Patent Grant
10540997
High-performance lubricants are used in a large number of diverse applications. The requirements of these lubricants are becoming more demanding due to a variety of factors, including increased miniaturization of electronic and mechanical devices, higher-temperature operating conditions, increased expectations for product lifetimes, and expanded ranges of operating and storage environments.
One application in which high-performance lubricants are subject to ever-increasing demands is in magnetic recording apparatuses such as hard disk drives. Some lubricants for hard disk drives include perfluoropolyethers. There remains, however, a need for optimizing PFPE lubricants to meet such ever-increasing demands.
Provided herein is a lubricant including a compound of Formula I
L-(CF2CF2O)n—CF2CH2O—N—OCH2CF2O—(CF2CF2O)n-M (Formula I)
Also provided herein is a lubricant including a compound of Formula II
(OH)CH2CH(OH)CH2—OCH2CF2O—(CF2CF2O)n—CF2CH2O—CH2CH(OH)—CH2—OCH2CF2O—(CF2CF2O)m—CF2CH2O—CH2CH(OH)CH2(OH) (Formula II)
Also provided herein is an apparatus including a substrate; a magnetic layer over the substrate for magnetic recording; a protective overcoat for protecting the magnetic layer; and a layer of lubricant over the protective overcoat. The lubricant may include one or more compounds selected from Formulas I and II.
Before some particular embodiments are provided in greater detail, it should be understood by those of ordinary skill in the art that the particular embodiments do not limit the scope of the concepts provided herein, as features of such particular embodiments may vary. It should likewise be understood that a particular embodiment has features that may be readily separated from the particular embodiment and optionally combined with or substituted for features of any of a number of other embodiments provided herein.
It should also be understood by those of ordinary skill in the art that the terminology used herein is for the purpose of providing some particular embodiments, and the terminology does not limit the scope of the concepts provided herein. Unless indicated otherwise, ordinal numbers (e.g., first, second, third, etc.) are used to distinguish or identify different features or steps in a group of features or steps, and the ordinal numbers do not supply a serial or numerical limitation. For example, “first,” “second,” and “third” features or steps need not necessarily appear in that order, and the particular embodiments need not necessarily be limited to the three features or steps. Unless indicated otherwise, any labels such as “left,” “right,” “front,” “back,” “top,” “bottom,” “forward,” “reverse,” “clockwise,” “counter-clockwise,” “up,” “down,” or other similar terms such as “upper,” “lower,” “aft,” “fore,” “verticle,” horizontal,” “proximal,” “distal,” and the like are used for convenience and are not intended to imply, for example, any particular fixed location, orientation, or direction. Instead, such labels are used to reflect, for example, relative location, orientation, or direction. Unless indicated otherwise, singular forms of “a,” “an,” and “the” include plural forms unless the context clearly dictates otherwise.
Unless defined otherwise, all scientific and technical terms used herein have the same meaning as commonly understood by those of ordinary skill in the art.
1. Definitions
As used in this application, the following words or phrases include the meanings specified.
A “storage medium” (plural: “storage media”) or “recording medium” (plural: “recording media”) includes any apparatus that can store information such as digital data. The storage medium may be in the form of a thin magnetic film, for example, a magnetic film of cobalt, platinum, and/or chromium alloy over a supporting substrate. One example of a supporting substrate is a nickel-phosphorous-plated aluminum or glass disk. The storage medium may also have a protective layer or overcoat applied over the magnetic film. An example of a protective overcoat includes, but is not limited to, amorphous carbon such as diamond-like carbon.
A “recording layer” or “recording surface” includes a portion of a storage medium adapted for magnetic recording of information. The magnetic recording may be effected by a magnetic head (or read-write head) assembly flying over the recording layer or recording surface. The magnetic head assembly may be mounted on a slider with an air-bearing surface for flying over the recording surface.
A “data zone” includes a zone over which the magnetic head assembly flies, in which the magnetic head assembly magnetically writes information, and from which the magnetic head assembly magnetically reads information. The data zone may have a roughness average of less than about 15 {acute over (Å)}, or a roughness average of less than about 10 {acute over (Å)}.
