JPH0227521A - Magnetic recording media, their manufacturing method, and their lubricants - Google Patents

Abstract

PURPOSE:To form a lubricating film which has less defects and is stable by using fluorine-contained acyl azide as a lubricating agent and forming fluorine- contained isocyanate on a medium surface. CONSTITUTION:A fluorine-contained polymer having the acyl azide group is used as the lubricating agent and after this lubricating agent is stuck to the magnetic recording medium surface 1, the isocyanate group is reproduced by a heating treatment and is in succession polymerized to form the lubricating agent 3 consisting of the fluorine-contained isocyanate polymer. The pot life of the lubricating agent is prolonged and the generation of the defects in the formed lubricating film 3 is decreased by using such fluorine-contained polymer as the lubricating agent of the magnetic recording medium; further, the sliding characteristic of the magnetic recording medium is improved. The generation of the defects as the lubricating film 3 is decreased and the magnetic recording medium having the excellent stability is obtd. in this way.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to magnetic recording media such as magnetic disks, magnetic tapes, magnetic cards, and magnetic drums, and in particular to magnetic recording media provided with a lubricating film made of a fluorine-containing isocyanate polymer. The present invention relates to a recording medium, a method for manufacturing the same, and a lubricant made of a fluorine-containing polymer having an acyl azide group, which is a raw material for a lubricant film.

[Conventional technology]

Normally, the surface of a magnetic recording medium is rubbed by a magnetic recording head or the like during recording and reproduction. To prevent performance deterioration of magnetic recording media due to this friction.

A method of forming a lubricant film on the surface of a magnetic recording medium is generally known.

In this technical field, the use of fluorine-containing compounds such as perfluoropolyether as lubricating film materials is
For example, a compound in which an isocyano group is introduced at the end of perfluoropolyether is disclosed in US Pat. No. 38108.
No. 74. In addition, fluorine-containing incyanate can be used as a lubricant for magnetic recording media (
JP-A-62-14553) and the use of fluorine-containing polyurethane produced from isocyanate and polyhydric alcohol (JP-A-62-187798) have been proposed.

[Problem to be solved by the invention]

In the prior art described above, no consideration was given at all to the stability of the manufacturing process when applying a fluorine-containing isocyanate to a lubricating film of a magnetic recording medium. In other words, fluorine-containing isocyanate has a short pot life, and when forming a lubricant film of fluorine-containing isocyanate as a lubricant for a magnetic recording medium, if a fluorine-containing isocyanate whose pot life has expired is used, it may cause adhesion of solids of the lubricant. There were problems such as defects in the lubricating film.

An object of the present invention is to solve the problems in the above-mentioned prior art, and to reduce the occurrence of defects in the lubricating film.

It is an object of the present invention to provide a magnetic recording medium with excellent stability in the manufacturing process, a method for manufacturing the same, and a lubricant that is a raw material for forming a lubricating film of the magnetic recording medium.

[Means to solve the problem]

The object of the present invention is to use a fluorine-containing polymer having an acyl azide group as a lubricant, and after adhering to the surface of a magnetic recording medium, regenerate the isocyano group by heat treatment, and then polymerize it to form a fluorine-containing isocyanate polymer. This is achieved by forming a lubricating film.

When a fluorine-containing isocyanate is used as a lubricant for a magnetic recording medium, there are problems such as not only a short pot life of the lubricant but also the occurrence of defects when forming a lubricant film. As a result of intensive research to solve this problem,
I learned that the cause of this is that the fluorine-containing isocyanate undergoes hydrolysis or polymerization due to moisture in the air.

Therefore, in order to prevent hydrolysis and polymerization, the present inventors deposited a fluorine-containing polymer having an acyl azide group on the surface of a magnetic recording medium, and then heated the 7-syl azide group of the fluorine-containing polymer on the medium. It has been found that by decomposing isocyano groups and subsequently polymerizing them, a lubricating film made of a homogeneous fluorine-containing isocyanate polymer with few defects can be formed.

When the fluorine-containing polymer having an acyl azide group of the present invention is used as a lubricant for a magnetic recording medium, the pot life of the lubricant becomes longer and the occurrence of defects in the formed lubricant film is reduced. It was also found that the properties were improved.

