JPH10105947A - Thin film magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium having excellent running property by using a plastic film having specific resiliency expressed by stiffness and specific film thickness as a support. SOLUTION: A magnetic layer is formed on one surface of the plastic film having <=6×10<-3> N/μm<2> stiffness per 1μm thickness and 3.0-4.5μm thickness by vacuum film-forming method and a back coat layer is formed on the opposite surface of the magnetic layer on the film. As a result, the magnetic recording medium capable of keeping excellent running property is obtained by giving the adequate stiffness to the whole magnetic recording medium without using an aramid or the like, which is higher in stiffness, but extremely expensive.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a magnetic recording medium. More specifically, a film having a thickness of 3.0 μm having a stiffness of 6 × 10 ⁻³ N / μm ² or less in a film having a thickness of 1 μm.
The present invention relates to a magnetic recording medium exhibiting good running properties by using a plastic film of about 4.5 μm and forming a magnetic layer on one surface of a plastic film and a back coat layer on the other surface in a vacuum. .

[0002]

2. Description of the Related Art High-density recording and miniaturization of magnetic recording media, especially magnetic tapes, have been progressing remarkably in recent years. Along with this, there is a demand for thinner supports for magnetic tapes or thinner layers such as magnetic layers constituting the magnetic tape. For example, as a support for a magnetic recording medium, a non-magnetic support such as a plastic such as polyethylene terephthalate (PET) is widely used, and its thickness is, for example, about 15.0 μm for a VHS type video tape, and 8 mm video tape. About 9.0 μm for DVC and 6.3 μm for DVC
As the high-density recording progressed, the thickness of the support became thinner. On the other hand, as for the magnetic layer, in the conventional method for producing a magnetic recording medium, a simple and high-productivity coating method has been mainly used. However, there is a limit in increasing the recording density because the coating method includes a binder, and as the demand for high-density recording for a magnetic recording medium increases, the mainstream has shifted to a vacuum film forming method such as evaporation without a binder. It has moved. The metal thin film type magnetic recording medium formed by the vacuum film forming method has a large amount of a magnetic substance per unit volume and can be reduced in film thickness, so that the recording density of the magnetic recording medium can be increased and the size can be further reduced. It is considered to be promising.

On the side of the support opposite to the magnetic layer,
The back coat layer is formed for the reasons of preventing adhesion of dust by an antistatic effect, good running stability obtained by controlling surface properties, and preventing occurrence of warpage by balancing with the magnetic layer side. . Conventionally, the method of applying also in the formation of the back coat layer has been the mainstream,
Due to the presence of the binder, there were problems that the back coat layer could not obtain sufficient conductivity, the support had to be exposed to the air during the process, and dust adhered. In the method of forming the back coat layer by a vacuum film forming method, the problems such as the conductivity and adhesion of dust, which were problems in the above coating method, could be improved, but the surface of the back coat layer became too smooth. However, it is difficult to provide sufficient hardness to the back coat layer, the end face of the support is deformed in a wave shape, and sufficient conductivity cannot be obtained when forming a semi-metal in a vacuum. I was In order to solve the above problems, the applicant of the present invention has proposed that a back coat layer is formed of two or more layers of metal or semi-metal to have appropriate surface properties and elasticity.
No. 53 proposes that a backcoat layer is formed by a carbon-based film to have sufficient hardness in the backcoat layer. JP-A-8-102051 proposes to suppress deformation of the end face of the support by the
Japanese Patent Application Laid-Open No. 7-9883 proposes to improve the conductivity of a back coat layer by vacuum-depositing a metalloid and impurities.
No. 0.

