JP2666430B2 - Magnetic recording media - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium such as a magnetic tape, a magnetic disk, etc. The present invention relates to a magnetic recording medium that retains as a lubricant.

[Summary of the Invention]

The present invention provides a magnetic recording medium having a magnetic layer on one surface of a non-magnetic support, wherein the magnetic layer comprises a long-chain fluorinated ammonium carboxylate or a long-chain fluorinated amine carboxylate as a lubricant. It is intended to improve the running property and durability of the magnetic recording medium by internally adding or coating.

[Conventional technology]

Conventionally, in the field of magnetic recording, γ-Fe containing γ-Fe ₂ O ₃ , Co on a non-magnetic support such as a polyester film or polyethylene terephthalate (PET) film.
_{2 O 3, Fe 3 O 4} , Fe 3 O 4 containing Co, γ-Fe ₂ O ₃ and Fe ₃ berthollide compound with O _4, a CrO _2, etc. oxide magnetic powder or Fe,
Applying and drying a magnetic paint in which a powder magnetic material such as an alloy magnetic powder containing Co, Ni, etc. as a main component is dispersed in an organic binder such as a vinyl chloride-vinyl acetate copolymer, a polyester resin, and a polyurethane resin. A so-called coating type magnetic recording medium prepared by the above-mentioned method is widely used.

On the other hand, as the demand for high-density magnetic recording has increased, magnetic materials made of metal or alloys such as Co-Ni alloys have been used in plating and vacuum thin film forming technologies (vacuum evaporation, sputtering, ion plating, etc.). ), A so-called metal thin film type magnetic recording medium in which a metal magnetic thin film is formed directly on a non-magnetic support has been proposed and attracts attention. This metal thin film type magnetic recording medium is excellent in coercive force, squareness ratio, electromagnetic conversion characteristics in a short wavelength range, etc.
The thickness of the magnetic layer can be made extremely thin so that recording demagnetization and thickness loss at the time of reproduction are extremely small, and since the magnetic layer does not contain a non-magnetic material such as a resin binder, the packing density of the magnetic material It has a number of advantages such as higher

Since these magnetic recording media are used while being in sliding contact with the magnetic head, the surface of the magnetic layer is formed sufficiently smooth from the viewpoint of maintaining excellent electromagnetic conversion characteristics and preventing obstacles such as dropouts. It is necessary that the contact property with the substrate be kept good. However, when the smoothness of the surface of the magnetic layer is extremely high, a substantial contact area with a sliding member such as a magnetic head or a guide roller becomes too large, and an adhesion phenomenon (so-called sticking) easily occurs. When such sticking occurs, the running property and the durability of the magnetic layer are rather reduced.

In order to solve this problem, use of various lubricants has been studied. Conventionally, higher fatty acids or esters thereof have been internally added to the magnetic layer of the magnetic recording medium, or the surface of the magnetic layer has to be added. Attempts have been made to reduce the coefficient of friction by coating the surface.

[Problems to be solved by the invention]

By the way, lubricants used for magnetic recording media include:
Especially at low temperatures so that the specified lubrication effect is ensured even when used in cold regions, it can be applied very thinly in consideration of the spacing between the magnetic head and the magnetic layer, and a sufficient lubrication effect is exhibited. Characteristics such as long-lasting lubrication effect.

However, various lubricating agents conventionally used harden under low temperature conditions, and the lubricating effect is reduced due to the fact that they are gradually removed by a magnetic head or the like over a long period of use. Was.

Therefore, the present invention has been proposed in view of such circumstances, and an object of the present invention is to provide a magnetic recording medium having excellent running properties and durability.

[Means for solving the problem]

As a result of repeated studies to achieve the above object, the present inventors have found that long-chain fluorinated ammonium carboxylate or long-chain fluorinated amine carboxylate exhibits a good lubricating effect over a wide temperature range and for a long period of time. It has been found that the present invention has been made.

 That is, the magnetic recording medium according to the present invention has a non-magnetic support.
Magnet consisting of a magnetic layer formed on at least one surface of the body
A recording medium, wherein the magnetic layer has a general formula C_nF_{2n + 1}(CH_Two)_mCOO N H_ThreeR (where n is a natural number, m is an integer of 2 or more, and R is water
Atom, unsubstituted hydrocarbon group, substituent-modified hydrocarbon group
Indicates one or the other. ) Fluorinated long-chain carboxyl
Acid ammonium salt or fluorinated long-chain carboxylic acid amine
It is characterized by retaining salt.

The ammonium salt of a fluorinated long-chain carboxylic acid or the amine salt of a fluorinated long-chain carboxylic acid used in the present invention has a negatively charged portion having a perfluoroalkyl group, a polymethylene group,
And a carboxyl group. This molecular ion is derived from a fluorinated long-chain carboxylic acid and can be synthesized, for example, by the following route.

