JP2010003350A - Lubricant for magnetic recording mediums, magnetic recording medium, and magnetic recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lubricant which can achieve any of: an effect which can keep a friction coefficient of magnetic recording medium face low; an effect which can reduce evaporation of the lubricant; an effect which can suppress migration of the lubricant by rotation of disk; or an effect which can enhance reliability, especially long-term reliability of the magnetic recording medium by suppressing intrusion of a volatile organic substance or the like. <P>SOLUTION: The lubricant having large temperature dependence of viscosity is used. It is desirable to use a magnetic recording device which can heat a write object area and a read object area. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a lubricant for a magnetic recording medium, a magnetic recording medium using the lubricant, and a magnetic recording apparatus.

  With the expansion of digital content, hard disk drives (HDDs) have become widespread not only in personal computers but also in various fields such as car navigators with hard disk recorders, and the capacity of HDDs has been increased to record more information. Is required.

  The recording part of the hard disk device is mainly composed of a magnetic head for reading and writing information and a magnetic recording medium for storing information. In the magnetic recording medium, a lubricating layer is provided on the protective layer for the purpose of reducing the coefficient of friction with the magnetic head and alleviating the impact during intermittent contact with the head.

  This is shown in FIGS. FIG. 1 is a schematic plan view showing the internal structure of the hard disk device, and FIG. 2 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. 1, the hard disk device includes a magnetic recording medium 1 and a head slider 2 having a head, a rotation control mechanism (for example, a spindle motor) 3 of the magnetic recording medium 1, a head positioning mechanism 4, and a recording / reproducing signal processing. A circuit (read / write amplifier, etc.) 5 is a main component.

  As shown in FIG. 2, the head slider 2 is connected to the head positioning mechanism 4 by a suspension 6 and a gimbal 7 for flexibly supporting the head slider 2, 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 1 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.

  This magnetic recording medium lubricating layer is a liquid thin film, and has a drawback that it easily evaporates due to the rotation of the disk and environmental changes in the drive.

  As another problem, a phenomenon called migration is known. As the magnetic recording medium rotates faster every year, the speed of reading and writing of information increases, so the speed of recording and playback of information is increasing. At present, the speed reaches 15000 rpm, but the lubricant on the surface of the magnetic recording medium may move from the central portion toward the peripheral portion as the magnetic recording medium rotates at a high speed. This is a phenomenon called migration. When migration occurs, a shortage of lubricant occurs in the center, which causes various problems due to insufficient lubrication.

  Problems other than insufficient lubrication include insufficient prevention of invasion of volatile organic substances.

  The magnetic recording medium lubricating layer serves to protect the magnetic layer against gases called volatile organic substances present in the hard disk drive. In other words, volatile organic substances penetrate into the magnetic recording medium and cause a chemical reaction with the magnetic substance in the magnetic layer, causing damage such as corrosion, but the lubricant applied to the surface of the magnetic recording medium adheres to the volatile organic substance. And prevents intrusion. If this volatile organic matter intrusion prevention function deteriorates due to evaporation or migration, the reliability of reproduction of the magnetic recording medium, particularly the ability to leave a long-term recording (long-term reliability) is insufficient due to corrosion or the like. come.

  As a recording method for the next-generation HDD, there is a heat-assisted recording method (see, for example, cited documents 1 to 3). In this heat-assisted recording, in order to increase the recording density of the magnetic recording medium, a material having a higher holding force than the conventional one is used for the magnetic recording medium. By increasing the holding force, stable recording can be realized even when the magnetized place is reduced. However, since the holding force is high, the magnetic force of a normal magnetic recording head is too weak, and magnetic information cannot be easily written on the magnetic recording medium. For this reason, the heat-assisted recording method uses the help of heat. That is, since the magnetic material has a property that the holding force decreases as the temperature rises, the heat-assisted magnetic recording apparatus is provided with a mechanism for temporarily heating the recording portion of the magnetic recording medium.

When the magnetic head writes information, the surface of the magnetic recording medium is spot-heated to heat the recording layer portion of the heated magnetic recording medium to a Curie temperature or a temperature close to the Curie temperature, and the holding force is temporarily increased. Decline. Therefore, in the heat-assisted recording method, the magnetic information is written into the magnetic recording medium by the magnetic head while the holding power of the magnetic recording medium recording layer is reduced. This heating is generally called heat irradiation.
JP 2007-184092 A (Claims) JP 2006-12256 A (Claims) JP 2006-155708 A (Claims)

  The following embodiments are intended to provide a novel lubricant capable of eliminating or alleviating the above-mentioned drawbacks and a technique using the lubricant. Still other objects and advantages will become apparent from the following description.

