JPH0249218A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To maintain an adhesive property and a lubricating effect over a long period of time by holding a specific lubricating agent in the recording medium. CONSTITUTION:The perfluoropolyether ester of carboxylic acid is held as the lubricating agent into the magnetic recording medium. The soln. of the lubricating agent is top coated on the surface of the thin metallic film in case of the recording medium of a thin metallic film type. The coated amt. thereof is 0.5-100mg/m<2>, more preferably 1-20mg/m<2>. The method of holding the lubricating agent into the lubricating agent of a coating type includes a method of internally adding the lubricating agent into the magnetic coated film and a method of top coating the same or combination methods of both, etc. The lubricating agent is added at 0.2-20pts.wt. per 100pts.wt. resin binder in case of the internal addition. Other known lubricating agents may be combined with this lubricating agent. The combination use of an extreme pressure additive is equally well. Further, a rust inhibitor may be used in combination.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to magnetic recording media such as magnetic tapes and magnetic disks, and particularly relates to lubricants.

[Prior Art] Conventionally, magnetic recording media have been prepared by recording a single layer on a non-magnetic support.
Fez0=, FeJn containing CO, 7-Fez0=, 1-F, ezO, containing Co, and Fe1g4
Hertolide compound with Fe, 0. , Heldride compounds containing Co, oxide ferromagnetic powders such as Coo□, or alloy magnetic powders containing Fe, Co, Ni, etc. as main components. 2. Description of the Related Art Coated magnetic recording media, which are manufactured by coating and drying a magnetic paint dispersed in an organic binder such as a polyurethane resin, are widely used.

On the other hand, with the increasing demand for high-density magnetic recording, ferromagnetic metal materials such as Go-Ni alloys can be made into polyester by plating or vacuum thin film formation technology (vacuum evaporation method, sputtering method, ion blating method, etc.). A so-called ferromagnetic metal thin film type magnetic recording medium, which is directly deposited on a non-magnetic support such as a film or a polyimide film, has been proposed and is attracting attention. This ferromagnetic metal thin film type magnetic recording medium not only has excellent coercive force and squareness ratio, and has excellent electromagnetic conversion characteristics at short wavelengths, but also has the ability to make the thickness of the magnetic layer extremely thin, making recording demagnetization possible. It has a number of advantages, such as extremely small thickness loss during recirculation and recirculation, and the ability to increase the packing density of the magnetic material because there is no need to mix an organic binder, which is a non-magnetic material, into the magnetic layer.

However, in the above-mentioned ferromagnetic metal thin film type magnetic recording medium, the surface smoothness of the magnetic layer is very good, so the effective contact area is large, and adhesion phenomenon (so-called sticking) easily occurs. or the coefficient of friction increases, etc.
It has many shortcomings in terms of durability, running performance, etc., and improving them is a major issue.

In general, a magnetic recording medium is subjected to high-speed relative motion with a magnetic head during the process of recording and reproducing magnetic signals, and must run smoothly and stably at this time.

Further, it is better to minimize wear and scratches caused by contact with the magnetic head.

For example, attempts have been made to improve the durability and runnability by coating the magnetic layer of the magnetic recording medium with a lubricant 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, this protective film exhibits good adhesion to the magnetic layer and has a high lubrication effect. are required to demonstrate their abilities. In the case of the above-mentioned ferromagnetic metal thin film type magnetic recording medium,
At first, the friction coefficient decreases and driving performance improves, but
Since the adhesion of the lubricant to the ferromagnetic metal thin film is weak, the lubricant is gradually scraped off by a magnetic head or the like, resulting in a sudden loss of effectiveness.

Furthermore, these adhesion properties and lubrication effects must be excellent even in places with severe temperature conditions such as tropical, subtropical, and cold regions.

However, the operating temperature range of conventionally widely used lubricants is limited, and their properties at high and low temperatures are poor compared to room temperature, and they solidify or freeze especially at low temperatures such as 0 to -5°C. There are many things to do.

