JP2745564B2 - Magnetic recording media - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic recording medium such as a magnetic tape and a magnetic disk, and more particularly to a lubricant.

[Conventional technology]

Conventionally, as a magnetic recording medium, γ
-Fe ₂ O ₃ , Co-containing Fe ₃ O ₄ , Co-containing γ-Fe
₂ O ₃ , a beltride compound of γ-Fe ₂ O ₃ and Fe ₃ O ₄ , Fe
₃ O _4, berthollide compound containing Co, oxides such as CoO ₂ ferromagnetic powder or Fe, Co, powdered magnetic material of vinyl chloride alloy magnetic powder mainly composed of Ni or the like - vinyl acetate copolymerization A coating type magnetic recording medium produced by applying and drying a magnetic coating material dispersed in an organic binder such as a coalesced resin, a polyester resin, and a polyurethane resin is widely used.

On the other hand, as the demand for high-density magnetic recording has increased, ferromagnetic metal materials such as Co-Ni alloys have been converted to polyester by plating or vacuum thin film forming technology (vacuum evaporation, sputtering, ion plating, etc.). A so-called ferromagnetic metal thin-film type magnetic recording medium directly attached on a non-magnetic support such as a film or a polyimide film has been proposed and attracts attention. This ferromagnetic metal thin film type magnetic recording medium is excellent in coercive force, squareness ratio, etc., is excellent in electromagnetic conversion characteristics at short wavelengths, and is capable of extremely thin magnetic layer, so that recording demagnetization is possible. In addition, there are many advantages, such as that the thickness loss at the time of reproduction is extremely small and that the packing density of the magnetic material can be increased because it is not necessary to mix an organic binder which is a specific magnetic material in the magnetic layer.

However, in the above-described ferromagnetic metal thin film type magnetic recording medium, since the surface smoothness of the magnetic layer is extremely good, the substantial contact area becomes large, so that the adhesion phenomenon (so-called sticking) is likely to occur or the friction is increased. There are many drawbacks in durability, running properties, etc., such as an increase in the coefficient, and the improvement thereof has been a major issue. Generally, a magnetic recording medium is subjected to a high-speed relative motion with a magnetic head in the process of recording / reproducing a magnetic signal, and at that time, the running must be performed in a smooth and stable state. Further, it is preferable that wear and damage due to contact with the magnetic head be as small as possible.

Thus, for example, attempts have been made to improve the durability and running properties by applying a lubricant on the magnetic layer of the magnetic recording medium to form a protective film.

[Problems to be solved by the invention]

By the way, when a protective film is formed by applying a lubricant as described above, it is required that the protective film exhibit good adhesion to the magnetic layer and exhibit a high lubricating effect. In the case of the above-mentioned ferromagnetic metal thin film type magnetic recording medium, at first, the friction coefficient is reduced and the running property is improved. However, since the adhesive force of the lubricant to the ferromagnetic metal thin film is weak, the lubrication is gradually increased. The agent is scraped off by a magnetic head or the like, and the effect is rapidly reduced.

In addition, these adhesiveness and lubricating effect must be excellent even in places where temperature conditions are severe, such as in tropical, subtropical and cold regions.

However, the working temperature range of the conventionally widely used lubricant is limited, and the properties at high and low temperatures are poor as compared with normal temperature, and particularly, the lubricant solidifies or freezes at a low temperature such as 0 to -5 ° C. There are many things. Therefore, a sufficient lubricating effect could not be exerted.

On the other hand, when an attempt is made to internally add a lubricant such as perfluoropolyether to the magnetic layer in a coating type magnetic recording medium,
A general-purpose solvent cannot be used, and further, for example, since the compatibility between the binder and the lubricant is poor, the characteristics of the lubricant cannot be fully utilized.

Therefore, the present invention provides a lubricant that maintains adhesion and lubricity under any use conditions and maintains a lubricating effect for a long period of time, and provides a magnetic recording medium excellent in running properties and durability. It is the purpose.

[Means for solving the problem]

The present inventors have intensively studied to achieve the above-mentioned object, and as a result, have found that a lubricant containing a perfluoropolyether ester of carboxylic acid is suitable for this purpose, and have completed the present invention. It has been reached.

