JP4629390B2 - Lubricant, magnetic recording medium and head slider - Google Patents

Description

  The present invention relates to a lubricant for a magnetic recording apparatus.

  In a magnetic recording apparatus, a head slider provided with a recording conversion element (also simply referred to as a head in the present invention) reads and writes information while flying over a hard disk, which is a magnetic recording medium.

  The distance between the head and the magnetic layer for recording (writing) or reproducing (reading) magnetic information on the hard disk is called magnetic spacing. The smaller the magnetic spacing, the higher the recording density. On the other hand, in order to increase the information transfer speed, it is necessary to increase the rotational speed of the hard disk. With recent improvements in recording density and transfer speed, low flying height and high speed rotation have progressed. Currently, the flying height of the head is about 10 nm and the rotation speed is about 15000 rotations / minute (rpm).

  In a hard disk drive, a lubricant is generally applied to a thickness of about 1 to 2 nm on a magnetic disk or a head slider in order to increase drive reliability. This lubricant reduces friction and wear when the head comes into contact with the disk and prevents the occurrence of trouble.

Since the film thickness of the lubricant is about 10% of the flying height of the head, the thickness is not negligible with respect to the magnetic spacing (see, for example, Non-Patent Document 1), and the recording density is reduced. In order to improve, it is important to reduce the thickness of the lubricant and reduce the magnetic spacing.
JP 2003-162810 A (Claims) X. Ma et al., “Ie Triple E Transaction on Magnetics (IEEE Trans. Magn.), 2001, Vol. 37, p. X. Ma et al., “Journal of Chemical Physics, 1999, 110, p. 3129-3137.

  However, since the lubricant molecules are finite in size, the lubricant film thickness cannot be made thinner than the film thickness for one molecule. Even though the average value can be reduced, this will reduce the coverage of the lubricant.

  It is known that the film thickness for one molecule of the lubricant is determined by the molecular weight of the lubricant (see, for example, Non-Patent Document 2), and by reducing the molecular weight, the film thickness for one molecule is reduced. Is possible.

  However, the lubricant has characteristics that it is likely to evaporate when the molecular weight is reduced, and to be easily scattered during high-speed rotation. Therefore, at present, the limit value for lowering the molecular weight is defined in consideration of HDI (head disk interface) characteristics such as lubricant wear during high-speed rotation. In order to exceed this limit value, a lubricant is required in which the film thickness for one molecule is sufficiently thin even when polymerized.

Hard disk drives are used in a wide range of temperature environments from low to high temperatures. In general, use of a lubricant with high viscosity improves durability at high temperatures. In order to increase the viscosity, it is conceivable to increase the molecular weight or use a lubricant having a highly polar end group. However, when the molecular weight is increased, the film thickness for one molecule is increased, which is not suitable for low levitation. In addition, when the viscosity is increased, at low temperatures, the lubricant is depleted due to friction and the durability of the magnetic recording medium and the head decreases.

  The present invention solves the above-mentioned problems, and even if a high molecular weight lubricant is used, the thickness of the lubricating layer can be made extremely small, and the reliability in a wide temperature environment is improved without impairing the flying stability. The goal is to develop technology that can Still other objects and advantages of the present invention will become apparent from the following description.

  According to one aspect of the present invention, a structural unit of formula (1) having a hydroxy group, a structural unit of formula (2), a structural unit of formula (3), a structural unit of formula (4) having a hydroxy group, Fluorinated having a number average molecular weight of 4000 or more and 12000 or less, and an average of 1.0 to 10.0 hydroxy groups in the middle of the molecular chain. Lubricants containing polyethers are provided.

-CF ₂ CH ₂ OH (1)
-CF _2- (2)
-CF ₂ CF _2- (3)

本発明の他の一態様によれば、式（８）の化合物（式（８）中ｘは、互いに独立に任意の正の整数である。）とエピクロロヒドリンとを反応させてなり、数平均分子量が４０００以上１２０００以下で、かつ、分子鎖の途中のヒドロキシ基を、一分子中に平均して１．０〜１０．０個有するフッ素化ポリエーテルを含有する潤滑剤が提供される。

According to another aspect of the present invention, a compound of the formula (8) (in the formula (8), x is independently any positive integer) and epichlorohydrin are reacted. Provided is a lubricant containing a fluorinated polyether having a number average molecular weight of from 4000 to 12000 and having an average of 1.0 to 10.0 hydroxy groups in the middle of the molecular chain in one molecule. .

HOCH ₂ CF ₂ O (CF ₂ CF ₂ O) _x (CF ₂ O) _x CF ₂ CH ₂ OH (8)
According to the above aspect, a lubricant is obtained in which the film thickness for one molecule is sufficiently thin even when polymerized. If this lubricant is used, the film thickness of the lubricating layer can be made very small even with a high molecular weight, and the reliability in a wide temperature environment can be improved without impairing the flying stability.

