JPH07272247A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To reduce size and weight, to improve electromagnetic transducing characteristics and to enable to cope with high density recording. CONSTITUTION:A nonmagnetic layer of a metal or metal oxide is formed on at least one side of a plastic film and a magnetic layer is formed on the nonmagnetic layer to obtain the objective magnetic recording medium. By this structure, high rigidity as well as lightness, flexibility and surface smoothness of the plastic film is ensured.

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, and more particularly to a magnetic recording medium excellent in workability, electromagnetic conversion characteristics during use, and running property even if a support film is thin. .

[0002]

2. Description of the Related Art Conventionally, magnetic oxides such as ferrite, chromium, cobalt, nickel, and iron on the surface of polyester films, metals, etc., such as vinyl chloride-based polymers, acrylate-based polymers, urethane-based polymers, etc. A magnetic tape or floppy disk is formed by applying a coating material dispersed in a so-called binder and curing it to form a magnetic layer on the surface, or vapor depositing a metal such as cobalt or nickel to form a metal thin film magnetic layer. Are used as magnetic recording media.

On the other hand, there is a strong demand for improvement in magnetic recording density and miniaturization of magnetic recording media. For this reason, in magnetic recording media, the performance and thinning of the magnetic layer are being advanced. However, under the present circumstances, there is a limit to miniaturization by thinning only the magnetic layer.
In order to miniaturize the magnetic recording medium, it is important to reduce the thickness of the magnetic layer as well as the thickness of the film that is the support of the magnetic layer.

[0004]

However, generally, when the thickness of the support film is made thin, the rigidity of the film itself becomes insufficient, so that problems such as contact force with the magnetic head during use and breakage of the film during running may occur. However, the conventional polyester film has a limitation in thinning the film because of the problem of the processability when producing the magnetic recording medium.

An object of the present invention is to solve the above problems and to provide a magnetic recording medium corresponding to a thinner support film.

[0006]

In order to achieve the above object, the present invention provides: 1. A magnetic recording medium characterized in that a non-magnetic metal or metal oxide layer is provided on at least one side of a plastic film, and a magnetic layer is provided on the non-magnetic metal or metal oxide layer. The film is a composite film in which the thickness of the non-magnetic metal or metal oxide layer satisfies the following formula (1) with respect to the thickness of the plastic film.
The magnetic recording medium described.

0.0005 <d / D <0.5 (1) where D is the thickness (μm) of the plastic film, d
Indicates the thickness (μm) of the metal layer or the metal oxide layer.

[0008]

The plastic film referred to in the present invention means
The organic polymer is melted or melt extruded and, if necessary, stretched in the longitudinal direction and the width direction. Examples of the organic polymer include polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate, polyethylene-2 and 6 naphthalate,
Polyamide such as nylon 6, nylon 66, nylon 12, vinyl chloride, vinylidene chloride, polyvinyl alcohol, aromatic polyamide, polyamideimide, polyetherimide, polysulfone, polyethersulfone,
Examples thereof include polyether ether ketone, polyarylate, polyphenylene sulfide, polyphenylene oxide and the like. Among them, polyesters such as polyester and polyarylate are preferably used, and among them, a biaxially oriented polyester film is particularly preferably used.

Further, these copolymers, copolymers with other organic polymers, or those containing other organic polymers may be used. Known additives such as antistatic agents, organic or inorganic lubricants may be added to these organic polymers.

The thickness of the plastic film of the present invention is
Although not particularly limited, the range of 1 to 100 μm is desirable in view of suitability as a magnetic medium film. Particularly when used as a magnetic tape, the range of 2 to 30 μm, more preferably 3 to 15 μm is preferable.

A nonmagnetic metal or metal oxide layer is provided on at least one side of such a plastic film.