That is, the present invention is characterized in that in a magnetic recording medium in which a magnetic layer is formed on a nonmagnetic support, a perfluoropolyether ester of a long-chain alkyl carboxylic acid or an aromatic carboxylic acid is held as a lubricant. It is assumed that.

Here, the perfluoropolyetherester of carboxylic acid used as a lubricant in the present invention is, for example, a compound represented by the general formula RfOOCR) _n (1) ΦCOOCH ₂ Rf) _L (2) Φ-COOCH ₂ Rf ′ CH ₂ OOC-Φ (3) OOC-Φ-COOCH ₂ Rf′-CH _{2 m} (4)

Here, Φ in the formula is a hydrocarbon-based aromatic ring such as a benzene ring and a naphthalene ring, and may be a compound having a heterocyclic ring. Further, it may contain a halogen, a nitro group, a cyano group, an alkyl group or the like as a substituent of the aromatic ring. On the other hand, R represents an alkyl group, particularly preferably a long-chain alkyl group having 11 or more carbon atoms. n and l are natural numbers of 1 or more and 6 or less, and m is a natural number of 2 or more.

Rf and Rf 'in the above formula are perfluoropolyether groups. For example, Rf is a general formula FCF ₂ CF ₂ CF ₂ O _a CF ₂ CF ₂ −... (5), a general formula —CF ₂ OCF (CF ₃ ) CF _{2 b} OCF ₂ OCF ₂ −. formula _{-CF 2 OC 2 F 4 O e} CF 2 O f CF 2 - is represented by ... (7).

Further, for example, Rf 'is the general formula _{-CF 2 OCF (CF 3) CF} 2 b OCF 2 OCF 2 - ...... (8) or the general formula _{-CF 2 OC 2 F 4 O e} CF 2 O f CF 2 - ... .. (9) Where a, b, c, d, e, and f are 10
It is preferably a natural number in the range of 500 to 500. Of course, it is not limited to these as long as it is a perfluoropolyether.

The magnetic recording medium to which the present invention is applied can be roughly classified into a metal thin film type and a coating type, and as a method for holding the perfluoropolyetherester of the carboxylic acid in such a metal thin film type magnetic recording medium, There is a method of top-coating the surface of a metal magnetic thin film. When the top coat is applied, as a method for applying the solution, a solution obtained by dissolving the carboxylic acid in a perfluoropolyether ester solvent is applied (eg, spin-coated) or sprayed,
Alternatively, the magnetic recording medium may be immersed in this solution.

When the perfluoropolyetherester of the carboxylic acid is top-coated on the surface of the metal magnetic thin film, the coating amount is preferably 0.5 to 100 mg / m2, and 1 to ²⁰ m / m2.
More preferably, it is g / m ² . If the coating amount is less than 0.5 mg / m ² , the effects of the present invention such as a decrease in friction coefficient, abrasion resistance, and improvement in durability do not appear, while if it is more than 100 mg / m ² , the sliding member and the ferromagnetic metal A sticking phenomenon occurs between the film and the thin film, and the running property is rather deteriorated.

The metal magnetic thin film, which is a magnetic layer, is formed as a continuous film by a PVD technique such as plating, sputtering, or vacuum deposition, and is made of a metal such as Fe, Co, Ni, a Co-Ni alloy, or a Co-Ni alloy.
Pt alloy, Co-Ni-Pt alloy, Fe-Co alloy, Fe-Ni alloy, Fe-Co-Ni alloy, Fe-Ni-B alloy, Fe-Co-
Examples are an in-plane magnetization recording metal magnetic thin film made of a B-based alloy, an Fe-Co-Ni-B-based alloy, and a perpendicular magnetization recording metal magnetic thin film such as a Co-Cr-based alloy thin film and a Co-O-based thin film.

In particular, in the case of an in-plane magnetized recording metal magnetic thin film, a base film of a low-melting nonmagnetic material such as Bi, Sb, Pb, Sn, Ga, In, Ge, Si, or Tl is formed on a nonmagnetic support in advance. Each metal magnetic material is deposited or sputtered from the vertical direction to diffuse these low-melting non-magnetic materials into the magnetic metal thin film, thereby eliminating orientation and ensuring in-plane isotropy and improving coercive force. You may do so.

