JPH0995691A - Lubricant and magnetic recording medium using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a lubricant comprising a specific tryptophan ester compound, excellent in lubricity, its long period durability and environment protection, and capable of imparting good travelability, abrasion resistance and durability to magnetic recording media. SOLUTION: This lubricant comprises a compound of the formula (R1 -R3 are each a hydrocarbon group; R4 is H, a hydrocarbon group), e.g. 3-[ 2-(octadecyloxycarbonyl)-2-(N,N-dimethylamino)ethyl]indole. When the lubricant is used for a magnetic recording medium, the compound of the formula is coated on a magnetic layer in an amount of 0.5-100mg/m<2> , especially 1-20mg/m<2> , in a top coating process, or added into the magnetic layer in an amount of 0.5-20 pts.wt. per 100 pts.wt. of a binder in a process for adding the compound into the magnetic layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lubricant for a magnetic recording medium which has an excellent lubricating effect. The present invention also relates to a magnetic recording medium that retains this lubricant and has improved runnability, wear resistance, and durability.

[0002]

2. Description of the Related Art As a magnetic recording medium such as a magnetic tape or a magnetic disk, a magnetic paint prepared by dispersing and kneading a ferromagnetic powder, a binder and various additives with an organic solvent is coated on a non-magnetic support. A magnetic layer is formed by coating and drying.
A so-called coating type magnetic recording medium or a so-called metal thin film type magnetic recording medium in which a magnetic layer is formed by depositing a ferromagnetic metal material on a non-magnetic support by a method such as vapor deposition has been proposed. I have.

[0003] Of these, a magnetic recording medium of the metal magnetic thin film type has a very high smoothness on the surface of the magnetic layer, and therefore has a substantial contact area with a sliding member such as a magnetic head or a guide roller. Also becomes a large value.
For this reason, there is a problem in that a sticking phenomenon (so-called sticking) easily occurs with these sliding members during running and the running property and durability are poor. For example, when applied to an 8 mm video deck or a hard disk drive, the following problems occur.

First, a tape inserted into an 8 mm video deck is guided by ten or more guide pins and wound around a head drum. At this time, the tape tension and the tape running speed are kept constant by a pinch roller and a capstan. Usually, the tension is set to about 20 g and the running speed is set to 0.5 cm / s.

[0005] The running system has a structure in which the magnetic layer side of the tape is in contact with a guide pin made of stainless steel. In such a case, if the coefficient of friction between the surface of the magnetic layer of the tape and the guide pins is large, the tape causes stick-slip, a phenomenon called tape squealing, and the reproduced image becomes cramped.

Also, the relative speed between the tape and the head is very high, and the head slides at the same position on the tape at a high speed especially in a pause state. This causes a problem of abrasion of the magnetic layer and a resulting reduction in reproduction output. In the metal thin film type magnetic tape, the magnetic layer is very thin, so that the wear of the magnetic layer is very serious.

On the other hand, in a hard disk drive,
The SS (contact start / stop) method is adopted. In the CSS method, when the disk is stopped, the magnetic head is in contact with the disk. When the disk is rotated at a high speed at the time of startup, the magnetic head floats from the surface of the disk due to the airflow generated thereby, and recording is performed in this state Playback is performed. When the operation is stopped, the rotation of the disk is further reduced, whereby the magnetic head comes into contact with the disk again. CSS like this
In the method, at the time of startup, from the start of disk rotation until the magnetic head floats, and at the time of operation stop, from the time the magnetic head contacts the disk until the disk stops rotating, The magnetic head slides on the disk. At that time, friction between the magnetic head and the disk becomes a serious problem. C to maintain product level reliability
It is desirable that the friction coefficient after performing the SS operation 20,000 times is 0.5 or less. However, it is difficult for the metal thin film type magnetic disk to satisfy this condition as it is. Also,
Since the disk rotates at a high speed, the problem of head crash caused by the collision between the head and the disk is one of the problems to be solved in the metal thin film type magnetic recording medium.

[0008] In order to solve such problems, attempts have been made to suppress the friction coefficient by top-coating or internally adding various lubricants such as higher fatty acids and their esters. Has been made. However, the lubricant used in the magnetic recording medium is required to meet the following strict conditions, and in reality, no suitable lubricant has been found.