By recrystallizing the fluorinated long-chain carboxylic acid thus synthesized together with ammonia or a primary amine from a suitable organic solvent, a fluorinated long-chain carboxylic acid ammonium salt or a fluorinated long-chain carboxylic acid amine salt is obtained. Obtainable.

Here, the carbon number n of the perfluoroalkyl group is a natural number. Although the range of carbon number n is not particularly limited, it is preferably 3 to 10. If it is less than 3, a sufficient lubricating effect does not appear, and if it is more than 10, there is a problem in handling such as solidification is likely to occur, and there is a possibility that lubricity may not be exhibited. Therefore, it may be set appropriately as long as practicality is not impaired.

The carbon number m of the polymethylene group is an integer of 2 or more. This is clear from the above-mentioned reaction pathway, and the synthesis of a fluorinated long-chain carboxylic acid involves the addition reaction of perfluoroalkyl iodide ( 1 ) to the terminal double bond of unsaturated carboxylic acid methyl ester ( 2 ). This is because m = 2 even when the lowest molecular weight methyl acrylate is used as this type of unsaturated carboxylic acid methyl ester. The larger the value of m is, the higher the melting point when the fluorinated long-chain carboxylic acid ammonium salt or fluorinated long-chain carboxylic acid amine salt is finally formed. In particular, it is more preferably selected to 5 or more because it is advantageous in terms of heat resistance when annealing is performed in a hard disk manufacturing process. Further, the upper limit of the number m of carbon atoms is not particularly limited, and can be appropriately set within a range that does not impair practicality.

On the other hand, when the molecular ion constituting the positively charged portion is a primary amine ion, R may be a saturated hydrocarbon group or an unsaturated hydrocarbon group, and these may be halogen, hydroxyl group, amino group, Nitro group, cyano group, aromatic ring,
It may be substituted by at least one of heterocycles and the like. The number of carbon atoms of R is not particularly limited, but is preferably 10 or more in the case of a linear hydrocarbon group.

Here, as the magnetic recording medium to which the present invention is applied,
First, a so-called coating type magnetic recording medium in which a magnetic layer is formed by applying a magnetic coating obtained by dispersing and kneading a magnetic material together with a dispersant and other additives to the surface of a non-magnetic support,
And a so-called metal thin film type magnetic recording medium in which a magnetic layer is formed by applying a magnetic material directly on a nonmagnetic support by a vacuum thin film forming technique.

Magnetic materials used in these magnetic recording media,
As the binder and other additives, the nonmagnetic support, and the like, any of conventionally known materials can be used, and there is no particular limitation.

In the present invention, as a method of retaining a long-chain fluorinated ammonium carboxylate or a long-chain fluorinated amine carboxylate in the magnetic layer, there are a method of internally adding to the magnetic layer and a method of coating the surface of the magnetic layer. The former is applicable to coating type magnetic recording media, and the latter is applicable to both coating type and metal thin film type magnetic recording media.

When internally adding a fluorinated long-chain carboxylic acid ammonium salt or a fluorinated long-chain carboxylic acid amine salt to the magnetic layer,
It is added in the range of 0.2 to 20 parts by weight based on 100 parts by weight of the binder.

When coating a fluorinated long chain carboxylic acid ammonium salt or fluoride long chain carboxylic acid amine salt to the surface of the magnetic layer, the coating amount 0.5 to 100 mg / m ^2, more preferably between 1 to 20 mg / m ² I do. When coating,
These may be dissolved in an appropriate organic solvent to form a lubricant solution, which may be applied or sprayed, or a magnetic recording medium may be immersed in the lubricant solution.

The above-mentioned ammonium salt of a fluorinated long-chain carboxylic acid or amine salt of a fluorinated long-chain carboxylic acid may be used alone as a lubricant for a magnetic recording medium, or may be used in combination with a conventionally known lubricant. Alternatively, it can be used in combination with a perfluoroalkyl carboxylic acid ester, a carboxylic acid perfluoroalkyl ester, a perfluoroalkyl carboxylic acid perfluoroalkyl ester, or a derivative thereof.

The magnetic recording medium of the present invention may have a back coat layer provided on the surface of the non-magnetic support on which the magnetic layer is not formed. In this case, the above-mentioned fluorinated long-chain carboxylic acid ammonium salt or fluorinated long-chain carboxylic acid amine salt can be also added to the back coat layer by internal addition or coating.

