JPH04222922A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To improve traveling property of a VTR and still durability by forming a diamond-like carbon film, plasma polymn. film containing metal, and lubricant layer to constitute a protective film for a magnetic film. CONSTITUTION:On a nonmagnetic substrate 5 comprising polyethylene terephthalate, etc., there are formed a magnetic metal thin film 4, diamond-like carbon film 3, plasma polymn. film 2 containing metal, and lubricant layer 1. The back surface of the substrate 5 is coated with a back coating layer 6. The layer 1 essentially consists of fluorine-contg. carboxylic acid and has 30-50Angstrom thickness. The optimum thickness of the film 2 is 5-30Angstrom . This layer assists orientation of the lubricant. The optimum thickness of the film 3 is 100-200Angstrom , and the film 3 with the layer 1 prevent damages in the magnetic tape.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium whose magnetic recording layer is a ferromagnetic metal thin film used in digital video tape recorders and high-definition video tape recorders, and a method for manufacturing the same.

0002

2. Description of the Related Art Attempts have been made to improve the corrosion resistance, still durability, and running durability of magnetic recording media whose magnetic recording layer is a ferromagnetic metal thin film using various methods. For example, a method of providing a carboxylic acid-based or phosphoric acid-based lubricant on a ferromagnetic metal thin film, a method of providing a protective film of a non-magnetic metal on a ferromagnetic metal thin film, or a method of providing a protective film of an oxide such as silica. There is a way to set it up.

[0003]More recently, Japanese Patent Application Laid-Open No. 14252/1983
No. 5, JP-A No. 61-208622, a carbon-based protective film is provided, or JP-A No. 62-21931,
A diamond-like carbon film is used as a protective film as in Publication No. 4 and Japanese Unexamined Patent Publication No. 61-210518. Also,
There is also an example of using a diamond-like carbon film and a plasma polymerized film as a protective film, as in JP-A-2-137116. When a diamond-like carbon film is used as a protective film for a ferromagnetic thin film, the still durability and running durability are significantly improved, but because the diamond-like carbon film is inert, the orientation of the lubricant is poor and water repellency is low. As a result, running performance deteriorated in high-temperature, high-humidity environments, and jitter was more likely to occur. Therefore,
It was considered that a diamond-like carbon film and a plasma polymerized film were used as a protective film, and that the plasma polymerized film had water repellency, but in this case, the lubricant did not react with the polymerized film, so most of the lubricant was transferred to the back coat side. The durability was reduced due to lack of lubricant.

0004

[Problem to be solved by the invention] Even if a diamond-like carbon film is used, which significantly improves the still durability and running durability of ferromagnetic metal thin film magnetic recording media, jitter occurs due to deterioration of running properties in high temperature and high humidity environments. The purpose of this invention is to provide a thin-film magnetic recording medium that does not generate.

[0005]

[Means for solving the problem] In order to achieve this object, a plasma polymerized film containing a metal that easily reacts with a carboxylic acid-based lubricant is provided on a diamond-like carbon film.
The structure is such that the lubricant does not easily move from the plasma polymerized film and the lubricant is sufficiently oriented.

Furthermore, in order to maintain the high orientation ability of the carboxylic acid lubricant, the carboxylic acid lubricant is applied immediately after the formation of the plasma polymerized film containing metal without taking out the magnetic recording medium from a vacuum using an organic vapor deposition method. A manufacturing method that provides

[0007]

[Action] Metals in the plasma polymerized film, such as Pb and Sn
, Cd, Fe, etc. and the carboxyl group of the fluorine-containing carboxylic acid, the structure is such that the carboxyl group of the carboxylic acid is arranged on the plasma polymerization side and the hydrophobic groups are arranged outward. As a result, the water-repellent property of the magnetic surface side of the magnetic tape is sufficiently ensured, and carboxylic acid does not migrate to the back coat side even in a high temperature and high humidity environment.

The advantage of the present invention is that there is no occurrence of jitter due to poor running in a high-temperature, high-humidity environment, and there is no decrease in still durability or running durability after long-term storage.

A feature of the manufacturing method is that three steps related to the protective film are performed at once in one vacuum chamber. It prevents water and oxygen from the atmosphere from adhering to the plasma polymerized film containing metal, and improves the ability of carboxylic acid to align with metal.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic cross-sectional view of a metal thin film type magnetic tape, and its structure will be explained.

