JPS61220118A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To reduce clogging and to improve the corrosion resistance, lubricity and head touch of the title medium by forming a fluoropolymer film satisfying the specified conditions on a continuous thin film-type magnetic layer on a substrate as the topcoat film. CONSTITUTION:The magnetic recording medium has a magnetic layer on a substrate and various kinds of continuous thin film-type ferromagnetic metallic thin films are used for the magnetic layer. A topcoat film consisting of a fluoropolymer is formed on the magnetic layer by vapor deposition. A fluoropolymer is used in the vapor deposition. the contact angle between the topcoat film and water is preferably regulated to 90-120 deg.. Traveling friction is increased at <90 deg. contact angle. Meanwhile, a decrease in the output is increased at >120 deg. contact angle and the medium can not be practically used. Besides, the thickness of the topcoat film is regulated to 5-100Angstrom . At this time, the characteristics are balanced. The clogging is thus reduced and the corrosion resistance, lubricity and head touch are improved.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvements in top coat films for magnetic recording media, particularly magnetic recording media having a continuous thin film 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, Co-Ni, Co, Co-Ni, etc., which is formed by the so-called oblique evaporation method, in which evaporation is performed at a predetermined angle with respect to the normal to the substrate.
Co-0, Co-Ni-0, etc. vapor deposited films are most suitable.

However, such a magnetic layer has high running friction, low film strength, poor head touch, low running durability, low output due to repeated running, and low corrosion resistance (I/).

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 for obliquely deposited magnetic layers have been proposed.

For example, evaporated or coated films of straight-chain saturated fatty acids or their esters (JP-A-53-88704, JP-A-55-9)
3533, etc.).

However, conventional linear fatty acid top coat films have high running friction, poor corrosion resistance, clogging of heads, and poor running durability.Repeated running increases running friction and reduces output. arise.

Further, Co--Cr or the like was deposited as a magnetic layer by vapor deposition and sputtering. Problems similar to those described above also occur with so-called perpendicular magnetization films.

■ Purpose of the Invention The present invention was developed in view of the above-mentioned circumstances, and its main purpose is to provide a top coat film that is less likely to clog, has excellent corrosion resistance, lubricity, head touchability, and has high running durability. An object of the present invention is to provide a magnetic recording medium having a continuous thin S-shaped magnetic layer.

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

That is, the present invention.

A magnetic recording medium having a continuous thin film type magnetic layer on a substrate and a top coat film on the magnetic layer.

The magnetic recording medium is characterized in that the top coat film is a fluorine-based polymer film formed by a vapor deposition method.

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

The magnetic recording medium of the present invention has a magnetic layer on a substrate.

The magnetic layer may be a variety of continuous thin ferromagnetic metal thin films.

The ferromagnetic metal thin film includes iron, cobalt, nickel, and other ferromagnetic metals, or Fe-Co, Fe-Ni, Co-
Ni, Fe-Rh, Fe-Cu, Fe-Au, Co-C
u%Co-Au.

Co-Y, Co-La, Go-Pr, Co-Gd, Co-3m, Co-Pt, Ni-Cu,
Fe-Co-Nd, Mn-B1. Mn-5b, Mn-A
l1. Examples include magnetic alloys such as Fe-Co-Cr and Co-Ni-Cr.

Alternatively, CoCr, C which is known as a perpendicular magnetization film
od, CoN1P, CoP, MnB1. MnARGe,
NdFe, NdCo, Co01MnSb, MnCuB1, GdF
e, GdCo, PtCo, TbCo.

TbFeCo, GdFeCo, TbFeO3.

GdIG, GdTbFe.

G d T b Fe Co B i , Co F
e 204 etc. may be used.

These magnetic layers may be directly formed on the substrate by a method such as a vacuum evaporation method, a sputtering method, an ion blasting method, or a plating method, or may be formed via an underlayer.

In this case, in the present invention, Co is an essential component, and C
It is preferable to consist of Co+Ni, Co+O, or Co+Ni+O.

That is, it may consist of Co alone.

4 and Ni.

In the case of Co+Ni, the weight ratio of Co/Ni is 1.5
It is preferable that it is above.