Therefore, it was not possible to exhibit a sufficient lubricating effect.

On the other hand, when attempting to internally add a lubricant such as perfluoropolyether to the magnetic layer of a coating-type magnetic recording medium, general-purpose solvents cannot be used, and, for example, the compatibility between the binder and the lubricant is poor. Therefore, the characteristics of the lubricant cannot be fully utilized.

Therefore, it is an object of the present invention to provide a lubricant that maintains adhesion and lubricity under any usage conditions and maintains a lubricating effect over a long period of time, and to provide a magnetic recording medium with excellent running performance and durability. This is the purpose.

Means for Solving C5m] As a result of extensive research into achieving the above-mentioned objective, the present inventors have found that a lubricant containing perfluoropolyether ester of carboxylic acid is suitable for this objective. This discovery led to the completion of the present invention.

That is, the present invention is characterized in that a magnetic recording medium comprising a magnetic layer formed on a nonmagnetic support contains perfluoropolyether ester of carboxylic acid as a lubricant.

Here, the perfluoropolyether ester of carboxylic acid used as a lubricant in the present invention is, for example, one represented by any of the general formulas % (1).

Here, Φ in the formula is a hydrocarbon aromatic ring such as a benzene ring or a naphthalene ring, and may also be a compound having a heterocycle. In addition, halogen, nitro group,
It may contain a cyano group, an alkyl group, etc. on the other hand,
R represents an alkyl group, and is particularly preferably a long-chain alkyl group having 11 or more carbon atoms. n and Il are natural numbers of 1 or more and 6 or less, and m is a natural number of 2 or more.

Furthermore, Rf and Rf' in the above formula are perfluoropolyether groups. For example, Rf has the general formula F-(CFzCF
zCF20)-rcFzcFz----= ・-・・(5
), general formula % formula % (6) or general formula CFzO←C2F40-h-(CF20-h-CF2-
...It is expressed by (7).

For example, Rf' is the general formula % formula % (8) or the general formula CFzO'(-CzF40-)'i-iCF20-)r
-CF2- It is represented by (9). Here, a, b, c in the formula.

Preferably, d, e, and f are natural numbers in the range of 10 to 500. Of course, it is not limited to these as long as it is a perfluoropolyether.

Magnetic recording media to which the present invention is applied can be broadly classified into metal thin film type and coated type, and the method for making such metal thin film type magnetic recording media retain the perfluoropolyether ester of carboxylic acid is as follows: There is a method of top-coating the surface of a metal magnetic thin film. When applying a top coat, the method of applying it is to apply (e.g. spin code) or spray a solution obtained by dissolving the carboxylic acid in a perfluoropolyether ester solvent, or conversely, to apply magnetic recording in this solution. All you have to do is immerse the medium.

When the perfluoropolyether ester of carboxylic acid is top coated on the surface of a metal magnetic material, the coating amount is preferably 0.5 to 100 g/nf, and 1 to 20 g/rr? It is more preferable that If the coating amount is less than 0.5 µ/a, the effects of lowering the coefficient of friction, improving wear resistance, and durability of the present invention will not be apparent, while if it is more than 100 µ/b, the sliding member and ferromagnetic A sticking phenomenon occurs between the metal thin film and the running performance becomes worse.

The metal magnetic thin film, which is the magnetic layer, is formed as a continuous film by PVD methods such as plating, spackling, and vacuum evaporation.
alloy, Co-Pt alloy, Co-Ni-Pt alloy,
Fe-Co alloy, Fe-Ni alloy, Fe-Co-N
In-plane magnetization recording metal magnetic films made of i-based alloys, Fe-N1-B-based alloys, Pe-Co-B-based alloys, Fe-Co-Ni B-based alloys, Co-Cr-based alloy thin films, Co-0 Examples include perpendicular magnetization recording metal magnetic thin films such as system thin films.

In particular, in the case of in-plane magnetization recording metal magnetic thin films, Bi, Sb, Pb, Sn, Ga, I
n, Ge.

