JPH11213382A - Recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the dissipation of a lubricant applied on a protective film and to improve the traveling property and durability by forming a protective film consisting of a carbon film having a specific density on a recording film. SOLUTION: The protective film is formed by forming the carbon film having a graphite bond or diamond bond on the recording film by plasma decomposition and deposition of a hydrogen carbide monomer by a CVD process or the like. At this time, the protective film having multiple pores is formed by specifying the density of the carbon film to 1.0 to 1.8 g/cm<3> . As a result, the applied lubricant molecules intrude into the pores and entangle with the pores. Even if the lubricant molecules are pulled by a magnetic head, the scraping and dissipating thereof from the surface are prevented and the accumulation of the lubricant into the pores is made possible. The lubricant is oozed on the surface from the pores in the event of the lubricant dissipation, by which the lubricant may be maintained at all times. When the density exceeds 1.8 g/cm, the pores decrease and the lubricant detaining property degrades. When the density falls below 1.0g/cm<3> , the pores increase so much that the entanglement of the lubricant is lowered and the carbon film becomes fragiled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a recording medium, and more particularly to a magnetic recording medium.

[0002]

2. Description of the Related Art Generally, a magnetic recording medium such as a magnetic tape or a floppy disk has a magnetic film provided on a polyethylene terephthalate (PET) film, for example. This magnetic film, from the coating type using a binder resin,
There is a metal thin film type that does not use a binder resin, and a magnetic recording medium in which a magnetic film is formed by wet plating means called electroless plating, or dry plating means such as vacuum deposition, sputtering or ion plating has been proposed. These magnetic recording media have a high filling density of a magnetic material and are suitable for high-density recording.

However, since the metal thin film type magnetic film does not have a lubricant inside like the coating type magnetic film, when the magnetic head repeatedly slides on the metal thin film type magnetic film, the magnetic film becomes Easily damaged. Therefore, a protective film is provided to protect the magnetic film. Various protective films have been proposed, and among them, a carbon film made of diamond-like carbon is well known.

With respect to the protective film, for example, a diamond-like carbon film alone is not sufficient, so that a lubricant film is further formed on the protective film. However, the molecules of the lubricant provided on the diamond-like carbon film are only physically attached to the diamond-like carbon film. Therefore, the lubricant is easily scraped off by contact with the magnetic head and disappears. As a result, runnability and recording / reproducing characteristics are reduced.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a recording medium which is hard to lose a lubricant provided on a protective film and has excellent running properties and durability. is there.

[0006]

An object of the present invention is to provide a recording medium having a recording film, a protective film provided on the recording film, and a lubricant film provided on the protective film. The protective film is a carbon film, and has a density of 1.0 to 1.8 g / cm ³ .

That is, when the density is 1.0 to 1.8 g / cm
³ of carbon film pores continuing from the surface (hole) is large and therefore if the lubricant is applied on the carbon film density 1.0~1.8g / cm ^3, as shown in FIG. 1, the lubricant molecules Ends of the pores enter the pores and become entangled. For this reason, even if the other end of the lubricant molecule is pulled, since one end of the lubricant molecule is entangled with the pores, it is difficult to be scraped off from the surface and disappear.
Lubricant is stored in the pores, and when the lubricant on the surface disappears,
The lubricant oozes out of the pores, and the lubricant always exists on the surface.

Here, when the density exceeds 1.8 g / cm ³ , it means that the carbon film is dense and has few pores.
As a result, the amount of lubricant molecules with one end entangled in pores is smaller, and the amount of stored lubricant is small.Therefore, more lubricant is scraped off by the magnetic head and disappears. descend. Conversely, the density is 1.0 g / cm
If it is less than ³ , the carbon film has too many pores, and one end of the lubricant molecule is entangled with the pores. However, the carbon film with too many pores is brittle, and the function as a protective film is further reduced.

