JP2002183938A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic tape excellent in recording and reproducing characteristics and suitable for larger capacity. SOLUTION: In the magnetic tape produced by forming a magnetic layer 2 on a nonmagnetic flexible substrate 1 and by forming a back coat layer 3 on the opposite surface of the substrate 1 to the magnetic layer forming surface, a carbon film is formed on the back coating layer 3 and the proportion of H/(C+H) in the carbon film is controlled to 30 to 50 atomic %.

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 such as a magnetic tape or a magnetic disk, and more particularly to a magnetic recording medium capable of realizing a thin magnetic recording medium for a large capacity.

[0002]

2. Description of the Related Art As is well known, a magnetic tape has a magnetic thin film and various ferromagnetic films formed on a non-magnetic flexible film substrate, and various quality tapes have been proposed and put into practical use.

In recent years, as computers have become smaller,
The capacity of magnetic recording media used in external recording devices has been rapidly increasing. As an effective method for increasing the capacity, there is a method for making the total thickness of the tape extremely thin.

Conventionally, a magnetic tape has a magnetic layer formed on a non-magnetic flexible substrate (base film) mainly made of a synthetic resin film, and a tape running system is formed on a surface of the substrate opposite to the surface on which the magnetic layer is formed. In particular, it has a configuration in which a back coat layer is formed in order to reduce friction with guide pins and cylinders and improve running properties.

[0005]

The thickest layer of the magnetic tape is the base film, and the next thickest is the back coat layer. Therefore, in order to make the tape thinner,
The base film may be made thinner. However, if the base film is simply made thinner, the rigidity of the tape becomes smaller in proportion to the cube of the thickness, and problems such as a decrease in durability arise.

For this reason, the use of a highly rigid film such as an aramid film has been considered. However, as described above, if the total tape thickness is reduced to 4.5 μm or less to increase the capacity, a highly rigid film is used. However, there is a problem that it is difficult to eliminate the influence of the decrease in rigidity even when using.

An object of the present invention is to provide a magnetic recording medium which solves such disadvantages of the prior art and is suitable for thinning without deterioration of recording / reproducing characteristics.

[0008]

In order to achieve the above object, a first means of the present invention is to form a magnetic layer on a non-magnetic flexible substrate, and to form a magnetic layer opposite to the surface of the substrate on which the magnetic layer is formed. It is intended for a magnetic recording medium having a backcoat layer formed on its surface.

Then, a carbon film is formed on at least the outermost surface of the back coat layer, and H in the carbon film is formed.
/ (C + H) is regulated in a range of 30 at% to 50 at%.

According to a second aspect of the present invention, in the first aspect, the ratio of H / (C + H + O + Si) in the carbon film is restricted to a range of 35 atomic% to 45 atomic%. Things.

According to a third aspect of the present invention, in the first or second aspect, the total thickness of the magnetic recording medium is 1 μm.
It is characterized in that it is regulated in the range of m to 4.5 μm.

According to a fourth aspect of the present invention, in the first or second aspect, the carbon film is a plasma carbon film.

According to a fifth aspect of the present invention, in the fourth aspect, the plasma carbon film is a diamond-like carbon film.

According to a sixth aspect of the present invention, in the first to fifth aspects, a light transmission suppressing layer for suppressing light transmission is formed on at least one surface of the non-magnetic flexible substrate. It is a feature.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, thinning a magnetic recording medium is an effective method for increasing the capacity of a magnetic recording medium. , The desired recording / reproducing characteristics cannot be obtained.

The inventors of the present invention have made intensive studies, and as a result, at least the outermost surface of the back coat layer is formed of a carbon film such as a plasma carbon film, and the ratio of H / (C + H) in the carbon film (hereinafter referred to as the carbon film). , The hydrogen content) in the range of 30 atomic% to 50 atomic%, even if the rigidity of the entire magnetic recording medium is slightly reduced,
It has been found that a desired recording / reproducing characteristic is obtained because the head contact is improved, and a magnetic recording medium suitable for increasing the capacity can be provided.