In any embodiment, the average number of hydroxy groups in the middle of the molecular chain is 1.0 to 5.0 per molecule, and the average value of the number average molecular weight of the structural portion between adjacent hydroxy groups is 3000. At least one compound selected from the group consisting of formula (5), formula (6) and formula (7), comprising a fluorine compound other than fluorinated polyether, Being
R ¹ CF ₂ O— (CF ₂ CF ₂ O) _p — (CF ₂ O) _q —CF ₂ —R ² .. (5)
R ¹ —O— (CF ₂ CF ₂ CF ₂ O) _r —CF ₂ CF ₂ —R ² .. (6)

（上式中、Ｒ¹，Ｒ²は、互いに独立に、かつ各式について独立に、ヒドロキシ基、カルボキシ基、アミノ基およびフォスファゼン環、ならびに、ヒドロキシ基、カルボキシ基、アミノ基およびフォスファゼン環からなる群から選ばれた基を置換基として一個以上含み、カルボニル基またはエーテル基またはカルボニル基とエーテル基とを含んでいてもよく、二重結合または三重結合または二重結合と三重結合とを含んでいてもよく、枝分かれしていてもよい一価の脂肪族炭化水素基、ならびに、ヒドロキシ基、カルボキシ基、アミノ基およびフォスファゼン環からなる群から選ばれた基を置換基として一個以上含む一価の芳香族炭化水素基および一価の複素環式芳香族炭化水素基からなる群から選ばれた基であり、ｐ，ｑ，ｒ，ｓは任意の正の整数である。式（５）、式（６）および式（７）の各構造単位は、各化合物の構造中ランダムに配列できる。）が好ましい。

(In the above formula, R ¹ and R ² are independently of each other and independently of each other, each consisting of a hydroxy group, a carboxy group, an amino group, and a phosphazene ring, and a hydroxy group, a carboxy group, an amino group, and a phosphazene ring. It contains one or more groups selected from the group as a substituent, may contain a carbonyl group, an ether group, or a carbonyl group and an ether group, and contain a double bond, a triple bond, or a double bond and a triple bond. And a monovalent aliphatic hydrocarbon group which may be branched, and a monovalent aliphatic hydrocarbon group, and a monovalent group containing one or more groups selected from the group consisting of a hydroxy group, a carboxy group, an amino group and a phosphazene ring as a substituent. A group selected from the group consisting of an aromatic hydrocarbon group and a monovalent heterocyclic aromatic hydrocarbon group, and p, q, r, and s are arbitrary Of an integer. Equation (5), each structural unit of the formula (6) and (7) can be arranged in the structure of randomly for each compound.) Are preferred.

  According to still another aspect of the present invention, there is provided a magnetic recording medium including a magnetic layer, a protective layer on the magnetic layer, and a magnetic recording medium lubricating layer on the protective layer, wherein the magnetic recording medium lubricating layer is A magnetic recording medium to which the above-described lubricant is applied, and a head slider provided with a recording conversion element for performing recording and / or reproduction on the magnetic recording medium, on the side facing the magnetic recording medium There is provided a head slider having a head slider lubrication layer in which a protective layer and the above-described lubricant are applied to the head slider surface.

  About these aspects, it is preferable that it is what was heat-processed after application | coating of a lubricant, and what was ultraviolet-irradiated.

  According to still another aspect of the present invention, a magnetic recording apparatus including the magnetic recording medium and a head slider is provided.

  According to the above aspects, a magnetic recording medium, a head slider, and a magnetic recording apparatus having a lubricating layer having a very small film thickness and improved reliability in a wide temperature environment without impairing flying stability can be obtained.

  According to the present invention, a lubricant can be obtained in which the film thickness for one molecule is sufficiently thin even when polymerized. If this lubricant is used in a magnetic recording medium lubricating layer or a head slider lubricating layer of a magnetic recording apparatus, the thickness of these lubricating layers can be made extremely small, and the stability in flying temperature can be reduced without sacrificing flying stability. Reliability can be increased.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, formulas, examples and the like. In addition, these figures, formulas, examples, etc., and explanations illustrate the present invention, and do not limit the scope of the present invention. It goes without saying that other embodiments may belong to the category of the present invention as long as they match the gist of the present invention.

  As a lubricant that gives a molecular structure in which the film thickness of one molecule does not increase even when the molecular weight is increased, perfluoropolyether having a functional group having a polar group at the middle part of the molecule is known (for example, Patent Documents). However, the specific molecular structure, molecular weight range, etc. remained unclear.

  As a result of research, high molecular weight lubricants are used when used in magnetic recording medium lubrication layers and head slider lubrication layers of magnetic recording devices, even if they are not perfluorostructures, due to fluorinated polyethers having a specific structure. However, it was found that the thickness of the lubricating layer can be made very small, and the reliability in a wide range of temperature environments can be improved without impairing the flying stability.

  That is, the lubricant according to the present invention is obtained by reacting a compound of formula (8) (in formula (8), x is any positive integer independently of each other) and epichlorohydrin, A fluorinated polyether having an average molecular weight of 4000 or more and 12000 or less and having an average of 1.0 to 10.0 hydroxy groups in the middle of the molecular chain in one molecule is contained. Any known method can be employed for this reaction. Hydroxy groups in the middle of the molecular chain originate from epichlorohydrin.