In FIG. 1, 1 is a lubricant layer mainly composed of fluorine-containing carboxylic acid, and has a thickness of 30 Å to 50 Å. The fluorine-containing carboxylic acid may be used alone or in combination with a fluorine-containing carboxylic acid ester. For example, C
5F11(CH2)10COOH and C5F11(CH2
)10COOC8H17 is mentioned.

2 is a plasma polymerized film containing metal;
The optimal thickness is 5 Å to 30 Å. This is formed by a plasma discharge within the discharge tube. This layer helps orient the lubricant.

No. 3 is a diamond-like carbon film, which has a high Vickers hardness of about 3000 and prevents damage to the magnetic tape together with the lubricant. Thickness is 100 Å to 200 Å
is the best balance between reliability and output.

4 is a ferromagnetic metal thin film, which is made of C
o-Ni-O, Co-O, Co-Cr, etc. can be used. Its thickness is generally from 500 Å to 3000 Å.

5 is a non-magnetic substrate made of polyethylene terephthalate, polyethylene naphthalate, polyamide,
Possible materials include films such as polyimide, aluminum substrates, and glass substrates. The surface of the magnetic side of the substrate is 100 Å to 300 Å.
The one with the protrusion forming process of Å is the best for achieving both reliability and output.

6 is a back coat layer, which is made of polyurethane, nitrocellulose, polyester, carbon,
Contains calcium carbonate, etc. The thickness is 5000 Å. (FIG. 2) is an example of the magnetic recording medium manufacturing apparatus of the present invention.

In FIG. 2, 7 is a vacuum chamber, which is controlled at 10-4 Torr to 10-3 Torr. This is managed by exhausting air from the exhaust port 13 with a pump.

Reference numeral 8 denotes a discharge tube for producing a diamond-like carbon film, and alternating current and direct current are applied to the electrodes. The gases used are hydrocarbons and inert gases such as argon.

Reference numeral 9 denotes a discharge tube for forming a plasma polymerized film containing a metal, which is the key to the present invention, and an alternating current is applied to the electrode, and the film is formed using an organometallic gas.

Reference numeral 10 denotes a nozzle for organic vapor deposition for forming a lubricant layer, and a resistance heater therein, and a lubricant introduced into a resistance heater 11 to evaporate the lubricant.

Reference numeral 12 denotes a cooling can along which the back coat layer of the metal thin film magnetic tape runs.

[0022] A detailed explanation including manufacturing conditions will be given below. 5
ST on the 00mm wide polyethylene terephthalate surface.
One protrusion with a height of 300 Å and a diameter of 2000 Å was determined by M analysis.
While introducing oxygen by oblique vacuum evaporation onto the non-magnetic substrate 5 on which 105 to 109 pieces per mm2 are formed, carbon is applied.
A ferromagnetic metal thin film 4 made of o(80)-Ni(20) is formed to a thickness of 1800 Å. After that, a methyl ethyl ketone/toluene/anone solution with a solid content of 30% consisting of polyurethane, nitrocellulose, and carbon black was applied using a reverse roll coater after drying.
The coating is applied so that the thickness is 5000 Å.

Argon gas and hexane gas are mixed at a ratio of 1:4 on this ferromagnetic metal thin film 4, and while maintaining the total gas pressure at 0.3 Torr, a frequency of 20 KHz and a voltage of 150
A diamond-like carbon film 3 having a thickness of 150 Å is formed by applying 0 V alternating current and 1000 V direct current to the electrodes in the discharge tube 8 by plasma CVD.

Next, tetramethyltin, tetraoctyltin, and dibutyldimethoxytin were introduced under reduced pressure as organic metal gases into the discharge tube No. 9, and the electrodes were heated at 20 KHz and 5 kHz.
Plasma polymerized film 2 containing metal by applying 00V alternating current
is provided with a thickness of 1 Å to 50 Å. Samples in which plasma polymerized films of 2 Å, 8 Å, 14 Å, 30 Å, 40 Å, and 50 Å thick were provided using tetramethyltin are referred to as samples 1, 2, 3, 4, 5, and 6, respectively. Samples with plasma polymerized films of 5 Å, 25 Å, and 40 Å thick using tetraoctyltin as a raw material are referred to as samples 7, 8, and 9, respectively. Furthermore, using dibutyldimethoxytin as a raw material, 1 Å
, 10 Å, and 20 Å thick plasma polymerized films are referred to as samples 10, 11, and 12. Samples 13 and 14 are samples in which plasma polymerized films with thicknesses of 30 Å and 40 Å are provided using ferrocene as a raw material. Samples 15 and 1 have plasma polymerized films of 10 Å and 35 Å thick using cyclohexane cadmium butyrate as a raw material.
Set it to 6. As a comparative example, Sample 17 was prepared using the same sample without the metal-containing plasma polymerized film 2.
, 18. A fluorine-containing carboxylic acid, C5F11 (C
H2) A lubricant layer 1 was formed by forming 50 Å of 10COOH by an organic vapor deposition method.