A base film of a low-melting point non-magnetic material such as Si or TI is formed, and a metal magnetic material is vapor-deposited or sputtered from the perpendicular direction to diffuse these low-melting point non-magnetic materials into the magnetic metal thin film to eliminate orientation. In addition to ensuring the in-plane method, the coercive force may also be improved.

Further, in the case of a hard disk as described above, a hard protective film such as a carbon film, a diamond thin film, a chromium oxide film, a 5i02 film, etc. may be formed on the surface of the metal magnetic thin film.

On the other hand, methods for retaining the carboxylic acid perfluoropolyether ester in a coated magnetic recording medium include adding it internally to the magnetic coating film, top-coating the surface of the magnetic layer, or a combination of both. etc.

At this time, since conventional lubricants do not dissolve in general-purpose solvents, lubricants were dissolved in, for example, Freon-based solvents and added internally or as a top coat. However, in the present invention,
Since it is a perfluoropolyether ester of carboxylic acid, the perfluoropolyether ester of carboxylic acid can be added internally to a magnetic paint as a lubricant or top coated on the surface of a magnetic layer without using a Freon solvent. is possible.

Here, when the perfluoropolyether ester of the carboxylic acid is internally added to the magnetic layer, it is added in an amount similar to that of a conventional lubricant, for example, 0.5 parts per 100 parts of the resin binding agent. Add 2 to 20 parts by weight.

Also, when top-coating the perfluoropolyether ester of carboxylic acid on the surface of the magnetic layer, it is sufficient to apply the same amount as a conventional lubricant, for example, the amount applied is 0.5 to 100 mg. /nr is preferable, and 1 to 20 .mu./bo is more preferable.

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

Therefore, usable ferromagnetic powders include ferromagnetic iron oxide particles, ferromagnetic chromium dioxide, ferromagnetic alloy powders, hexagonal barium ferrite M1 particles, iron nitride, and the like.

The above-mentioned strong (53) iron oxide particles include those whose X value is in the range of 1.33≦X≦1.50 when expressed by the general formula FeOx, that is, magnetite (γ-Fez03+・1
．． 50), magnetite (Fe30.
．． 50). Cobalt may be added to these ferromagnetic iron oxides for the purpose of increasing coercive force. There are two types of cobalt-containing iron oxide: doped type and deposited type.

”2 Ferromagnetic chromium dioxide includes Coo□ or RLl+Sn+Te for the purpose of improving coercive force.
+Sb, Fe+Ti+V+Mn, etc. can be used.

As the ferromagnetic alloy powder, Fe+Co+Ni, Fe-C
o, FeNi, Fe-Co-N i + Co-Ni
+ Fe-Co-B, Fe-Co-Co-B+ Mn
-Bt +Mn-Al, Fe-Co-V, etc. can be used, and Al can also be added to these for the purpose of improving various properties.
+ S i + T i + Cr + M n +
A metal component such as CuZn may also be added.

The perfluoropolyether ester of carboxylic acid described in -F may be used alone as a lubricant for magnetic recording media, or may be used in combination with a conventionally known lubricant.

Alternatively, perfluoroalkyl carboxylic acid ester,
It can also be used in combination with carboxylic acid perfluoroalkylamide, perfluoroalkylcarboxylic acid perfluoroalkylamide, or derivatives thereof.

Furthermore, 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 30:0 to about 70:30.

The extreme pressure agent reacts with the metal surface due to the frictional heat that accompanies partial metal contact in the boundary lubrication region.
Each reaction product film is formed to prevent friction and wear. Phosphorus-based extreme pressure agents, sulfur-based extreme pressure agents, halogen-based extreme pressure agents, organometallic extreme pressure agents, and composite extreme pressure agents etc. can be used.

Moreover, in addition to the above-mentioned lubricants and extreme pressure agents, a rust preventive agent may be used in combination as necessary.

