm or less so that the magnetic recording medium 1 can be recorded for a long time and is compact and light.

The film of the nonmagnetic support 2 thus obtained is stretched, and its Young's modulus in the machine direction is 800 kg / m.
m ² or more, and the Young's modulus in the width direction is 1200 kg / mm ² or more. Preferably, inert particles having an average particle size of 0.01 to 0.3 μm are further added to the non-magnetic support 2, and 10,000 particles / mm ² or more are added to the surface on which the magnetic layer 3 is formed. 20,000,000 projections / mm ² or less are provided.

The inert particles in this case include, for example, silicon dioxide (including hydrates, diatomaceous earth, silica sand, quartz, etc.), alumina, and silicates containing 30% by weight or more of SiO ₂ (eg, amorphous or crystalline) Quality clay minerals, aluminosilicates including calcined and hydrated products), hot asbestos, zircon,
Fly ash, etc.), sulfates of Mg, Zn, Zr, Ca, Ba, phosphates of Li, Na, Ca (including monohydrogen salts and dihydrogen salts), benzoates of Li, Na, K, Ca , B
a, Zn, Mn terephthalate, Mg, Ca, Ba,
Titanate of Zn, Cd, Pb, Sr, Mn, Fe, Co, Ni, chromate of Ba, Pb, carbon (eg, carbon black, graphite, etc.), carbonate of Ca, Mg, fluorite, ZnS Etc. are exemplified.

More preferably, silicic anhydride, hydrous silicic acid,
Aluminum oxide, aluminum silicate (including calcined and hydrated), monolithium phosphate, trilithium phosphate, sodium phosphate, barium phosphate, titanium oxide, lithium benzoate, double salts of these compounds (hydrates) ), Clay, kaolin, bentonite, clay minerals such as clay, talc, diatomaceous earth, calcium carbonate and the like.

These inert fine particles may be added and dispersed in a solvent of one monomer before polymerization, or may be added and dispersed in a solvent to be polymerized at the time of polymerization. It may be added during the solution preparation step.

When the average particle size of the inert particles is less than 0.02 μm, the height of the projections formed on the surface of the magnetic layer 3 is low, and when the number of the projections is less than 10,000 / mm ² , the number of the projections is small. In any case, the effect of preventing head clogging cannot be obtained. On the other hand, addition of particles larger than 0.3 μm or addition amount exceeding 20 million particles / mm ² deteriorates the electromagnetic conversion characteristics of the magnetic recording medium.

Further, in order to improve the handleability of the film, for example, the film of the nonmagnetic support 2 has a two-layer structure, and the surface roughness SRa of the surface on which the magnetic layer is not formed
0.005 to 0.025 μm, preferably 0.010
It is desirable to set it to 0.020 μm. The surface roughness is adjusted by adding the above-mentioned inert particles and controlling the average particle size, particle size distribution, and the amount added.

The magnetic layer 3 is made of a ferromagnetic metal thin film and is formed by, for example, oblique evaporation or vertical evaporation. As the ferromagnetic metal thin film, a metal thin film mainly composed of Co, Ni, Fe or the like, or a metal thin film mainly composed of an alloy thereof can be used.

Further, for the purpose of improving the adhesion strength of the nonmagnetic support 2 to the film, or the corrosion resistance and wear resistance of the ferromagnetic thin film itself, the atmosphere during the deposition was set to an atmosphere in which oxygen gas is dominant. It is desirable to use a ferromagnetic thin film containing oxygen which is sometimes obtained.

The thickness of the magnetic layer 3 is preferably 0.05 to
It is about 1.0 μm, more preferably about 0.1 to 0.3 μm.

Further, by providing a lubricant on the surface of the magnetic layer 3, it is possible to further enhance the effect of improving the running property based on the shape of the particulate projections.

If necessary, the surface of the magnetic recording medium 1, the back surface, or the vicinity thereof, or a gap in the magnetic layer, the interface between the magnetic layer 3 and the non-magnetic support 2, the inside of the non-magnetic support 2, etc. Various additives such as a rust inhibitor, an antistatic agent, and a fungicide can be added by known means.