When a hard disk as described above is used, a hard protective film such as a carbon film, a diamond thin film, a chromium oxide film, and an SiO ₂ film may be formed on the surface of the metal magnetic thin film.

On the other hand, as a method of retaining the perfluoropolyetherester of the carboxylic acid in a coating type magnetic recording medium, a method of internally adding the carboxylic acid to a magnetic coating film, a method of topcoating the surface of a magnetic layer, or a combination of both methods Etc.

At this time, since the conventional lubricant does not dissolve in general-purpose solvents,
For example, a lubricant is dissolved in a freon-based solvent and internally added or top-coated. However, in the present invention, since the perfluoropolyether ester of a carboxylic acid is soluble in an alcohol-based solvent, a magnetic paint is used without using a Freon-based solvent and using the perfluoropolyether ester of the carboxylic acid as a lubricant. It is possible to add internally or top coat the surface of the magnetic layer.

Here, when the perfluoropolyether ester of the carboxylic acid is internally added to the magnetic layer, an amount equivalent to a conventional lubricant is added, for example, 0.2 to 20 parts by weight based on 100 parts by weight of the resin engaging agent. Parts.

It is also the case of top coat a perfluoropolyether ester of the carboxylic acid on the surface of the magnetic layer may be coated with an amount equivalent to conventional lubricants, e.g., the coating weight is 0.5 to 100 mg / m ² Is preferred, and 1 to 20 mg /
m ² is more preferable.

The coating type magnetic layer may also be applied by a conventionally known method using a conventionally known magnetic material.

Accordingly, usable ferromagnetic powders include ferromagnetic iron oxide particles, ferromagnetic chromium dioxide, ferromagnetic alloy powder, hexagonal barium ferrite fine particles, iron nitride and the like.

When the ferromagnetic iron oxide particles are represented by the general formula FeOx, those having a value of x in the range of 1.33 ≦ x ≦ 1.50, that is, maghemite (γ-Fe ₂ O ₃ , x = 1.50), magnetite (F
e ₃ O ₄ , x = 1.33) and their solid solutions (FeOx, 1.33 <x <
1.50). Cobalt may be added to these ferromagnetic iron oxides for the purpose of increasing coercive force. Cobalt-containing iron oxides are roughly classified into two types: a doped type and an adhered type.

Examples of the ferromagnetic chromium dioxide include CoO ₂ or Ru, Sn, Te, Sb, Fe, Ti, V, Mn for the purpose of improving coercive force.
And the like to which at least one of them is added can be used.

As ferromagnetic alloy powders, Fe, Co, Ni, Fe-Co, Fe-Ni, F
e-Co-Ni, Co-Ni, Fe-Co-B, Fe-Co-Co-B, Mn-Bi, Mn
-Al, Fe-Co-V or the like can be used, and a metal component such as Al, Si, Ti, Cr, Mn, Cu, Zn or the like may be added thereto for the purpose of improving various characteristics.

The above-mentioned perfluoropolyether ester of carboxylic acid may be used alone as a lubricant for a magnetic recording medium, or may be used in combination with a conventionally known lubricant.
Alternatively, a perfluoroalkyl carboxylic acid ester,
It is also possible to use in combination with carboxylic acid perfluoroalkylamide, perfluoroalkylcarboxylic acid perfluoroalkylamide, or a derivative thereof.

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

The extreme pressure agent reacts with the metal surface due to the frictional heat generated when partial metal contact occurs in the boundary lubrication region, and performs a friction / wear prevention effect by forming a reaction product film. Any of phosphorus-based extreme-pressure agents, sulfur-based extreme-pressure agents, halogen-based extreme-pressure agents, organometallic-based extreme-pressure agents, and complex-type extreme-pressure agents can be used.

Further, in addition to the above-mentioned lubricant and extreme pressure agent, a rust preventive may be used in combination as needed.

As the rust inhibitor, any one which is usually used as a rust inhibitor for this type of magnetic recording medium can be used, for example, phenols, naphthols, quinones, heterocyclic compounds containing a nitrogen atom, oxygen atoms And heterocyclic compounds containing a sulfur atom.