  A lubricant for a magnetic recording medium that does not exhibit fluidity at 25 ° C. but exhibits fluidity at 80 ° C., or a magnetic material having a viscosity at 25 ° C. of 100 Pa · s or more and a viscosity at 80 ° C. of 1 Pa · s or less. By using a lubricant having a large temperature dependency of viscosity, such as a lubricant for a recording medium, a low friction coefficient, a decrease in evaporation of the lubricant, suppression of migration, and suppression of invasion of volatile organic substances can be achieved.

  As a magnetic recording apparatus for using a magnetic recording medium comprising a magnetic recording medium lubricating layer made of this lubricant, the lubricant in the area to be written during and near the write-in area such as a heat-assisted magnetic recording apparatus exhibits fluidity. Or the heating is performed so that the lubricant in the writing target area during writing and the vicinity thereof exhibits fluidity, and the heating is performed in the reading target area during reading and in the vicinity thereof. If an apparatus is employ | adopted, the said effect can be fully exhibited.

  When the lubricant disclosed below is used, the friction coefficient of the magnetic recording medium surface can be kept low during writing and reading of magnetic recording information, the evaporation of the lubricant can be reduced, and the lubricant can be migrated by rotating the disk. It is possible to realize any of the effects that can be suppressed and that the intrusion of volatile organic substances can be suppressed to improve the reliability of the magnetic recording medium, particularly the long-term reliability.

  Further, if a magnetic recording apparatus suitable for the lubricant described below is used, the above effect can be sufficiently exerted.

  Embodiments of the present invention will be described below with reference to the drawings, examples and the like. In addition, these figures, Examples, etc. and description 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.

  It has been found that the above effect can be obtained by using a lubricant having a large temperature dependency of viscosity.

  If such a lubricant is used, the evaporation of the lubricant can usually be reduced due to the high viscosity, and the migration of the lubricant due to the rotation of the disk can be suppressed. In addition, the intrusion of volatile organic substances can be suppressed, and the reliability of the magnetic recording medium, particularly the long-term reliability, can be improved.

  Furthermore, at the time of writing or reading magnetic recording, if the lubricant in the target area and its vicinity is heated so as to exhibit fluidity, the friction coefficient of the magnetic recording medium surface is reduced due to a large decrease in viscosity. Can be kept low.

  As the lubricant having a large temperature dependency of the viscosity, a lubricant having a solid or high-viscosity paste form in the vicinity of room temperature and not exhibiting fluidity and having high fluidity at high temperatures (for example, liquid) is preferable.

  Specifically, when 25 ° C. is considered as a temperature near room temperature and 80 ° C. is considered as a high temperature, it has been found that a lubricant that does not exhibit fluidity at 25 ° C. and exhibits fluidity at 80 ° C. is preferable. It is often more preferable that it is solid at 25 ° C. and liquid at 80 ° C.

  Or it turned out that the viscosity whose viscosity in 25 degreeC is 100 Pa.s or more and whose viscosity in 80 degreeC is 1 Pa.s or less is preferable. More preferably, the viscosity at 25 ° C. is 500 Pa · s or more.

  Or it turned out that the lubricant whose viscosity in 80 degreeC becomes 1000 times or more of the viscosity in 25 degreeC is preferable. A lubricant having a viscosity at 80 ° C. of 10,000 times or more that at 25 ° C. is more preferable.

  Further, a heat-assisted magnetic recording device is specifically known as a magnetic recording device that heats the write target area and its vicinity when writing magnetic recording. A lubricant used for a magnetic recording medium of a heat-assisted magnetic recording apparatus, which exhibits fluidity in and near the region irradiated with heat during the heat irradiation, and does not exhibit fluidity in other portions. It can be said that an agent is preferable. The “near” range of the region irradiated with heat can be determined as appropriate.

  Of course, the above changes are preferably reversible.

