JPH07210861A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a metallic thin film magnetic recording medium excellent in travelling property, durability and preservability. CONSTITUTION:In a magnetic recording medium with a magnetic layer on at least one side of the nonmagnetic substrate, a lubricative layer contg. at least one of compds. represented by (CF3)2CF(CF2)a-(CH2)bCOO<->N<+>H3(CH2)cCH3 (general formula I) and (CF3)2CF(CF2)aCOO<-> N<+>H3(CH2cCH3 (general formula II) is formed on a ferromaqnetzc metallic thin film as the magnetic layer. In the formula I, 2<= a+b<=8, 0<=a<=8, 1'<=4 and 13<=c<=21. In the formula II, 2<=a<=8 and 13<=c<=21. The objective magnetic recording medium excellent in such characteristics as the coefft. of friction and still durability is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of running property, durability and storability of a ferromagnetic metal thin film type magnetic recording medium, and particularly lubrication of a magnetic layer formed of a ferromagnetic metal thin film by vapor deposition. And a magnetic recording medium having improved properties.

[0002]

2. Description of the Related Art A lubricant for a magnetic recording medium such as a magnetic tape or a floppy disk is applied to the surface of a magnetic layer to improve the lubricity and running durability between the magnetic recording medium and the head. ing. In particular, in the magnetic recording medium, due to the higher recording density, the magnetic layer surface becomes smoother, and the magnetic recording medium is used in various environments.
And the recorded information is stored for years to decades. Therefore, running durability and storage stability under various environments are required, and conventional lubricants cannot exhibit sufficient effects. Further, a camcorder, that is, a video tape recorder with a built-in camera and a small video tape recorder are often used externally, and a magnetic recording medium is required to have a lubricating performance that can be used under a wide range of environmental conditions. Further, the metal thin film type magnetic layer is advantageous for high density recording, and a thin film metal type is expected for future high definition and digitalization for improving magnetic recording density.
Since the metal of the recording layer is protected only by a very thin oxide layer, there is a demand for a thin film metal type magnetic recording medium to provide a lubricant capable of greatly improving the storability.

In a so-called metal thin film type magnetic recording medium having a ferromagnetic thin film formed on a non-magnetic support, which is expected as a magnetic recording medium for high density recording, which is excellent in electromagnetic conversion characteristics, an organic fluorine compound is lubricated. It is known that it is effective to use it as an agent, and various compounds are used in combination with these compounds. For example, Japanese Patent Laid-Open No. 64-3
In Japanese Patent No. 3719, RCOO ⁻ N ⁺ H (Rf) ₃ which is a salt of an amine in which one of the alkyl groups is a perfluoroalkyl group having 3 or more carbon atoms and a fatty acid containing a hydrocarbon is disclosed.
(However, R is a hydrocarbon and Rf is a perfluoroalkyl group) is described, but it is insufficient in terms of still durability and the like. Also, JP-A-64-3
In Japanese Patent No. 5722, R is a compound with an amine in which a fatty acid is a perfluoroalkyl group having 3 or more carbon atoms, and one or more of the alkyl groups is a fluorinated alkyl group.
Although a magnetic recording medium having fCOO ⁻ N ⁺ (R) ₄ (R is a fluorinated alkyl group or a perfluoroalkyl group) formed therein is described, it has insufficient still durability and storability and is a hydrocarbon. It was insoluble in the system solvent. Further, in JP-A-2-139715, C _n F _{2n + 1} (C is a compound of a fatty acid composed of a hydrocarbon substituted with a perfluoroalkyl group and an amine having a hydrocarbon group.
_{^{H 2) m COO - H 3}} N + R ( however, m is 2 or more, R represents but a hydrocarbon) is described, still durability was insufficient in terms of the friction coefficient.

In Japanese Patent Laid-Open No. 271013/1992, Rf (C) is a compound of a fatty acid composed of a hydrocarbon substituted with a perfluoroalkyl group and an amine having a hydrocarbon group.
^{_{H 2) n COO - H 3}} N + R (Rf is a perfluoroalkyl radical, R is described hydrocarbon) is, C ₈ F ₁₇ Specific compound ^{_{(CH 2) 9 COO - H}} 3 N + C ₁₈ H ₃₇ (heptadecafluoro octadecanoic acid octadecylamine salt)
Compounds in which the perfluoroalkyl group is linear are described, but the friction coefficient and the still durability after storage are not sufficient.

