JPH10105942A - Magnetic recording media - Google Patents

Abstract

[PROBLEMS] To use a thin base film having a thickness of 4.5 μm or less as a non-magnetic support of a magnetic recording medium.
Provided is a magnetic recording medium which prevents cupping, has excellent running properties, and realizes good head touch. SOLUTION: In a magnetic recording medium having one or two or more magnetic layers having a column structure inclined in the same direction formed by vapor deposition on a nonmagnetic support, a magnetic layer opposite to the magnetic layer of the nonmagnetic support is provided. A magnetic recording medium, wherein at least one backcoat layer is formed on a surface by vapor deposition, and the backcoat layer is formed from a thin film composed of a column inclined in a direction opposite to the inclination of the column of the magnetic layer. .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deposition type magnetic recording medium, and more particularly to a back coat layer. More specifically, the present invention relates to a magnetic recording medium that can prevent cupping of a magnetic air recording medium and maintain good running performance and head touch by forming a thin film forming a back coat layer by controlling the structure by oblique evaporation.

[0002]

2. Description of the Related Art Conventionally, a backcoat layer is formed on a surface of a nonmagnetic support opposite to a magnetic layer so as to have the following three functions. (1) By providing conductivity, adhesion of dust is prevented by an antistatic effect. (2) Running stability is obtained by controlling surface properties (coefficient of friction). (3) From the viewpoint of hardness and the like, the surface having the magnetic layer and the back surface having the back coat layer are balanced to prevent the occurrence of warpage.

[0003] As a method of forming the back coat layer, carbon having a particle size of 10 to 100 nm is dispersed in a binder (using a vinyl chloride-based, urethane-based, or nitrified cotton-based material alone or as a mixture), and the gravure method or the reverse method Conventionally, a method of applying a die coating method so that the thickness after drying becomes 0.4 to 1.0 μm, or a method of depositing a metal or metalloid in a vacuum vessel has been conventionally performed. In the method of forming the back coat layer by coating, the method (1) is performed by controlling the conductivity of carbon, the method (2) is controlled by controlling the particle diameter of the carbon and the coating process, and the method (3) is performed by controlling the coating process. By controlling the binder and the coating thickness, each was satisfied. However, due to the presence of the binder, the back coat layer could not obtain sufficient conductivity, and the magnetic layer was damaged because the medium had to be taken out to the atmosphere once when applying the back coat layer due to the influence of the solvent of the binder. There is a problem that the number of dropouts increases in the dropout inspection due to contamination, dirt, or adhesion of dust.

On the other hand, in the method of depositing a metal in a vacuum, the influence of the binder can be avoided, so that the conductivity of the back coat layer can be improved and the number of dropouts can be reduced. However, it is not possible to obtain sufficient conductivity when depositing a metalloid,
Also, when a metal is deposited, there have been problems in that the surface of the back coat layer becomes too smooth, it is difficult to provide the back coat layer with sufficient hardness, and the end face of the medium is deformed in a wavy manner. To solve the above problems, the present applicant has proposed a method of improving the conductivity of a back coat layer by vacuum-depositing a metalloid and an impurity in Japanese Unexamined Patent Publication No. Hei 7-1995.
Japanese Patent Application Laid-Open No. 98830/98 proposes that a back coat layer is made of two or more layers of metal or metalloid to impart appropriate surface properties and elasticity. Japanese Patent Application Laid-Open No. H8-1010 proposes that the back coat layer has sufficient hardness by forming
Japanese Patent Application Laid-Open No. Hei 8-102051 discloses a proposal in Japanese Patent Application Laid-Open No. Hei 8-102051 that a diamond-like carbon layer is formed on a back coat layer to suppress deformation of an end face of a magnetic recording medium.