According to the present invention, in particular, the total thickness of the magnetic recording medium is 1 μm.
If the magnetic recording medium is restricted to a range of about 4.5 μm, it is possible to provide a magnetic recording medium having particularly excellent running properties and recording / reproducing characteristics. When the total thickness of the magnetic recording medium is less than 1 μm, the magnetic recording medium is extremely thin and too soft, making it difficult to mass-produce the magnetic recording medium in good mass production, and has a problem in running properties of the magnetic recording medium. On the other hand, if the total thickness of the magnetic recording medium exceeds 4.5 μm, the recording capacity per one turn of the magnetic recording medium is not sufficient, which is not suitable for increasing the capacity.
Therefore, it is better to restrict the total thickness of the magnetic recording medium to a range of 1 μm to 4.5 μm.

In the present invention, any conventionally used base film can be used as the flexible substrate (base film). Specifically, films such as polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins, cellulose triacetate, polycarbonate, polyamide, polyamideimide, polysulfone, polybenzoxazole, and aromatic polyamide are used.

As the magnetic layer, either a coating type magnetic layer or a metal thin film type magnetic layer can be used. As the coating type magnetic layer, for example, γ-Fe ₂ O ₃ , γ-Fe ₃ O ₄ ,
Co-containing γ-Fe ₂ O ₃ , Co-containing γ-Fe ₃ O ₄ , F
e, Co, Fe-Ni, barium ferrite, strontium ferrite and the like are used. These powders can be mixed and dispersed together with a binder resin, an organic solvent and the like to prepare a magnetic paint, applied on a base film, and dried to form a coating type magnetic layer.

As the metal thin film type magnetic layer, for example, F
e, Co, Co-O, Co-Ni, Co-Ni-O, C
o-Cr, Co-Fe, Co-Ni-Cr, Co-Pt
-Cr, Te-Fe-Co, Gd-Fe-Co, Fe-
Co, Fe-Ni, Fe-Co-Ni, Fe-Rh, C
o-P, Co-B, Co-Y, Co-La, Co-C
e, Co-Pt, Co-Mn, Co-Ni-P, Co-
Ni-B, Co-Ni-Ag, Co-Ni-Nd, Co
-Ni-Ce, Co-Ni-Zn, Co-Ni-Cu,
Co-Ni-W, Co- Ni-Re, γ-Fe 2 O 3,
Magnetic films used for ME tapes, hard disks, MO disks, and the like, such as γ-Fe ₃ O ₄ and barium ferrite, can be used, and are formed by any film forming method such as vapor deposition, ion plating, plasma CVD, and sputtering.

The metal thin film type magnetic layer may be composed of, for example, O, N, Cr, Ga, Aa, Sr, Zr, N
b, Mo, Rh, Pd, Sn, Sb, Te, Pm, R
e, Os, Ir, Au, Hg, Pb, Bi, Ta, W,
Dy, Hf, Y, La, Pr, Gd, Sm and the like may be contained in appropriate amounts.

According to the present invention, the durability is improved by forming a carbon film (plasma carbon film) as a back coat layer as described above. However, when the carbon film is thin, the light transmittance of the tape increases, and recording is performed. Depending on the playback device, the tape end may not be detected. Therefore, a light transmission suppressing layer for suppressing light transmission may be formed on the front surface, the back surface, or both surfaces of the base film.

As the light transmission suppressing layer, for example, a layer coated with a coating liquid in which light absorbing particles such as fine particle carbon black are dispersed, Al, Cu, Ni, Co, F
A vapor deposition film of a metal such as e, Si, Zn, Sn, Ti, Cr, an oxide thereof, or a mixture thereof is used.

In the magnetic recording medium of the present invention, it is possible to form a protective layer on the magnetic layer in order to further increase the durability. As the protective layer, for example, a plasma carbon film, S
An iOx film, a SiC film, a Si film and the like can be mentioned.

