JPS615435A - Manufacture of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the titled magnetic recording medium without any curls and whose electromagnetic characteristic is not deteriorated by specifying the flow rate of a gaseous monomer to be introduced, the voltage to be impressed, and the area of an electrode, and plasma-polymerizing the monomer to form a protective layer on the ferromagnetic metallic thin film formed on a nonmagnetic supporting body. CONSTITUTION:While a nonmagnetic supporting body 7, on which a ferromagnetic metallic thin film is formed, is moved from a supply roll 8 to a winding roll 9, a gaseous monomer is plasma-polymerized by regulating the flow rate of the gaseous monomer to F(cc/sec), the power to be impressed to W (watt), and the respective areas of electrodes 3 and 4 to Scm<2>, where W/(FXS) is regulated to 5-10W/(cc.sec.cm<2>). A protective layer 9 is formed on a magnetic film 8 in this way. Simultaneously with the formation of the protective film 9, the film 8 is placed at the inside to eliminate the generation of curls by the internal stress due to the contraction generated when the magnetic film 9 is formed. Consequently, the magnetic recording medium having excellent flatness, traveling property, and durability is manufactured with good productivity.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for manufacturing a ferromagnetic metal thin film type magnetic recording medium such as a so-called vapor-deposited tape, and more specifically to a method for eliminating curl. be.

[Background technology and its problems]

In the field of magnetic recording, higher recording density and shorter wavelength recording signals are being recorded, and in response to this, the coercive force H
There is a demand for magnetic recording media with large c and residual magnetic flux density Br.

Conventionally, a ferromagnetic metal thin film made of a ferromagnetic metal material such as a Co-Ni alloy is deposited directly on a non-magnetic support such as a polyester film using a vacuum evaporation method or a spacing method. A magnetic recording medium of a ferromagnetic metal thin film type magnetic layer has been proposed and is attracting attention. This ferromagnetic metal thin film type magnetic recording medium not only has high coercive force Hc and residual magnetic flux density Br, but also has extremely low thickness loss during recording demagnetization and reproduction because the thickness of the magnetic layer can be made extremely thin. It has many advantages in terms of magnetic properties, such as the ability to increase the packing density of ferromagnetic metal materials because there is no need to mix resin binders such as vinyl chloride-vinyl acetate copolymer or polyurethane resin into the layer. ing.

However, in this type of magnetic recording medium, since a vacuum evaporation method or the like is used as a means of forming the ferromagnetic metal thin film, the base film, which is a non-magnetic support, is susceptible to thermal damage. In addition, when the evaporated metal atoms recrystallize and form a thin film on this base film, they shrink and generate internal stress, resulting in a concave bend called a curl, with the ferromagnetic metal thin film on the inside. It has some drawbacks.

Therefore, various methods have been tried in the past in order to eliminate the above-mentioned curls.

For example, after depositing a ferromagnetic metal thin film, a type of crack called a crack is created in the metal thin film to relieve strain stress, or after a ferromagnetic metal thin film is deposited, heat treatment is applied to the non-magnetic support side. A method of relieving stress by shrinking the magnetic layer, a method of relieving stress by providing a back coat layer on the side opposite to the magnetic layer (ferromagnetic metal thin film), etc. are known.

However, all of these methods require a special process for eliminating curls, and have many drawbacks in terms of productivity and the like.

On the other hand, the above-mentioned ferromagnetic metal thin film type magnetic recording medium has many drawbacks in terms of durability, runnability, etc., and improvement thereof has become a major issue.

[Purpose of the invention]

Therefore, the present invention was proposed in view of the above-mentioned conventional situation, and is a ferromagnetic metal thin film magnetic film having excellent flatness, durability, runnability, etc. by forming a protective film and at the same time eliminating curls. It is an object of the present invention to provide a method for manufacturing a magnetic recording medium that can manufacture the recording medium with high productivity.

[Means for solving problems]

As a result of intensive studies to achieve the above objectives, the inventors of the present invention discovered that the stress that causes curling can be canceled by controlling the applied voltage when forming a protective film by plasma polymerization. Heading The present invention has been completed, and the present invention has been introduced in forming a protective film by plasma polymerization on the surface of a ferromagnetic metal thin film of a magnetic recording medium in which a ferromagnetic metal thin film is provided on a non-magnetic support. The monomer gas flow rate is F (CC/(8)), and the applied power is W (
w), which is characterized by carrying out polymerization.