The improvement in sliding properties is thought to be due to the improvement in the crosslinking density of the fluorinated isocyanate polymer.

The present invention provides a magnetic recording medium having a magnetic film formed directly or through an underlayer on a substrate, or a protective film on the magnetic film, wherein the magnetic film or the protective film contains a magnetic film containing an acyl azide group. A lubricant made of a fluoropolymer is attached and then heat treated to form a lubricant film made of a fluorine-containing isocyanate polymer on the magnetic film or protective film.

The present invention relates to a method for manufacturing a magnetic recording medium having a magnetic film formed directly or via an underlayer on a substrate, or a protective film on the magnetic film.

After attaching a lubricant made of a fluorine-containing polymer having a basic skeleton of a fluoropolyether chain or an alkyl chain and at least one acyl azide group on the magnetic film or protective film, heat the film to a temperature of, for example, 100 to 200°C. treatment to regenerate isocyano groups in the fluoropolymer,
This is a method in which a lubricating film made of a fluorine-containing isocyanate polymer is formed on the magnetic film or protective film by subsequent polymerization.

2. The lubricant that is the raw material for forming the lubricant film of the present invention is as follows.

A fluoropolymer having an acyl azide group represented by the general formula % formula % () (in the formula, t Rt--Rx'- represents a fluorine-containing carbon group selected from a perfluoropolyether group and a perfluoroalkyl group) consisting of the above general formula (1) or (II)
R z -Rt'- constitutes a fluorine-containing polymer having an acyl azide group represented by:

-((CF,0)P(CF,CF,0)41--((C
It is desirable to have a fluorine-containing carbon group selected from F, CF, CF, O) - (in the formula, + Pp que re S represents an integer from 3 to 100).

[Effect]

The lubricant that forms the lubricant film of the magnetic recording medium of the present invention is a fluorine-containing polymer having an acyl azide group, so it is stable against moisture when attached to the medium surface, and nitrogen is then dissociated by heat treatment. to produce isocyano groups,
The produced fluorine-containing incyanate undergoes hydrolysis and polymerization to form a lubricating film made of the desired fluorine-containing isocyanate polymer.

In the method for producing an information recording medium of the present invention, the fluorine-containing polymer having an acyl azide group used as a lubricant is one of the compounds having a basic structure of a fluoropolyether chain or an alkyl chain and having at least one acyl azide group. selected from.

The fluoropolyether chain or fluoroalkyl chain may be not only a linear chain but also a monobranched chain. Examples of the fluorine-containing polymer having an acyl azide group include N, 0C ((CF, O), (CF, C
F2O), 3CON, .

Examples include.

When applying the above-mentioned fluorine-containing polymer having an acyl azide group to a magnetic recording medium, for example, as shown in the manufacturing process diagram of FIG. state.

It is attached by a spray wipe method, a dip method, a spin code method, etc. [Fig. 3(b)].

And the fluoropolymer attached to the medium surface.

Generates isocyano groups by heating and polymerizes on the medium surface [
FIG. 3(c)), and a lubricating film made of the fluorine-containing incyanate polymer is formed [FIG. 3(d)].

The temperature required for the formation and polymerization of the above-mentioned isocyano groups varies depending on the type of fluoropolymer.

Since the reaction is slow at low temperatures and the medium tends to deteriorate at high temperatures, the temperature range is generally preferably 100 to 200°C.

2. In the present invention, it is important to convert the fluorine-containing acyl azide into a fluorine-containing isocyanate on the surface of the information recording medium and perform 9-polymerization. You may use .

〔Example〕

Hereinafter, nine embodiments of the present invention will be listed and explained in more detail.

First, Examples 1 and 2 show the synthesis of a fluorine-containing polymer having an acyl azide group.

(Example 1) Perfluoropolyether-α represented by the following formula (1)
, ω-diacid dimethyl ester (average molecular weight 2000)
20g of solution.

CH, O, C ((CF, O), (CF, CF20),)
Co, CHI-(1) hydrazine (monohydrate) 1.5g
Gradually drip.

The reaction was stirred at room temperature for 4 hours.

After the reaction was completed, unreacted hydrazine was distilled off under reduced pressure.