HOCH ₂ CF ₂ O (CF ₂ CF ₂ O) _x (CF ₂ O) _x CF ₂ CH ₂ OH (8)
According to the present invention, the film thickness for one molecule can be made sufficiently thin even if the polymer is formed.

  In a lubricant containing a fluorinated polyether having such a structure, the hydroxy group in the middle of the molecule is probably the surface to which the lubricant is applied (hereinafter referred to as the surface to be coated) together with the hydroxy groups at both ends of the molecule. Therefore, even if a high-molecular-weight lubricant is used, the film thickness of the lubricating layer can be very small. .

  This will be described with reference to FIGS. FIG. 1 is a schematic view showing a state in which a fluorinated polyether 1 of the present invention having one hydroxy group in the middle of a molecular chain is attached to an application surface 2 with a polar group Z. FIG. 2 is a schematic view showing a state in which a fluorinated polyether 1 having no polar group such as a hydroxy group is attached to the coated surface 2 in the middle of the molecular chain. When these fluorinated polyethers have the same molecular weight, in FIG. 2, one molecule adheres to the coated surface at two points, whereas in FIG. 1, one molecule adheres to the coated surface at three points. To do. Therefore, as can be seen from a comparison between FIG. 1 and FIG. 2, the distance (indicated by L in FIGS. 1 and 2) that the fluorinated polyether according to the present invention separates the molecule from the coated surface is smaller. It becomes.

  As a result of the above examination, in the lubricant, the structural unit of the formula (1), the structural unit of the formula (2), the structural unit of the formula (3), and the structural unit of the formula (4) are bonded to each other through oxygen. It turned out to be.

  Therefore, as a result of the above examination, the structural unit of the formula (1), the structural unit of the formula (2), and the structural unit of the formula (3) The structural units of the formula (4) are bonded to each other through oxygen, the number average molecular weight is 4000 or more and 12000 or less, and the hydroxy groups in the middle of the molecular chain are averaged from 1.0 to 1.0 in one molecule. If it is a lubricant containing 10.0 fluorinated polyethers, it can be considered that the same effect as the above lubricant can be obtained.

-CF ₂ CH ₂ OH (1)
-CF _2- (2)
-CF ₂ CF _2- (3)

一分子中における、式（１）〜（４）の構造単位の数には特に制限はなく、同一の構造単位が連続した部分があってもよい。これらが一分子中複数回現れてもよい。

There is no restriction | limiting in particular in the number of the structural units of Formula (1)-(4) in 1 molecule, There may exist the part which the same structural unit continued. These may appear several times in one molecule.

  In any of the above cases, the number of hydroxy groups in the middle of the molecular chain is preferably 1.0 to 10.0 on average per molecule, and more preferably 1.0 to 5.0. If it is less than 1.0, the film thickness for one molecule tends to be thick. In a typical case, the film thickness for one molecule may exceed 2 nm. Even if the number exceeds 10.0, no particular improvement effect is obtained. 16 and 17 show structural examples of molecules having 1 to 3 hydroxy groups in the middle of the molecular chain. 16 and 17, x is a positive integer.

  Within the above range, as long as the adhesion to the coated surface is successful, the distance L from which the fluorinated polyether according to the present invention is separated from the coated surface has a polar group only at the end, and the above polar group It can be considered that the fluorinated polyether having the same value as the molecular weight of the structure portion between them as the molecular weight as a whole molecule is approximately the same as the distance L away from the coated surface.

  In addition, the molecular weight of the structural part between any polar group (hydroxy group) in the fluorinated polyether and any polar group (hydroxy group) adjacent to the polar group in the connection of the molecular chain is the same as M1 When the molecular weight of the structural portion between any other polar group on the molecule and any polar group adjacent to the polar group in the connection of the molecular chain is M2, | M1-M2 | ≦ 1000 It turned out to be preferable. If it is in such a range, as long as the adhesion to the coated surface is successful, the structure portion between any polar group and the polar group adjacent to this polar group on the molecular chain connection is removed from the coated surface. It is possible to keep the variation in the distance L away as small as about 0.3 nm.

  In addition, as will be described later, the molecular weight of the structural portion between the adjacent polar groups is preferably 3000 or less when the average molecular value exceeds 3000 and the thickness of the lubricating layer exceeds 3000. It has been found.

  In the above description, an arbitrary polar group on the same molecule and a polar group adjacent to the polar group in connection of molecular chains mean adjacent Z in FIG. 3, for example. It does not mean polar groups that are spatially adjacent to each other. The molecular weight is a number average molecular weight. In addition, the molecular weight of the structural portion between the polar groups adjacent to the polar group in connection with the molecular chain is counted in consideration of the molecular weight of the polar group concerned. For example, it counts about the part enclosed by the ellipse in FIG.