The magnetic recording medium to which the present invention is applied is a so-called ferromagnetic metal thin film type magnetic recording medium in which a ferromagnetic metal material is directly deposited on a nonmagnetic support and a ferromagnetic metal thin film is formed as a magnetic layer. .

Materials for the non-magnetic support include polyesters such as polyethylene terephthalate, polyolefins such as polyethylene and polypropylene, cellulone derivatives such as cellulose triacetate, cellulose diacetate, and cellulose acetate butyrate, polyvinyl chloride, polyvinylidene chloride, etc. Examples include plastics such as vinyl resin, polycarbonate, polyimide, and polyamideimide. Furthermore, the form of the non-magnetic support is as follows:
Any of film, tape, sheet, disk, card, drum, etc. may be used.

The above-mentioned ferromagnetic metal material may be any material that is normally used in this type of magnetic recording medium, such as iron (Fe), cobalt (Co), nickel (Ni), etc.
metals such as Co-Ni alloy, Fe-Co alloy, F
Examples include alloys such as e-Ni alloy and Co-Ni-Fe-B alloy, and those containing metals such as Cr and Al1.

The means for depositing the ferromagnetic metal material include vacuum evaporation,
Examples include the ion plate ink method and the sputtering method.

In the vacuum evaporation method, the ferromagnetic metal material is evaporated on the non-magnetic support by resistance heating, high frequency heating, electron beam heating, etc. under a vacuum of 10-4 to 10-5 Torr. This method is divided into two methods: oblique deposition method and vertical deposition method. In the above-mentioned oblique deposition method, the ferromagnetic metal material is obliquely deposited on a non-magnetic support in order to obtain a high coercive force. It also includes things that are done. In the vertical deposition method, Bit'rV and Sb are preliminarily deposited on a non-magnetic support in order to improve deposition efficiency and productivity and to obtain high coercive force.

A base metal layer of Ga, Ge, etc. is formed in advance, and the ferromagnetic metal material is vertically deposited on the base metal layer. The above-mentioned ion plate ink method is also a type of vacuum evaporation method, in which DC glow discharge and RF glow discharge are generated in an inert gas atmosphere of 10-4 to 10" Torr, and the above-mentioned ferromagnetic metal is evaporated during the discharge. The spackle method described above is a method in which glow discharge is caused in an atmosphere containing argon gas as the main component at 10 to 10 Torr, and the generated argon ions knock out atoms on the target surface. DC 2
Examples include pole and three-pole sputtering methods, high-frequency sputtering methods, and magnetron sputtering methods that utilize magnetron discharge.

In the present invention, a protective film is formed on the surface of the ferromagnetic metal thin film of the above-mentioned magnetic recording medium by plasma polymerization with a predetermined applied power.

The plasma polymerization described above involves performing glow discharge in an organic monomer gas alone or in a mixture of the monomer gas and another gas (carrier gas), and depositing a polymer film derived from the excited monomer on a substrate in contact with the discharge region. This allows for, for example, 1) high adhesion to the ferromagnetic metal thin film that is the substrate, 2) high density, 3) heat resistance, and 4) uniform film formation. An extremely thin polymeric film with properties such as formation is formed as a protective film.

The monomer gas used in the above plasma polymerization may be any commonly used monomer gas, such as CF4, C2F! .

CF8 C2H8F, CzH2F'z, CzFo, CFaN
O, 3-fluorine-containing compounds such as CFg-C-0, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, n-propylamine, di-n-propylamine, tri-n-propylamine, n- Butylamine, rhoamylamine, n-hexylamine, laurylamine, ethylenedi787.
1 ノ )-y-v ′-)y ゝ ′・ ′
′-flfLy”/
, t-diamine, ethanolamine, jetanolamine, allylamine, aniline, alanine, N-methylaniline, allyldimethylamine, 2
-aminoethyl ether, 1-dimethylamino-2-chloroethane, cyclopropylamine, cyclohexylamine, ethyleneimine, 1-methylethyleneimine, N
, N-dimethylformamide, formamide, capronamide, aminoacetal.

Organic amine compounds such as benzylamine, piperidine, pyrrolidine, morpholine, trimethylchlorosilane, trimethylmethoxysilane, vinyldimethylchlorosilane,
Organic materials such as tetramethoxysilane, tetraethoxysilane, trimethoxysilane, alicite-1-ethoxysilane, phenyltrimethoxysilane, tetraallyloxysilane, methyldichlorosilane, vinylmethyldichlorosilane, and organosiloxanes as hydrolyzed condensates thereof Silicon compounds, ethylene, propylene, acetylene, vinyl chloride, vinylidene chloride, acrolein, allyl alcohol, maleic acid, acrylic acid, methyl methacrylate, cyclopentene, cyclohexene, cyclohexe/-/L/, 2, s-dihydrofuran, phlopadiene, 1.2--j tadiene,
1.3-bucudiene, 1,7-octadiene, ■.