  Here, whether or not “fluidity” is indicated may be determined by giving acceleration to the lubricant and determining that there is no fluidity when deformation does not occur, and determining that there is fluidity when deformation occurs. The acceleration at that time may be the acceleration (centrifugal force) under the use conditions of the hard disk. Specifically, for example, when a 3.5-inch diameter (converted value is 8.9 cm) disk is rotated at 10,000 rpm, if the lubricant applied to the surface does not move in nm units after 24 hours, the fluidity It can be determined that there is none, and if there is movement, it can be determined that there is liquidity. In this case, the rotation speed, processing time, etc. may be arbitrarily determined according to the actual situation of the magnetic recording apparatus to be used. However, as long as it is solid, it may be determined that there is no fluidity without such evaluation. Further, if it is liquid, it may be determined that there is fluidity without such evaluation.

  Alternatively, as will be described later, the external appearance of the lubricant is inspected by using a melting point measuring instrument, and the corner of the rectangular parallelepiped of the sample disappears and spreads wet on the sample stage or the surface of the sample with a pin (such as a wire) When injured, the lubricant surface may be confirmed to be fluid by direct visual observation as in the case where the surface of the lubricant is repaired in an instant without being damaged.

  In addition, although the said form is an independent thing, it may be a lubricant which satisfies any or all of it, and it is more preferable in many cases.

  The lubricant described above can be selected from conventional lubricants. From the viewpoint of easily obtaining low friction, the lubricant is a polymer containing fluorine, that is, a fluorine-containing polymer or a polymer having a perfluoro structure can be exemplified. Such polymers generally have a linear molecular structure and often contain ether linkages. In many cases, the polymer has a polar group such as a carboxy group or a hydroxy group at one or both terminal groups. It is known that a polymer having such a structure can have a very thin layer thickness and exhibits good lubricity.

  The lubricant satisfying the above-described form can be obtained by selecting a lubricant satisfying the above-mentioned conditions from the group of lubricants.

Specific examples of the lubricant for selecting the above-mentioned lubricant include tetraol (trade name), which is a fluorine-containing polyether polymer manufactured by Solvay Solexis. The molecular structure of tetraol has a random polymer chain composed of CF ₂ O and CF ₂ CF ₂ O as a main chain, and has hydroxyl groups at both ends. Naturally, tetraol is a mixture containing molecules having a molecular weight distribution and different numbers of terminal hydroxyl groups. Therefore, in the fractionation technique such as supercritical purification, the viscosity characteristics in the lubricant can be freely controlled by controlling the molecular weight and the number of hydroxyl groups in the tetraol.

  This selection may be possible by simply selecting from conventional lubricants, but in general it will be difficult to simply select. This is because when a normal magnetic recording device is used, good lubricity cannot be obtained due to its high viscosity. Therefore, a lubricant that satisfies such a condition is regarded as a lubricant for a magnetic recording device. Because it is not done. Further, in the heat-assisted magnetic recording apparatus, only the search for a lubricant that exhibits favorable characteristics as a lubricant during heat irradiation has been pursued, and the search for a lubricant from the viewpoint disclosed in this specification has not been considered at all. It was because there was not.

  Therefore, this selection can be made by selecting from a broader group of lubricants than the conventional group of lubricants for magnetic recording devices, or by separating extraction, distillation, etc. for a group of lubricants including the group of lubricants for conventional magnetic recording devices. It is practical to take out a fraction using a means, and to perform whether or not the above condition is satisfied for the fraction or a mixture of a plurality of fractions.

  There is no particular limitation on the magnetic recording medium using the lubricant and the magnetic recording apparatus using the magnetic recording medium, but in use, the fluidity can be improved by reaching the writing area or the reading area. From the point of importance, a magnetic recording device having a heating mechanism capable of realizing such a thing and a magnetic recording medium used for a magnetic recording device having such a heating mechanism are preferable.

  Specifically, at the time of writing magnetic recording, the write target region during writing of the magnetic recording medium and the lubricant in the vicinity thereof are heated so as to exhibit fluidity, or at the time of writing magnetic recording, the magnetic The area to be written during writing of the recording medium and its vicinity are heated so that the lubricant exhibits fluidity, and the area to be read and its vicinity during reading of the magnetic recording medium during reading of the magnetic recording A magnetic recording apparatus that is heated to a magnetic recording medium and a magnetic recording medium used in such a magnetic recording apparatus are preferable. The latter condition is more practical because the lubricant exhibits fluidity in both writing and reading.