The rust inhibitor may be used as a mixture with a lubricant containing the perfluoropolyether ester of the carboxylic acid, but the lubricant layer is applied after the rust inhibitor layer is applied. The effect is high if they are applied separately. When applied in this manner divided into two layers is preferably The coating amount of the rust inhibitor is a previous lubricant similar 0.5 to 100 mg / m ^2, in the range of 1 to 20 mg / m ² Is more preferred. Is less than the amount of coating is 0.5 mg / m ^2, insufficient effect of corrosion resistance improvement, conversely
If the amount is more than 100 mg / m ² , there will be a problem in running property and the like.

Further, in the magnetic recording medium of the present invention, a back coat layer, an undercoat layer, and the like may be formed as necessary in addition to the magnetic layer.

For example, the back coat layer is formed by adding a carbon-based fine powder for imparting conductivity to a resin binder or an inorganic pigment for controlling surface roughness to be applied.

The perfluoropolyether ester of the carboxylic acid of the present invention can be added to the back coat layer as a lubricant internally or by a top coat.
Alternatively, various combinations such as internal addition of the above-mentioned carboxylic acid perfluoropolyether ester as a lubricant and top coating to both the magnetic layer and the back coat layer are also possible.

In the metal thin film and the coating type magnetic recording medium, the non-magnetic support may be any of conventionally known ones, and is not limited at all.

For example, as the non-magnetic support, a polymer support formed of a polymer material represented by polyesters, polyolefins, cellulose derivatives, vinyl resins, polyimides, polyamides, polycarbonates and the like And a metal substrate made of an aluminum alloy, a titanium alloy or the like, a ceramic substrate made of alumina glass or the like, a glass substrate, or the like. The shape is not limited at all, and may be any shape such as a tape shape, a sheet shape, and a drum shape. Further, the non-magnetic support
In order to control the surface properties, the surface may be subjected to a surface treatment for forming fine irregularities.

Here, when a rigid substrate such as an Al alloy plate or a glass plate is used for the non-magnetic support, an oxide film such as alumite treatment or a Ni-P film is formed on the substrate surface, and the surface is hardened. You may make it.

[Action]

Perfluoropolyetheresters of carboxylic acids are
It has high water repellency and has an excellent effect of lowering surface energy. Particularly, the bifunctional (terephthalic acid) lubricant has a remarkable decrease in the surface energy, and the surface energy of the magnetic layer is 44 mJ / m ² when the lubricant of the present invention is not used. When an agent is used, it can be reduced to 10 to 13 mJ / m ² . This value is smaller than the value of fluorine resin such as Teflon, and contributes to the reduction of the coefficient of friction.
Exhibits excellent lubrication.

Further, the perfluoropolyether ester of carboxylic acid has higher solubility than that of perfluoropolyether alone, and is soluble in various hydrocarbon solvents (eg, n-hexane, petroleum ether, etc.) and alcohol solvents. Thus, it is not necessary to use a freon-based solvent.

At the same time, the durability is not impaired even under severe conditions such as high temperature, high humidity and low temperature.

In the perfluoropolyether ester of carboxylic acid, the terminal of the perfluoropolyether is an alcohol, which forms an ester bond with the carboxylic acid having a benzene ring. Prevent change. On the other hand, perfluorocarboxylic acid esters are ester compounds of carboxylic acid at the end of perfluoropolyether, and these compounds (that is, carboxylic acid bonded to perfluoroalkyl group)
Is a strong acid due to the electron-withdrawing property of fluorine, is very easily hydrolyzed, and degrades with time. Therefore, an instantaneous clock is likely to occur.

〔Example〕

Hereinafter, specific examples of the present invention will be described,
It goes without saying that the present invention is not limited to this embodiment.

In the following examples, the present invention was applied to vapor deposition type and coating type magnetic recording media, and the characteristics thereof were evaluated. Therefore, first, a method for manufacturing each magnetic recording medium will be described. The manufactured magnetic recording media were a deposition type magnetic tape, a hard disk, and a coating type magnetic tape.

<Production method of vapor-deposited magnetic tape> Co was applied to a 14 μm-thick polyethylene terephthalate film by oblique vapor deposition to form a ferromagnetic metal thin film having a thickness of 1000 mm.