[0005]

It is desired to produce a high quality magnetic recording medium with high productivity in the future. However, in the method of forming the back coat layer by coating as described above, a sufficient conductivity is required. This is disadvantageous in that it is difficult to obtain the desired characteristics and the number of dropouts cannot be reduced. The surface property or hardness of the back coat layer was also improved by the above-mentioned proposal in the method of vapor deposition, but further suppression of cupping, improvement in running stability and head touch were desired, so the surface property of the back coat layer was further improved. Alternatively, improvement in hardness has been desired. In the future, the thickness of magnetic recording media will tend to be smaller in order to store more information in a container of a fixed size, and the magnetic layer and back coat layer formed on a non-magnetic support It has become necessary to make the recording medium have an appropriate hardness.
Therefore, in the present invention, in view of the conventional problems as described above, and for the future, in a magnetic recording medium having a magnetic layer formed by oblique deposition, by controlling the structure of the thin film forming the back coat layer It is an object of the present invention to obtain a magnetic recording medium that can prevent occurrence of cupping, achieve high running stability, and achieve good head touch.

[0006]

Means for Solving the Problems For this reason, the present inventors have:
In a magnetic recording medium with a magnetic layer having a column structure formed by oblique vapor deposition, a back coat layer having a column structure obliquely vapor-deposited is formed on the surface opposite to the magnetic layer on the nonmagnetic support by controlling the structure. As a result, the present inventors have found that the above object can be achieved, and have completed the present invention.

The back coat layer obtained by the present invention is formed on the surface opposite to the magnetic layer having a column structure inclined in the same direction and formed on the non-magnetic support by oblique vapor deposition. It is characterized by comprising a thin film having a column structure inclined in the direction opposite to the column. Here, the structural analysis of a plane parallel to the longitudinal direction of the non-magnetic support and perpendicular to the surface of the non-magnetic support is performed by a transmission electron microscope (TEM).
Evaluation is performed by observation with a photograph or electron beam diffraction. Further, the back coat layer is evaporated by irradiating a metal or metalloid with an electron beam in a vacuum chamber, and the metal or metalloid obtained by attaching the metal or metalloid on a nonmagnetic support or oxides, nitrides, Formed by carbide. Various metals can be attached as the back coat layer, but Al, Cu, Zn, Sn, N
i, Ag, etc. and their alloys are used.
Cu-Al alloys are preferred from the viewpoints of adhesion speed and stability after oxidation. Further, as the semimetal that adheres as the back coat layer, Si, Ge, As, Sc, Sb, or the like is used, and Si is particularly preferable in terms of cost and adhesion speed. Furthermore, it is also preferable to perform any one of oxidation, nitridation, and carbonization simultaneously when depositing these metals or metalloids to form an oxide film, a nitride film, and a carbonized film. The thickness of the back coat layer is set to be smaller than the thickness of the magnetic layer by 2,000 mm in consideration of the rigidity balance with the magnetic layer formed on the surface of the nonmagnetic support opposite to the back coat layer. 2 more than layer thickness
It is formed to have a thickness of 000 thick. The back coat layer may be formed on the non-magnetic support either before or after the formation of the magnetic layer and the protective layer on the non-magnetic support.

[0008] As the nonmagnetic support used in the present invention, polyethylene terephthalate (PET) is preferable from the viewpoint of cost. However, polyesters such as polyethylene naphthalate, polyolefins such as polyethylene and polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, and plastics such as polycarbonate, polyvinyl chloride, polyimide, and aromatic polyamide can also be used. The thickness of these non-magnetic supports is generally considered to be about 50 μm, but from the practical point of view in the future, it is preferably 4.5 μm or less. The thickness is preferably 6.0 μm or less from the thickness of the nonmagnetic support and the thickness of each of the constituent layers.