[0004]

In the future, higher density recording and smaller size are desired for magnetic recording media, and it is considered that the thickness of the support and the thickness of the magnetic layer will be reduced. By the way, in order to realize a good head touch and a good running property, a magnetic recording medium having an appropriate stiffness must be obtained. For example, in response to recent demands for miniaturization of magnetic recording media, when the thickness of the support is reduced, the stiffness of the support as a whole is sharply reduced, resulting in a problem such as a decrease in output due to poor head touch and deterioration in running performance. It became so. In particular, the stiffness per μm is 6
A plastic film having a low elasticity of × 10 ⁻³ N / μm ² or less, for example, polyethylene terephthalate which is widely used as a support of a magnetic recording medium and has a thickness of 3.0 to 3.0.
The problem was noticeable with the 4.5 μm support. Where 1
A highly elastic plastic film having a stiffness per μm larger than 6 × 10 ⁻³ N / μm ² may be used. Such a film is, for example, aramid, but the price of aramid is currently widely used. 10 times or more of polyethylene terephthalate, which is very expensive. Conversely, even if the stiffness of the support as a whole is too large, good head touch and running performance cannot be obtained.

[0005] Further, the metal thin film has strong elasticity because it does not contain a binder. In recent years, as described above, the back coat layer on the surface opposite to the magnetic layer on the support has also been formed by a vacuum film forming method. According to the above proposal, the surface property or hardness of the back coat layer has been improved, and at the same time, the strong elasticity of the back coat layer has become apparent.

[0006] In the future, it is expected that the size of the magnetic recording medium itself will be further reduced and the density of the magnetic recording medium will be further increased, and it is expected that the thickness of the support will be further reduced.
Therefore, in the present invention, in view of the above problems, a vacuum film is formed on one surface of a plastic film having a stiffness per 1 μm of 6 × 10 ⁻³ N / μm ² or less and a thickness of 3.0 to 4.5 μm. By forming the magnetic layer by a vacuum coating method on the surface of the film opposite to the magnetic layer by a vacuum coating method, the magnetic recording medium as a whole has an appropriate stiffness. It is an object of the present invention to obtain a magnetic recording medium capable of maintaining good running properties without using expensive aramid or the like.

[0007]

Means for Solving the Problems In view of the above situation, the present inventors have formed a magnetic layer and a back coat layer by a vacuum film forming method using a support having a thickness of 3.0 to 4.5 μm. As a result of researching to provide a magnetic recording medium that can prevent distortion of the support even when formed and has good running properties, the stiffness of a film having a thickness of 1 μm is 6 × 10 ⁻³ N.
/ Μm ² or less by forming a magnetic layer on one surface of a plastic film having a thickness of 3.0 to 4.5 μm and a back coat layer on the other surface by a vacuum film forming method. The inventors have found that the object can be achieved, and have completed the present invention.

The support used in the present invention is characterized by its elasticity. That is, the support used in the present invention is a plastic film of 3.0 to 4.5 μm, and the stiffness of the film at a thickness of 1 μm is 6 × 10 ⁻³ N / μm ² or less. The stiffness is a value for evaluating the elasticity of the film. Generally, the stiffness is a value obtained by measuring a tensile force-elongation curve of the film and obtaining the inclination of an initial linear portion of the curve. The support used in the present invention is not limited as long as it is a plastic film having the above-mentioned thickness and stiffness.Polyolefins such as polyester, polyethylene and polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, polycarbonate and polychloride Use of various plastics such as vinyl, polyimide, and aromatic polyamide can be considered. However, the use of polyethylene terephthalate (PET) is particularly preferred in terms of price. In addition, a filler may be added to the plastic film in order to make the elasticity expressed by the stiffness of the support to a desired value. The filler added to the film is beads such as SiO ₂ , ZnO, Al ₂ O ₃ , and plastic, and is added to the film by performing a heat treatment or a pressure treatment. It is particularly preferable that the diameter of the filler to be added is 15 nm or less. Further, the filler may be unevenly distributed in the vicinity of the surface in the plastic film or may be randomly present in the plastic film.

