JPS61115232A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium causing hardly traveling friction, having high corrosion resistance, and maintaining the reproduction output by forming a plasma-polymerized film having a specified atomic ratio of F/C as a top coat film and by specifying the thickness of the film and the angle of contact with water. CONSTITUTION:A top coat film having 0.3-2, preferably 0.5-1.5 atomic ratio of F/C is formed. In case of <0.3 atomic ratio, traveling friction is not well reduced, and in case of >2 atomic ratio, the film is not fit for practical use because the output is reduced as traveling is repeated. The top coat film is a plasma-polymerized film of 10-40Angstrom , preferably 15-30Angstrom thickness. In case of >40Angstrom thickness, spacing loss is excessively increased to reduce magnetic flux density, and in case of <10Angstrom thickness, corrosion resistance and durability are not provided. The angle of contact of the top coat film with water is 100-130 deg., preferably 110-120 deg.. In case of <100 deg. angle, initial friction is increased, and in case of >130 deg., it is difficult to form the plasma-polymerized film.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. Background of the Invention Technical Field The present invention relates to an improvement in the top coat film of a magnetic recording medium, particularly a magnetic recording medium having a continuous 11Illi type magnetic layer.

Prior art and its problems As magnetic recording media for video, audio, etc., media having a continuous thin film type magnetic layer are being actively developed because of their compactness when wound into tapes.

Due to its characteristics, the magnetic layer of such a continuous thin film type medium is made of Co, Go-Ni, which is formed by the so-called oblique evaporation method, which is deposited at a predetermined tilt angle with respect to the X&X oil body.
, Co-0, Co-Ni-0 and the like are most suitable.

However, such a magnetic layer has high running friction, low film strength, poor head touch, and particularly low running durability, resulting in a decrease in output due to repeated running.

In addition, video media have a short durability in a still image mode called still.

Furthermore, there are many so-called dropouts.

Under these circumstances, various top coat films of diagonally deposited magnetic layers have been proposed.

As an example of a top coat film, a fluorocarbon-based plasma polymerized film is known (Japanese Patent Laid-Open No. 59-7265
No. 3, No. 5B-194131, No. 57-135442
No. 57-135443, No. 57-198542, No. 58-102330, No. 58-88829, No. 58-88828, etc.).

However, the fluorocarbon-based plasma polymerized film top foot obtained by the conventional method has disadvantages such as high running friction, insufficient corrosion resistance, and reduced regeneration output.

(2) Purpose of the Invention An object of the present invention is to provide a magnetic recording medium that has low running friction, good corrosion resistance, and does not cause a decrease in reproduction output.

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

That is, the present invention has a ferromagnetic metal thin film on a support,
In a magnetic recording medium having a top coat film on this ferromagnetic metal thin film.

The top coat film is a gold film containing plasma containing carbon and fluorine and having a fluorine/carbon atomic ratio of 0.3 to 2, an N51 thickness of 10 to 40 mm, and a contact angle with water of 0.3 to 2. is 100 to 13o#.

■Specific structure of the invention A specific configuration of the present invention will be explained in detail below.

The top coat film of the magnetic recording medium of the present invention is a plasma polymerized film.

This film is a thin film containing carbon and fluorine.

Thin films containing these elements are usually made using fluorocarbon raw material gases such as tetrafluoromethane, octafluoropropane, octafluorocyclobutane, tetrafluoroethylene, and hexafluoropropylene, which are gases at room temperature, either singly or in combination, due to their ease of operation. or boron fluoride.

It is formed by plasma polymerization using IWi or higher nitrogen fluoride, silicon fluoride, etc. mixed with one or more of the above-mentioned fluorocarbons.

In this case, if necessary, Freon 12 or Freon 13B, which is liquid or solid at room temperature, 1. Freon 22 or the like may be used as a raw material.

Further, if necessary, trace components such as nitrogen, boromine, boron, and phosphorus may be added to the raw material.

Further, the atomic ratio of two/element/carbon contained in the top coat film is 0.3 to 2, more preferably 0.5 to 1.
It is 5. If this atomic ratio is less than 0.3, the running friction will not be sufficiently reduced and it will not be practical.

Moreover, if this atomic ratio exceeds 2, the output will decrease as the number of runs increases, making it unsuitable for practical use.

In addition, the elemental analysis of F/C of the top coat film was performed using SIMS.
, an analysis method such as ESCA Auger may be used.
When using SIMS.

) -/ It may be calculated by counting F and C on the surface of the fucoate film, or it may be calculated by measuring the profile of F and C while performing ion etching with Ar or the like.

