JPH1173643A - Manufacturing method of magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for obtaining a magnetic recording medium having a metal thin film type back coat layer with controlled surface properties. SOLUTION: In a vacuum vessel 1, a metal or semimetal is deposited on a support 4 while introducing an inert gas from an inert gas introduction pipe 10 to form a back coat layer on the support 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a magnetic recording medium having a back coat layer having excellent surface properties.

[0002]

2. Description of the Related Art A magnetic recording medium, for example, a magnetic tape includes:
There is a coating tape formed by applying a magnetic paint in which a magnetic powder is dispersed in a binder on a film serving as a support, and a vapor-deposited tape containing no binder formed by vapor-depositing a metal on a film in a vacuum. . The vapor-deposited tape is said to be promising for high-density recording because it can increase the density of the magnetic material because the magnetic layer does not contain a binder.

[0003] The basic structure of a vapor deposition tape currently sold or developed is polyethylene terephthalate (PE).
T), a magnetic layer formed by depositing a magnetic metal using a vacuum deposition method on a support such as polyethylene naphthalate (PEN) or polyimide. In addition, a top coat layer is formed to protect the magnetic layer and to act as a lubricant for smooth contact with the recording / reproducing head, and a support for improving the running property. The back coat layer is formed on the side opposite to the magnetic layer.

[0004] Conventionally, after a magnetic layer is vapor-deposited on a support in a vacuum, the support is taken out to the atmosphere, and then carbon black and carbon black are coated on the surface of the support opposite to the magnetic layer surface. Disperse ceramic powder (particle size: 10-100nm) etc. in a binder (using PVC, urethane, nitrified cotton etc. alone or as a mixture) and dry it by gravure method, reverse method or die coating method 0.4-1.0 μm thick
It is formed by applying such that However, when the back coat layer is formed by this method, the magnetic layer becomes dirty or dust adheres in the work process, and as a result, a drop-out test (a magnetic tape is put into a cassette deck for test). Play while recording a certain signal,
In a test for detecting a dropout where a reproduction signal is missing due to a scratch on the tape surface or the attachment of a foreign substance, there is a problem that the number of dropouts is increased. In addition, carbon black has good conductivity,
Since the binder is added, there is a problem that the conductivity is reduced and the antistatic effect is reduced.

[0005] Therefore, by forming the back coat layer conventionally formed by coating in the air by metal deposition in a vacuum using a metal material such as an aluminum-copper alloy, durability and running stability are improved. It has been proposed to obtain a magnetic recording medium having a high density.

[0006]

However, it is difficult to control the surface roughness of a metal thin film type back coat layer. In particular, the center line average roughness (Ra) and the ten point average roughness (Rz) are low. It is difficult to make it big. After forming the metal thin film type back coat layer, it is possible to control the surface roughness by etching or polishing, but a separate step is required, which is not desirable from the viewpoint of productivity.

Further, since the metal thin film type back coat layer is formed by depositing a metal, an oxidizing gas is introduced during or after the film formation to improve the durability of the thin film itself. Forming thin films containing substances (Japanese Unexamined Patent Publication No. 7-98
No. 853) or forming an oxide layer on a metal backcoat layer (JP-A-61-229230). However, even with these methods, it is difficult to achieve large Ra and Rz.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, when forming a metal thin film type back coat layer by a vacuum evaporation method, an inert gas is introduced. As a result, it has been found that a magnetic recording medium having a back coat layer having a small coefficient of friction by controlling Ra and Rz can be obtained, and the present invention has been completed.

That is, the present invention comprises a step of forming a back coat layer on the support by vapor-depositing a metal or metalloid on the support while introducing an inert gas in a vacuum atmosphere. An object of the present invention is to provide a method for manufacturing a magnetic recording medium.

[0010]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a support, a magnetic layer formed on the support, and a back coat formed on a surface of the support opposite to the surface on which the magnetic layer is formed. And a magnetic recording medium having a layer. In the present invention, the back coat layer is a metal thin film type, and is formed by depositing a metal or a metalloid on a support by a vacuum evaporation method. that time,
The present invention is characterized in that an inert gas is introduced into a metal vapor. Hereinafter, a method for forming a back coat layer according to the present invention will be described with reference to the drawings.