  Here, the reason why the “write target area during writing” is defined is that heating is not required for the “write target area during writing”. The reason why the “write target area and its vicinity” is defined is that heating does not have to be strictly limited to the “write target area during writing”. Note that the range of “near” can be determined as appropriate.

  Heating is not required in other places, that is, places other than “the write target area being written and its vicinity”. It should be noted that “a write target area that is not being written” is included in places other than “a write target area that is being written and its vicinity”.

  However, a place other than “the write target area during writing and its vicinity” may be heated. For example, a type in which the entire magnetic recording medium is heated may be used. In this case, when the magnetic recording medium is not used, it is possible to improve the reliability, particularly the long-term reliability, of the magnetic recording medium by suppressing the penetration of volatile organic substances. There is also a merit that can be simplified in terms of equipment.

  The heating may be simple heating such as simply heating a space in which the magnetic recording medium is located, or may heat only the target region, the target region, and the vicinity thereof. There is no restriction | limiting in particular in the supply method of heat. Any heating mechanism can be employed.

  Although there is no restriction | limiting in particular about heating temperature, Generally, if it is less than 200 degreeC, there is no problem. 100 degrees C or less is more preferable, and the range of 60-90 degreeC is the most preferable. When the temperature is 55 ° C. or lower, it is difficult to produce a difference in fluidity of the lubricant. This heating temperature means a temperature realized in “the write target area during writing and its vicinity”. It is not necessary to heat places other than “the target area to be written and its vicinity” (this place includes “the target area to be written and its vicinity”). You may be affected.

  When the magnetic recording device is a heat-assisted magnetic recording device, at the time of writing the magnetic recording, heat irradiation is performed so that the lubricant in the writing target area during writing of the magnetic recording medium and the lubricant in the vicinity thereof show fluidity, or When the magnetic recording is written, the magnetic recording medium is read while the magnetic recording medium is being heated so that the lubricant in the writing target area during writing and the lubricant in the vicinity thereof is fluid. It is preferable that heat irradiation is performed on the reading target area and its vicinity. The meanings of “target region” and “near” are the same as described above. There is no restriction | limiting in particular about the system of heat irradiation, The conventional system can be employ | adopted. In the former case, a method of heating the entire magnetic recording medium may be adopted when reading the magnetic recording.

  The state of heat irradiation in the case of a heat-assisted magnetic recording apparatus will be schematically described below. In the following, the expressions “lubricant that does not exhibit fluidity” and “lubricant that exhibits fluidity” are employed, but this is for the sake of simplification. You are not restricted.

  FIG. 3 (1) shows a schematic side view of the magnetic recording medium. In FIG. 3 (1), the lubricant of the lubricating layer 16 present on the protective film 15 is present as a lubricant that does not exhibit fluidity because it is not irradiated with heat. Therefore, even when the magnetic recording medium rotates at high speed, the movement of the lubricant in the outer peripheral direction, called migration, is difficult to occur. In addition, the lubricant that does not exhibit fluidity can suppress the invasion of volatile organic substances and improve the reliability of the magnetic recording medium, particularly the long-term reliability. In the figure, the structure under the protective film 15 is omitted.

  (2) in FIG. 3 shows a state in which heat is spot-irradiated from the magnetic head 2 to the magnetic recording medium. Reference numeral 31 represents a region of heat irradiation. In this figure, the heat generating device is incorporated in the head, but it may not be incorporated in the head. The thermal irradiation is performed so as to reach the magnetic layer, and a part thereof is used to heat the magnetic recording medium when passing through the magnetic recording medium. Therefore, the heat at the time of heat assist can be effectively utilized.

  By the heat irradiation, the lubricant on the surface of the magnetic recording medium in the region 31 under heat irradiation (this region corresponds to the write target region during writing and the vicinity thereof) becomes fluid. In this way, the lubricity necessary for writing is ensured.

  FIG. 3 (3) shows a state in which the head approaches the surface of the magnetic recording medium in this state. Even if such a thing happens, since the lubricant exhibits sufficient lubricity, troubles such as head crashes are less likely to occur.

  Further, the evaporation of the lubricant can be reduced by limiting the heated area. Further, the migration of the lubricant due to the rotation of the disk can be suppressed.

  There is no restriction | limiting in particular about the temperature of heat irradiation. In the case of a normal assist magnetic recording apparatus, the temperature is 200 to 500 ° C. on the surface of the magnetic recording medium.