Next, the amount of perfluoropolyetherester of carboxylic acid applied as a lubricant on the surface of the ferromagnetic metal thin film is reduced.
5 mg / m ² was applied and cut into 1/2 inch width to prepare a sample tape <Hard disk manufacturing method> Al with a 15 μm thick Ni-O plating layer formed as a non-magnetic metal base layer -Easy to use Mg alloy substrate (thickness 1.5mm, outer diameter 95mm, inner diameter 25mm), pressure 1x on this non-magnetic metal base layer
Bi was deposited by electron beam evaporation under the conditions of 10 ^-5 Torr and a substrate temperature of 150 ° C. to form a low-melting metal underlayer having a thickness of 200 °.

Next, a pressure of 1 × 10
Co was deposited by electron beam evaporation at a temperature of ^-5 Torr and a substrate temperature of 150 ° C. to form a metal magnetic thin film having a thickness of 1000 Å, and a carbon protective film was formed on the metal magnetic thin film by vacuum evaporation.

Finally, a perfluoropolyether ester of carboxylic acid was applied as a lubricant on the surface of the carbon protective film to prepare a sample hard disk.

<Production method of coated magnetic tape> Co-coated γ-Fe ₂ O ₃ 100 parts by weight Vinyl chloride-vinyl acetate copolymer 10.5 parts by weight (UCC, VAGH) Polyurethane resin 10.5 parts by weight (Nippon Polyurethanes, M-5033) Carbon (antistatic agent) 5 parts by weight Lecithin (dispersant) 1 part by weight Methyl ethyl ketone 150 parts by weight Methyl isobutyl ketone 150 parts by weight The above composition was used as a basic composition, and carboxylic acid was used as a lubricant in the basic composition. Was mixed with a ball mill for 24 hours and then taken out through a filter. Further, 4 parts by weight of a curing agent was added, followed by stirring for 30 minutes.

This magnetic paint was applied on a polyethylene terephthalate base having a thickness of 12 μm so that the thickness after drying became 5 μm, and after orientation in a magnetic field, dried and wound up. This was calendered and then cut into 1/2 inch widths to produce sample tapes.

In the present embodiment, as specific examples of the perfluoropolyether ester of the carboxylic acid, a perfluoropolyether ester of a long-chain alkyl carboxylic acid (perfluoropolyether having a long-chain alkyl group) and an aromatic carboxylic acid Perfluoropolyether ester of acid (perfluoropolyether having aromatic ring ester)
Were used.

These perfluoropolyetheresters of carboxylic acids are synthesized as follows.

Here, t represents a natural number, R represents a long-chain alkyl group or a hydrocarbon group having an aromatic ring, and Rf represents a perfluoropolyether. That is, the compound can be easily synthesized by reacting a perfluoropolyether having at least one hydroxyl group with carboxylic acid chloride. The by-product HCl is neutralized by adding a base such as pyridine and triethylamine.

The ester synthesized above can be purified by vacuum distillation or column chromatography.

Specific synthetic methods, for example as a perfluoropolyether Rf, formula _{-CH 2 -CF 2 O- (C 2} F 4 O s CF 2 O z CF 2 -CH 2 - ...... (11) ( where Where s and z represent natural numbers.), 2 equivalents of linolenic chloride were added dropwise in the presence of 2 equivalents of triethylamine. After washing and purification by column chromatography, the eluate is n-hexane.

According to the above synthesis method, nine types of compounds (Compound 1 to Compound 9) were synthesized by changing the types of the long-chain alkyl group and the perfluoropolyether group. Table 1 shows the synthesized compounds.

Above (shown in FIG. 1.) Infrared absorption spectrum of Compound 1 of Table 1 in view the 3000 cm ^-1 to the double bond of CH stretching vibration and stretching vibration of CH bond was observed at 2930,2850Cm ^-1 That the stretching vibration of the carbonyl group is at 1760 cm ^-1 , 1320
The compound 1 can be identified from the fact that there is a large stretching vibration of CF in the range of 1601160 cm ⁻¹ .

Similarly, nine kinds of perfluoropolyethers having an aromatic ring ester (compounds 10 to 18) were synthesized.

