JPH07141644A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve durability in an environment of high temp. high humidity or low temp. low humidity while reducing the thickness of a lubricant layer by forming a lubricant layer with a liq. lubricant removed of quality-unstable components. CONSTITUTION:The surface of a magnetic recording medium is coated with a perfluoro-polyether type liq. lubricant having arom. ring-contg. groups at the terminals of each molecule and having molecular skeletons represented by formulae I, II to obtain the objective magnetic recording medium. The liq. lubricant has been removed of low molecular components and unreacted arom. impurities as quality-unstable components by extraction with an org. solvent represented by formula III. The tribochemical stability of the lubricant is improved, the adsorption of water on the resulting lubricant layer can be inhibited and superior durability can be ensured by a thinner lubricant layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium,
More particularly, it relates to a magnetic recording medium having excellent durability.

[Prior Art and Problems to be Solved by the Invention]

In recent years, a contact start stop (CSS) method, which is a method in which a head contacts and rubs against a magnetic recording medium when the drive apparatus is stopped and driven in a small hard disk apparatus, has been recently used as a drive apparatus start / stop method. It occupies the mainstream. However, the above CS
In the S method, the head comes into contact with the magnetic recording medium and rubs against each other, so that a sliding state occurs between the head and the disk when the drive device is started and stopped, causing damage to the disk and the head due to abrasion, head crash and data loss. There is a problem that occurs.

Therefore, in order to avoid the above problems, it has been proposed to provide a protective film such as amorphous carbon or silicon dioxide on the magnetic layer of the disk. However, the protective film alone can sufficiently solve the above problems. Since this cannot be solved, it has been proposed (US Pat. No. 3,778,308) to form a lubricant layer by applying a liquid type lubricant such as perfluoroalkyl polyether on the protective film, and thereafter. Further, it has been proposed to use a perfluoroalkylpolyether having a polar group at the terminal as the lubricant (US Pat. No. 4,267,238, US Pat. No. 4,268,556).

However, since the perfluoroalkyl polyethers produced without any particular application such as commercial products have different average molecular weights, molecular weight distributions and unreacted aromatic impurities contained in the production lots, In order to use as a lubricant in the production of a magnetic recording medium and to impart good durability, there is a problem that it is necessary to set the thickness of the lubricant that matches the texture shape of the magnetic recording medium for each manufacturing lot. .

Therefore, Japanese Patent Laid-Open No. 5-109053,
JP-A-5-234066 proposes a method for removing impurities from a commercially available perfluoroalkyl polyether lubricant. However, these methods are not practical because they lack the ability to remove low molecular weight components.

On the other hand, with the recent improvement in recording density for magnetic recording media, it is necessary to shorten the distance between the magnetic layer and the magnetic head, which reduces the thickness of the protective film and the roughness of the texture shape. Is being pursued. Therefore, in order to improve durability, it is preferable that the thickness of the lubricant layer is thick, but it is necessary to reduce the thickness from the above viewpoint. It also causes problems such as the head sticking to the disk surface. Furthermore, the advent of highly portable personal computers such as notebook computers has caused not only an increase in the number of CSSs but also an increase in the operating environment range. Currently, CSSs are used under various environments such as high temperature and high humidity or low temperature and low humidity. Durability,
Required for magnetic recording media.

Therefore, an object of the present invention is to provide a magnetic recording medium having a thin lubricant layer and excellent durability in various environments such as high temperature and high humidity or low temperature and low humidity.

[0008]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned problems, the present inventors have found that a commercially available perfluoropolyether-based liquid lubricant and a benzene derivative such as toluene and xylene are used. It was found that the magnetic recording medium applied after being purified by using it exhibits excellent durability.

The present invention has been made based on the above findings, and has a group containing an aromatic ring at the molecular end and has the following general formula [Chemical formula 6] (the same as the above general formula [Chemical formula 1]) and In a magnetic recording medium having a surface coated with a liquid lubricant of perfluoropolyether having a molecular skeleton represented by the following formula: Is a low-molecular-weight component and an unreacted aromatic impurity component, which are unstable components of the quality, represented by the following general formula [Chemical formula 8]
(Same as the above general formula [Chemical formula 3]), [Chemical formula 9] (same as the above general formula [Chemical formula 4]) or [Chemical formula 10] (The above general formula [Chemical formula 5]
Same as the above), which has been extracted / removed with an organic solvent,
The present invention provides a magnetic recording medium characterized by the above.

[0010]

[Chemical 6]

[0011]

[Chemical 7]

[0012]

[Chemical 8]

[0013]

[Chemical 9]

[0014]

[Chemical 10]

The magnetic recording medium of the present invention will be described in detail below. The liquid lubricant used in the present invention is a perfluoropolyether-based liquid lubricant having a specific structure in which a quality-unstable component is extracted / removed with a specific organic solvent.

