JPH1049857A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the running property of a magnetic recording medium by forming a metal thin-film magnetic layer on a support, and a back coat layer on a face of the support opposite to a face on which the magnetic layer is formed. SOLUTION: First, Co is vapor-deposited on a PET film in a thickness of 6μm, and a magnetic layer in a thickness of 2000Å is formed. In addition, a lubricant layer in a thickness of 20Å(after a drying operation) is formed of a fluorine-based lubricant on the magnetic layer. Then, a back coat layer is formed on a face opposite to a face on which the film magnetic layer is formed in such a way that the film is coated by a gravare method with a paint for a back coat so as to be in a dried thickness of 0.5μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal thin film type magnetic recording medium on which a back coat layer containing a specific lubricant is formed.

[0002]

2. Description of the Related Art A magnetic recording medium, for example, a magnetic tape includes:
There is a coating tape formed by applying a magnetic paint in which a magnetic powder is dispersed in a binder on a film serving as a support, and a vapor-deposited tape containing no binder formed by vapor-depositing a metal on a film in a vacuum. . The vapor-deposited tape is said to be promising for high-density recording because it can increase the density of the magnetic material because the magnetic layer does not contain a binder.

[0003] The basic structure of a vapor-deposited tape currently sold or developed is a magnetic layer in which a magnetic metal is vapor-deposited on a support such as PET (polyethylene terephthalate), polyimide, or aramid using a vacuum vapor deposition method. have.
In addition, a top coat layer is formed to protect the magnetic layer and to act as a lubricant for smooth contact with the recording / reproducing head, and a support for improving the running property. The back coat layer is formed on the side opposite to the magnetic layer.

[0004] Conventionally, after a magnetic layer is vapor-deposited on a support in a vacuum, the support is taken out into the air, and then a carbon black or the like is coated on the surface of the support opposite to the magnetic layer surface. A ceramic powder or the like is dispersed in a binder (using a PVC-based, urethane-based, or nitrocellulose-based material alone or as a mixture), and the thickness after drying is 0.4 by a gravure method, a reverse method, or a die coating method. It is formed by coating so as to have a thickness of about 1.0 μm.

[0005]

As described above, conventionally,
The back coat layer of the magnetic recording medium is formed by applying a coating material containing a binder and inorganic particles such as carbon black and ceramics to a support, and the back coat layer mainly containing the inorganic particles and the binder. Indicates a tendency that the dynamic friction coefficient (μ) increases and the running performance becomes insufficient.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies in view of the above problems, and as a result, by forming a back coat layer containing a specific lubricant, a back coat layer having an appropriate surface property was formed. As a result, it has been found that the running property of the magnetic recording medium is improved, and the present invention has been completed.

That is, according to the present invention, an ester lubricant is provided on a support, a metal thin film type magnetic layer formed on the support, and a surface of the support opposite to the surface on which the magnetic layer is formed. And a back coat layer containing the same. Further, the present invention includes a support, a metal thin film type magnetic layer formed on the support, and a fluorine-based lubricant on a surface of the support opposite to a surface on which the magnetic layer is formed. A magnetic recording medium provided with a back coat layer is provided.

[0008] As described above, the present invention is characterized in that the back coat layer contains a specific lubricant. In the present invention, the back coat layer is formed by applying a back coat paint containing an ester lubricant or a fluorine lubricant and further containing inorganic particles, a binder, a solvent, and the like to the surface of the support opposite to the magnetic layer forming surface. It is formed by this.

As the ester-based lubricant used in the present invention, a fatty acid ester-based lubricant which is usually added to a magnetic coating material of a coating type magnetic recording medium can be mentioned. Particularly, butyl stearate is preferred.

Further, as the fluorine-based lubricant used in the present invention, the following general formula _{C n F 2n + 1 -O-} C m H 2m + 1 ( wherein, n number of 8 to 30, m is 6 Particularly preferred is a compound represented by the formula:
Such a compound is a compound in which a fluoroalkyl group and an alkyl group are ether-bonded, and can be obtained, for example, by hydrolyzing a fluoroalkyl alcohol and an aliphatic alcohol to form an ether bond as follows. _{C n F 2n + 1 -OH +} C m H 2m + 1 -OH → C n F
_{2n + 1 -O-C m H} 2m + 1 ( wherein, n, m are the same. As above) is optimal molecular weight 600 to 3000 of such compounds, n, the number, such as m the molecular weight is within this range It is preferred that

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a back coat layer is formed according to a conventionally known coating type back coat layer forming method. That is, the above-mentioned ester lubricant or fluorine lubricant and inorganic particles, a suitable binder,
A coating for a back coat is prepared by dispersing in a solvent, and this is applied on a support by an appropriate method. As the inorganic particles to be blended in the backcoat paint, carbon black is preferable. Other inorganic particles include γ-Fe ₂ O ₃ ,
Al ₂ O ₃ , TiO ₂ , CaCO ₃ , SiO _{2 and the} like can be mentioned. In addition, as a binder to be blended in the backcoat paint, a PVC-based, urethane-based, nitrified cotton-based binder, or the like can be used alone or in combination. In addition, various additives usually used in this field can be blended when forming a coating type back coat layer.