In the present invention, the metal thin film type magnetic layer is formed by ordinary methods such as vapor deposition and sputtering. Examples of the magnetic material for forming the metal thin film type magnetic layer include ferromagnetic metal materials used for manufacturing a normal metal thin film type magnetic recording medium. For example, a ferromagnetic metal such as Co, Ni, Fe or the like, or Fe-Co, Fe-Ni, Co-Ni, Fe-Co
-Ni, Fe-Cu, Co-Cu, Co-Au, Co-
Y, Co-La, Co-Pr, Co-Gd, Co-S
m, Co-Pt, Ni-Cu, Mn-Bi, Mn-S
b, Mn-Al, Fe-Cr, Co-Cr, Ni-C
and ferromagnetic alloys such as r-Fe-Co-Cr and Ni-Co-Cr. Particularly, from the viewpoint of the magnetic properties of the magnetic material used for the magnetic recording medium, at least one selected from a ferromagnetic alloy mainly composed of Co, Ni, and Fe and a nitride or carbide thereof is preferable. By introducing an oxidizing gas at the time of vapor deposition to form an oxide layer on the surface of the magnetic layer, the durability of the magnetic layer can be improved. The magnetic layer formed by vapor deposition may be a single layer or a multilayer of two or more layers, but is preferably a multilayer for high-density recording, and a practical range of two to three layers is appropriate. Further, it is preferable that the magnetic layer of the magnetic recording medium is formed on the non-magnetic support by oblique vapor deposition, and when the magnetic layer is a multilayer, the columns forming the magnetic layers are formed so that the inclination is in the same direction. You. The method of oblique deposition is not particularly limited, and follows a conventionally known method. The thickness of the metal thin-film magnetic layer is not limited, but is preferably 500 to 5000 °, and particularly preferably 800 to 3000 ° as a practical range. In the case of two layers, the lower layer is about 200 to 2000 ° and the upper layer is 100 to
It is preferably about 1000 °, and in the case of three layers,
Preferably, the thickness is about 00 to 2000 °, the middle layer is about 200 to 2000 °, and the upper layer is about 100 to 1000 °.

For the purpose of improving the durability and corrosion resistance of the magnetic recording medium, a protective layer of a high hardness thin film can be provided on the magnetic layer and the back coat layer. Such a protective layer is made of a non-magnetic material such as carbide, nitride, or oxide such as diamond-like carbon, boron carbide, silicon carbide, boron nitride, silicon nitride, silicon oxide, or aluminum oxide. The film is formed by the PVD method.

A lubricating layer made of an appropriate lubricant may be formed on the protective layer on the magnetic layer and the back coat layer or on the protective layer on the magnetic layer and the protective layer on the back coat layer. The lubricating layer may be formed by applying a solution obtained by dissolving a lubricant in an appropriate solvent, or may be formed by spraying the lubricant in a vacuum. As the lubricant, a fluorine-based lubricant such as perfluoropolyether is preferable from the viewpoint of lubricity, in either case of application or spraying,
For example, perfluoropolyether has a molecular weight of 200
Those having 0 to 5000 are preferred. The amount of the lubricant to be applied or sprayed is appropriately determined depending on the use of the magnetic recording medium and the type of the lubricant.
It is about 00 °.

[0012]

FIG. 1 shows an example of a vapor deposition apparatus 1 suitable for producing a magnetic recording medium according to the present invention. Here, a vacuum chamber 2 connected to a vacuum evacuation device (not shown), a cooling can roll 3 provided in the vacuum chamber 2, and a nonmagnetic support 4 such as a PET film running on the cooling can roll 3. Including a take-up roll and a take-up roll. A crucible 7 is disposed below the cooling can roll 3 as an evaporation source, and a back coat forming material, for example, a Cu-Al alloy is accommodated in the crucible 7. An electron gun 8 is arranged in the vacuum chamber 2,
The electron beam is irradiated to the crucible 7, and the Cu in the crucible 7
-To evaporate the Al alloy. Above the crucible 7, deposition preventing plates 9 and 9 ′ for limiting the incident angle of the Cu—Al alloy vapor from the crucible 7 evaporated by the electron beam toward the cooling can roll 3 to the nonmagnetic support 4.
Are arranged so that oblique vapor deposition can be performed. Further, nozzles 10 and 10 'for supplying oxygen gas are disposed immediately above the deposition-preventing plates 9 and 9', respectively.