! Regarding the measurement of MMS, please refer to Volume 3 of 1 Surface Science Basic Course (
1984) Fundamentals and Applications of Surface Analysis P70 "SIMS and I, AMMA" can be praised for its description.

The thickness of the plasma polymerized film is lO~4°λ,
More preferably, it is 15 to 30λ.

In the M series i4s type magnetic recording medium, the plasma polymerized film is
If the number exceeds 0, the spacing loss (magnetic loss due to yI difference) becomes too large and the magnetic flux density decreases. And clogging increases.

Problems such as a large decrease in output after endurance running occur frequently.

In addition, if it is thinner than 10, the corrosion resistance and durability of the present invention cannot be obtained. In the case of forming a plasma polymerized film, such control of film thickness depends on the reaction time, medium transfer rate, and raw material gas as described below. This is done by controlling the flow rate, and has low spacing loss, good corrosion resistance, and durability.
The body is realized.

The contact angle between this top coat film and water is 100~
130@, more preferably 110 to 120@. If this contact angle is less than 1001, the initial value is +1! It has a lot of friction and is not suitable for practical use.

Further, it is difficult to produce a plasma polymerized film having a contact angle of more than 130'', and there is no practical need for it.

Formation of the plasma polymerized film of the present invention is performed using W/FM (herein,
W is the plasma input power (Joule/5ec), F is the raw material gas flow rate (Kg/5ec), and M is the raw material gas molecular weight). More preferably W/FM value is 108~
l O11 Joule/kg. W/FM value is 1
If it is less than 07, a plasma-polymerized film with a dense surface cannot be formed, resulting in poor corrosion resistance and cannot be put to practical use.If it exceeds 1012, the damage to the base will be large and it cannot be put to practical use.

In addition, when using two or more kinds of raw material gases, F and M are
The total amount will be counted.

The plasma polymerized film uses the above-mentioned carbon dioxide as a raw material gas, and forms a polymerized film by bringing discharge plasma of this gas into contact with a magnetic layer.

To give an overview of the principle of plasma polymerization, when the substrate is kept at low pressure and an electric field is applied, the free electrons present in a small amount in the substrate undergo electrolytic acceleration due to their molecular distance being very large compared to normal pressure. Obtain kinetic energy (TL child bath 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 electrolytically accelerated again and dissociate other atoms and 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.

In this way, the kinetic energy of the electron (′: 4.child temperature)
A system in which the gas and one molecule's thermal interlock (gas temperature) are separated is called a low-temperature plasma, and this creates a situation in which chemical species can proceed with acidic chemical reactions such as polymerization while remaining relatively intact. 5 The present invention attempts to utilize this situation to form a plasma polymerized film on a base film. Note that since low-temperature plasma is used, there is no thermal effect on the base film or magnetic layer.

An example of an apparatus for forming a plasma polymerized film on the surface of a base film using plasma is shown in FIG. ! Figure 1 shows a plasma polymerization apparatus using a single frequency variable power source.

In the first frA, one reaction vessel R includes an IiK material gas source 5
Raw material gas is supplied from 11 or 512 via mass flow controllers 521 and 522, respectively. When separate gases are supplied to the gas source 511 or 512, they are mixed in a mixer 53 and then supplied.

Each source gas can have a flow rate range of 1 to 250 mA/min.

Inside the reaction vessel R, a base film support 91 to be processed is installed, and a feed roll 561 and a take-up roll 562 are shown here for the purpose of processing a film for magnetic tape.

Various support devices can be used depending on the form of the base film for the magnetic recording medium to be processed. For example, a storage type rotary support device can be used.

Electrodes 551 facing each other with the base film to be processed in between
．． 552, one electrode 551 is connected to a variable frequency power source 54, and the other electrode 552 is installed.

Furthermore, a vacuum system for evacuating the inside of the reaction vessel R is provided, and this is a liquid nitrogen trap 57.
．． These vacuum systems include an oil rotary pump 58 and a vacuum controller 59.
rr vacuum degree aii! Maintain at tl.

In operation, the interior of one reaction vessel R is first evacuated by an oil rotary pump until the pressure in the vessel R becomes 103 Tarr or less, and then the raw material gas is supplied into the vessel in a mixed state at a predetermined flow rate.

At this time, the vacuum inside one reaction vessel is 0.01 to 10 Torr.
managed within the range of

Once the film transfer rate and the flow rate of the source gas are stabilized, the variable frequency power supply is turned on. In this way, a plasma polymerized film is formed on the transferring base film.

Note that Ar, N2, He, etc. can be used as the carrier gas.