The coating for the back coat is prepared by a suitable method such as a gravure method, a reverse method, or a die coating method so that the thickness after drying is 0.4 to 1.0 μm. And applied on the opposite side. Thereby, the back coat layer of the present invention is formed.

The magnetic recording medium of the present invention has a so-called metal thin film type magnetic layer formed by a method such as vapor deposition or sputtering. The metal thin film is formed by a usual method such as evaporation or sputtering. Examples of the magnetic material for forming the metal thin film type magnetic layer include ferromagnetic metal materials used in the manufacture of ordinary metal thin film type magnetic recording media. For example, ferromagnetic metals such as Co, Ni, and Fe; Fe-C
o, Fe-Ni, Co-Ni, Fe-Co-Ni, Fe
-Cu, Co-Cu, Co-Au, Co-Y, Co-L
a, Co-Pr, Co-Gd, Co-Sm, Co-P
t, Ni-Cu, Mn-Bi, Mn-Sb, Mn-A
1, Fe-Cr, Co-Cr, Ni-Cr, Fe-Co
Ferromagnetic alloys such as -Cr and Ni-Co-Cr; In addition, Fe-N-based, Fe-C-based, and Fe-based systems formed by a so-called ion-assisted deposition method for supplying ions such as nitrogen ions, oxygen ions, and carbon ions during iron deposition.
The magnetic layer may be a -NO-based, Fe-CO-based, or Fe-NCO-based magnetic layer.

For high density recording, the magnetic layer of the magnetic recording medium is preferably formed on a substrate by oblique evaporation. The method for oblique deposition is not particularly limited, and follows a conventionally known method. The degree of vacuum at the time of vapor deposition is 10 ^-4 to 10 ^-7 Torr
It is about. The magnetic layer formed by vapor deposition may have either a single layer structure or a multilayer structure. In particular, by introducing an oxidizing gas to form an oxide on the surface of the magnetic layer, the durability can be improved. Although the thickness of the metal thin-film type magnetic layer is not limited, it is preferably 500-3000 °, and particularly preferably 500-2
000 ° is preferred. Further, the metal thin film type magnetic layer may have a single layer structure or a multilayer structure.

The magnetic layer has a thickness of 10 to 200 mm.
It is desirable to provide a protective layer of a certain degree, particularly a carbon thin film such as diamond-like carbon and graphite, a silicon-containing thin film such as silicon oxide and silicon carbide, and a zirconium oxide thin film. These thin films are ECR plasma CV
It can be formed by Method D.

Further, in the present invention, when a magnetic layer or a protective layer is formed, a lubricant layer made of a suitable lubricant may be formed on the protective layer. In particular, in the present invention, it is preferable to use a fluorine-based lubricant such as perfluoropolyether, and specifically, as the perfluoropolyether, those having a molecular weight of 2,000 to 5,000 are suitable, and for example, "FOMBLIN Z DIAC" [Carboxyl group-modified, manufactured by Montecatini Co., Ltd.], “FOMB
LIN Z DOL "(alcohol-modified, manufactured by Montecatini Co., Ltd.) can be used. The thickness of the lubricant layer may be appropriately determined in consideration of the use of the magnetic recording medium, the type of the lubricant, and the like.
It is about 200Å.

The support used in the magnetic recording medium of the present invention includes polyesters such as polyethylene terephthalate and polyethylene naphthalate; polyolefins such as polyethylene and polypropylene; cellulose derivatives such as cellulose triacetate and cellulose diacetate; polycarbonate; Vinyl chloride; polyimide;
Plastics such as aromatic polyamide are used. The thickness of these supports is about 3 to 50 μm.

One example of the composition of the coating composition for a back coat according to the present invention is shown below, but is not limited thereto. <When an ester-based lubricant is used>-100 parts by weight of inorganic particles-0.5 to 10.0 parts by weight of an ester-based lubricant-80 to 120 parts by weight of a binder-Solvent 6 to 9 times (weight) the above total amount <Ratio><When using a fluorine-based lubricant>-100 parts by weight of inorganic particles-0.05 to 3.0 parts by weight of a fluorine-based lubricant-80 to 120 parts by weight of a binder-Solvent 6 to 9 times the above total amount. (Weight ratio).