In the present invention, the magnetic layer is formed by a vacuum deposition method such as ordinary vapor deposition or 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, ferromagnetic metals such as Co, Ni, and Fe, or Fe-Co, Fe-Ni, Co-Ni, and 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, a ferromagnetic alloy mainly containing Co, Ni, and Fe and at least one selected from oxides, nitrides, and carbides thereof are preferable. Further, in the present invention, good running properties can be realized by changing the number and thickness of the thin films forming the magnetic layer. Any of the materials, nitrides and carbides can be used. The durability can be improved by introducing an oxidizing gas at the time of vacuum film formation to form an oxide layer on the surface of the magnetic layer. The magnetic layer formed by the vacuum film formation method 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. It is preferable that the magnetic layer of the magnetic recording medium is formed on the non-magnetic support by oblique evaporation. The method of oblique deposition is not particularly limited, and follows a conventionally known method.
The thickness of the metal thin-film type magnetic layer is not limited.
000 [deg.] Is preferable, and a practical range of 800 to 3 is particularly preferable.
000 ° is preferred. In the case of two layers, the lower layer is 20
The upper layer is preferably about 100-1000 °, and in the case of three layers, the lower layer is about 200-2000 °, the middle layer is about 200-2000 °, and the upper layer is 100-1.
It is preferably about 000 °.

The back coat layer in the present invention is formed of at least one thin film on the surface of the support opposite to the magnetic layer by a usual vacuum film forming method. In particular, for the purpose of improving the elasticity of the back coat layer, it is preferably formed of two or more thin films. The back coat layer is a metal or semi-metal or an oxide, nitride, or metal or semi-metal obtained by adhering it on a support by a method such as evaporating a metal or semi-metal by irradiating an electron beam in a vacuum chamber. It is formed by an oxide. As a material for forming the back coat layer, Al, C if a metal is used.
u, Zn, Sn, Ni, Ag, and the like and alloys thereof can be considered. In particular, a Cu-Al alloy is preferable from the viewpoint of cost, adhesion rate, and stability after oxidation. If it is a semi-metal,
i, Ge, As, Sc, Sb, etc. can be considered. It is preferable to add an additive in order to further improve the conductivity. Further, Si is particularly preferable in terms of cost and deposition rate. In addition, it is also preferable to perform one or more reactions of oxidation, nitridation, and carbonization when vacuum-forming these metals or metalloids to form oxide films, nitride films, carbonized films, and composite films thereof. Further, in the present invention, since good running properties can be realized by changing the number and thickness of the thin films forming the magnetic layer, the above-mentioned metals and metalloids or oxides and nitrides thereof are used. And carbides can be used. The back coat layer may be formed before or after the magnetic layer is formed.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The magnetic recording medium of the present invention is characterized in that a plastic film having elasticity and film thickness expressed by the above-mentioned stiffness is used as a support, and one of the plastic films is used. A magnetic layer on the surface,
A back coat layer is formed on the other surface by vacuum film formation.

FIG. 1 shows an example of a vapor deposition apparatus 1 suitable for manufacturing a thin film magnetic recording medium obtained by the present invention. The same apparatus can be used when forming the magnetic layer and when forming the back coat layer. Here, the case of forming a magnetic layer will be described. The vacuum chamber 2 of the vapor deposition device 1 is connected to a vacuum exhaust device not shown here. A cooling can roll 3 is provided in the vacuum chamber 2.
And an unwind roll 5 and a take-up roll 6 for running a support 4 such as a plastic film on the cooling can roll 3. A crucible 7 is disposed below the cooling can roll 3 as an evaporation source, and a magnetic material such as metallic cobalt is contained in the crucible 7. An electron gun 8 is arranged in the vacuum chamber 2 and irradiates the crucible 7 with an electron beam to evaporate metallic cobalt in the crucible 7. Above the crucible 7,
Prevention plates 9 and 9 ′ for limiting the incident angle of the metal cobalt vapor from the crucible 7 evaporated by the electron beam irradiation toward the cooling can roll 3 to the support 4 are arranged so that oblique deposition can be performed. . A nozzle 10 for supplying oxygen gas is disposed immediately above the deposition-preventing plate 9.

In both cases of forming the magnetic layer and the back coat layer, the same operation is performed using the vapor deposition apparatus 1 as shown in FIG. Can be formed. Here, the case of forming a magnetic layer will be described. After the inside of the vacuum chamber 2 is evacuated to a predetermined degree of vacuum by the evacuation device, the support 4 is run from the unwind roll 5 onto the cooling can roll 3. At this time, the support may or may not have a back coat layer formed in advance. The electron gun 8 irradiates the crucible 7 with an electron beam, melts and evaporates the metal cobalt in the crucible 7, and performs vapor deposition on the support 4. This is performed in the presence of oxygen supplied from the nozzle 10. Support 4 treated in this way
Is taken up by a take-up roll 6. When a magnetic layer having a multilayer structure is formed, a plurality of vapor deposition apparatuses 1 as shown in FIG. 1 may be connected and formed continuously, or may be formed by repeating vapor deposition multiple times in the vapor deposition apparatus 1. Is also good.

