JPH07220264A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To maintain lubricity over a long period of time by adding a lubricant prepd. by adding a long chain amine represented by a specified general formula to a phosphoric ester or phosphorous ester lubricant represented by a specified general formula to the surface of a magnetic layer. CONSTITUTION:This magnetic recording medium has a magnetic layer on the nonmagnetic substrate and the surface of the magnetic layer has been coated with a lubricant compsn. prepd. by adding a long chain amine represented by general formula II to a phosphoric ester or phosphorous ester represented by general formula I. This magnetic recording medium coated with the lubricant prepd. by adding the long chain amine represented by the formula II to the phosphoric ester or phosphorous ester having hydroxyl groups by 30-500mol% of the amt. of the ester exhibits satisfactory lubricating action, can improve its running performance and has improved durability.

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 such as a magnetic tape and a magnetic disk, which is a magnetic recording medium obtained by coating a lubricant containing a phosphoric acid or phosphite ester with a long-chain amine. It is about.

[0002]

2. Description of the Related Art In a so-called metal thin film type magnetic recording medium in which a ferromagnetic metal material is deposited on a non-magnetic support by a method such as vapor deposition and used as a magnetic layer, the smoothness of the magnetic layer surface is extremely good. Therefore, a substantial contact area with a sliding member such as a magnetic head or a guide roller is large, and thus a friction coefficient is increased, and an adhesion phenomenon (so-called sticking) is likely to occur, resulting in lack of running property and durability. There are many.

For example, a tape inserted in an 8 mm video deck is wound around a drum through 10 or more guide pins. At that time, the tape tension and the tape running speed were kept constant by the pinch roller and the capstan, the tension was about 20 g and the running speed was 0.5 c.
m / s. In this running system, the magnetic layer of the tape is in contact with a stainless guide pin that is fixed. Therefore, when the friction on the surface of the tape becomes large, the tape causes a stick-slip, a phenomenon called so-called tape squeaking occurs, and the playback screen becomes tight. Further, the relative speed between the tape and the head is very large, and particularly in the paused state, high-speed contact is made at the same place, which causes a problem of abrasion of the magnetic layer, leading to a reduction in reproduction output. In the case of vapor-deposited tape, the magnetic layer is so thin that this problem becomes more serious.

In a hard disk device, called a CSS (contact start stop), the magnetic head is in contact with the disk before the rotation, and the magnetic head is levitated by an air flow generated when the magnetic head starts rotating at a high speed. Therefore, the medium travels by rubbing the medium at the time of start-stop or start-up, and the increase in friction at that time is a serious problem. In order to maintain the product level reliability, it is desired that the friction coefficient after performing the CSS operation 20,000 times is 0.5 or less. Further, since it rotates at a high speed, the problem of head crash due to the head and the medium is one of the problems in the thin film medium.

Therefore, it has been studied to use various kinds of lubricants in order to improve these problems. Conventionally, a higher fatty acid or its ester is coated on the magnetic layer of the magnetic recording medium by topcoating so as to reduce friction. Attempts have been made to reduce the coefficient.

By the way, the lubricant used in the magnetic recording medium is required to have very strict characteristics, and it is difficult to cope with the conventional lubricant.

That is, the lubricant used in the magnetic recording medium is (1) excellent in low temperature characteristics so as to ensure a predetermined lubricating effect when used in cold regions, and (2) a lubricant with a magnetic head. Since pacing is a problem, it is necessary to be able to apply it extremely thinly, to exhibit sufficient lubrication characteristics even in that case, and (3) to endure long-term use or long-term use and to maintain the lubrication effect. To be done.

The most important solution to these problems of increasing coefficient of friction or durability is to study the lubricant applied to the surface. Good lubrication performance with the head, uniform and strong adhesion to the tape or disk surface, long-term retention of these performances (for example, 10 years), such requirements with a film thickness of about a single molecular level of about several nm To realize it, it is necessary to study the lubricant.

It has been known that the lubrication characteristics depend on the molecular structure of the lubricant, but those developed especially for magnetic recording media are roughly classified into three types: silicon-based, hydrocarbon-based, It is a fluorinated carbon system.

The silicon-based lubricant is one of the lubricants often used in the coating medium because of its good thermal stability and low vapor pressure. However, it does not have very good lubrication performance on thin film type magnetic recording media with very good surface properties like the present, and the lubrication characteristics in the pin-on-disk accelerated wear test or CSS test satisfy the durability specifications. do not do.
In other words, it is very limited in the silicon-based lubricant to form the oriented lubricating film on the surface of the thin film type magnetic recording medium, which is the mainstream at present, to satisfy the required lubricating characteristics.