A compound represented by the following formula (2) was obtained.

H,NNHOC[(CF,0)n(CF,CF,O),
)CONHNH.

・・・・・・・・・(2) 20g of the compound represented by formula (2) and 1 part of sodium nitrite
．． Added 8g. The above mixture was ice-cooled to 0-5°C, and 5%
After 0 drops of hydrochloric acid (50 mm) were gradually added dropwise, water cooling was continued and stirring was continued for 6 hours. Wash the above mixture with water, 1.
A 1,2-trichlorotrifluoroethane (hereinafter abbreviated as Freon) solution was prepared, dried over anhydrous magnesium sulfate, and the solvent was distilled off to obtain a compound represented by the following formula (3).

N5OC((CF2O)a(CF,CF,O),)CO
N, ------- (3) In the infrared spectrum of the compound represented by the above formula (3), absorption of the azide group was observed in 2200c Otori-1.

(Example 2) ω-Polyhexafluoropropylene oxide acid methyl ester represented by the following formula (4) (average molecular weight 2500)
25g of solution.

CF, CF.

Hydrazine (monohydrate) Ig was added dropwise and reacted by stirring at room temperature for 2 hours. After completion of the reaction, unreacted hydrazine was distilled off under reduced pressure to obtain a compound represented by the following formula (5).

1 g of sodium nitrite was added to 25 g of the compound represented by formula (5). The above mixture was ice-cooled to 0 to 5°C, and 50 mQ of 5% hydrochloric acid was gradually added dropwise. After 6 drops, water cooling was continued and stirring was continued for 6 hours.

After washing the above mixture with water and making it into a Freon solution.

It was dried over anhydrous magnesium sulfate, and the solvent was distilled off to obtain a compound represented by the following formula (6).

In the infrared spectrum of the compound represented by the above formula (6), absorption of the azide group was observed at 2200 cm-'.

Next, regarding the synthesis of fluorine-containing isocyanate used as a comparative example, Comparative Example 1. This is shown in Comparative Example 2.

(Comparative Example 1) 10 g of the compound of formula (3) synthesized in Example 1 was heated at a temperature of 90° C. for about 1 hour in a dry nitrogen atmosphere.

A fluorine-containing isocyanate represented by the following formula (7) was obtained.

0NC((CF,O),(CF,CF,O),)NCO
---.-(7) In the infrared spectrum of the compound represented by the above formula (7), absorption of isocyano group was observed at 2300 cm''1.

(Comparative Example 2) The compound Log shown by formula (6) synthesized in Example 2 was heated at a temperature of 90° C. for about 1 hour in a dry nitrogen atmosphere.
A fluorine-containing isocyanate represented by formula (8) was obtained.

In the infrared spectrum of the compound represented by the above formula (8), the absorption of isocyano group at 2300c-1 is Il! It was measured.

The structural formulas of the fluorine-containing acyl azides represented by the above formulas (3) and (6) and the fluorine-containing incyanates represented by the formulas (7) and (8) are summarized in Table 1 below.

Next, Examples 3 to 8 show examples in which the fluorine-containing polymer having an acyl azide group of the present invention is applied to a magnetic recording medium.

(Example 3) As a magnetic recording medium, as shown in FIG. 1, magnetic powder (γ-F 6 = Os
) was dispersed therein to form a magnetic coating film 2. A 0.5% (by weight) Freon solution of the fluorine-containing acyl azide represented by the above formula (3) was spray-coated onto a 5-inch diameter coated magnetic disk.

Next, this magnetic disk was heated at 200° C. for 2 hours to form a lubricating film 3.

Using the magnetic disk prepared in the above procedure, a magnetic head with a piezo element attached to the arm was levitated at a height of 0.2μ, and the number of peaks exceeding five times the average output noise level of the piezo element was detected in the lubricating film. It was defined as the number of defects. Note that in order to measure noise and defects separately, the above method is limited to peaks that are five times or more the average output noise level.

Samples were prepared using lubricant solutions that had been used for 1 hour, 10 days, and 1 month after the lubricant solution was prepared.
The number of defects was determined for the sample. The results are shown in Table 2.

The number of lots is 1000, and the thickness of the lubricating film is approximately 1
There were 00 people.