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, (2)
It can be applied very thinly because spacing with the magnetic head is a problem, and sufficient lubrication performance can be exhibited even in that case. (3) It can withstand long-time use and maintain the lubrication effect for a long time. , Etc. are required.

That is, as a lubricant for the magnetic recording medium,
Not only it has excellent lubrication performance, but it adheres evenly and firmly to the surface of the magnetic layer, and its lubrication performance can be maintained for a long period of 10 years or more. What can be applied as is ideal.

On the other hand, as the lubricant, a large number of compounds have been proposed so far, and they are roughly classified into three types, that is, a silicon type, a hydrocarbon type and a fluorinated carbon type.

First, the silicon-based lubricant is one of the commonly used lubricants in the coating type magnetic recording medium because of its good thermal stability and low vapor pressure. However, when used for a metal thin film type magnetic recording medium having a very good surface property, a silicon-based lubricant does not have sufficient lubrication performance.
It does not meet the durability specifications in the test. That is, it is difficult for the silicon-based lubricant to satisfy the lubrication characteristics required in the thin film type magnetic recording medium which is currently the mainstream.

Hydrocarbon-based lubricants are still the mainstream lubricants for coating type magnetic recording media. However, this hydrocarbon-based lubricant is generally inferior in thermal or chemical stability as compared with a silicon-based or fluorinated carbon-based lubricant. Therefore, friction causes the lubricant molecules to react,
Generates a frictional polymer. This frictional polymer is very troublesome, degrading lubricating properties and sometimes causing catastrophic failure. In addition, hydrocarbon lubricants have a high vapor pressure, which is one of the drawbacks. That is, the hydrocarbon-based lubricant exhibits excellent friction characteristics, but gradually evaporates due to its high vapor pressure.
For this reason, in a metal thin film type magnetic recording medium in which a lubricant is retained only by topcoating it on the surface, it is difficult to maintain the lubrication performance because the lubricant is not replenished if it evaporates from the surface. .

Fluorine-based lubricants are currently the most widely used lubricants in metal thin film type magnetic recording media. Among the fluorine-based lubricants, particularly, perfluoropolyether is widely used because of its better lubricating performance and surface protection effect as compared with other fluorine-based lubricants. The perfluoropolyether has such good properties because of the flexibility of the CF ₂ —O—CF ₂ ether bond, the viscosity is lower than that of perfluoroalkane of the same molecular weight, and over a wide temperature range. This is because the viscosity does not change. In addition, it must be chemically inert, have a low vapor pressure, have high thermal or chemical stability, have a low surface energy, have good boundary lubrication properties, and have a high water repellency. Etc. are mentioned as a feature.

The properties of the above-mentioned perfluoropolyether depend very strongly on its molecular structure. Currently, several types of perfluoropolyethers are commercially available, but they differ in molecular weight, main chain repeating units, and terminal groups.

[0016] For example, the product name Fom manufactured by Montecatini
Blin-Y is a random copolymer of CF (CF ₃ ) CF ₂ O and CF ₂ O, and the repeating unit of the main chain has a branched structure. In contrast, the company's product name is Fomb
Lin-Z is a homopolymer of CF ₂ CF ₂ O and CF ₂ O and has a linear structure. Product name Dem manufactured by Daikin Industries, Ltd.
Num and DuPont's trade name Krytox are homopolymers of hexafluoropropylene oxide and hexafluoroisopropylene oxide, respectively.

However, since the perfluoropolyether is non-polar, it has a drawback that it lacks the adsorption ability on the surface of the magnetic recording medium. As described above, the lubricant is applied on the magnetic layer to hold it. This is a difficulty in the magnetic recording medium of. Therefore, in order to improve the adsorptive power, as a perfluoropolyether having polar groups introduced at both ends, a product name Fomblin manufactured by Montecatini Co., Ltd.
Z-DOL (introducing a hydroxyl group as a polar group) and manufactured by the same company
The product name Fomblin AM2001 (introducing a piperonyl group as a polar group) has been developed. The perfluoropolyether introduced with these polar groups has a very strong immobilizing effect on the metal surface and the carbon surface, and when used as a lubricant, compared with unmodified perfluoropolyether, A large effect of reducing the friction coefficient is obtained, and the service life is improved.

As described above, various improvements have been made to the perfluoropolyether in order to improve the lubrication performance. But it still has problems that need to be resolved.