FIG. 1 is a schematic view of a vacuum deposition apparatus used for forming a back coat layer in the present invention. The vacuum vessel 1 is evacuated by vacuum means (not shown).
An unwind roll 2 and a take-up roll 3 are provided in the vacuum vessel 1, and the support 4 is placed under the can roll 5 while being unwound from the unwind roll 2 and wound up by the take-up roll 4. It runs around the side. The metal or metalloid may be deposited obliquely or by other methods. Here, a case will be described in which an apparatus for forming a back coat layer on a support by oblique deposition as shown in FIG. 1 is used. The method for oblique deposition is not particularly limited, and follows a conventionally known method. The degree of vacuum at the time of vapor deposition is 10 ^-4
~ 10 ^-7 Torr.

A crucible 6 made of MgO is placed below the can roll 5 and contains a metal or semi-metal serving as a back coat layer. Here, between the crucible 6 and the can roll 5, a deposition-preventing plate 7 for regulating the deposition range on the support 4 is provided. An electron beam is deflected from the electron gun 8 to irradiate the metal or metalloid in the crucible 6 with an electron beam, thereby heating the metal or metalloid to evaporate the metal or metalloid.

In the present invention, the metal or metalloid forming the back coat layer includes Al, Zn, Sn, Ni, Ag, V, C
metals such as r, Mo, Ti, and Cu; semimetals such as B, As, Te, and Si;
Further, these alloys may be mentioned. In particular, Al, Cu, and Al-Cu alloy are preferable for metal, and Si or its alloy is preferable for semimetal from the viewpoints of price, deposition rate, and the like.

In the present invention, the inert gas is introduced into the vapor of the metal or metalloid, but the inert gas may be introduced into any of the deposition regions. For example, as shown in FIG.
Although the introduction pipes 10a, 10b, and 10c can be provided at positions such as α, β, and γ, it is particularly desirable to introduce the introduction pipes near the upstream of the deposition region. Therefore, in the oblique vapor deposition apparatus as shown in FIG. 1, the introduction pipe 10 is provided at a position where the inert gas is introduced near the maximum incident angle of the vapor deposition region. Furthermore,
Β position opposite to the scattering direction of vapor deposition particles (introduction tube 10b)
It is preferable to introduce an inert gas from the above. By introducing the inert gas near the upstream of the deposition region, a moderately rough initial growth film is formed, and the surface of the subsequently grown growth film also becomes moderately rough.

In the present invention, a plurality of inert gases may be mixed and introduced from a single introduction pipe, or a single or a plurality of inert gases may be introduced from a plurality of introduction pipes. .

Examples of the inert gas to be introduced include argon gas, nitrogen gas, helium gas and the like. Inert gas refers to a gas that is chemically inert. The introduction amount of the inert gas can be adjusted by a flow control valve (not shown), and is usually introduced at a flow rate of 20 to 100 SCCM.

In the present invention, when forming the back coat layer, it is preferable to introduce an oxidizing gas into the deposition region. In particular, the oxidizing gas is desirably introduced near the downstream of the deposition region. Therefore, in FIG. 1, the oxidizing gas introduction pipe 9 is provided near the minimum incident angle of the deposition region. The introduction amount of the oxidizing gas can also be adjusted by a flow control valve (not shown), and is usually introduced at a flow rate of 20 to 100 SCCM. Examples of the oxidizing gas include oxygen, air, and ozone.

The thickness of the metal thin film type back coat layer formed by the present invention is not limited, but is preferably 0.01 to 0.5 μm.

According to the method of the present invention, the surface properties of the back coat layer are appropriately adjusted by changing the conditions (type, flow rate, introduction position, etc.) of the inert gas or the inert gas and the oxidizing gas. Can be. Generally, in a vapor deposition type magnetic recording medium such as the present invention, Ra to be targeted is 8 to 15 Ra.
nm and Rz are 30 to 60 nm, and the friction coefficient is desirably 0.15 to 0.30, but the method of the present invention can easily be controlled within these ranges.

The method of manufacturing a magnetic recording medium of the present invention includes the above-described steps of manufacturing a back coat layer, but includes other steps such as a step of forming a magnetic layer, a protective layer, a lubricant layer and the like, and a step of forming each layer. Various steps after the film formation conform to a known method.