  In heat-assisted magnetic recording devices, it is normal not to perform such heat irradiation during normal reading, but when the lubricant according to this embodiment is employed, such heating is also performed during reading. Is preferred. However, at the time of magnetic information reproduction, if it is heated more than necessary, the demagnetization due to a decrease in the coercive force of the magnetic layer occurs at the same time as the change of the lubricant to a high fluidity state. It is not preferable to make it.

  Needless to say, temperature control of heat is important. Therefore, the change in state due to the heat of the lubricant must be a temperature lower than the holding power lowering temperature of the heat-assisted recording. Specifically, it can be said that the surface temperature of the magnetic recording medium at the time of reading is desirably lower than the heat assist temperature. Since it is 200-500 degreeC in the magnetic recording medium surface at the time of heat-assisted recording, less than 200 degreeC is preferable, 100 degrees C or less is more preferable, and the range of 60-90 degreeC is the most preferable. When the temperature is 55 ° C. or lower, it is difficult to produce a difference in fluidity of the lubricant.

  Next, examples and comparative examples of the present invention will be described in detail.

[Example 1]
The temperature dependence of the viscosity was investigated using a rotational viscometer VAR100 manufactured by Rheologicala. About 300 μL of a lubricant was sandwiched between the rotating cone and the fixed stage, and measurement was performed while changing the temperature between 20 ° C. and 80 ° C. using a Peltier temperature controller with a constant rotation speed.

  As a conventional lubricant, TETRAOL (manufactured by Solvay Solexis) was used. The lubricant of the present invention was obtained by setting TETRAOL on an extraction column and extracting with a supercritical fluid using carbon dioxide. The supercritical extraction conditions were an extraction temperature of 60 ° C., and the target lubricant was obtained under an extraction pressure of more than 25 MPa and not more than 30 MPa. Since a low-viscosity lubricant is obtained in the fraction of 25 MPa or less, first, the low-viscosity lubricant was removed under conditions of 25 MPa or less. Moreover, since the ultrahigh viscosity lubricant obtained by the pressure exceeding 30 MPa remains in the extraction column, only the desired lubricant can be extracted.

  The viscosity of the conventional product and the present invention both decreased as the temperature increased. The viscosity value of the lubricant of the present invention was 2 to 3 orders of magnitude larger than the viscosity value of the conventional product at 25 ° C., showing an overwhelmingly high value. However, at 80 ° C., the viscosity value of the lubricant of the present invention is larger than the viscosity value of the conventional product, but the magnitude is one digit or less.

  Furthermore, changes in the state of the lubricant of the present invention due to heat were observed with the naked eye. Specifically, the external appearance inspection of the lubricant was carried out using a melting point measuring device (manufactured by AS ONE, ATM-01). A sample approximately 3 mm in rectangular parallelepiped was set on the sample stage of the melting point measuring instrument. At room temperature, the corners of the rectangular parallelepiped were visually confirmed.

  The sample was gradually heated from room temperature (25 ° C.) to 80 ° C. over about 10 minutes. At 80 ° C., the corners of the rectangular parallelepiped disappeared and the lubricant spread on the sample stage. When the lubricant surface was injured with a pin (such as a wire) at 80 ° C., the lubricant surface was repaired within an instant (within 1 second) without being damaged. Also, as a matter of course, in the lubricant at 25 ° C. before heating, when injured, the lubricant was hard and was not repaired within 1 second, and the injured scratch was kept. When the lubricant once heated to 80 ° C. was lowered to room temperature and was injured, it was not repaired and the scratches were kept.

  The lubricant of the present invention is in the form of a grease that is nearly solid at 25 ° C., and at 50 ° C., it gradually transitions to a low fluidity grease state and to a low fluidity state in the temperature range of 50 ° C. to 60 ° C. I confirmed that. Furthermore, in a state higher than 60 ° C. (for example, 80 ° C.), the liquid state changed to a highly fluid state.

  On the contrary, when the temperature of the lubricant was gradually lowered from 80 ° C., the fluidity was high at a temperature of 60 ° C. or higher, but the change in state was confirmed in the range of 60 ° C. to 50 ° C. It changed to the grease state with low fluidity at the following temperatures. In other words, with a temperature range of 50 ° C. to 60 ° C. as a boundary, the fluidity is high at a high temperature, the fluidity is low or the fluidity is low at a low temperature, and this state change is reversible. It was confirmed. For example, it is an image where butter (of food) melts at a temperature higher than 50 ° C. The results are shown in FIG. Data other than 25 ° C and 80 ° C were omitted.

