JPH04188430A - Magnetic recording tape having excellent abrasion resistance and corrosion resistance and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve abrasion resistance and corrosion resistance, and to prevent damage to the counterpart at the time of contact by forming a non- magnetic thin-film, in which an iron-group double boride group hard alloy composed of Mo2FeB2 type double boride group hard phase and iron-group bond phase containing Cr, Mo and Ni is used and which consists of a specific composition and has film thickness of 10-10000Angstrom , as a protective film. CONSTITUTION:A non-magnetic thin-film, in which an iron-group double boride group hard alloy made of Mo2FeB2 type double boride group hard phase and iron-group bond phase containing Cr, Mo and Ni is employed and which is composed of the composition of Fe: 25wt.% or less, B+Mo: 60wt.% or less and Cr+Ni: the remainder and has film thickness of 10-10000Angstrom , is formed on the surface and/or the rear of a magnetic recording tape as a protective film. It is advantageous that the atomic ratio B/Mo of B to Mo in the iron- group double boride group hard alloy is kept within a range of 0.5-1.5. Accordingly, abrasion resistance and corrosion resistance are improved, and the magnetic recording tape damaging light abrasion to the counterpart can be acquired.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a magnetic recording tape with excellent wear resistance and corrosion resistance, and a method for manufacturing the same.

(Conventional technology) In the present age, advanced information technology is particularly important, as it is called the advanced information age.

Magnetic recording media, such as floppy disks and video tapes, play a role in supporting this advanced information technology. Among them, flexible tapes using CoCr perpendicular magnetic recording media are the next generation video media, HDT.
V (H,igh Definition TV)
It is expected to be used as a TR medium.

Incidentally, such magnetic recording media are required to have corrosion resistance from the viewpoint of long-term storage of records, and wear resistance from the viewpoint of high-speed contact between the medium surface and the sensor during use.

Therefore, for magnetic recording tapes in which a magnetic recording medium is formed on a plastic substrate, a top coat is applied to the surface to protect the surface of the magnetic recording medium, and also to prevent static electricity and lower the coefficient of friction on the tape surface to improve the slippage between the tapes. From this point of view, is it necessary to apply a back coat to the reverse side?

Hitherto, various thin films of carbon, carbide, nitride, etc. have been studied for this purpose, and research on diamond-like thin films has recently been progressing. However, it has not been possible to obtain a fully satisfactory performance, and it has been pointed out that this is a drawback in that it can cause damage to the other side, especially the head that comes into contact with the medium.

In addition to polyimide tape, thermoplastic tapes such as polyethylene naphthalate tape and polyethylene terephthalate tape are said to be suitable as substrates for magnetic recording tapes, but since such thermoplastic tapes generally have poor heat resistance, Another problem remains that the film is susceptible to thermal damage during film formation.

(Problems to be Solved by the Invention) The present invention advantageously solves the above problems, and is a magnetic recording medium having a protective coating that is excellent in wear resistance and corrosion resistance, and does not cause damage to the other party upon contact. The purpose is to propose a tape together with an advantageous manufacturing method thereof.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the inventors conducted intensive research and came up with the idea of utilizing an iron-based complex boride alloy as a material for the protective coating.

Although such alloys have excellent properties as high-hardness materials, they have poor wettability with various metals and it is difficult to obtain dense sintered bodies, so there have been few examples of their application as practical materials.

However, among these, iron-based hard alloys consisting of a Mo2FeB2 type double-boride hard phase and an iron-based binder phase containing Cr, Mo, Ni, etc. are (1)
Excellent wear resistance; (2) minimal wear of the mating material; (3) high corrosion resistance and high temperature oxidation resistance; (4) magnetic properties cannot be changed by changing the composition of the binder phase. If such an alloy can be made into a thin film by some method and coated on the surface of the tape substrate without causing thermal damage, its wear resistance and corrosion resistance will improve. We can expect an improvement in this.

Until now, such iron-based complex boride hard alloys have only been used in so-called bulk form, such as copper hot extrusion dies, injection molding machine parts, and seaming rolls for can manufacturing, and have been used in thin films of 1 μm or less. There have been no attempts to use it as such.