One of them is decomposition caused by friction between the medium and the magnetic head.

That is, in some magnetic recording systems, the relative velocity between the medium and the magnetic head exceeds several meters, and the frictional heat generated at the contact portion causes the temperature of the medium surface to increase rapidly, though instantaneously. is there. Although the temperature at the contact area has not yet been established as an accurate measurement method,
The calculated value is estimated to exceed several hundred degrees Celsius. Especially,
Under boundary lubrication conditions, such as in magnetic recording systems,
Since the reactive surface is exposed at the sliding portion, this is combined with the temperature rise at the above-mentioned contact point, thereby promoting 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, as well as AlCl ₃ and FeF.
Decomposition is promoted in the presence of a Lewis acid such as ₃ , Al ₂ O ₃ or a Lewis base. Such decomposition of the lubricant not only adversely affects the lubrication characteristics, but also results in impairing the reliability of the magnetic recording system.

Further, perfluoropolyether dissolves only in a fluorinated solvent such as CFC, which is a problem from the viewpoint of global environment protection.

As measures against this, perfluoropolyether type lubricants (soluble in hydrocarbon type solvents) in which perfluoropolyether groups are introduced into long-chain alkyl esters and perfluoropolyethers having a carboxyl group at the end are used. Amine salt compounds (soluble in alcoholic solvents) have been reported. However, although the lubricant having an ester group is excellent in still durability, it tends to have a relatively high coefficient of friction and cannot be said to be sufficient.

[0024]

As described above, the lubricant used for the magnetic recording medium has not only the lubricating performance but also the thermal or chemical stability, the adsorptivity with the medium surface, the kind of the solvent and the like. However, various requirements are required, but it is the current situation that the ones that completely satisfy these requirements cannot be realized.

Therefore, the present invention has been proposed in view of such a conventional situation, and it is possible to maintain excellent lubricity under various conditions of use and to maintain a lubricating effect for a long time. It is an object of the present invention to provide a magnetic recording medium that retains the lubricant and is excellent in running property, abrasion resistance and durability.

[0026]

Means for Solving the Problems As a result of extensive studies, the present inventors have found that the tryptophan ester compound represented by Chemical formula 3 has an excellent lubricating effect. Found that the magnetic recording medium in which this lubricant is retained exhibits excellent characteristics,
The present invention has been completed.

[0027]

Embedded image

That is, the lubricant according to the present invention has the above chemical formula
And a tryptophan ester compound represented by

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 a lubricant composed of the tryptophan ester compound represented by the above chemical formula 3 is retained. It has been done.

The tryptophan ester compound represented by the above chemical formula 3 has a high effect of reducing the friction coefficient and is good not only under normal temperature and normal humidity but also under severe environment such as high temperature and high humidity and low temperature and low humidity. Demonstrate lubrication performance. The tryptophan ester compound is also soluble in a non-fluorine-based solvent, for example, a hydrocarbon-based solvent such as hexane or toluene.

Here, the hydrocarbon group represented by R ₁ and R ₂ in Chemical formula 3 may have a linear structure or a branched structure, and may have an unsaturated structure or an aromatic ring. I do not care. Moreover, the kind of isomer does not matter. However, considering the ease of synthesis, it is desirable that the number of carbon atoms be 6 or less.

Further, R 3 in the chemical formula ₃ represents a hydrocarbon group having 6 or more carbon atoms, and this hydrocarbon group may have a linear structure or a branched structure, and may have an unsaturated structure or It may have an aromatic ring. Moreover, the kind of isomer does not matter. However, in consideration of the reduction of the friction coefficient and the solubility in the solvent, it is preferable that the structure has a linear or branched structure having 10 or more carbon atoms.

Further, R ₄ in Chemical formula 3 represents hydrogen or a hydrocarbon group. In particular, when R ₄ is a hydrocarbon group (hydrogen of amino group of indole ring is replaced with a hydrocarbon group), the lubricating effect is less likely to be deteriorated even by an acceleration test or the like, and the friction coefficient can be suppressed to be low. In this case, the hydrocarbon group may have a linear structure or a branched structure, and may have an unsaturated structure or an aromatic ring,
The type of isomer does not matter. However, considering the ease of synthesis, it is desirable that the number of carbon atoms be 6 or less.