Examples include organic unsaturated compounds such as 3.5-hexatriene, benzene, styrene, phthalic acid, phenol, aniline, dichlorobenzene, naphthalene, and cyclohexadiene.

In particular, in order to form a highly durable protective film, (1)
Method of using silazane monomer gas as monomer gas (2) Using silazane-based monomer gas as monomer gas
The plasma polymerization reaction may be carried out by a method using fluorocarbon and oxygen, hydrogen, or nitrogen as a carrier gas.

The method (1) above involves performing a plasma polymerization reaction using a silazane compound, which is an organosilicon compound having a Si--N bond, as a monomer gas,
In this way, a highly durable polymer film can be obtained, but in particular, by mixing 20 to 40 volumes of an inert gas such as argon gas or oxygen to these silazane monomer gases, the degree of crosslinking is high and the ferromagnetic metal thin film is bonded to the silazane monomer gas. A polymer film with excellent adhesion is formed as a protective film. Here, the silazane compounds used are: (1) Tetramethylcyclodisilazane (2) ], 1,3,3-tetramethyldisilazane H + H+ (CHa)2-8i-tN-8i-(CH8)2 ■
Hexamethylcyclotrisilazane■ Hexaphenylcyclotrisilazane■ Octamethylcyclotetrasilazane! 1 ■ 1,3-bis(chloromethyl)tetramethyldisilazane■ Hexamethoxydisilazane (CH20-N-8i-(OCHz)s■ Hexamethyldisilazane (CHa) asiNH8i (CHa)a, etc. be done.

On the other hand, the method (2) above uses, as a monomer gas, a fluorocarbon (having 2 to 4 carbon atoms) having an unsaturated bond, particularly preferably tetrafluoroethylene (C2F4) or hexafluoropropylene (CaFa), and One of oxygen, hydrogen, and nitrogen is used as a carrier gas, and a plasma polymerization reaction is carried out by performing glow discharge in a mixed gas of these monomer gases and carrier gas.

Here, the ratio of the monomer gas to the carrier gas is important, and when oxygen is used as the carrier gas, the volume ratio of monomer gas to carrier gas is 75:25.
~85:15, when hydrogen is used as the carrier gas, the monomer gas:carrier gas volume ratio is 5=
If nitrogen is used as the carrier gas, the monomer gas:carrier gas volume ratio must be set at 95:50:60:50:50:50:20. Thus, by setting the ratio of the monomer gas to the carrier gas within a predetermined range, a polymeric film that is highly crosslinked and exhibits excellent durability is formed.

The reaction apparatus used to carry out the plasma polymerization reaction in the present invention may be of any commonly used type, but for example, two electrodes are disposed facing each other in a bell jar, and these electrodes are placed in a bell jar. An example is an internal electrode type reaction device in which high-frequency power is applied between the two.

FIG. 1 schematically shows an example of a plasma reactor used in the present invention.

This reaction apparatus has a pair of electrodes 3 and 4 arranged facing each other, an electrode 3 connected to a high frequency power source 2 and an electrode 4 connected to a grounded electrode, in a reaction chamber 1 in which a five-plasma polymerization reaction is carried out. The pressure inside the reaction chamber 1 is reduced through an exhaust pipe 5, and monomer gas or a mixed gas of monomer gas and carrier gas is introduced into the reaction chamber 1 through a gas introduction pipe 6.

Further, between the electrodes 3 and 4, a non-magnetic support T having a ferromagnetic metal thin film deposited on its surface is disposed, and even if it is a long support by a supply roll 8 and a winding roll 9, It can be processed continuously.

Using the reaction apparatus configured as described above, first, the residual air in the reaction chamber 1 is sufficiently removed to reduce the pressure to about I Activating the high frequency power source 2 while introducing it into the reaction chamber 1 at a flow rate of
High-frequency power of a predetermined frequency (usually 13, 56 MHz) is applied between the electrodes 3 and 4 to cause a discharge, and as shown in FIG. 2, the ferromagnetic At this time, the power applied to the electrodes 3 and 4 is important.
When forming the above-mentioned protective film 9 by plasma polymerization, if the applied power is increased, the positive curl (curl such that the ferromagnetic metal thin film 8 is on the inside) gradually disappears and becomes even more curly. Then, negative curl (support T
It turns out that the curls are curled so that the inside of the curl is on the inside. According to the inventor's experiments, the degree of curl of the obtained magnetic recording medium (the third degree in a magnetic recording medium with a width of 3A inch)
In order to keep the amount (rDHI) indicated by Regardless of the thickness of the polymer film formed,
It was found that the monomer gas flow rate was F (cC/see), the power applied by the high frequency power source 2 was W (,w), and the electrode 3 was applied. That is, for example, monomer gas
C0mt+□, 7-1t force 3°-4□. . . ,Yo,
In some cases, the power applied by the high frequency power source 2 is increased to 500
It is sufficient to set it to ~1000W.