The manufacture of a magnetic recording medium according to the present invention using such a vapor deposition apparatus 1 is as follows. That is, after the inside of the vacuum chamber 2 is set to a predetermined degree of vacuum by the vacuum exhaust device, the nonmagnetic support 4 is caused to travel from the unwinding roll onto the cooling can roll 3. At this time, the non-magnetic support may be either a magnetic layer and a protective layer formed on the magnetic layer in advance, or a non-magnetic support having no magnetic layer formed thereon. However, when at least one magnetic layer is formed in advance by oblique deposition, the nonmagnetic support 4
The inclination of the column forming the upper magnetic layer and the running direction of the nonmagnetic support 4 are important. That is, in FIG. 1, there are two rotation directions of the cooling can roll 3: rotating in the same direction (clockwise) as the clockwise direction and rotating in the opposite direction (clockwise) to the clockwise direction. In the case of (1), the running direction of the non-magnetic support 4 is such that the inclination of the column of the magnetic layer formed on the non-magnetic support when the non-magnetic support is down and the magnetic layer is It must be inclined forward with respect to the direction of travel. In the other case, the inclination of the column of the magnetic layer formed on the non-magnetic support when the non-magnetic support is turned down and the magnetic layer is turned up in the same manner, with respect to the traveling direction of the non-magnetic support 4 Must be tilted backwards. In this case, the roll 5 is an unwinding roll and the roll 6 is a winding roll. In this case, the roll 6 is an unwinding roll and the roll 5 is a winding roll. As described above, the nonmagnetic support 4 is caused to travel from the unwinding roll onto the cooling can roll 3. An electron beam is irradiated from the electron gun 8 toward the crucible 7 to melt and evaporate the Cu—Al alloy in the crucible 7, and
Is vapor-deposited. This is done in the presence of oxygen supplied from nozzles 10 and 10 '. The non-magnetic support 4 thus treated is wound on a winding roll. A protective layer is formed on the back coat layer if necessary. The protective layer is formed by forming a high-hardness thin film such as diamond-like carbon by CVD or PVD as described above. Further, when the protective layer is formed on the magnetic layer and the magnetic layer in advance, if necessary, the lubricating layer is immediately formed on the protective layer on the magnetic layer and the uppermost layer on the back coat layer side. In the case where the magnetic layer is not formed, at least one magnetic layer is formed by oblique deposition so that the inclination of the column of the magnetic layer is opposite to the inclination of the column of the back coat layer, and a protective layer is formed thereon. Is formed, and a lubricating layer is formed on the protective layer on the magnetic layer and the uppermost layer on the back coat layer side. As described above, the formation of the lubricating layer is performed by applying a fluorine-based lubricant in the air or spraying it in a vacuum. After the formation of the necessary layers is completed, slitting, wrapping, assembling into a cassette, and the like are performed by a general method.

[0014]

【Example】

Example 1 A non-magnetic film in which a two-layer metallic cobalt magnetic layer was formed on a 4.5 μm-thick PET film by oblique vapor deposition to a total thickness of 1900 mm, and a diamond-like carbon film was formed thereon as a protective layer with a thickness of 120 mm. A support was provided. On this non-magnetic support, a back coat layer was formed on the surface of the non-magnetic support opposite to the magnetic layer using the vapor deposition apparatus shown in FIG. After the inside of the vacuum chamber 2 was evacuated to 2 × 10 ⁻⁵ Torr, the Cu—Al alloy in the crucible 7 was irradiated with an electron gun 8 at an output of 20 kW to form a steam atmosphere. The non-magnetic support 4 is moved from the roll 6 to the cooling can roll 3
Pass it over to the roll 5 and roll the cooling can roll 3
A back coat layer was formed thereon. At this time, the traveling speed of the nonmagnetic support 4 was set to 10 m / min. During the formation of the back coat layer, oxygen gas was introduced at 230 SCCM from the nozzles 10 and 10 ′. Further, both surfaces of the protective layer and the back coat layer on the magnetic layer were coated with a fluorine-based lubricant so that the thickness of the lubricating layer was 40 ° to form a lubricating layer. The obtained product was cut into a width of 8 mm and loaded into a cassette to produce an 8 mm video cassette. The cross section of the obtained magnetic recording medium and the structure of the back coat layer are T
According to the EM photograph or the electron beam diffraction, as shown in FIG. 2A, the inclination of the column of the backcoat layer and the inclination of the column of the magnetic layer are in opposite directions, and the inclination of the column of the backcoat layer is opposite. The thickness decreased as the distance from the nonmagnetic support increased. The thickness of the back coat layer is 2000mm
Met.

