JPH02139715A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve traveling property and durability of a magnetic recording medium by incorporating fluorinated long-chain carboxylic acid ammonium salt or fluorinated long-chain carboxylic amino salt as a lubricant into a magnetic layer or applying the lubricant on the magnetic layer formed on one side of the substrate. CONSTITUTION:The magnetic recording medium has the magnetic layer formed on at least one side of the nonmagnetic substrate, and the magnetic layer contains fluorinated long-chain carboxylic acid ammonium salt or fluorinated long-chain carboxylic amino salt represented by CnF2n+1(CH2)mCOO<->N<+>H3R [wherein, (n) is a natural number, (m) is an integer >=2, R is hydrogen, unsubstd. hydrocarbon, or hydrocarbon with substd. groups]. The fluorinated long-chain carboxylic acid ammonium salt or fluorinated long-chain carboxylic amino salt is incorporated into the magnetic layer or applied on the surface of the magnetic layer by coating. By this method, the magnetic layer stably maintains lubricating effect for a long time and the obtained medium has excellent travel ing durability and wear resistance.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a magnetic recorder such as a 6i1 tape, a 111 disc, etc. In the magnetic recording medium formed by the above-mentioned magnetic layer, running properties and durability of the magnetic recording medium can be improved by internally adding or coating a fluorinated long-chain carboxylic acid ammonium salt or a fluorinated long-chain carboxylic acid amine salt as a lubricant to the magnetic layer. The aim is to improve the

[Prior Art] Conventionally, in the field of magnetic recording, recordings of Fe20=, Co-containing rFezO=, Fe:IO on a non-magnetic support such as a polyester film or a polyethylene terephthalate (PET) film have been used. .

Co-containing Fe5oa, r Fezo3 and Fe
.

Powder magnetic materials such as helutolide compounds with 04, oxide magnetic powders such as CrO□, or alloy magnetic powders containing Fe, Co, Ni, etc. as main components, vinyl chloride-vinyl acetate copolymers, polyester resins.

2. Description of the Related Art So-called coated magnetic recording media, which are produced by applying and drying a magnetic paint dispersed in an organic binder such as a polyurethane resin, are widely used.

On the other hand, with the increasing demand for high-density magnetic recording, magnetic materials made of metals or alloys such as Co-Ni alloys are being made using plating or vacuum thin film formation techniques (vacuum evaporation, sputtering, ion blating, etc.). ) to form a metal magnetic thin film directly on a non-magnetic support.
A so-called metal thin film type magnetic recording medium has been proposed and is attracting attention. This metal'III film type magnetic recording medium has excellent coercive force squareness ratio, electromagnetic conversion characteristics in the short wavelength range, etc., and the thickness of the magnetic layer can be made extremely thin, so it is easy to use during recording demagnetization and reproduction. It has a number of advantages, such as a significantly small loss in thickness and the fact that the magnetic layer does not contain a non-magnetic material such as a resin binder, making it possible to increase the packing density of the magnetic material.

These magnetic recording media are used in sliding contact with a magnetic head, so from the viewpoint of maintaining excellent electromagnetic conversion characteristics and preventing problems such as dropouts, it is important to ensure that the surface of the magnetic layer (sufficiently smooth and magnetically It is necessary to maintain good contact with the head.However, if the surface of the magnetic layer is extremely smooth, the substantial contact area with sliding members such as the magnetic head and guide rollers may be reduced. becomes too large, and adhesion phenomenon (so-called sticking) tends to occur.

When such sticking occurs, the running properties and the durability of the magnetic layer are reduced.

Therefore, in order to solve this problem, the use of various lubricants has been considered.
Alternatively, attempts have been made to reduce the coefficient of friction by coating the surface of the magnetic layer.

[Invention tries to solve! ! [Title] By the way, lubricants used in magnetic recording media must: ■ have excellent low-temperature properties so as to ensure the desired lubrication effect even when used in particularly cold regions; It is required to have characteristics such as being able to be applied thinly by bending in consideration of spacing, and exhibiting a sufficient lubricating effect; and (1) maintaining the lubricating effect for a long time.

However, the reality is that the lubricating effects of conventionally used lubricants tend to decrease due to reasons such as solidification under low-temperature conditions or being gradually scraped off by magnetic heads etc. after long-term use. Ta.

