JPH01184713A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve head touch, traveling property and durability by using a thin-film magnetic layer consisting of an iron nitride system and providing the rugged shapes of the surface and a plasma-polymerized layer and further a back layer. CONSTITUTION:A primer coating layer 2, the thin-film magnetic layer 3 consisting of the iron nitride system and the plasma-polymerized layer 4 are laminated in this order on one side of a nonmagnetic base and the back layer 5 having 200-2,000Angstrom surface roughness is provided on the opposite side. The primer coating layer 2 is formed by dispersing fine particles into an org. binder and projecting parts 2a are formed on the surface of the primer coating layer 2. As a result, the ruggedness having less unequalness is formed on the surface of the plasma-polymerized layer 4 which is the uppermost surface layer by the projecting parts 2a uniformly distributed over the entire area of the primer coating layer. A protective layer having the ruggedness on such a hard film as an iron nitride film is formed, by which the cushion effect between a tape and head is effectively acted and the good head touch is maintained. The friction resistance to the head is thus adequately maintained and the wear resistance of the head is substantially improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic recording medium in which a ferromagnetic metal thin film is provided as a magnetic recording layer on a non-magnetic support, and particularly relates to a magnetic recording medium having a ferromagnetic metal thin film provided as a magnetic recording layer on a non-magnetic support. The present invention relates to magnetic recording media that are excellent in such things as magnetic recording media.

[Prior art]

Conventionally, as a magnetic recording medium, r
Fears, Co-doped r-Fe, 0. , Fe
J4, Go-doped Pe5ts, r-Fer
Bertolide compound of n, l and Fe, 04, Cry
A powder magnetic material such as magnetic powder such as @ or ferromagnetic alloy powder dispersed in an organic binder such as vinyl chloride-vinyl acetate copolymer, styrene-butadiene copolymer, epoxy resin, polyurethane resin, etc. is applied. Dry coating types have been widely used. In recent years, with the increasing demand for high-density recording, magnetic recording layers are made of ferromagnetic metal thin films formed by paper deposition methods such as vacuum evaporation, sputtering, and ion blating, or plating methods such as electroplating and electroless plating. So-called metal thin film magnetic recording media that do not use a binder are attracting attention, and various efforts are being made to put them into practical use.

Conventional coating-type magnetic recording media mainly use metal oxides, which have lower saturation magnetization than ferromagnetic metals, as magnetic materials, so the thinning required for high-density recording leads to a reduction in signal output, which has reached its limit. Moreover, the manufacturing process is complicated, and it has the drawback of requiring large auxiliary equipment for solvent recovery and pollution prevention. Metal thin film type magnetic recording media have the advantage that they can be made ultra-thin and capable of high-density recording because a ferromagnetic metal with a higher saturation magnetization than the above-mentioned oxides is formed as a thin film without containing a non-magnetic substance such as a binder. Moreover, the manufacturing process is simple.

As one of the requirements for magnetic recording media for high-density recording, high coercive force and thinness have been proposed both theoretically and experimentally. There are great expectations for metal thin film magnetic recording media, which can be easily made small and thin and have a high saturation magnetic flux density.

Furthermore, major problems concerning magnetic recording media made of ferromagnetic metal thin films include strength against corrosion and abrasion, and running stability. A magnetic recording medium is subjected to high-speed relative motion with a magnetic head during the recording, reproducing, and erasing processes of magnetic signals, but in this case, the medium must move smoothly and maintain stable spacing loss with the magnetic head. It's not true,
At the same time, wear or magnetic breakdown due to contact with the head must not occur.