After forming a necessary magnetic layer on the support and a necessary back coat layer on the surface opposite to the magnetic layer on the support, if necessary, a protective layer and a lubricating layer may be formed on the respective layers. Layers can be formed. The protective layer is formed by forming a high-hardness thin film such as diamond-like carbon by a CVD method or a PVD method. The lubrication layer is
It is formed by applying a fluorine-based lubricant such as perfluoropolyether 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, and the product is commercialized as, for example, an 8 mm video tape.

[0015]

【Example】

Example 1 Fine particles of SiO _{2 having} a diameter of 10 nm were 1 μm as a filler.
3.8 μm thick containing 200 pieces per m ^{3 and having a} stiffness of 4.5 × 10 ⁻³ N / μm ² at a thickness of 1 μm.
A thin film magnetic recording medium was formed using polyethylene terephthalate as a support. On this support, a magnetic layer and a back coat layer were formed using the vapor deposition apparatus 1 of FIG. The formation of the magnetic layer is as follows. The degree of vacuum in the vacuum chamber 2 is reduced to 2 × 10 ⁻⁵ Torr by a vacuum exhaust device.
After that, the metal cobalt in the crucible 7 was irradiated with an electron beam at an output of 15 kW by the electron gun 8 to make a metal cobalt vapor atmosphere. The support 4 was passed from the unwinding roll 5 to the take-up roll 6 through the cooling can roll 3, and a magnetic layer thin film was formed on the cooling can roll 3. At this time, the traveling speed of the support 4 was 1.2 m / min.
During the film formation, oxygen gas was introduced from the nozzle 10 at 30 SCCM. Subsequently, a back coat layer was formed on the surface of the support opposite to the magnetic layer. After evacuating the vacuum chamber 2 to 3 × 10 ⁻⁵ Torr as in the case of forming the magnetic layer,
The metal cobalt in the crucible 7 was irradiated with an electron beam at a power of 15 kW by the electron gun 8 to make a metal cobalt vapor atmosphere. The support 4 was passed from the unwinding roll 5 to the take-up 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 traveling speed of the support 4 was set to 2.0 m / min,
More oxygen gas was introduced at 40 SCCM. Further, a diamond-like carbon film was formed on the magnetic layer at a thickness of 100 ° to form a protective layer. Further, a fluorine-based lubricant was coated on the protective layer and the back coat layer on the magnetic layer so that the thickness of the lubricant layer became 20 ° to form a lubricant layer. The obtained one was cut into a width of 8 mm and loaded into a cassette to prepare an 8 mm video cassette. The obtained thin-film magnetic recording medium had a magnetic layer of 1500 ° and a backcoat layer of 1600 °. The magnetic characteristics are as follows: coercive force (Hc) is 1440 Oe, saturation magnetic flux density (Bs) is 5900 G, squareness ratio (Br / B
s) was 0.95.

Example 2 A magnetic layer of metallic cobalt was formed on the support used in Example 1 under the same conditions as in Example 1. Subsequently, a back coat layer was formed on the surface of the support opposite to the magnetic layer using the vapor deposition apparatus 1 of FIG. 3 × 10 in vacuum chamber 2
After evacuating to ^-4 Torr, output 2 by electron gun 8
At 0 kW, the silicon in the crucible 7 was irradiated with an electron beam to form a silicon vapor atmosphere. The support 4 ran from the unwinding roll 5 on the cooling can roll 3 to the take-up roll 6. At this time, the running speed of the support 4 was set at 3.0 m / min, and oxygen gas was introduced from the nozzle 10 at 50 SCCM to form a SiO ₂ back coat layer on the cooling can roll 3. Further, a diamond-like carbon film was formed on the magnetic layer at a thickness of 110 ° to form a protective layer.
Further, a fluorine-based lubricant was coated on the protective layer and the back coat layer on the magnetic layer so that the thickness of the lubricating layer was 12 ° to form a lubricating layer. The obtained one was cut into a width of 8 mm and loaded into a cassette to prepare an 8 mm video cassette. The obtained thin film magnetic recording medium has a magnetic layer of 1500
Å, the back coat layer was 2,000 Å.