Example 2 On the same non-magnetic support as in Example 1, a back coat layer was formed on the surface of the non-magnetic support opposite to the magnetic layer using the vapor deposition apparatus shown in FIG. 2 × 10 ⁻⁵ To in the vacuum chamber 2
After evacuating to rr, output 15 kW by electron gun 8
Then, the metal Al in the crucible 7 was irradiated with an electron beam to make a vapor atmosphere. The nonmagnetic support 4 was passed from the roll 5 to the roll 6 through the cooling can roll 3, and a back coat layer was formed on the cooling can roll 3. At this time, the running speed of the non-magnetic support 4 was 12 m / min. At the time of forming the back coat layer, oxygen gas was introduced at 180 SCCM from the nozzles 10 and 10 ′, respectively. In order to form two back coat layers, a back coat film forming step under the same conditions was performed twice. Further, both surfaces of the protective layer and the back coat layer on the magnetic layer were coated with a fluorine-based lubricant so that the thickness of the lubricating layer was 40 ° to form a lubricating layer. The obtained product was cut into a width of 8 mm and loaded into a cassette to produce an 8 mm video cassette. The cross section of the obtained magnetic recording medium and the structure of the back coat layer are as shown in FIG. 2B according to the TEM photograph or the electron beam diffraction, and each of the back coat layers formed from the two thin films is used. The inclination of the column of the magnetic layer and the inclination of the column of the magnetic layer were in opposite directions, and the thickness of the column of the back coat layer increased as the distance from the non-magnetic support increased. The thickness of the back coat layer was 2600 °.

Example 3 On the same non-magnetic support as in Example 1, a back coat layer was formed on the surface of the non-magnetic support opposite to the magnetic layer using the vapor deposition apparatus 11 of FIG. 2 × 10 in vacuum chamber 12
After evacuation to ^-5 Torr, the Cu-Al alloy in the crucible 17 was irradiated with an electron beam at a power of 20 kW by an electron gun 18 to form a steam atmosphere. The non-magnetic support 4 was moved from the unwind roll 15 to the take-up roll 16 via the guide rolls 13 and 13 ', and a back coat layer was formed between the guide rolls 13 and 13'. Non-magnetic support 4
The running speed was 9 m / min. At the time of the back coat film formation, oxygen gas was supplied from the nozzles 20 and 20 'respectively.
Introduced at 10 SCCM. Further, both surfaces of the protective layer and the back coat layer on the magnetic layer were coated with a fluorine-based lubricant so that the thickness of the lubricating layer was 40 ° to form a lubricating layer. The obtained product was cut into a width of 8 mm and loaded into a cassette to produce an 8 mm video cassette. The cross section of the obtained magnetic recording medium and the structure of the back coat layer are as shown in FIG. 2C according to the TEM photograph or the electron beam diffraction, and the inclination of the column of the back coat layer and the column of the magnetic layer are shown. The inclination was in the opposite direction, and the thickness of the column of the back coat layer was constant even when separated from the nonmagnetic support. The thickness of the back coat layer was 2500 °.

Comparative Example 1 On the same non-magnetic support as in Example 1, a back coat layer was formed on the surface of the non-magnetic support opposite to the magnetic layer using the vapor deposition apparatus 21 of FIG. 2 × 10 in the vacuum chamber 22
After evacuation to ^-5 Torr, the electron beam was applied to the metal Al in the crucible 27 at an output of 11 kW by an electron gun 28 to form a vapor atmosphere. The non-magnetic support 4 was moved from the unwinding roll 25 to the take-up roll 26 through the cooling can roll 23 to form a back coat layer on the cooling can roll 23. The running speed of the nonmagnetic support 4 was 16 m / min. At the time of forming the back coat, oxygen gas was introduced from the nozzle 30 at 120 SCCM. Further, both surfaces of the protective layer and the back coat layer on the magnetic layer were coated with a fluorine-based lubricant so that the thickness of the lubricating layer was 40 ° to form a lubricating layer. The obtained product was cut into a width of 8 mm and loaded into a cassette to produce an 8 mm video cassette. The cross section of the obtained magnetic recording medium and the structure of the back coat layer were as shown in FIG. 5 according to a TEM photograph or electron beam diffraction, and the back coat layer was formed of a thin film having no clear structure. . The thickness of the back coat layer was 2000 °.