When a plasma carbon film is formed, methane, ethane, ethylene, acetylene,
A monomer gas composed of a hydrocarbon gas such as butane and benzene and a carrier gas such as argon, helium, neon, krypton, xenon, radon, nitrogen, hydrogen, carbon monoxide, and carbon dioxide are supplied at a predetermined ratio. In addition,
Any gas introduction method and gas type may be used as long as a plasma carbon film can be formed on the magnetic layer.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an enlarged cross-sectional view of a magnetic tape according to an embodiment of the present invention, and FIG. 2 is a schematic configuration diagram of a plasma CVD apparatus for manufacturing the magnetic tape raw material.

As shown in FIG. 1, a magnetic layer 2 is formed on a base film 1 via a light transmission suppressing layer 4a.
A hard protective layer 9 is formed on the substrate. On the other hand, the light transmission suppressing layer 4 b
The back coat layer 3 is formed via the.

The surface opposite to the magnetic layer forming surface of the base film 1 on which the light transmission suppressing layers 4a and 4b, the magnetic layer 2 and the hard protective layer 9 have been formed is formed from a plasma carbon film using a plasma CVD apparatus shown in FIG. Back coat layer 3 is formed.

The base film 1 wound so that the light transmission suppressing layer 4b is on the outside is continuously fed out from the supply roll 5 and is cooled at a predetermined speed.
The film is formed while being transported along with the peripheral surface, and is sequentially wound up by a winding roll 7. Several intermediate rolls 8 are provided between the supply roll 5, the rotating drum 6, and the take-up roll 7 for guiding, and each of the intermediate rolls 8 is insulated from the ground in high frequency.

From the gas inlet 11, a monomer gas composed of a hydrocarbon gas such as methane and a carrier gas such as hydrogen are supplied at a predetermined ratio. These gases are kept in a plasma state by microwaves (MW) applied from the microwave linear applicator 12. A self-bias voltage is applied to the rotating drum 6 by a high frequency power supply 14 via a matching box 13 so that the conveyed base film 1 (light transmission suppressing layer 4
b) Backcoat layer 3 made of plasma carbon film on top
Are formed continuously and uniformly in a wide width.

A transfer chamber 1 which is a transfer system for the base film 1
5 and the degree of vacuum in the film forming chamber 16 for forming a film can be controlled independently, and the transfer chamber 15 is maintained at a high degree of vacuum where no plasma is generated. In the figure, reference numeral 17 denotes the transfer chamber 15 and the film formation chamber 1
6 is an intermediate room provided between them.

In the present invention, the back coat layer 3 is made of a plasma carbon film, and the plasma carbon film contains hydrogen at a predetermined ratio. The adjustment is performed by adjusting the ratio of the introduced hydrogen gas and the bias voltage at the time of film formation.

Next, examples will be specifically described. (Example 1) A polybenzoxazole (PBO) film having a thickness of 1.0 µm was used as a base film 1,
Ti was vapor-deposited on the front and back surfaces to form light transmission suppressing layers 4a and 4b each having a thickness of 0.2 μm. Then, a magnetic layer 2 made of Co-O and having a thickness of 0.1 μm and a hard protective layer 9 made of diamond-like carbon (DLC) having a thickness of 10 nm are formed on one of the light transmission suppressing layers 4a.

On the other light transmission suppressing layer 4b of the base film 1 on which the respective layers are formed as described above, the microwave frequency is 2.45 GHz, the input power is 3 kW, the transfer chamber 15
The plasma carbon (DLC) film was formed by setting the degree of vacuum of 5 × 10 ⁻⁵ Torr, the degree of vacuum of the film forming chamber 16 to 0.03 Torr, the volume ratio of methane and hydrogen of the introduced gas to 1: 2, and the bias voltage to 250 V. A back coat layer 3 having a thickness of 40 nm was formed.