Hydrocarbon-based lubricants are still the mainstream lubricants in coating type magnetic recording media. However, in terms of thermal or chemical stability, hydrocarbon-based lubricants are generally worse than silicon-based or fluorine-based lubricants, and frictional polymers formed by the reaction of molecules by friction, It is easily produced by a system that uses a hydrocarbon-based lubricant. This polymer reduces lubrication properties,
Sometimes it becomes a fatal failure. The high vapor pressure is one of the drawbacks of hydrocarbon lubricants. The thin-film magnetic recording medium exhibits excellent friction characteristics because the lubricant cannot be replenished, but the vapor pressure is high, so that it is difficult to use for the actual thin-film magnetic medium.

Fluorine-based lubricants are currently the most widely used lubricants in thin film magnetic recording media. Among the fluorine-based lubricants, the above-mentioned perfluoropolyether is widely used because it has better lubricating performance and surface protection action than other fluorine-based lubricants. For this reason C
Since the F ₂ —O—CF ₂ ether bond is flexible, the viscosity is low when the molecular weight is the same, and the viscosity does not change in a wide temperature range. In addition, it must be chemically inert, have low vapor pressure, have high thermal or chemical stability, have low surface energy, have good boundary lubrication properties, and have good water repellency. To be

The properties of perfluoropolyethers are very strongly dependent on their molecular structure. Several types of perfluoropolyethers are commercially available, which differ in molecular weight, backbone repeat units, and end groups. For example Fomb
The lin-Y type (made by Montecatini) is CF (CF ₃ )
While the repeating unit of the main chain has a branched structure in a random polymer of CF ₂ 0 and CF ₂ O, the Fomblim-Z type is a polymer of CF ₂ CF ₂ O and CF ₂ O and has a linear structure. have. The Demnum type (manufactured by Daikin Industries, Ltd.) and the Krytox type (manufactured by DuPont) are homopolymers of hexafluoropropylene oxide and hexafluoroisopropylene oxide, respectively. Due to their chemical inertness, perfluoropolyethers lack the ability to adsorb on the surface of magnetic media. Therefore, in order to improve the adsorption power, Fomblin Z-DOL, a perfluoropolyether with polar groups at both ends
(Hydroxyl group) and Fomblin AM2001 (piperonyl group) were developed. AM2001 has a very strong immobilization effect especially on the metal surface and carbon surface, and the introduction of polar groups at the ends reduces the friction coefficient and increases the service life of the magnetic disk. As described above, there are very strict demands on the lubricant for the thin film magnetic recording medium, and various measures have been taken, but there is no lubricant yet that satisfies the required characteristics.

Further, in a magnetic recording system in which the relative velocity exceeds several meters, the frictional heat generated at the contact portion causes the surface temperature to increase rapidly, though instantaneously. Although there is no accurate method for measuring the temperature at the contact point between the head and the medium, it is estimated by calculation to exceed several hundred degrees. Particularly under such boundary lubrication conditions, since a reactive surface appears, the temperature at such a contact point accelerates the decomposition reaction of the lubricant molecules. Perfluoropolyether is
It is stable in air at temperatures of 350 ° C or higher, but easily decomposes in the presence of metal alloys such as iron and titanium alloys, or Lewis acids and Lewis bases such as AlCl ₃ , FeF ₃ , and Al ₂ O ₃ . .

The decomposition of such a lubricant adversely affects the lubrication characteristics, which in turn results in a loss of reliability of the magnetic recording system. Therefore, it is necessary to develop not only lubricating characteristics, but also lubricants with less decomposition.

[0016] Further, perfluoropolyethers are problematic in terms of the global environment because they dissolve only in freons.

As described above, the properties required of the lubricant are extremely strict, and the reliability of the magnetic recording medium cannot be completely satisfied even if it has thermal or chemical stability or adsorption to the medium surface. is the current situation.

[0018]

As described above, in the field of magnetic recording media, due to the lack of ability of the lubricant used, practical characteristics such as running durability and the solvent used are unsatisfactory. I have left.

Therefore, the present invention provides a magnetic recording medium which has excellent lubricity under various conditions of use, has a long-lasting lubrication effect, and is excellent in running property, wear resistance, durability and the like. The purpose is to do.

[0020]

According to the present invention, a lubricant having a characteristic of phosphoric acid or phosphorous acid, which has a low friction, is newly synthesized, and as a result of earnest research, it is generally found that the above object is not achieved. The inventors have found that a lubricant obtained by adding a long-chain amine represented by the general formula 2 to the phosphoric acid or phosphite ester-based lubricant represented by the formula 1 is suitable for this purpose and completed the present invention. is there. In the past, it has been said that phosphoric acid ester exhibits excellent lubricating characteristics in a coated magnetic recording medium (Japanese Patent Laid-Open No. 4-192115). But,
As described above, the effect of hydrocarbon-based phosphoric acid or phosphorous acid alone is limited in its sustainability.

