Tape medium having a magnetic recording layer and an underlying layer

Abstract

One approach includes a magnetic recording layer formed on an underlayer, the underlayer including first encapsulated nanoparticles, each including a first magnetic nanoparticle encapsulated by a first aromatic polymer, and a first polymer binder that binds the first encapsulated nanoparticles together, and the recording layer including second encapsulated nanoparticles, each including a second magnetic nanoparticle encapsulated by a encapsulating layer, and a second polymer binder that binds the second encapsulated nanoparticles together.

Description

[Technical field]

[0001] The present invention relates to data storage systems, and more particularly, the present invention relates to magnetic recording layers for tape media. [Background technology]

[0002] In a magnetic storage system, a magnetic transducer reads data from and writes data onto a magnetic recording medium. Data is written onto the magnetic recording medium by moving a magnetic recording transducer to a location on the medium where the data is to be stored. The magnetic recording transducer then generates a magnetic field that encodes the data into the magnetic medium. Data is read from the medium by similarly positioning a magnetic read transducer and sensing the magnetic field of the magnetic medium. Read and write operations can be independent and synchronized with the movement of the medium to ensure that data can be read from and written to desired locations on the medium.

[0003] An important and continuing goal in the data storage industry is to increase the density of data stored on a medium. In the case of tape storage systems, this goal translates to increasing the track and linear bit density on the recording tape and decreasing the thickness of the magnetic tape media. However, the development of smaller footprint and higher performance tape drive systems creates a variety of challenges, from designing tape head assemblies for use in such systems to addressing the dimensional instability of the tape. Summary of the Invention

[0004] One approach includes an article of manufacture that includes an underlayer and a magnetic recording layer formed on the underlayer. The underlayer includes first encapsulated nanoparticles, each including a first magnetic nanoparticle encapsulated by a first aromatic polymer, and a first polymeric binder that binds the first encapsulated nanoparticles. The recording layer includes second encapsulated nanoparticles, each including a second magnetic nanoparticle encapsulated by an encapsulation layer, and a second polymeric binder that binds the second encapsulated nanoparticles.

[0005] Various advantages of products having the above-described structure include, but are not limited to, one or more of the following: thinner recording layers, more uniform distribution of magnetic particles in the recording layer, flatter, less turbid interface between the underlayer and the recording layer, higher glass transition temperatures, less or substantially no voiding of magnetic particles in the recording layer, etc. Each of these advantages results in magnetic recording products, such as tapes, that exhibit one or more of the following characteristics, but are not limited to, improved tear resistance, increased recording resolution down to 1 nm or less, lower noise resulting in a higher signal-to-noise ratio, etc.

[0006] In one embodiment, the underlayer is conductive. The conductive property of the underlayer aids in dissipating charge, for example by conducting the charge to the grounded hub, thereby minimizing charge transfer to the head and, consequently, reducing the risk of condensed liquid water forming a conductive path between the tape and the head surface that provides a path for electrochemical corrosion of the recording head structure.

[0007] In another aspect, the underlying layer is free of wear particles, which have been found to constitute increasingly unacceptable defects and a source of damage to shrinking read and write structures in current and future recording heads.

[0008] In an embodiment, the sealing layer comprises a second aromatic polymer. Aromatic polymers are suitable as sealing layers because the aromatic ring structures seal the surface of the magnetic nanoparticles. Aromatic rings have a very good behavior, especially in relation to chemically reactive metal oxides such as chromium oxide, due to the unique properties of aromaticity in their molecules, which provide improved stability and some magnetic shielding at the surface of the magnetic nanoparticles when properly aligned with the magnetic axis of the magnetic nanoparticles. For example, aromatic ring structures can act as a magnetic field modifier due to their unique molecular electronic structure and ability to suppress external magnetic fields. Aromatic polymers also provide magnetic shielding at the surface of the pigment, helping to isolate the magnetic nanoparticles from other particles to improve the independent switching of the encapsulated nanoparticles, resulting in higher bit resolution.

[0009] In one embodiment, the recording layer is substantially unintermixed with the underlying layers, a feature that solves a long-standing problem in magnetic recording tape production, namely, intermixing of layers at their interfaces and the well-known problems that such intermixing creates.

[0010] In one preferred embodiment, the product is a magnetic recording tape.