In Japanese Patent Laid-Open No. 4-274017, Rf
^{_{(CH 2) n N + H}} 3 - OOCRf (Rf is a perfluoroalkyl group) compound of fatty acid and amine represented by have been described, the friction coefficient was insufficient in terms of still durability. In Japanese Patent Laid-Open No. 4-274018, Rf (CH
₂ ) A compound of a fatty acid and an amine represented by _n N ⁺ H ₃ R ^— OOCR (Rf is a perfluoroalkyl group, R is a hydrocarbon) is described, but it is insufficient in terms of friction coefficient and still durability. there were. ^{_{Furthermore, C 7 F 15 COO - H}} 3 N + C 18 H 37
It is possible to use the above as a lubricant for hard disk discs. Mag. Soc. Japan, 13 , 213
(1989), the improvement in characteristics required for video tapes and the like was insufficient.

Further, carboxylic acid amine salt type C ₉ F ₁₉ C
The use of OO ^- H ₃ N ⁺ C ₁₈ H ₃₇ as a lubricant for vapor-deposited tape is the fourth paper of the Tribology Conference of the Japan Society of Lubrication.
Although it is described on page 79 (1992-5), the effect of reducing the friction coefficient was insufficient. Further, in Japanese Patent Application Laid-Open No. 5-2737, RfCOO ⁻ N ⁺ R ¹ R ² R ³ R ⁴ is disclosed.
(Rf is a perfluoropolyether group, R ^{1 to} R ⁴ are hydrocarbons), but in JP-A-4-370520, RhC
OO ⁻ N ⁺ (R) ₄ (Rh is a C _{10 to} C ₃₀ hydrocarbon)
Japanese Patent Laid-Open No. 4-372716 discloses RhPO ₃ {N
(R) ₄ } _n H _2-n (Rh is a C _{10 to} C ₃₀ hydrocarbon)
The JP 64-49118, JP-carboxylic acid amine salt composed of hydrocarbons, in JP-A-62-202326, RCOO ^- salts of heterocycles (R is C ₈ or higher alkyl groups) is JP-A-62-89220, RN ⁺
Although a lubricant for the back coat layer, which is a salt of a heterocyclic ring of H ₃ (R is an alkyl group having a C ₈ or more), is described, all of them are insufficient in terms of lubricating properties.

[0007]

DISCLOSURE OF THE INVENTION The present invention is directed to a high density magnetic recording medium, and in particular to vapor deposition for dramatically improving the recording density,
It is intended to provide a magnetic recording medium which is provided with runnability, durability and storability to a magnetic recording medium formed of a ferromagnetic metal thin film formed by a method such as sputtering.

Another object of the present invention is to provide a magnetic recording medium for a camcorder, which has sufficient running property and durability even when used outdoors. Another object of the present invention is to provide a magnetic recording medium having sufficient running property and durability even under various temperature and humidity environments. It is another object of the present invention to provide a method for producing a magnetic recording medium which is soluble in a hydrocarbon organic solvent and does not cause environmental problems due to the use of a fluorine organic solvent.

[0009]

The present invention is a magnetic recording medium having a ferromagnetic metal thin film on at least one surface of a non-magnetic support, and the following general formula (1) or A magnetic recording medium having a lubricating layer containing at least one of the compounds represented by formula (2). _{(CF 3) 2 CF (CF} 2) a (CH 2) b COO - N + H
₃ (CH ₂ ) _C CH ₃ (1) where 2 ≦ a + b ≦ 8, 0 ≦ a ≦ 8, 1 ≦ b ≦ 4, 1
3 ≦ c ≦ 21 (CF ₃ ) ₂ CF (CF ₂ ) _a COO ⁻ N ⁺ H ₃ (CH ₂ ) _C C
H ₃ (2) However, 2 ≦ a ≦ 8, 13 ≦ c ≦ 21 Further, the lubricating layer is a magnetic recording medium formed on a carbon film on a ferromagnetic metal thin film. A lubricating layer is a magnetic recording medium formed by coating a reaction product of a carboxylic acid component and an amine component. The lubricating layer is a magnetic recording medium formed by applying a carboxylic acid component and then an amine component, or by applying an amine component and then a carboxylic acid component.