  As described above, the molecular weight of the fluorinated polyether according to the present invention is in the range of 4000 to 12000 in terms of number average molecular weight. If it is less than 4000, the migration characteristics as indicated by the durability at a high temperature and the reduction rate of the film thickness deteriorate. Moreover, the tendency which becomes easy to scatter at the time of high speed rotation appears. If it exceeds 12000, the viscosity is too high, and the above-described magnetic recording medium or head tends to deteriorate in durability at low temperatures.

  The lubricant according to the present invention may be composed of only the above fluorinated polyether, but may contain other compounds. The other compound is preferably a fluorine compound other than the fluorinated polyether. These fluorine-based compounds are desirably those having characteristics required as a lubricant with respect to molecular weight, fluorine content, and the like. Such a fluorine-based compound is preferably at least one compound selected from the group consisting of formula (5), formula (6), and formula (7).

R ¹ CF ₂ O— (CF ₂ CF ₂ O) _p — (CF ₂ O) _q —CF ₂ —R ² .. (5)
R ¹ —O— (CF ₂ CF ₂ CF ₂ O) _r —CF ₂ CF ₂ —R ² .. (6)

（上式中、Ｒ¹，Ｒ²は、互いに独立に、かつ各式について独立に、ヒドロキシ基、カルボキシ基、アミノ基およびフォスファゼン環、ならびに、ヒドロキシ基、カルボキシ基、アミノ基およびフォスファゼン環からなる群から選ばれた基を置換基として一個以上含み、カルボニル基またはエーテル基またはカルボニル基とエーテル基とを含んでいてもよく、二重結合または三重結合または二重結合と三重結合とを含んでいてもよく、枝分かれしていてもよい一価の脂肪族炭化水素基、ならびに、ヒドロキシ基、カルボキシ基、アミノ基およびフォスファゼン環からなる群から選ばれた基を置換基として一個以上含む一価の芳香族炭化水素基および一価の複素環式芳香族炭化水素基からなる群から選ばれた基であり、ｐ，ｑ，ｒ，ｓは、任意の正の整数である。式（５）、式（６）および式（７）の各構造単位は、各化合物の構造中ランダムに配列できる。）
より具体的には、図４〜６の構造のフッ素化ポリエーテルを例示することができる。なお、図４〜６中ｘは、互いに独立な任意の正の整数である。このようなフッ素化ポリエーテルを含有させると流動性や摩擦特性の微調整ができ、ＨＤＩ特性の最適化が可能になる。なお、各構造単位を各化合物の構造中ランダムに配列できるとは、図４〜６に示すような種々の構造が可能であることを意味する。

(In the above formula, R ¹ and R ² are independently of each other and independently of each other, each consisting of a hydroxy group, a carboxy group, an amino group, and a phosphazene ring, and a hydroxy group, a carboxy group, an amino group, and a phosphazene ring. It contains one or more groups selected from the group as a substituent, may contain a carbonyl group, an ether group, or a carbonyl group and an ether group, and contain a double bond, a triple bond, or a double bond and a triple bond. And a monovalent aliphatic hydrocarbon group which may be branched, and a monovalent aliphatic hydrocarbon group, and a monovalent group containing one or more groups selected from the group consisting of a hydroxy group, a carboxy group, an amino group and a phosphazene ring as a substituent. A group selected from the group consisting of an aromatic hydrocarbon group and a monovalent heterocyclic aromatic hydrocarbon group, and p, q, r, and s are arbitrary Positive integer. Equation (5), equations (6) and the structural unit (7) can be arranged in the structure of the random of each compound.)
More specifically, the fluorinated polyether having the structure shown in FIGS. 4 to 6 are arbitrary positive integers independent of each other. When such a fluorinated polyether is contained, the fluidity and friction characteristics can be finely adjusted, and the HDI characteristics can be optimized. In addition, that each structural unit can be randomly arranged in the structure of each compound means that various structures as shown in FIGS. 4 to 6 are possible.

  The lubricant according to the present invention can be suitably used for a lubricating layer provided on a magnetic recording medium or a head slider for a magnetic recording apparatus. That is, a magnetic recording medium comprising a magnetic layer, a protective layer on the magnetic layer, and a magnetic recording medium lubricating layer on the protective layer, wherein the magnetic recording medium lubricating layer is coated with the lubricant. A magnetic recording medium, and a head slider provided with a head for recording and / or reproducing with respect to the magnetic recording medium, the head slider surface facing the magnetic recording medium having a protective layer and the above-mentioned The head slider having the head slider lubricant layer coated with the lubricant can make the lubricant layer very thin, and can cope with a narrow head flying height.

  In this case, both the magnetic recording medium lubricating layer and the head slider lubricating layer are heated after application of the lubricant in order to improve the surface uniformity of the lubricant applied to the coated surface and the adhesion to the coated surface. It is preferable to process. As the heat treatment, the environmental temperature is preferably in the range of 70 to 150 ° C. and in the range of 0.5 to 2 hours. It is also preferable to carry out an ultraviolet irradiation treatment after applying the lubricant. Either one or both of the heat treatment and the ultraviolet irradiation treatment may be performed. In order to improve the adhesion to the surface to be coated, it is preferable to employ both methods and perform the ultraviolet irradiation treatment after the heat treatment.