Furthermore, in addition to Co or Co+Ni, 0 may be included. When 0 is included, more favorable results can be obtained in terms of electromagnetic conversion characteristics and running durability.

In such a case, the atomic ratio of O/Co (if Ni is not included) or O/(Co+Ni) is preferably 0.6 or less, particularly 0.15 to 0.5.

On the other hand, the magnetic layer contains Co, Co+Ni.

When Cr is contained in addition to Co+O or Co+Ni+O, even more favorable results are obtained.

This is because electromagnetic conversion characteristics are improved, output and S/N ratio are improved, and film strength is further improved.

In such cases, Cr/Co (if Ni is not included)
Or the weight ratio of Cr/(Co+Ni) is 0.001
˜0.l is preferable.

In this case Cr/Co or Cr/(Co+Ni)
When the weight ratio of is 0.005 to 0805, even more preferable results are obtained.

Note that such a magnetic layer also contains other trace components,
Especially transition metal elements, such as Fe.

M n , V , Z r , N b , T a
, M o W , T i .

Cu, Zn, etc. may be included.

Such a Co-Ni magnetic layer is usually used.

It is preferable that there is an aggregate of particles having a columnar crystal structure tilted with respect to the normal to the main surface of the substrate. This improves electromagnetic conversion characteristics.

In such a case, the particles having a columnar crystal structure are preferably inclined at an angle of 20 to 60 degrees with respect to the normal to the main surface of the substrate.

Further, each columnar crystal grain usually has a length spanning the entire thickness direction of the magnetic layer, and its breadth is generally about 50 to 500.

Then, Co and Ni added as necessary.

Cr etc. constitute this columnar crystal itself, and O
When 0 is added, 0 usually exists mainly in the form of oxide on the surface of each columnar crystal grain.

Such a Co--Ni magnetic layer is usually formed by an oblique evaporation method.

As the oblique evaporation method used, a known oblique evaporation method may be used, and the minimum value of the incident angle with respect to the normal to the substrate is preferably 30° or more.

Incidentally, the vapor deposition conditions, post-treatment method, etc. may be in accordance with known conditions and methods. In this case, effective post-treatment methods include various known treatment methods for introducing zero into the magnetic layer. .

Such a magnetic layer is usually formed to a thickness of 0.05 to 0.5 JL layer.

In this case, the magnetic layer may be provided directly on the substrate, or may be provided on the substrate via an underlayer.

Further, although the magnetic layer is usually formed as a single layer, it may be formed by laminating a plurality of layers with an intermediate layer interposed therebetween as the case may be.

A top coat film made of a fluorine-based polymer is formed on such a magnetic layer.

Such a top coat film is formed by a vapor deposition method.

Regardless of the vapor deposition method, when coating is used, there arises the disadvantage that it is difficult to reduce the film thickness and form a layer with a uniform thickness.

For vapor deposition, a fluororesin may be used.

Here, the fluororesins used include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyvinyl fluoride (PVF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoroethylene. -Ethylene copolymer (ETFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PF
A), chlorotrifluoroethylene-ethylene copolymer (
ECTFE), etc. Among these, polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FE)
P), tetrafluoroethylene-ethylene copolymer (
E T F E) is commonly used.

Moreover, it is preferable that the average degree of polymerization of the fluororesin used as the evaporation source is about 700 to 3000.

The fluorine content is preferably 30 to 80 mol% per average repeating unit.

Further, the contact angle with water of the top coat film having such a composition is preferably 90 to 120@.

In this case, if the 11i antennae is less than 90'', the running friction is too large to withstand practical use, and the running durability is also poor.

On the other hand, if the angle exceeds 120°, the output decreases so much that it is not practical.

Such a topcoat film may have a thickness of 5 to 100 nm. At this time, the balance of characteristics is maintained.

In this case, the film thickness can be measured using an ellipsometer.

In addition, the formation of fluoropolymer during vapor deposition,
The contact angle of the surface depends on the substrate temperature, substrate-to-hearth spacing, operating pressure, etc. The conditions can be easily determined experimentally for each manufacturing device.

Usually, the distance between the substrate and the hearth is about 1 to 20 cm, and the temperature of the substrate is about 30@.

