JPH08235572A - Magnetic recording medium - Google Patents

Abstract

PURPOSE: To sustain a lubricating effect over a long time as well as to maintain superior lubricity under various service conditions and to ensure superior running performance, wear resistance and durability by synthesizing and using a novel lubricant made of a long chain amine salt of phosphoric or phosphorous ester. CONSTITUTION: In a magnetic recording medium with a magnetic layer on the nonmagnetic substrate, a lubricant made of a long chain amine salt of phosphoric or phosphorous ester represented by formula 1 or 2 is applied on the magnetic layer. Lubricity can be maintained even under any service conditions, this lubricity can be maintained over a long period of time and the running performance, wear resistance and durability of the magnetic recording medium can be made superior. In the formulae 1, 2, R1 is >=10C hydrocarbon, at least one of R2 -R5 is >=10C hydrocarbon and the others are 1-20C hydrocarbons.

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 or a magnetic disk.

[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 very 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 large, and an adhesion phenomenon (so-called sticking) is likely to occur, resulting in problems such as lack of running property and durability. Many.

For example, a magnetic 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.
It is 5 cm / 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 CSS (contact start stop) type hard disk device, the magnetic head is in contact with the magnetic disk before the rotation, and is levitated by the air flow generated when the magnetic head is rotated 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 is rotating at a high speed, the problem of so-called head crash due to the magnetic head and the magnetic recording medium, that is, the magnetic disk is one of the problems in the thin film magnetic recording medium.

Therefore, it has been studied to use various kinds of lubricants in order to solve these problems, and a lubricant such as higher fatty acid or its ester has been conventionally top-coated on the magnetic layer of the magnetic recording medium. Therefore, attempts have been made to suppress the coefficient of friction.

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 for the magnetic recording medium has the following problems: (1) excellent low-temperature characteristics so that a predetermined lubricating effect is ensured when used in cold regions, and (2) spacing with the magnetic head. Therefore, it is required that the coating can be applied extremely thinly, sufficient lubrication characteristics can be exhibited even in that case, and (3) that the lubricating effect can be maintained for a long time or long-term use, and the like.

The most important solution to these problems of increased coefficient of friction or durability is to consider the lubricant applied to the surface. The requirements for good lubrication performance with a magnetic head, uniform and strong adhesion to the surface of a magnetic recording medium such as a magnetic tape or magnetic disk, and long-term (for example, 10 years) retention of these performances are about a few nm. In order to achieve a level of film thickness, it is necessary to study lubricants.

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

The silicon-based lubricant is one of the lubricants often used in the coating type 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 lubricants are still the predominant lubricants in coating type magnetic recording media. However, in terms of thermal or chemical stability, hydrocarbon-based lubricants are generally inferior to 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 the lubrication properties and is sometimes a catastrophic failure. The high vapor pressure is one of the drawbacks of hydrocarbon lubricants. Since the thin film magnetic recording medium cannot replenish the lubricant, it exhibits excellent friction characteristics, but it is difficult to be used for an actual thin film magnetic recording medium because of its high vapor pressure.

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 Fo
mblin-Y (made by Montecatini) type is CF (C
In F ₃ ) CF ₂ O and CF ₂ O random polymers, the repeating units of the main chain have a branched structure.
The blin-Z type is a polymer of CF ₂ CF ₂ O and CF ₂ O and has a linear structure. The Demnum (manufactured by Daikin Industries, Ltd.) type and the Krytox (manufactured by DuPont) type 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 adsorptive power, Fomblin-Z-DOL (hydroxyl group), a perfluoropolyether having polar groups at both ends
And Fomblin AM2001 (piperonyl group) were developed. Fomblin AM2001 has a very strong immobilizing action especially on the metal surface or 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 devises have been made, but there is no lubricant yet that satisfies the required characteristics.

In a magnetic recording system having a relative velocity exceeding several m / s, the frictional heat generated at the contact portion causes the surface temperature to increase suddenly, 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 to exceed several hundred degrees in the evaluation by calculation. 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.