The magnetic layer can be formed by depositing a magnetic metal on a support by a vacuum deposition apparatus as shown in FIG. Examples of the magnetic material forming the magnetic layer include ferromagnetic metal materials used in the manufacture of ordinary metal thin-film type magnetic recording media, for example, ferromagnetic metals such as Co, Ni, and Fe, and Fe-Co and Fe-Ni, Co-Ni, Fe-Co-Ni, Fe-Fh, Fe
-Cu, Co-Cu, Co-Au, Co-Y, Co-La, Co-Pr, Co-
Gd, Co-Sm, Co-Pt, Ni-Cu, Mn-Bi, Mn-Sb, Mn-A
l, Fe-Cr, Co-Cr, Ni-Cr, Fe-Co-Cr, Ni-Co-Cr
And other ferromagnetic alloys.

For high density recording, the magnetic layer of the magnetic recording medium is preferably formed on a substrate by oblique evaporation. The method for oblique deposition is not particularly limited, and follows a conventionally known method. The degree of vacuum at the time of vapor deposition is about 10 ^-4 to 10 ^-7 Torr. The magnetic layer formed by vapor deposition may have either a single layer structure or a multilayer structure. In particular, by introducing an oxidizing gas to form an oxide on the surface of the magnetic layer, the durability can be improved. In the present invention, the magnetic layer may be a single layer or a multilayer. The thickness of the magnetic layer is 120 to 19 for a single layer
The thickness of the lower magnetic layer is preferably from 70 to 120 nm, and the thickness of the upper magnetic layer is preferably from 60 to 100 nm. It is considered that two or three layers are appropriate as a practical range for the number of magnetic layers.

The vacuum deposition of the magnetic layer and the back coat layer may be performed continuously, or the steps may be performed separately, and one of the steps may be followed by winding on a roll and then unwinding from the roll to deposit the other. Good. Even if the magnetic recording medium is placed in the air in the middle of performing the separation separately, no problem such as adhesion of dust or the like occurs unless the magnetic recording medium is wound around a roll and unwound in the air.

In the present invention, it is preferable to form a protective film having a thickness of 1 to 50 nm on the magnetic layer. Examples of the material constituting the protective layer include oxides, nitrides, and carbides of metals such as Al, as well as SiC and compounds containing the same. In particular, a carbon film, especially diamond-like carbon, is preferable. The protective layer made of diamond-like carbon is formed by a physical vapor deposition (PVD) method or a chemical vapor deposition (CVD) method. In particular, it is formed by an ECR plasma CVD apparatus. That is, the ECR plasma CVD apparatus is operated on the magnetic layer on the support provided in the vacuum chamber, and plasma of the hydrocarbon gas is blown on the magnetic layer. Thereby, a protective layer (diamond-like carbon layer) is formed on the surface of the magnetic layer.

Further, in the present invention, it is preferable to form a lubricant layer made of a suitable lubricant on the magnetic layer or the protective layer. Particularly, a fluorine-based lubricant such as perfluoropolyether is preferable, and the thickness of the lubricant layer is about 0.5 to 10 nm. As the lubricant, for example,-[C (R) F-CF ₂ -O] _p- (where R is a group such as F, CF ₃ , CH ₃ ), particularly HOOC-CF ₂ (OC ₂ F ₄ )
_p (OCF ₂ ) _q -OCF ₂ COOH, carboxyl group-modified perfluoropolyether such as F- (CF ₂ CF ₂ CF ₂ O) _n -CF ₂ CF ₂ COOH, HOCH _2-
CF ₂ (OC ₂ F ₄ ) _p (OCF ₂ ) _q -OCF ₂ -CH ₂ OH, HO- (C ₂ H ₄ O) _m -CH _2- (OC
₂ F ₄ ) _p (OCF ₂ ) _q -OCH _2- (OCH ₂ CH ₂ ) _n -OH, F- (CF ₂ CF ₂ CF ₂ O) _n -C
Examples include alcohol-modified perfluoropolyethers such as F ₂ CF ₂ CH ₂ OH. The molecular weight is preferably from 500 to 50,000. Specifically, the product name “FOMBLIN” of Montecatini
Z DIAC "and" FOMBLIN Z DOL ", and Daikin Industries' brand name" Demnum SA ". Particularly in terms of durability, it is preferable to use a lubricant having both a fluorinated alkyl group and an alkyl group. It is also preferable to use a mixture of these lubricants.