The present invention was proposed in view of the above circumstances, and an object of the present invention is to provide a magnetic recording medium that has excellent running properties and durability.

[Means to solve the problem]

As a result of repeated studies to achieve the above object, the present inventors found that fluorinated long-chain carboxylic acid ammonium salts or fluorinated long-chain carboxylic acid amine salts can be
It was discovered that a good lubricating effect is exhibited over a period of υ1, and the present invention was developed.

The magnetic recording medium according to the present invention is a cf1 magnetic recording medium in which a magnetic layer is formed on at least one surface of a non-magnetic support.
(where n is a natural number, m is an integer of 2 or more, and R is a hydrogen atom, an unsubstituted hydrocarbon group, or a substituent-modified hydrocarbon group). It is characterized by holding a fluorinated long-chain carboxylic acid ammonium salt or a fluorinated long-chain carboxylic acid amine salt represented by any one of the following.

The fluorinated long-chain carboxylic acid ammonium salt or fluorinated long-chain carboxylic acid amine salt used in the present invention has a negatively charged moiety formed by the perfluoroalkyl method.

It is considered to be a molecular ion in which a polymethylene group 3 and a carboxyl group are bonded in a linear chain. 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 thus synthesized fluorinated long-chain carboxylic acid from an appropriate organic solvent together with ammonia or a primary amine, an ammonium salt of a fluorinated long-chain carboxylic acid or an amine salt of a fluorinated long-chain carboxylic acid can be obtained. can be obtained.

Here, the number n of carbon atoms in the perfluoroalkyl group is a natural number. The range of carbon number n is not particularly limited, but it is preferably from 3 to 10. If it is less than 3, sufficient lubricating effect will not be obtained, and if it is larger than 10, solidification may easily occur, etc. Problems may occur and lubricity may not be achieved. Therefore, it may be set as appropriate within a range that does not impair practicality.

The number m of carbon atoms in the polymethylene group is an integer of 2 or more.

As is clear from the above reaction route, the synthesis of fluorinated long-chain carboxylic acids is an 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 methyl acrylate, which has the lowest molecular weight, is used as this type of unsaturated carboxylic acid methyl ester. When the value of m is larger to some extent, the melting point of the final fluorinated long-chain carboxylic acid ammonium salt or fluorinated long-chain carboxylic acid amine salt increases.

It is more preferably selected to be 5 or more because it is advantageous in terms of heat resistance especially when undergoing annealing treatment in the hard disk manufacturing process. Moreover, since the upper limit of the carbon number m is not particularly limited, it can be set as appropriate within a range that does not impair practicality.

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

Here, in the magnetic recording medium to which the present invention is applied, a magnetic layer is first formed by applying a magnetic paint made by dispersing and kneading a magnetic material together with a dispersant and other additives onto the surface of a non-magnetic support. Examples include so-called coating type magnetic recording media and so-called metal thin film type magnetic recording media in which a magnetic layer is formed by directly depositing a magnetic material on a nonmagnetic support using vacuum thin film formation technology.

As the magnetic material, binder and other additives, non-magnetic support, etc. used in these magnetic recording media, any conventionally known materials can be used, and there are no limitations at all.

In the present invention, methods for retaining a fluorinated long-chain carboxylic acid ammonium salt or a fluorinated long-chain carboxylic acid amine salt in the magnetic layer include a method of adding it internally 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 a fluorinated long-chain carboxylic acid ammonium salt or a fluorinated long-chain carboxylic acid amine salt is internally added to the magnetic layer, it is added in an amount of 0.2 to 20 parts by weight per 100 parts by weight of the binder.

When coating the surface of the magnetic layer with fluorinated long-chain carboxylic acid ammonium salt or fluorinated long-chain carboxylic acid amine salt, the coating amount is 0.5 to 100 mg/m.
More preferably 1 to 20 mg/m''. For coating, these are dissolved in a suitable organic solvent to form a lubricant solution, and this is applied or sprayed, or the magnetic recording medium is placed in this lubricant solution. Just soak it.

The above-mentioned fluorinated long-chain carboxylic acid ammonium salt or fluorinated long-chain carboxylic acid amine salt 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 also be used in combination with perfluoroalkylcarboxylic acid ester, monocarboxylic acid perfluoroalkyl ester, perfluoroalkylcarboxylic acid perfluoroalkyl ester, or derivatives thereof.