A “fluoropolyether” (“FPE”) includes a compound or polymer composed of at least some fluoroalkyloxy units (e.g., CH2CF2O—, —CF2CH2O—, —CH2CH2CF2O—, —CH2CF2CF2O—, —CH2CF2CH2O—, CF2CF2CH2O—, —CF2CH2CH2O—, —CF2CH2CF2O— etc.) some of which may optionally be perfluoroalkyloxy units (e.g., —CF2CF2O—, CF2CF2CF2O—, etc.). A “per£luoropolyether” (“PFPE”) includes a compound or polymer composed of perfluoroalkyloxy units. Examples of commercially available FPEs and PFPEs include, but are not limited to, Fomblin Z (random copolymer of CF2CF2O and CF2O units), Fomblin Y (random copolymer of CF(CF3)CF2O and CF2O), and functional derivatives of Fomblin Z or Fomblin Y such as ZDOL, ZDOL TX, and Z-TETRAOL, available from Montedison S. p. A (Milan, Italy); Demnum™ available from Daikin America, Inc. (Orangeburg, N.Y.); and DuPont™ Krytox®.
“Backbone” includes a main chain of a compound or polymer such as the main chain of an FPE or a PFPE. Elements of the backbone may includecarbon (C), nitrogen (N), oxygen (O), or other linker elements. The backbone of an FPE or a PFPE, itself, does not bond to a surface (e.g, diamond-like carbon surface) over which the FPE or the PFPE is applied. However, the backbone of the FPEs provided herein may interact with or bond to such a surface through intervening non-terminal functional groups.
A “functional group” includes a functionalized substituent attached to a chain (e.g., main chain or backbone; side chain; etc.) of an FPE that is capable of interacting or bonding with a surface over which the FPE is applied. Examples of functional groups that may be used include, but are not limited to, any one or more of hydroxyl, alkoxyl, carbocycyl, phenyl, heterocycyl, piperonyl, carboxyl, alkylamido, acetamido, carbamoyl, N-alkylcarbamoyl, N,N-dialkylcarbamoyl, 2,3-dihydroxy-1-propoxyl, acryloyl, alkacryloyl, methacryloyl, a substituent of methyl methacrylate, and a substituent of glycidyl ether. Functional groups may cause the FPEs to interact with or bond to a surface through one or more intermolecular interactions (e.g., polar interactions) adhering the FPEs to a surface. If methacryloyl, a substituent of methyl methacrylate, or a substituent of glycidyl ether is used, then ultraviolet light may optionally be used to activate the bonding enhancer.
A “terminal functional group” includes a functional group that is attached to a linker element of the backbone or a side chain thereof on an end of the backbone or the side chain thereof.
A “non-terminal functional group” includes a functional group that is attached to a linker element of the backbone or a side chain thereof that is not at an end of the backbone or the side chain thereof. A non-terminal functional group may be attached at any one or more points along the backbone or the side chain thereof. One or more non-terminal functional groups may be provided in order to reduce the height that the backbone extends from the surface.
Various aspects of lubricants including FPEs for storage media and storage media incorporating the lubricants are provided herein below. However, as those of ordinary skill in the art will readily appreciate, the FPEs may be used in other capacities including other compositions and apparatuses.
2. Compositions
Lubricants may include one or more FPEs including a backbone, wherein each end of the backbone may terminate with one or more terminal functional groups (e.g., —OH). The one or more terminal functional groups may cause each end of the backbone to bond to a surface (e.g., diamond-like carbon-coated surface) over which the FPE is applied. One or more non-terminal functional groups (e.g., —OH) may also be attached at any point along the backbone including at or near a center of the backbone. The one or more non-terminal functional groups may cause internal points of the backbone to bond to the surface over which the FPE is applied, thereby drawing and conforming the FPE to the surface. In addition to optimizing bonding of FPEs to surfaces such as those with a carbon (e.g., diamond-like carbon) overcoat, the use of the functional groups in the foregoing configuration beneficially reduces the height that lubricants including the FPEs reach, for example, into head-media spacing (“HMS”) in hard disk drives.
Lubricants may include, wholly or in part, one or more compounds of Formula I
L-(CF2CF2O)n—CF2CH2O—N—OCH2CF2O—(CF2CF2O)m-M (Formula I)
Lubricants may include, wholly or in part, one or more compounds of Formula II
(OH)CH2CH(OH)CH2—OCH2CF2O—(CF2CF2O)n—CF2CH2O—CH2CH(OH)—CH2—OCH2CF2O—(CF2CF2O)m—CF2CH2O—CH2CH(OH)CH2(OH) (Formula II)
For lubricants including one or more compounds selected from Formulas I and II, the values of n and m, each of which may be greater than or equal to 1 (e.g., ≥1, 2, 3, 4, 5, etc.), may be selected so as to provide compounds having a molecular weight that falls within a desired average range. The average molecular weight range, for example, may range from about 1000 dalton (“Da”) to about 7000 Da, including from about 1000 Da to about 5000 Da, such as about 2000 Da to about 4000 Da.