  By using a magnetic recording medium that uses a lubricant that causes a change in state due to such a temperature change, in the temperature range where the lubricant exists in a solid state, the rotation of the disk as occurs with conventional liquid lubricants. It is possible to suppress the movement of the lubricant in the outer peripheral direction due to the so-called migration. Furthermore, since the lubricant having a low fluidity is particularly easy to prevent the invasion of volatile organic substances, it is possible to prevent troubles such as corrosion due to a chemical reaction between the volatile organic substances and the magnetic substances, and the magnetic recording medium. Reliability, particularly long-term reliability, can be improved.

  In addition, the head slider and the magnetic recording medium may come into contact with each other as long as the writing target area being written and its vicinity or the reading target area being read and its vicinity are heated by a heat-assisted recording method or the like. Since only the area is heated and the lubricant melts only in that area and exhibits lubricity, the action as a lubricant is sufficiently ensured.

[Example 2]
The lubricant of Example 1 and a conventional lubricant were applied to a 2.5 inch glass disk having a film thickness of 1.5 nm and having a carbon protective film sputtered thereon. The coating method was carried out by a pulling method using a solution obtained by adding a Vertrel solvent (fluorine solvent manufactured by Mitsui Dupont Fluorochemical) to a lubricant. The thickness of the lubricating layer was measured using an infrared spectrophotometer. At this time, the film thickness was determined from the strength of CF vibration expansion and contraction in the lubricating layer.

  A constant vertical load of 0.8 g was applied to the magnetic recording medium (glass disk) coated with a lubricant at a position 20.0 mm in the radial direction from the center using a hard disk head. With a constant load applied, an external force P in the direction of rotating the disk (vector is a tangential direction) was generated, and the external force P was gradually increased by gradually increasing the torque.

  While the external force P in the tangential direction is small, the head does not slip due to the frictional force, but when the external force exceeds a certain value, the tangential external force P becomes equal to the frictional force F and the head starts to slide. The static friction coefficient (μ) was calculated from the friction force F at this time. The calculation method followed Formula 1. The measurement was performed at a temperature of 25 ° C. and 80 ° C.

μ (Static friction coefficient) = F (Friction force) / W (Vertical load) Equation 1
The result of the static friction coefficient obtained by the above method is shown in FIG. In the conventional lubricant, the static friction coefficient at 80 ° C. was slightly lower than the static friction coefficient at 25 ° C. This is because the fluidity is higher (viscosity is smaller) at higher temperatures because the fluidity is larger (the viscosity is smaller), but the temperature dependence of viscosity is small, so there is not much change. It is thought that it means that.

  On the other hand, in the lubricant of the present invention, the coefficient of static friction at 25 ° C. is significantly higher than that of the conventional lubricant, and it can be seen that the lubricant does not show lubricity. However, at 80 ° C., the static friction coefficient of the lubricant of the present invention was the same value as the static friction coefficient of the conventional lubricant.

  In other words, it does not exhibit fluidity at room temperature, and therefore does not exhibit lubricity, so that the evaporation of the lubricant can be reduced, the migration of the lubricant due to the rotation of the disk can be suppressed, and the invasion of volatile organic substances can be prevented. By suppressing it, it is possible to prevent the corrosion and the like and to realize the effect of improving the reliability of the magnetic recording medium, particularly the long-term reliability.

  In addition, it showed fluidity at high temperatures, and thus showed lubricity, indicating that it can be used as a heat-assisted magnetic recording lubricant.

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

  (Supplementary note 1) A lubricant for a magnetic recording medium having a viscosity at 25 ° C of 100 Pa · s or more and a viscosity at 80 ° C of 1 Pa · s or less.

  (Supplementary note 2) The lubricant according to supplementary note 1, wherein the viscosity at 80 ° C is 1000 times or more of the viscosity at 25 ° C.

(Supplementary Note 3) A lubricant used for a magnetic recording medium of a heat-assisted magnetic recording device, wherein the heat-assisted magnetic recording device exhibits fluidity in and near the heat-irradiated region and in the vicinity thereof,
Lubricant that does not exhibit fluidity in areas other than the heat-irradiated region and its vicinity.