(Example 4) A sample was prepared in the same manner as in Example 3 using the compound represented by the above formula (6) as the fluorine-containing acyl azide.

(Comparative Example 3) A sample was prepared in the same manner as in Example 3, using the fluorine-containing isocyanate represented by the above formula (7) instead of the fluorine-containing acyl azide.

Blank space below (Comparative Example 4) A sample was prepared in the same manner as in Example 3, using the fluorine-containing incyanate represented by the above formula (8) instead of the fluorine-containing acyl azide.

The test results of the samples prepared in Examples 3 and 4 and Comparative Examples 3 and 4 above are summarized in Table 2.

(Example 5) As a magnetic recording medium, as shown in FIG.

A film with a thickness of 0.25 mm was formed on the NLP-plated AQ alloy substrate 1 by high-frequency sputtering in an Ar gas atmosphere.
μm Cr film6. Co-Ni-Z with a film thickness of 0.06μ
Using a magnetic disk on which a metal magnetic film 2' made of r-alloy and a carbonaceous protective film 4 with a film thickness of 0.05 μm were sequentially formed, and using a compound represented by the above formula (3) as a fluorine-containing acyl azide, A magnetic disk on which a lubricating film 3 was formed was prepared in the same manner as in Example 3, with a margin of 7° or less (Example 6). Samples were prepared in a similar manner.

(Comparative Example 5) A sample was prepared in the same manner as in Example 5 using the fluorine-containing isocyanate represented by the above formula (7) instead of the fluorine-containing acyl azide.

Table 3 shows the results of determining the number of defects in the lubricating film in Examples 5 and 6 and Comparative Example 5.

(Example 7) A magnetic disk produced in the same manner as in Example 5 was mixed with 0.5wt of fluorine-containing acyl azide represented by the above formula (3).
% Freon solution and then pulled up to apply a dip. Next, this magnetic disk was heated at 200°C for 2 hours to form a lubricating film at, xi&*m°7.
Blank space below (Example 8) A sample was prepared in the same manner as in Example 7 using the fluorine-containing acyl azide represented by the above formula (6).

(Comparative Example 6) A sample was prepared in the same manner as in Example 7, using the fluorine-containing incyanate represented by the above formula (8) instead of the fluorine-containing acyl azide.

Table 4 shows the results of determining the number of defects in the lubricating film in Examples 7 and 8 and Comparative Example 6.

The following can be seen from the above Examples 3 to 8 and Comparative Examples 3 to 6.

As is clear from Table 2, when a lubricating film is formed by spray coating, the conventional method using fluorine-containing isocyanate (Comparative Examples 3 and 4), compared to the present invention (Examples 3 and 4), after 10 days. The number of defects is more than one digit, and it increases even more after one month. The present invention, which uses a compound with protected isocyano groups, provides a stable lubricant film with a small number of defects over a long period of time.

Further, as is clear from Comparative Example 5 and Examples 5 and 6 in Table 3, the present invention is effective not only for coated magnetic films but also for metal magnetic films.

Furthermore, as shown in Comparative Example 6 and Examples 7 and 8 in Table 4, the present invention is effective not only for spray coating but also for dip coating.

Further, a 2vt% Freon solution of the compounds represented by formulas (3), (6), (7), and (8) was prepared, and the temperature was 27°C.
As a result of an experiment in which air with a humidity of 60% RH was sealed and left to stand, it was found that the compounds represented by formulas (7) and (8) having an isocyano group produced solid insoluble matter after two weeks.
The compounds represented by formulas (3) and (6) obtained in Examples 1 and 2 of the present invention in which the isocyano group was protected remained stable without forming any solid insoluble matter even after being left for one month. It was found that when used as a lubricant, the change over time is small and it is effective.

In the above Examples and Comparative Examples, the number of defects is shown when forming a lubricating film with a thickness of 100 people.

Similar effects were obtained when forming film thicknesses other than this.

In addition, in the said Comparative Examples 3-6 and Examples 3-8.

Before applying the lubricant, filtration is performed using a φ=0.2 μι filter. Therefore, the number of defects in Comparative Examples 3 to 6 is as follows.

