JP2002183937A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic tape having excellent durability and high reliability and suitable for higher 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 surface of the back coat layer 3. The proportions of H/(C+H+O+Si), O/(C+H+O+Si) and Si/(C+H+O+Si) are controlled to the ranges of 30 to 50 atomic %, 1 to 15 atomic % and 0 to 15 atomic %, respectively.

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 is formed by forming a magnetic thin film or various ferromagnetic films on a non-magnetic flexible film substrate, and various types of magnetic tapes have been proposed and put to 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, when the total thickness of the tape is reduced to 4.5 μm or less in order to increase the capacity, a highly rigid film is used. Is almost ineffective, and there is a problem in running durability.

An object of the present invention is to provide a magnetic recording medium which is excellent in durability, has high reliability, and is suitable for increasing the capacity, by overcoming such disadvantages of the prior art.

[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 magnetic layer forming surface of the substrate. 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.
The ratio of O / (C + H + O + Si) is 30 to 50 atomic%, and the ratio of O / (C + H + O + Si) is 1 to 15 atomic%.
Atomic%, the ratio of Si / (C + H + O + Si) is 0 atomic%
It is characterized by being restricted to the range of １５15 atomic%.

In a second aspect of the present invention, in the first aspect, the ratio of H / (C + H + O + Si) in the carbon film is 35 atomic% to 45 atomic%, and O / (C + H + O + S
i) 1 atomic% to 6 atomic%, Si / (C + H + O
+ Si) is regulated in a range of 5 atomic% to 10 atomic%.

According to a third aspect of the present invention, in the first or the second means, the total thickness of the magnetic recording medium is 1 μm.
It is characterized by being restricted to a 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 nonmagnetic flexible substrate. It is a feature.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, thinning of a magnetic recording medium is an effective method for increasing the capacity of the magnetic recording medium. And the durability decreases, so that desired reliability cannot be obtained.

The inventors of the present invention have made intensive studies, and as a result, the outermost surface of the back coat layer is formed of a carbon film such as a plasma carbon film.
/ (C + H + O + Si) ratio (hereinafter, referred to as hydrogen content) is 30 atomic% to 50 atomic%, and O / (C + H + O + S)
The ratio of i) (hereinafter referred to as oxygen content) is 1 atomic% to 1 atomic%.
5 atomic%, Si / (C + H + O + Si) ratio (hereinafter, referred to as
By limiting the silicon content to a range of 0 to 15 atomic%, desired durability can be obtained and reliability is high even if the rigidity of the entire magnetic recording medium is slightly reduced.
It has been found that a magnetic recording medium suitable for increasing the capacity can be obtained.

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 rotary drum 6, and the take-up roll 7 for guiding, and each of the intermediate rolls 8 is insulated from the ground at high frequencies.

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 independently controlled, 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, oxygen and silicon at a predetermined ratio. This is done by adjusting the proportions of hydrogen, oxygen and silane introduced during film formation and the bias voltage during 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
Of 3 × 10 ⁻⁵ Torr, 0.02 Torr of vacuum in the film forming chamber 16, the volume ratio of methane, hydrogen and oxygen of the introduced gas is 1: 2: 0.2, and the bias voltage is 200 V.
As thickness 4 of plasma carbon (DLC) film
A backcoat layer 3 having a thickness of 0 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 prepared in the same manner as in Example 1 except that polyethylene naphthalate (PEN) of μm was used as a base film, the volume ratio of methane, hydrogen, and oxygen was 1: 2: 0.5, and the bias voltage was 230 V. Produced.

(Embodiment 3) Thickness 3 on which Ti is not deposited
A magnetic tape was prepared 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, hydrogen, and oxygen was 1: 2: 0.1, and the bias voltage was 150 V. Produced.

(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 A magnetic tape was produced in the same manner as in Example 3, except that the volume ratios of methane, hydrogen, oxygen, and silane were set to 1: 1.5: 0: 0.3.

Example 6 A magnetic tape was produced in the same manner as in Example 3, except that the volume ratios of methane, hydrogen, oxygen, and silane were set to 1: 1.5: 0.1: 0.6.

Example 7 A magnetic tape was produced in the same manner as in Example 3 except that the volume ratios of methane, hydrogen, oxygen, and silane were set to 1: 1.5: 0.2: 0.9.

(Comparative Example 1) Thickness 3 with no Ti deposited
A magnetic tape was prepared 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, hydrogen, and oxygen was 1: 1: 0.2, and the bias voltage was 300 V. Produced.

(Comparative Example 2) Thickness 3 with no Ti deposited
A magnetic tape was prepared 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, hydrogen, and oxygen was 1: 4: 0.2, and the bias voltage was 80 V. Produced.