As the rust preventive agent, any of those normally used as a rust preventive agent for this type of magnetic recording medium can be used, such as phenols, naphthols, quinones, heterocyclic compounds containing nitrogen atoms, and oxygen atoms. , a heterocyclic compound containing a sulfur atom, etc.

The rust preventive agent may be used in combination with a lubricant containing the perfluoropolyether ester of carboxylic acid, but in some cases, the lubricant layer is applied after the rust preventive layer is applied.
It is most effective when applied in two or more layers. Like this 2
When applied in layers, the amount of the rust preventive agent applied is preferably 0.5 to 100 mg/if, and more preferably 1 to 20 mg/if, similar to the above lubricant. . If the coating amount is less than 0.5 cm/n, the effect of improving corrosion resistance will be insufficient, and conversely, if the coating amount is more than loOmg/n, problems will occur in running properties, etc. In the magnetic recording medium of the present invention, the magnetic layer In addition, a back coat layer, an undercoat layer, etc. may be formed as necessary.

For example, the back coat layer is formed by coating a resin binder with the addition of carbon-based fine powder for imparting conductivity or an inorganic pigment for controlling surface roughness.

The perfluoropolyether ester of carboxylic acid of the present invention can be added internally as a lubricant to the Barafco-1 layer or can be incorporated as a top coat.

Alternatively, various combinations are possible, such as internally adding or top-coating the perfluoropolyether ester of the carboxylic acid as a lubricant to both the magnetic layer and Basokuko Bg.

In the metal thin film and coating type magnetic recording media, any conventionally known nonmagnetic support can be used, and there are no limitations in any way.

For example, examples of non-magnetic supports include polymers formed from polymeric materials such as polyesters, polyolefins, cellulose lid "E bodies, vinyl resins, polyimides, polyamides, polycarbonates, etc." These include molecular supports, metal substrates made of aluminum alloys, titanium alloys, etc., ceramic substrates made of alumina glass, etc., glass substrates, etc.The shape is not limited in any way, and may be tape-shaped, sheet-shaped, drum-shaped, etc. The nonmagnetic support may be in any form.Furthermore, the nonmagnetic support may be subjected to a surface treatment to form fine irregularities in order to control its surface properties.

If a rigid substrate such as an A1 alloy plate or a glass plate is used as the non-magnetic support, an oxide film such as alumite treatment or an N1-P film is formed on the surface of the substrate to make the surface hard. You may also do so.

[Effect]

Perfluoropolyether esters of carboxylic acids have high water repellency and have an excellent effect of lowering surface energy. In particular, difunctional (terephthalic acid-based) lubricants have a remarkable decrease in surface energy, and the surface energy of the magnetic layer is 44 mJ/r when the lubricant of the present invention is not used.
However, when using the lubricant of the present invention, it is 10 to 13 m
It becomes possible to reduce the amount to J/nf. This value is smaller than that of fluorine fiber resins such as Teflon, which contributes to lowering the coefficient of friction and exhibits excellent lubrication.

In addition, perfluoropolyether ester of carboxylic acid has improved solubility than perfluoropolyether alone, and is soluble in various hydrocarbon-based (e.g., n-hexane, petroleum ether, etc.) and alcohol-based solvents. Then,
There is no need to use freon-based i8 agents.

At the same time, this durability will not deteriorate even under harsh conditions such as high temperature, high humidity, or low temperature.

In addition, in perfluoropolyether esters of carboxylic acids, perfluoropolyether has an alcohol at the end, which forms an ester bond with the carboxylic acid having a benzene ring. Preventing change.

On the other hand, perfluorocarboxylic acid esters are ester compounds of perfluoropolyether with carboxylic acid at the end, and these compounds (i.e., carboxylic acid bonded to perfluoroalkyl groups) It is a strong acid, easily hydrolyzed, and deteriorates rapidly over time. For this reason, instantaneous clocks are likely to occur.

(Margin below) [Examples] 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.

In the following examples, the present invention was applied to vapor deposition type and coating type magnetic recording media, and their characteristics were evaluated. Therefore, first, the manufacturing method of each magnetic recording medium will be described.