Example 3 A magnetic layer of metallic cobalt was formed on the support used in Example 1 under the same conditions as in Example 1. Subsequently, two backcoat layers were formed on the surface of the support opposite to the magnetic layer using the vapor deposition apparatus 1 of FIG. 5 in the vacuum chamber 2
After evacuating to ^10-5 Torr, the electron gun 8 irradiates the silicon in the crucible 7 with an electron beam at an output of 20 kW to form a silicon vapor atmosphere. The support 4 passes from the unwinding roll 5 onto the cooling can roll 3, and
Was driven to. At this time, the running speed of the support 4 is 4.
0 m, and oxygen gas is introduced from the nozzle 10 at 40 SCCM, so that Si
Was formed as a first layer. Subsequently, similarly, the inside of the vacuum chamber 2 is set to 1 × 10 ⁻⁴ Torr.
After evacuation, the silicon inside the crucible 7 was irradiated with an electron beam at an output of 20 kW by the electron gun 8 to form a silicon vapor atmosphere. The support 4 ran from the unwinding roll 5 on the cooling can roll 3 to the take-up roll 6. At this time, the traveling speed of the support 4 was 3.5 m / min,
By introducing oxygen gas from 0 at 40 SCCM,
A back coat layer of SiO _{2 was formed} on the cooling can roll 3 and used as a second layer. Further, a diamond-like carbon film was formed on the magnetic layer by 90 ° to form a protective layer. Further, a fluorine-based lubricant was coated on the protective layer and the back coat layer on the magnetic layer so that the thickness of the lubricant layer became 10 ° to form a lubricant layer. The obtained one was cut into a width of 8 mm and loaded into a cassette to prepare an 8 mm video cassette. The obtained thin film magnetic recording medium has a magnetic layer of 15
00 °, the backcoat layer first layer was 1000 °, and the backcoat layer second layer was 1000 °.

Example 4 A thin-film magnetic recording medium using 3.8 μm thick polyethylene terephthalate as a support, in which no filler is contained in the film and the stiffness at a thickness of 1 μm is 4.1 × 10 ⁻³ N / μm ^2. Was formed. On this support, a magnetic layer and a back coat layer were formed using the vapor deposition apparatus 1 of FIG. The formation of the magnetic layer is as follows. The degree of vacuum in the vacuum chamber 2 is reduced to 3 × 10
After the pressure was set to ^-5 Torr, the metal cobalt in the crucible 7 was irradiated with an electron beam at an output of 16 kW by the electron gun 8 to make a metal cobalt vapor atmosphere. The support 4 is an unwinding roll 5
, And passed over the cooling can roll 3 to the take-up roll 6 to form a magnetic layer thin film on the cooling can roll 3. At this time, the traveling speed of the support 4 is 1.4 m / min.
And 33 SCC oxygen gas from nozzle 10 during film formation
M introduced. Subsequently, a back coat layer was formed on the surface of the support opposite to the magnetic layer. As in the case of forming the magnetic layer, the inside of the vacuum chamber 2 is evacuated to 2 × 10 ⁻⁴ Torr, and the electron gun 8 irradiates the metal cobalt in the crucible 7 with an electron beam at an output of 20 kW. Atmosphere. The support 4 was passed from the unwinding roll 5 to the take-up 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 support 4 was 1.8 m / min, and oxygen gas was introduced from the nozzle 10 at 45 SCCM. Further, a diamond-like carbon film was formed on the magnetic layer at a thickness of 105 ° to form a protective layer. Further, a fluorine-based lubricant was coated on the protective layer and the back coat layer on the magnetic layer so that the thickness of the lubricant layer became 15 °, thereby forming a lubricant layer. The obtained one was cut into a width of 8 mm and loaded into a cassette to prepare an 8 mm video cassette. The obtained thin-film magnetic recording medium had a magnetic layer of 1500 ° and a backcoat layer of 1600 °. The magnetic properties were a coercive force (Hc) of 1440 Oe, a saturation magnetic flux density (Bs) of 5900 G, and a squareness ratio (Br / Bs) of 0.95.