Table 2 shows the synthesized perfluoropolyethers having an aromatic ring ester.

In the table, Rf and Rf ′ represent perfluoropolyether groups, Rf is a general formula —CF ₂ CF ₂ OCF ₂ CF ₂ CF _{2 g} F (12), and Rf ′ is a general formula —CF ₂ O (C ₂ F ₄ O _h (CF ₂ O _i CF ₂ −) (13) where g, h, and i are natural numbers of 10 to 500.

The following magnetic recording media were produced using the compounds shown in Tables 1 and 2 above.

 First, an evaporation type sample tape was manufactured.

Examples 1 to 18 As Examples 1 to 18, the perfluoropolyether ester of carboxylic acid in the method for producing a vapor-deposited magnetic tape was referred to as Compound 1 to Compound 18 shown in Tables 1 and 2. Then, a sample tape was prepared. Here, in Examples 1 to 9, the perfluoropolyether having the long-chain alkyl ester was used as a lubricant.
Examples 10 to 18 use perfluoropolyether having an aromatic ester as a lubricant.

Comparative Example A and Comparative Example B As Comparative Example A and Comparative Example B, sample tapes were prepared using the perfluoropolyether ester of carboxylic acid as the compound A and the compound B shown in Table 3 in the above-described method of producing a vapor-deposited magnetic tape. did.

Note that x and y in Table 3 represent natural numbers.

Comparative Example C As Comparative Example C, a sample tape to which no lubricant was applied was also manufactured.

For each of the sample tapes of Examples 1 to 18 and Comparative Examples A to C produced as described above,
℃, relative humidity (RH) 30%, temperature 25 ° C, relative humidity (RH) 60
%, And a coefficient of friction, a still durability, and a shuttle durability under each condition of a temperature of −5 ° C. were measured. The coefficient of friction was measured by using a guide pin made of stainless steel (SUS304) and feeding the material at a constant tension and at a speed of 5 mm / sec. For still durability, the decay time until the output decreased by 3 dB in the pause state was evaluated. Shuttle durability is as follows: Shuttle runs for 2 minutes each time, and outputs 3d
The evaluation was made based on the number of shuttles until B decreased.

Tables 4a, 4b, and 5 show the results of the friction coefficient, shuttle durability, and still durability of Examples 1 to 18 and Comparative Examples A to C. However, in the case of Comparative Example C,
The result was too bad when measured under conditions of temperature 25 ° C and relative humidity (RH) 60%, temperature 40 ° C and relative humidity (RH).
The measurement at 30% and a temperature of -5 ° C was stopped.

Table 4a shows the results of Examples 1 to 9 using a perfluoropolyether having a long-chain alkyl ester.

Table 4b shows the results of Examples 10 to 18 using perfluoropolyether having an aromatic ring ester.

Table 5 shows the results of Comparative Examples A to C.

As is clear from Tables 4 and 5, each embodiment to which the present invention is applied has a small coefficient of friction under each condition of room temperature, high temperature and low temperature, has extremely stable running, and has 100 shuttle runs. After that, no damage was seen on the tape surface, and there was no 3dB decrease in output even after 150 shuttle runs.
Still durability also shows a very good value. On the other hand, in the tape of the comparative example, the coefficient of friction increased as the number of times of shuttle traveling increased, the traveling was unstable, the friction of the tape was observed, and the durability was poor.

 Next, evaluation was performed using a hard disk.

Examples 19 to 36 As Example 19 to Example 36, in the method for producing a hard disk, the perfluoropolyether ester of carboxylic acid was changed to Compound 1 to Compound 18 shown in Tables 1 and 2 to obtain a sample disk. Was prepared. Here, Examples 19 to
Example 27 uses a perfluoropolyether having a long-chain alkyl ester as a lubricant.
Examples 27 to 36 use perfluoropolyether having an aromatic ring ester.

Comparative Examples D and E As Comparative Examples D and E, sample disks were prepared by using perfluoropolyetherester of carboxylic acid as the compound A or the compound B shown in Table 3 in the method for preparing a hard disk.

