JPS61160830A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To increase the adhesive strength between a substrate and magnetic layer and to obtain a magnetic disk having excellent durability by forming the magnetic layer on the substrate which is subjected to a plasma treatment by using an inorg. gas contg. N, H and O and has a specific thermal deformation temp. or above. CONSTITUTION:The inside of a plasma treatment reaction vessel R is evacuated and thereafter an inorg. gas contg. O2 or an inorg. gas contg. N and H and an inorg. gas contg. N, H and O, for example, gaseous mixture selected from N2, H2, NH3, O2, NO, H2O, NOx, etc. are supplied from gas sources 1, 2 after the gases are mixed in a mixer 5 via mass flow controllers 3, 4. Electric power is supplied from a DC, AC and frequency variable type power source 6 to electrodes 7, 7' sandwiching a film for a magnetic tape while the film is fed repeatedly to a roll 9 or 10 in the reaction vessel. The plasma treated substrate of polyamide, polyimide, polyphenylene sulfide, all arom. polyester, etc. having >=150 deg.C thermal deformation temp. is obtd. at (10-200)kHz. A magnetic metal such as Co-Cr is deposited by evaporation on such substrate directly or via a substratum layer, by which the magnetic layer is provided. The magnetic recording medium having the excellent durability, etc. is thus obtd.

Description

BACKGROUND OF THE INVENTION TECHNICAL FIELD The present invention relates to magnetic recording media. For more details, please see
The present invention relates to a magnetic recording medium using a substrate that has been subjected to a predetermined plasma treatment to improve durability.

Prior art and its problems There is a magnetic recording medium in which a magnetic layer mainly composed of oxide-based magnetic powder such as γ-Fe2O3゜y-Fe304 or Co-impregnated 7-Fe2O3 and a binder is formed on a nonmagnetic support. It has been a long time since it appeared.

Recently, in order to further improve the recording density, F
e, Co, Ni, Fe-Co, C.

-Nl, Fe-Co-Ni, Fe-Co-B.

Fe-Co-Cr-B, Mn-Bi, Mn-
Magnetic recording media made of ferromagnetic powder such as Al or Fe-Go-V and a binder, as well as magnetic recording media having a magnetic layer made of a metal vapor-deposited film or a sputtered thin film, have been put into practical use and are attracting attention.

Among these magnetic recording media, especially for magnetic tape and magnetic disk applications, they must have a small coefficient of friction, exhibit smooth and stable running properties, have excellent wear resistance, and be able to run stably for long periods of time. There is a strong demand for such materials to be stable under different environmental conditions, capable of reliable regeneration at any time, and durable.

Conventionally, various pretreatments have been performed on various substrates for the purpose of improving durability.

In particular, plasma treatment has a great effect on improving durability and adhesive strength.

As a plasma treatment for the substrate, for example,
No. 7-42889 discloses a technique of processing using air, oxygen, nitrogen, hydrogen, helium, argon, or the like as a processing gas with plasma at radio wave or microwave frequencies.

In addition, according to Japanese Patent Application Laid-open No. 58-77030, oxygen, argon, helium, neon, or nitrogen is used as a processing gas.
A technique is disclosed in which plasma processing is performed using a predetermined applied current at a commercial frequency.

These plasma treatments improve adhesive strength with the magnetic layer and improve durability.

By the way, 1. For example, when a magnetic metal such as iron, cobalt, cobalt, chromium, etc. or an alloy thereof is deposited by vacuum evaporation, sputtering, etc. to form a magnetic layer thin film for perpendicular magnetic recording, It is necessary to raise the temperature.
However, a typical polyester resin substrate has a low heat resistance and undergoes thermal deformation during film formation, making it impossible to increase the substrate temperature.

Therefore, if a heat-resistant resin such as polyamide or polyimide is used as the substrate for the perpendicularly magnetized film, thermal deformation during film formation can be prevented.

However, various heat-resistant resins have a problem in that since water is contained in the resin, the water is released during film formation, the crystal structure of the magnetic layer is disturbed, and the perpendicular magnetization characteristics are deteriorated.

■ Purpose of the Invention The purpose of the present invention is to provide a magnetic recording medium using a plasma-treated substrate, which has a metal thin film magnetic layer with less disordered crystal structure, and has significantly improved durability. be.

■Disclosure of invention These objects are achieved by the invention described below.

That is, the present invention.

This magnetic recording medium is characterized in that a magnetic layer is formed directly or via an underlayer on a resin substrate having a thermal deformation temperature of 150° C. or higher and subjected to plasma treatment using an inorganic gas as a processing gas.