Therefore, it is said that it is necessary to increase the interaction with the magnetic layer in order to maintain the effect and maintain the lubricating property (H. Kondo et al, IEEE Trans.
MAG, vol. 26, pp2691, 1990). In this patent, in order to further improve the lubrication characteristics, a lubricant is prepared by adding 30 to 500% of a long-chain amine in molar ratio to phosphoric acid or phosphorous acid ester having a hydroxyl group represented by the general formula 1 It is intended to improve the durability by giving a salt structure inside and increasing the adsorptivity with the magnetic layer. Since phosphoric acid and phosphorous acid have a higher acidity than carboxylic acid, it is considered that they have stronger adsorptivity than the amine salt of carboxylic acid.

That is, the magnetic recording medium of the present invention is a magnetic recording medium in which at least a magnetic layer is formed on a non-magnetic support, and the phosphoric acid or phosphorous acid represented by the general formula 3 has a hydroxyl group. A magnetic recording medium is characterized by having a lubricant containing 30 to 500% of a long-chain amine represented by the general formula 4 in a molar ratio with respect to an ester.

[0023]

[Chemical 3]

M is an integer from 1 to 3. R ₁ represents a hydrocarbon having 10 or more carbon atoms. R ₂ has 2 to 4 carbon atoms
Is an alkylene group. n represents an integer from 1 to 30.

[0025]

[Chemical 4]

R represents a hydrocarbon having 10 or more carbon atoms. R
₃ R ₄ represents hydrocarbon or hydrogen.

That is, according to the present invention, by applying it to the surface of a thin film magnetic recording medium such as a vapor deposition tape, good durability can be obtained even when used under severe conditions such as high temperature and high humidity or low temperature and low humidity. Moreover, its characteristics do not deteriorate.

The structure of the phosphoric acid or phosphite ester having a hydroxyl group of the present invention is shown in the general formula 3, but it is sufficient if at least an oxyalkylene group, an alkyl group, and an aromatic ring are present in the molecule. Absent.

The long-chain amine is also represented by the general formula 4, but similarly, it can be selected regardless of the molecular weight, the number of carbon atoms, the branched structure, the unsaturation, the presence or absence of an aromatic ring, the isomer or the alicyclic structure. A linear or branched hydrocarbon having 10 or more carbon atoms is preferable from the viewpoint of friction coefficient or solubility.

The magnetic recording medium of the present invention has a lubricant containing a long-chain amine in a molar ratio of 30 to 500% with respect to phosphoric acid or phosphorous acid ester having a hydroxyl group.

The magnetic recording medium to which the present invention is applied is a so-called metal thin film type magnetic recording medium in which a magnetic coating film is formed as a magnetic layer on the surface of a non-magnetic support by a method such as vapor deposition. It is possible to Further, this metal thin film type magnetic recording medium can be applied to a magnetic recording medium having a structure in which an underlayer is interposed between a non-magnetic support and a magnetic layer. It can also be applied to a coating type magnetic recording medium.

In this case, the non-magnetic support and the metal magnetic thin film of the applicable metal thin film type magnetic recording medium are not particularly limited, and any conventionally known one can be used.

For example, as the non-magnetic support, the same as the above-mentioned coating type magnetic recording medium can be used. In this case, when a rigid substrate such as an Al alloy plate or a glass plate is used as the non-magnetic support, an oxide film such as an alumite treatment or a Ni-P film is formed on the surface of the substrate to harden the surface. You may do it.

The metal magnetic thin film is formed as a continuous film by a PVD method such as plating, sputtering or vacuum deposition, and is made of a metal such as Fe, Co or Ni, or Co-Ni.
Alloys, Co-Pt alloys, Co-Pt-Ni alloys,
Fe-Co based alloy, Fe-Ni based alloy, Fe-Co-N
Examples are in-plane magnetization recording metal magnetic films and Co-Cr alloy thin films made of i-based alloys, Fe-Ni-B-based alloys, Fe-Co-B-based alloys, Fe-Co-Ni-B-based alloys, and the like. .

Particularly in the case of in-plane magnetization recording metal magnetic thin film,
Bi, Sb, Pb, Sn, Ga, on the non-magnetic support in advance
An underlayer of a low-melting point non-magnetic material such as In, Ge, Si, or Ti is formed, and a metal magnetic material is vapor-deposited or sputtered from the vertical direction to diffuse the low-melting point non-magnetic material in the metal magnetic thin film. The orientation may be eliminated to secure the in-plane isotropic property, and the coercive force may be improved.

