Fluorinated and functionalized cycloparaffin lubricant molecules

Abstract

A cyclic lubricant for a magnetic recording medium has general formula (I) or formula (III): CnR2n (I), R1 2pCp-CoR2 2o (III) where R, R1 and R2 may each independently be F or a moiety optionally containing an anchoring functional group and n, o, p are each independently 3-50. The anchoring functional group can be –OH. R, R1 and R2 may each independently be a fluoroalkyl, fluoroalkenyl, perfluoroalkyl, or perfluoroalkyl ether moiety with an optional anchoring functional group, or a fluoroalkyl, fluoroalkenyl, perfluoroalkyl, or perfluoroalkyl ether moiety having a cyclic or aromatic substituent, and with an optional anchoring functional group.

Description

PATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO)FLUORINATED AND FUNCTIONALIZED CYCLOPARAFFIN LUBRICANT MOLECULESCROSS-REFERENCE TO RELATED APPLICATION^ )

[0001] This application claims priority to and the benefit of Non-Provisional Patent Application Serial No. 19 / 182,213 filed in the United States Patent Office on April 17, 2025, the entire content of which is incorporated herein as if fully set forth below in its entirety and for all applicable purposes.FIELD

[0002] The disclosure relates to lubricants, and more particularly, to high temperature lubricants, which may be used with media configured for magnetic recording, e.g., for Heat Assisted Magnetic Recording (HAMR) having ring-shaped architectures.INTRODUCTION

[0003] Magnetic storage systems, such as a hard disk drive (HDD), are utilized in a wide variety of devices in both stationary and mobile computing environments. Examples of devices that incorporate magnetic storage systems include data center storage systems, desktop computers, portable notebook computers, portable hard disk drives, network storage systems, high definition television (HDTV) receivers, vehicle control systems, cellular or mobile telephones, television set top boxes, digital cameras, digital video cameras, video game consoles, and portable media players.

[0004] A typical disk drive includes magnetic recording media in the form of one or more flat disks or platters. The disks generally include two main components, namely, a substrate material that gives it structure and rigidity, and a magnetic medium coating that stores the magnetic signals that represent data in a recording layer within the coating. The typical disk drive also includes a read head and a write head, generally in the form of a magnetic transducer which can sense and / or change the magnetic fields stored on the recording layer of the disks. HAMR is a recordingPATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO) technique that can increase the areal density capability (ADC) of written data on a magnetic recording medium having very high coercivity with high-temperature assistance. However, the high recording temperatures applied to the medium may present challenges. Other examples of magnetic recording media include flexible tape media usable for magnetic tape recording.

[0005] As a result of the high temperatures associated with HAMR technology, suitable lubricants for use in HAMR media may benefit from high thermal stability arising from better methods of bonding with the carbon overcoat layer (COC) on the media surface. In addition, the higher temperatures also increase the presence of contaminants which may negatively affect data storage. The high temperatures may also cause thermally activated reactions in the lubricant such as decomposition and polymerization which will cause discoloring, i.e., fogging, of the storage medium. It is therefore desirable to find lubricant chemistries that will inhibit these thermally activated reactions while maintaining high evaporation temperature.

[0006] A factor in lubricant performance is the distribution of the lubricant on the COC layer, i.e., the packing density. Conventional lubricants arc linear in nature and arc restricted to relatively short side chains. As the length of the side chain increases the steric hindrance will reduce the packing density. Also, increasing the length of the side chain will consequently reduce the coverage on the COC and the lubricants performance and adversely affect the head-disk clearance.

[0007] As such, there is a need in the art for high temperature lubricants having properties suitable for use in HAMR drives, including enhanced bonding of the lubricant to the media and COC in particular.SUMMARY

[0008] In one aspect, this disclosure provides a lubricant comprising:a cyclic lubricant according to general formula (I) or formula (III):CuR2n (I),R pCp-CoR^o (III)where R, R1and R2are each independently F or a moiety optionally containing an anchoring functional group and n, o, and p are each independently from 3 to 50.

[0009] In one aspect, the lubricant described above wherein each anchoring functional group independently comprises at least one of a B, Si, pnictogen, chalcogen, halogen, -OR*, -NR*2, -NR*-CO-R*, -OR*, -O-CO-R*, -CO-O-R*, -SeR*, -TeR*, -PR*2, -PO-(OR*)2, -O-PO-(OR*)2, -PATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO) N=P(NR*2)3, -ASR*2, -SR*, -SO2-(OR*)2, -BR*2, -SiR*3, -(CH2)q-SiR*3, -(CF2)q-SiR*3, or a combination thereof, wherein q is 1 to 10 and each R* is, independently a hydrogen, pnictogen, chalcogen, halogen, saturated or unsaturated aromatic, polycyclic aromatic, heteroaromatic, alicyclic, or heterocyclic C1-C50 radical.

[0010] In one aspect, the lubricant described above wherein at least one anchoring functional group is -OH.

[0011] In one aspect, the lubricant described above having the formula:where n, m are independently from 5 to 200.

[0012] In one aspect, the lubricant described above having the formula:

[0013] In one aspect, the lubricant described above wherein R, R1, R2, each independently comprises a fluoroalkyl, fluoroalkenyl, perfluoroalkyl, or perfluoro alkyl ether moiety with an optional anchoring functional group.

[0014] In one aspect, the lubricant described above wherein R, R1, R2each independently comprises a fluoroalkyl, fluoroalkenyl, perfluoroalkyl, or perfluoroalkyl ether moiety having a cyclic or aromatic substituent, and with an optional anchoring functional group.PATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO)

[0015] In one aspect, this disclosure provides a magnetic recording medium comprising: a magnetic recording layer on a substrate; a protective overcoat on the magnetic recording layer; and a lubricant layer comprising the lubricant described above on the protective overcoat.

[0016] In one aspect, the magnetic recording medium described above wherein a clearance between the lubricant and the protective overcoat is:where MW is the molecular weight of the lubricant, h is thickness of the lubricant and f is flexibility of the lubricant.

[0017] In one aspect, the magnetic recording medium described above wherein a coverage, 02, of the lubricant on a surface of the protective overcoat is calculated from a contact angle on the surface with the lubricant, 0Cb, and is determined by formula:COS 0cb = < T COS 0i + O2 COS 02where 02 is a contact angle of the surface at complete coverage, 0i is a contact angle of the surface when uncoated, 01 is a fraction of the surface that is uncoated, and 02 represents a fraction of the surface covered by the lubricant.

[0018] In one aspect, this disclosure provides a data storage system, comprising: at least one magnetic head; a magnetic recording medium including the lubricant described above; a drive mechanism for positioning the at least one magnetic head over the magnetic recording medium; and a controller electrically coupled to the at least one magnetic head for controlling operation of the at least one magnetic head.

[0019] In one aspect, this disclosure provides a method of bonding a lubricant to a carbon overcoat layer (COC) of a magnetic recording medium, including: coating the lubricant described above on the COC; and applying at least one of mechanical action, heat or light to the lubricant to bond the lubricant to the COC.

[0020] In one aspect, the method described above further comprising: burnishing the magnetic recording medium.

[0021] In one aspect, this disclosure provides a method of synthesizing the lubricant described above, the method comprising: condensing a linear diamide to form a ring; hydrogenating the ring: and fluorinating the ring.PATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO)

[0022] In one aspect, the method described above comprising:where n, m are independently is from 5 to 200 and starting n, m are independently CpH pO where p is from 1 to 100.

[0023] In one aspect, this disclosure provides a method of synthesizing the lubricant described above, the method comprising: condensing diacrylate or dimethacrylate to form a ring; hydrogenating the ring: and fluorinating the ring.

[0024] In one aspect, the method described above comprising:PATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO)where n is from 5 to 200.