Specific examples of the non-magnetic metal or metal oxide used in the present invention include Al, Ti, Si, Cu and Zr, and these metals or oxides are used. Further, in the case of an oxide, it may be in a completely oxidized state in which the valence of the metal and the amount of oxygen to be bonded are the same, or the so-called incomplete oxidation in which the amount of oxygen is insufficient with respect to the valence of the metal. It may be in a state. However, for the purpose of improving the rigidity of the film of the present invention, a so-called incompletely oxidized layer is more preferable. The incomplete oxidation means a state in which the oxygen / metal ratio of the obtained oxide film is smaller than 1 with respect to the oxygen / metal ratio in the completely oxidized state of the metal used, and the range of 0.3 to 0.9 is preferable. , And more preferably 0.4 to 0.8.

As a method for providing a nonmagnetic metal or metal oxide layer on the surface of a plastic film, a plating method,
A vacuum deposition method, a sputtering method, an ion plating method, or the like can be used.

In the case of providing an oxide layer, when performing vacuum vapor deposition, sputtering or ion plating,
From the viewpoint of productivity, it is preferable that oxygen is allowed to coexist and the oxidation reaction proceeds simultaneously with vapor deposition.

The plastic film used in the present invention may be chemically or physically treated on one side or both sides or coated with another material.

In the present invention, the thickness of the non-magnetic metal or oxide layer (d (μ
m)) is the thickness of the plastic film used (D (μ
m)), the range is 0.0005 <d / D <0.5. When d / D is less than 0.0005, the effect of improving the rigidity is small, and when it is more than 0.5, the plastic film has reduced lightness, flexibility and water resistance, and the film is deformed. Is not preferred. It is preferably 0.0008 <d / D <0.2, and more preferably 0.001 <d / D <0.1.

Thus, the plastic film having a non-magnetic metal or metal oxide layer formed on at least one side used in the present invention has a tensile elastic modulus in the longitudinal direction of 400 kg.
/ Mm ² , preferably 500 kg / mm ² , and particularly preferably 600 kg / mm ² or more. The elastic modulus is 400
If it is less than kg / mm ² , the tape may be broken or the tape may be broken in an extreme case when it is run as a magnetic tape, which is not preferable.

The magnetic recording medium of the present invention comprises a plastic film having a non-magnetic metal or metal oxide layer formed on at least one surface thereof, and a magnetic layer formed on the non-magnetic metal or metal oxide layer. The magnetic layer is formed by chlorinating a ferromagnetic oxide powder such as γ-ferrite, cobalt-containing γ-ferrite, chromium oxide, or a ferromagnetic metal powder such as iron, cobalt, nickel, iron-cobalt, or iron-nickel. It is formed by dispersing it in an organic binder such as vinyl polymer, acrylic ester polymer, urethane polymer, etc., coating and curing it on the non-magnetic metal or metal oxide layer of the base material. It By forming the magnetic layer on the non-magnetic metal or metal oxide layer, the coatability of the magnetic layer is improved and the high-order magnetic layers can be prevented from falling off or being scraped.

[0020]

EXAMPLES The present invention will be described below with reference to examples.

The characteristic values of the present invention are measured by the following measuring methods.

(1) Tensile Modulus According to JIS-K-7127. Using an Instron type tensile tester, a sample having a sample length of 50 mm and a sample width of 10 mm was used and measured at 20 ° C. and 65% RH.

(2) Lamination Thickness The cross section of the film was observed with a microscope to measure the thickness of the plastic film and the metal or metal oxide layer.

(3) Travelability The produced video tape was brought into contact with a fixed hard chrome-plated metal roll having a diameter of 6 mm at a winding angle of 135 °, and was run under the conditions of a tension of 54 g and a speed of 1 m / min. The start and stop were repeated, and the running property was evaluated from the state of the tape at that time. 3: The tape runs well.

2: Tape wrapping occurs at start / stop.

1: The tape breaks and breaks.