As the evaporation source, any of a resistance heating evaporation source, a high frequency heating evaporation source, etc. may be used.

The fluorine-based polymer film deposited in this manner preferably has a fluorine/carbon atomic ratio of about 15 to 3.

If it falls outside this range, running durability will decrease.

Note that hydrogen may be contained in the polymer film in a range of 50 at % or less.

Similarly, chlorine or the like may be contained in a range of 10% at or less.

Further, the composition in the film may be identified by ESCA, SIMS (secondary ion mass spectrometry), or the like.

The substrate to be used is not particularly limited, but particularly flexible substrates, particularly polyester and polyimide.

It is preferably made of resin such as phoriflovirene.

In addition, the thickness may be various, but especially 5.
~ “201L Maro is preferable.

A back coat layer is preferably provided on the back side of the magnetic layer forming surface.

(2) Specific effects of the invention The magnetic recording medium of the present invention is useful as a magnetic recording medium for video, audio, and the like.

According to the present invention, the top coat film of the magnetic recording medium is formed by a vapor deposition method, and since the film is made of a fluorine-based polymer, running friction is low, and running durability is particularly improved.
It has excellent corrosion resistance and exhibits an excellent effect of reducing clogging.

■Specific embodiments of the invention Specific examples of the present invention will be described in detail below.

Example Co/Ni (7) Weight ratio 4/l no Co
Using a Ni alloy, a 10 g layer of polyethylene terephthalate (PET) film was deposited using an oblique vapor deposition method.
A sample An was prepared by forming a magnetic layer with a thickness of 0.2 vol.

The incident angle in the oblique evaporation method was 45°, and the evaporation atmosphere was as follows.

F A, = 2 x 10-” P a -P
= IX10-”Pa The obtained magnetic layer has the corresponding alloy composition and 0/
(Co+N1)=0.2 (atomic ratio), and is an aggregate of columnar crystal grains grown over the entire thickness direction with a minor axis of 0.01 μm and inclined at approximately 40 degrees with respect to the normal to the main surface of the substrate. there were.

Furthermore, when performing Auger spectroscopy analysis while performing ion etching, it was found that Co was less near the surface, and O was chemically shifted, with a profile in which it was more abundant near the surface. It was confirmed that it exists in a combined state.

Next, in order to deposit a fluoropolymer on the An magnetic layer, Polyflon T was used as a fluoropolymer as an evaporation source.
FE (manufactured by Daikin Industries) and Teflon FEP (manufactured by DuPont) were used.

Atmospheric pressure P a, = I X l O-! At Pa, the substrate temperature and substrate-evaporation source distance were changed to a film thickness of 50, and a fluorine-based polyester having a contact angle with water shown in Table 1 was used.
Coat the sample with topcoat II of A1.
~A3 was obtained.

Note that the film composition was identified by ESCA.

In addition, in order to confirm the effects of the present invention, a top coat film was prepared in which Teflon (a low molecular weight product: product name PIDAX, film thickness 1Oλ) was coated on the magnetic layer, and stearic acid was vapor-deposited as a fatty acid. (film thickness: 10 layers) and one without a top coat layer were used as comparative examples (sample defects, Ao, A4, A5).

The following measurements were performed for each of these samples.

1) Running Durability A 50-bus test was conducted on each sample using a commercially available VTR device, and the amount of reduction (dB) in the 4 MHz signal was measured.

2) Corrosion resistance The sample was stored in an atmosphere of 60° C. and 90% RH for 70 days, and the rate of change in saturation magnetic flux density Δφmaro/φmaro (%) was measured.

3) Clogged The number of times clogging occurred during the 100 pass test was measured.

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

Claims (3)

[Claims] (1) In a magnetic recording medium that has a continuous thin magnetic layer on a substrate and a top coat film on this magnetic layer, the top coat film is a fluorine-based polymer film formed by a vapor deposition method. A magnetic recording medium characterized by: (2) The magnetic recording medium according to claim 1, wherein the top coat film has a thickness of 5 to 100 Å. (3) Claim 1 or 2, wherein the top coat film has a contact angle with water of 90 to 120°.
The magnetic recording medium described in section.