The lubricant made of the tryptophan ester compound as described above is a metal thin film type magnetic recording medium,
It is applied to both coating type magnetic recording media.

The metal thin film type magnetic recording medium is formed by forming a metal magnetic thin film as a magnetic layer on a non-magnetic support.

Examples of the non-magnetic support include polyesters such as polyethylene terephthalate, polyolefins such as polyethylene and polypropylene, cellulose derivatives such as cellulose triacetate, cellulose diacetate and cellulose butyrate, polyvinyl chloride and polyvinylidene chloride. In addition to polymeric materials such as vinyl resins, polycarbonate, polyimide, polyamide, etc.,
Examples include light metals such as aluminum alloys and titanium alloys, and ceramics such as alumina glass. When a rigid substrate such as an aluminum alloy plate or a glass plate is used as the non-magnetic support, an oxide film such as alumite treatment or a Ni-P film is formed on the substrate surface to harden the surface. May be.

The metal magnetic thin film is made of a ferromagnetic metal material,
It is a continuous film formed by applying it on a nonmagnetic support by a technique such as plating, sputtering, or vacuum deposition.

As the metal magnetic thin film, Fe, Co,
Metals such as Ni, Co-Ni alloys, Co-Pt alloys,
Co-Pt-Ni based alloy, Fe-Co based alloy, Fe-N
i-based alloy, Fe-Co-Ni-based alloy, Fe-Ni-B-based alloy, Fe-Co-B-based alloy, Fe-Co-Ni-B-based alloy, etc., in-plane magnetization recording type metal magnetic thin film and C
An example is a perpendicular magnetic recording type metal magnetic thin film made of an o-Cr alloy or the like.

Of these, in the case of an in-plane magnetization recording type metal magnetic thin film, Bi, Sb, Pb,
A base layer of a low-melting non-magnetic material such as Sn, Ga, In, Ge, Si, and Ti is formed in advance, and a metal magnetic thin film is formed by vertically depositing or sputtering a metal magnetic material on the base layer. It is good to form. When a metal magnetic material is deposited on the underlayer, the low-melting nonmagnetic material of the underlayer diffuses into the metal magnetic thin film, the orientation of the metal magnetic thin film is eliminated, and in-plane isotropy is secured. And the coercivity is improved.

In order to retain the lubricant composed of the tryptophan ester compound on the metal magnetic thin film as described above, the tryptophan ester compound is dissolved in a hydrocarbon solvent such as hexane or toluene,
This may be top-coated on the metal magnetic thin film. At this time, the coating amount of the tryptophan ester-based compound was 0.
5-100 mg / m ² Is preferably 1 to 20
mg / m ² Is more preferable.

When the magnetic recording medium is used as a hard disk, a graphite-like, tire-mond-like or amorphous carbon film, chromium oxide film, SiO ₂ film, ZrO ₂ film, etc. are formed on the surface of the metal magnetic thin film. The hard protective film may be formed. However, when such a protective film is formed, a lubricant composed of a tryptophan ester compound is held on the protective film instead of the metal magnetic thin film. Also in this case, tryptophan ester compound is dissolved in a hydrocarbon solvent,
This may be top-coated on the protective film. The coating amount may be the same as when it is held on the metal magnetic thin film.

On the other hand, the coating type magnetic recording medium comprises a non-magnetic support and a magnetic coating mainly composed of a ferromagnetic powder and a binder is formed as a magnetic layer on the non-magnetic support.

As the non-magnetic support, any of those exemplified for the magnetic recording medium of metal magnetic thin film can be used.

The magnetic layer is formed by dispersing and kneading at least a ferromagnetic powder and a binder together with an organic solvent to prepare a magnetic coating material, coating the magnetic coating material on a non-magnetic support and drying.

The ferromagnetic powder may be an oxide magnetic powder or a metal magnetic powder. Examples of the oxide magnetic powder include γ-Fe ₂ O ₃ and Co-containing γ-Fe ₂ O ₃ , F.
e ₃ O ₄ , Co-containing γ-Fe ₃ O ₄ , Co-deposited-Fe ₃
Examples include O ₄ and CrO ₂ . Further, as the magnetic metal powder, Fe, Co, Ni, Fe-Co, Fe-Ni,
Fe-Co-Ni, Co-Ni, Fe-Co-B, Fe
—Co—Cr—B, Mn—Bi, Mn—Al, Fe—C
O-V, etc., and further, for the purpose of improving these various characteristics, Al, Si, Ti, Cr, Mn, Cu, Z.
A metal component such as n may be added. Further, hexagonal ferrite such as barium ferrite and iron nitride can be used.