■Specific structure of the invention Hereinafter, a specific configuration of the present invention will be explained in detail.

The base material used in the magnetic recording medium of the present invention is a heat-resistant resin having a heat distortion temperature of 150° C. or higher.

In the present invention, when a heat-resistant resin having such a heat distortion temperature is used, it is possible to prevent crystal disorder during film formation.

Such heat-resistant resins include polyamides such as aromatic polyamides, polyimides such as aromatic polyimides, polyphenylene sulfide, polysal 7one, fully aromatic polyesters, polyether ether ketone (PEEK),
Examples include polyether sulfone and polyetherimide. Polyamide is a general term for polymers having an amide bond -CONH-, and is classified into natural polyamides and synthetic polyamides, and the former includes natural polypeptides. Synthetic polyamide is obtained by polycondensation of diamine and dicarboxylic acid (-CORCONHR')
It is broadly classified into RCONH+ type.

Aromatic polyamides are disclosed in Japanese Patent Publication Nos. 56-136828 and 59-45124. For example, polyimide is a general term for polymers that have imide bonds in their main chains. Basically, polyamic acid is made from dicarboxylic acid and diamine, and after molding, it is heated, dehydrated, and cyclized to form polyimide.

The general formula is It is indicated by. Here, R is a divalent group.

These polyamides and polyimides have extremely excellent heat resistance as a polymer property.

Polyphenylene sulfide is (It is a polymer with a -0-3+- structure.

Has excellent heat resistance.

Polysal7one has a sulfonyl bond in the main chain〇 Rizalfulfon has excellent heat resistance.

for example.

is an example.

A wholly aromatic polyester is a polyester having an aromatic skeleton, and examples thereof include a polymer having the structure of.

The structure of polyetheretherketone (PEEK) is as follows.

The structure of polyether sulfone is shown below, and that of polyetherimide is shown below.

There are no restrictions on the shape, dimensions, or thickness of the substrate made of such a material, and it may be in the shape of a film, disk, etc., depending on the intended use.

At least the magnetic layer forming surface of such a substrate is subjected to plasma treatment.

The plasma processing method uses an inorganic gas as a processing gas, and plasma-treats the surface of the substrate by bringing discharge plasma of this gas into contact with the substrate. vacuum evaporation method,
When depositing a perpendicular magnetization film using sputtering etc.
The crystals are arranged with uniform directionality. As a result, a magnetic recording medium can be obtained which has a perpendicularly magnetized film with high coercive force in the direction perpendicular to the film surface, in which disorder of the crystal structure can be prevented.

To outline the principle of plasma processing, when a gas is kept at a low pressure and an electric field is applied, the free electrons present in a small amount in the gas are accelerated by the electric field and move at a rate of 5 to 10 eV because their molecular distance is much larger than at normal pressure. Obtain energy (electron temperature).

When these accelerated electrons collide with atoms and molecules, they disrupt atomic and molecular orbits and dissociate them into chemical species that are unstable under normal conditions, such as electrons, ions, and neutral radicals.

The dissociated electrons are accelerated by the electric field again, causing them to dissociate from other atoms or molecules, and this chain reaction quickly turns the gas into a highly ionized state. And this is called plasma gas.

Gas molecules have fewer chances of collision with electrons, so they do not absorb much energy and are kept at a temperature close to room temperature.

A system in which the kinetic energy of electrons (electron temperature) and the thermal motion of molecules (gas temperature) are separated is called a low-temperature plasma, where chemical species undergo processes such as polymerization while remaining relatively intact. This creates a situation in which chemical reactions can proceed, and the present invention attempts to utilize this situation to plasma-treat a substrate.

In addition, as the resin material of the base, a resin with heat resistance is used.
Because it is used, it can also be heated during plasma treatment.

An example of an apparatus for treating the surface of a substrate with plasma is shown in FIG. FIG. 1 shows a plasma processing apparatus using a variable frequency power source.

In FIG. 1, one reaction vessel R is supplied with processing gas from a processing gas source 1 or 2 via mass flow controllers 3 and 4, respectively. When separate gases are supplied from the gas sources 1 or 2, they are mixed in the mixer 5 and then supplied.

Each of the process gases can have a flow rate range of 1 to 250 mJL/min.

A substrate support device to be processed is installed in the reaction vessel R, and here a feed roll 9 and a take-up roll 1O are shown for the purpose of processing a film for magnetic tape.

Various support devices can be used depending on the form of the substrate for the magnetic recording medium to be processed, and for example, a mounted rotary support device can be used.