Example 1 A partial oxide film of aluminum was formed on a 7 μm biaxially stretched polyethylene terephthalate film (longitudinal tensile modulus of elasticity 450 kg / mm ² , widthwise tensile modulus of elasticity 360 kg / mm ² ) by vacuum deposition. That is, using an electron beam heating type vacuum vapor deposition machine equipped with a vapor deposition electrode and a cooling roll, granular aluminum filled in an alumina crucible was heated and melted by an electron beam while being evaporated, and vapor was deposited on the film surface (one side). At this time, oxygen gas was allowed to flow little by little to partially oxidize the metal surface formed by vapor deposition. The obtained partial aluminum oxide film-forming composite film was cut, and the thicknesses of the film and the partial oxide film were measured, and they were 7 μm and 0.01 μm, respectively, and the d / D was 0.00.
It was 8. In addition, as a result of measuring the ratio of oxygen and aluminum in the surface metal oxide layer with a secondary ion mass spectrometer,
The oxygen / aluminum element ratio was 0.9.

This composite film had a tensile elastic modulus in the film longitudinal direction of 600 kg / mm ² and a tensile elastic modulus in the width direction of 460 kg / mm ² .

200 parts of magnetic fine powder (γ-ferrite),
30 parts of polyurethane resin, 10 parts of nitrocellulose, 10 parts of vinyl chloride / acetate copolymer, 5 parts of lecithin, 100 parts of cyclosexanone, 100 parts of methyl isobutyl ketone and 300 parts of methyl ethyl ketone are mixed and dispersed in a ball mill for 48 hours, and then 5 parts of polyisocyanate compound. Was added to prepare a magnetic paint. This was applied onto the oxide film layer of a partially oxide film-formed polyethylene terephthalate film, magnetically oriented before the paint was sufficiently dried and solidified, and then dried.
Further, this coated film was surface-treated with a super calendar and slit into a 1/2 inch width to obtain a video tape. As a result of evaluating the runnability of this video tape, the runnability was 3, and the runnability was good.

Comparative Example 1 A video tape was prepared and evaluated in the same manner as in Example 1 except that the untreated polyethylene terephthalate film used in Example 1 was used. Tape wrapping occurred at the start and stop, and the evaluation was 2.

Example 2 Using a 4 μm biaxially stretched polyethylene 2,6 naphthalate film (longitudinal tensile modulus of elasticity 720 kg / mm ² , widthwise tensile modulus of elasticity 750 kg / mm 2), aluminum was vacuum-deposited. A partial oxide film was formed. That is, an electron beam heating type vacuum vapor deposition machine equipped with two vapor deposition electrodes and cooling rolls was evacuated to 2 × 10 ^-3 Pascal, and then carbon dioxide gas was introduced to a pressure of 4 × 10 ^-1 Pascal to form a coaxial cylindrical magnetron. E value of 200 using electrodes
A low temperature plasma treatment was performed at an intensity of W · min / m ² , followed by vacuum deposition of aluminum. In the vacuum vapor deposition, alumina crucible was filled with granular aluminum, and aluminum was evaporated while being heated and melted by an electron beam. At the same time, oxygen gas was allowed to flow little by little to form an aluminum oxide film layer on the film surface (both sides). The obtained double-sided partial aluminum oxide film-forming film was cut, and the thickness of the partial oxide film was measured.
D was 0.05. The oxygen / aluminum element ratio was 1.0 as a result of measuring the ratio of oxygen and aluminum of the surface metal oxide layer with a secondary ion mass spectrometer.

The tensile elastic modulus of this film in the longitudinal direction is 1160 kg / mm ² , and the tensile elastic modulus in the width direction is 12.
It was 00 kg / mm ² .