  The material for forming the magnetic recording medium to which the lubricant according to the present invention is applied and the application surface of the head slider is not particularly limited and can be appropriately selected from known materials. It is generally preferred to have an affinity of

  The magnetic recording apparatus according to the present invention will be described as a hard disk apparatus as follows. However, the “magnetic recording apparatus” according to the present invention can include all magnetic recording apparatuses that use a magnetic recording medium or a head slider as long as they do not contradict the spirit of the present invention.

  21 is a schematic plan view showing the internal structure of the hard disk device, and FIG. 22 is a schematic cross-sectional view showing the relationship between the head and the magnetic recording medium (cut in a direction perpendicular to the magnetic layer of the magnetic recording medium). Figure).

  As shown in FIG. 21, the hard disk drive includes a magnetic slider 11 having a magnetic recording medium 11 and a head, a rotation control mechanism (for example, a spindle motor) 3 of the magnetic recording medium 11, a head positioning mechanism 4, and recording / reproducing signal processing. A circuit (read / write amplifier, etc.) 5 is a main component.

  As shown in FIG. 22, the head slider 212 is connected to the head positioning mechanism 4 by a suspension 6 and a gimbal 7 for flexibly supporting the head slider 212, and a head 8 is provided at the tip thereof. . A head slider protective layer 9 and a head slider lubricating layer 10 are provided on the head slider surface.

  The magnetic recording medium 11 includes a substrate 12, a Cr underlayer 13, a magnetic layer 14, a magnetic recording medium protective layer 15, and a magnetic recording medium lubricating layer 16 from the lower side of FIG. Although other layers such as a seed layer may be provided, they are omitted in this figure.

Next, examples of the present invention will be described in detail.
[Example 1]

(Synthesis of lubricant)
Aqueous solution of 0.11 mol of sodium hydroxide in 5 g of water was added to 500 mL of acetone and 100 g of commercial FOBLIN Z DOL (manufactured by Solvay Solexis, molecular weight 2020) and 0.125 mol of epichlorohydrin were stirred well. The solution was added dropwise over 10 minutes and heated to reflux for 8 hours.

  Thereafter, acetone was evaporated by an evaporator, 25 g of trifluoroacetic acid and 250 mL of water were added, and the mixture was stirred at 70 ° C. for 3 hours. The precipitate was collected and washed with 80 ° C. water.

The molecular structure was determined by FTIR, ¹ HNMR, ¹³ CNMR, ¹⁹ FNMR. The spectrum obtained in FIGS. ^{According to 19} FNMR, the number average molecular weight is 4653, the average degree of polymerization is 2.14, and the average value of the number average molecular weight (M1, M2,...) Of each main chain unit (structure portion between adjacent hydroxy groups) is 1980. It was decided.

  Furthermore, using a supercritical fluid of carbon dioxide, the lubricant obtained by synthesis was dissolved and extracted while changing the temperature and pressure. Number average molecular weight (Mn) of extracted lubricant, average degree of polymerization (r), number average molecular weight (Mc) of each main chain unit (M1, M2,...), And average number of hydroxy groups per molecule Are summarized in Table 1 together with the fraction names (Fr1 to Fr7).

  As a typical example, in Fr4, the average value of the number of each structural unit per molecule is as follows: the structural unit of formula (1) is 2, the structural unit of formula (2) is 11, and the structural unit of formula (3) is 11.8 and the structural unit of formula (4) was found to be 1.1.

In addition, it was confirmed by FTIR, ¹ HNMR, ¹³ CNMR, and ¹⁹ FNMR that the FOMBLIN Z DOL used in this example had the structure of the formula (8).

[実施例２]

[Example 2]

(Measurement of film thickness for one molecule)
As shown in Non-Patent Document 2, the film thickness for one molecule appears when the lubricant flows by observing a change in the cross-sectional profile of the lubricant film thickness with an ellipsometer. Can be known from the terrace structure A as shown in FIG.

  A lubricant of Fr4 was applied to a part of the protective layer of the hard disk by an immersion method, and the change over time in the cross-sectional profile of the lubricant film thickness was observed. As a result, as shown in FIG. 11, a terrace structure appeared, and the film thickness of the terrace was determined to be 1.74 nm (that is, the film thickness for one molecule). Note that a smaller value on the left side in FIG. 11 represents a protective layer surface to which no lubricant is applied. Moreover, the value larger than the terrace structure on the right side is considered to mean a film thickness configuration of two or more molecules.

  In the case of FOBLIN Z DOL (molecular weight 2022) obtained in the same manner, it was 1.66 nm. That is, it was found that the film thickness of one molecule of the fluorinated polyether according to Example 1 is approximately the same, although the molecular weight is twice or more that of FOMBLIN Z DOL. This is considered because the polar group of the lubricant is adsorbed toward the substrate.