Electrodes 7 and 7' are provided facing each other with the substrate to be processed in between, one electrode 7 being connected to a variable frequency power source 6, and the other electrode 7' being grounded at 8.

Furthermore, a vacuum system for evacuating the inside of the reaction vessel R is provided, and this is connected to the liquid nitrogen trap 11.
．． These vacuum systems, including an oil rotary pump 12 and a vacuum controller 13, operate within the reaction vessel at 0,01"l O
Maintain the vacuum within the range of Tarr.

In the operation, the inside of the reaction vessel R is first set at 10-3 Torr.
The inside of the container is evacuated by an oil rotary pump until the amount reaches below 100 ml, and then the processing gas is supplied in a mixed state into the container at a predetermined flow rate.

At this time, the vacuum inside the reaction vessel is 0.01 to 10-1 cm
It is managed within the range of rr.

Once the transfer rate of the substrate to be processed and the flow rate of the processing gas are stabilized, the variable frequency power supply is turned on. thus,
The transitioning substrate is plasma treated.

In such plasma processing, the present invention uses an inorganic gas containing oxygen 02, an inorganic gas containing N and H, or an inorganic gas containing N, H, and 0 as the processing gas.

These inorganic gases are N2, N2, and NH3.

02, No, N20. N20. A mixture thereof may be used, appropriately selected from among such as Not, etc.

And if it contains oxygen, the content of oxygen in the inorganic gas is 5
% or more, or if it contains N, H, O, etc., N in the inorganic gas
The content of is 5 to 80 at, and the content of H is 5 to 80 at.
%, the content of O is 0 to 50 at%. If the content range of the substances contained in the above-mentioned inorganic gas deviates from the above-mentioned range,
The present invention will no longer be effective.

Note that when the above-mentioned inorganic gas contains a gas other than N, H, and O, it may be one or more of Ar, Ne, He, and the like.

Furthermore, the frequency of the power supply is between 10KHz and 200KHz.
It is said that

If the frequency is lower than 10 KHz or higher than 200 KHz, the durability will decrease rapidly and the adhesive strength will decrease rapidly.

Note that the applied current, processing time, etc. may be set to normal conditions.

The contact angle of the substrate subjected to such plasma treatment was reduced, and FTIR (Fourier transform infrared absorption spectrum) confirmed that the surface was modified and C0OH bonds and N-H bonds were formed. It is possible.

The magnetic layer formed on the surface of the plasma-treated substrate in this way is of a metal thin film type, and various types are possible.

A perpendicularly magnetized film is particularly preferable as the metal thin film, because according to the present invention, it is highly effective in preventing disturbances in the crystal structure during the formation of the perpendicularly magnetized film.

Various types of perpendicular magnetization films are used.

CoCr, CoV, CoN1P, CoP.

MnB1. MnAjLGe, NdFe, NdCo, C
oO, MnSb, MnCuBu, GdFe, GdC
o, PtCo, TbCo.

TbFeCo, GdFeCo, TbFeO3.

GdIG, GdTbFe, GdTb
Any of FeCoBi, CoFe204, etc. may be used.

These magnetic layers may be formed directly on the plasma-treated surface of the substrate by a method such as a vacuum evaporation method or a sputtering method, or may be formed with an underlying layer interposed therebetween.

The base layer may be formed from an alloy of aluminum, copper, titanium, chromium, etc. by ion blasting, vacuum evaporation, sparring, or the like.

■Specific Effects of the Invention According to the present invention, since a resin with excellent heat resistance and a heat distortion temperature of 150°C or higher is used as the material of the substrate to be plasma treated, no moisture is released from the surface of the substrate during film formation and crystallization occurs. The magnetic layer can be changed with less structural disturbance.

Therefore, when a perpendicularly magnetized film is formed, the magnetizing force in the direction perpendicular to the film surface becomes high, and the durability characteristics are also significantly improved.

(2) Specific Examples of the Invention Hereinafter, specific examples of the present invention will be shown and the present invention will be explained in more detail.

Example 1 A substrate made of the materials shown below (substrate materials 1 to 3) was subjected to plasma treatment (processing conditions 1 to 7 degrees, comparative processing conditions 1 to 4) using a mixed gas as shown below as a processing gas.

L Lord 1I” aromatic polyamide (Product name = Aramid film, manufactured by Toshi) aromatic polyimide (Product name Ni Kapton, manufactured by du Pant) L raw beans Polyphenylene sulfide (Product name: Ryton, manufactured by Philips) 11 Ai 1” Processing gas: A mixed gas of 02:Ar=l:1.