In order to improve the above problem, it has been proposed to provide a plasma polymerized film as a protective layer on a ferromagnetic metal thin film.
No. 59-154641, No. 59-154643, No. 59-160828, No. 59-171028, No. 59-171029, No. 60-22730,
No. 60-35330, No. 60-35331, No. 60
-38727, 60-38728, 60-57
No. 535, No. 60-57536, No. 60-57537
No. 60-63724, No. 60-69825, No. 60-69826, etc. However, conventional metal thin film magnetic recording media with a plasma polymerized film as a protective layer have insufficient lubricity, especially in repeated friction, and in order to improve the repeated friction characteristics, the thickness of the plasma polymerized film must be increased. However, in this case, there is a problem that the electromagnetic conversion characteristics deteriorate and the characteristics of the metal thin film magnetic recording medium cannot be utilized, and an improvement has been strongly desired.

Furthermore, as a non-binder type magnetic recording medium with excellent weather resistance, there is a magnetic thin film made of iron nitride or iron and iron nitride as disclosed in European Patent No. 8328 or Japanese Patent Application Laid-open No. 87809/1983. Improvements in durability were desired.

[Purpose of the invention]

An object of the present invention is to provide a magnetic recording medium that has improved the above-mentioned drawbacks, that is, a magnetic recording medium that has good lubricity, excellent running properties, and excellent electromagnetic conversion characteristics.

[Structure of the invention]

The above-mentioned object of the present invention is to provide an undercoat layer on one side of a non-magnetic support to provide protrusions on the surface of the outermost layer, and to form an iron nitride thin film magnetic layer and a plasma polymerized layer on the undercoat layer in this order. The other surface of the non-magnetic support has a surface roughness of 2.
This can be achieved by a magnetic recording medium provided with a back layer of 0.00 to 2000 layers.

Hereinafter, the present invention will be specifically explained with reference to FIG. 1. Note that FIG. 1 is an enlarged cross-sectional view of a magnetic tape, which is a magnetic recording medium according to the present invention.

As shown in FIG. 1, examples of non-magnetic supports include α-plastic bases such as polyethylene terephthalate, polyimide, polycarbonate, polyvinyl chloride, cellulose triacetate, polyphenylene sulfide, polyamide, etc.
is used.

On one side of this nonmagnetic support 1, an undercoat layer 2, an iron nitride thin film magnetic layer 3, and a plasma polymerized layer 1i4 are laminated in this order. The undercoat N2 is made by dispersing, for example, 5iO1 fine particles with a diameter of 10 to 300 in an organic binder, and the film thickness is in the range of 0.05 μm to 1 μm.
These fine particles create protrusions 2a on the surface of the undercoat 1i2.
is formed. As a result, extremely uniform unevenness is formed on the surface of the plasma polymerized layer 4, which is the uppermost layer, due to the protrusions 2a uniformly distributed over the entire area of the undercoat layer.

The iron nitride thin film magnetic layer 3 provided on the undercoat layer 2 mainly contains elements such as Fe%N, O, etc., and the substance is a -Fes g -Few-s! L r'-
It is a mixture such as FeJsFe2N%FeOx. however,
Containing iron nitride is necessary to improve the corrosion resistance and electromagnetic conversion characteristics of the magnetic tape, especially Fe! -sN to 10
The iron nitride-based thin film magnetic layer 3, which preferably contains % or more in order to ensure corrosion resistance, is produced by, for example, vacuum-depositing Fe while ionizing, exciting, and atomizing nitrogen and sending it into the film-forming area. The membrane speed is fast and simple. The thickness of the iron nitride thin film magnetic layer 3 is 500 to 5,000, preferably 1,000 to 3,000.