As the binder, an organic binder such as vinyl copolymer, polyester polyurethane, polycarbonate polyurethane, nitrocellulose or the like can be used.

In order to retain the above-mentioned tryptophan ester-based compound in such a magnetic layer, the tryptophan ester-based compound may be dissolved in a solvent as described above, and this may be top-coated on the magnetic layer. The compound may be directly internally added to the magnetic layer. In order to internally add the tryptophan ester compound to the magnetic layer, a lubricant composed of this tryptophan ester compound may be mixed with another coating composition at the stage of preparing the magnetic coating material. At this time, the ratio of the lubricant is
0.5 to 20 parts by weight is suitable for 100 parts by weight of the binder.

In this magnetic layer, if necessary, in addition to a lubricant made of a tryptophan ester compound, an additive usually used in this type of magnetic recording medium, such as an abrasive or an antistatic agent, is used. There is no problem even if it is added by adding.

As described above, in the present invention, the magnetic layer is made to hold a lubricant composed of a tryptophan ester compound, but this lubricant is used alone, and a known lubricant conventionally used in magnetic recording media is used. It may be used in combination with.

Further, the lubricant composed of the tryptophan ester compound may be used in combination with the extreme pressure agent so that the lubricating effect is maintained even under more severe conditions.

The extreme pressure agent reacts with a metal surface by frictional heat generated when a metal contact is partially generated in the boundary lubrication region to form a reaction product film. This prevents friction and wear. As the extreme pressure agent, any of a phosphorus extreme pressure agent, a sulfur extreme pressure agent, a halogen extreme pressure agent, an organometallic extreme pressure agent, a composite extreme pressure agent, and the like can be used. The mixing ratio of lubricant and extreme pressure agent is 3
About 0:70 to 70:30 (weight ratio) is suitable.

In addition to these, a rust preventive can be used in combination.
As the rust preventive, any of those used in this kind of magnetic recording medium can be used, and examples thereof include phenols, naphthols, quinones, nitrogen atom-containing heterocyclic compounds, oxygen atom-containing heterocyclic compounds, and sulfur atoms. Examples include contained heterocyclic compounds.

Although the basic structure of the magnetic recording medium to which this lubricant is applied has been described above, the structure of the medium is not limited to this. There may be no problem in providing additional elements that are usually employed for the purpose of improving characteristics.

For example, a back coat layer is provided on the surface of the non-magnetic support opposite to the surface on which the magnetic layer is formed, or under the magnetic layer for the purpose of controlling the surface property of the magnetic layer. An undercoat layer may be formed on the side.

Of these, the back coat layer is a layer in which fine carbon powder for imparting conductivity to the resin binder exemplified above for the magnetic coating film and an inorganic pigment for controlling the surface roughness are dispersed. And is provided to improve the running property of the medium. The back coat layer may be retained by internally adding or top-coating the lubricant made of the tryptophan ester compound.

[0056]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described, but it goes without saying that the present invention is not limited to these embodiments.

First, in the general formula of Chemical formula 4, R _{1 to} R ₄
Was prepared from a tryptophan ester compound having the structure shown in Table 1 [compound (1) to compound (10)].

[0058]

Embedded image

[0059]

[Table 1]

For example, to synthesize the compound (2), commercially available tryptophan and stearyl alcohol are put into anhydrous toluene, p-TsOH is added in a catalytic amount, and the mixture is heated and stirred. Then, after removing the produced water and reacting for 5 hours, the product is taken out into water and the precipitate is filtered to obtain a stearyl ester of tryptophan. Furthermore, after purification by the recrystallization method, using dimethyl sulfate, hydrogen of the amino group at the α-position in tryptophan,
The hydrogen of the amino group of the indole ring may be replaced with a methyl group.

Example 1 In this example, a magnetic tape made of the above-mentioned compound (1) was applied to a magnetic layer made of a metal magnetic thin film.

Specifically, first, Co was deposited on a polyethylene terephthalate (hereinafter referred to as PET) film having a thickness of 10 μm by the oblique vapor deposition method to give a film thickness of 200.
A metal magnetic thin film of nm was formed.