The inventors then conducted repeated studies on a method for thinning the iron-based double boride hard alloy, and found that if facing target sputtering was used, the tape substrate would not be damaged by plasma during film formation. (Moreover, we have found that the above alloy can be advantageously formed into a film.

This invention is based on the above knowledge.

That is, the present invention provides a magnetic recording tape surface and 7/7
Or as a protective coating on the back side, an iron-based double boride hard alloy consisting of a MO□FeB2 type double boride hard phase and an iron-based binder phase containing Cr, Mo and N1, Fe: 251vt94 or less, B + Mo: 60 wt945 or less, 1::r+N
i: A magnetic recording tape (first invention) having a non-magnetic thin film having the same composition and having a film thickness of 10 to 10,000, and having excellent wear resistance and corrosion resistance.

Further, the present invention provides a method for applying a MO□FeB2 type double boride hard phase to the front and/or back surface of a tape substrate having a magnetic recording medium by a facing target sputtering method.
An iron-based double boride hard alloy consisting of an iron-based binder phase containing r, Mo and Ni, Fe: 25 wt.
Production of a magnetic recording tape with excellent abrasion resistance and corrosion resistance, consisting of an alloy with a film thickness of 10 to 10,000 %, B 10 Mo: 60 wt % or less, Cr + Ni: the remaining composition. This is a method (second invention).

In this invention, it is advantageous that the atomic ratio B/Mo of B and MO in the iron-based complex boride hard alloy is in the range of 0.5 to 1.5. This is because in this range, Mo2
This is because it is easy to obtain the hard phase of FeB2.

In particular, according to the second invention, when applying the top coat and/or back coat to the magnetic recording tape, it is preferable to apply the top coat and/or back coat to the magnetic recording tape without applying an RF (for example, 13.56 MHz) bias to the tape substrate. This is because such a bias application method changes the surface morphology of the protective film (
This is because it is possible to control unevenness.

Furthermore, in the second invention, as the magnetic recording tape to be coated with the protective coating, any conventionally known magnetic recording tape is suitable, and it does not matter whether it is a longitudinal magnetic recording medium or a perpendicular magnetic recording medium. Perpendicular magnetic recording tape is advantageously suitable.

(Function) As mentioned above, the magnetic properties of iron-based complex boride hard alloys can be changed by changing the composition of the binder phase. Therefore, when we investigated the composition range that would be non-magnetic, we found that if we use a target with a composition of Fe: 25 wt% or less, B + Mo: 60 wt% or less, and Cr + Ni: the remaining composition, a non-magnetic film with the same composition can be obtained. It turned out. Therefore, if a nonmagnetic film having such a composition can be used as a top coat and a back coat of a magnetic recording medium, it is expected that the wear resistance and corrosion resistance of the magnetic recording tape will be greatly improved.

B: 5.85wt%, Mo: 43.9wt%,
Cr: 20.6wt% and Ni: 8.2w
A top coat was applied on the CoCrTa magnetic recording layer using a target with an alloy having a composition of 1.5% and the remainder was essentially Fe, and the presence or absence of changes in the M-H loop of the magnetic recording medium was investigated at this time. clumsy.

First, the results of measuring the saturation magnetization of the target using VSM are as follows.
It was confirmed that the value was 0.2 efflu/cc or less, and that it was substantially non-magnetic.

Next, polyethylene naphthalate (PE) with a thickness of 11 μm was
N) On the tape, by facing Turkerato sputtering method,
(1500 people - COgoCr+ = Ta3/PEN) and (
1500 people - Protective film / 1500 people - CogoCr+1T
As/PEN) two types of membranes were made and the M-H loops of each membrane were compared.

The results are shown in FIGS. 1a and 1b, respectively.

As is clear from the figure, M
There was no change in the -H loop, thus confirming that the protective coating did not adversely affect magnetic properties.

By the way, in addition to polyimide tape, thermoplastic tapes such as polyethylene naphthalate tape and polyethylene terephthalate tape are said to be suitable as substrate tapes for magnetic recording tapes, but since these types of tapes usually have poor heat resistance, A condition required for the film formation method is that the tape is not thermally damaged.

Therefore, we next investigated the film formation method.

Since iron-based complex boride hard alloys have electrical conductivity,
After converting the gas into neutral, ionic, or excited atomic, molecular, or cluster gas through a plasma dry process in vacuum, the gas is rapidly agglomerated on the surface of an object in vacuum, resulting in a film with a thickness of 10 to 10 mm. It can be made into a thin film of 10,000 people.