The present invention is particularly effective when the magnetic recording medium of the present invention is a metal thin film type magnetic recording medium in which the magnetic layer is a so-called ferromagnetic metal thin film formed by a vacuum film forming method such as vapor deposition or sputtering. Is. That is,
By forming the lubrication layer represented by the general formula (1) or (2), the metal thin film magnetic recording medium having excellent electromagnetic conversion characteristics has practically excellent durability, running property, corrosion resistance and the like. The problem of (1) is remarkably improved.

In the magnetic recording medium of the present invention, in the above general formula (1) or (2), 2 ≦ a + b ≦
8, 0 ≦ a ≦ 8, 13 ≦ c ≦ 21, preferably 4 ≦ a + b ≦ 6, 2 ≦ a ≦ 6, 15 ≦ c ≦ 19,
If a + b is larger or smaller than this, a sufficient friction reducing effect is not exhibited. Whether a is larger or smaller than this does not show a sufficient friction reducing effect, and particularly when a is larger than 8, the solubility is poor and it becomes difficult to form a uniform protective film. When b is greater than 4, it is relatively a
However, when b exceeds 4, the chain length of the branched perfluoro and the alkyl group becomes short, and the effect of reducing the friction coefficient decreases. b does not have to be 0, that is, a hydrocarbon group adjacent to the alkyl fluorine chain, but it is effective in increasing the solubility and also has an effect of preventing corrosion. Therefore, b is 1 or more, that is, such a carbon group. It is preferable to have a hydrogen group. Therefore, from the viewpoint of solubility in ordinary organic solvents, that is, non-fluorine-based solvents, (1) is preferable to (2) above. Further, if c is larger or smaller than this, a sufficient effect of reducing the friction coefficient is not exhibited, and if it is particularly large, the solubility of the amine salt becomes poor and the still durability becomes insufficient. As the carboxylic acid group as described above, (CF ₃ ) ₂ CF (CH ₂ ) ₄ CO having a fluoroalkyl group composed of a branched carbon chain is used.
_{O, (CF 3) 2 CFCF} 2 (CH 2) 2 COO, (CF 3)
_{2 CF (CF 2) 2 (} CH 2) 2 COO, (CF 3) 2 CF
(CF ₂ ) ₄ (CH ₂ ) ₂ COO and the like, and amines include CH ₃ (CH ₂ ) ₁₃ NH ₂ and CH ₃ (CH ₂ ) ₁₅ N.
H ₂ , CH ₃ (CH ₂ ) ₁₇ NH ₂ , CH ₃ (CH ₂ ) ₁₉ NH ₂
Etc. The carbon chain of the amine is preferably longer than the carbon chain of the carboxylic acid, and specific compounds include (CF ₃ ) ₂ CF (CH ₂ ) ₄ COO ^- H ₃ N ⁺ (C
H ₂ ) ₁₃ CH ₃ , (CF ₃ ) ₂ CF (CH ₂ ) ₄ COO ^- H ₃ N
⁺ (CH ₂ ) ₁₇ CH ₃ , (CF ₃ ) ₂ CF (CF ₂ ) ₄ (C
^{_{H 2) 2 COO - H 3}} N + (CH 2) 13 CH 3, (CF 3) 2 C
F (CF ₂ ) ₄ (CH ₂ ) ₂ COO ^- H ₃ N ⁺ (CH ₂ ) ₁₇ CH
_{3, (CF 3) 2 CF} (CF 2) 4 (CH 2) 2 COO - H 3 N +
(CH ₂ ) ₁₉ CH ₃ , (CF ₃ ) ₂ CF (CF ₂ ) ₆ (C
^{_{H 2) 2 COO - H 3}} N + (CH 2) 17 CH 3, (CF 3) 2 C
_{F (CF 2) 6 (CH} 2) 2 COO - H 3 N + (CH 2) 19 CH
_{3, (CF 3) 2 CF} (CF 2) 4 (CH 2) 2 COO - H 3 N +
(CH ₂ ) ₁₃ CH _{3 and the} like can be mentioned, and these may be used as a mixture. Further, in the magnetic recording medium of the present invention, the coating amount of the compound of the fatty acid having the branched perfluoroalkyl group and the amine having the long chain hydrocarbon group is preferably 1.0 to 50 mg / m ^2. If the amount is less than the above range, the effect cannot be obtained. If the amount is more than the above range, the vehicle may stop running. Moreover, the coating amount is 3 to 30.
More preferably, it is mg / m ² . Acetone, methyl ethyl ketone, methyl isobutyl ketone,
It can be coated on the magnetic layer or the carbon film formed on the magnetic layer by a usual coating method such as a coil bar using cyclohexanone, methanol, ethanol, isopropanol or the like as a solvent.