Next, the magnetic recording medium 1 having the configuration shown in FIG.
Were prepared and various characteristics were examined.

Example 1 2-Chloro-phenylenediamine corresponding to a molar ratio of 1: 0.9 to dehydrated n-methylpyrrolidone and 4,4 corresponding to a molar ratio of 1: 0.1
4′-Diaminenodiphenyl sulfone is dissolved by stirring,
This was cooled. Next, terephthalic acid chloride corresponding to a molar ratio of 1: 0.7 to n-methylpyrrolidone was added, and the mixture was stirred for 2 hours.

Thereafter, sufficiently generated calcium hydroxide was added and mixed with stirring. Ammonia water is added to this to complete the neutralization.

Further, it is dispersed in n-methylpyrrolidone.
SiO with an average particle size of 0.05 μm _TwoAddition of aromatic
A polyamide solution was obtained.

Next, this solution was uniformly cast on a metal drum having a polished surface at a temperature of 30 ° C., and dried in an atmosphere of 120 ° C. for about 10 minutes.

Next, the film formed on the metal drum was peeled off from the metal drum and stretched in the MD direction (longitudinal direction) while being continuously immersed in a water bath at 30 ° C. for about 30 minutes. Furthermore, the film was introduced into the tenter and
Then, a film constituting the nonmagnetic support 2 having a thickness of 5 μm was obtained by stretching in the TD direction (width direction).

(Examples 2 to 6, Comparative Examples 1 to 6) Stretching ratio in the longitudinal direction, stretching ratio in the width direction, and SiO 2
Changing ₂ particle size, respectively, to obtain a film constituting the non-magnetic substrate 2 in the same manner as in Example 1.

The Young's modulus and the number of surface protrusions in the width direction and the length direction were measured for the films of the nonmagnetic support 2 of each of the examples and comparative examples. The measurement conditions were as follows.

(1) Young's modulus Using a Tensilon type tensile tester, at a temperature of 25 ° C.
Pull under conditions of 55% relative humidity, (0.05-0.1
% Elongation) was used to calculate the Young's modulus.

(2) Number of surface protrusions The film surface was observed with an electron microscope at a magnification of 10,000 times or more, the number of protrusions was counted, and this was converted to 1 mm ² to obtain the number of surface protrusions.

Table 1 shows the measured values of the Young's modulus and the number of surface protrusions, and the particle size of SiO ₂ in each of the films.

[0051]

[Table 1]

Next, the magnetic layer 3 was formed on the film of the nonmagnetic support 2 of each example. A magnetic layer 3 made of a CoNi ferromagnetic metal thin film was formed on the nonmagnetic support 2 by a continuous vacuum oblique deposition method using the vapor deposition apparatus shown in FIG.

The vapor deposition apparatus shown in FIG. 2 is called a continuous winding vapor deposition apparatus. The continuous winding vapor deposition apparatus is, for example, a vacuum chamber A having an internal pressure of 10 ^-3 [Pa]. A cooling can C cooled to, for example, −20 ° C., and a deposition source D of a magnetic metal material forming the magnetic layer 13, for example, a Co—Ni alloy are disposed therein. Then, the above-described non-magnetic support 2 is unwound from the supply roll R ₁ , moved along the periphery of the cooling can C, and taken up by the take-up roll R ₂ .

The evaporation source D contains the above-described magnetic metal material, for example, a Co—Ni alloy, in a container P, and accelerates and irradiates the magnetic metal material with an electron beam B from an electron beam generating source X. And fly it to the cooling can C
The magnetic layer 3 is deposited on the non-magnetic support 2 running along the periphery of the substrate. In this case, the evaporation source D and the cooling can C
A shutter S is provided between the magnetic layer 3 and the magnetic layer 3 by oblique vapor deposition so that only vapor-deposited particles that enter the non-magnetic support 2 at a predetermined incident angle pass therethrough.