According to the second method, the object to be coated can be coated regardless of its shape, as long as the object to be coated is brought to an appropriate degree of vacuum in a vacuum chamber. Therefore, we tried various film-forming methods and found that by using the facing target sputtering method, the film can be formed in a plasma-free state where the object to be processed is not exposed to plasma, and it is relatively resistant to thermal damage like plastic thin films. It was discovered that it is possible to coat delicate objects without causing damage.

Here, the facing target sputtering method refers to the method of sputtering using two target sputtering sheets (approximately 10 x 10 x 10 pieces) as shown in Figure 2.
1. , 1. -2 with their faces facing each other with a distance of about 10c+n, and a magnetic pole 2-1.2-2, which can be made of a permanent magnet, is installed on the back side of each target 1-1.1-2. This method performs sputtering without confining plasma between two targets by running a magnetic field between the targets perpendicular to each target surface. At this time,
The coated substrate is 3~ from the edge of the two targets 1-1.12.
Placed 10CI [l apart, perpendicular to the target plane and centered between the targets.

Therefore, the substrate is not exposed to plasma and can be deposited in a plasma-free state. In this sputtering, the sputtering Ar gas pressure p Ar is preferably about 5 mTorr or less. Further, in the figure, 3 is a mask, 4 is a slit provided in the mask 3, 5 is a flexible tape serving as a substrate, 6 is a can roll, and 7 is a matching circuit for applying a PR bias.

In sputtering using an alloy target, although the target composition and film composition may generally differ, plasma-free facing target sputtering can minimize this difference.

Generally, the target and the sputtered film may have different magnetic properties, but in this respect, there is no difference in the facing target sputtering method, and if a target with a non-magnetic composition is used, a non-magnetic coating film can be obtained. was confirmed.

Furthermore, when applying a top coat and/or back coat, the tape substrate may be exposed to RF (e.g. 13.56 MHz
If the film is formed while applying a bias voltage of It has been found that this is particularly advantageous in obtaining a friction coefficient of .

11μm thick polyethylene naphthalene) (PEN)
When back-coating onto the tape, the surface unevenness was investigated when the film was formed without applying an RF bias of 13.56 MHz to the can roll.

In the second case, the potential of the tape substrate was 1100 mm lower than the ground, and the Ar gas pressure was in the range of 0.25 mTorr to 4 mTorr.

As a result, it was found that when no bias was applied, unevenness was observed on the surface, but when a bias was applied, the surface unevenness was reduced. It has also been found that this surface unevenness reducing effect is even more pronounced at low gas pressures.

(Example) Preliminary experiment B: 5.85wt? +5, Mo: 43.9wt
'6, Cr: 20.6wt06 and Ni: 8
．． Using a 1010 x 10" square alloy as a target containing 2 Wt94 and the remainder being essentially Fe, it was sputtered onto a 10 μm thick polyethylene naphthalate tape and a glass substrate at room temperature using a facing target sputtering method. The thin films were deposited to a thickness of 1,500 mm.At this time, the sputtering was performed at an argon gas pressure of 0.25 to 4.0 mTorr.Those on glass substrates were further annealed in vacuum at 400'C for 11 hours.For these thin films, The crystal structure was investigated using X-ray diffraction, and the magnetic properties were investigated using VSM.

Before annealing, no X-ray diffraction peaks appeared for the films on either substrate, indicating that they were amorphous films.

It was also found that no crystalline structure appeared even after the above annealing, and that the amorphous structure was stable. Furthermore, the VSM
It was also found that there are films that are more non-magnetic.

Example 1 The amorphous film used in the preliminary experiment was flexible and had a dense structure because it was produced plasma-free using the facing Turkerato sputtering method. Moreover, it was a nonmagnetic film, so it was prototyped as a back coat for a magnetic recording tape. did. The magnetic recording tape used was a 750A N18oFe2o backing layer on top of a 750A N18oFe2o backing layer on each inch wide and 11 μm thick polyimide tape and an additional 1500 CO□gcr2 on top.
It is coated with a + layer.