30% is a very small value. Although filtration removes lubricant solids to some extent and reduces the number of defects, it is not as effective when isocyano groups are protected as in the present invention.

As explained in the above examples, it can be seen that the lubricating film of the magnetic recording medium of the present invention has few defects and can provide a stable manufacturing process over a long period of time.

Next, Examples 9 to 14 demonstrate that the two lubricating films of the present invention have excellent sliding properties.

(Example 9) Epoxy and phenol as magnetic recording media.

A fluorine-containing acyl azide represented by formula 9 (3) is coated to a predetermined thickness on a 5-inch diameter coated magnetic disk prepared by dispersing magnetic powder (γ-FeiOs) in a binder made of polyvinyl butyral resin. did. The lubricant was applied by spraying it in the form of a Freon solution, and then, while rotating the magnetic disk, excess lubricant was wiped off with gauze tape until the lubricant reached a predetermined film thickness. In addition.

The film thickness of the lubricant was measured using a Fourier transform infrared spectrometer.

Next, this magnetic disk was heated at 200°C for 2 hours,
It was used as a lubricating film.

The sliding strength of the magnetic head was measured by using a sapphire slider (a spherical slider with a radius of curvature of 50 layers) to which a load of 20 g was applied to the magnetic disk prepared by the above method.
Repeatedly slide at a sliding speed of 20 positions/s,
Durability was evaluated by measuring the number of times until scratches appeared on the surface of the magnetic recording medium.

(Example 10) A sample was prepared in the same manner as in Example 9 using the fluorine-containing acyl azide compound represented by formula (6).

(Comparative Example 7) A sample was prepared in the same manner as in Example 9, using a fluorine-containing isocyanate represented by formula (7) instead of the fluorine-containing acyl azide.

Example 9 above. The test results for IO and Comparative Example 7 are shown in Table 5.

Table 5 (Example 11) As a magnetic recording medium, a 0.25 μ-thick Cr film and a 0.06 μ-thick Cr film were deposited on an NLP-plated A2 alloy substrate by high-frequency sputtering in an Ar gas atmosphere. G
A metal magnetic film made of o-Ni-Zr alloy.

A magnetic disk was prepared by sequentially forming a carbonaceous protective film with a film thickness of 0.05μ, and a lubricating film was formed in the same manner as in Example 9 using a fluorine-containing acyl azide represented by formula (3) as a lubricant. Formed.

The sliding strength was measured using a sapphire slider (curvature radius of 50 μm) at a load of 20 g and a sliding speed of 2.
Evaluation was performed at 0 m/s using the same method as the sliding test method described above.

(Example 12) A sample was prepared in the same manner as in Example 11 using a fluorine-containing acyl azide compound represented by formula (6).

(Comparative Example 8) A sample was prepared in the same manner as in Example 11 using a fluorine-containing incyanate represented by formula (7) instead of the fluorine-containing acyl azide.

The test results for Examples 11 and 12 and Comparative Example 8 above are shown in Table 6.

Table 6 (Example 13) As a magnetic recording medium, a film with a thickness of 0.5 mm was deposited on a polyimide film.
A floppy disk was prepared in which a 22 μm Co-Cr metal magnetic film and a 0.02 μm thick boron protective film were sequentially deposited, and a fluorine-containing acyl azide represented by formula (3) was used as a lubricant. A lubricating film was formed in the same manner as in Example 9.

The sliding strength was measured by gluing the above floppy disk to a glass plate and using a sapphire slider (curvature radius of 50 mm).
) using a load of 20 g and a sliding speed of 2 m/s, and was evaluated in the same manner as the above-mentioned sliding test method.

(Example 14) A sample was prepared in the same manner as in Example 13 using the fluorine-containing acyl azide compound represented by formula (6).

(Comparative Example 9) A sample was prepared in the same manner as in Example 13 using a fluorine-containing isocyanate represented by formula 2 (7) instead of the fluorine-containing acyl azide.

The test results for Examples 13 and 14 and Comparative Example 9 above are shown in Table 7.

The following can be seen from Examples 9 to 14 and Comparative Examples 7 to 9 in Table 7 and above.

As shown in Table 5, when Comparative Example 7 is compared with Examples 9 and 10, which have almost the same film thickness, the sliding strength of the magnetic disks according to the present invention is improved by about three times. Is recognized.