The magnetic recording media produced were vapor-deposited magnetic tapes and hard disks, and coated magnetic tapes.

<Method for producing vapor-deposited magnetic tape> Co was deposited on a 14 μl thick polyethylene terephthalate film by oblique vapor deposition to form a ferromagnetic metal thin film with a thickness of 1000 μl.

Next, perfluoropolyether ester of carboxylic acid was applied as a lubricant on the surface of this ferromagnetic metal thin film in an amount of 5.
mg/rrf and cut into 1 inch width to prepare a sample tape (hard disk manufacturing method) A 15 μm thick Ni-0 plating layer was formed as a non-magnetic metal underlayer. - A Mg alloy substrate (thickness 1.5I, outer diameter 95mm, inner diameter 25+am) was prepared, and a pressure of I x 10-5 Torr and a substrate temperature of 1
Bi was deposited by electron beam at 50°C to a film thickness of 200°C.
A low melting point metal base film was formed.

Then, on this low melting point metal base film, a pressure of I
A metal magnetic F4 film with a thickness of 1000 nm was formed by electron beam evaporation of CO under conditions of 10-' Torr and a substrate temperature of 150°C, and a carbon protective film was further formed on this metal magnetic thin film by a vacuum thin deposition method. .

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

<Method for producing coated magnetic tape) Co-adhered r-Fezes 1
00 parts by weight vinyl chloride-vinyl acetate copolymer 10,
5 parts by weight (manufactured by U, C, C, VAGH) Polyurethane resin 10.5 parts by weight (
Manufactured by Nippon Polyurethane Co., Ltd., M-5033) Carbon (antistatic agent) 5 parts by weight Lecithin (dispersant)
1 part by weight methyl ethyl ketone
150 ff11 parts Methyl isobutyl ketone
150 parts by weight of the above composition as a basic composition,
To the basic composition, 1.5 parts by weight of perfluoropolyether ester of carboxylic acid was added as a lubricant, mixed in a ball mill for 24 hours, taken out through a filter, further added 4 parts by weight of a curing agent, and stirred for 30 minutes. did.

This magnetic paint was applied onto a 12 μm thick polyethylene terephthalate heath to a dry thickness of 5 μm, oriented in a magnetic field, dried and rolled up. This was calendered and cut into 1/2 inch width to produce sample tapes.

In addition, in this example, as specific examples of the above-mentioned perfluoropolyether ester of carboxylic acid, perfluoropolyether ester of long-chain alkyl carboxylic acid (perfluoropolyether having a long-chain alkyl group) and aromatic carbon Perfluoropolyether ester of acid (perfluoropolyether having aromatic ring ester) 2
type was used.

These perfluoropolyether esters of carboxylic acids are synthesized as follows.

Synthesis Example Here, t represents a natural number, R represents a long-chain alkyl group or a hydrocarbon group having an aromatic ring, and Rf represents perfluoropolyether. In other words, it can be easily synthesized by reacting a perfluoropolyether having one or more hydroxyl groups with a carboxylic acid chloride.

Note that by-produced HCI is neutralized by adding a base such as pyridine or triethylamine.

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

As a specific synthesis method, for example, when a perfluoropolyether Rf represented by the general formula % (11) (where S and 2 represent natural numbers) is used, double equivalent of Lyric acid chloride was added dropwise in the presence of two equivalents of triethylamine. After completion of the dropwise addition, the mixture was stirred overnight, thoroughly washed with water, and then purified by column chromatography. The eluent is n-hexane.

According to the above synthesis method, nine types of compounds (Compounds 1 to 9) were synthesized by changing the types of long-chain alkyl groups and perfluoropolyether groups. The synthesized compounds are shown in Table 1.

(Left below) Table 1 can be seen, and the stretching vibration of the carbonyl group is 1760 cm.
C from 1320 to 1160 cm-'
Compound 1 can be identified because of the large stretching vibration of F.