Further, by providing a back coat layer composed of a coating film mainly composed of non-magnetic powder and a binder resin on the surface of the non-magnetic support opposite to the surface on which the magnetic layer is formed, the magnetic recording according to the present invention. The running property and durability of the medium can be further improved. In the case of a ferromagnetic metal thin film, the amount of lubricant that can be retained on the surface or inside is small, so by adding a lubricant in the backcoat layer in advance, the insufficient lubricant can be removed from the backcoat layer side. Is advantageous because it can be supplied from That is, the lubricant is replenished to the magnetic layer by bringing the backcoat layer and the magnetic layer into contact with each other while the tape-shaped magnetic recording medium is wound. As the non-magnetic powder of the back coat layer,
Various inorganic pigments and carbon black can be used, and various binder resins such as nitrocellulose, vinyl chloride resin, polyurethane and other binder resins used for coating type magnetic layers can be used. can do.

Further, a carbon film having a graphite structure or a diamond-like structure is formed on the surface of the magnetic layer, and carbon such as alkanes such as methane, ethane, propane and butane, alkenes such as ethylene and propylene, and alkynes such as acetylene. After forming by plasma CVD, sputtering, etc. using the contained compound as a raw material,
By imparting the above-mentioned phosphate compound, particularly in the case of a metal thin film type magnetic recording medium, its durability can be effectively improved. The nonmagnetic support in the magnetic recording medium of the present invention has a thickness of 5 to 15 μm.
Polyethylene terephthalate, polyethylene naphthalate, polyamide, polyimide and the like. Also,
The magnetic layer of the magnetic recording medium of the present invention is preferably a ferromagnetic metal thin film made of a metal such as iron, nickel or cobalt, or an alloy thereof, and has a magnetic layer thickness of 0.1 to 0.3 μm.
It is preferably m. The magnetic layer is particularly preferably a single layer containing 90 atomic% or more of cobalt and containing nickel, chromium, etc., a parallel type multilayer, and a non-parallel type multilayer, and the magnetic layer forming means is a means such as vapor deposition or sputtering. Can be applied, but a magnetic layer formed by a vapor deposition method in the presence of oxygen is particularly preferable. Further, on the magnetic layer comprising the ferromagnetic metal thin film of the present invention, carbon-containing compounds such as alkanes such as methane, ethane, propane and butane, alkenes such as ethylene and propylene, or alkynes such as acetylene are used as raw materials. After forming the carbon film by the plasma CVD described above, the compound of the present invention can be applied by coating or the like. In addition, the magnetic recording medium of the present invention contains a rust preventive agent composed of a tetrazaindene ring compound and / or a thiouracil ring compound, a benzotriazole compound, and a thiobenzimidazole compound, thereby improving the properties as a magnetic recording medium. Can be increased. Examples of the tetrazaindene ring compound that can be used for such a purpose include those shown below.

[0014]

[Chemical 1]

Here, R is a hydrocarbon group selected from an alkyl group, an alkoxy group and an alkylamido group.
Particularly preferably, the number of carbon atoms is 3 or more and 26 or less, and in the case of alkoxy, R of ROCOCH ₂ — is C ₃ H.
_{7 -, C 6 H 13 -} , phenyl, also in the case of alkyl _{groups, C 6 H 13 -, C} 9 H 19 -, C 17 H 35 - , and the like,
In the case of alkylamide, R of RNHCOCH ₂ — includes phenyl and C ₃ H ₇ —. Further, examples of the thiouracil ring compound include those shown below.