[Action]

In general, perfluoroalkyl groups are known to have the effect of lowering the coefficient of friction.However, intermolecular interactions are generally small, and especially when coated, the film strength is insufficient and the lubricating effect is sustained. There was a disadvantage that it was difficult.

However, in the fluorinated long-chain carboxylic acid ammonium salt or fluorinated long-chain carboxylic acid amine salt used in the present invention, a polymethylene group, which is not bulky, is bonded to a perfluoroalkyl group to increase the chain length. The intermolecular interaction is enhanced. Therefore, when the magnetic layer is internally added or held by a coating, a sufficient lubricating effect is exhibited, and the strength of the coating film particularly when coated is increased. As a result, the running properties and durability of the magnetic recording medium are improved.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described based on experimental examples.

First, an example in which the present invention is applied to a coating type magnetic tape will be described.

Example 1 First, a magnetic coating composition was prepared according to the following composition.

Co-coated γ-Fe ₂ O ₃ 100 parts by weight Vinyl chloride-vinyl acetate copolymer [binder] (UCC, trade name VAGH) 10.5 parts by weight Polyurethane resin [binder] (Nihon Polyurethanes, trade name M-5033) 10.5 parts by weight Carbon black [antistatic agent] 5 parts by weight Lecithin [dispersant] 1 part by weight Methyl ethyl ketone [solvent] 150 parts by weight Methyl isobutyl ketone [solvent] 150 parts by weight 1.5 parts by weight of stearylamine heptadecafluorononadecanoate (lubricant 1) shown in Table 1 was added as a lubricant, and 2 parts were added by a ball mill.
After mixing for 4 hours, the mixture was filtered through a 3 μm filter, and 4 parts by weight of an isocyanate-based curing agent was added, followed by stirring for 30 minutes. This magnetic paint was applied on a PET film having a thickness of 14 μm so that the thickness after drying was 5 μm, subjected to a magnetic field orientation treatment, dried, and wound up. Further, the sample tape was cut into 1/2 inch width through a calendering process to prepare a sample tape.

Examples 2 to 6 Instead of the above-mentioned stearylamine heptadecafluorononadecanoate (lubricant 1) as a lubricant, a lubricant 2 to a lubricant 6 shown in Table 1 described below was added, respectively. A sample tape was prepared in the same manner as in Example 1.

Comparative Example 1 In this comparative example, a sample tape was prepared in the same manner as in Example 1 except that ammonium nonadecafluorocarboxylate (lubricant 7 in Table 1) was used as a lubricant. This compound differs from the lubricant used in the present invention in that the positively charged portion has no polymethylene group between the perfluoroalkyl group and the carboxyl group.

For each of the sample tapes prepared as described above, the coefficient of friction and sfix lip characteristics before and after aging were measured at 25 ° C, 60% relative humidity, or temperature.
It was measured under each condition of 40 ° C and 80% relative humidity. Table 2 shows the results. In addition, the evaluation of stick-slip was evaluated as ○ when it was good, and x when it was bad.

As is clear from this table, in each of the examples in which the fluorinated long-chain carboxylic acid amine salt was used as the lubricant, the friction coefficient was reduced and the stick-slip property was improved as compared with the comparative example.

Next, an example in which the present invention is applied to a metal thin-film type magnetic disk will be described.

Example 7 First, in order to form a non-magnetic metal underlayer, a 15 μm thick
Al-Mg alloy substrate with an nNi-P plating layer (1.5m thick
m, an outer diameter of 95 mm, and an inner diameter of 25 mm), and Bi was deposited on the plating layer by electron beam evaporation at a gas pressure of 1 × 10 ⁻⁵ Torr and a substrate temperature of 150 ° C. to a thickness of 200 °.

Next, a gas pressure of 1 is also applied on the nonmagnetic metal underlayer.
× 10 ^-5 Torr, substrate temperature 150 ° C
Was deposited to a thickness of 1000 mm to form a metal magnetic thin film, and a carbon protective film was formed on the metal magnetic thin film by a vacuum evaporation method. Finally, on the surface of the carbon protective film,
The amount of heptadecafluorononadecanoic acid stearylamine salt (lubricant 1) shown in Table 1 above as a lubricant was applied.
It was applied so as to be 5 mg / m ² to prepare a sample disk.

Examples 8 to 12 Except for adding the above-mentioned lubricants 2 to 6 shown in Table 1 in place of the above-mentioned stearylamine heptadecafluorononadecanoate (lubricant 1) as a lubricant, respectively. A sample disk was prepared in the same manner as in Example 7.

Comparative Example 2 In this comparative example, a sample disk was prepared in the same manner as in Example 7, except that ammonium nonadecafluorocarboxylate (lubricant 7 in Table 1) was used as a lubricant.