The magnetic recording medium of the present invention may be one in which a back coat layer is provided on the side of the nonmagnetic support on which the magnetic layer is not formed. In this case, the back coat layer can also retain the aforementioned fluorinated long-chain carboxylic acid ammonium salt or fluorinated long-chain carboxylic acid amine salt by internal addition or coating.

[Effect]

It is generally known that perfluoroalkyl groups have the effect of lowering the coefficient of friction, but intermolecular interactions are generally small, and the strength of the coating is insufficient, especially when coated, making it difficult to maintain a lubricating effect. The drawback was 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 that is not bulkier than the perfluoroalkyl group is bonded to the perfluoroalkyl group to increase the chain length. As a result, intermolecular interactions are enhanced. Therefore, when it is retained in the magnetic layer by internal addition or coating, it exhibits a sufficient lubricating effect, and particularly when coated, it increases the strength of the coating. 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 coated magnetic tape will be described.

Example 1 First, 8 rounds of a magnetic coating composition were prepared according to the following composition.

Co adhesion r FezO3 100 parts by weight Hinychloride-vinyl acetate copolymer [Binder] (manufactured by U, C, C, Inc., trade name VAGH) 10.5 parts by weight Polyurethane resin [Binder] (Nippon Po'Jtsul) , manufactured by Tan Co., product name ?l-5033)
10.5 parts by weight carbon blank [antistatic agent]
5 parts by weight lecithin [dispersant] 1 part by weight methyl ethyl ketone [1150 parts by weight solvent methyl isobutyl ketone [3150 parts by weight solvent 1) as a lubricant
．． 5 parts by weight were added, mixed in a ball mill for 24 hours, filtered through a 3 μm filter, and further 4 parts by weight of an isocyanate curing agent was added and stirred for 30 minutes. This magnetic paint was applied onto a PET film having a thickness of 14 μm so that the thickness after drying would be 5 μm, subjected to a magnetic field orientation treatment, dried and rolled up. After further calendar processing, 1/
A sample tape was created by cutting it into a 2-inch width.

Examples 2 to 6 As a lubricant, instead of the above-mentioned hebutadecafluorononadecanoic acid stearylamine salt (Lubricant 1), Lubricant 2 to Lubricant 6 shown in the construction table below were 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 I, except that nonadecafluorocarboxylic acid ammonium salt (Lubricant 7 in Table 1) was used as the lubricant. This compound differs from the lubricants used in this invention in that its positively charged moiety does not have a polymethylene group between the perfluoroalkyl and carboxyl groups.

The first table shows the stain slip characteristics at a temperature of 25℃ and a relative humidity of 60℃.
%, or under the following conditions: temperature: 40° C., relative humidity: 80%. The results are shown in Table 2. In the stick-slip evaluation, a good case was given and a poor O1 case was given a ×.

(Left space below) Table 2 shows the friction coefficient before and after aging for each sample tape made as described above. In the examples, the coefficient of friction is reduced and the stain slip characteristics are improved compared to the comparative examples.

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, an nN i-P plating layer with a thickness of 15 μm was formed /M! -Mg alloy substrate (thickness 1.5 mm, outer diameter 95 mm, inner diameter 25 mm)
is prepared, and a gas pressure of lXl0-5T is applied on top of this plating layer.
Bi was deposited to a thickness of 200 mm by electron beam evaporation at orr+substrate temperature of 150°C.

Next, a gas pressure I is applied to the non-magnetic metal underlayer in the same manner.
Co is deposited to a thickness of 1000 nm by electron beam evaporation at Xl0-'Torr and substrate temperature of 150°C to form a metal magnetic thin film, and a carbon protective film is further deposited on this metal magnetic thin film by vacuum evaporation. was formed.

Finally, on the surface of the carbon protective film, heptadecafluorononadecanoic acid stearylamine salt (Lubricant 1) shown in Table 1 above was applied as a lubricant in an amount of 5 mg/g/g.
A sample disk was prepared by coating the sample disk so as to give a coating thickness of 100 mm.

Examples 8 to 12 Instead of the above-mentioned hebutadecafluorononadecanoic acid stearylamine salt (lubricant 1) as a lubricant, the above-mentioned first
Sample disks were prepared in the same manner as in Example 7, except that each of Lubricant 2 to Lubricant 6 shown in the table was added.