  Accordingly, the molecular layer thickness obtained by the ellipsometer as described above is plotted in FIG. 18 with respect to the number average molecular weight (Mc) of each main chain unit (M1, M2,...).

  As a result, it was presumed that when the molecular weight was increased to about 3000, the molecular layer thickness could reach 2.5 nm. Since the normal coating thickness is about 80% of the molecular layer thickness, when Mc is about 3000, the coating thickness is 2 nm. That is, it can be understood that setting the molecular weight of Mc to about 3000 is not only undesirable in view of the contribution of magnetic spacing, but is also not preferable in that stable flying of the head cannot be obtained. Therefore, in terms of Mc, it can be considered that 3000 or less is an acceptable range.

In addition, it was judged that the coverage to a to-be-coated surface was enough from the measurement result of surface free energy. The surface energy value was 23 mN / m in the case of FOMBLIN Z DOL and 18 mN / m in the case of the fluorinated polyether of Fr4 according to Example 1, and a sufficiently low surface energy state was obtained.
[Example 3]

(Evaluation of flying characteristics)
The lubricant (Fr4) of Example 2 obtained in Example 1 was applied to the protective layer of the hard disk by an immersion method, and a glide test was performed as an evaluation of the floating characteristics. The coating thickness of the lubricant was 1.2 nm, and heat treatment was performed at an environmental temperature of 130 ° C. for 50 minutes.

  In this test, while rotating a disk at a peripheral speed of 8.6 m / s, a slider equipped with a piezo element is levitated at a height of 6 nm, and the output of the piezo element is monitored.

As a comparison, a similar test was performed on a commercially available disc having a recording density of 38 Gbit / inch ² (converted value was 5.89 Gbit / cm ² ). As shown in FIGS. 12 and 13, there is no difference between the two, and the magnetic disk using the lubricant according to the present invention for the lubricating layer showed good flying characteristics. 12 and 13, the horizontal axis represents the radial position of the disk, and the vertical axis represents the output voltage of the piezo element. A and B indicate the surfaces of the disc.
[Example 4]

(Evaluation of flying characteristics)
A take-off speed (TOV) and a touch-down speed (TDV) were measured using a CSS (contact-start-stop) tester. TOV is the speed at which the head flies when the rotational speed of the disk is increased, and TDV is defined as the speed at which the head collides with the disk when the rotational speed of the disk is decreased.

  The head used was a head having a flying height of 10 nm. In the magnetic disk used, a lubricant (Fr4) was used for the magnetic recording medium lubricating layer. The coating thickness was 1.2 nm, and heat treatment was performed in the same manner as in Example 3.

As a comparison, the same test was performed on a commercially available disc having a recording density of 38 Gbit / inch ² (converted value was 5.89 Gbit / cm ² ). The results are shown in FIGS. There was no difference between the two, and good floating characteristics were exhibited. 14 and 15, the horizontal axis represents the position in the radial direction of the disk, and the vertical axis represents the rotational speed of the disk.
[Example 5]

(Low temperature characteristics)
The lubricants (Fr1 to Fr7) of Example 1 were applied to the protective layer of the hard disk by an immersion method, and a CSS (contact-start-stop) test was performed as an evaluation of the low temperature characteristics. The coating thickness of the lubricant was 1.2 nm, and heat treatment was performed at an environmental temperature of 130 ° C. for 50 minutes.

CSS was repeated at an ambient temperature of 5 ° C. As a result, although Fr1 to Fr6 operated without any trouble even at the standard value of 50000 times or more, Fr7 led to a head crash after about 38000 times. That is, when the molecular weight exceeded 12,000, durability at low temperature was remarkably lowered. This is because the viscosity at a low temperature is remarkably increased as shown in FIG.
[Example 6]

(High temperature characteristics)
The lubricants (Fr1 to Fr7) of Example 1 were applied to the protective layer of the hard disk by the dipping method, and a CSS test was performed as an evaluation of high temperature characteristics. The coating thickness of the lubricant was 1.2 nm, and heat treatment was performed at an environmental temperature of 130 ° C. for 50 minutes.

CSS was repeated at an ambient temperature of 70 ° C. As a result, from Fr4 to Fr7, the motor operated without any trouble even at the standard value of 50000 times or more, but in Fr1, Fr2, Fr3 and FOMBLIN Z DOL, head crash occurred at 40000 times or less. That is, when the molecular weight is less than 4000, the durability at high temperature is remarkably lowered.
[Example 7]

(Migration characteristics)
The lubricant (Fr4 to Fr6) prepared in Example 1 and FOMBLIN Z DOL (molecular weight 2020) were applied to the protective layer of the hard disk by a dipping method, and applied to a thickness of 1.3 nm.
This disk was fixed to a spindle and kept rotating at a rotation speed of 10,000 rpm for 300 hours in an environment of 80 ° C. and 50% RH. Thereafter, the film thickness was measured at a radius of 32 mm from the center of the disk, and the reduction rate of the film thickness was determined. The results are shown in FIG. The reduction rate is desirably 35% or less, and it was found that this condition is not satisfied when the molecular weight is less than 4000.