[0025] In one aspect, the lubricant described above wherein the lubricant are stable above about 250 °C.

[0026] In one aspect, the lubricant described above wherein the lubricant has a weight average molecular weight of greater than or equal to about 0.5 kiloDalton.

[0027] In one aspect, the lubricant described above wherein the lubricant has a polydispersity of about 1 to 2.

[0028] Other aspects and advantages of the present disclosure will become apparent from the following detailed description and examples, when considered in conjunction with the drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1A is a diagram schematically illustrating a data storage device including a slider and a magnetic recording medium in accordance with one aspect of the disclosure.

[0030] FIG. IB is a side schematic view of the slider and magnetic recording medium of FIG.1A in accordance with one aspect of the disclosure.PATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO)

[0031] FIG. 2 is a side schematic view of a magnetic medium configured for head assisted magnetic recording in accordance with one aspect of the disclosure.

[0032] FIG. 3 depicts the basic architecture of cyclic or ring shaped lubricants.

[0033] FIG. 4 is a graph showing the effect of lubricant viscosity on change in fly height, in accordance with an aspect of the disclosure.

[0034] FIG. 5 is a graph of the contamination robustness (Si robustness) for three lubricants as a function of lubricant thickness, in accordance with an aspect of the disclosure.

[0035] FIG. 6 is a graph of the contamination robustness (Si robustness) for three lubricants as a function of COC coverage, in accordance with an aspect of the disclosure.

[0036] FIG. 7 shows the process of applying the lubricant to a disk (e.g., magnetic recording medium in disk form), in accordance with an aspect of the disclosure.

[0037] FIG. 8 is a flowchart of an exemplary process for fabricating a HAMR medium that includes a magnetic recording layer, a capping layer, an overcoat and a lubricant, in accordance with an aspect of the disclosure.

[0038] FIG. 9 shows the structures of Z-Tetraol and Z-Tetraol Multidentate (ZTMD).DETAILED DESCRIPTION

[0039] Heat Assisted Magnetic Recording (HAMR) systems operate at substantially higher temperatures than traditional magnetic recording systems. HAMR is an example of magnetic recording within the class of Energy Assisted Magnetic Recording (EAMR) techniques, where conventional magnetic recording is supplemented by other energy used in the system. Other examples of EAMR may include Microwave Assisted Magnetic Recording (MAMR) and applications of electric current into various conductive and / or magnetic structures near the main pole. This disclosure is generally directed to lubricants having enhanced substrate bonding and high thermal stability that can be used in conjunction with a magnetic recording medium and / or a magnetic data storage system configured for HAMR.

[0040] As noted above, conventional lubricants do not provide the high thermal stability and packing density needed to adequately support HAMR. FIG. 9 shows the structures of conventional lubricants such as Z-Tetraol or Z-Tetraol Multidentate (ZTMD).

[0041] Any lubricant architecture that has increased packing density relative to a linear molecule is advantageous. In general, these are molecules that lack side chains greater than a fewPATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO) carbon-carbon bonds long. The lubricants of the disclosure have large cyclic fluorinated and functionalized molecules for lubrication. One benefit of large cyclic molecules versus their linear counterparts is increased stiffness, which allows for enhanced packing density of the lubricant on a surface, as the molecule will tend toward a globular configuration rather than extended linear configuration. This is driven by a more restricted conformational landscape versus linear molecules. This also leads to a reduction in lubricant viscosity due to reduced intermolecular interactions, which enhances the smear shedding of the head during operation. However, one potential downside of this design is that cyclic molecules will likely perform worse at lubricating versus the same linear molecule at low coverage. However, at higher coverages, cyclic molecules should lubricate better than the same linear molecules due to higher packing density. The rings can be further modified by including side chains or other large rings. The number of anchoring functional groups can be tailored to fine tune the monolayer thickness of the lubricant, with higher number of anchoring functional groups lowering the monolayer thickness. The higher packing density of the cyclic molecules also enhances the contamination robustness of the surface which will correspondingly make failure modes related to contamination less likely.

[0042] The disclosure overcomes the disadvantages of the conventional art by producing a cyclic or ring-shaped lubricant containing a backbone repeating unit having anchoring functional groups. The structure of an aspect of the cyclic lubricant is shown in formula (I):CnR2n (I)where R is F or a moiety containing an anchoring functional group and n = 3-50. A typical example is a substituted cyclohexyl ring of formula (II):PATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO)(II).

[0043] The cyclic lubricant of the disclosure can also take the form of multiple joined rings, for example, in formula (III):R pCp-CoR^o(HI)where R1, R2are independently F or a moiety containing an anchoring functional group, and o, p are independently from 3 to 50. In an embodiment of the disclosure the cyclic lubricant can have the formula (VI):where n, m can independently be from 5 to 200. In another embodiment of the disclosure the cyclic lubricant can have the formula (VII):PATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO)where n is from 5 to 200.Definitions

[0044] As used herein, and unless otherwise specified, the term “Cn” means hydrocarbon(s) having n carbon atom(s) per molecule, where n is a positive integer. Likewise, a “Cm-Cy” group or compound refers to a group or compound including carbon atoms at a total number thereof in the range from m to y. Thus, a C1-C4 alkyl group refers to an alkyl group that includes carbon atoms at a total number thereof in the range of 1 to 4, e.g., 1, 2, 3 and 4.

[0045] “Moiety” refers to one or more covalently bonded atoms which form a part of a molecule. The terms “group,” “radical,” “moiety”, and “substituent” may be used interchangeably.

[0046] The terms “hydrocarbyl radical,” “hydrocarbyl group,” or “hydrocarbyl” may be used interchangeably and are defined to mean a group including hydrogen and carbon atoms only. Preferred hydrocarbyls are C1-C50 radicals that may be linear, branched, or cyclic, and when cyclic, aromatic or non-aromatic. Examples of such radicals include, but are not limited to, alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec -butyl, tert-butyl, pentyl, iso-amyl, hexyl, octyl cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cyclooctyl, cyclononyl, cyclodecyl and the like, aryl groups, such as phenyl, benzyl, naphthyl, and the like.

[0047] For purposes herein, a heteroatom is any non-carbon atom, selected from groups 13 through 17 of the periodic table of the elements. In one or more aspects, heteroatoms are non-metallic atoms selected from B, Si, pnictogens (N, P, As, Sb, Bi), chalcogen (O, S, Se, Te), and halogens (F, Cl, Br, I).PATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO)

[0048] Unless otherwise indicated, the term “substituted” means that at least one hydrogen atom has been replaced with at least one non-hydrogen atom or a functional group.

[0049] For purposes herein, when a segment includes a particular moiety, it is to be understood that the moiety may be bonded to the respective segment at any substitutable position in which a hydrogen atom may be replaced with a chemical bond between the moiety and the segment.

[0050] For purposes herein, a functional group includes one or more of a hydrocarbyl group, a heteroatom, or a heteroatom containing group, such as B, Si, pnictogen, chalcogen, or halogen (such as Br, Cl, F or I), at least one of -OR*, -NR*2, -NR*-CO-R*, -OR*, *-O-CO-R*, -CO-O-R*, -SeR*, -TeR*, -PR*2, -PO-(OR*)2, -O-PO-(OR*)2, -AsR*2, -SbR*2, -SR*, -SO2-(OR*)2, -BR*2, -SiR*3, -(CH2)q-SiR*3, or a combination thereof, wherein q is 1 to 10 and each R* is independently hydrogen, a hydrocarbyl or halocarbyl radical, and two or more R* may join together to form a substituted or unsubstituted completely saturated, partially unsaturated, or aromatic cyclic or polycyclic ring structure, or where at least one heteroatom has been inserted within a hydrocarbyl ring. In an aspect, R* is H such that the functional group may be -OH, -NH2, -NH-CO-H, -OH, H-O-CO-H, -CO-O-H, -SeH, -TeH, -PH2, -PO-(OH)2, -O-PO-(OH)2, -AsH2, -SbH2, -SH, -SO2-(OH)2, -BH2, -SiH3, -(CH2)q-SiH3, or a combination thereof.