Compared to other lubricants, lubricants including one or more compounds selected from Formulas I and II provide higher resistance to head-media contact (e.g., higher power is needed during a shock event to put the head into contact with underlying media); lower lubricant pickup by head (e.g., the low-flying or media-contacting head picks up less lubricant); lower negative burnish; and lower HMS, which, in turn, leads to higher areal density.
With respect to lower HMS,
The conventional lubricant may include an FPE or a PFPE lacking non-terminal functional groups attached to a backbone thereof. Lubricants including one or more compounds selected from Formulas I and II 230B may include one or more non-terminal functional groups 232B attached at any one or more points along the backbone or a side chain thereof. One or more non-terminal functional groups may reduce the height the compounds selected from Formulas I and II extend from the surface (e.g., lubricated surface 220B) Consequently, the distance between the flying head 210B and the surface may be significantly smaller for the lubricant including a compound of Formula I or Formula II than the distance between the flying head 210A and surface when a conventional lubricant is used.
3. Apparatuses Incorporating the Lubricant, and Methods for Lubricating
Apparatuses such as storage media including a lubricant layer formed from lubricants including one or more compounds selected from Formula I and II are provided. Methods for lubricating apparatuses such as storage media may include lubricating, either wholly or in part, with one or more compounds selected from Formulas I and II as provided
With respect to the apparatuses,
The protective layer 140 is a thin film deposited on top of the magnetic layer 130. The protective layer 140 may be a diamond-like carbon (“DLC”) layer, which exhibits properties between those of graphite and diamond. The DLC layer may be deposited using thin film deposition techniques such as one or more thin film deposition techniques selected from ion beam deposition (IBD), plasma enhanced chemical vapor deposition (PECVD), magnetron sputtering, radio frequency sputtering, and chemical vapor deposition (CVD) During the deposition process, adjusting sputtering gas mixtures of argon and hydrogen varies the concentrations of hydrogen found in the DLC. The protective layer may be about 150 {acute over (Å)} thick, or the protective layer may be less than 150 {acute over (Å)} thick, such as less than 100 {acute over (Å)} thick.
Lubricant layer 150 including one or more compounds selected from Formulas I and II may be deposited on top of the protective layer 140 for added protection, lubrication, and enhanced disk drive reliability. Lubricant layer 150 reduces wear and damage caused by occasional contacts of the magnetic head assembly with the storage medium.
The durability and reliability of storage media is achieved primarily by the application of the protective layer 140 and the lubricant layer 150. As the thickness of the protective layer 140 and the lubricant layer 150 is reduced, greater integration at the interface of the protective layer 140 and the lubricant layer 150 is specified to provide a more durable protective film. The conformation of the lubricant molecules on the protective layer 140, as described in reference to the lubricated surface 220B of
With respect to the methods, the methods for lubricating apparatuses such as storage media may include applying a lubricant layer over a surface to be lubricated. The lubricant layer may be formed using a lubricant including one or more compounds selected from Formulas I and II, which one or more compounds may form the lubricant either wholly or in part.
The lubricant layer such as lubricant layer 150 may be applied evenly in a thin film having a thickness from about 5 {acute over (Å)} to about 50 {acute over (Å)}, including from about 8 {acute over (Å)} to about 40 {acute over (Å)}, for example, from about 10 {acute over (Å)} to about 20 {acute over (Å)}. The lubricant layer may be made as thin as possible while maintaining its characteristics related to storage media durability and slider flyability. The selection of the thickness of the lubricant layer may depend on interactions between the storage medium and the magnetic head assembly, which interactions include the static friction or “sticktion” force on the slider, air shear, and/or the tendency of the lubricant to evaporate.
The methods of preparing storage media using the lubricants described herein may be incorporated into methods for manufacturing disks and disk drives. Inaccordance with these methods, more durable, higher-density storage media may be provided.
These and other aspects related to the lubricants provided herein are further described in the non-limiting Examples set forth below.
Compounds of Formulas I and II such as the compounds of
Starting materials may be available from commercial sources such as Sigma-Aldrich Co. (St. Louis, Mo.). Starting materials may also be prepared using methods available to those of ordinary skill in the art. For example, some starting materials may be prepared using methods available in the following reference: Ho, T.-L. Fieser and Fieser's Reagents for Organic Synthesis, Vol. 27; John Wiley & Sons: New York, 2013.
Organic transformations such as functional group transformations may be used to prepare compounds of Formulas I and II. Forexample, some organic transformations may be used in accordance with organic transformations available in the following reference: Larock, R. C. Comprehensive Organic Transformations, A Guide to Functional Group Preparations, 2nd ed.; John Wiley & Sons: New York, 1999.