These samples 1 to 18 were cut into 8 mm width pieces using a slitter to prepare magnetic tapes. Using the experimentally produced magnetic tape samples 1 to 8, the coefficient of dynamic friction was first measured in an environment of 40° C.-80%. The measurement was carried out using a friction coefficient measuring machine, the post material was SUS420J2, the diameter was 4 mm, the surface roughness was 0.2 s, the load was 30 gf, and the tape speed was 0.5 mm.
The test was carried out under the conditions of /s. The results are shown in Table 1 for each sample. Table 1 also shows the jitter level in a VTR deck in a 40°C-80% environment, which is thought to be related to this coefficient of dynamic friction.

[0026] Furthermore, these samples were heated at 40°C-90°C.
The cassette was left in an environment of 100% for one month, then taken out again and its still life was measured using an 8mm VTR. The environment was 23°C - 70% and the actual machine tension was used. The life was determined when the output decreased by 3 dB compared to the initial state, and the time up to that point was expressed in minutes. The results also (Table 1)
It was shown to.

[0027]

[Table 1]

Samples 2, 3, and 4 in which the thickness of the metal-containing plasma-polymerized film was controlled from 5 Å to 30 Å (Table 1)
, 7, 8, 11, 12, 13, 14, and 15 have lower friction coefficients at 40° C.-80% than the comparative examples, and no jitter occurs in the VTR. Furthermore, still durability has been improved after long-term storage in high-temperature, high-humidity environments.

However, the plasma polymerized film containing metal is
Below Å, as shown in Samples 1 and 10, the friction coefficient is insufficiently lowered and jitter is likely to occur. On the other hand, sample 5 in which the thickness of the plasma polymerized film containing metal was 30 Å or more,
The runnability and jitter in high-temperature, high-humidity environments of Nos. 6, 9, and 16 are similarly improved, but the still durability after being left in a high-temperature, high-humidity environment is reduced. Although the reason for this is not clear, it is thought that the thick plasma-polymerized film containing metal has stronger metallic properties, making it easier to adhere to the head.

[0030]

As described above, the present invention provides a lubricant containing fluorine atoms by providing a plasma polymerized film containing metal on a diamond-like carbon film with a thickness of 5 Å to 30 Å immediately after forming the diamond-like carbon film. This improves the orientation of the carboxylic acid agent, which improves the running properties of magnetic tapes and the jitter characteristics of VTRs, and also improves the still durability after being left at high temperatures and high humidity.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a metal thin film magnetic tape according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a protective film forming apparatus according to an embodiment of the present invention.

[Explanation of symbols]

1 Lubricant layer 2 Plasma polymerized film containing metal 3 Diamond-like carbon film 4 Ferromagnetic metal thin film 5 Polyethylene terephthalate 6 Back coat 7 Vacuum chamber 8 Discharge tube for diamond-like carbon film 9 Discharge tube for plasma polymerized film 10 Nozzle for organic vapor deposition 11 Resistance heater 12 Can 13　Exhaust port

Claims (3)

[Claims] 1. A metal thin film magnetic recording medium in which a ferromagnetic metal thin film is provided on one surface of a nonmagnetic substrate, wherein the protective film of the magnetic thin film is composed of a diamond-like carbon film, a plasma polymerized film containing metal, and a lubricant. A metal thin film magnetic recording medium characterized by: [Claim 2] The thickness of the plasma polymerized film containing metal is 5
2. The metal thin film magnetic recording medium according to claim 1, wherein the thickness is from Å to 30 Å. 3. A method for manufacturing a protective film, which comprises successively forming a diamond-like carbon film as a protective film and a plasma polymerized film containing metal by a plasma CVD method, and a lubricant layer by an organic vapor deposition method.