[0051] In one or more aspects, functional groups may include: a saturated C1-C50 radical, an unsaturated C1-C50 radical, an alicyclic C3-C50 radical, a heterocyclic C3-C50 radical, an aromatic C5-C50 radical, a heteroaromatic C5-C50 radical, a cyclo triphosphazine radical, a B, Si, pnictogen, chalcogen, halogen, -OR*, -NR*2, -NR*-CO-R*, -OR*, -O-CO-R*, -CO-O-R*, -SeR*, -TeR*, -PR*2, -PO-(OR*)2, -O-PO-(OR*)2, -N=P(NR*2)3, -ASR*2, -SR*, -SO2-(OR*)2, -BR*2, -SiR*3, -(CH2)q-SiR*3, -(CF2)q-SiR*3, or a combination thereof, wherein q is 1 to 10 and each R* is, independently a hydrogen, pnictogen, chalcogen, halogen, saturated or unsaturated aromatic, polycyclic aromatic, heteroaromatic, alicyclic, and / or heterocyclic C4-C50 radical. Anchoring functional groups can also be least one of -OH, -NH2, -NH-CO-H, -O-CO-H, -CO-O-H, -SeH, -TeH, -PH2, -PO-(OH)2, -O-PO-(OH)2, -N=P(NH2)3, -AsH2, -SH, -SO2-(OH)2, -BH2, -SiH3, -(CH2)q-SiH3, -(CF2)q-SiH3, or a combination thereof.

[0052] For purposes herein, a cyclic functional group is a monovalent alicyclic C3-C50 alkyl radical, an alicyclic C3-C50 alkenyl radical, a heterocyclic C3-C50 radical, an aromatic C5-C50 radical, a polycyclic aromatic C10-C50 radical, a hetero aromatic C5-C50 radical, a cyclotriphosphazine radical, or a combination thereof. Unless otherwise indicated, the cyclicPATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO) functional group may be further substituted with another cyclic functional group and / or with one or more functional groups including one or more of a saturated C1-C50 radical, an unsaturated Ci-C50 radical, an alicyclic C3-C50 radical, a heterocyclic C3-C50 radical, an aromatic C5-C50 radical, a heteroaromatic C5-C50 radical, a cyclotriphosphazine radical, a B, Si, pnictogen, chalcogen, halogen, -OR*, -NR*2, -NR*-CO-R*, -OR*, -O-CO-R*, -CO-O-R*, -SeR*, -TeR*, -PR*2, -PO-(OR*)2, -O-PO-(OR*)2, -N=P(NR*2)3, -ASR*2, -SR*, -SO2-(OR*)2, -BR*2, -SiR*3, -(CH2)q-SiR*3, -(CF2)q-SiR*3, or a combination thereof, where q is 1 to 10 and each R* is, independently a hydrogen, pnictogen, chalcogen, halogen, saturated or unsaturated aromatic, polycyclic aromatic, heteroaromatic, alicyclic, or heterocyclic C1-C50 radical.

[0053] For purposes as described herein, an anchoring functional group which is selected for being attachable to and / or engageable with a protective overcoat of a magnetic recording medium refers to a functional group having increased affinity for the protective overcoat of the magnetic recording medium relative to the affinity of a fluoroalkenyl ether moiety, a perfluoroalkyl ether moiety, a pcrfluoroalkcnyl ether moictics, to that same surface. Increased affinity may include Van der Waals forces, weak London Dispersion forces (temporary dipoles), dipole-dipole forces, polar interactions, polarizability / hydrogen bonding interactions, and / or the like, and / or may include the formation of one or more types of bonds, backbending (electron density is donated from a filled orbital on one atom to an empty orbital on an adjacent atom), and / or dative bonds (where both electrons in the shared pair come from only one of the participating atoms) with the protective overcoat of a magnetic recording medium. In one or more aspects, a functional group which is attachable to and / or engageable with a protective overcoat of a magnetic recording medium refers to one or more functional groups having increased affinity for the carbon overcoat (COC) layer of the magnetic recording medium, relative to the affinity of a fluoroalkenyl ether moiety, a perfluoroalkyl ether moiety, a perfluoroalkenyl ether moieties to that same surface. In some aspects, functional groups attachable to and / or engageable with a protective overcoat of a magnetic recording medium include radicals including one or more hydroxyl moieties (-OH), or a single hydroxyl moiety (-OH).

[0054] A “heterocyclic ring,” also referred to herein as a heterocyclic radical, is a ring having a heteroatom in the ring structure as opposed to a heteroatom substituted ring where a hydrogen on a ring atom is replaced with a heteroatom. For example, tetrahydrofuran is a heterocyclic ring and 4-N, N-dimethylamino-phenyl is a heteroatom substituted ring. A substituted heterocyclic ringPATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO) is a heterocyclic ring where a hydrogen of one of the ring atoms is substituted, i.e., replaced, with a hydrocarbyl, or a heteroatom containing group.

[0055] A “compound” refers to a substance formed by the chemical bonding of a plurality of chemical elements. A “derivative” refers to a compound in which one or more of the atoms or functional groups of a precursor compound have been replaced by another atom or functional group, generally by means of a chemical reaction having one or more steps.

[0056] Fluorinated alkyl ethers including fluoroalkyl ethers, fluoroalkenyl ethers, perfluoroalkyl ethers, perfluoroalkenyl ethers, or combinations thereof, refer to branched or linear chains of Ci to C20 alkyl ethers in which one or more hydrogen atoms are substituted with fluorine. In one aspect, all or a majority of alkyl hydrogen atoms are substituted with fluorine.

[0057] For any particular compound disclosed herein, any general or specific structure presented also encompasses all conformational isomers, regio-isomers, and stereoisomers that may arise from a particular set of substituents, unless stated otherwise. Similarly, unless stated otherwise, the general or specific structure also encompasses all enantiomers, diastereomers, and other optical isomers whether in enantiomeric or racemic forms, as well as mixtures of stereoisomers, as would be recognized by a skilled artisan.

[0058] As used herein, the term “aromatic” also refers to pseudoaromatic heterocycles which are heterocyclic substituents that have similar properties and structures (nearly planar) to aromatic heterocyclic ligands, but are not by definition aromatic; likewise the term aromatic also refers to substituted aromatics.

[0059] As used herein, a moiety which is chemically identical to another moiety is defined as being identical in overall composition exclusive of isotopic abundance and / or distribution, and / or exclusive of stereochemical arrangement such as optical isomers, conformational isomers, spatial isomers, and / or the like.HAMR System for Employing Lubricant

[0060] FIG. 1A is a top schematic view of a data storage device 100 (e.g., disk drive or magnetic recording device) configured for heat assisted magnetic recording (HAMR) including a slider 108 and a magnetic recording medium 102 having a lubricant according to one or more aspects of the disclosure. The laser (not visible in FIG. 1A, but see 114 in FIG. 1B) is positioned with a head / slider 108. Disk drive 100 may include one or more disks / media 102 to store data.PATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO) Disk / media 102 resides on a spindle assembly 104 that is mounted to a drive housing 106. Data may be stored along tracks in the magnetic recording layer of disk 102. The reading and writing of data is accomplished with the head 108 (slider) that may have both read and write elements (108a and 108b). The write element 108a is used to alter the properties of the magnetic recording layer of disk 102 and thereby write information thereto. In one aspect, the head 108 may have magneto-resistive (MR), giant magneto-resistive (GMR), or tunnel magneto-resistive (TMR) elements. In an alternative aspect, head 108 may be another type of head, for example, a Hall effect head. In operation, a spindle motor (not shown) rotates the spindle assembly 104, and thereby rotates the disk 102 to position the head 108 at a particular location along a desired disk track 107. The position of the head 108 relative to the disk 102 may be controlled by the control circuitry 110 (e.g., a microcontroller). It is noted that while an example HAMR system is shown, the various embodiments described may be used in other EAMR or non-EAMR magnetic data recording systems, including perpendicular magnetic recording (PMR) disk drives or magnetic tape drives.