Therefore, the protective film for a recording medium, especially for a magnetic film of a metal thin film type, has a density of 1.0 to 1.8 g / cm ^3.
Carbon film. In addition, more preferably, the density is 1.0 to 1.0.
It is a 1.6 g / cm ³ carbon film. In the present invention, the carbon film is formed by decomposing a hydrocarbon monomer by plasma and depositing the same. This type of carbon film has
For example, there are an amorphous carbon film (generally called a-Carbon, I-Carbon) in which carbon is connected in an amorphous state, and an amorphous carbon film (generally called a-Carbon; H) containing a relatively large amount of hydrogen and having low hardness. A particularly hard carbon film is a carbon film containing diamond bonds therein (generally referred to as diamond-like carbon (DLC)). In particular, a carbon film having a graphite bond and / or a diamond bond is preferable. Among them, the density is 1.
0 to 1.8 g / cm < ³ >, especially a density of 1.0 to 1.6 g / cm < ³ >
A cm ³ diamond-like carbon film is preferred.

The lubricant formed after the formation of the protective film is preferably a protective film, that is, one in which one end is caught in pores of the carbon film, or one that gradually exudes from the pores. Lubricants exhibiting this behavior include esters of fatty acids such as stearic acid and fatty acids such as myristic acid used in coating tapes. In particular, the molecular weight is preferably from 160 to 480, and if it is less than this, it will volatilize without permeating, and if it is more than that, it will be solidified.

Further, it is more preferable to additionally use a fluorine-based lubricant used in a conventional vapor deposition type magnetic tape. For example, HOOC-CF ₂ (OC ₂ F ₄ ) _p (OCF ₂ ) _q-
HOCH ₂ -CF, a carboxyl group-modified perfluoropolyether called OCF ₂ -COOH, F- (CF ₂ CF ₂ CF ₂ O) _n -CF ₂ CF ₂ COOH
₂ (OC ₂ F ₄ ) _p (OCF ₂ ) _q -OCF ₂ -CH ₂ OH, an alcohol-modified perfluoropolyether, or a saturated hydrocarbon group such as an alkyl group on one or a part of the molecule Or an unsaturated hydrocarbon group, an aromatic hydrocarbon group, or a compound having another functional group. Specifically, Montecatini's product name FOMBLIN Z DIAC
And FOMBLIN Z DOL, trade name Demnum SA of Daikin Industries, and the like.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A recording medium according to the present invention comprises a recording film,
In a recording medium having a protective film provided on the recording film and a lubricant film provided on the protective film,
The protective film is a carbon film, and has a density of 1.0
Ｇ1.8 g / cm ³ , especially 1.0-1.6 g / cm ³ .

Hereinafter, the recording medium of the present invention will be described in more detail. [Support] Recording film (magnetic film, especially metal thin film type magnetic film)
As the support, a known support in the technical field can be used without particular limitation. Specifically, known resins such as PET, polyethylene naphthalate (PEN), polyphenylene sulfide, polycarbonate, polyamide, polyimide, polyamide imide, polysulfone, aramid, and aromatic polyamide; metals such as aluminum and copper; paper; and ceramics Etc. can be used. The form may be any of film, tape, sheet, disk, drum and the like. Before providing the magnetic film on the support, the surface thereof may be subjected to a treatment such as corona discharge, plasma, easy adhesion, heat, dustproofing, and bombardment in the air and / or in a vacuum in advance. The thickness of the support is 1 to 300 μm,
Preferably it is 2 to 100 μm.