[0016]

[Chemical 2]

Here, R is a hydrocarbon group having 3 or more carbon atoms. The lubricant and the rust preventive may be mixed and applied at the same time, but a method of applying the rust preventive first and then applying the lubricant is effective. The coating method can be applied by dissolving in an organic solvent and applying a usual coating method such as a coil bar,
Further, the rust preventive agent may be included in the back coat layer and transferred to the magnetic layer when the magnetic recording medium is wound up. The coating amount of the rust preventive agent is preferably 0.1 to 5.0 mg / m ² ,
Particularly preferably, the rust preventive agent is 0.3 to 3 mg / m ² . In order to improve running durability, it is effective to provide fine protrusions on the surface of the non-magnetic support before forming the ferromagnetic metal thin film, as a result of which appropriate irregularities are provided on the surface of the magnetic layer. is there. The existence density of the fine projections on the surface of the non-magnetic support is 2 × 10 ⁶ to 2 × 10 ⁸ , and the height of the projections is 1 to 5
It is preferably 0 nm.

[0018]

The present invention relates to a magnetic recording medium having a magnetic layer made of a ferromagnetic metal thin film on at least one surface of a non-magnetic support, in which a branch is formed on the surface of the magnetic layer or on the carbon film formed on the magnetic layer. A lubricant layer containing a carboxylic acid group having a fluoroalkyl group consisting of a carbon chain and a salt consisting of a long-chain aliphatic amine, in which the carbon chain of the amine is made longer than that of the carboxylic acid. It is a thing. Due to this, the length of the two molecular chains extending from the polar group adsorbed on the surface of the magnetic layer is different, and the still durability,
Both are excellent in terms of friction coefficient. The alkyl group on the carboxyl group side is preferable because it reduces the corrosiveness of the polar group. Furthermore, since the terminal of the perfluoroalkyl group is branched, the covering effect by the perfluoroalkyl group is enhanced and the still durability is improved. as a result,
A magnetic recording medium having an unprecedented friction coefficient and still characteristics can be obtained.

[0019]

EXAMPLES The present invention will be described in more detail below by showing Examples of the present invention. Examples and Comparative Examples (Lubricant Synthesis Method) Perfluoroalkyl iodide (RfI) and an acrylic acid ester compound (CH ₂ ═CHCOOR) having an unsaturated bond at the end are subjected to a radical reaction in the presence of azobisisobutyronitrile. Let RfCH ₂
RfCH ₂ CH ₂ COOH was synthesized by making CHICOOR and then hydrolyzing the ester bond. (A method for producing such a compound is described in, for example, J. Org. Ch.
em. , 27 , 4491 (1962). ) Then, the obtained carboxylic acid having a perfluoroalkyl group was mixed with an amine compound and heated to obtain a desired lubricant.

(Production of magnetic recording medium) A 150 μm-thick magnetic layer made of cobalt-nickel was obliquely vapor-deposited on polyethylene terephthalate having a thickness of 7 μm. Evaporation is
A cobalt-nickel alloy (90% by weight cobalt, 10% by weight nickel) was evaporated by an electron beam, and an oxygen gas was introduced in a vacuum degree of 6.7 × 10 ^-3 N / m ² while being oblique at an incident angle of 50 degrees. Deposition was performed. Next, high-frequency power of 400 W was applied to methane as a raw material on the magnetic layer to generate plasma, and -40 was generated on the surface of the magnetic layer through a pass roller.
0 V is applied to the anode provided in the gas introduction part, and a DC bias voltage of +500 V is applied to accelerate the generated plasma to form a carbon film with a thickness of 8 nm on the surface of the magnetic layer. The surface treatment of the carbon film was performed by supplying a mixed gas of argon: oxygen = 95: 5 in ratio to generate plasma in the same manner.