[0061] FIG. 1B is a side schematic view of the slider 108 and magnetic recording medium 102 of FIG. 1A. The magnetic recording medium 102 includes a lubricant layer (see FIG. 2) in accordance with one or more aspects of the disclosure. The slider 108 may include a sub-mount 112 attached to a top surface of the slider 108. The laser 114 may be attached to the sub-mount 112, and possibly to the slider 108. The slider 108 includes a write element (e.g., writer) 108a and a read element (e.g., reader) 108b positioned along an air bearing surface (ABS) 108c of the slider for writing information to, and reading information from, respectively, the medium 102. In other aspects, the slider may also include a layer of the lubricant (not shown).

[0062] In operation, the laser 114 is configured to generate and direct light energy to a waveguide (possibly along the dashed line) in the slider which directs the light to a near field transducer (NFT) near the air bearing surface (e.g., bottom surface) 108c of the slider 108. Upon receiving the light from the laser 114 via the waveguide, the NFT generates localized heat energy that heats a portion of the medium 102 near the write element 108a and the read element 108b. The anticipated recording temperature is in the range of about 350°C to 400°C. In the aspect illustrated in FIG. 1B, the laser directed light is disposed between the writer 108a and a trailing edge of the slider. In other aspects, the laser directed light may instead be positioned between the writer 108a and the reader 108b. FIGs. 1A and 1B illustrate a specific aspect of a HAMR system. In other aspects, the magnetic recording medium 102 with the lubricant layer according to aspectsPATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO) of the disclosure can be used in other suitable HAMR systems (e.g., with other sliders configured for HAMR).

[0063] FIG. 2 is a side schematic view of a magnetic recording medium 200 having a lubricant layer according to one or more aspects of the disclosure. In one aspect, the magnetic recording medium 200 may be used in a HAMR system (e.g., disk drive 100). The magnetic recording medium 200 has a stacked structure with a substrate 202 at a bottom / base layer, an adhesion layer 204 on the substrate 202, a heat sink layer 206 on the adhesion layer 204, an interlayer 208 on the heat sink layer 206, a magnetic recording layer (MRL) 210 on the interlayer 208, a capping layer 212 on the MRL 210, an overcoat layer (e.g., carbon overcoat layer or COC layer) 214 on the capping layer 212, and a lubricant layer 216 on the overcoat layer 214. In one aspect, the magnetic recording medium 200 may have a soft magnetic underlayer (SUL) between the adhesion layer 204 and the heat sink layer 206. In one aspect, the magnetic recording medium 200 may have a thermal resistance layer (TRL) between the interlayer 208 and the heat sink layer 206. In one aspect, for disk drive applications, the substrate 202 can be made of one or more materials such as an Al alloy, NiP plated Al, glass, glass ceramic, and / or combinations thereof. In one aspect for magnetic tape recording applications, the substrate 202 can include a flexible material, such a film made of one of various types of resins, polyesters, polyolefins, polyamides, and the like, or combinations thereof. The substrate may include non-magnetic materials, and may be laminated. In some aspects, the magnetic recording medium 200 may have some or all of the layers illustrated in FIG. 2 and / or additional layer(s) in various stacking orders. It should also be noted that each layer shown in FIG. 2 may include one or more sub-layers. For example, the magnetic recording layer may be formed from multiple layers in certain embodiments. Also, some of the layers may be etched before the next layer is applied.

[0064] Lubricants according to aspects disclosed herein may function as boundary lubricants which may be used in various mechanical devices, including on the magnetic recording media of hard disk drives or tape drives and in conjunction with other microelectronic mechanical systems. Boundary lubricants may form a lubricant layer when one or more functional groups of the lubricant attach or otherwise engage with the surface being lubricated. For instance, one or more boundary lubricants may form the lubricant layer 216 on magnetic recording medium 200 (e.g., a disk that includes a magnetic recording layer 210) that moves relative to other parts in the magnetic storage device. This lubricant layer 216 may help to protect the magnetic recording medium fromPATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO) friction, wear, contaminations, smearing, and / or damage caused by interactions between the magnetic recording medium and other parts in the storage device (e.g., interactions between a slider and the magnetic recording medium). In other words, this boundary layer may help limit solid-to-solid contact.

[0065] While the HDD examples illustrated in FIGS. 1 A, IB, and 2 primarily relate to HAMR technology that involves the use of lubricants, the lubricants described herein may also be used in other magnetic recording technologies. These may include Micro wave Assisted Magnetic Recording (MAMR), Perpendicular Magnetic Recording (PMR), Enterprise Perpendicular Magnetic Recording (ePMR), Shingled Magnetic Recording (SMR), or any other magnetic recording technology employing lubricants on magnetic media (e.g., magnetic recording disks or magnetic recording tape).

[0066] In one aspect, each anchoring functional group may independently be a B, Si, pnictogen, chalcogen, halogen, -OR*, -NR*2, -NR*-CO-R*, -OR*, -O-CO-R*, -CO-O-R*, -SeR*, -TcR*, -PR*2, -PO-(OR*)2, -O-PO-(OR*)2, -N=P(NR*2)3, -ASR*2, -SR*, -SO2-(OR*)2, -BR*2, -SiR*3, -(CH2)q-SiR*3, -(CF2)q-SiR*3, or a combination thereof, wherein q is 1 to 10 and each R* is, independently a hydrogen, pnictogen, chalcogen, halogen, saturated or unsaturated aromatic, polycyclic aromatic, heteroaromatic, alicyclic, and / or heterocyclic C1-C50 radical, and two or more R* may join together to form a ring structure. When R* is H, the anchoring functional group can be OH, -NH2, -NH-CO-H, -OH, -O-CO-H, -CO-O-H, -SeH, -TeH, -PH2, -PO-(OH)2, -O-PO-(OH)2, -N=P(NH2)3, -ASH2, -SH, -SO2-(OH)2, -BH2, -SiH3, -(CH2)q-SiH3, -(CF2)q-SiH3, or a combination thereof.

[0067] In one aspect, each cyclic functional group may further be, e.g., may be further substituted with a functional group including at least one of a B, Si, pnictogen, chalcogen, halogen, -OR*, -NR*2, -NR*-CO-R*, -OR*, -O-CO-R*, -CO-O-R*, -SeR*, -TeR*, -PR*2, -PO-(OR*)2, -O-PO-(OR*)2, -N=P(NR*2)3, -ASR*2, -SR*, -SO2-(OR*)2, -BR*2, -SiR*3, -(CH2)q-SiR*3, -(CF2)q-SiR*3, or a combination thereof, wherein q is 1 to 10 and each R* is, independently a hydrogen, pnictogen, chalcogen, halogen, saturated or unsaturated aromatic, polycyclic aromatic, heteroaromatic, alicyclic, and / or heterocyclic C1-C50 radical, and two or more R* may join together to form a ring structure.

[0068] In one aspect, one or more anchoring functional group may include, or is, a hydroxyl (-OH) moiety. In one aspect, each anchoring functional group includes or is a hydroxyl (-OH)PATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO) moiety. In some aspects, one or more cyclic functional groups may be a hydroxyl (-OH) moiety. In some aspects, each cyclic functional group is a hydroxyl (-OH) moiety.Molecular Design

[0069] The basic molecular design of lubricants of the disclosure was performed in light of current high temperature lubricants for HDD, which rely upon increasing molecular stiffness to reduce lubricant loss. A benefit of large cyclic molecules versus their linear counterparts is increased stiffness which leads to lower viscosity and higher packing density on a surface. This is driven by a more restricted conformational landscape versus linear' molecules. These benefits allow for increased smear shedding, contamination robustness, and enhanced lubricity at high coverages.