After applying a fluororesin-based lubricant to both the front and back surfaces of the magnetic tape raw material thus obtained, the width is 6.
It was slit to 4 mm to produce a magnetic tape for DVC.

(Example 2) Thickness 3 with no Ti deposited
A magnetic tape was produced in the same manner as in Example 1 except that μm polyethylene naphthalate (PEN) was used as a base film, the volume ratio of methane and hydrogen was 1: 3, and the bias voltage was 350 V.

(Example 3) Thickness 4 in which Ti is not deposited
A magnetic tape was produced in the same manner as in Example 1 except that μm polyethylene naphthalate (PEN) was used as a base film, the volume ratio of methane and hydrogen was 1: 1 and the bias voltage was 350 V.

(Example 4) Thickness 4 in which Ti is not deposited
A magnetic tape was produced in the same manner as in Example 1 except that μm polyethylene naphthalate (PEN) was used as a base film.

Example 5 Example 3 except that the volume ratio of methane and hydrogen was 2: 3 and the bias voltage was 270 V.
A magnetic tape was produced in the same manner as described above.

Example 6 The volume ratio of methane to hydrogen was 1:
3. A magnetic tape was produced in the same manner as in Example 3 except that the bias voltage was 230 V.

(Comparative Example 1) Thickness 3 with no Ti deposited
A magnetic tape was produced in the same manner as in Example 1 except that μm polyethylene naphthalate (PEN) was used as a base film, the volume ratio of methane and hydrogen was 2: 1 and the bias voltage was 500 V.

(Comparative Example 2) Thickness 3 on which Ti was not deposited
A magnetic tape was produced in the same manner as in Example 1, except that μm polyethylene naphthalate (PEN) was used as a base film, the volume ratio of methane and hydrogen was 1: 3, and the bias voltage was 50 V.

(Comparative Example 3) A 3.5 μm-thick polyethylene naphthalate (PEN) film having no Ti deposited thereon was used as a base film, and a 0.5 μm-thick coating type was used instead of a plasma carbon film as a back coat layer. A magnetic tape was produced in the same manner as in Example 1 except that the back coat layer was formed.

The coating type back coat layer was prepared by coating the following coating composition for a back coat layer with a residence time of 45 minutes in a sand mill.
After dispersion in minutes, 8.5 parts by weight of polyisocyanate was added to adjust the coating component for the back coat layer, and after filtration, dried on the opposite side of the magnetic layer of the magnetic tape raw material prepared above, and calendered. Was dried so as to have a thickness of 0.5 μm and dried.

(Coating component for back coat layer) Carbon black (particle size: 75 nm) 40.50 parts by weight Barium sulfate 4.05 parts by weight Nitrocellulose 28.00 parts by weight Polyurethane resin (containing SO ₃ Na group) 20.00 Parts by weight cyclohexanone 100.00 parts by weight toluene 100.00 parts by weight (Comparative Example 4) In the same manner as in Comparative Example 3 except that a polyethylene naphthalate (PEN) having a thickness of 4 μm on which Ti was not deposited was used as a base film. A magnetic tape was produced. The hydrogen content in the back coat layer of each sample [H
/ (C + H)], and the results are shown in the table below.

The hydrogen content in the back coat layer was measured by a known HFS (Hydrogen Forward Scattering Analysis) device. The system of this HFS device is 3S-R1
0, the accelerator is 3SDH Pelletron manufactured by NEC, the end station is CE & A RBS-400, the analysis conditions are He ion beam energy of 1.00 MeV, the detection angles are 30 ° (HFS), 160 ° (RBS), and the sample normal. The ion beam irradiation angle is 75 ° and the ion beam irradiation amount is 8 μc.

The recording / reproducing characteristics of each sample were measured with a commercially available DVC deck (DC3, manufactured by Sharp Corporation) modified so as to take out the output.
The values were evaluated relative to each other as 0 dB, and the results are shown in the table below. Further, the total thickness of the tape of each sample was also measured, and the results were also shown.