[0011] Other aspects and approaches of the invention will become apparent from the following detailed description, which, when read in conjunction with the drawings, illustrate, by way of example, the principles of the invention. [Brief description of the drawings]

[0012] [Figure 1A] 1 is a schematic diagram of a simplified tape drive system. [Figure 1B] 1 is a schematic diagram of a tape cartridge according to one embodiment of the present invention. [Figure 2A] FIG. 2 is a side view of a flat-lapped bi-directional, two-module magnetic tape head according to one embodiment of the present invention. [Figure 2B] 2B is a view of the tape bearing surface taken from line 2B of FIG. 2A. [Figure 2C] FIG. 2C is a detailed view taken from circle 2C of FIG. 2B. [Figure 2D] FIG. 13 is a detailed view of a partial tape bearing surface of a pair of modules. [Diagram 3] FIG. 2 is a partial tape bearing surface view of a magnetic head having a write-read-write configuration. [Figure 4] FIG. 2 is a partial tape bearing surface view of a magnetic head having a read-write-read configuration. [Diagram 5] FIG. 2 is a side view of a magnetic tape head using three modules, all of which lie generally along parallel planes. [Figure 6] FIG. 1 is a side view of a magnetic tape head using three modules in a tangent (angled) configuration. [Figure 7] FIG. 1 is a side view of a magnetic tape head using three modules in an overlapping configuration. [Figure 8A] FIG. 1 is a schematic diagram showing the principle of tape tenting. [Figure 8B] Schematic diagram showing the principle of tape tenting. [Figure 8C] Schematic diagram showing the principle of tape tenting. [Figure 9] 2 is a representation of files and indexes stored on a magnetic tape in accordance with one aspect of the present invention; [Figure 10] 1A to 1C are partial cross-sectional views of the basic structure of a magnetic recording medium according to various approaches. [Figure 11] 1 is a plot showing dynamic mechanical analysis (DMA) of coatings to determine critical pigment volume concentration (CPVC) by various approaches. [Figure 12] This is a transmission electron microscope (TEM) image of a cross section of a conventional recording tape. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The following description is made for the purpose of illustrating the general principles of this invention and is not intended to limit the inventive concepts claimed herein. Moreover, particular features described herein can be used in combination with other features described in a wide variety of possible combinations and permutations.

[0014] Unless otherwise defined in this specification, all terms should be given their broadest possible interpretation, including the meaning implied from this specification and the meaning understood by a person skilled in the art and / or defined in dictionaries, technical books, etc.

[0015] It should also be noted that as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless specified otherwise.

[0016] The following description discloses various configurations of layers and methods for forming those layers that are particularly useful in magnetic recording media.

[0017] In one general approach, an article includes an underlayer and a magnetic recording layer formed on the underlayer. The underlayer includes first encapsulated nanoparticles, each including a first magnetic nanoparticle encapsulated by a first aromatic polymer, and a first polymer binder that binds the first encapsulated nanoparticles. The recording layer includes second encapsulated nanoparticles, each including a second magnetic nanoparticle encapsulated by an encapsulation layer, and a second polymer binder that binds the second encapsulated nanoparticles. Example Operating Environment

[0018] Figure 1A illustrates a simplified tape drive 100 of a tape-based data storage system that may be used in the context of the present invention. Although a particular implementation of a tape drive is shown in Figure 1A, it should be noted that the approaches described herein may be implemented in the context of any type of tape drive system.

[0019] As shown, a tape supply cartridge 120 and a take-up reel 121 are provided for supporting a tape 122. One or more of the reels may form part of a removable cartridge, but are not necessarily part of the tape drive 100. A tape drive such as that illustrated in FIGURE 1A may further include a drive motor or motors that drive the tape supply cartridge 120, and a take-up reel 121 that moves the tape 122 over some type of tape head 126. Such a head may include an array of readers, writers, or both.

[0020] The guide 125 guides the tape 122 across the tape head 126, which is also coupled to a controller 128 via a cable 130. The controller 128 may be or may include a processor and / or any logic for controlling any of the subsystems of the drive 100. For example, the controller 128 typically controls head functions such as servo tracking, data writing, and data reading. The controller 128 may include at least one servo channel and at least one data channel, each of which includes data flow processing logic configured to process and / or store information written to and / or read from the tape 122. The controller 128 may operate under any logic known in the art as well as any logic disclosed herein and may be considered as a processor for any of the tape drive descriptions contained herein in various approaches. The controller 128 may be coupled to any known type of memory 136, which may store instructions executable by the controller 128. Additionally, the controller 128 may be configured and / or programmable to perform or control some or all of the methodologies presented herein. Thus, the controller 128 may be considered to be configured to perform various operations by logic programmed into one or more chips, modules or blocks, or a combination thereof, and software, firmware or other instructions or a combination thereof available to one or more processors, and a combination thereof.

[0021] Cable 130 may include read / write circuitry for transmitting data to tape head 126, recording data on tape 122, and receiving data from tape 122 that is read by tape head 126. Actuator 132 controls the position of tape head 126 relative to tape 122.

[0022] An interface 134 may also be provided for communication between tape drive 100 and a host (internal or external) to send and receive data, and for controlling the operation of tape drive 100 and communicating the status of tape drive 100 to the host, all as would be understood by one of ordinary skill in the art.