[0070] FIG. 3 depicts the basic architecture of cyclic or ring shaped lubricants. As shown in FIG. 3, a single ring lubricant 302 is ringed with anchoring functional groups (in this case -OH but not restricted to -OH). In an embodiment there can be a lubricant 304 formed from more than 1 ring. In this case two rings arc shown, but there can be additional rings in the structure. The rings can be further modified by including side chains or other large rings attached. One potential downside of this design is that cyclic molecules will likely perform worse at lubricating versus the same linear molecule at low coverage. To address this, the lubricants of the disclosure can utilize fewer anchoring groups per molecule to compensate for the decreased lubricity or increase the size of the ring.

[0071] The lubricants of the disclosure include a cyclic lubricant containing a backbone repeating unit having anchoring functional groups. The structure of an aspect of the cyclic lubricant is shown in formula (I):CaR2n(I)where R is F or a moiety containing an anchoring functional group and n = 3-50. A typical example is a substituted cyclohexyl ring of formula (II):PATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO)where m is from 0 to 50 or from 1 to 50. Other ring structures can be based on cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cycloundecane, cyclododecane, cyclotridecane, cyclotetradecane, cyclopentadecane, cyclohexadecane, cycloheptadecane, cyclooctadecane, cyclononadecane, cycloeicosane, etc. As the size of the ring increases there will be increases in melting point, boiling point and density.

[0072] The cyclic lubricant of the disclosure can also take the form of multiple joined rings, for example, in formula (III):R^pCp-CoR^o(HI)where R1, R2are independently F or a moiety containing an anchoring functional group, and o, p are independently from 3 to 50. A typical example is a substituted dicyclohexyl ring of formula (IV):PATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO)where q is from 0 to 50 or from 1 to 50. Any CqF2qOH can be replaced with F. Other ring structures can be based on dicyclopropane, dicyclobutane, dicyclopentane, dicyclohexane, dicycloheptane, dicyclooctane, dicyclononane, dicyclodecane, dicycloundecane, dicyclododecane, dicyclotridecane, dicyclotetradecane, dicyclopentadecane, dicyclohexadecane, dicycloheptadecane, dicyclooctadecane, dicyclononadecane, dicycloeicosane, etc. More than 2 cyclic rings may be present in the lubricant and can be up to 50 cyclic rings.

[0073] In an embodiment, the cyclic lubricant of the disclosure can have the formula (V):PATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO) where R1is CnF2n, CnF2nO or a moiety containing at least one anchoring functional group, R2is O=C-N-CmF2mor a moiety containing at least one anchoring functional group, R3is CoF2oor a moiety containing at least one anchoring functional group, and R4is optionally O=C-N or a moiety containing at least one anchoring functional group, and n, m, o are independently 1 to 200. The cyclic lubricant is not restricted to four R groups, and there can be from 3 to 50 R groups in the cyclic lubricant.

[0074] In an embodiment of the disclosure the cyclic lubricant can have the formula (VI):where n, m can independently be from 5 to 200.

[0075] In another embodiment of the disclosure the cyclic lubricant can have the formula (VII):where n is from 5 to 200.PATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO)

[0076] The lubricants of the disclosure are not restricted to rings formed from perfluoroalkanes, as other fluorinated and non-fluorinated moieties can be used. These include alicyclic C3-C50alkyl moieties, alicyclic C3-C50alkenyl moieties, heterocyclic C3-C50moieties, aromatic C5-C50moieties, polycyclic aromatic C10-C50moieties, heteroaromatic C5-C50moieties, cyclotriphosphazine moieties, or a combination thereof.

[0077] FIG. 4 is a graph showing the effect of lubricant viscosity on change in fly height. Change in fly height is related to the amount of material that is irreversibly adhered to the head during operation, with lower changes in fly height related to enhanced ability for the material to be removed. It has been found that the ability to remove the material is related to the lubricant’ s viscosity. All the molecules have the same molecular weight and are linear, but have different main chain repeat units to alter the stiffness of the molecule; with Lube 1 being the most flexible, Lube 2 having an intermediate stiffness and Lube 3 being the stiffest. Thus, as shown in FIG. 4, use of Lube 1 with the lowest viscosity (measured in milli Pascal seconds or mPa*s) results in the lowest change in fly height among the three lubricants. Since cyclic molecules have a lower viscosity relative to their linear counterparts, all cyclic molecules are expected to have enhanced smear shedding relative to their linear counterparts.

[0078] When considering the molecular weight of the polymer between anchoring functional groups, the clearance is defined as:where MW is the molecular weight of the polymer, h is the thickness of the polymer and f is the flexibility of the polymer.

[0079] Just like how the elastic modulus is proportional to the mass between crosslinks, the HDI clearance is proportional to the mass between anchoring functional groups. For example, if a first example lubricant, Lube 1, has a monolayer thickness of 8.8 A and a MW of 3050, and a second example lubricant, Lube 2, has the same design but has a monolayer thickness of 11.5 A at a MW of 4670, then the predicted monolayer thickness of Lube 1 is 9.34 A when considering the entire MW. On the other hand, the predicted monolayer thickness is 8 A when considering the MW of one arm. Since the actual monolayer thickness of 8.8 A is between 9.34 A and 8 A for Lube 1, and the value of 8 A assumes 100% anchoring and 9.34 A assumes 0% anchoring, thisPATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO) suggests the actual lube only has partial anchoring to the carbon overcoat. Following this logic, any additional anchoring groups should further push the monolayer thickness closer to 8 A. That is, in a data storage system, the lubricant may be a monolayer with an average thickness being in the range of 5 to 12 A, or at 8 A.Contamination Robustness

[0080] FIG. 5 is a graph of the contamination robustness (Si robustness quantified by counts of the silicon (Si) contaminants found in the lubricants) for three lubricants as a function of lubricant thickness. Lube la and Lube 2a have the same stiffest main chain repeat unit, whereas Lube 3a has a more flexible main chain repeat unit. Lube 2a does not contain internal anchoring groups. It can be seen that Lube 2a has more Si counts at the same lube thickness (e.g., in the range of about 8-9 Angstroms) than the Lube la or Lube 2a. This difference is related to the lack of internal anchoring groups for Lube 2a.

[0081] FIG. 6 is a graph of the contamination robustness (Si robustness) for three lubricants as a function of COC coverage. In FIGs. 5 and 6, Lubes la and 3a are lubricants with end and internal anchoring functional groups, whereas Lube 2a is without the internal anchoring functional groups; inclusion of the internal anchoring functional group decreases the monolayer thickness. All three lubricants are linear. As the coverage of the lubricant molecules on the disk surface (carbon overcoat or COC in particular) increases the Si counts decrease, thereby increasing the contamination robustness. Coverage of the lubricant (02) is calculated using the Cassie-Baxter model:cos θcb= σ1cosθ1+ σ2cosθ2where θcbis the contact angle of the surface with the lubricant, θ2is the contact angle of the surface at complete coverage, θ1is the contact angle of the uncoated surface / disk, σ1is the fraction of uncoated surface, and σ2represents the fraction of surface covered by the lubricant. The fact that after plotting the coverage data using the Cassie-Baxter model, the data forms a well-behaved master curve indicates that each molecule, regardless of design, have similar packing densities. Since the coverage is with respect to the monolayer state for the lubricants (i.e., this is a relative metric rather than absolute metric), it can be understood that at 100% coverage, there is still some amount of the disk’s surface that is not covered by the lubricants; this is due to poor packing density. By changing the architecture of the lubricant molecule from linear to cyclic, thePATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO) contamination robustness would be enhanced at the same coverage relative to the linear counterpart due to the enhanced packing density; i.e., at the monolayer thickness for a cyclic lubricant there would be more disk surface that is covered. The expectation for a cyclic lubricant can be seen in the dashed line in FIG. 6. Thus, we may expect less Si counts at the same lubricant coverage.