The plasma polymerized layer 4 laminated on the iron nitride thin film magnetic layer 3 reduces the frictional force between the magnetic tape and the magnetic head, and improves the durability, abrasion resistance, and corrosion resistance of the tape. It is produced by plasma polymerization of organic monomer gas. Further, this plasma polymerized film will be explained. In the present invention, the plasma polymerized film refers to a film of an organic polymer material formed by polymerizing organic monomer gas on a ferromagnetic metal thin film in plasma generated by discharge excited by DC, AC1 high frequency, microwave, etc. In this case, the organic monomer gas may be directly ionized, or Ar5He, O□,
Organic monomer gas may be introduced during gas discharge such as N2, N2, etc., and the pressure during plasma polymerization is 1 to 10-'
Torr is preferably 0 The thickness of the plasma polymerized film in the present invention is preferably in the range of 20 to 400 Torr, particularly 20 to 20
The organic monomer gas, preferably 0, includes tetrafluoromethane, tetrafluoroethylene, hexafluoroethane, barfluoroprohane, octafluorocyclobutane,
Methane, ethylene, propylene, butylene, vinyl chloride, styrene, chlorobenzene, dimethylsiloxane, hexamethyldisilazane, diethylaminotrimethylsilane, etc. are used alone or in combination.

On the other hand, the opposite surface of the plastic base 1 has a surface roughness of 20
0 to 2000 batters - set up Jl 5. This back layer 5 is provided for stable running of the tape and is a mixed layer of an organic binder containing carbon, calcium carbonate, etc. Surface roughness can be measured using a stylus roughness meter.

If the surface roughness of this backing layer is less than 200 people, the running stability effect will be insufficient. Moreover, if the number of people is larger than 2,000, surface roughness due to reflection on the magnetic layer cannot be ignored.

The magnetic recording medium configured as described above has protrusions 4a on the surface of the magnetic layer side formed by the protrusions 2a of the undercoat layer 2.
By forming a protective layer (plasma polymerized layer 4) with unevenness on a hard film such as iron nitride, the surface does not become flattened and spacing loss is minimized. The cushioning action between the two parts works effectively, making it possible to maintain good head contact, moderate frictional resistance with the head, and substantially improving the wear resistance of the head. In addition, the plasma polymerized layer 4 as the uppermost layer improves lubricity and the like, and improves running performance.

(Effects of the Invention) As described above, according to the present invention, the weather resistance is improved by using the iron nitride-based thin film magnetic layer, and the unevenness of the surface, the plasma polymerized layer, and the back layer make it possible to improve head touch and running. The mechanical properties such as running properties, durability, weather resistance, etc. are dramatically improved due to synergistic effects, and the electromagnetic conversion properties are excellent. A magnetic recording medium can be provided.

〔Example〕

Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

[Example 1] An undercoat layer having the following composition was used on the surface of a support made of a polyethylene terephthalate film having a thickness of 12.5 μm and a width of 100 vm.

Nitrocellulose 25 parts by weight Polyurethane (Product name: Nippo 10 parts by weight Run 2301, manufactured by Nippon Polyurethane ■) Polyisocyanate (Product name: 5 parts by weight Coronate L1 manufactured by Nippon Polyurethane ■) Fine particles of silicon dioxide (SiO□) 12 parts by weight Department (
Methyl ethyl ketone was used as the solvent (particle diameter: 250 particles) to form an undercoat layer with a protrusion density of 2.5 x 10'protrusions/wxr'' on the surface of the undercoat layer.A continuous vapor deposition device was installed on the undercoat layer thus obtained. An iron nitride-based thin film magnetic layer is formed to a thickness of 1500 mm by irradiating a nitrogen ion flow with an ion gun while depositing iron (Fe) using a magnetic layer.The magnetic layer at this time has Hc = 9500e, SQ = 0.7
The film forming conditions are controlled so that the value becomes 0.

The support on which the iron nitride-based thin film magnetic layer was formed was set in a plasma polymerization chamber, and 30 cc of methane gas/MIN and 30 cc of argon gas/ex-N were introduced, and the pressure was increased to 1. OXl0-”
RF plasma was created by applying a high frequency of 13.56 MHz at Torr, and a plasma polymerized layer having a thickness of 200 MHz was formed.

In addition, the back surface of the support (non-magnetic material side) has a surface roughness of 4.
We set up a back layer with 00 people.

The raw tape thus obtained was slit into 8f1 width samples to prepare 8mm video tape cassettes, and the following characteristics were measured.