As mentioned above, by performing the plasma polymerization reaction while setting the value of . The durability and runnability of the magnetic recording medium are improved, and at the same time, curling can be eliminated.

Note that after forming the protective film 9, the protective film 9 may be subjected to oxygen plasma treatment to modify its surface, thereby further improving the runnability of the resulting magnetic recording medium. . The oxygen plasma treatment is performed by performing glow discharge in an oxygen atmosphere and applying a physicochemical surface treatment to the surface of the protective film 9 using the generated oxygen plasma, using the same reaction apparatus as the plasma polymerization reaction described above. is available.

Next, specific examples of the present invention will be described, but it goes without saying that the present invention is not limited to these examples.

〔Example〕

Example 1 A back coat layer with a thickness of 0.4μ was provided on a polyethylene terephthalate film with a thickness of 9μ, and a Co-N layer with a thickness of 1000A was formed on the opposite side of the film by oblique vapor deposition.
An i-alloy film (Co content: 80% by weight, Ni content: 20% by weight) was formed by vapor deposition.

Then, hexamethyldisilazane [
(CHs)ssiNH8i(CHs)+) was used, argon (Ar) was used as the carrier gas, monomer gas flow rate was 8 cC/IRm, carrier gas flow rate was 3 CC/mm, and pressure was 2.5 X I Q-"Tor.
r, and set the applied power (frequency 13.56 h) to the first
A plasma polymerization reaction was carried out for 20 seconds with changes as shown in the table to form a plasma polymerized film on the surface of the Co--Ni alloy film. Note that the electrode in the reaction apparatus used here was circular, and its diameter was 32 cm (area approximately 804 cm).

Next, pressure 5. Oxygen plasma treatment was performed for 10 seconds under the conditions of OX 10 Torr and high frequency power (frequency 13.56 MHz) 400 W to produce Samples 1 to 5.

Each of the obtained samples was cut into inch width pieces, and the degree of curl was measured. The results are shown in Table 1.

Note that in Table 1, the comparative samples are those without a plasma polymerized film.

Table 1 From Table 1, it can be seen that according to the manufacturing method according to the present invention (Samples 3 to 5), magnetic recording media with extremely little curl can be manufactured.

Example 2 In Example 1 above, the applied power was set to 700 W and the plasma polymerization reaction was carried out for 710 seconds, but the process was repeated in the same manner as in Example 1. Sample 6 was produced. In addition, the film thickness of the plasma polymerized film in this sample 6 was 80 mm.

When the degree of curl of the obtained sample 6 was measured, it was found to be ±O
mm, and had extremely excellent flatness.

〔Effect of the invention〕

As is clear from the description of the above embodiments, according to the present invention, plasma polymerization is performed by setting the monomer gas flow rate and the applied power within a predetermined range, so that the plasma polymerization film can be prepared at the same time. It becomes possible to eliminate curling, and it is possible to manufacture a magnetic recording medium with excellent flatness, durability, and running performance.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram schematically showing an example of a plasma polymerization reaction apparatus used in the present invention, FIG. 2 is an enlarged sectional view of main parts showing the structure of a magnetic recording medium obtained by the present invention, and FIG. It is a schematic diagram explaining curl degree. 7...Nonmagnetic support, 8...Ferromagnetic metal thin film 9...
·Protective film

Claims (1)

[Claims] When forming a protective film by plasma polymerization on the surface of a ferromagnetic metal thin film of a magnetic recording medium in which a ferromagnetic metal thin film is provided on a nonmagnetic support, the introduced monomer gas flow rate is set to F(
C. C. /sec), the applied power is W (w), the electrode area is S
(cm^2), the value of W/(F・S) is 5~
10 [W/(C.C./sec·cm^2)] A method for manufacturing a magnetic recording medium, characterized by performing plasma polymerization under conditions such that the polymerization ratio becomes 10 [W/(C.C./sec.cm^2)].