Also, Examples 11 and 12 in Table 6. Example 13 in Table 7
, 14, it is clear that the present invention can provide the same excellent sliding strength as a coated magnetic film even for metal magnetic films.

As explained in the above two embodiments of the present invention.

It can be seen that the magnetic recording medium according to the present invention exhibits good sliding strength in all cases and has excellent durability and reliability as a magnetic recording medium.

〔Effect of the invention〕

As explained in detail above, in the magnetic recording medium of the present invention, a fluorine-containing acyl azide is used as a lubricant,
Because the manufacturing process uses fluorine-containing isocyanate to generate on the medium surface, it is possible to form a stable lubricant film with few defects over a long period of time without being affected by the hydrolyzability and self-polymerization of fluorine-containing incyanate. A magnetic recording medium with excellent durability and reliability can be obtained.

Furthermore, the lubricating film of the present invention can be applied to coated magnetic recording media, Go
- A sputtered metal magnetic recording medium such as Ni-Zr, a metal magnetic film formed by plating or vacuum evaporation, and carbon on the magnetic film.

In addition to magnetic recording media with protective films such as boron.

It is also effective for magnetic recording media in which, for example, micropores are formed on the surface and impregnated with a lubricant.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the cross-sectional structure of a magnetic disk illustrated in Example 3 of the present invention, FIG. 2 is a schematic diagram showing the cross-sectional structure of a magnetic disk illustrated in Example 5 of the present invention, and FIG. 1 shows a manufacturing process diagram of the magnetic recording medium of the present invention. 1...Substrate 2...Magnetic coating film 2'...
・Metal magnetic film 3...Lubricating film 4...Protective film
5... NiP Metsuki 6... Cr membrane agent patent attorney Junnosuke Nakamura

Claims (1)

[Claims] 1. In a magnetic recording medium having a magnetic film formed directly or through an underlayer on a substrate, or a protective film on the magnetic film, an acyl azide is formed on the magnetic film or the protective film. A magnetic recording medium characterized in that a lubricant made of a fluorine-containing polymer having a group is attached and then heat-treated to form a lubricant film made of a fluorine-containing isocyanate polymer on the magnetic film or protective film. . 2. In a method for manufacturing a magnetic recording medium having a magnetic film formed directly or through an underlayer on a substrate, or a protective film on the magnetic film, a fluoropolyether is formed on the magnetic film or the protective film. After attaching a lubricant made of a fluorine-containing polymer having a basic skeleton of a chain or alkyl chain and at least one acyl azide group, heat treatment is performed to regenerate isocyano groups in the fluorine-containing polymer, followed by subsequent polymerization. A method for manufacturing a magnetic recording medium, comprising forming a lubricating film made of a fluorine-containing isocyanate polymer on the magnetic film or protective film. 3. A method for manufacturing a magnetic recording medium according to claim 2, characterized in that the temperature of the heat treatment is 100 to 200°C. 4. The lubricant used for magnetic recording media has the general formula R_f-CON_2... (I) or N_2OC-R_f'-CON_2...
(II) (In the formula, R_f- and -R_f'- represent a fluorine-containing carbon group selected from a perfluoropolyether group and a perfluoroalkyl group.) Consisting of a fluorine-containing polymer having an acyl azide group represented by A lubricant for magnetic recording media characterized by: 5. In the lubricant for magnetic recording media according to claim 4, R_f- constitutes a fluorine-containing polymer having an acyl azide group represented by the general formula (I) or (II).
, -R_f'- is ▲There are mathematical formulas, chemical formulas, tables, etc.▼, -[(CF_2O)_p(CF_2CF_2O)_q]
-, -[(CF_2CF_2CF_2O)_s]-, (wherein p, q, r, and s represent integers from 3 to 100.) Magnetic recording characterized by being a fluorine-containing carbon group selected from Media lubricant. 6. The lubricant according to claim 4 contains a compound having an acyl azide group represented by the general formula ▲ Numerical formula, chemical formula, table, etc. ▼ (wherein, n represents an integer from 3 to 100). A lubricant for magnetic recording media characterized by being made of a fluoropolymer.