Although perfluoropolyether is stable in air at temperatures of 350 ° C. or higher, metal alloys such as iron and titanium alloys, Lewis acids and Lewis bases such as AlCl ₃ , FeF ₃ and Al ₂ O _{3 are used.} It becomes easy to decompose in the presence of.

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. In addition, perfluoropolyethers are only environmentally friendly 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.

[0017]

As described above, in the field of magnetic recording media, the practical properties such as running property and durability are unsatisfactory due to the lack of ability of the lubricant and protective film used. Is 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.
Specifically, the problem of exhaustion of the lubricant, which is a drawback of the hydrocarbon lubricant, is solved, and the molecular design of the lubricant is carried out by taking advantage of the advantages of the hydrocarbon lubricant, for example, that it is inexpensive. The purpose of the present invention is to achieve the object by newly synthesizing a phosphate ester long-chain amine salt lubricant.

By the way, as a lubricant for use in a magnetic recording medium, particularly a thin film magnetic recording medium, it must first have an ability to be adsorbed to a magnetic layer, and since it is diluted with a solvent at the time of manufacture, it is soluble in an organic solvent. Is an important point. The use of phosphoric acid or phosphorous acid ester as a lubricant is disclosed in, for example, Japanese Patent Application Laid-Open No. 4-192115, but in this case, the adsorptivity to the magnetic layer is poor. Therefore, it was proposed in Japanese Patent Application No. 6-10038 “magnetic recording medium” as a lubricant for improving it. There is an amine salt, but in this case, it has a phenyl group and may not have sufficient solubility in a solvent.

[0020]

In the present invention, as a result of earnestly researching those which do not achieve the above-mentioned object, a lubricant suitable for the above-mentioned object was found, and the magnetic recording medium of the present invention was provided. It is a thing.

That is, the magnetic recording medium according to the present invention is a magnetic recording medium having at least a magnetic layer on a non-magnetic support, and is represented by the following general formula (3) or (4).
Alternatively, a phosphoric acid or phosphite ester long-chain amine salt lubricant represented by 2 is coated on the magnetic layer.

[0022]

Embedded image

[0023]

[Chemical 4] (Here, R ₁ is a hydrocarbon having 10 or more carbon atoms, R ₂ , R
_At least one of ₃ , R ₄ and R ₅ has 1 carbon atom
Shows 0 or more hydrocarbons, other than 1 has 20 or more carbon atoms
Up to hydrocarbons. )

[0024]

The present invention, as described above, applies the phosphoric acid or phosphorous acid ester long-chain amine salt lubricant represented by the general formula 1 or 2 of (Chemical formula 3) or (Chemical formula 4) to the surface of the magnetic layer. Provides a good lubrication effect to reduce the friction coefficient as well as to improve the still durability and shuttle durability, and this lubrication effect is not impaired even under severe conditions such as low temperature. The medium can be configured.

[0025]

EXAMPLE A magnetic recording medium of the present invention is a magnetic recording medium having at least a magnetic layer formed on a non-magnetic support, and the magnetic layer has the general surface of the above (Chemical Formula 3) or (Chemical Formula 4). A phosphoric acid or phosphite ester long-chain amine salt-based lubricant represented by the formula 1 or 2 is applied, wherein the long-chain ester of hydrocarbon enhances the solubility in a solvent The salt enhances the adsorptivity to the magnetic layer.

That is, the present invention provides good durability even when a thin film magnetic recording medium such as a vapor deposition tape is used under severe conditions such as high temperature and high humidity or low temperature and low humidity, and its characteristics. Does not deteriorate.

The magnetic recording medium to which the present invention is applied can be applied to a so-called metal thin film type magnetic recording medium in which a magnetic layer is formed on the surface of a non-magnetic support by a method such as vapor deposition. Is. 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. 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, polyethylene terephthalate similar to the 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 alumite treatment or Ni-P is formed on the surface of the substrate.
A film or the like may be formed to harden the surface.