Next, a lubricant coating prepared by dissolving the compound (1) in hexane was applied to the surface of the metal magnetic thin film,
A sample tape was produced by cutting into a millimeter width. The amount of lubricant applied was 5 mg / m ² .

Examples 2 to 10 In Examples 2 to 10, sample tapes were prepared in the same manner as in Example 1 except that the compounds (2) to (10) were used instead of the compound (1). Was produced.

Comparative Example 1 Instead of the compound (1), a perfluoropolyether having a hydroxyl group at the terminal (manufactured by Montecatini, trade name Fom
A sample tape was prepared in the same manner as in Example 1 except that blin Z-DOL) was used.

Comparative Example 2 A sample tape was prepared in the same manner as in Example 1 except that perfluoropolyether having a carboxyl group at the terminal (Fomblin Z-DIEC, trade name, manufactured by Montecatini) was used in place of the compound (1). Was produced.

Example 11 In this example, a magnetic tape mainly made of magnetic powder and a binder was internally added with a lubricant composed of the compound (1) to prepare a magnetic tape.

Specifically, first, each magnetic coating composition was weighed out according to the following composition and mixed in a ball mill for 24 hours.

Magnetic coating composition Metal powder Magnetic powder 100 parts by weight Vinyl chloride / vinyl acetate copolymer 10.5 parts by weight Polyurethane resin 10.5 parts by weight Carbon (antistatic agent) 5 parts by weight Methyl ethyl ketone 150 parts by weight Cyclohexanone 150 parts by weight After filtering the obtained mixture through a filter, 4 parts by weight of Coronate L (manufactured by Nippon Polyurethane Company, trade name polyisocyanate) as a curing agent and 1% by weight of the above-mentioned compound (1) dissolved in toluene were used as 3 parts. A magnetic coating material was prepared by adding 30 parts by weight and stirring for 30 minutes.

Then, this magnetic paint was applied to a P coating having a thickness of 12 μm.
A sample tape was prepared by applying the composition on an ET film so that the thickness after drying was 2 μm, performing magnetic field orientation treatment, drying, winding, and calendering, and then cutting into 8 mm width.

Example 12 to Example 20 In Example 12 to Example 20, sample tapes were prepared in the same manner as in Example 11 except that the compounds (2) to (10) were used instead of the compound (1). Was produced.

Example 21 In this example, a magnetic tape mainly made of magnetic powder and a binder was coated with a lubricant containing the above-mentioned compound (1) to prepare a magnetic tape.

Specifically, first, 2 parts by weight of butyl stearate and 2 parts by weight of myristic acid were added to a magnetic coating composition having the same composition as shown in Example 11, and then, as in Example 11. Similarly, after mixing with a ball mill and filtering with a filter, a curing agent was added and stirred for 30 minutes to prepare a magnetic paint. Then, as in Example 11, this magnetic coating material was applied onto a PET film having a thickness of 12 μm so that the thickness after drying was 2 μm, magnetic field orientation treatment, drying, winding, and calendering treatment were performed, and then the compound ( 2 mg of 1) dissolved in toluene
/ M ² and then cut into 8 mm width to prepare a sample tape.

Example 22 to Example 30 In Example 22 to Example 30, sample tapes were prepared in the same manner as in Example 21 except that compounds (2) to (10) were used instead of compound (1). Was produced.

Comparative Example 3 A sample tape was prepared in the same manner as in Example 11 except that the compound (1) was not applied.

Evaluation of Characteristics As described above, Examples 1 to 30 and Comparative Examples 1 to 1
For the sample tape produced in Comparative Example 3, α,
The friction coefficient, the still durability and the shuttle durability were examined under the three conditions of β and γ. Table 2 shows the conditions for α, β, γ
Table 3 to Table 5 show the measurement results under the respective conditions.

The still durability was evaluated by measuring the time taken for the output in the pause state to decay to -3 dB.

The shuttle durability was evaluated by performing the shuttle running for 2 minutes each time a plurality of times and measuring the number of times until the output decreased by 3 dB.