[0023] FIG. 1B illustrates an exemplary tape cartridge 150, which may include any of the configurations of magnetic recording media in tape form described herein in various approaches. Such a tape cartridge 150 may be used with a system such as that shown in FIG. 1A. As shown, the tape cartridge 150 includes a housing 152, a tape 122 within the housing 152, and an optional non-volatile memory 156 coupled to the housing 152. In some approaches, the non-volatile memory 156 may be embedded within the housing 152, as shown in FIG. 1B. In more approaches, the non-volatile memory 156 may be attached to the interior or exterior of the housing 152 without modifying the housing 152. For example, the non-volatile memory may be embedded in a self-adhesive label 154. In one preferred approach, the non-volatile memory 156 may be a solid state memory (e.g., flash memory), a read-only memory (ROM) device, or the like, embedded or coupled to the interior or exterior of the tape cartridge 150. This non-volatile memory can be accessed by the tape drive, tape operation software (driver software), and / or other devices.

[0024] By way of example, Figure 2A illustrates a side view of a flat-wrapped bi-directional two-module magnetic tape head 200 that may be implemented in the context of the present invention. As shown, the head includes a pair of bases 202, each with a module 204, fixed at a small angle α to each other. The bases may be "U-beams" adhesively bonded to each other. Each module 204 includes a substrate 204A and a closure 204B with a thin film portion, usually referred to as a "gap", in which a reader and / or writer 206 is formed. In use, a tape 208 is moved over the modules 204 along a media (tape) support surface 209 in the manner shown to read and write data on the tape 208 using the readers and writers. The wrap angle θ of the tape 208 at its edges leading onto and leaving the flat media support surface 209 is typically between about 0.1 degrees and about 3 degrees.

[0025] The substrate 204A is typically constructed of a wear-resistant material such as a ceramic. The closure 204B may be made of the same or a similar ceramic as the substrate 204A.

[0026] The readers and writers may be arranged in a piggyback or integrated configuration. An exemplary piggyback configuration includes a (magnetically inductive) writer transducer above (or below) a (magnetically shielded) reader transducer (e.g., a magnetoresistive reader), with the writer pole and the reader shield typically being separate. An exemplary integrated configuration includes one reader shield on the same (hence "integrated") physical layer as one of the writer poles. The readers and writers may also be arranged in an interleaved configuration. Alternatively, each array of channels may be only readers or writers. Any of these arrays may include one or more servo track readers for reading servo data on the media.

[0027] Figure 2B illustrates the tape support surface 209 of one of the modules 204 as viewed from line 2B of Figure 2A. A representative tape 208 is shown in dashed lines. The module 204 is preferably long enough to be able to support the tape as the head advances between the data bands.

[0028] In this example, the tape 208 includes between 4 and 32 data bands, such as with 16 data bands and 17 servo tracks 210 shown in FIG. 2B on a 1.5 inch wide tape 208. The data bands are defined between the servo tracks 210. Each data band may include a number of data tracks, such as 1024 data tracks (not shown). During read / write operations, the reader and / or writer 206 is positioned at a particular track location within one of the data bands. An external reader, sometimes referred to as a servo reader, reads the servo tracks 210. In response, the servo signals are used to keep the reader and / or writer 206 aligned with a particular set of tracks during read / write operations.

[0029] FIG. 2C shows multiple readers and / or writers 206 formed in gaps 218 on the module 204 at circle 2C in FIG. 2B. As shown, the array of readers and writers 206 includes, for example, 16 writers 214, 16 readers 216, and two servo readers 212, although the number can vary. Exemplary approaches include 8, 16, 32, 40, and 64 active readers and / or writers 206 per array, or an odd number of readers or writers, such as 17, 25, 33, etc., in the case of an interleaved design. Exemplary approaches include 32 readers per array and / or 32 writers per array, where the actual number of transducer elements can be greater, such as 33, 34, etc. This allows the tape to move slower, thus reducing velocity induced tracking and mechanical difficulties and / or allowing fewer "wraps" to be performed to fill or read the tape. While the readers and writers may be arranged in a piggyback configuration as shown in FIG. 2C, the readers 216 and writers 214 may also be arranged in an interleaved configuration. Alternatively, each array of reader / writers 206 may be only readers or writers, or the array may include one or more servo readers 212. As noted by reviewing FIGS. 2A and 2B-2C, each module 204 may include a complementary set of readers and / or writers 206 for bidirectional reading and writing, the ability to read and write simultaneously, backward compatibility, etc.

[0030] FIG. 2D shows a partial tape-bearing surface view of complementary modules of a magnetic tape head 200 according to one approach, where each module has multiple read / write (R / W) pairs in a piggyback configuration formed on a common substrate 204A and, optionally, an electrically insulating insulating layer 236. The writer 214 and the reader 216 are aligned parallel to the intended direction of tape media movement across them to form an R / W pair, illustrated as R / W pair 222. Note that the intended direction of tape movement is sometimes referred to herein as the direction of tape movement, and these terms may be used interchangeably. This direction of tape movement may be inferred from the design of the system, for example, by reviewing the instructions, observing the actual direction of tape movement relative to a reference point, etc. Furthermore, in systems that operate to allow bidirectional reading and / or writing, the directions of tape movement in both directions are typically parallel, and thus both directions may be considered equivalent to each other.