When the hard disk as described above is used, a hard protective film such as a carbon film, a diamond-like or amorphous carbon film, a chromium oxide film, a ZrO ₂ film, and a SiO ₂ film is formed on the surface of the metal magnetic thin film. You may do it.

The above-mentioned metal thin film type magnetic recording medium is
Perfluoropolyether and long-chain
Keep a phosphoric acid or phosphite ester lubricant with a kill group
As a method of providing, the surface of the metal magnetic thin film and the protection
There is a method of top-coating a lubricant layer on the film surface.
It In this case, perfluoropolyether is added to the ester moiety.
And long-chain alkyl group phosphoric acid or phosphorous acid ester
The amount of lubricant applied is 0.5 to 100 mg /
m²Is preferably 1 to 20 mg / m ²And
More preferably.

The above-mentioned phosphoric acid or phosphite ester-based lubricant having a perfluoropolyether and a long-chain alkyl group in the ester portion may be used alone as a lubricant for a magnetic recording medium. You may use it in combination.

Further, an extreme pressure agent may be used in combination at a weight ratio of about 30:70 to 70:30 in order to cope with more severe conditions and maintain the lubricating effect.

The extreme pressure agent reacts with the metal surface due to frictional heat generated when a metal contact is partially generated in the boundary lubrication region, and forms a reaction product film to perform a friction and wear preventing action. Which is a phosphorus-based extreme pressure agent,
Sulfur-based extreme pressure agent, halogen-based extreme pressure agent, organometallic extreme pressure agent,
Any compound type extreme pressure agent or the like can be used.

In addition to the above-mentioned lubricant and extreme pressure agent, a rust preventive agent may be used in combination if necessary. As the rust preventive, any rust preventive commonly used as a rust preventive for magnetic recording media of this type can be used, and examples thereof include phenols, naphthols, quinones, nitrogen atom-containing heterocyclic compounds, and oxygen atoms. And a heterocyclic compound containing a sulfur atom.

By the way, in the above-mentioned metal thin film type magnetic recording medium, a back coat layer, an undercoat layer and the like may be formed, if necessary, in addition to the metal magnetic thin film which is the magnetic layer.

For example, the back coat layer is formed by coating a resin binder similar to that of the magnetic coating film with a carbon-based fine powder for imparting conductivity and an inorganic pigment for controlling the surface roughness. is there. In the present invention, the long-chain amine is contained in the back coat layer in a molar ratio of 30 to 500 with respect to the phosphoric acid or phosphorous acid ester having a hydroxyl group.
%, The lubricant added may be internally added or may be contained by a top coat. Alternatively, the magnetic coating film, the metal magnetic thin film and the back coat layer are all internally added and top-coated as a lubricant in which a long-chain amine is added in a molar ratio of 30 to 500% to phosphoric acid or phosphorous acid ester having a hydroxyl group. , Various combinations are possible.

[0044]

[Function] A lubricant obtained by adding a long-chain amine in a molar ratio of 30 to 500% to phosphoric acid or phosphite having a hydroxyl group exhibits a good lubricating effect and reduces the friction coefficient. Further, this lubricating action is not impaired even under severe conditions such as low temperature. Therefore, a magnetic recording medium coated with a lubricant in which a long-chain amine is added to the phosphoric acid or phosphite having a hydroxyl group in a molar ratio of 30 to 500% is improved in running property due to the above-mentioned lubrication effect and is durable. The property is improved.

[0045]

EXAMPLES An example of the magnetic recording medium of the present invention will be described below. The magnetic recording media shown below were prepared using the compounds shown in Table 1. An example applied to a metal thin film type magnetic recording medium (vapor deposition tape) will be described.

Example 1 Co was deposited on a polyethylene terephthalate film having a thickness of 10 μm by the oblique vapor deposition method to form a ferromagnetic metal thin film having a thickness of 200 nm. Next, on the surface of this metal magnetic thin film, a lubricant composition prepared by dissolving stearylamine in an equimolar amount to the phosphoric acid ester having a hydroxyl group shown in Lubricant 1 in Table 1 dissolved in hexane was applied. 5 mg /
It was applied so as to have a size of m ² and cut into a width of 8 mm to prepare a sample tape.

[0047]

[Table 1]

Examples 2 to 28 In Examples 2 and 2, lubricants 2 to 28 in Table 1 were prepared by adding equimolar amounts of long-chain amines to the phosphoric acid ester or phosphorous acid ester having a hydroxyl group shown in Table 1, respectively. ~ Example 2
It corresponds to 8. A sample tape was prepared in the same manner as in Example 1 except for the above.