A can roll with a diameter of about 15 cm was installed at the position of the coated substrate, and while the magnetic recording tape was conveyed in synchronization with the rotation of this roll, a film having the same composition as in the preliminary experiment was continuously deposited on the back side of the tape. The film was coated to a thickness of 800 people.

In this example, it was investigated whether the backcoat layer formation process would not have a negative magnetic effect on the backcoat layer or the magnetic recording layer, and whether it would cause thermal damage to the magnetic recording layer and the polyimide tape.

As a result, it was confirmed that there was no change in the magnetic properties of the COvgCrz□ layer after backcoating, and that there was no damage such as thermal deformation of the tape.

Example 2 The coefficient of friction of the coated surface of the tape prepared in Example 1 was evaluated. 1) Tension T using the device shown in Figure 3
2 was measured, and the friction coefficient was determined from Euler's equation. Note that Euler's equation is expressed as -2 and □'In(T2/Tl) for μ.

As a result, the friction coefficient of the polyimide tape surface without a back coat was as large as 0.46, whereas
The coefficient of friction on the back-coated surface was significantly lower at 0.29. This value is approximately equal to 0.28, which is the value of the tape surface of a commercially available coated tape, indicating that the coefficient of friction has been improved to a level equivalent to that of a commercially available tape. Therefore, it is expected that such a backcoat will reduce the friction between the tapes and increase the durability of the magnetic tape.

(Effects of the Invention) Thus, according to the first invention, it is possible to obtain a magnetic recording tape which is excellent in abrasion resistance and corrosion resistance, and in which the mating material is only slightly abraded.

Further, according to the second invention, since the film can be formed in a plasma-free situation where the object to be processed is not exposed to plasma, it is possible to prevent damage even on a tape substrate, such as a plastic tape, which is relatively susceptible to thermal damage. It can be coated with a protective film without any second need.

[Brief explanation of drawings]

111a and 111b are diagrams respectively showing the M-H loop with and without a protective coating according to the present invention; FIG. 2 is a perspective view of a facing target type sputtering apparatus; FIG. , is a schematic diagram of a friction coefficient measuring device. 1-1. i2...Target 2-1. 2-2・
...Magnetic pole 3...Mask 4...Slit 5...
・・Board tape 6・・Can roll 7・・Matching circuit 3・−Mask A−−−・Suji nod 5−・1 Hayashi‐r‐7゛6−−−−Kya′/roll 7−−− −Temporary implicature circuit

Claims (1)

[Claims] 1. As a protective coating on the front and/or back surface of the magnetic recording tape, a Mo_2FeB_2 type double boride hard phase and Cr, M
An iron-based complex boride-based hard alloy consisting of an iron-based binder phase containing O and Ni, the composition of which is Fe: 25 wt% or less, B + Mo: 60 wt% or less, Cr + Ni: the remainder, and the film thickness is 10 to 10%. A magnetic recording tape with excellent wear resistance and corrosion resistance, characterized by having a nonmagnetic thin film of 10,000 Å. 2. The magnetic recording tape according to claim 1, wherein the iron-based double boride hard alloy has an atomic ratio B/Mo of B and Mo of 0.5 to 1.5, which has excellent wear resistance and corrosion resistance. 3. A magnetic recording tape with excellent wear resistance and corrosion resistance according to claim 1 or 2, wherein the magnetic recording tape to be coated with the protective coating is a CoCr perpendicular magnetic recording tape. 4. The surface of the tape substrate containing the magnetic recording medium and/or
Or, on the back side, M
o_2FeB_2 type double boride hard phase and Cr, Mo
and an iron-based binder phase containing Ni, the alloy having a composition of Fe: 25 wt% or less, B + Mo: 60 wt% or less, and Cr + Ni: the remaining composition, film thickness: 10 ~ A method for manufacturing a magnetic recording tape having excellent wear resistance and corrosion resistance, characterized by coating the tape with a thickness of 10,000 Å. 5. A method of manufacturing a magnetic recording tape having excellent wear resistance and corrosion resistance, which comprises forming a top coat and/or back coat thin film while applying an RF bias to the tape substrate as claimed in claim 4. 6. A magnetic recording tape having excellent wear resistance and corrosion resistance according to claim 4 or 5, wherein the magnetic recording tape to be coated with the protective coating is a CoCr perpendicular magnetic recording tape.