Similarly, nine types of perfluoropolyethers (Compounds 10 to 18) having aromatic ring esters were synthesized.

Table 2 shows perfluoropolyethers having an aromatic ring ester synthesized.

(Left below) Infrared absorption spectrum of Compound 1 in Table 1 above (1st
As shown in the figure. ), there is a double bond C in 3000C11-
H stretching vibration, 2930.2850 cm"'Stretching vibration of CH single bondTable 2In the table, Rf and Rf' represent perfluoropolyether groups, and Rf is represented by the general formula %Formula % (12) ' is the general formula CPzO(CzFJh-(CF!0h-CFr-...
(13), where g, h, and i are 10
It is a natural number of ~500.

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

First, a vapor-deposited sample tape was produced.

Jitsushin IIL: 1Ili-Needle Main Examples 1 to 18, in the method for producing the vapor-deposited magnetic tape, perfluoropolyether esters of carboxylic acids were used as compounds 1 to 1 shown in Tables 1 and 2. Compound 18
A sample tape was prepared. Examples 1 to 9 use perfluoropolyethers having the long-chain alkyl esters as lubricants, and Examples 10 to 18 use perfluoropolyethers having aromatic ring esters as lubricants. It uses ether.

Comparison 1 As Comparative Example A and Comparative Example B, the perfluoropolyether ester of carboxylic acid in the method for producing a thinly attached magnetic tape was used as Compound A and Compound B shown in Table 3. A sample tape was made.

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

A sample tape to which no lubricant was applied was also prepared as Comparative Example C.

For each sample tape of Examples 1 to 18 and Comparative Examples A to Comparative Example C produced as described above, the temperature was 40°C.
°C2 relative humidity (R11) 30χ, temperature 25”C.

The friction coefficient, still durability, and shuttle durability were measured under the conditions of relative humidity (R1 () 60%) and temperature -5'C.
The test was conducted by using a guide pin made of SUS304) and feeding it at a speed of 5III1/SeC with a constant tension applied. Still durability was evaluated by evaluating the decay time until the output decreased by 3 dB in a pause state.

Shuttle durability was evaluated by running the shuttle for 2 minutes each time and determining the number of shuttle runs until the output decreased by 3 dB.

Examples 1 to 18. r of Comparative Examples A to Comparative Examples C! The results of friction coefficient, shuttle durability, and still durability are shown in Table 4a.
, Table 4 and Table 5. However, in the case of Comparative Example C, the results were too poor when measurements were performed at a temperature of 25°C and a relative humidity (R1+) of 60%.
C, relative humidity (RH) 30%, temperature -5°C measurements were discontinued.

Table 4a shows the results of Examples 1 to 9 using perfluoropolyethers having long chain alkyl esters.

Table 4 a Table 4 shows the results of Examples 1O to 18 using perfluoropolyethers having an aromatic ring ester.

Table 4b Table 5 shows the results of Comparative Examples A to C.

Next, we evaluated the hard disk.

As is clear from Tables 4 and 5, each of the examples to which the present invention is applied has a small aJ6 coefficient under the conditions of room temperature, high temperature, and low temperature, and the running is extremely stable, and the shuttle running is completed 100 times. No damage was observed on the tape surface after this, and no 3 dB drop in output was observed even after 150 shuttle runs. The still durability also shows very good values.

On the other hand, with the tape of the comparative example, the coefficient of friction increases as the number of shuttle runs increases, running is unstable, tape wear is observed, and durability is poor.
I! 1lLfL Examples 19 to 36, in the hard disk manufacturing method, perfluoropolyether esters of carboxylic acids were prepared from compounds 1 to 18 shown in Tables 1 and 2.
A sample disk was prepared. Here, Example 1
9 to Example 27 used perfluoropolyether having a long chain alkyl ester as a lubricant,
Examples 27 to 36 use perfluoropolyether having an aromatic ring ester.