[0031] There may be any number of R / W pairs 222, such as 8, 16, 32 pairs. The R / W pairs 222 shown are aligned linearly, in a direction approximately perpendicular to the direction of tape movement across them. However, the pairs may also be aligned diagonally, etc. The servo reader 212 is positioned outside the array of R / W pairs, but its function is well known.

[0032] Generally, the magnetic tape medium moves in either a forward or reverse direction as indicated by arrow 220. The magnetic tape medium and head assembly 200 operate in a transforming relationship in a manner well known in the art. Head assembly 200 includes two thin film modules 224 and 226 that are generally identically constructed.

[0033] Modules 224 and 226 are coupled to one another, with a space existing between them in their enclosure 204B (partially shown), to form a single physical unit that provides simultaneous read and write capability by energizing the writer of the preceding module and the reader of the succeeding module aligned with the writer of the preceding module parallel to the direction of tape movement relative thereto. When the modules 224, 226 of the magnetic tape head 200 are constructed, the layers for the R / W pair 222 are formed in a gap 218 above a conductive substrate 204A (partially shown), such as AlTiC, typically in the following order: an insulating layer 236, a first shield 232, typically an iron alloy such as NiFe(-), cobalt-zirconium-tantalum (CZT) or Al-Fe-Si (Sendust), a sensor 234 for sensing a data track on the magnetic medium, a second shield 238, typically a nickel-iron alloy (e.g., .about.80 / 20% NiFe, also known as Permalloy), first and second writer poles 228, 230, and a coil (not shown). The sensor can be of any known type, including those based on magnetoresistive (MR), GMR, AMR, tunneling magnetoresistive (TMR), etc.

[0034] The first and second writer poles 228, 230 may be fabricated from a high magnetic moment material, such as ~45 / 55 NiFe. Note that these materials are provided merely as examples and other materials may be used. There may also be additional layers such as insulation between the shield and / or pole tips, and an insulating layer around the sensor. Exemplary materials for insulation include alumina and other oxides, insulating polymers, etc.

[0035] The tape head 126 configuration may include multiple modules, preferably three or more. In a write-read-write (WRW) head, an outer module for writing is placed alongside one or more inner modules for reading. Referring to FIG. 3, which shows a WRW configuration, the outer modules 252, 256 each include one or more arrays of writers 260. The inner module 254 of FIG. 3 includes one or more arrays of readers 258 in a similar configuration. Variations of multi-module heads include RWR heads (FIG. 4), RRW heads, WWR heads, etc. In yet other variations, one or more of the modules may have read / write pairs of transducers. Furthermore, there may be more than three modules. In a further approach, two or more inner modules may be placed alongside two outer modules, such as, for example, a WRRW, RWWR arrangement. For simplicity, a WRW head is primarily used herein to illustrate embodiments of the invention. Those skilled in the art having the benefit of the teachings herein will understand how the permutations of the present invention may be applied to configurations other than the WRW configuration.

[0036] FIG. 5 illustrates one approach to magnetic head 126, including first, second, and third modules 302, 304, 306, each having a tape bearing surface 308, 310, 312, respectively, which may be flat, contoured, or otherwise. Note that the term "tape bearing surface" is used to imply that the surface facing the tape 315 is in physical contact with the tape bearing surface, but this is not necessarily the case. Rather, only a portion of the tape may be in constant or intermittent contact with the tape bearing surface, while other portions of the tape ride (or "fly") on a layer of air, sometimes referred to as "air bearing," above the tape bearing surface. The first module 302 is referred to as the "leading" module because it is the first module the tape encounters in the three-module design when the tape is moving in a directed direction. The third module 306 is referred to as the "trailing" module. The trailing module follows the middle module and is the last module the tape sees in a three-module design. The leading and trailing modules 302, 306 are collectively referred to as the outer modules. Note also that the outer modules 302, 306 take turns as leading modules depending on the direction of movement of the tape 315.

[0037] In one approach, the tape bearing surfaces 308, 310, 312 of the first, second and third modules 302, 304, 306 lie on substantially parallel planes (which is intended to include parallel and nearly parallel planes, e.g., between parallel and tangential as in FIG. 6 ), and the tape bearing surface 310 of the second module 304 is above the tape bearing surfaces 308, 312 of the first and third modules 302, 306. As will be described below, this determines the desired wrap angle α of the tape relative to the tape bearing surface 310 of the second module 304. 2 This has the effect of producing the following:

[0038] Intuitively, if the tape bearing surfaces 308, 310, 312 lie along planes that are parallel or nearly parallel but offset, the tape should peel off from the tape bearing surface 308 of the leading module 302. However, it has been experimentally discovered that the vacuum created by the skiving edge 318 of the leading module 302 is sufficient to keep the tape adhered to the tape bearing surface 308 of the leading module 302. The trailing edge 320 of the leading module 302 (the end where the tape leaves the leading module 302) is at a wrap angle α on the tape bearing surface 310 of the second module 304. 2 The tape remains in close proximity to the tape support surface until near the trailing edge 320 of the leading module 302. Thus, the transducers 322 can be placed near the trailing edges of the outer modules 302, 306. These approaches are particularly suited for write-read-write applications.