1. Demagnetization rate (%) The magnetic flux reduction rate after being left for 30 days in an atmosphere of 60° C. and 90% relative humidity was measured.

2. Runability 8 m/m Sample assembled in cassette
Run it at RT. Repeat the cycle of "replay, stop, rewind" every 5 minutes. 1 pass this cycle
It is called. If the output decreases by 3 dB or more from the l-th pass, or if any noise or squeak occurs midway through, the vehicle will be stopped, and the running performance will be evaluated based on this number of passes.

3. Playback with 8 Dragon VTR (Fuji Photo Film FUJ [X-8) per head] and observe the output waveform envelope with an oscilloscope. At this time, the quality of the magnetic tape per head can be determined based on the change in amplitude of the output waveform that appears on the oscilloscope within a certain period of time, that is, the ratio between the maximum amplitude Y max and the minimum amplitude Y min .
In this specification, Y l1in/Y Taax is 0
．． 9 or more is indicated by ◯, 0.7 to 0.9 is indicated by Δ, and 0.7 or less is indicated by X.

[Example-2] The product was manufactured in exactly the same manner as in Example-1 except that the surface roughness of the back layer was set to 1000.

[Example-3] The product was manufactured in exactly the same manner as in Example-1 except that the surface roughness of the back layer was set to 200.

[Comparative Example-1] An iron nitride thin film magnetic layer was formed on one surface of a support made of a polyethylene terephthalate film with a thickness of 12.5 μm and a width of 100 m using a continuous Vt vapor deposition device to a thickness of 1200 m without providing an undercoat layer. Formed by people. The conditions during smoke deposition were a support conveyance speed of 610 m/min and a high incidence excess θll1.
ax was 90'', and low incidence excess θIwin was 62''.

A protective film of stearic acid with a thickness of about 150 mm was provided on this magnetic layer. In addition, a sample similar to that of the example was prepared without providing a back layer.

[Comparative Example-2] The same undercoat layer as in the example was formed on the surface of a polyethylene terephthalate film having a thickness of 12.5 μm and a width of 100H. On top of this undercoat layer, Co
A Ni ferromagnetic thin film (containing 10% by weight of Ni and 1% of oxygen by weight) was deposited to a thickness of 1800 mm using an oblique evaporation method, and a back layer was provided to prepare a magnetic tape material, and samples were prepared in the same manner as in the examples.

[Comparative Example-3] It was manufactured in exactly the same manner as in Example-1 except that the surface roughness of the back layer was set to 100.

It was manufactured in exactly the same way except for the following.

The surface roughness of the backing layer in each of the above Examples and Comparative Examples was adjusted by appropriately changing the diameter of calcium carbonate particles contained in the backing layer.

The results of the above Examples and Comparative Examples are shown in Table-1.

As is clear from Table 1, in the examples according to the present invention, the magnetic flux was small and the running properties and head contact were also very good. Also, if the back layer surface roughness is small,
The increase in friction causes poor runnability (adverse effects begin to appear after about 2,000 people), and conversely, when the surface roughness of the back layer reaches the limit of 200 people or more, the back layer becomes imprinted on the plasma polymerized layer on the front side. It is presumed that the head area is likely to be defective because of this.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a magnetic tape that is an embodiment of the present invention. 1... Nonmagnetic support, 2... Undercoat layer, 2a...
Convex portion, 3... Iron nitride thin film magnetic layer, 4... Plasma polymerized layer, 4a... Protrusion, 5... Back layer. (3 others)

Claims (1)

[Claims] An undercoat layer capable of imparting protrusions to the surface of the outermost layer is provided on one side of the nonmagnetic support, and an iron nitride thin film magnetic layer and a plasma polymerized layer are sequentially laminated on the undercoat layer in this order. , the other surface of the non-magnetic support has a surface roughness of 200 to 200.
A magnetic recording medium provided with a 2000 Å back layer.