[0079]

[Table 2]

[0080]

[Table 3]

[0081]

[Table 4]

[0082]

[Table 5]

As shown in Tables 3 to 5, the sample tapes of Examples 1 to 30 using the lubricant composed of the tryptophan ester compound were prepared by coating the metal magnetic thin film with these lubricants, and Any type of magnetic powder mainly composed of powder and binder with these lubricants internally added, magnetic layer mainly composed of magnetic powder and binder with these lubricants applied, The friction coefficient was low even under the measurement environment of, and still durability and shuttle durability were also very good.

Further, the measurement results of the sample tapes of Examples 1 to 10 in which a lubricant composed of a tryptophan ester compound was applied on the metal magnetic thin film, and a hydroxyl group was added to the terminal instead of the tryptophan ester compound. The sample tape of Comparative Example 1 using the perfluoropolyether having the same and the measurement result (shown in Table 3) of the sample tape of Comparative Example 2 using the perfluoropolyether having a terminal carboxyl group were compared. However, it can be seen that the sample tapes of Comparative Examples 1 and 2 have a higher friction coefficient, and the still durability and the shuttle durability are deteriorated especially under the high temperature and high humidity environment and the low temperature environment.

Further, these lubricants were used in comparison with the sample tapes of Examples 21 to 30 in which the lubricant composed of the tryptophan ester compound was applied to the magnetic layer mainly composed of the magnetic powder and the binder. The sample tape of Comparative Example 3 having the same configuration except that it was not applied,
In particular, still durability and shuttle durability are deteriorated in a low temperature environment.

From the above, it was found that the lubricant composed of the tryptophan ester compound according to the present invention is superior in lubrication performance as compared with the lubricant having the perfluoropolyether structure.

Next, Examples 1 to 30 and Comparative Example 1
-The sample tape prepared in Comparative Example 3 was stored under condition β (temperature 40 ° C, relative humidity 80%) for 7 days,
The situation of stick-slip and drop-out before and after that was compared.

The stick-slip was judged as an index whether or not the static friction coefficient during friction exceeds 0.6. When exceeding, it was recorded as "x", and when not exceeding, was recorded as "○".

For dropout, run for 3 minutes continuously,
At that time, it was evaluated by measuring the number of times that the output decrease of 10 dB or more continued for 3 μsec.

The coefficient of friction and stick-slip,
The condition of occurrence of dropout is condition α (temperature 25
It was measured under a temperature of 60 ° C. and a relative humidity of 60%. The measurement results before and after storage are shown in Tables 6 to 8.

[0091]

[Table 6]

[0092]

[Table 7]

[0093]

[Table 8]

As shown in Tables 6 to 8, the sample tapes of Examples 1 to 30 using the tryptophan ester compound as the lubricant show that stick-slip and dropout are almost increased by storage. It is kept low. On the other hand, Comparative Example 1 using perfluoropolyether having a hydroxyl group at the terminal
The sample tape of Comparative Example 2 and the sample tape of Comparative Example 2 using the perfluoropolyether having a carboxyl group at the end are apt to cause stick-slip upon storage. From this, the lubricant comprising the tryptophan ester compound according to the present invention is superior in lubrication performance to other lubricants having a perfluoropolyether structure, and the lubrication performance thereof is, for example, stored under high temperature and high humidity conditions. It was found to be very stable without deterioration even after the application.

[0095]

As is clear from the above description, the lubricant according to the present invention maintains excellent lubricity under various conditions of use and can maintain the lubrication effect for a long time. Therefore, the magnetic recording medium of the present invention holding this lubricant can have good running properties, wear resistance, and durability under various usage environments.

Further, the lubricant made of this tryptophan ester compound is soluble in a hydrocarbon solvent such as hexane, and it is not necessary to use a fluorine solvent, so that it is very preferable from the viewpoint of protecting the global environment. Is.

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Claims (4)

[Claims] 1. A lubricant comprising a tryptophan ester compound represented by Chemical formula 1. Embedded image 2. A magnetic recording medium having at least a magnetic layer on a non-magnetic support, wherein a lubricant composed of a tryptophan ester compound represented by Chemical formula 2 is retained. . Embedded image 3. The magnetic recording medium according to claim 2, wherein the magnetic layer is formed of a metal magnetic thin film, and the lubricant is applied to the magnetic layer. 4. The magnetic recording medium according to claim 2, wherein the magnetic layer is mainly composed of a magnetic powder and a binder, and the lubricant is applied to or internally added to the magnetic layer.