[0048]

【The invention's effect】

[Table 1] As is clear from this table, even if the hydrogen content in the back coat layer is low as in Comparative Example 1 or the hydrogen content in the back coat layer is high as in Comparative Example 2, Even when the coating type back coat layer is formed instead of the plasma carbon film as the back coat layer, the C / N value is low and the recording / reproducing characteristics are poor. In Comparative Example 4, the same back coat layer as that in Example 3 was used. However, the base film was thick, so the rigidity was high, and the head contact was not good. Therefore, the C / N value was lower than that in Example 3. Since it is low and the total thickness of the tape is as large as 4.61 μm, it is not suitable for increasing the capacity.

On the other hand, in the magnetic tapes of Examples 1 to 6 of the present invention, a carbon film was formed on the surface of the back coat layer, and the hydrogen content in the carbon film was 30 atomic% to 50 atomic%.
By restricting the thickness of the tape to a range of 1 atomic% (preferably 35 atomic% to 45 atomic%), the total thickness of the tape is reduced to 1 [mu] m to 4.5 [mu] m from the demand for large capacity, and the rigidity of the tape is reduced. However, since the head contact is improved, it is possible to provide a magnetic tape having recording / reproducing characteristics equal to or higher than that of a conventional thick tape.

In the above embodiment, one backcoat layer is provided. However, the backcoat layer is composed of two or more layers, and the outermost layer has a hydrogen content of 30 atomic% to 50 atomic% as described above.
The carbon film may be restricted to the range of atomic%.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a magnetic tape according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a plasma CVD apparatus for manufacturing a raw material of the magnetic tape.

[Explanation of symbols]

 Reference Signs List 1 base film 2 magnetic layer 3 back coat layer 4a, 4b light transmission suppressing layer 5 supply roll 6 rotating drum 7 winding roll 8 intermediate roll 9 hard protective layer 11 gas inlet 12 microwave linear applicator 13 matching box 14 high frequency power 15 Transfer room 16 Film formation room 17 Intermediate room

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Tetsuo Mizumura 1-1-88 Ushitora, Ibaraki City, Osaka Prefecture Inside Hitachi Maxell Co., Ltd. (72) Michio Asano 1-188 Ushitora, Ibaraki City, Osaka Prefecture No. F term in Hitachi Maxell, Ltd. (reference) 4K030 AA09 AA17 BA28 BB12 CA07 FA01 HA04 JA01 JA06 LA20 5D006 CA05 CC01 CC03 DA00 EA03

Claims (6)

[Claims] 1. A magnetic recording medium in which a magnetic layer is formed on a non-magnetic flexible substrate and a back coat layer is formed on the surface of the substrate opposite to the surface on which the magnetic layer is formed, at least the outermost of the back coat layer. A magnetic recording medium, wherein a carbon film is formed on the surface, and the ratio of H / (C + H) in the carbon film is regulated in a range of 30 at% to 50 at%. 2. The magnetic recording medium according to claim 1, wherein
The ratio of H / (C + H) in the carbon film is 35 atomic%.
A magnetic recording medium characterized in that the magnetic recording medium is restricted to a range of 45 to 45 atomic%. 3. The magnetic recording medium according to claim 1, wherein the total thickness of the magnetic recording medium is 1 μm to 4 μm.
A magnetic recording medium characterized by being restricted to a range of 5 μm. 4. The magnetic recording medium according to claim 1, wherein said carbon film is a plasma carbon film. 5. The magnetic recording medium according to claim 4, wherein
2. The magnetic recording medium according to claim 1, wherein the plasma carbon film is a diamond-like carbon film. 6. The magnetic recording medium according to claim 1, wherein a light transmission suppressing layer for suppressing light transmission is formed on at least one surface of the non-magnetic flexible substrate. Magnetic recording medium.