The conditions for the vapor deposition were such that the angle of incidence of the oblique vapor deposition was 90 ° to 45 ° from the normal direction of the film, the feed rate of the film was 25 m / min, and the vapor deposition thickness was 0.2 μm. The intensity of the electron beam was adjusted.

Next, a back layer 4 made of, for example, carbon or the like was applied to the back surface of the nonmagnetic support 2, and perfluoroether was applied as a lubricant to form the magnetic recording medium 1. Then, the magnetic recording medium 1 was cut into a width of 8 mm and assembled into an 8 mm cassette to obtain an 8 mm video tape.

The tape characteristics were examined for 8 mm video tapes produced from the non-magnetic support films of the examples and comparative examples, and comparison was made. Each video tape was set on a modified Sony high band 8 mm video deck EV-900, and the following characteristics were compared with a relative speed of 3.8 m / sec and a recording frequency of 7 MHz.

(1) Generation of squeal The state of generation of squeal (sound due to friction or the like) in the rotary head cylinder was examined.

(2) S / N ratio A commercially available Hi8ME tape (8 mm video tape) is
As B, the S / N ratio was measured comparatively.

(3) Still Life The time (minute) until the output was reduced to half of the first reproduction was measured. The higher the value, the better the durability, but the measurement was performed for a maximum of 120 minutes.

(4) Running Durability Reproducing and running 100 times repeatedly causes output fluctuation during running,
And the fall of the output after running with respect to the initial output was measured.

(5) Contact Characteristics with Head When the output signal at the time of tape reproduction, that is, the hit waveform is viewed on one screen, the output waveform is strong and flat, and the minimum value / maximum value of the output signal is 85% or more. Indicates that the output signal is distorted upward or downward at the center and the minimum / maximum value of the output signal is 7
The case where it is 0% or more is marked with Δ, and the case where the minimum / maximum value of the output signal is less than 70% is marked with x.

(6) Skew Characteristics The recorded magnetic recording medium was stored at 60 ° C. for 3 days, reproduced again at normal temperature and normal humidity, and the amount of signal deviation (skew) at the head switching point was measured.

Table 2 shows the measurement results.

[0065]

[Table 2]

According to Table 2, when comparing Example 2 and Comparative Example 3 in which only the Young's modulus in the vertical direction and the horizontal direction is different, the skew amount of Comparative Example 3 is about twice as large. The Young's modulus in the horizontal direction is larger in Comparative Example 3, but the difference is smaller, and it is understood that the Young's modulus in the vertical direction needs to be 1000 kg / mm ² or more in Example 2.

Next, from a comparison between Examples 1 and 2 and Comparative Examples 1 and 2 in which the added particle diameter and the number of surface protrusions are almost the same, in the case of Comparative Examples 1 and 2, It can be seen that the lower the Young's modulus in the width direction, the lower the hitting characteristics. In Comparative Example 1, the skew amount is increased. It can be seen that it is necessary to make the Young's modulus in the width direction 1300 kg / mm ² or more as in Examples 1 and 2 in order to improve the hitting characteristics.

Next, when comparing Example 3 with Comparative Example 4 in which the Young's modulus is equal and the added particle diameter and the number of surface protrusions are different, as shown in Comparative Example 4, the particle diameter is reduced and the surface protrusions are reduced accordingly. It can be seen that when the number is increased, squealing and output fluctuation of running durability occur. Therefore, it can be seen from Example 3 and Comparative Example 4 that the added particle diameter needs to be 0.02 μm or more and the number of surface projections needs to be 20 million / mm ² or less.

Further, when comparing Example 4 and Comparative Example 5 in which the number of surface projections is different, the S / N ratio is small in Comparative Example 5 although the Young's modulus is almost the same.
It can be seen that squealing has occurred, the still life is short, and the running durability has output fluctuations and output attenuation.
Since the characteristics are degraded due to the small number of surface projections, the number of surface projections is 10,000 / mm ^2.
It is understood that it is necessary to make the above. Comparative Example 6
Means that the Young's modulus in the width direction is small and the number of surface projections is 700
Since it is as small as 0 pieces / mm ² , the S / N ratio is small, the still life is short, the output of running durability is attenuated, and the hit characteristics are poor.