The obtained partial oxide film-formed polyethylene 2, 6 naphthalate film was coated on one side with 100 parts of iron-cobalt-nickel alloy powder and 5 parts of saturated polyester resin.
Parts, acrylic-vinyl alcohol copolymer 10 parts, acrylic double bond-introduced polyether urethane elastomer 1
0 part, methyl ethyl ketone 120 parts and toluene 12
A magnetic paint obtained by mixing 0 parts was applied, magnetically oriented before the paint was sufficiently dried and solidified, and then dried. further,
This coated film was surface-treated with a super calendar. Further, 50 parts of carbon black, 30 parts of vinyl chloride-vinyl acetate-vinyl alcohol copolymer, 30 parts of polyurethane elastomer, 40 parts of nitrification cotton, 20 parts of polyisocyanate, 150 parts of methyl isobutyl ketone and 150 parts of toluene are provided on the opposite surface on which the magnetic layer is formed. The coating liquid containing the mixed parts was applied. After drying, the surface was smoothed by a calendar and then slit into a 1/2 inch width to obtain a video tape. As a result of evaluating the runnability of this video tape, the runnability was 3, and no winding or tape breakage occurred.

Comparative Example 2 A videotape was prepared and evaluated in the same manner as in Example 2 except that the untreated polyethylene 2,6 naphthalate film used in Example 2 was used, and the result was 1. , The tape broke during running, and the tape broke during start / stop.

Example 3 5 μm biaxially stretched polyester film (longitudinal tensile elastic modulus 850 kg / mm ² , widthwise tensile elastic modulus 400 k)
g / mm ² ) was used, and a silica oxide layer was formed on both sides in the same manner as in Example 2 except that evaporated metal silicon oxide was used. The thickness of the partial oxide film of the obtained double-sided partial silicon oxide film forming film was 0.15 μm on both sides,
d / D was 0.06. When the ratio of silicon to oxygen in the surface oxide layer was measured, the oxygen / silicon element ratio was 1.3. The obtained film had a tensile elastic modulus in the film longitudinal direction of 1400 kg / mm ² and a tensile elastic modulus in the width direction of 940 kg / mm ² .

A magnetic tape was produced in the same manner as in Example 1 and the running property was evaluated. As a result, the running property was 3, and good running property was obtained.

Example 4 A titanium film was formed on the film surface in the same manner as in Example 1 except that titanium was used as the vapor deposition metal and oxygen gas was not introduced. The thickness of the metal film layer is 0.
At 01 μm, the d / D was 0.008. The tensile elastic modulus in the longitudinal direction of this composite film is 550 kg / mm ² ,
The tensile elastic modulus in the width direction was 440 kg / mm ² . A magnetic tape was prepared in the same manner as in Example 1 and the runnability was evaluated. As a result, the runnability was 3, indicating that the runnability was good.

Comparative Example 4 A magnetic tape was prepared in the same manner as in Example 1 except that the magnetic layer was formed on the surface opposite to the partial oxide film, and the running property was evaluated. Winding occurred at the start and stop, and the runnability was 2.

[0039]

The magnetic recording medium obtained according to the present invention is
The support plastic film is manufactured by using the support plastic film which makes use of the lightness, flexibility and surface smoothness of the support plastic film and improves the rigidity thereof. Therefore, it becomes possible to significantly reduce the thickness of the support film as compared with the conventionally used thickness, and the magnetic recording medium of the present invention can be made smaller and lighter, and its rigidity makes it possible to improve electromagnetic conversion characteristics. It is possible to support high density recording.

Claims (2)

[Claims] 1. A magnetic recording medium comprising a nonmagnetic metal or metal oxide layer provided on at least one surface of a plastic film, and a magnetic layer provided on the nonmagnetic metal or metal oxide layer. . 2. A magnetic film according to claim 1, which is a composite film in which the thickness of the nonmagnetic metal or metal oxide layer satisfies the following formula (1) with respect to the thickness of the plastic film. recoding media. 0.0005 <d / D <0.5 (1) where D is the thickness (μm) of the plastic film, d
Indicates the thickness (μm) of the metal layer or the metal oxide layer.