Contact start/stop (C3S)
) characteristics were measured. That is, after contact start and stop were repeated 20,000 times with the head load of the ferrite magnetic head being 9.5 g, the coefficient of static friction between each sample disk and the ferrite magnetic head was measured. The results are shown in Table 3.

Table 3 Comparative Example 2 In this comparative example, a sample disk was prepared in the same manner as in Example 7 except that nonadecafluorocarboxylic acid ammonium salt (Lubricant 7 in Table 1) was used as the lubricant.

From Table 3 of each sample prepared as described above, Examples 8 to 12 all achieved C3S characteristics superior to Comparative Example 2. Comparing each example, which example? , 8.10°11, the friction coefficient value did not increase significantly from the value shown in Table 2, whereas in Example 9 and Example 12, the rate of increase was slightly higher.
Based on this fact, it is better to use a long-chain hydrocarbon group as the R portion of the primary amine ion than a cyclic hydrocarbon group such as a phenyl group or a cyclohexyl group to improve the running properties of the magnetic recording medium. It can be seen that this is preferable from the viewpoint of improving durability.

Stearylamine fluorononadecanoic acid salt (lubricant 1) was applied to the sample tape at a coating density of 5 mg/m2, subjected to magnetic field orientation treatment and calender treatment, and then cut into 1/2 inch pieces to prepare sample tapes.

Examples 14 to 18 Instead of the above-mentioned hebutadecafluorononadecanoic acid stearylamine salt (lubricant l) as a lubricant, the above-mentioned first
Sample tapes were prepared in the same manner as in Example 13, except that each of Lubricant 2 to Lubricant 6 shown in the table was added.

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

Example 13 First, Go was deposited on a 14 μmW PET film by oblique vapor deposition to form a ferromagnetic metal FA film with a thickness of 1000 μm. Subsequently, on this ferromagnetic metal thin +1Q, heptadecaf Comparative Example 3 shown in Table 1 above was applied as a lubricant to nonadecafluorocarboxylic acid ammonium salt (Lubricant 7 in Table 1) as a lubricant. A sample tape was prepared in the same manner as in Example 13, except that .

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.

Table 4 For each sample tape prepared as described above, the coefficient of dynamic friction, methyl durability and shuttle durability were measured under the following conditions: temperature 25°C, relative humidity 50%, and -5°C. The above f) + friction coefficient is stainless steel (S
Measurements were taken by using a guide pin manufactured by US Pat. Still durability was expressed as the time (minutes) until the playback output decreased by 3 dB when held in a paused state.

Shuttle durability was evaluated by running the shuttle for 2 minutes each time and determining the number of shuttle runs until the reproduction output decreased by 3 dB. These results are shown in Table 4.

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

In Comparative Example 4 where no lubricant was used, the temperature was 25°C1
Since the friction coefficient was already large and the durability was significantly poor at a relative humidity of 60%, no tests were conducted under other conditions. At this time, the running of the sample tape was unstable, and abrasion of the four supporting layers was also observed. In Comparative Example 3, in which nonadecafluorocarboxylic acid ammonium salt (Lubricant 7) was used as the lubricant, these characteristics were considerably improved.

However, Examples 13 to 18 applying the present invention
The results shown in Comparative Example 3 are even more significant than Comparative Example 3. Even after 150 shuttle runs, there was no 3 dB drop in the playback output, the sample tape ran extremely stably, and there was no wear. I was not able to admit.

It retains acid amine salts as lubricants. therefore,
It becomes possible to provide a magnetic recording medium with excellent running stability and IY wear resistance. In particular, metal F!, which had conventional running stability and wear resistance that needed improvement! V If! By solving these problems in the J-type magnetic recording medium, high-density, high-quality magnetic recording and reproduction can be performed with high reliability.

Claims (1)

[Claims] A magnetic recording medium comprising a magnetic layer on at least one surface of a non-magnetic support, wherein the magnetic layer has the general formula C_nF_2_m_+_2(CH_2)_mCOO^■
N^■H_3R (in the formula, n is a natural number, m is an integer of 2 or more, and R represents any one of a hydrogen atom, an unsubstituted hydrocarbon group, and a substituent-modified hydrocarbon group). A magnetic recording medium characterized by retaining an ammonium salt of an enlarged long-chain carboxylic acid or an amine salt of a fluorinated long-chain carboxylic acid.