The contact start / stop (CSS) characteristics of each sample disk prepared as described above were measured. In other words, the contact start / stop was set to 2000 with the head load of the ferrite magnetic head set at 9.5 g.
After repeating 0 times, the static friction coefficient between each sample disk and the ferrite magnetic head was measured. Table 3 shows the results.

From Table 3, it can be seen that Examples 8 to 12 all achieved better CSS characteristics than Comparative Example 2. When comparing the examples, the values of the coefficient of friction in Examples 7, 8, 10, and 11 did not increase significantly from the values shown in Table 2, whereas the values in Examples 9 and 12 were different. The rate of increase is somewhat high. Based on this fact, the runnability and durability of the magnetic recording medium are better when the R portion of the primary amine ion is a long-chain hydrocarbon flag than a cyclic hydrocarbon group such as a phenyl group or a cyclohexyl group. It is understood that this is preferable from the viewpoint of improving

Further, an example in which the present invention is applied to a metal thin film type magnetic tape will be described.

Example 13 First, a 14 μm-thick PET film was coated with Co by oblique deposition.
Was deposited to form a ferromagnetic metal thin film having a thickness of 1000 mm.
Subsequently, as a lubricant, heptadecafluorononadecanoic acid stearylamine salt (lubricant 1) shown in Table 1 was applied onto the ferromagnetic metal thin film so that the application amount was 5 mg / m ^2, and a magnetic field was applied. After being subjected to an orientation treatment and a calender treatment, it was cut into 1/2 inch to prepare a sample tape.

Examples 14 to 18 In place of the above-mentioned stearylamine heptadecafluorononadecanoate (lubricant 1) as a lubricant, except that lubricants 2 to 6 shown in Table 1 were respectively added. A sample tape was prepared in the same manner as in Example 13.

Comparative Example 3 In this comparative example, a sample tape was prepared in the same manner as in Example 13, except that ammonium nonadecafluorocarboxylate (lubricant 7 in Table 1) was used as a lubricant.

Comparative Example 4 After forming a ferromagnetic metal thin film in the same manner as in Example 13, a sample tape was prepared without applying a lubricant.

The dynamic friction coefficient, still durability, and shuttle durability of each of the sample tapes prepared as described above were measured under the conditions of a temperature of 25 ° C., a relative humidity of 50%, and −5 ° C. The dynamic friction coefficient was measured by using a guide pin made of stainless steel (SUS304), applying a constant tension to the sample tape, and running while sliding on the guide pin at a tape speed of 5 mm / sec. Still durability was expressed as the time (minutes) until the playback output decreased by 3 dB when held in the pause state. In addition, shuttle durability was evaluated by the number of shuttles until the reproduction output was reduced by 3 dB after the shuttle traveled for 2 minutes each time. Table 4 shows the results.

In this table, the bars with bars in the respective columns of friction coefficient, still durability, and shuttle durability indicate that measurement was impossible because the friction coefficient was too high.

In Comparative Example 4 in which no lubricant was used, the test was not performed under other conditions because the coefficient of friction was already large and the durability was extremely poor at a temperature of 25 ° C. and a relative humidity of 60%. At this time, the running of the sample tape was unstable, and wear of the magnetic layer was also observed. In Comparative Example 3, in which nonadecafluorocarboxylic acid ammonium salt (lubricant 7) was used as a lubricant, these properties were considerably improved. However, Examples 13 to 18 to which the present invention is applied
The result of (1) is much more improved than that of Comparative Example 3. The reproduction output did not decrease by 3 dB even after the shuttle running was repeated 150 times, the running of the sample tape was extremely stable, and the wear was reduced. I was not able to admit.

〔The invention's effect〕

As is clear from the above description, the magnetic recording medium of the present invention is capable of maintaining a lubricating effect on the magnetic layer stably for a long period of time. Is held as a lubricant. Therefore, it is possible to provide a magnetic recording medium having excellent running stability and wear resistance. Especially,
By solving these problems in metal thin film type magnetic recording media, which had many points to be improved in running stability and wear resistance, high-density, high-quality magnetic recording and reproduction can be performed with high reliability. Become like

Claims (1)

(57) [Claims] 1. A non-magnetic support comprising a magnetic material on at least one surface thereof.
In the magnetic recording medium having a layer, the magnetic layer has a general formula C_nF_{2n + 1}(CH_Two)_mCOO N H_ThreeR (where n is a natural number, m is an integer of 2 or more, and R is water
Atom, unsubstituted hydrocarbon group, substituent-modified hydrocarbon group
Indicates one or the other. ) Fluorinated long-chain carboxyl
Acid ammonium salt or fluorinated long-chain carboxylic acid amine
A magnetic recording medium which retains salt.