[Recording Film (Magnetic Film, Especially Metallic Thin Film Type Magnetic Film)] For forming the magnetic film, known metal thin film forming means can be used, but oblique evaporation is particularly preferable. (See FIG. 2 vacuum oblique deposition apparatus). In FIG. 2, 1 is a support, 2 is a cooling can roll, 3a is a supply-side roll of the support 1, 3b is a support 1
, 4 is a crucible, 5 is a ferromagnetic metal filled in the crucible 4, 6 is an electron gun, 7 is a magnet, 8 is a shielding plate, and 9 is an oxygen gas supply nozzle. These are arranged in a vacuum chamber. The oblique deposition conditions are set so that the inclination angle of the column constituting the magnetic film is, for example, 40 ° to 55 °. The setting of these conditions cannot be determined uniquely, but the angle of incidence when the metal particles adhere to the support greatly affects. For example, if the maximum angle of incidence is
0 °, and the minimum incident angle is set to 50 ° to 60 °. Further, the inside of the vacuum chamber is evacuated to 1 × 10 ⁻⁴ to 1 × 10 ⁻⁶ Torr. The traveling speed of the support 1 is 10 to 30 m / min.
Is 40-60 kw, and the supply amount of oxygen gas from the oxygen gas supply nozzle 9 is 500-800 sccm. Accordingly, a magnetic film (metal thin film type magnetic film) having a column structure in which the center is a ferromagnetic metal and the periphery is a ferromagnetic metal oxide, and the inclination angle of the column is 40 ° to 55 ° Is formed.

The metal forming the metal thin film type magnetic film includes:
For example, in addition to metals such as Fe, Co, and Ni, Co-Ni
System, Co-Pt system, Co-Ni-Pt system, Fe-Co
System, Fe-Ni system, Fe-Co-Ni system, Fe-Co-
B-based, Co-Ni-Fe-B-based, Co-Cr-based, or alloys containing a metal such as Al in these are used. Further, these oxides, nitrides, carbides and the like are also used.

The magnetic film may be composed of a single metal thin film or a laminate of two or more metal thin films. When the magnetic film is composed of two or more metal thin films,
The material of each metal thin film may be the same or different.
The above metal thin film type magnetic film has an overall thickness of 0.3 mm.
It is 1 μm to 0.5 μm. [Protective Film] A protective film is provided on the recording film (magnetic film, especially a magnetic film of a metal thin film type). The protective film has a density of 1.
0 to 1.8 g / cm ³ , especially 1.0 to 1.6 g / cm ³
Is a carbon film. In particular, a carbon film having a graphite bond and / or a diamond bond, particularly the carbon film made of diamond-like carbon, is preferable.

This carbon film is formed by decomposing hydrocarbon monomers by plasma and depositing them. For example, ECR (Electron Cyclotron)
Resonance) Plasma CVD (Chemica)
CV such as l Vapor Deposition method
It is formed by Method D. For example, an ECR plasma CVD apparatus shown in FIG. 3 is used. In FIG. 3, reference numeral 21 denotes a support provided with the magnetic film 11, reference numeral 22 denotes a cooling can roll,
23a is a supply-side roll of the support 21, and 23b is a support 2
A take-up roll 1, a vacuum tank 24, a plasma reaction tube 25, a magnet 26, a material supply nozzle 27, and a microwave waveguide 28.

Conventionally, the formation of a carbon protective film using an ECR plasma CVD apparatus has mainly focused on densification and high density. In this case, the growth rate is slowed down so that the atoms grow while taking a close-packed structure, and the substrate temperature is raised. As a result, the atoms decomposed by plasma grew while filling the surface defect portion, and a dense film was obtained. Specifically, the film was formed at a growth rate of 80 to 240 (nm · m / min) as a product of the film thickness and the tape transport speed and a substrate temperature of 5 to 60 ° C. (Japanese Patent Application No. 8-24).
43224).