[0019]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 First, Co was deposited on a PET film having a thickness of 6 μm to form a magnetic layer having a thickness of 2000 °. On the magnetic layer, a fluorine-based lubricant (FOMBLIN Z DOL, alcohol-modified, manufactured by Montecatini Co., Ltd.) is used.
A lubricant layer of 0 ° (after drying) was formed. Next, a back coat layer was formed on the surface of the film opposite to the surface on which the magnetic layer was formed. The back coat layer was formed by applying a back coat paint having the following composition to a film by a gravure method so as to have a dry thickness of 0.5 μm.
The average surface roughness (Ra) of this back coat layer was 8.7 nm. <Coating for back coat> 100 parts by weight of carbon black 3.5 parts by weight of butyl stearate 52 parts by weight of nitrocellulose 52 parts by weight of polyurethane resin 830 parts by weight of cyclohexanone

Example 2 First, Co was deposited on a 6 μm-thick PET film to form a magnetic layer having a thickness of 2000 °. On the magnetic layer, a fluorine-based lubricant (FOMBLIN Z DOL, alcohol-modified, manufactured by Montecatini Co., Ltd.) is used.
A lubricant layer of 0 ° (after drying) was formed. Next, a back coat layer was formed on the surface of the film opposite to the surface on which the magnetic layer was formed. The back coat layer was formed by applying a back coat paint having the following composition to a film by a gravure method so as to have a dry thickness of 0.5 μm.
The average surface roughness (Ra) of this back coat layer was 7.7 nm. <Backcoat paint>-100 parts by weight of carbon black-0.5 parts by weight of fluorine-based lubricant ^* 50 parts by weight of nitrocellulose-50 parts by weight of polyurethane resin-802 parts by weight of cyclohexanone (Note) * Fluorine-based lubricant is C ₁₆ F ₃₃ is -O-C ₁₈ H _37.

COMPARATIVE EXAMPLE 1 First, Co was vapor-deposited on a 6 μm-thick PET film to form a 2000-μm-thick magnetic layer. On the magnetic layer, a fluorine-based lubricant (FOMBLIN Z DOL, alcohol-modified, manufactured by Montecatini Co., Ltd.) is used.
A lubricant layer of 0 ° (after drying) was formed. Next, a back coat layer was formed on the surface of the film opposite to the surface on which the magnetic layer was formed. The back coat layer was formed by applying a back coat paint having the following composition to a film by a gravure method so as to have a dry thickness of 0.5 μm.
The average surface roughness (Ra) of this back coat layer was 4.2 nm. <Coating material for back coat> 100 parts by weight of carbon black 50 parts by weight of nitrocellulose 50 parts by weight of polyurethane resin 800 parts by weight of cyclohexanone

<Evaluation of Performance> The film on which the magnetic layer, lubricant layer and back coat layer obtained in Examples 1 and 2 and Comparative Example 1 were formed was cut into a width of 8 mm, and the coefficient of kinetic friction was determined by the following method. μ) and jitter were evaluated. Table 1 shows the results. Dynamic friction coefficient Under a condition of 20 ° C./50% (temperature / humidity), a wrap angle of 115 ° is obtained at a speed of 14.3 mm / sec with respect to a friction body (diameter 5 mm, stainless steel, surface roughness 0.2 S). The value when 20 g of tension was applied to the tape was measured by a friction coefficient measuring machine. Jitter A commercially available Hi-8 VTR was modified, and a jitter meter was connected thereto to measure jitter. The jitter was measured in a so-called high (Hi-8) mode.

[0024]

[Table 1]

[0025]

According to the present invention, since the back coat layer contains a specific lubricant, the lubricating effect of the back coat layer is improved and an appropriate dynamic friction coefficient (μ) is provided. The performance is improved.

Continued on the front page (72) Inventor Osamu Yoshida 2606 Kabane-cho Akabane, Haga-gun, Tochigi Prefecture Inside Kao Co., Ltd.

Claims (7)

[Claims] 1. A backing comprising an ester lubricant on a surface of a support, a metal thin film type magnetic layer formed on the support, and a surface of the support opposite to a surface on which the magnetic layer is formed. A magnetic recording medium having a coat layer formed thereon. 2. The magnetic recording medium according to claim 1, wherein the ester lubricant is butyl stearate. 3. A backing containing a fluorine-based lubricant on a surface of a support, a metal thin-film type magnetic layer formed on the support, and a surface of the support opposite to a surface on which the magnetic layer is formed. A magnetic recording medium having a coat layer formed thereon. Wherein said fluorine-based lubricant, in the following general formula _{C n F 2n + 1 -O-} C m H 2m + 1 ( wherein, n is the number of 8 to 30, m is a number of 6 to 30 4. The magnetic recording medium according to claim 3, comprising a compound represented by the formula: 5. A lubricant layer is formed on the magnetic layer with a perfluoropolyether-based lubricant.
The magnetic recording medium according to any one of claims 1 to 4, wherein 6. The protective layer according to claim 1, wherein a protective layer is formed on the magnetic layer, and a lubricant layer is formed on the protective layer with a perfluoropolyether-based lubricant. Magnetic recording medium. 7. An average surface roughness (R) of the back coat layer.
7. The magnetic recording medium according to claim 1, wherein a) is from 6 to 30 nm.