[0039] An advantage of this embodiment and the other embodiments described herein is that because the outer module 302, 306 is fixed at a predetermined offset from the second module 304, when the modules 302, 304, 306 are bonded together or otherwise secured within the head, the inner wrap angle α 2 The inside wrap angle α 2 is approximately equal to tan -1 (δ / W). An exemplary inner wrap angle α 2 is between about 0.3 degrees and about 1.1 degrees, but may be any angle required by the design.

[0040] Advantageously, the inside wrap angle α on the side (leading edge) of the module 304 that receives the tape 2 is the inner wrap angle α at the trailing edge 3is greater than α because tape 315 rides above subsequent module 306. This difference is generally advantageous because α 3 This is because the smaller the wrap angle, the steeper the outgoing effective wrap angle tends to be.

[0041] Note that the tape bearing surfaces 308, 312 of the outer modules 302, 306 are positioned to create a negative wrap angle at the trailing edge 320 of the outer module 302. This is generally good in helping to reduce friction due to contact with the trailing edge 320, if proper consideration is given to the location of the burl area formed in the tape where it peels off the head. This negative wrap angle also reduces flutter and scrub damage to the elements on the leading module 302. Furthermore, at the trailing edge 306, the tape 315 flies over the tape bearing surface 312, so there is virtually no wear on the elements as the tape moves in this direction. In particular, the tape 315 does not significantly rest on the tape bearing surface 312 of the third module 306 (although some contact may occur) because it is airborne. This is acceptable because the leading module 302 is writing even when the trailing module 306 is idle.

[0042] The write and read functions are performed by different modules at any given time. In one approach, the second module 304 includes multiple data and optional servo readers 331, but no writers. The first and third modules 302, 306 include multiple writers 322, but no data readers, with the exception that the outer modules 302, 306 may include optional servo readers. The servo readers may be used to position the heads during read and / or write operations. The servo readers in each module are typically located toward the ends of the array of readers or writers.

[0043] By having only a reader in the gap between the substrate and the closure, or by having a writer and a servo reader side by side, it is possible to reduce the length of the gap substantially. A typical head has a piggyback reader and writer, where the writer is formed above each reader. A typical gap is 20-35 microns. However, irregularities on the tape may tend to sag into the gap and cause gap erosion. Thus, the smaller the gap, the better. The smaller gaps made possible herein will present fewer problems with wear.

[0044] In some approaches, the second module 304 has an encapsulation while the first and third modules 302, 306 do not. In the absence of an encapsulation, a hard coating is preferably added to the modules. One preferred coating is diamond-like carbon (DLC).

[0045] In the approach shown in FIG. 5, the first, second and third modules 302, 304, 306 each have a closure 332, 334, 336 that extends the tape bearing surface of the associated module, effectively positioning the read / write elements away from the edge of the tape bearing surface. The closure 332 on the second module 304 can be a ceramic closure of the type typically found in tape heads. However, the closures 334, 336 of the first and third modules 302, 306 can be shorter than the closure 332 of the second module 304 when measured parallel to the direction of tape travel on the respective modules. This allows the modules to be positioned closer to each other. One way to create the shorter closures 334, 336 is to overlap the standard ceramic closure of the second module 304 by an additional amount. Another way is to plate or deposit a thin film closure on the elements during thin film processing. For example, a thin film encapsulation of a hard material such as sendust or a nickel-iron alloy (eg, 45 / 45) can be formed over the module.

[0046] With reduced thickness ceramic or thin film closures 334, 336 or no closure on the outer modules 302, 306, the write to read gap spacing can be reduced to less than about 1 mm, such as about 0.75 mm, or less than 50% of the spacing of commonly used Linear Tape Open (LTO®) tape heads. The open space between the modules 302, 304, 306 can still be set to about 0.5-0.6 mm, which in some approaches is ideal for stabilizing tape movement on the second module 304.

[0047] Depending on the tension and stiffness of the tape, it may be desirable to angle the tape bearing surface of the outer module relative to the tape bearing surface of the second module. Figure 6 illustrates an arrangement in which modules 302, 304, 306 are in a tangential or near tangential (angled) configuration. In particular, the tape bearing surfaces of the outer modules 302, 306 are angled relative to the desired wrap angle α of the second module 304. 2 In other words, the plane of the tape support surfaces 308, 312 of the outer modules 302, 306 is approximately parallel to the tape 315 relative to the second module 304 at a desired wrap angle α 2 In this approach, the tape also moves away from the subsequent module 306, thereby reducing wear on the elements in the subsequent module 306. These approaches are particularly useful for write-read-write applications. Additional aspects of these approaches are similar to those described above.

[0048] Typically, the tape wrap angle may be set approximately halfway between the approach shown in FIG. 5 and the approach shown in FIG.