In the present invention, the film forming conditions are different in order to intentionally form voids in the protective film and impregnate the lubricant, contrary to the conventional carbon protective film. Film formation rate, substrate temperature, H ₂ O, C
This is a method of controlling by adding O ₂ or the like to obtain a target film density. That is, as compared with the related art, the growth rate is increased, the substrate temperature is also reduced, the kinetic energy of plasma particles on the substrate is suppressed, and the amount of voids is controlled to be larger. Further, H ₂ O, C
Control can also be achieved by adding O ₂ . When these molecules are added, during the growth process of carbon, these particles are adsorbed on the substrate, thereby suppressing the growth of carbon and increasing the amount of voids.
In the present invention, the product of the film thickness and the tape transport speed is 3
60-980 (nmm / min), substrate temperature -30
To −8 ° C. and the amount of H ₂ O, CO _2, etc. added is 2
To 20%. Thereby, the density is 1.0 to 1.8 g.
/ Cm ^3, a carbon film, a carbon film, particularly made of diamond-like carbon is formed in particular with a graphite bond and / or diamond bond 1.0~1.6g / cm ^3.

The thickness of the protective film is 6 × 10 ⁻³ μm to 16 μm.
× 10 ⁻³ μm is preferred. [Back Film] In order to improve running properties and durability, a back film is provided on the surface of the support of the magnetic recording medium opposite to the surface on which the magnetic film is formed. As the back film, any of a coating type and a metal thin film type may be used, but a metal thin film type is preferable. Generally, a metal thin film type back film is made of A
Non-magnetic metal such as 1, Cu, Si, Fe, Mo, Mn, Zn, or their alloys, oxides, nitrides, carbides, etc., by PVD (Physical Vap)
or Deposition) means. The thickness of the metal thin film type back film is 0.1 μm to 0.1 μm.
2 μm.

[Lubricant] The lubricant may be any as long as one end is caught by the pores of the carbon film. Further, a material that can gradually exude from the pores is preferable. That is, the lubricant is, for example, selected from the group of fatty acid esters and fatty acids themselves. In particular, those having a molecular weight of 160 to 480. Specifically, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, isostearic acid, linolenic acid, linoleic acid, oleic acid, elaidic acid, behenic acid, malonic acid,
Fatty acids such as succinic acid, maleic acid, glutaric acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, oleyl oleate, isocetyl stearate, dioleyl maleate, butyl stearate, butyl palmitate, butyl myristate, Octyl myristate, octyl palmitate, amyl stearate, amyl palmitate, isobutyl oleate, stearyl stearate, lauryl oleate, octyl oleate, isobutyl oleate, ethyl oleate, ethyl stearate, isopropyl palmitate, butyl laurate, dioleyl adipate And fatty acid esters such as diethyl adipate and diisobutyl adipate.

Hereinafter, the present invention will be described with reference to specific examples.

[0023]

[Embodiment 1] Using a vacuum oblique deposition apparatus shown in FIG.
The magnetic film 11 was formed on the ET film 1. In addition, PET
The thickness of the film 1 is 6 μm, the surface roughness Ra on the side on which the magnetic film 11 is formed is 2 nm, and the surface roughness Ra on the opposite side is 5 nm.
Met.

The output of the electron gun 6 is 15 kW, the running speed of the PET film 1 is 10 m / min, the magnetic metal 5 is Co, the maximum incident angle of the magnetic metal particles is 90 °, the minimum incident angle is 60 °,
The degree of vacuum in the vacuum chamber is 3 × 10 ⁻³ Torr, the supply amount of oxygen gas from the oxygen gas supply nozzle 9 is 500 sccm, the magnetic film 11 has a column structure in which the center is Co and the periphery is Co—O. Was formed.

The thickness of the magnetic film 11 was 0.18 μm, and the inclination angle θ of the column was 47 °. The coercive force Hc is 1600 Oe and the saturation magnetic flux density Bs is 6200
G and squareness ratio Sq were 0.92. Next, the PET film 1 on which the magnetic film 11 was formed was subjected to the EC shown in FIG.
The protective film 12 was formed on the magnetic film 11 by mounting the film in an R plasma CVD apparatus.