Lubricants shown in Tables 1 and 2 were applied to the surface of the carbon film with a coil bar and dried, and then a backcoat layer coating solution having the following composition was applied to the surface opposite to the surface on which the magnetic layer was formed. Then, it was cut into a width of 8 mm to produce a magnetic tape. (Backcoat layer coating liquid) Carbon black (particle size 18 nm) 100 parts by weight Nitrocellulose (RS1 / 2H manufactured by Daicel) 60 parts by weight Polyurethane (N-2304 manufactured by Nippon Polyurethane Co., Ltd.) 60 parts by weight Polyisocyanate (manufactured by Nippon Polyurethane Co., Ltd.) Coronate L) 20 parts by weight Methyl ethyl ketone 1000 parts by weight Toluene 1000 parts by weight Next, the magnetic tapes produced were evaluated by the following methods, and the results are shown in Tables 1 and 2. The (ratio) described in the sample number indicates a comparative example. [Evaluation Method] Measurement of Friction Coefficient A magnetic tape and a stainless steel pole are brought into contact with each other at a winding angle of 180 ° with a tension (T ₁ ) of 50 g, and a tension required for running the magnetic tape at a speed of 3.3 cm / sec. (T ₂ ) was measured. Repeat 100 times, 100
The friction coefficient μ for the second time was calculated by the following calculation formula. μ = 1 / π · ln (T ₂ / T ₁ ) The friction coefficient μ was measured at 23 ° C. and 70% RH.

Still-durability measurement Still-durability was measured by using an 8mm VTR (Hi8 FH125SW manufactured by Fuji Photo Film Co., Ltd.) without operating the still limit mechanism, and playing back a self-recorded image in a still state and outputting the output. Was evaluated by measuring the time until it became −3 dB with respect to the initial output. Still durability is
A) As is (before storage) and B) 60 ° C 90%
What was stored in the RH environment for 7 days (after storage) was 5 ° C 1
It was measured at 0% RH.

Evaluation of storability VTR of the same model as used for evaluation of still durability
Is used to measure the reproduction output of a magnetic tape stored in an environment of 60 ° C and 90% RH for 7 days, and the output before storage is 0 dB.
Was evaluated as.

Evaluation of output reduction VTR of the same model as used for evaluation of still durability
The signal of 7 MHz was recorded by using and was reproduced 100 times at 23 ° C. and 10% RH. With the initial reproduction output of reproduction 1 pass set to 0 dB, the output after 100 passes reproduction was measured and shown in the table as an output change.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

[0028]

Industrial Applicability A high density magnetic recording medium capable of obtaining a protective layer technology having high storability, runnability and durability, which has not been obtained by a conventionally known lubricant, and is sufficiently compatible with an outdoor environment. Was realized. This is a long-chain fat having a carboxylic acid group having a fluoroalkyl group consisting of a branched carbon chain and an alkyl group longer than the carbon chain of fluoroalkyl on the surface of the magnetic layer or on the carbon film formed on the magnetic layer. A lubricating layer containing a salt consisting of a group amine is formed. Due to this, the lengths of two molecular chains extending from the polar groups adsorbed on the surface of the magnetic layer are different, so that the still durability and friction coefficient are improved. Both become excellent, especially,
Since the terminal of the perfluoroalkyl group is branched, the covering effect by the perfluoroalkyl group is enhanced and the still durability is improved. As a result, a magnetic recording medium having an unprecedented coefficient of friction and still characteristics can be obtained.

Claims (4)

[Claims] 1. In a magnetic recording medium having a ferromagnetic metal thin film on at least one surface of a non-magnetic support, the following general formula (1) or general formula (2) is provided on the ferromagnetic metal thin film.
A magnetic recording medium having a lubricating layer containing at least one of the compounds represented by. _{(CF 3) 2 CF (CF} 2) a (CH 2) b COO - N + H
₃ (CH ₂ ) _C CH ₃ (1) where 2 ≦ a + b ≦ 8, 0 ≦ a ≦ 8, 1 ≦ b ≦ 4, 1
3 ≦ c ≦ 21 (CF ₃ ) ₂ CF (CF ₂ ) _a COO ⁻ N ⁺ H ₃ (CH ₂ ) _C C
H ₃ (2) where 2 ≦ a ≦ 8, 13 ≦ c ≦ 21 2. The magnetic recording medium according to claim 1, wherein the lubricating layer is formed on the carbon film on the ferromagnetic metal thin film. 3. The magnetic recording medium according to claim 1, wherein the lubricating layer is formed by coating a reaction product of a carboxylic acid component and an amine component. 4. The lubricating layer is formed by applying a carboxylic acid component and then an amine component, or is formed by applying an amine component and then a carboxylic acid component. Item 1. A magnetic recording medium according to items 1 and 2.