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

In addition to the above-mentioned high-frequency discharge, plasma generation sources include
Any of microwave discharge, direct current discharge, alternating current discharge, etc. can be used.

Also, the top coat film of plasma polymerized film.

Layered on a ferromagnetic metal thin film.

The 8 thin ferromagnetic metal layers as the underlayer are mainly composed of Co and contain O, and further include Ni and/or as necessary.
Or it has a composition containing Cr.

That is, in a preferred addition, when NI is included, which may consist of Co alone or a NI may consist of Co and Ni, the weight ratio of Co/NI is preferably 1.5 or more.

Furthermore, Cr may be contained in the ferromagnetic metal thin film layer.

When Cr is contained, electromagnetic conversion characteristics are improved, output and S/N ratio are improved, and film strength is also improved.

In such cases, Cr/Co or Cr/(C
o+Ni) ji weight ratio 0.0O1 to 0. l, more preferably o, oos to 0.05.

Furthermore, 0 is contained in the ferromagnetic metal thin film.

The average amount of oxygen in a ferromagnetic metal thin film is an atomic ratio.

In particular, the atomic ratio of O/(Co or Co+Ni) is 0.5
Hereinafter, it is more preferably 0.05 to 0.5.

In this case, oxygen forms an oxide with the ferromagnetic metal (Co, Ni) on the surface of the first ferromagnetic metal thin film layer.

That is, in the surface area, particularly in the thickness range of 50 to 500, more preferably 50 to 200, from the surface, a peak indicating a sulfide is observed by Auger spectroscopy. The oxygen content of this oxide layer is about 0.5 to i,0 in atomic ratio.

In addition, in such a ferromagnetic metal thin film.

Furthermore, other trace components, especially transition elements such as Fe, Mn
, V, Zr, Nb, Ta, Ti.

Zn, Mo, W, Cu, etc. may be included.

In a preferred embodiment, such a ferromagnetic metal thin film layer is composed of an aggregate of columnar crystal grains mainly composed of Co as described above.

In this case, the thickness of the ferromagnetic metal thin film layer is.

0.05-0.5 m, preferably 0.07-0.3
It is said to be JLm.

The columnar crystal grains have a length spanning almost the entire thickness direction of the thin film;

Preferably, the angle is inclined within a range of 10 to 70 degrees with respect to the normal to the main surface of the base.

Note that oxygen exists in the form of a compound on the surface of the columnar crystal grains in the surface portion, as described above.

Further, there is no particular restriction on the oxygen concentration gradient of the first ferromagnetic metal thin wA layer.

Moreover, it is preferable that the short axis of the crystal grain has a length of about 50 to 500 grains.

The substrate on which such a ferromagnetic metal thin film layer is formed is not particularly limited as long as it is non-magnetic, but it is particularly preferable to use a flexible substrate, especially one made of resin such as polyester or polyimide. Preferably, "Also, the thickness may be a, but especially 5".
It is preferable that it is 204 m.

In this case, on the back side of the ferromagnetic metal thin film layer forming surface of the substrate,
Various known backcoat patterns may be formed.

In addition, the substrate and the ferromagnetic metal thin 1111! ’ between.

If necessary, various known underlayers may be interposed.

Furthermore, if necessary, the ferromagnetic metal thin film layer may be divided into a plurality of parts, and a non-ferromagnetic metal thin film layer may be interposed between them.

The magnetic layer can be formed by electrolytic vapor deposition, ion blating, etc., but it is preferably formed by a so-called oblique vapor deposition method.

In this case, the minimum value of the incident angle of the thinly deposited substance with respect to the normal to the substrate is preferably 200 or more.

When the incident angle is less than 20'', the electromagnetic displacement characteristics deteriorate.

Note that the M deposition atmosphere is usually an atmosphere containing oxygen gas in an inert atmosphere such as argon, helium, or vacuum;
The pressure may be approximately o-sxxoo Pa, and the leather application distance, substrate conveyance direction, structure and arrangement of cans and busks, etc. may be the same as known conditions.

Then, a metal oxide film is formed on one surface by vapor deposition in an oxygen atmosphere. Note that the oxygen gas partial pressure at which metal oxides are formed can be easily determined through experiments.

Note that various oxidation treatments can be used to form a metal oxide film on one surface.

Applicable oxidation treatments include the following.

l) Dry process a, energetic particle process As noted in Japanese Patent Application No. 76840/1982, oxygen is applied to the magnetic layer as energetic particles using an ion gun or a neutral gun in the latter stage of vapor deposition.

b. Glow treatment 02, N20, 02 +H20, etc.! :Ar.