The conditions for forming the protective film 12 are as follows.
Is 40 m / min, the temperature of the cooling can roll 22 is −20 ° C., and the vacuum tank 24 is in a state before the supply of the raw material gas.
The degree of vacuum inside is 2.0 × 10 ⁻⁶ Torr, and C ₂ H is supplied from the raw material supply nozzle 27 into the plasma reaction tube 25.
Mixed gas of ₂ and H ₂ O (C ₂ H ₂ : H ₂ O = 9: 2 (molar ratio)), the degree of vacuum in the vacuum chamber 24 is 2.0 mTorr
The mixed gas is supplied so that
It is.

The protective film 12 thus formed is made of diamond-like carbon and has a thickness of 12 ×
It was 10 ⁻³ μm. The density of the protective film 12 obtained based on information obtained by Rutherford backscattering spectroscopy (RBS method) and thickness data obtained by a transmission electron microscope is 1.6.
g / cm ³ . The density was determined by the following method. That is,
The number of carbon atoms per measurement unit area dn · tn (atoms / cm ² ) is determined by Rutherford backscattering spectroscopy. Here, dn (atoms / cm ³ ) is the number of carbon atoms per unit deposition, and tn (cm) is the film thickness.
After that, the actual film thickness tn is measured with a transmission electron microscope to obtain dn. The density (g / cm ³ ) was determined from the dn and the atomic weight of carbon atoms. The Rutherford backscattering spectrometer uses a backscattering measuring device AN-2500 manufactured by Nissin High Voltage Co., Ltd. and has an acceleration voltage of 0.5 to 2.5 M.
V, and the measurement was performed under the condition of a maximum current of 20 μA (He ⁺ ). To measure the film thickness, cut a magnetic tape sample embedded in acrylic resin with a microtome and use it with Hitachi, Ltd.
The measurement was performed at an accelerating voltage of 100 kV using H-7000 manufactured by KK.

A metal (Co) thin film (a so-called back film) 13 having a thickness of 0.15 μm was formed on the surface opposite to the magnetic film 11 by vapor deposition. Thereafter, a toluene solution obtained by diluting butyl stearate to 0.1 wt% and an average molecular weight having a hydroxyl group, a fluoroalkyl group and an alkenyl group of 8% were obtained.
A 30% fluorine-based lubricant diluted to 0.1 wt% with a toluene solution mixed at a ratio of 2: 1 (weight ratio) was ultrasonically sprayed with an ultrasonic sprayer and heated to a thickness of 2 nm. The lubricating films 14 and 15 were formed.

The raw material of the magnetic recording medium obtained as described above was cut into a predetermined width to obtain a magnetic tape.

[0030]

Example 2 A magnetic tape was obtained according to the method of Example 1. However, the conditions for forming the protective film 12 in Example 1 were changed as follows. Film forming speed; 50 m / min Can roll temperature; -10 ° C. C ₂ H ₂ : H ₂ O = 9.8: 0.2 μ wave power; 800 w Gas flow rate: 2.2 mTorr The formed protective film 12 It is made of diamond-like carbon and has a thickness of 12 × 10 ⁻³ μm.
The density of the protective film 12 obtained based on the information and the thickness data obtained by the S method was 1.3 g / cm ³ .

[0031]

Example 3 A magnetic tape was obtained according to the method of Example 1. However, the conditions for forming the protective film 12 in Example 1 were changed as follows. Film formation speed; 60 m / min Can roll temperature; -15 ° C. C ₂ H ₂ : H ₂ O = 9: 1 μ wave power; 900 w gas flow rate: 2.4 mTorr The formed protective film 12 is made of diamond-like carbon. And its thickness is 12 × 10 ⁻³ μm,
The density of the protective film 12 obtained based on the information and the thickness data obtained by the S method was 1.0 g / cm ³ .

[0032]

Comparative Example 1 A magnetic tape was obtained according to the method of Example 1. However, the conditions for forming the protective film in Example 1 were changed as follows. Film forming speed; 10 m / min Can roll temperature; -30 ° C. C ₂ H ₂ : H ₂ O = 2: 6 μ wave power; 900 w gas flow rate: 4.0 mTorr The formed protective film is made of diamond-like carbon. The thickness was 12 × 10 ⁻³ μm, and the density of the protective film obtained based on the information obtained by the RBS method and the data on the thickness was 0.8 g / cm ³ .