  In addition, the invention shown to the following additional remarks can be derived from the content disclosed above.

(Appendix 1)
The structural unit of formula (1) having a hydroxy group, the structural unit of formula (2), the structural unit of formula (3), and the structural unit of formula (4) having a hydroxy group are bonded to each other via oxygen. A lubricant containing a fluorinated polyether having a number average molecular weight of from 4,000 to 12,000 and having an average of 1.0 to 10.0 hydroxy groups in the middle of the molecular chain in one molecule.

-CF ₂ CH ₂ OH (1)
-CF _2- (2)
-CF ₂ CF _2- (3)

（付記２）
式（８）の化合物（式（８）中ｘは、互いに独立に任意の正の整数である。）とエピクロロヒドリンとを反応させてなり、数平均分子量が４０００以上１２０００以下で、かつ、分子鎖の途中のヒドロキシ基を、一分子中に平均して１．０〜１０．０個有するフッ素化ポリエーテルを含有する潤滑剤。

(Appendix 2)
A compound of formula (8) (in formula (8), x is an arbitrary positive integer independently of each other) and epichlorohydrin are reacted, and the number average molecular weight is 4000 or more and 12000 or less, and A lubricant containing a fluorinated polyether having an average of 1.0 to 10.0 hydroxy groups in the middle of the molecular chain in one molecule.

HOCH ₂ CF ₂ O (CF ₂ CF ₂ O) _x (CF ₂ O) _x CF ₂ CH ₂ OH (8)
(Appendix 3)
The lubricant according to appendix 1 or 2, having an average of 1.0 to 5.0 hydroxy groups in the middle of the molecular chain.

(Appendix 4)
The lubricant according to any one of appendices 1 to 3, wherein the average value of the number average molecular weight of the structural portion between adjacent hydroxy groups is 3000 or less.

(Appendix 5)
The lubricant according to any one of appendices 1 to 4, containing a fluorine-based compound other than the fluorinated polyether.

(Appendix 6)
The lubricant according to appendix 5, wherein the fluorine-based compound is at least one compound selected from the group consisting of formula (5), formula (6), and formula (7).

R ¹ CF ₂ O— (CF ₂ CF ₂ O) _p — (CF ₂ O) _q —CF ₂ —R ² .. (5)
R ¹ —O— (CF ₂ CF ₂ CF ₂ O) _r —CF ₂ CF ₂ —R ² .. (6)

（上式中、Ｒ¹，Ｒ²は、互いに独立に、かつ各式について独立に、ヒドロキシ基、カルボキシ基、アミノ基およびフォスファゼン環、ならびに、ヒドロキシ基、カルボキシ基、アミノ基およびフォスファゼン環からなる群から選ばれた基を置換基として一個以上含み、カルボニル基またはエーテル基またはカルボニル基とエーテル基とを含んでいてもよく、二重結合または三重結合または二重結合と三重結合とを含んでいてもよく、枝分かれしていてもよい一価の脂肪族炭化水素基、ならびに、ヒドロキシ基、カルボキシ基、アミノ基およびフォスファゼン環からなる群から選ばれた基を置換基として一個以上含む一価の芳香族炭化水素基および一価の複素環式芳香族炭化水素基からなる群から選ばれた基であり、ｐ，ｑ，ｒ，ｓは任意の正の整数である。式（５）、式（６）および式（７）の各構造単位は、各化合物の構造中ランダムに配列できる。）
（付記７）
磁性層と、当該磁性層上にある保護層と、当該保護層上にある磁気記録媒体潤滑層とを含む磁気記録媒体であって、当該磁気記録媒体潤滑層が付記１〜６のいずれかに記載の潤滑剤を塗布したものである、磁気記録媒体。

(In the above formula, R ¹ and R ² are independently of each other and independently of each other, each consisting of a hydroxy group, a carboxy group, an amino group, and a phosphazene ring, and a hydroxy group, a carboxy group, an amino group, and a phosphazene ring. It contains one or more groups selected from the group as a substituent, may contain a carbonyl group, an ether group, or a carbonyl group and an ether group, and contain a double bond, a triple bond, or a double bond and a triple bond. And a monovalent aliphatic hydrocarbon group which may be branched, and a monovalent aliphatic hydrocarbon group, and a monovalent group containing one or more groups selected from the group consisting of a hydroxy group, a carboxy group, an amino group and a phosphazene ring as a substituent. A group selected from the group consisting of an aromatic hydrocarbon group and a monovalent heterocyclic aromatic hydrocarbon group, and p, q, r, and s are arbitrary Of an integer. Equation (5), each structural unit of the formula (6) and (7) can be arranged in the structure of the random of each compound.)
(Appendix 7)
A magnetic recording medium comprising a magnetic layer, a protective layer on the magnetic layer, and a magnetic recording medium lubricating layer on the protective layer, wherein the magnetic recording medium lubricating layer is any one of appendices 1 to 6 A magnetic recording medium coated with the described lubricant.