With respect to these tapes, the relative humidity at 25 ° C. was 6
Friction was measured under the conditions of 0%, 40 ° C. relative humidity 80% RH, and −5 ° C. The still durability (min) and the shuttle durability (times) were also measured under the same conditions. The results of these measurements are shown in Table 2.

[0050]

[Table 2]

Here, the still durability is preferably 60 minutes or more, and the shuttle durability is preferably 100 times or more. In all of Examples 1 to 28, this condition is satisfied. The friction coefficient is preferably 0.4 or less. In all of Examples 1 to 28, this condition is satisfied. The maximum value of the friction coefficient measured this time is 0.33 (Example 2). From this, it is understood that if the friction coefficient is at least 0.33 or less, the still durability and the shuttle durability can be satisfied at the same time.

As a comparative example, a blank tape containing no lubricant (Comparative Example 1), a phosphoric acid ester having a hydroxyl group (one in which stearylamine of the lubricant 7 was not added), a phosphorous acid ester having a hydroxyl group ( The measurement was performed for the case where the lubricant 14 to which stearylamine was not added) was used alone as a lubricant (Comparative Examples 2 and 3). The friction measurement results are also shown in Table 3.

[0053]

[Table 3]

In Comparative Examples 1 to 3, none of them simultaneously satisfied the friction coefficient, the still durability and the shuttle durability.

Next, a lubricant prepared by changing the amount of amine added to the phosphoric acid ester was prepared according to Table 4, and a sample tape was prepared in the same manner as in Example 1. Friction measurements were similarly performed on these tapes. The results are shown in Table 4. Here, in the experiment of Table 4, using the lubricant composition used in Example 1, the effect was investigated by changing the amount of stearylamine added to the phosphoric acid ester.

[0056]

[Table 4]

In Examples 29 to 36, the molar ratio% of amine to phosphoric acid was in the range of 30 to 500%, and the friction coefficient was 0.33 or less. Since the friction coefficient is 0.33 or less, the still durability and the shuttle durability can be satisfied at the same time. On the other hand, in Comparative Examples 4 and 5, the molar ratio of amine to phosphoric acid was 10% or 1000%, and the friction coefficient contained a value larger than 0.33.

As is clear from the results of Tables 2 and 4,
As a lubricant, the long-chain amine is used in a molar ratio of 30 to 500% with respect to phosphoric acid or phosphite having a hydroxyl group at the end.
By using it as a lubricant added in the above range, the friction coefficient did not increase under various conditions, and very good results were obtained.

As is clear from the above description, the magnetic recording medium of the present invention has a long-chain amine in a molar ratio of 30 with respect to phosphoric acid or phosphorous acid ester having a hydroxyl group at the terminal, which has extremely excellent lubricity. Since the lubricant added in the range of 1 to 500% is retained, the lubricity can be maintained under any use condition, and the lubricity can be maintained for a long period of time. Therefore, the magnetic recording medium of the present invention is excellent in wear resistance, durability, and especially running property.

The present invention is not limited to the above-mentioned embodiments, and it goes without saying that various other configurations can be adopted without departing from the gist of the present invention.

[0061]

As described above, according to the present invention,
It has a very good lubricity and a long-chain amine in a molar ratio of 3 to phosphoric acid or phosphite having a hydroxyl group at the terminal.
Since the lubricant added is in the range of 0 to 500%, the lubricity can be maintained under any use condition, and the lubricity can be maintained for a long period of time.
Therefore, the magnetic recording medium of the present invention is excellent in wear resistance, durability, and especially running property.

Claims (2)

[Claims] 1. A magnetic recording medium comprising at least a magnetic layer on a non-magnetic support, wherein a phosphoric acid ester or phosphorous acid ester type lubricant represented by the following general formula 1 is present on the surface of the magnetic layer. A magnetic recording medium characterized in that a lubricant composition containing a long-chain amine represented by the general formula 2 is applied. [Chemical 1] m is an integer from 1 to 3. R ₁ represents a hydrocarbon having 10 or more carbon atoms. R ₂ represents an alkylene group having 2 to 4 carbon atoms. n represents an integer from 1 to 30. [Chemical 2] R represents a hydrocarbon having 10 or more carbon atoms. R ₃ and R ₄ represent hydrocarbon or hydrogen. 2. The magnetic recording medium according to claim 1, wherein the long-chain amine is added in a molar ratio of 30 to 500% with respect to the phosphoric acid ester or the phosphorous acid ester.