Gas flow rate: 50 mm/min Vacuum level: 0.1 Torr Power source: 100 KHz Processing gas: NH3 Gas flow rate = 100 mm/min Vacuum level: 0.1 Torr Power source: 100 KHz 1 mm Processing gas: A mixed gas of NO2:H2=3:l.

Gas flow rate: 100 g + 4/min Vacuum degree: 0.1 Torr Power source: 150 KHz 110'' In processing condition 1, the power source was AC, and other conditions were the same as in processing condition 1.

In processing condition 1, the power supply was set to 500 KHz, and the other conditions were the same as in processing condition 1.

凰1''LlJ In processing condition 2, the power source was DC, and other conditions were the same as in processing condition 1.

11 Kei 11 In processing condition 2, the power source was set to 13.56 MHz, and other conditions were the same as in processing condition 1.

Salt JLJL! L-Yu corona discharge treatment was carried out. The corona discharge treatment was carried out at a voltage of 20 using Coas treatment @P-500VA manufactured by Pillar.
It was carried out at 0v.

Arashi Toko I” Under processing conditions 1, the processing gas was Ar.

ratio”E 瀝JJ In processing condition 4, the processing gas was Ar.

Hi”L JL4 In processing condition 5, the processing gas was Ar.

Furthermore, a magnetic layer was provided on each of the substrates treated in this manner by the method shown below, and various 5'' magnetic disks shown in Table 1 below were manufactured.

A magnetic layer of 0 and I ILm was formed from an ingot of Go and Cr using a vertically incident component of the highest vapor content of evaporated atoms.

The composition of the film was controlled to be 80 wt% Co and 20 wt% Cr.

Co-Cr (composition Co80wt%-Cr20wt%)
was sputtered to a thickness of 0.1 pm using as a raw material.

The following tests were conducted on the samples.

(a) Endurance time Record on a 5" magnetic disk with a vertical head.

The contact angle was measured by the water droplet projection method using a contact angle meter CA-P type (manufactured by Kyowa Chemical), which measured the time until the reproduction output decreased to 95%.

('') Δθ5° The half width Δ'5G of the rocking curve for the (002) plane was measured for the purpose of investigating the dispersion of the C axis of Co analyzed by an X-ray crystal structure analyzer.

The results are shown in Table 1.

From the results in Table 1, the effects of the present invention are clear.

[Brief explanation of drawings]

FIG. 1 shows a schematic diagram of a plasma processing apparatus using direct current, alternating current, and variable frequency power supplies. 1.2: Process gas source 3.4: Mass flow controller 5: Mixer 6: DC, AC and variable frequency power supply 7.7': Electrode 9.10: Payout and take-up roll 11: Liquid nitrogen trap 12: Oil Rotary pump applicant TDC Co., Ltd. agent
Person Patent attorney Yo Ishii -FIG, 1 Procedural amendment (voluntary) 6 February 7, 1985 Manabu Shiga, Commissioner of the Patent Office 2 Name of invention Magnetic recording medium 3 Relationship with the case of the person making the amendment Patent Applicant location
Nihonbashi-chome 13-1, Chuo-ku, Tokyo Name
(306) Representative of TDC Co., Ltd.
Hiroshi Otoshi 4, Agent 101 Address 4th floor, Chiyoda Iwamoto Building, 3-2-2 Iwamoto-cho, Chiyoda-ku, Tokyo Contents of amendment (1) Line 10, page 3 of the specification (1) ry-Fe30
4. Correct "Co impregnated" to "rCo-containing".

Claims (7)

[Claims] (1) A magnetic recording medium characterized in that a magnetic layer is formed directly or via an underlayer on a resin substrate having a thermal deformation temperature of 150° C. or higher and subjected to plasma treatment using an inorganic gas as a processing gas. (2) A patent in which the resin base is formed from one or more selected from polyamide, polyimide, polyphenylene sulfide, polysulfone, wholly aromatic polyester, polyetheretherketone, polyethersulfone, and polyetherimide. A magnetic recording medium according to claim 1. (3) The magnetic recording medium according to claim 1 or 2, wherein the magnetic layer is a metal thin film. (4) The magnetic recording medium according to any one of claims 1 to 3, wherein the plasma treatment is performed at a frequency of 10 KHz to 200 KHz. (5) The magnetic recording medium according to any one of claims 1 to 4, wherein the inorganic gas contains oxygen. (6) The magnetic recording medium according to any one of claims 1 to 4, wherein the inorganic gas contains N and H. (7) The magnetic recording medium according to any one of claims 1 to 4, wherein the inorganic gas contains N, H, and O.