(Comparative Example 3) Thickness 3 in which Ti was not deposited
A magnetic tape was produced in the same manner as in Example 1 except that polyethylene naphthalate (PEN) of μm was used as a base film, the volume ratio of methane, hydrogen, and oxygen was 1: 2: 0, and the bias voltage was 200 V. .

(Comparative Example 4) Thickness 3 with no Ti deposited
A magnetic tape was prepared in the same manner as in Example 1 except that polyethylene naphthalate (PEN) of μm was used as a base film, the volume ratio of methane, hydrogen, and oxygen was 1: 2: 0.6, and the bias voltage was 200 V. Produced.

(Comparative Example 5) A 3.5 μm-thick coating type using 3.5 μm-thick polyethylene naphthalate (PEN) without Ti as a base film 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 backcoat layer was prepared by coating the following coating composition for a backcoat layer with a residence time of 45 minutes in a sand mill.
After dispersion in minutes, 8.5 parts by weight of a polyisocyanate was added to prepare a coating component for the back coat layer, and after filtration, dried on the surface of the magnetic tape raw material opposite to the surface opposite to the magnetic layer, 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 6) In the same manner as in Comparative Example 3 except that 4 μm-thick polyethylene naphthalate (PEN) having no Ti deposited thereon 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 + O + Si)], oxygen content [O / (C + H)
+ O + Si)] and silicon content [Si / (C + H)
+ O + Si)], and the results are shown in the table below.

The hydrogen content and the oxygen content in the back coat layer can be determined by a known HFS (Hydrogen Forward Scattering Analyzing).
ysis) device. The system of this HFS device is 3
S-R10, Accelerator made by NEC 3SDH Pelletro
n, end station is CE & A RBS-400,
The analysis conditions were that the He ion beam energy was 1.00 Me.
V, detection angle is 30 ° (HFS), 160 ° (RB
S), the ion beam irradiation angle from the sample normal is 75 °,
The irradiation amount of the ion beam is 8 μc.

The silicon content was measured using a known XPS device (PHI5500MC manufactured by Perkin-Elmcr, X-ray source: Mg kα400 W, analysis area: 800 μm,
The photoelectron emission angle was measured at 45 deg).

The still durability of each sample was measured with a commercially available DVC deck (DC3 manufactured by Sharp Corporation) modified so as to take out the output, and the results are also shown in the following table.
Note that the still durability in this test is the time until C / N becomes 1/2 of the initial value. Further, the total thickness of the tape of each sample was also measured, and the results were also shown.

[0052]

【The invention's effect】

[Table 1] As is clear from this table, even if the hydrogen content in the backcoat layer is low as in Comparative Example 1 or the hydrogen content in the backcoat layer is high as in Comparative Example 2, Even if the oxygen content in the back coat layer is 0 atomic%,
Even when the oxygen content in the back coat layer is high as in Comparative Example 4, even when a coating type back coat layer is formed instead of the plasma carbon film as the back coat layer as in Comparative Example 5, still durability is still high. Comparative Example 5 was particularly poor in durability. Comparative Example 6 has good still durability, but is not suitable for increasing the capacity because the total thickness of the tape is 4.61 μm.

On the other hand, in the magnetic tapes of Examples 1 to 7 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%.
Atomic% (preferably 35 to 45 atomic%), and the oxygen content is 1 to 15 atomic% (preferably 1 to 6 atomic%).
By controlling the silicon content in the range of 0 to 15 atomic% (preferably 5 to 10 atomic%), the total thickness of the tape is 1 μm to 4.
Even if the thickness is reduced to 5 μm and the rigidity of the tape is reduced, a magnetic tape having durability equal to or higher than that of a conventional thick tape can be provided.

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.
It may be a carbon film in which the atomic percentage, the oxygen content is regulated in the range of 1 to 15 atomic%, and the silicon content is regulated in the range of 0 to 15 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 supply 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 AA14 AA17 BA28 BB12 CA07 FA01 HA04 JA01 JA06 LA20 5D006 CA05 CC01 CC03 DA00 EA03 FA02

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 a surface of the substrate opposite to the surface on which the magnetic layer is formed, wherein at least the outermost layer of the back coat layer is provided. A carbon film is formed on the surface, and H / (C + H + O + S) in the carbon film is formed.
i) is 30 atomic% to 50 atomic%, and O / (C + H +
O + Si) is 1 atomic% to 15 atomic%, and Si / (C
+ H + O + Si) in a range of 0 to 15 atomic%. 2. The magnetic recording medium according to claim 1, wherein
The ratio of H / (C + H + O + Si) in the carbon film is 35 to 45 atomic%, the ratio of O / (C + H + O + Si) is 1 to 6 atomic%, and Si / (C + H + O + S).
A magnetic recording medium characterized in that the ratio of i) is regulated in the range of 5 to 10 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.