Comparison 1031 As Comparative Example and Comparative Example E, sample disks were prepared using the perfluoropolyether ester of carboxylic acid as Compound A or Compound B shown in Table 3 in the hard disk manufacturing method described above.

For each of the sample disks of Examples 19 to 36 and Comparative Examples D to E produced as described above, a contact start/stop (C3S) test was conducted to determine C.
The friction coefficient after 20,000 cycles of 3S was investigated. The results are shown in Table 6a, Table 6 and Table 7 below.

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

Table 6 a shows the results of Examples 19 to 27 using perfluoropolyethers having long chain alkyl esters.

Table 6a Table 7 shows the results of Comparative Example and Comparative Example E.

Table 7 As is clear from Tables 6 and 7, each example of the present invention had a small friction coefficient in the C3S test, and the comparative example disc had a large friction coefficient and was inferior in durability. .

Next, an evaluation was made using coated magnetic tape.

37-=UfljLL As Examples 37 to 54, in the method for producing a coated magnetic tape, the perfluoropolyether ester of carboxylic acid was used as Compounds 1 to 18 shown in Tables 1 and 2, and samples were prepared. A tape was made. Here, Example 3
7 to Example 45 used perfluoropolyether having the long-chain alkyl ester as the lubricant,
Examples 46 to 54 use perfluoropolyether having an aromatic ring ester as a lubricant.

As Comparative Example F and Comparative Example G, perfluoropolyether ester of carboxylic acid was sampled as Compound A or Compound B shown in Table 3 in the method for producing a coated magnetic tape. A tape was made.

Furthermore, as Comparative Example H, a sample tape without any lubricant applied was also prepared.

Examples 37 to 54 produced as described above.
For each sample tape of Comparative Examples F to H, the temperature was 40'C, the relative humidity (R11) was 80%, the temperature was 25°C,
The friction coefficient and stick-slip were measured before and after aging under each condition of relative humidity (RH) of 60%.

Examples 37 to 54. The friction coefficient results for Comparative Examples F to Comparative Examples H are shown in Table 8 a, Table 8 b1, Table 9, and the stick-slip results are shown in Table 1 O a, 10th and X1.
Shown in the table. In the stick-slip table, good stick-slip results are indicated by ○, and poor results are indicated by x.

(Left space below) Table 8 a shows the results (friction coefficient) of Examples 37 to 45 using perfluoropolyethers having long-chain alkyl esters.

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

Table 8b (hereinafter blank) (hereinafter blank) Table 9 shows the results (friction coefficients) of Comparative Examples F to H.

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

Table 10b (blank below) Table 10a shows the results (stick-slip) of Examples 37 to 45 using perfluoropolyethers having long-chain alkyl esters.

Table 10a Table 11 shows the results (stick-slip) of Comparative Examples F to H.

As is clear from Table 1I, Tables 8 to 11, each of the coating type examples shows little decrease in the coefficient of friction even after aging, and also shows good results in stick-slip after aging. there were. On the other hand, the tapes of comparative examples had poor results in terms of both friction coefficient and stick-slip, and many of them had poor results not only after aging but also before aging.

〔Effect of the invention〕

As is clear from the above description, perfluoropolyether ester of carboxylic acid is a compound having extremely excellent lubricating properties, and can be said to be useful as a lubricant for metal thin film type magnetic recording media. At the same time, this compound
Since it is compatible with general-purpose solvents, it can also be used as a lubricant for coated magnetic recording media.

In addition, perfluoropolyether ester of carboxylic acid reduces the acidity of carboxylic acid, so there is little change over time and instantaneous blackout is less likely to occur.

The present invention has a low friction coefficient even under severe conditions such as high temperature, high humidity, or low temperature, and has excellent running stability and wear resistance.
It is possible to obtain a magnetic recording medium with excellent temperature characteristics.

[Brief explanation of the drawing]

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

Claims (1)

[Scope of Claims] A magnetic recording medium comprising a magnetic layer formed on a non-magnetic support, characterized in that a perfluoropolyether ester of carboxylic acid is retained as a lubricant.