The metal magnetic thin film as the magnetic layer is formed as a continuous film by a PVD (Physical Vapor Deposition) method such as plating, sputtering or vacuum deposition.
e, Co, Ni and other metals, Co-Ni alloys, Co-P
t-based alloy, Co-Pt-Ni-based alloy, Fe-Co-based alloy, Fe-Ni-based alloy, Fe-Co-Ni-based alloy, Fe
-Ni-B system alloy, Fe-Co-B system alloy, Fe-Co
Examples are an in-plane magnetization recording metal magnetic film and a Co—Cr alloy thin film made of —Ni—B alloy. In particular, in the case of an in-plane magnetization recording metal magnetic thin film, Bi, S is previously formed on a non-magnetic support.
An underlayer of a low melting point non-magnetic material such as b, Pb, Sn, Ga, In, Ge, Si, or Ti is formed in advance, and a metallic magnetic material is vapor-deposited or sputtered from the vertical direction, and these low magnetic materials are deposited in the metallic magnetic thin film. The melting point non-magnetic material may be diffused to eliminate the orientation to secure the in-plane isotropic property and improve the anti-magnetism.

As a method of retaining a lubricant on it
The most common method is to use a metal magnetic thin film surface or
Similarly, dip coat a lubricant layer on the protective film surface.
Method. In this case, the amount of lubricant applied
Is 0.5 to 100 mg / m ²Is desirable,
1-20 mg / m²Is more preferable. this
Is 1 mg / m²Less than 0.5 mg / m²Less than
20 mg / m due to durability issues²Especially when
100 mg / m²Drive exceeds the drive system of the magnetic recording medium.
The problem of "sticking" with the sliding parts in the system occurs
Will be.

In order to solve the problem of exhaustion, which is a problem of hydrocarbon lubricants, phosphoric acid or phosphorous acid amine salt is used as the polar group of the lubricant in the present invention. Because of this salt structure, adsorptivity with the magnetic layer is increased, and as a result, volatility is reduced and the problem of depletion can be solved.

The novel lubricant, phosphoric acid or phosphite ester long chain amine salt type lubricant, can be easily synthesized from, for example, phosphoric acid or phosphite and a quaternary ammonium salt having a long chain hydrocarbon. Is. The phosphoric acid and phosphorous acid are not limited as long as they have a long-chain hydrocarbon group, and the long-chain hydrocarbon R ₁ also has a carbon number of 1
If it is 0 or more, the objective is achieved. Phosphoric acid or phosphite can be easily obtained by reacting with phosphoric acid or phosphorous acid alkali or alkali metal, respectively. That is, raw material synthesis is easy.

Hydrocarbon radicals R ₂ , R ₃ , of the ammonium salt,
Regarding R ₄ and R ₅ , it becomes possible to improve the friction characteristics, durability or solubility of the lubricant by retaining the hydrocarbon group. That is, at least one of them must have 10 or more carbon atoms. When the number of carbon atoms of all hydrocarbons is 10 or less, durability or friction is impaired. Further, the quaternary structure prevents dissociation in the solvent, and the original properties of the lubricant can be maintained. That is, in the case of a tertiary salt, since it becomes phosphoric acid or phosphorous acid corresponding to the tertiary amine which is each constituent, there is a possibility of dissociation especially in paint or solvent, It may not function. There is no particular limitation on the structure of the hydrocarbon moiety of R ₁ , R ₂ , R ₃ , R ₄ and R ₅ , and it can be used regardless of branching, carbon number, double bond or the presence or absence of an aromatic ring. Is.

These lubricants may be applied alone on the magnetic recording medium, but conventionally known lubricants such as long-chain carboxylic acids or esters thereof generally used for magnetic recording media. , Long-chain alcohols may be used 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 by frictional heat generated when a metal contact is partially generated in the boundary lubrication region, and forms a reaction product film to prevent friction and wear. Any of a phosphorus-based extreme pressure agent, a sulfur-based extreme pressure agent, a halogen-based extreme pressure agent, an organometallic extreme pressure agent, a complex-based extreme pressure agent, and the like can be used.

In addition to the above 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.

In addition, in the above-mentioned metal thin film type magnetic recording medium, in addition to the metal magnetic thin film which is the magnetic layer, an undercoat layer or the like may be formed under the back coat layer or the magnetic film if necessary. Good.