(Appendix 8)
The magnetic recording medium according to appendix 7, wherein the magnetic recording medium is heat-treated after application of the lubricant.

(Appendix 9)
The magnetic recording medium according to appendix 7 or 8, wherein the magnetic recording medium has been subjected to an ultraviolet irradiation treatment after application of the lubricant.

(Appendix 10)
A head slider including a recording conversion element for recording and / or reproducing with respect to a magnetic recording medium,
A head slider having a head slider lubricating layer coated with the protective layer and the lubricant according to any one of supplementary notes 1 to 6 on a head slider surface facing the magnetic recording medium.

(Appendix 11)
The head slider according to appendix 10, wherein the head slider is heat-treated after application of the lubricant.

(Appendix 12)
12. The head slider according to appendix 10 or 11, which has been subjected to ultraviolet irradiation treatment after application of the lubricant.

(Appendix 13)
A magnetic recording apparatus comprising the magnetic recording medium according to any one of appendices 7 to 9 and the head slider according to any one of appendices 10 to 12.

3 is a schematic diagram showing a state in which a fluorinated polyether adheres to a surface to be coated with a polar group Z. FIG. FIG. 5 is another schematic diagram showing a state in which the fluorinated polyether is attached to the coated surface with the polar group Z. FIG. 5 is another schematic diagram showing a state in which the fluorinated polyether is attached to the coated surface with the polar group Z. It is a figure which illustrates the compound structure which belongs to Formula (5). It is a figure which illustrates the compound structure which belongs to Formula (6). It is a figure which illustrates the compound structure which belongs to Formula (7). 2 is an FT-IR chart of the compound obtained in Example 1. FIG. 2 is a ¹ HNMR chart of the compound obtained in Example 1. FIG. 3 is a ¹³ C NMR chart of the compound obtained in Example 1. FIG. 2 is a ¹⁹ FNMR chart of the compound obtained in Example 1. FIG. It is a chart which shows the cross-sectional profile of the lubricant film thickness in an ellipsometer. It is a chart showing the result of a glide test. It is another chart showing the result of a glide test. It is a chart showing the test result of TDV and TOV. It is another chart showing the test result of TDV and TOV. It is a figure which illustrates the structure of the fluorinated polyether which concerns on this invention. It is another figure which illustrates the structure of the fluorinated polyether which concerns on this invention. It is a graph which shows the relationship between the number average molecular weight (Mc) of the structure part between adjacent hydroxy groups, and a molecular one layer film thickness. It is a graph which shows the temperature characteristic of the viscosity of each lubricant. It is a graph which shows the relationship between a migration characteristic (decrease rate of a film thickness) and molecular weight. 2 is a schematic plan view showing an internal structure of the hard disk device. FIG. It is a typical cross-sectional view showing the relationship between the head of the hard disk device and the magnetic recording medium.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fluorinated polyether 2 Coating surface 3 Rotation control mechanism 4 Head positioning mechanism 5 Recording / reproduction signal processing circuit 6 Suspension 7 Gimbal 8 Head 9 Head slider protective layer 10 Head slider lubricating layer 11 Magnetic recording medium 12 Substrate 13 Cr Base layer 14 Magnetic layer 15 Magnetic recording medium protective layer 16 Magnetic recording medium lubricating layer 17 Ni-P plating layer 212 Head slider

Claims (5)

The structural unit of formula (1) having a hydroxy group, the structural unit of formula (2), the structural unit of formula (3), and the structural unit of formula (4) having a hydroxy group are bonded to each other via oxygen. A lubricant containing a fluorinated polyether having a number average molecular weight of from 4,000 to 12,000 and having an average of 1.0 to 10.0 hydroxy groups in the middle of the molecular chain in one molecule.
-CF ₂ CH ₂ OH (1)
-CF _2- (2)
-CF ₂ CF _2- (3)

A compound of formula (8) (in formula (8), x is an arbitrary positive integer independently of each other) and epichlorohydrin are reacted, and the number average molecular weight is 4000 or more and 12000 or less, and A lubricant containing a fluorinated polyether having an average of 1.0 to 10.0 hydroxy groups in the middle of the molecular chain in one molecule.
HOCH ₂ CF ₂ O (CF ₂ CF ₂ O) _x (CF ₂ O) _x CF ₂ CH ₂ OH (8)   The lubricant according to claim 1 or 2, having an average of 1.0 to 5.0 hydroxy groups in the middle of the molecular chain in one molecule.   A magnetic recording medium comprising a magnetic layer, a protective layer on the magnetic layer, and a magnetic recording medium lubricating layer on the protective layer, wherein the magnetic recording medium lubricating layer is any one of claims 1 to 3. A magnetic recording medium to which the lubricant described in 1 is applied. A head slider including a recording conversion element for recording and / or reproducing with respect to a magnetic recording medium,
A head slider having a head slider lubricant layer coated with the protective layer and the lubricant according to any one of claims 1 to 3 on a head slider surface facing the magnetic recording medium.

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