[0082] The clearance for the cyclic lubricant is proportional to the molecular weight between anchoring functional groups. In the disclosure, high molecular weight and high clearance is achieved by optionally including a long side chain on locations on the cyclic ring. This is in contrast to the typical -CF2CF2O- type repeat units in linear lubricants.

[0083] The optional side chain of the cyclic lubricant can be, for example, a fluoroalkyl, fluoroalkenyl, perfluoroalkyl, or perfluoroalkyl ether moiety. The side chain can be attached to the main chain by an ether bond, an ester bond, an amide bond, a nitrile bond, etc. Stiffness of the side chains of the cyclic lubricant can be attained by incorporating an aromatic moiety such as benzene, toluene or a bicyclic hydrocarbon ring such as is set forth in Table 1.Table 1. Bicyclic Hydrocarbon RingsPATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO)

[0084] Strained ring structures can contain heteroatoms such as B, N, O, P and S. Three member rings with one heteroatom include borirane, aziridine, oxirane, phosphirne and thiirane. Three member rings with two heteroatoms include diaziridine, oxaziridine and dioxirane. Four member rings with one heteroatom include azetidine, oxetane, phosphetane and thietane. Four memer rings with two heteroatoms include dizetine, dioxetane and dihetane. The structure of a selection of these possible heteroatom compounds is set forth in Table 2.Table 2. Structure of Heteroatom Compounds.

[0085] Five member rings containing heteroatoms such as O, N, P or S, can also be utilized. These compounds may also include pyrrole, pyrrolidine, furan, tetrahydrofuran, phosphole, phospholane, thiophene, tetrahydrothiophene, imidazole, imidazolidine, pyrazole, pyrazolidine,PATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO) oxathiole, 1,3-oxathiolane, Isoxathiole, 1,2-oxathiolane, oxazole, oxazolidine, isooxizole, isoxazolidine, thiozole, thiazolidine, isothiozole, isothiazolidine, diozolane, dithiole, and dithiolane. Five membered rings having at least three heteroatoms include triazole, furazan, oxadiazole, thiadiazole, dixazole, dithiazole, tetrazole, qxatetrazole, thiatetrazole and pentazole. Structures of some of the five member ring compounds can be found in Table 3.Table 3. Five Member Ring Structures.PATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO)

[0086] For thermally active groups, nitrile or isocyanate containing molecules can be used. The nitriles have a -C=N functional group. The nitriles can include acetonitrile, propionitrile, acrylonitrile, cyanoacrylate, benzonitrile, butyronitrile, cyanoacetic acid, isobutyronitrile, and lactonitrile. The isocyanates have a -R-N=C=O structure. The isocyanates can include methyl isocyanate, propyl isocyanate, butyl isocyanate, toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI) and methylene diphenylmethane diisocyanate (MDI).Synthesis Example 1

[0087] One synthesis route involves a ring forming condensation of a linear diamide, which deforms to form a ring, followed by hydrogenation over Pd / C and fluorination by Simon / Fowler’ s Process to yield formula (VI):PATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO)where, n, m are independently 5 to 200 and the starting repeat unit can be CpFhpO where p = 1 to 100, i.e., CH2O, C2H4O, CaHeO, etc. or some other combination of carbons, oxygens and nitrogen.Synthesis Example 2

[0088] Another synthesis route is the condensation of a diacrylate or dimethcrylate, followed by hydrogenation and fluorination to yield Formula (VII):PATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO)(VII)where n = 5 to 200.

[0089] In one or more aspects, the lubricants are stable above about 250°C, or above about 300°C, or above about 325°C, or above about 350°C, or above about 375°C, and less than or equal to about 450°C, or 425°C when determined in air, nitrogen, helium, or 90 vol% helium / 10 vol% oxygen.

[0090] In one or more aspects, the lubricant has a weight average molecular weight of greater than or equal to about 0.5 kiloDalton (kDa), or from about 1 to about 20 kDa, or from about 2 to about 10 kDa, or from about 3 to about 7 kDa, or from about 1 to about 5 kDa, or 2 to about 4 kDa.

[0091] In one or more aspects, the lubricant has a weight average molecular weight of greater than or equal to about 500 grams per mole (g / mol), or from about 1,000 to about 20,000 g / mol, or from about 2,000 to about 10,000 g / mol, or from about 3,000 to about 7,000 g / mol, or from about 1,000 to about 5,000 g / mol, or 2,000 to about 4,000 g / mol.

[0092] In one or more aspects, the lubricants are essentially pure compounds, having a polydispersity, defined as the number average molecular weight Mn divided by the weight average molecular weight Mw (Mn / Mw), from about 1 to 2, or from about 1 to about 1.5, or from about 1 to about 1.1, or from about 1 to about 1.05.

[0093] Returning to FIG. 2, in one or more aspects, the magnetic recording medium 200 has a stacked structure which includes a lubricant layer 216 according to the disclosure on the overcoat layer 214.

[0094] In one or more aspects, the average thickness of the lubricant layer of the magnetic recording medium is less than about 10 nanometers (nm), or less than about 5 nm, or less than or equal to about 1 nm. In some aspects, the lubricant of the magnetic recording medium has an average thickness from about 0.1 nm to about 10 nm, or from about 0.1 nm to about 1 nm.

[0095] In one or more aspects of the magnetic recording medium, the lubricant may have a bonding percentage of at least about 30%, or at least about 50%, or at least about 70%, or at least about 80%, or at least about 90%, and less than or equal to about 99%, or less than or equal to about 95%, corresponding to a post-stripping bonding level of the lubricant to the total area of an upper surface of the protective overcoat.

[0096] In one aspect, a magnetic data storage system may include a magnetic head; a magnetic recording medium according to any one or a combination of aspects disclosed herein including aPATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO) lubricant according to one or more aspects disclosed herein, a drive mechanism for moving the magnetic head over the magnetic recording medium; and a controller electrically coupled to the magnetic head for controlling operation of the magnetic head.Media Fabrication

[0097] FIG. 7 shows the process of applying the lubricant to a disk (e.g., magnetic recording medium in disk form), in accordance with an aspect of the disclosure. Lubricant 703 is applied to the un-lubricated disk 702 to produce an unbonded lubricated disk 704. A subsequent heat treatment and / or burnishing process 705 (discussed below) yields a fully bonded disk 706.

[0098] FIG. 8 is a flowchart of an exemplary process 800 for fabricating a HAMR medium that includes a lubricant in accordance with an aspect of the disclosure. In one aspect, the process 800 can be used to fabricate the HAMR media described above, including medium 200 shown in FIG. 2.

[0099] At block 802, the process provides a substrate (e.g., substrate 202). At block 804, the process provides an optional adhesion layer (e.g., adhesion layer 204) on the substrate. At block 806, the process provides a heat sink layer (e.g., heat sink layer 206) on the adhesion layer 204. In one aspect, at block 808, the process may additionally provide an interlayer / seed layer (e.g., interlayer 208) on the heat sink layer 206. At block 810, the process provides a magnetic recording layer (MRL) (e.g., MRL 210) on the interlayer / seed layer. At block 812, the process provides a capping layer (e.g., capping layer 212) on the MRL 210.

[0100] At block 814, the process provides an overcoat layer (e.g., overcoat layer 214) on the capping layer 212. At block 816, the process provides a lubricant layer, e.g., lubricant layer 216, on the overcoat layer 214.