With respect to the sample disks of Examples 19 to 36 and Comparative Examples D to E produced as described above, the friction coefficient after 20,000 times of CSS was examined by a contact start / stop (CSS) test. . The results are shown in Tables 6a, 6b and 7 below.

Table 6a shows the results of Examples 19 to 27 using a perfluoropolyether having a long-chain alkyl ester.

Table 6b shows the results of Examples 28 to 36 using perfluoropolyethers having an aromatic ring ester.

Table 7 shows the results of Comparative Examples D and E.

As is clear from Tables 6 and 7, even in the CSS test, each example of the present invention has a small coefficient of friction, and the disk of the comparative example has a large coefficient of friction and is inferior in durability.

 Next, evaluation was performed using a coating type magnetic tape.

Examples 37 to 54 As Examples 37 to 54, in the method for producing a coating type magnetic tape, compounds 1 to 18 shown in Tables 1 and 2 were obtained by using perfluoropolyether esters of carboxylic acid in Tables 1 and 2.
To prepare a sample tape. Here, in Examples 37 to 45, the perfluoropolyether having the long-chain alkyl ester was used as a lubricant.
Examples 54 to 54 use perfluoropolyether having an aromatic ring ester as a lubricant.

Comparative Example F and Comparative Example G As Comparative Example F and Comparative Example G, a sample tape was prepared by using a perfluoropolyether ester of carboxylic acid as the compound A or the compound B shown in Table 3 in the method of producing the coating type magnetic tape. Produced.

Comparative Example H As Comparative Example H, a sample tape to which no lubricant was applied was also manufactured.

For each of the sample tapes of Examples 37 to 54 and Comparative Examples F to H produced as described above,
℃, relative humidity (RH) 80%, temperature 25 ° C, relative humidity (RH) 60
% Of each condition before and after aging.

Tables 8a, 8b, and 9 show the results of the friction coefficients of Examples 37 to 54 and Comparative Examples F to H, and Tables 10a and 10 show the results of the stick-slip. b and Table 11. In the table of the stick-slip, the result of the stick-slip is indicated by “○”, and the result of the stick-slip is indicated by “X”.

Table 8a shows the results (coefficient of friction) of Examples 37 to 45 using perfluoropolyether having a long-chain alkyl ester.

Table 8b shows the results (friction coefficient) of Examples 45 to 54 using perfluoropolyether having an aromatic ring ester.

Table 9 shows the results (friction coefficient) of Comparative Examples F to H.

Table 10a shows the results (stick slip) of Examples 37 to 45 using perfluoropolyether having a long-chain alkyl ester.

Table 10b shows the results (stick-slip) of Examples 45 to 54 using perfluoropolyether having an aromatic ring ester.

Table 11 shows the results (stick-slip) of Comparative Examples F to H.

As is clear from Tables 8 to 11, in each of the examples in the coating type, the decrease in the coefficient of friction was small even after aging, and the results were also good in stick-slip after aging. On the other hand, in the tape of the comparative example, the results were poor in both the coefficient of friction and the stick-slip, and in many cases the results were poor not only after aging but also before aging.

〔The invention's effect〕

As is apparent from the above description, perfluoropolyetherester of carboxylic acid is a compound having extremely excellent lubricity, and can be said to be useful as a lubricant for a metal thin film type magnetic recording medium. At the same time, since this compound is compatible with a general-purpose solvent, it can be applied as a lubricant for a coating type magnetic recording medium.

Further, the perfluoropolyether ester of carboxylic acid has a reduced acidity of the carboxylic acid, so that there is little change with time and an instantaneous clock hardly occurs.

According to the present invention, it is possible to obtain a magnetic recording medium having a small friction coefficient even under severe conditions such as high temperature and high humidity or low temperature, and excellent in running stability, abrasion resistance and temperature characteristics.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing an infrared absorption spectrum of Compound 1.

Claims (2)

(57) [Claims] 1. A magnetic recording medium comprising a magnetic layer formed on a non-magnetic support, wherein a perfluoropolyether ester of a long-chain alkyl carboxylic acid is held as a lubricant. . 2. A magnetic recording medium comprising a magnetic layer formed on a non-magnetic support, wherein a perfluoropolyether ester of an aromatic carboxylic acid is held as a lubricant.