[0049] 7 illustrates an apparatus in which modules 302, 304, 306 are in an overlapping configuration. In particular, the tape bearing surfaces 308, 312 of the outer modules 302, 306 are aligned at a desired wrap angle α with respect to the second module 304. 2When set to , the tape has a slightly larger angle than the tape 315. In this approach, the tape does not move away from the subsequent module, allowing the subsequent module to be used for writing or reading. Thus, both the preceding and middle modules can perform read and / or write functions, while the subsequent module can only read whatever data has been written. Thus, these approaches are suitable for write-read-write, read-write-read, and write-write-read applications. In the latter approach, the closure must be wider than the tape canopy to ensure read capability. A wider closure may require a wider gap separation. Thus, a preferred approach has a write-read-write configuration, which may use a shortened closure that allows a narrower gap separation.

[0050] Additional aspects of the approach illustrated in Figures 6 and 7 are similar to those described above.

[0051] A 32 channel version of the multi-module tape head 126 may use a cable 350 with leads on the same or smaller pitch as the current 16 channel piggyback LTO modules, or alternatively the connections on the module may be organ key shaped to reduce the cable span by 50%. An unshielded cable with upper and lower write pairs may be used for the writer, which may have an integrated servo reader.

[0052] Outer wrap angle α 1can be set in the drive by any type of guide known in the art, such as adjustable rollers or slides, or alternatively by outriggers integral with the head. A roller with an offset shaft, for example, could be used to set the wrap angle. The offset shaft creates an orbital arc of rotation, and the wrap angle α 1 This allows for accurate alignment of the

[0053] Conventional U-beam assemblies can be used to assemble any of the above-mentioned approaches. Thus, the mass of the resulting head can be maintained or even reduced in weight compared to previous generations of heads. In other approaches, the module can be constructed as a single unit. Those skilled in the art, armed with the teachings herein, will understand that other known methods of manufacturing these heads can be adapted to construct these heads. Additionally, unless otherwise noted, processes and materials of the type known in the art can be adapted for use in the various approaches consistent with the teachings herein, as will be apparent to those skilled in the art upon reading this disclosure.

[0054] As the tape is moved over the module, it is preferable that the tape pass close enough to the magnetic transducers on the module so that reading and / or writing can be performed efficiently, e.g., with a low error rate. According to some approaches, tape tenting may be used to ensure that the tape passes close enough to the portions of the module that have the magnetic transducers. To better understand this process, FIGS. 8A-8C illustrate the principle of tape tenting. FIG. 8A shows a module 800 having an upper tape bearing surface 802 that extends between opposing edges 804 and 806. A stationary tape 808 is shown wrapped around the edges 804, 806. As shown, the bending stiffness of the tape 808 lifts the tape off the tape bearing surface 802. As shown in FIG. 8A, the tension in the tape tends to flatten the shape of the tape. When the tape tension is minimal, the curvature of the tape becomes more parabolic than shown.

[0055] FIG. 8B shows the tape 808 in motion. The leading edge, i.e., the first edge the tape encounters as it moves, may act to strip air from the tape, thereby creating subambient air pressure between the tape 808 and the tape bearing surface 802. In FIG. 8B, as the tape moves from left to right, the leading edge is the edge on the left and the edge on the right is the trailing edge. As a result, atmospheric pressure above the tape forces the tape in a direction toward the tape bearing surface 802, thereby creating tape tenting near each of the edges. The bending stiffness of the tape resists the effects of atmospheric pressure, thereby causing tape tenting near both the leading and trailing edges. Modeling predicts that the two tents are very similar in shape.

[0056] FIG. 8C illustrates how sub-atmospheric pressure urges the tape 808 in a direction toward the tape bearing surface 802 even though the trailing guide 810 is positioned above the plane of the tape bearing surface.

[0057] Thus, tape tenting may be used to direct the path of the tape as it passes over the module, preferably to ensure that the tape passes close enough to the portions of the module that have magnetic transducers so that reading and / or writing can be performed efficiently, e.g., with a low error rate, as described above.

[0058] The magnetic tapes may be stored in tape cartridges, which are in turn stored in storage slots or the like within a data storage library. The tape cartridges may be stored in the library in a manner accessible for physical removal. In addition to the magnetic tapes and tape cartridges, data storage libraries may include data storage drives that store and / or retrieve data from the magnetic tapes. Additionally, tape libraries and the components contained therein may implement file systems that allow access to the tapes and the data stored on the tapes.

[0059] A file system may be used to control how data is stored in and retrieved from memory. Thus, a file system may include the processes and data structures that an operating system uses to keep track of files in memory, such as the manner in which files are organized in memory. A Linear Tape File System (LTFS) is an exemplary format of a file system that may be implemented in a given library to enable access to compatible tapes. It should be understood that various aspects described herein may be implemented using a wide range of file system formats, including, for example, IBM® Spectrum Archive Library Edition (LTFS LE). However, to provide context and simply to assist the reader, some of the following approaches may be described with reference to one type of file system format, LTFS. This is done merely as an example and should not be considered a limitation on the invention as defined in the claims.