Performance Evaluation The envelope characteristics of the output waveforms of the magnetic recording media obtained in Examples and Comparative Examples were measured by using a device modified from a commercially available 8 mm VTR device. Although the envelope characteristic waveform as shown in FIG. 6A is ideal, the waveform is actually chipped as shown in FIG. Here, the envelope characteristic was obtained by subtracting, from the 100%, the higher chipping rate of the front chipping or the rear chipping at the time of measurement. Table 1 shows these results.
Shown in

[0019]

[Table 1]

[0020]

According to the present invention, since the cupping of the support can be prevented, a better head touch than before can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of an apparatus that can be used for manufacturing a magnetic recording medium of the present invention.

FIG. 2 is a model diagram showing a structure of a surface of a magnetic recording medium obtained by the present invention, the surface being parallel to the longitudinal direction of the non-magnetic support and perpendicular to the surface of the non-magnetic support.

FIG. 3 is a schematic view showing another example of an apparatus that can be used for manufacturing the magnetic recording medium of the present invention.

FIG. 4 is a schematic view of an apparatus used for manufacturing a conventional magnetic recording medium.

FIG. 5 is a model diagram showing a structure of a surface of a conventional magnetic recording medium which is parallel to the longitudinal direction of the non-magnetic support and perpendicular to the surface of the non-magnetic support.

FIG. 6 is a model diagram showing a missing rate of an envelope waveform.

[Explanation of symbols]

 1, 11, 21 Vacuum evaporation apparatus 2, 12, 22 Vacuum chamber 3, 23 Cooling can 4 Non-magnetic support 5, 6, Roll 7, 17, 27 Crucible 8, 18, 28 Electron gun 9, 9'19, 19 ' 29 Prevention plate 10, 10'20, 20'30 Nozzle 13, 13 'Guide roll 15, 25 Unwind roll 16, 26 Take-up roll

Claims (9)

[Claims] In a magnetic recording medium having one or more magnetic layers having a column structure inclined in the same direction formed by vapor deposition on a nonmagnetic support, the magnetic recording medium is opposite to the magnetic layer of the nonmagnetic support. Characterized in that at least one backcoat layer is formed by vacuum film formation on the surface, and the backcoat layer is formed of a thin film composed of a column inclined in a direction opposite to the inclination of the column of the magnetic layer. Magnetic recording medium. 2. The thickness of a column of the back coat layer in a plane parallel to the longitudinal direction of the non-magnetic support and perpendicular to the surface of the non-magnetic support is from the surface of the back coat layer to the non-magnetic support. 2. The magnetic recording medium according to claim 1, wherein the magnetic recording medium gradually changes in a depth direction. 3. The thickness of a column of the back coat layer in a plane parallel to the longitudinal direction of the non-magnetic support and perpendicular to the surface of the non-magnetic support is from the surface of the back coat layer to the non-magnetic support. 2. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is constant in a depth direction. 4. The method according to claim 1, wherein the back coat layer is a metal or metalloid, or is one of an oxide, a nitride, and a carbide of the metal or metalloid. Magnetic recording medium. 5. The metal constituting the back coat layer is A
The magnetic recording medium according to claim 4, wherein the magnetic recording medium further comprises l. 6. The film thickness Tbc of the back coat layer and the film thickness Tm of the magnetic layer have a relationship represented by the following equation.
The magnetic recording medium according to any one of claims 1 to 5, wherein Tbc = Tm ± 2000Å 7. The magnetic recording medium according to claim 1, wherein a lubricating layer exists on the back coat layer. 8. The magnetic recording medium according to claim 1, wherein a protective layer and a lubricating layer are present on the back coat layer. 9. The magnetic recording medium according to claim 1, wherein the thickness of the nonmagnetic support is 4.5 μm or less, and the total thickness of the magnetic recording medium is 6.0 μm or less.
The magnetic recording medium according to any one of claims 1 to 8, wherein