Example 5 A magnetic layer and a back coat layer were formed on the support used in Example 1 using an apparatus as shown in FIG. The formation of the magnetic layer is as follows. After the inside of the vacuum chamber was evacuated to 3 × 10 ⁻⁵ Torr by a vacuum evacuation device, the metal iron in the crucible 17 was irradiated with an electron beam at an output of 10 kW by an electron gun 18 to make a metal iron vapor atmosphere. The support 4 is composed of an unwinding roll and a cooling can roll 1
3 and was run to a take-up roll. At this time, the running speed of the support 4 was 0.4 m / min, and oxygen gas was introduced from the nozzle 20 at 5 SCCM. At the same time, a current of 10 A was passed through the filament, and an Fe—N magnetic film was formed on the support 4 on the cooling can roll 13 by an ion gun 21 with an acceleration voltage of 800 V and a nitrogen gas flow rate of 10 SCCM. The back coat layer was formed using an apparatus as shown in FIG. 2 in the same manner as when the magnetic film was formed. After the inside of the vacuum chamber was evacuated to 4 × 10 ⁻⁵ torr, the electron beam was applied to the metal aluminum in the crucible 17 by the electron gun 18 at an output of 6 kW to form a metal aluminum vapor atmosphere. The support 4 passed from the unwinding roll to the take-up roll through the cooling can roll 13. At this time, the running speed of the support 4 was 0.8 m / min. At this time, a current of 10 A is supplied to the filament, and the accelerating voltage is set to 80.
Ion gun 2 with 0 V and nitrogen gas flow rate of 10 SCCM
1 allows Al- to be deposited on the support 4 on the cooling can roll 13.
An N back coat layer was formed. Further, a diamond-like carbon film was formed on the magnetic layer at a thickness of 110 ° to form a protective layer. Further, a fluorine-based lubricant was coated on the protective layer and the back coat layer on the magnetic layer so that the thickness of the lubricating layer was 12 ° to form a lubricating layer. The obtained one was cut into a width of 8 mm and loaded into a cassette to prepare an 8 mm video cassette. The obtained thin-film magnetic recording medium has a magnetic layer of 18
00 ° and the backcoat layer was 2000 °. The magnetic characteristics are as follows: coercive force (Hc) is 1420 Oe, saturation magnetic flux density (Bs) is 6800 G, squareness ratio (Br / Bs) is 0.7.
It was 2.

COMPARATIVE EXAMPLE 1 A thin film magnetic recording medium was prepared by using a 3.8 μm thick aramid as a support having no filler in the film and having a stiffness of 15.1 × 10 ⁻³ N / μm ² at a thickness of 1 μm. Formed. A vapor deposition device 1 shown in FIG.
Was used to form a magnetic layer. The formation of the magnetic layer is as follows. Vacuum chamber 2 by vacuum pumping device
After setting the degree of vacuum in the inside to 8 × 10 ⁻⁶ Torr, the metal cobalt in the crucible 7 was irradiated with the electron gun 8 at an output of 25 kW to form a metal cobalt vapor atmosphere. The support 4 was passed from the unwinding roll 5 to the take-up roll 6 through the cooling can roll 3, and a magnetic layer thin film was formed on the cooling can roll 3. At this time, the running speed of the support 4 was 2.1 m / min. At the time of film formation, oxygen gas was introduced from the nozzle 10 at 35 SCCM. Subsequently, a back coat layer was formed on the surface of the support opposite to the magnetic layer by a coating method. A backcoat layer was formed by applying a carbon binder such that the thickness of the backcoat layer was 0.5 μm. Further, a diamond-like carbon film was formed on the magnetic layer by 80 ° to form a protective layer. Further, a fluorine-based lubricant was coated on the protective layer and the back coat layer on the magnetic layer so that the thickness of the lubricant layer became 20 ° to form a lubricant layer. The obtained one was cut into a width of 8 mm and loaded into a cassette to prepare an 8 mm video cassette. The obtained thin film magnetic recording medium had a magnetic layer of 1500 °. The magnetic properties are as follows: coercive force (Hc) is 1440 Oe, saturation magnetic flux density (Bs) is 5900 G, and squareness ratio (Br / Bs) is 0.9.
It was 5.