The magnetic recording medium having the above-mentioned magnetic layer surface coated with a phosphoric acid or phosphite ester long-chain amine salt-based lubricant not only exerts a good lubricating action to reduce the friction coefficient but also still durability and shuttle durability. Improve sex. Also,
This lubricating action is not impaired even under severe conditions such as low temperature.

Specific examples of the present invention will be described below, but it goes without saying that the present invention is not limited to these examples. The magnetic recording media shown below were prepared using the compounds shown in Table 1 below. An example applied to a metal thin film type magnetic recording medium (vapor deposition tape) will be described.

Example 1 Co was adhered to 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, a lubricant prepared by dissolving Lubricant 1 in Table 1 below in a mixed solvent of ethanol and hexane was applied at a coating amount of 5 mg / m ² and cut into 8 mm width to prepare a sample tape.

[Examples 2 to 13] The same as Example 1 except that the lubricant 1 in Table 1 used as the lubricant in Example 1 was replaced with the lubricants 2 to 13. A sample tape was prepared according to the method. About each sample tape manufactured as described above, the temperature is 25 ° C. and the humidity is 60.
%, The temperature was −5 ° C. and the temperature was 40 ° C. and the humidity was 80%. For still durability, the decay time until the output decreased by 3 dB in the paused state was evaluated. The shuttle durability was evaluated by the number of shuttles until the output decreased by 3 dB after the shuttle traveled for 2 minutes each time. The results are shown in Table 2 below.

[0041]

[Table 1]

[0042]

[Table 2]

Comparative Example 1 In Example 1, the following Table 3
As shown in, a blank tape containing no lubricant was prepared. [Comparative Examples 2 and 3] In Example 1, the quaternary ammonium salt containing a long-chain hydrocarbon similar to phosphoric acid and phosphorous acid containing a long-chain hydrocarbon, which is the raw material shown in Table 2, was used as the lubricant.

[0044]

[Table 3]

Table 4 below shows the measurement results of each friction coefficient, still durability and shuttle durability of Comparative Examples 1 to 3.

[0046]

[Table 4] As is clear from the comparison of the results in Tables 2 and 4, the phosphoric acid or phosphorous acid ester long-chain amine salt-based lubricant coated on the magnetic layer was compared with the case where the raw materials were used alone.
Durability such as friction coefficient, still durability, shuttle durability, etc. was very good under various conditions. Further, it can be seen that excellent results are obtained with almost no deterioration due to aging.

Next, the results of examining the solubility in a solvent will be described. As the lubricant at that time, the lubricant 7 in Table 1 was used. Hexane, ethanol, methyl ethyl ketone, and chloroform were used as the solvent, and dissolved in these solvents at a concentration of 1 g / 100 cc or more. this is,
The concentration is high enough for practical use in production. That is, it dissolves in a commercially available inexpensive hydrocarbon-based, alcohol-based, ketone-based, or halogen-based solvent, and there is almost no problem in production.

[0048]

As is apparent from the above, the present invention constitutes a magnetic recording medium by coating a newly developed long-chain amine salt lubricant of phosphoric acid or phosphite on a magnetic layer. Thus, by coating the long-chain amine salt lubricant of phosphoric acid or phosphorous acid ester on the magnetic layer in this manner, the lubricity can be maintained under any use condition, and this lubricity can be maintained for a long time. Can be kept. Therefore, the magnetic recording medium of the present invention is excellent in running property, wear resistance and durability. Further, since it dissolves in a commercially available inexpensive organic solvent, there are almost no problems in production.

Claims (1)

[Claims] 1. A magnetic recording medium comprising at least a magnetic layer on a non-magnetic support, wherein the phosphoric acid or phosphite ester represented by the following general formula (1) or general formula (2) A magnetic recording medium, characterized in that a long-chain amine salt lubricant is coated on the magnetic layer. Embedded image Embedded image (Here, R ₁ is a hydrocarbon having 10 or more carbon atoms, R ₂ , R
_At least one of ₃ , R ₄ and R ₅ has 1 carbon atom
Shows 0 or more hydrocarbons, other than 1 has 20 or more carbon atoms
Up to hydrocarbons. )