[0060] A tape cartridge may be "loaded" by inserting the cartridge into a tape drive, and a tape cartridge may be "unloaded" by removing the tape cartridge from the tape drive. Once loaded into a tape drive, the tape in the cartridge may be "threaded" through the drive by physically pulling the tape (magnetic recording portion) from the tape cartridge and passing it over the magnetic tape head of the tape drive. Additionally, the tape may be attached to a take-up reel (see, e.g., 121 in Figure 1A above) to move the tape over the magnetic tape head.

[0061] Once threaded through the tape drive, the tape in the cartridge may be "mounted" by reading the metadata on the tape and placing the tape in a state that allows LTFS to use it as part of its file system. To further "unmount" the tape, metadata is preferably first written onto the tape (e.g., as an index) and then the tape may be removed from the state that allows LTFS to use it as part of its file system. Finally, to "unmount" the tape, the tape is removed from the take-up reel and physically placed back inside the tape cartridge. The cartridge may remain loaded in the tape drive even after the tape has been unloaded, e.g., waiting for another read and / or write request. However, in other cases, such as when the tape is unloaded as described above, the tape cartridge may be unloaded from the tape drive.

[0062] Magnetic tape is a sequential access medium; that is, new data is written to the tape by appending it to the end of previously written data. Thus, when data is recorded to a tape containing only one partition, as the data is frequently updated and rewritten to the tape accordingly, metadata (e.g., allocation information) is sequentially appended to the end of the previously written data. As a result, when a tape is first mounted, the information at the end is read to access the most recent copy of the metadata corresponding to that tape. However, this introduces a significant amount of delay into the process of mounting a given tape.

[0063] To overcome the delays caused by single-partition tape media, the LTFS format includes tapes divided into two partitions, including an index partition and a data partition. The index partition may be configured to record metadata (meta-information), e.g. file allocation information (index), while the data partition may also be configured to record the main body of data, e.g. the data itself.

[0064] 9, a magnetic tape 900 is illustrated according to one approach, including an index partition 902 and a data partition 904. As shown, data files and indexes are stored on the tape. As will be appreciated by those of ordinary skill in the art upon reading the description herein, the LTFS format allows for index information to be recorded in the index partition 902 at the beginning of the tape 906.

[0065] When index information is updated, it is preferable to overwrite the previous version of the index information so that the current, updated index information can be accessed in the index partition at the beginning of the tape. According to the particular example illustrated in FIG. 9, the latest version of the metadata, Index 3, is recorded in the index partition 902 at the beginning of the tape 906. Conversely, all three versions of the metadata, Index 1, Index 2, and Index 3, and the data, File A, File B, File C, and File D, are recorded in the data partition 904 of the tape. Although Index 1 and Index 2 are old (e.g., not updated) indexes, as described above, information is written to the tape by appending the information to the end of the previously written data, these old indexes, Index 1 and Index 2, remain stored in the data partition 904 on the tape 900 rather than being overwritten.

[0066] Metadata may be updated in the index partition 902 and / or the data partition 904 in the same or different manners depending on the desired approach. According to some approaches, metadata in the index partition 902 and / or the data partition 904 may be updated in response to a tape being unmounted, for example so that the index can be quickly read from the index partition when the tape is mounted again. Metadata is preferably written to the data partition 904 so that a tape can be mounted with the metadata recorded in the data partition 904 as a backup option, for example.

[0067] According to one example, which is in no way intended to limit the invention, LTFS LE may be used to provide the ability to write an index to a data partition when the user explicitly instructs the system to do so or at a time specified by a predefined period that may be set by the user, to mitigate data loss, for example, in the event of a sudden power outage. Manufacturing of magnetic recording media and layers thereof

[0068] FIG. 10 shows a partial cross-sectional view, not to scale, of the basic structure of a magnetic recording medium 1000 according to the various approaches described herein. Optionally, the magnetic recording medium 1000 according to the present invention may be implemented with features according to any other approach enumerated herein, such as those described with reference to other figures. However, of course, such magnetic recording medium 1000 and others presented herein may be used in various applications and / or permutations that may or may not be specifically described in the exemplary approaches enumerated herein. Furthermore, the magnetic recording medium 1000 presented herein may be used in any desired environment. The magnetic recording medium 1000 in various permutations disclosed herein has been developed to improve the stability and performance of tape storage media in the required environment for use and storage.

[0069] Unless otherwise stated herein, the various layers of the magnetic recording medium 1000 may be of conventional construction, design, or function, or a combination thereof. In various approaches, new and novel layers may be used in conjunction with conventional layers. In further approaches, multiple new and novel layers may be used in conjunction with conventional layers.

[0070] Unless otherwise specified herein, the various layers of magnetic recording medium 1000 may be formed using conventional methods, particularly if each layer is of conventional construction.

[0071] The magnetic recording medium 1000 is preferably a magnetic recording tape, but in other embodiments is a different type of deformable medium.