From the above, the Young's modulus in the vertical direction is 1000 k
g / mm ² or more, Young's modulus in the width direction is 1300 kg / m
By using an aromatic polyamide film having an m ² or more, a magnetic recording medium having excellent skew characteristics and good running properties can be formed. Furthermore, the addition of inert particles having an average particle diameter of 0.02~0.3μm a non-magnetic support body, the 10,000 / mm ² or more 20 million / mm ² or less of the magnetic layer to form the surface protrusion It can be seen that by providing the magnetic recording medium, it is possible to configure a magnetic recording medium having both good electromagnetic conversion characteristics and running properties and capable of long-term recording.

In the above example, the magnetic layer 3 is provided on the non-magnetic support 2.
Was formed by vapor deposition, but the magnetic recording medium of the present invention can be similarly applied to a magnetic recording medium in which a magnetic layer is coated and formed on a nonmagnetic support, for example. In addition, a configuration in which the back layer 4 on the back surface of the nonmagnetic support 2 is not formed, a configuration in which a protective film is formed on the surface of the magnetic layer, and a non-conductive layer such as an underlayer between the nonmagnetic support 2 and the magnetic layer 3. A configuration for forming a magnetic layer and the like can be adopted.

The magnetic recording medium of the present invention is not limited to the above-described example, and may take various other configurations without departing from the gist of the present invention.

[0073]

According to the above-described magnetic recording medium of the present invention, the thickness is 10 μm or less and the Young's modulus in the longitudinal direction is 1000 μm.
kg / mm ² or more, Young's modulus in the width direction is 1300 kg /
By using an aromatic polyamide film having a thickness of not less than mm ² , a magnetic recording medium having few folds, wrinkles and deformations, good compatibility with conventional magnetic recording media, and excellent skew characteristics can be formed.

Further, an average particle size of 0.0
10,000 particles / mm ² by adding inert particles of 2 to 0.3 μm.
When the magnetic layer is provided on the surface on which the projections of not less than 20 million protrusions / mm ² are formed, there are few breaks, wrinkles, and deformations, good compatibility with conventional magnetic recording media, excellent skew characteristics, and excellent electromagnetic characteristics. A magnetic recording medium having both conversion characteristics and running properties and capable of long-term recording can be configured.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of a magnetic recording medium according to the present invention.

FIG. 2 is a schematic configuration diagram of a vapor deposition device used for vapor deposition of a magnetic layer.

[Explanation of symbols]

1 magnetic recording medium, 2 non-magnetic support, 3 magnetic layer, 4
Back layer, A vacuum chamber, B electron beams, X electron beam source, C cooling can, R ₁ a supply roll, R ₂
Take-up roll, D evaporation source, P container, S shutter

Claims (3)

[Claims] 1. A magnetic recording medium having a magnetic layer formed on a non-magnetic support, wherein the non-magnetic support is an aromatic polyamide film, the thickness of the non-magnetic support is 10 μm or less, Young's modulus in the longitudinal direction of the body is 1000 kg / m
m ² or more, and the Young's modulus in the width direction of the nonmagnetic support is 1300 kg / m
The magnetic recording medium characterized in that m ² or more. 2. The magnetic recording medium according to claim 1, wherein said magnetic layer is formed by vapor deposition. 3. The non-magnetic support according to claim 1, wherein the non-magnetic support has an average particle size of 0.02 to 0.02.
0.3 μm of inert particles are added to the surface of the non-magnetic support on which the magnetic layer is to be formed to reach 10,000 particles / mm ² or more.
^2. The magnetic recording medium according to claim 1, wherein protrusions of not more than 10 million / mm ² are formed.