[0033]

Comparative Example 2 A magnetic tape was obtained according to the method of Example 1. However, the conditions for forming the protective film in Example 1 were changed as follows. Film forming speed; 2 m / min Can roll temperature; 40 ° C. C ₂ H ₂ ; 100% μ wave power; 600 w Gas flow rate: 0.2 mTorr The formed protective film is made of diamond-like carbon, and its thickness is 12 × 10 ⁻³ μm, and the density of the protective film obtained based on the information and the thickness data obtained by the RBS method was 1.9 g / cm ³ .

[0034]

Comparative Example 3 A magnetic tape was obtained according to the method of Example 1. However, the protective film is a plasma polymerized film formed by plasma polymerization using CH ₄ as a raw material, and has a thickness of 12 × 1.
The density was 0 ⁻³ μm and the density was 1.3 g / cm ³ .

[0035]

[Characteristics] Still durability of the magnetic tape obtained in each of the above examples was examined. The results are shown in Table 1. Still durability is
A modified version of a commercially available 8m VTR (EV-S900, manufactured by Sony Corporation) was used, and it was expressed by the time required for the output to decrease by 3dB from the initial value.

Table 1 Density of protective film (g / cm ³ ) Still durability (time) Example 1 1.6 5.2 Example 2 1.3 5.6 Example 3 1.0 5.0 Comparison Example 1 0.8 1.2 Comparative Example 2 1.9 3.2 Comparative Example 3 1.3 1.0 According to this, it can be seen that the material according to the present invention has excellent still durability.

That is, even if the protective film is formed of the same diamond-like carbon, if the density is out of the range of the present invention, for example, if the density is 1.9 or more, the still durability is reduced. This is probably because the lubricant applied to the surface disappeared in a short time. On the other hand, for example, even when the density is 0.8 or less, the still durability is reduced. This is because the density is small and fragile even if the protective film is formed of diamond-like carbon,
It is considered that the function as a protective film was low, and as a result, the still durability was lowered.

On the other hand, when the density is 1.0 to 1.8 g /
If the protective film is formed of ³ cm ³ diamond-like carbon, the lubricant is trapped in the pores because it has moderate pores, and it is difficult to be scraped off even by sliding the magnetic head, and the lubricant disappears. Since it is difficult and the density is not too small, it is considered to be excellent in the function as a protective film, good in running property, and excellent in still durability.

[0039]

The recording medium of the present invention has a density of 1.0 to 1.0.
Since a protective film made of a 1.8 g / cm ³ carbon film is provided, excellent running properties and excellent still durability are achieved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a protective film.

FIG. 2 is a schematic diagram of a vacuum oblique deposition apparatus.

FIG. 3 is a schematic diagram of an ECR plasma CVD apparatus.

FIG. 4 is a schematic sectional view of a magnetic tape.

[Explanation of symbols]

 Reference Signs List 1 PET film (support) 11 Magnetic film 12 Protective film 13 Metal thin film (back film) 14, 15 Lubricant film

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akira Shiga 2606 Akabane, Kaigai, Haga-gun, Tochigi Pref.

Claims (4)

[Claims] 1. A recording medium having a recording film, a protective film provided on the recording film, and a lubricant film provided on the protective film, wherein the protective film is a carbon film. And its density is 1.0
-1.8 g / cm < ³ >. 2. The recording medium according to claim 1, wherein the recording film is a metal thin film type magnetic film. 3. The recording medium according to claim 1, wherein the carbon film is a carbon film having a graphite bond and / or a diamond bond. 4. The recording medium according to claim 1, wherein the lubricant is selected from the group consisting of esters and fatty acids.