(Supplementary Note 4) A lubricant used for a magnetic recording medium of a heat-assisted magnetic recording apparatus, which exhibits fluidity in and near the region irradiated with heat when the heat-assisted magnetic recording apparatus is irradiated with heat,
The lubricant according to appendix 1 or 2, which does not exhibit fluidity in a region other than the heat-irradiated region and its vicinity.

  (Supplementary Note 5) The lubricant according to any one of Supplementary Notes 1 to 4, wherein the lubricant is a polymer having a linear molecular structure that may include an ether bond and containing fluorine.

  (Additional remark 6) The lubricant of Additional remark 5 which contains at least any one of a carboxy group and a hydroxy group in the terminal group of the said polymer one terminal or both terminals.

  (Supplementary note 7) A magnetic recording medium using the lubricant according to any one of supplementary notes 1 to 6.

(Appendix 8) A magnetic recording apparatus for using the magnetic recording medium according to appendix 7,
With a heating mechanism,
At the time of writing the magnetic recording, the magnetic recording medium is heated so that the lubricant in the writing target area during the writing and the vicinity thereof exhibits fluidity, or
When writing the magnetic recording, the magnetic recording medium is heated so that the lubricant in the writing target area and the vicinity thereof is fluid, and the magnetic recording medium is read while the magnetic recording is being read. A magnetic recording apparatus in which heating is applied to a reading target area and its vicinity.

(Supplementary note 9) A heat-assisted magnetic recording apparatus for using the magnetic recording medium according to supplementary note 7,
When the magnetic recording is written, the magnetic recording medium is subjected to heat irradiation so that the lubricant in the writing target region during writing and the vicinity thereof exhibits fluidity, or
At the time of writing the magnetic recording, heat irradiation is performed so that the lubricant in the writing target area during the writing of the magnetic recording medium and the lubricant in the vicinity thereof show fluidity, and during the reading of the magnetic recording, A heat-assisted magnetic recording apparatus in which heat irradiation is performed on an area to be read during reading and the vicinity thereof.

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 and the magnetic recording medium. It is a schematic diagram which shows a mode that the lubricant of a magnetic recording medium changes from the state which does not show fluidity to the state which shows fluidity. It is a graph which shows the change of the viscosity when temperature is changed. It is a graph which shows the result of the static friction coefficient of the lubricant used in the Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetic recording medium 2 Head slider 3 Rotation control mechanism 4 Head positioning mechanism 5 Recording / reproducing signal processing circuit 6 Suspension 7 Gimbal 8 Head 9 Head slider protective layer 10 Head slider lubricating layer 12 Substrate 13 Cr underlayer 14 Magnetic layer 15 Magnetic Recording medium protective layer 16 Magnetic recording medium lubricating layer 31 Heat irradiation area

Claims (5)

  A lubricant for a magnetic recording medium having a viscosity at 25 ° C. of 100 Pa · s or more and a viscosity at 80 ° C. of 1 Pa · s or less.   The lubricant according to claim 1, wherein the lubricant is a polymer having a linear molecular structure that may include an ether bond and containing fluorine.   The lubricant according to claim 2, comprising at least one of a carboxy group and a hydroxy group at one or both terminal groups of the polymer. A magnetic recording device for using a magnetic recording medium comprising a magnetic recording medium lubricating layer comprising the lubricant according to any one of claims 1 to 3,
With a heating mechanism,
At the time of writing the magnetic recording, the magnetic recording medium is heated so that the lubricant in the writing target area during the writing and the vicinity thereof exhibits fluidity, or
When writing the magnetic recording, the magnetic recording medium is heated so that the lubricant in the writing target area and the vicinity thereof is fluid, and the magnetic recording medium is read while the magnetic recording is being read. A magnetic recording apparatus in which heating is applied to a reading target area and its vicinity. A heat-assisted magnetic recording apparatus for using a magnetic recording medium comprising a magnetic recording medium lubricating layer made of the lubricant according to claim 1,
At the time of writing magnetic recording, heat irradiation is performed so that the lubricant in the writing target area during writing of the magnetic recording medium and the lubricant in the vicinity thereof show fluidity, or
At the time of writing the magnetic recording, heat irradiation is performed so that the lubricant in the writing target area during the writing of the magnetic recording medium and the lubricant in the vicinity thereof exhibits fluidity, and during the reading of the magnetic recording, A heat-assisted magnetic recording apparatus in which heat irradiation is performed on an area to be read during reading and in the vicinity thereof.

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