An inert gas such as N2 is used to generate plasma by glow discharge, and the surface of the magnetic film is exposed to this plasma.

C1 oxidizing gas Items that spray oxidizing gas such as ozone or heated steam.

d, Heat treatment: Oxidation is performed by heating, heating temperature is 60-15
Around 0℃.

2) Wet treatment a, anodic oxidation, alkaline treatment C1 acid treatment, chromate treatment, permanganate treatment, phosphate treatment, etc. are used.

d. Oxidizing agent treatment H2O2 etc. are used.

■Specific Effects of the Invention According to the present invention, a magnetic recording medium having a plasma polymerized film containing carbon and fluorine on a ferromagnetic metal thin film layer formed on a support has low running friction and It has sufficient corrosion resistance and also has the effect of not causing a decrease in reproduction output.

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

Example 1 While a 10 pm polyethylene terephthalate (PET) substrate was run along a cooling roll provided in a vacuum chamber, a Co-Ni alloy was heated with an EB gun and evaporated while introducing 02.

In this case, the background pressure is 5×10′ T
orr, the pressure after introducing 02 is 2 X l O-4Tar
It was set as t.

Also, the incident angle of deposition was continuously decreased from 90° to 30′.

The composition was Co8O-Ni20 (weight ratio), and the M thickness was about 1500.

Then, put it in a vacuum chamber and heat it for 10'T.
It was pulled to a vacuum of orr. Then, gaseous hexafluoropropylene is added to A as a carrier gas.
It was introduced at a ratio of r11:l. After that, the gas pressure is 0
, 500W while keeping 1 forr, 13.56
Generate plasma by applying a high frequency voltage of MHz,
A plasma polymerized film was formed on the magnetic layer.

The thickness of the plasma polymerized film formed here was 10 people.

In addition, the W/FM value is 3X l O', and the C/F ratio is 1.
It was 0 (sample No. 1).

According to this, a top coat layer shown in Table 1 below was formed on the magnetic layer.

Furthermore, the elemental analysis of these top coat layers is as follows.

Topcoat e was ion-etched with argon and then measured using SIMS.

Characteristics of each of these samples were measured.

The characteristics were measured as follows.

(1) Running friction Measured at 20°C and 60% relative humidity.

(2) Corrosion resistance Initially and at 60°C and 80% relative humidity.

After storage for 3 days, Δφm/φm (%) was measured.

(3) After running 50 output passes, the amount of signal reduction (dB) at 4 MHz was measured.

From these results, the effects of the present invention are clear.

[Brief explanation of the drawing]

Figure %1 is a schematic diagram of a plasma processing apparatus using direct current, alternating current, and variable frequency power sources. Explanation of symbols 53...Mixer. 54...DC, AC and variable frequency power supply, 57
...Liquid nitrogen trap. 58...Oil rotary pump. 511.512...processing gas source, 521.522...mass flow controller. 561.562...Feeding and winding roll Applicant: TDC Co., Ltd. FIG, I Procedural amendment button August 12, 1985 Patent application No. 237353 2, Name of invention Magnetic recording medium 3. Relationship with the case of the person making the amendment Patent applicant address: 13-1 Nihonbashi-chome, Chuo-ku, Tokyo
(306) Representative of TDC Co., Ltd.
Hiroshi Otoshi 4, Agent 101 Telephone 864-4498 Address 3-2-2 Iwamoto-cho, Chiyoda-ku, Tokyo Column 6 of "Detailed Description of the Invention" of the Specification, Contents of Amendment (1) Specification No. r103J on page 12, line 17, rlO
Correct it with 'J.

Claims (4)

[Claims] (1) In a magnetic recording medium having a ferromagnetic metal thin film on a support and a top coat film on the ferromagnetic metal thin film, the top coat film contains carbon and fluorine, and the atomic ratio of fluorine/carbon is is 0.3 to 2, the film thickness is 10 to 40λ, and the contact angle with water is 100
A magnetic recording medium characterized in that the angle is 130°. (2) Formation of plasma polymerized film is performed using W/FM (where W is plasma input power, F is raw material gas flow rate,
M is the raw material gas molecular weight) is 10^7 to 10^1^2jou
The magnetic recording medium according to claim 1, which is conducted under the condition of le/kg. (3) The magnetic recording medium according to claim 1 or 2, wherein the ferromagnetic metal thin film is a metal thin film mainly composed of Co. (4) The magnetic recording medium according to claim 3, wherein the ferromagnetic metal thin film contains O.