[0101] It is important to note that in alternative approaches, the lubricant layer formed above the protective overcoat may include any of the multidentate fluoroalkyl, fluoroalkenyl, perfluoroalkyl, or perfluoropolyether boundary lubricants described herein, singly and / or in any combination.

[0102] In various aspects, the lubricant layer can be formed on the magnetic recording medium, specifically on the protective overcoat, via a dip coating method. For instance, in one aspect the magnetic recording medium may be dipped into a lubricant bath including the multidentate perfluoropolyether boundary lubricant according to one or more aspects of thePATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO) disclosure and a fluorocarbon solvent such as HFE7100 (hydrofluoroether) or VERTREL-XF (hydrofluorocarbon). After a predetermined amount of time, the magnetic recording medium may be pulled out from the lubricant bath at a controlled rate. The solvent may then evaporate, leaving behind a lubricant layer including the multidentate perfluoropolyether boundary lubricant. The bonding percentage is quantified by stripping the lubricated magnetic recording medium with the solvents used in the lubricant bath at various post-lube time periods.

[0103] The thickness of the lubricant layer may be tuned by controlling the submergence duration of the magnetic recording medium in the lubricant bath, the rate at which the magnetic recording medium is removed from the coating solution, and / or the concentration of the boundary lubricant (e.g. the lubricant according to one or more aspects of the disclosure) in the lubricant bath.

[0104] In one or more aspects, the concentration of lubricant in the lubricant bath may be in a range from about 0.001 grams per liter (g / L) to about 1 g / L. In yet other aspects, the concentration of the lubricant in the lubricant bath may be selected so as to achieve a resulting lubricant layer with a thickness in a range from about less than or equal to about 10 nanometers (nm), or less than or equal to about 5 nm, or less than or equal to about 1 nm or from 0.1 nm to less than about 1 nm.

[0105] Likewise, the formation of the lubricant layer on the surface of the magnetic recording medium, specifically on the surface of the protective overcoat, is not limited to dip coating, but may also involve spin coating, spray coating, a vapor deposition, combinations thereof, or any other suitable coating process as would be understood by one having skill in the art upon reading the present disclosure.Burnishing

[0106] Burnishing is a manufacturing process for HDD to reduce asperities and the disk surface. If the lubricant film thickness exceeds its monolayer thickness, the extra lubricant is readily removed by burnishing. On the contrary, when the lubricant film thickness is below the monolayer thickness, the lubricant remains undisturbed. Thus, the monolayer film thickness could be determined by burnishing the disk surface as a function of film thickness. The changes in the lubricant film thickness before and after burnish provide an estimate for the monolayer thickness.

[0107] Several different burnishing pad designs are commonly utilized. Some heads have a burnishing ridge providing a burnishing edge that extends across the entire front surface of thePATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO) head. Other current head designs have burnishing members on the left side and right side of the burnishing head, but have a lengthwise channel between the left and right burnishing members. In such heads, a significant portion of the burnishing head does not burnish the disk, resulting in significant inefficiency in the burnishing process. In one configuration, the burnishing pad has a waffle type pattern of burnishing pads; that is, a plurality of diamond shaped burnishing pads that are disposed on the burnishing head surface. The diamond shaped pads are oriented such that the point of each diamond shaped pad is directed towards the media to be burnished.Thermal Annealing

[0108] The thermal annealing of the lubricants of the disclosure, resulting in advanced adhesion of the lubricant to the COC, is related to the thermal degradation of polymers. In polymers, such as plastics or the lubricants of the disclosure, thermal degradation refers to a type of degradation where chemical changes take place at elevated temperatures, without the simultaneous involvement of other compounds such as oxygen. Even in the absence of air, polymers will begin to degrade if heated high enough. It is distinct from thermal-oxidation, which can usually take place at less elevated temperatures.

[0109] The onset of thermal degradation dictates the maximum temperature at which a polymer or lubricant can be used. It is a limitation in how the polymer is manufactured and processed. For instance, polymers become less viscous at higher temperatures, but thermal degradation places a ceiling temperature on this. Polymer or lubricant devolatilization is similarly affected. At high temperatures, the components of the long chain backbone of the polymer or lubricant can break (chain scission) and react with one another (cross-link) or react to the substrate to change the properties of the polymer. These reactions result in changes to the molecular weight (and molecular weight distribution) of the polymer and can affect its properties.Optical Annealing

[0110] Optical annealing of the lubricants of the disclosure is related to the photo-oxidation of polymers. In polymer chemistry, photo-oxidation (sometimes: oxidative photodegradation) is the degradation of a polymer surface due to the combined action of light and oxygen. It is the most significant factor in the weathering of plastics. Photo-oxidation causes the polymer chains to break (chain scission), resulting in the material becoming increasingly brittle. This leads to mechanicalPATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO) failure and, at an advanced stage, the formation of microplastics. In textiles the process is called phototendering.

[0111] Susceptibility to photo-oxidation varies depending on the chemical structure of the polymer. Some materials have excellent stability, such as fluoropolymers, polyimides, silicones and certain acrylate polymers. The strained anchoring functional group of the lubricant of the disclosure addresses the high stability of the fluoropolymer backbone, by being susceptible to light to break the strained functional group (which can be a strained ring such as cyclopropane or cyclobutane) and thus react with the surface of the COC layer to create an enhanced bond between the lubricant and the underlying disk. The types of light used for optical annealing can typically include laser light. Ultraviolet radiation for lasers includes wavelengths between 180 and 400 nanometers (nm). The visible region is radiation with wavelengths between 400 and 700 nm. The infrared region of the spectrum is radiation with wavelengths between 700 nm and 1 mm. The lubricant of the disclosure does not necessarily require a laser to supply light. Ultraviolet or infrared lamps can be used instead.Additional Aspects

[0112] It should be noted that the methodology presented herein for at least some of the various aspects may be implemented, in whole or in part, in computer hardware, by hand, using specialty equipment, etc. and combinations thereof.

[0113] Moreover, any of the structures and / or steps may be implemented using known materials and / or techniques, as would become apparent to one skilled in the art upon reading the present disclosure.

[0114] In some aspects, for the processes described herein, the processes herein can perform the sequence of actions discussed above in a different order. In other aspects, the processes can skip one or more of the actions. In still other aspects, one or more of the actions are performed simultaneously. In some aspects, additional actions can be performed. For example, in one aspect, the process may include any additional actions needed to fabricate the magnetic recording layer structure.

[0115] In some aspects, the forming or deposition of such layers can be performed using a variety of deposition sub-processes, including, but not limited to physical vapor deposition (PVD), direct current (DC) sputter deposition, ion beam deposition, radio frequency sputter deposition, orPATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO) chemical vapor deposition (CVD), including plasma enhanced chemical vapor deposition (PECVD), low pressure chemical vapor deposition (LPCVD) and atomic layer chemical vapor deposition (ALCVD). In other embodiments, other suitable deposition techniques known in the art may also be used.

[0116] The terms “on,” “above,” “below,” and “between” as used herein refer to a relative position of one layer with respect to other layers. As such, one layer deposited or disposed on / above or below another layer may be directly in contact with the other layer or may have one or more intervening layers. Moreover, one layer deposited or disposed between layers may be directly in contact with the layers or may have one or more intervening layers.

[0117] The above description is made for the purpose of illustrating the general principles of the present disclosure and is not meant to limit the inventive concepts claimed herein. Further, particular features described herein can be used in combination with other described features in each of the various possible combinations and permutations.

[0118] It should be noted that in the development of any such actual aspect, numerous implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system related and business related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time consuming but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. In addition, the device, system and / or method used / disclosed herein can also be formed from some components other than those cited.

[0119] Unless otherwise specifically defined herein, all terms are to be given their broadest possible interpretation including meanings implied from the specification as well as meanings understood by those skilled in the art and / or as defined in dictionaries, treatises, and the like.