That is, the above-mentioned liquid lubricant is a liquid lubricant obtained by a normal manufacturing process (hereinafter referred to as "untreated liquid lubricant") from which quality unstable components are removed. Here, the untreated liquid lubricant has the above-mentioned specific structure, that is, a group containing an aromatic ring at the molecular end and has the above general formula [Chemical Formula 6] and / or [Chemical Formula 7].
Is not particularly limited as long as it uses a perfluoropolyether compound having a molecular skeleton as a lubricant component, and examples of the group containing an aromatic ring include a piperonyl group and a benzyl group. Examples of the above compounds include the following general formulas [Chemical formula 11] to [Chemical formula 14] (wherein,
l to q are all integers of 1 or more, and are numbers selected so that the number average molecular weight of each compound satisfies 2500 to 10000. ) And the like.

[0017]

[Chemical 11]

[0018]

[Chemical 12]

[0019]

[Chemical 13]

[0020]

[Chemical 14]

[Fomblin AM 2001], [Fomblin AM 3001]
Commercial products such as (all are trade names, manufactured by Montecatini Co., Ltd.) are also examples of the untreated liquid lubricant.

The above-mentioned quality unstable components are low molecular weight components and unreacted aromatic impurity components. Examples of the low molecular weight components include components having a molecular weight of 2000 or less, and the unreacted aromatic impurity components are Examples of the raw material component used in the production of the above liquid lubricant, its modified product, and the like.

The number average molecular weight of the liquid lubricant is
Within the range of 2500 to 10000, and further 3000 to 7
It is preferably in the range of 000.

The above specific organic solvent used in the present invention is represented by the above general formula [Chemical formula 8], [Chemical formula 9] or [Chemical formula 1].
0], specifically, toluene, xylene, benzene, trimethylbenzene, ethylbenzene and the like can be mentioned, and among them, toluene and xylene are particularly preferably used. Moreover, at the time of use, these 1 type (s) or 2 or more types can be used.

The amount of the organic solvent used is preferably 900 to 2000 parts by weight based on 100 parts by weight of the untreated liquid lubricant.

In the magnetic recording medium of the present invention, the object to which the liquid lubricant is applied is not particularly limited, but it is used as a magnetic disk such as a hard disk or a floppy disk, and the magnetic material is magnetically applied onto the substrate by a commonly known method. Examples thereof include a disk having a layer and a protective layer formed thereon.

In order to produce the magnetic recording medium of the present invention, the liquid lubricant obtained by extracting / removing the unstable components of the quality from the above-mentioned untreated liquid lubricant by the following method or the like is subjected to the dip coating method or the like. It can be obtained by applying to the surface of the above-mentioned object by a usual method.

Method: The unprocessed lubricant and the above-mentioned amount of the organic solvent are put in a separating funnel, shaken sufficiently, and then allowed to stand for preferably 12 to 24 hours until phase separation. Next, after sufficient phase separation, the lubricant phase located in the lower phase in the separating funnel is separated. The operation up to this point is repeated several times as necessary. Further, since the separated lubricant phase contains a small amount of an organic solvent, it is preferable to remove it with a rotary evaporator. Finally, a membrane filter is used to remove fine particles, thereby obtaining a liquid lubricant.

Since the liquid lubricant obtained as described above has the quality unstable component removed, the average molecular weight is increased and the molecular weight distribution is decreased as compared with the untreated liquid lubricant. Further, the increase rate of the average molecular weight and the decrease degree of the molecular weight distribution can be freely adjusted by changing the organic solvent.

In the magnetic recording medium of the present invention, since the lubricant layer is formed of the liquid lubricant having a certain quality in which the fluctuation of the quality due to the manufacturing lot of the lubricant is suppressed, the high temperature,
The lubrication characteristics do not change even in a high humidity environment, and as a result, the CSS durability is improved. The reason why such an effect is exerted is considered to be due to the improvement of tribochemical durability and the improvement of hydrophobicity of the lubricant due to the use of the liquid lubricant from which the quality unstable component is removed. To be

[0031]

The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto.

[Example 1] In a separating funnel, 100 g of "Fomblin AM2001" (trade name, manufactured by Montecatini) as an untreated liquid lubricant and 900 g of toluene as an organic solvent.
, And shaken well, and then left for 24 hours for two-phase separation. Then, the lower phase "Fomblin AM 2001"
After the phases were separated, a small amount of toluene taken in on the “Fomblin AM2001” phase side was removed using a rotary evaporator, and subsequently filtered using a 1 μm membrane filter to obtain a liquid lubricant. The GPC spectra of the untreated liquid lubricant and the liquid lubricant are shown in FIGS. 1 and 2, respectively.
Shown in.

The GPC measurement was carried out under the following conditions. Column: Perkin Elmer PL Gel 79911GP-101
79911GP-103 coupled in series ・ Detection: UV detector ・ Detection wavelength: 258 nm

The number average molecular weight of the liquid lubricant was determined by ¹⁹ F-NMR spectrum to be 3300.