As the support used in the method for producing a magnetic recording medium of the present invention, a normal non-magnetic support can be used, and polyethylene terephthalate (PET),
Polyesters such as polyethylene naphthalate (PEN); polyolefins such as polyethylene and polypropylene; cellulose derivatives such as cellulose triacetate and cellulose diacetate; polycarbonates; polyvinyl chloride; polyimides; The thickness of these supports is 3 to 50 μm
It is about.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

Examples 1 to 5 and Comparative Examples 1 to 4 Using the apparatus shown in FIG. 2, a back coat by vapor deposition was applied to the surface of the support having the magnetic layer and the protective layer formed on the magnetic layer opposite to the surface of the magnetic layer. A layer was formed.

First, using a vacuum deposition apparatus shown in FIG. 2, first, 180 nm of Co was deposited on a 6 μm-thick PET film by vacuum deposition, and a magnetic tape on which a magnetic layer was formed was wound around a roll. Was. At this time, 60
SCCM was introduced at the flow rate. Next, a protective layer of diamond-like carbon having a thickness of 10 nm was formed on the magnetic layer by ECR plasma CVD.

Next, the tape was set again in the apparatus shown in FIG. 2 and the Al-Cu
An alloy (80/20: weight ratio) was deposited to a thickness of 0.3 μm. At this time, the vapor deposition conditions were as follows: the output of the electron gun 8 was 13 kW, the film running speed was 2 m / min, the inert gas was introduced at the introduction position and flow rate shown in Table 1, and the oxygen gas was introduced at the introduction pipe 9 at the flow rate shown in Table 1. Introduced from.

The film obtained above on which the magnetic layer, the diamond-like carbon protective layer and the back coat layer are formed is cut into a width of 6.35 mm, loaded into a DVC (digital video cassette) case, and
I got the tape.

(2) Performance Evaluation The DVC tape obtained above was evaluated for the surface properties on the back coat layer side and the friction coefficient by the following methods. Table 1 shows the results. Surface properties Ra and Rz were measured with an optical surface roughness meter [model: Zygo Maxim D5700 (manufactured by Zygo)] under the measurement conditions of FilterOff and 40 times the objective lens Fizeau. Coefficient of friction DVC tape is wrapped around a 2mm diameter, 0.2S stainless steel roll at 90 °, 18.8 in an environment of 20 ° C and 50% RH.
100 passes were performed at 0.1 N in mm / s, and the maximum coefficient of friction in 100 passes was measured.

[0033]

[Table 1]

[0034]

According to the present invention, a magnetic recording medium having a metal thin film type back coat layer having a moderately rough surface and a good coefficient of friction can be obtained by a simple method.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a vacuum evaporation apparatus used in the present invention.

FIG. 2 is a schematic view showing another example of a vacuum deposition apparatus used in the present invention.

[Description of Signs] 1 vacuum vessel 2 unwinding roll 3 winding roll 4 support 5 can roll 6 crucible 7 shielding plate 8 electron beam gun 9 oxidizing gas introduction pipe 10 inert gas introduction pipe

Continued on the front page (72) Inventor Takeshi Miyamura 2606 Akabane, Kaigamachi, Haga-gun, Tochigi Pref.

Claims (5)

[Claims] 1. A magnetic recording medium comprising a step of depositing a metal or semimetal on a support while introducing an inert gas in a vacuum atmosphere to form a back coat layer on the support. Manufacturing method. 2. The method according to claim 1, wherein the inert gas is introduced near an upstream of a deposition region. 3. The method according to claim 1, further comprising introducing an oxidizing gas. 4. The method according to claim 3, wherein the inert gas is introduced near the upstream of the deposition region, and the oxidizing gas is introduced near the downstream of the deposition region. 5. The method according to claim 1, wherein the inert gas is an argon gas and / or an inert gas.
Or a nitrogen gas and / or a helium gas.
5. The production method according to any one of 4.