Comparative Example 2 1 μm fine particles of SiO _{2 having} a diameter of 10 nm
3.8 μm thick containing 200 pieces per m ^{3 and having a} stiffness of 4.5 × 10 ⁻³ N / μm ² at a thickness of 1 μm.
A thin film magnetic recording medium was formed using polyethylene terephthalate as a support. On this support, a magnetic layer was formed using the vapor deposition apparatus 1 of FIG. The formation of the magnetic layer is as follows. After the degree of vacuum in the vacuum chamber 2 was adjusted to 2 × 10 ⁻⁵ Torr by the vacuum exhaust device, the electron beam was applied to the metal cobalt in the crucible 7 by the electron gun 8 at an output of 18 kW to form a metal cobalt vapor atmosphere. The support 4 was passed from the unwinding roll 5 to the take-up roll 6 through the cooling can roll 3, and a magnetic layer thin film was formed on the cooling can roll 3. At this time, the support 4
The traveling speed was 1.6 m / min. Nozzle 10 during film formation
More oxygen gas was introduced at 28 SCCM. Subsequently, a back coat layer was formed on the surface of the support opposite to the magnetic layer by a coating method. A backcoat layer was formed by applying a carbon binder so that the thickness of the backcoat layer was 0.6 μm. Further, a diamond-like carbon film was formed on the magnetic layer at a thickness of 110 ° to form a protective layer. Further, a fluorine-based lubricant was coated on the protective layer and the back coat layer on the magnetic layer so that the thickness of the lubricant layer became 13 ° to form a lubricant layer. The obtained one was cut into a width of 8 mm and loaded into a cassette to prepare an 8 mm video cassette. The obtained thin film magnetic recording medium had a magnetic layer of 1500 °.

Performance Evaluation The running properties of the thin-film magnetic recording media obtained in Examples and Comparative Examples were evaluated. Evaluation was made using a commercially available Hi8-V
This was performed by modifying the TR, changing the running speed to 1, 2, 3 times the conventional speed, and measuring the jitter. Table 1 shows the results.

[0023]

[Table 1]

[0024]

According to the present invention, inexpensive polyethylene terephthalate can be used as a support for a thin medium having a total thickness of 5 μm or less when used as a magnetic recording medium. A thin-film magnetic recording medium having running properties can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a schematic view showing an example of a main part of another apparatus that can be used for manufacturing the thin-film magnetic recording medium of the present invention.

[Description of Signs] 1 Vacuum evaporation device 2 Vacuum chamber 3, 13 Cooling can roll 4 Support 5 Unwind roll 6 Take-up roll 7, 17 Crucible 8, 18 Electron gun 9, 9 ', 19 Anti-adhesion plate 10, 20 Nozzle 21 ion gun

Claims (6)

[Claims] 1. A film having a thickness of 1 μm and having a stiffness of 6 × 10 ⁻³ N / μm ² or less.
A magnetic recording medium wherein a magnetic layer is formed on one side of a plastic film of 0 to 4.5 μm and a back coat layer is formed on the other side by a vacuum film forming method. 2. The magnetic recording medium according to claim 1, wherein the vacuum film forming method is a vacuum evaporation method. 3. The magnetic recording medium according to claim 1, wherein the thin film of the magnetic layer is made of a metal or at least one selected from a metal oxide, a nitride, and a carbide. 4. The magnetic recording medium according to claim 1, wherein the thin film of the back coat layer is made of a metal or metalloid, or an oxide, nitride, or carbide of the metal or metalloid. 5. The plastic film having a diameter of 1
The magnetic recording medium according to claim 1, wherein the magnetic recording medium contains a filler of 5 nm or less. 6. The magnetic recording medium according to claim 1, wherein the back coat layer is formed of at least two layers.