[0120] It must also be noted that, as used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless otherwise specified.

[0121] As also used herein, the term “about” denotes an interval of accuracy that ensures the technical effect of the feature in question. In various approaches, the term “about” when combined with a value, refers to plus and minus 10% of the reference value. For example, a thickness of about 20 angstroms (A) refers to a thickness of 20 A + / - 2 A, e.g., from 18A to 22A in this example.

[0122] In the summary and this detailed description, each numerical value should be read once as modified by the term “about” (unless already expressly so modified), and then read again as notPATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO) so modified unless otherwise indicated in context. Also, in the summary and this detailed description, it should be understood that a physical range listed or described as being useful, suitable, or the like, is intended that any and every value within the range, including the end points, is to be considered as having been stated. For example, “a range of from 1 to 10” is to be read as indicating each and every possible number along the continuum between about 1 and about 10. Thus, even if specific data points within the range, or even no data points within the range, are explicitly identified or refer to only a few specific, it is to be understood that inventors appreciate and understand that any and all data points within the range are to be considered to have been specified, and that inventors possessed knowledge of the entire range and all points within the range.

[0123] As used in the specification and claims, “near” is inclusive of “at.” The term “and / or” refers to both the inclusive “and” case and the exclusive “or” case, and such term is used herein for brevity. For example, a composition including “A and / or B” may include A alone, B alone, or both A and B.

[0124] Various components described in this specification may be described as “including” or made of certain materials or compositions of materials. In one aspect, this can mean that the component is made of the particular material(s). In another aspect, this can mean that the component includes the particular material(s). In another aspect, this can mean that the component is formed from only the particular material(s) (e.g., “consists of’ only the particular material(s)). In another aspect, this can mean that the component is formed primarily from the particular material(s) (e.g., “consists essentially of” the particular material(s)), with a percentage of those materials at 75%, 80%, 85%, 90%, or 95%.

[0125] The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any implementation or aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects of the disclosure. Likewise, the term “aspects” does not require that all aspects of the disclosure include the discussed feature, advantage or mode of operation. The term “coupled” is used herein to refer to the direct or indirect coupling between two objects. For example, if object A physically touches object B, and object B touches object C, then objects A and C may still be considered coupled to one another-even if they do not directly physically touch each other. It is further noted that the term “over” as used in the present application in the context of one component located over another component, may be used to meanPATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO) a component that is directly on another component and / or in another component (e.g., directly on a surface of a component or embedded in a component). Thus, for example, a first component that is over the second component may mean that (1) the first component is over the second component, but not directly touching the second component, (2) the first component is directly on (e.g., directly on a surface of) the second component, and / or (3) the first component is in (e.g., embedded in) the second component. The term “about 'value X'“, or “approximately value X,” as used in the disclosure shall mean within 10 percent of the 'value X'. For example, a value of about 1 or approximately 1 would mean a value in a range of 0.9-1.1. In the disclosure various ranges in values may be specified, described and / or claimed. It is noted that any time a range is specified, described and / or claimed in the specification and / or claim, it is meant to include the endpoints (at least in one embodiment). In another embodiment, the range may not include the endpoints of the range. In the disclosure various values (e.g., value X) may be specified, described and / or claimed. In one embodiment, it should be understood that the value X may be exactly equal to X. In one embodiment, it should be understood that the value X may be “about X,” with the meaning noted above.

[0126] While various aspects have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of an aspect of the present invention should not be limited by any of the above-described exemplary aspects, but should be defined only in accordance with the following claims and their equivalents.

Claims

PATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO) WHAT IS CLAIMED IS:

1. A lubricant comprising:a cyclic lubricant according to general formula (I) or formula (III):CnR2n (I),R^pCp-CoR^o (III)where R, R1and R2are each independently F or a moiety optionally containing an anchoring functional group and n, o, and p are each independently from 3 to 50.

2. The lubricant of claim 1, wherein each anchoring functional group independently comprises at least one of a B, Si, pnictogen, chalcogen, halogen, -OR*, -NR*2, -NR*-CO-R*, -OR*, -O-CO-R* -CO-O-R* -SeR*, -TeR*, -PR*2, -PO-(OR*)2, -O-PO-(OR*)2, -N=P(NR*2)3, -ASR*2, -SR*, -SO2-(OR*)2, -BR*2, -SiR*3, -(CH2)q-SiR*3, -(CF2)q-SiR*3, or a combination thereof, wherein q is 1 to 10 and each R* is, independently a hydrogen, pnictogen, chalcogen, halogen, saturated or unsaturated aromatic, polycyclic aromatic, heteroaromatic, alicyclic, or heterocyclic C1-C50 radical.

3. The lubricant of claim 1, wherein at least one anchoring functional group is -OH.

4. The lubricant of claim 1, having the formula (VI):PATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO) where n, m are independently from 5 to 200.

5. The lubricant of claim 1, having the formula (VII):where n is from 5 to 200.

6. The lubricant of claim 1, wherein R, R1, R2, each independently comprises a fluoroalkyl, fluoroalkenyl, perfluoroalkyl, or perfluoroalkyl ether moiety with an optional anchoring functional group.

7. The lubricant of claim 1, wherein R, R1, R2each independently comprises a fluoroalkyl, fluoroalkenyl, perfluoroalkyl, or perfluoroalkyl ether moiety having a cyclic or aromatic substituent, and with an optional anchoring functional group.

8. A magnetic recording medium, comprising:a magnetic recording layer on a substrate;a protective overcoat on the magnetic recording layer; anda lubricant layer comprising the lubricant according to claim 1 on the protective overcoat.

9. The magnetic recording medium of claim 8, wherein a clearance between the lubricant and the protective overcoat is:PATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO)where MW is the molecular weight of the lubricant, h is thickness of the lubricant and f is flexibility of the lubricant.

10. The magnetic recording medium of claim 8, wherein a coverage, 02, of the lubricant on a surface of the protective overcoat is calculated from a contact angle on the surface with the lubricant, 0cb, and is determined by formula:COS 9cb = O1 COS 91 + 02 COS 92where O2 is a contact angle of the surface at complete coverage, Oi is a contact angle of the surface when uncoated, 01 is a fraction of the surface that is uncoated, and 02 represents a fraction of the surface covered by the lubricant.

11. A data storage system, comprising:at least one magnetic head;a magnetic recording medium including the lubricant of claim 1;a drive mechanism for positioning the at least one magnetic head over the magnetic recording medium; anda controller electrically coupled to the at least one magnetic head for controlling operation of the at least one magnetic head.

12. A method of bonding a lubricant to a carbon overcoat layer (COC) of a magnetic recording medium, including:coating the lubricant of claim 1 on the COC; andapplying at least one of mechanical action, heat or light to the lubricant to bond the lubricant to the COC.

13. The method of claim 12, further comprising:burnishing the magnetic recording medium.PATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO) 14. A method of synthesizing the lubricant of claim 1, comprising:condensing a linear diamide to form a ring;hydrogenating the ring: andfluorinating the ring.where n, m are independently is from 5 to 200 and starting n, m are independently CptripO where p is from 1 to 100.

16. A method of synthesizing the lubricant of claim 1, comprising:condensing diacrylate or dimethacrylate to form a ring;PATENT Attorney Docket No.: WDT-1472PCT (WDA-7992-WO) hydrogenating the ring: andfluorinating the ring.

17. A method of synthesizing the lubricant of claim 1, comprising:where n is from 5 to 200.

18. The lubricant of claim 1, wherein the lubricant are stable above about 250 °C.

19. The lubricant of claim 1, wherein the lubricant has a weight average molecular weight of greater than or equal to about 0.5 kiloDalton.

20. The lubricant of claim 1, wherein the lubricant has a poly dispersity of about 1 to 2.

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