Protecting group methodologies for protecting/de-protecting functional groups may be used to prepare compounds of Formulas I and II. For example, some protecting group methodologies may be used in accordance with protecting group methodologies available in the following reference: Greene, T. W.; Wuts, P. G. M. Protective Groups in Organic Synthesis, 3nd ed.; John Wiley & Sons: New York, 1999.
To a 250 mL flask was added 152.35 g of compound (1), 50 mL of t-BuOH, and 1.58 g of potassium tert-butoxide at 65° C. Glycidol (12.17 g) was added to the mixture over 3 hours, and the reaction was carried out for 24 hours.
The reaction mixture was subsequently washed with a mixture of 75 mL of deionized (“DI”) water, 50 mL of isopropyl alcohol, and 1.5 mL of 1:1 HCl. The mixture was then washed with 75 mL of DI water twice. The reaction product was recovered by rotary evaporation.
The crude product was purified by column chromatography on silica gel to afford 47 g of compound (2).
To a 250 mL flask equipped with a Dean-Stark trap and condenser was added 30.60 g of Compound (2), 40 mL of acetone, 30 mL of petroleum ether, and 2 drops of 96% H2SO4. The mixture was stirred under reflux for 20 hours.
The reaction mixture was cooled down to room temperature, and 0.73 g of sodium bicarbonate was added. After stirring for 1 hour, the mixture was filtered through a 1-μm filter. Petroleum ether and acetone were removed by rotary evaporation to afford 25.46 g of compound (3) as an oily liquid.
To a 250 mL flask was added 25.46 g of compound (3), 15 ml of t-BuOH, and 2.23 g of potassium tert-butoxide. The flask was immersed in a 60° C. oil bath. To the flask was added 0.92 g of epichlorohydrin over 1.5 hours, and the reaction mixture was stirred for 24 hrs.
The reaction mixture was cooled down to room temperature. The reaction mixture was subsequently washed with a mixture of 100 mL of water, 50 mL of isopropyl alcohol, and 1 ml of 1:1 HCl. The mixture was then washed with a mixture of 100 mL of water and 30 mL of isopropyl alcohol. After drying, 24.00 g of compound (4) was obtained.
To a 250 mL flask was added 22.5 g of compound (4), 6.5 g of methanol, 3.5 g of water, and 0.37 g of 1:1 HCl. The reaction mixture was stirred in a 65° C. oil bath for 4 hours, and then the reaction mixture was stirred at room temperature for 1 day.
To the reaction mixture was added 10 mL DI water and 0.37 g of sodium bicarbonate. After stirring for 1 hour, the oil phase was washed with 30 mL of DI water. The oil phase was then dissolved in DuPont™ Vertrel®. The Vertrel® solution was dried over anhydrous magnesium sulfate. After removing the magnesium sulfate and solvent, 20.49 g of crude product was obtained.
The above obtained crude product was purified by column chromatography on silica gel to afford 10.1 g of compound (5).
While some particular embodiments have been provided herein, and while the particular embodiments have been provided in some detail, it is not the intention of the applicant(s) for the particular embodiments to limit the scope of the concepts provided herein. Additional adaptations and/or modifications may readily appear to persons having ordinary skill in the art, and, in broader aspects, these adaptations and/or modifications may be encompassed as well. Accordingly, departures may be made from the particular embodiments provided herein without departing from the scope of the concepts provided herein.
This application claims the benefit of U.S. Provisional Patent Application No. 62/109,030, filed Jan. 28, 2015. This application is a continuation of prior U.S. patent application Ser. No. 14/788,654, filed Jun. 30, 2015.
| Number | Name | Date | Kind |
|---|---|---|---|
| 6608009 | Akada | Aug 2003 | B2 |
| 7683012 | Burns | Mar 2010 | B2 |
| 8586703 | Yang | Nov 2013 | B2 |
| 9805755 | Yang | Oct 2017 | B1 |
| 20020119316 | Shukla | Aug 2002 | A1 |
| 20140029137 | Musashi | Jan 2014 | A1 |
| Entry |
|---|
| Marchon et al., “Fomblin Multidentate Lubricants for Ultra-Low Magnetic Spacing,” IEEE Trans Magn, vol. 42, No. 10, Oct. 2006, pp. 2504-2506. |
| Number | Date | Country | |
|---|---|---|---|
| 20170365287 A1 | Dec 2017 | US |
| Number | Date | Country | |
|---|---|---|---|
| 62109030 | Jan 2015 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14788654 | Jun 2015 | US |
| Child | 15693372 | US |