Then, the NiP-plated aluminum substrate is polished and textured so that the center line roughness Ra is set to 5.
of 50 nm on the substrate of 50 nm in the Ar gas atmosphere by DC magnetron sputtering, CoCrT
A disc having an a-type magnetic layer of 40 nm and a carbon protective layer formed thereon was prepared. Further, the liquid lubricant was applied to the surface of the disk by a dip coating method. After coating, heat treatment was performed to obtain a magnetic disk (magnetic recording medium of the present invention) having a lubricant layer thickness of 25 liters.

Example 2 In a separating funnel, 100 g of "Fomblin AM2001" (trade name, manufactured by Montecatini Co.) as an untreated liquid lubricant and 900 g of toluene as an organic solvent.
, And shake well, and then 2 to separate the two phases.
It was left for 4 hours. Next, the lower "Fomblin AM 2001" phase was collected and separated using a rotary evaporator.
n AM 2001 ”Toluene slightly taken in on the phase side was removed. The obtained lubricant was placed in a separating funnel, and again extracted and purified with 700 g of toluene to obtain a liquid lubricant. The GPC spectrum of the obtained liquid lubricant is shown in FIG. Further, the number average molecular weight of the obtained liquid lubricant was determined from ¹⁹ F-NMR spectrum to be 3700.

Then, the same liquid lubricant as that used in Example 1 was coated with the above liquid lubricant by a dip coating method. After coating, heat treatment was performed to obtain a magnetic disk (magnetic recording medium of the present invention) having a lubricant layer thickness of 20Å.

COMPARATIVE EXAMPLE 1 A disc similar to the disc used in Example 1 was applied to the untreated liquid lubricant "Fomblin".
AM 2001 "(trade name, manufactured by Montecatini) was applied by a dip coating method. After coating, heat treatment,
A magnetic disk having a lubricant layer thickness of 25Å was obtained.

[Comparative Example 2] A magnetic disk was obtained in the same manner as in Comparative Example 1 except that the thickness of the lubricant layer was 30Å.

(Characteristics) Examples 1 and 2 and Comparative Example 1,
The magnetic disk obtained in No. 2 was subjected to a CSS test [a thin film head (manufactured by GLIDE / WRITE, USA) consisting of a sintered body of Al ₂ O ₃ and TiC was used as a slider material, and the head flying height was 0.1 μm and 3600 rpm. 15 second operation-15 second stop cycle] was carried out, and the CSS resistance was examined by a disk friction / rubbing tester PT101 (manufactured by Pattytec).
The results are shown in [Table 1].

[0041]

[Table 1]

As is clear from the results shown in [Table 1],
Compared to the case where the commercially available lubricant was used as it is as in Comparative Examples 1 and 2, Examples 1 and 2 show excellent durability with a thinner lubricant layer thickness, and the magnetic recording medium of the present invention is durable. It can be seen that it has excellent properties.

[0043]

The magnetic recording medium of the present invention has a thin lubricant layer and is excellent in durability under various environments such as high temperature and high humidity or low temperature and low humidity. Contained in a perfluoropolyether-based lubricant having an aromatic ring at the end of, the quality instability component is extracted and extracted with an organic solvent, so that the lubricant layer is formed using the liquid lubricant, In addition to the increase in tribochemical stability of the lubricant molecule, the adsorption of water to the lubricant layer can be suppressed, and as a result, the thinner lubricant layer exhibits excellent durability.

[Brief description of drawings]

FIG. 1 GPC of untreated liquid lubricant (commercial lubricant)
It is a chart which shows a spectrum.

2 is a chart showing a GPC spectrum of the liquid lubricant obtained in Example 1. FIG.

3 is a chart showing a GPC spectrum of the liquid lubricant obtained in Example 2. FIG.

Claims (4)

[Claims] 1. A perfluoropolyether liquid having a group containing an aromatic ring at the molecular end and having a molecular skeleton represented by the following general formula [Chemical formula 1] and / or [Chemical formula 2]. In a magnetic recording medium having a surface coated with a lubricant, the liquid lubricant has a low molecular weight component and an unreacted aromatic impurity component, which are unstable components, of the following general formulas [Chemical Formula 3] and [Chemical Formula 3]. 4] or [Chemical formula 5] extracted / removed with an organic solvent. [Chemical 1] [Chemical 2] [Chemical 3] [Chemical 4] [Chemical 5] 2. The magnetic recording medium according to claim 1, wherein the liquid lubricant has a number average molecular weight in the range of 2,500 to 10,000. 3. The magnetic recording medium according to claim 1, wherein the group containing an aromatic ring is a piperonyl group. 4. The magnetic recording medium according to claim 1, wherein the organic solvent is toluene or xylene.