[0072] As shown in FIG. 10, there are four basic layers in the magnetic recording medium 1000. An optional backcoat 1002 is positioned along one side (the bottom side in the figure) of a substrate 1004. An underlayer 1006 is positioned along the other side (the top side in the figure) of the substrate 1004. A recording layer 1008 is positioned above the underlayer 1006. Additional layers of conventional configurations may be present in the magnetic recording medium 1000, in a variety of approaches. For example, to enable recording on both sides of the final tape, the backcoat may be removed and multiple layers may be placed on both sides of the substrate. Backcourt

[0073] The magnetic recording medium 1000 may or may not have a backcoat 1002. The backcoat 1002 may be of conventional construction, design and function, but in some approaches may have a conventional composition including conductive carbon black dispersed in a polymer binder system as has been commonly practiced in the industry for decades, although any conventional backcoat material may be used. Preferably, the backcoat 1002 is constructed of a material that provides one or more of the following advantages: ease of separation from other portions of the tape on the spool, improved friction, dissipation of static electricity, etc. The preferred thickness of the backcoat 1002 is less than about 0.3 microns, and preferably less than about 0.2 microns. substrate

[0074] The substrate 1004 is preferably of conventional construction, design and function. The substrate 1004 is typically the thickest layer. Exemplary materials for the substrate 1004 include polyethylene terephthalate (polyester or PET), polyethylene naphthalate (PEN), super-tensilised PEN, aramid-like materials (e.g., solubilized paramides such as those sold under the trade name Miktron® by Toray Industries, Inc., 2-1-1 Nihonbashi Mitsui Tower, Muromachi 2-chome, Chuo-ku, Tokyo, Japan 103-8666, Japan), and the like. Lower tier

[0075] The underlayer 1006 provides one or more of the following functions in the structure: attenuation of the magnetic signal passing through the recording layer, adhesion of the recording layer to the substrate 1004, etc. Thus, in most approaches described herein, the function of the underlayer 1006 is not to retain any memory of the writer flux, but rather to improve the write flux box from the write head element during writing to the recording layer 1008. Furthermore, any retained magnetic moment orientation resulting from writing is preferably weak or nonexistent to minimize noise during readback.

[0076] One very important attribute of the magnetically filled coating in the underlayer, by various approaches, is that it quickly absorbs stray magnetic fields that pass through the recording layer above during the very abrupt magnetic switching encountered during writing. An ideal underlayer would have a very low remanent moment (M) so that it does not maintain orientation after the write field has passed through its volume in the underlayer. r ) must be present.

[0077] In some approaches, the sub-layer 1006 has a new and novel composition. The new and novel sub-layer 1006 may, in some embodiments, be present in the medium 1000 with a conventional recording layer 1008 thereon. In other embodiments, the new and novel sub-layer 1006 may be present in the medium 1000 with a new and novel recording layer 1008 thereon. In other approaches, the sub-layer 1006 has a conventional composition and is present in the medium 1000 with a new and novel recording layer 1008 thereon.

[0078] In various approaches, the underlayer 1006 has one or more of the following properties, and preferably all of the following properties: it is electrically conductive and weakly magnetic (bulk magnetic strength less than 200 Oersteds (Oe), preferably less than 100 Oersteds). Ideally, the underlayer is coated and calendered before the recording layer 1008 is formed thereon to improve the interface with the recording layer 1008, as described in more detail below. In a preferred embodiment, the underlayer 1006 has a coercivity approximately 10 times lower in Oersteds than the recording layer 1008, and a low remanent magnetization that allows the underlayer 1006 to act as a magnetic flux sink for magnetic fields without causing signal interference with the recording layer 1008 above it.

[0079] The conductive property serves to reduce corrosion of the magnetic head operating against the tape. In particular, when the tape is unwound, separation of the recording layers creates frictional potentials and currents that generate static discharges in dry environments and electrochemical pathways to head corrosion in wet environments. Both of these conditions are undesirable for tape performance and durability, and both are believed to be significant contributors to head corrosion. The conductivity of the underlayer 1006 allows charge to be dissipated, for example by carrying the charge to the grounded hub, thereby minimizing charge migration into the head and reducing the risk of condensed fluid water forming a conductive path between the tape and head surface that would provide a path to electrochemical corrosion of the recording head structure.

[0080] The weak magnetic properties reduce the amount of noise contributed by the magnetic field emanating from the sublayer 1006, improving the resolution of written bits in the recording layer above the sublayer.

[0081] In some approaches, the underlayer 1006 has a conventional composition, typically using low coercivity and low moment particles in the micron size range. The coating is not optimized for high loading of very small (nano scale) particles. In some approaches, the underlayer is composed of weakly magnetic iron oxide using a conventional polyester-polyurethane rubbery resin with a poly(vinyl acetate-vinyl alcohol-vinyl chloride) hard resin cured with poly(isocyanate) used in previous tape product formats. However, such conventional coatings are not specifically designed or formulated to be optimal underlayers for the signal recording layer overlying them in the final tape.

[0082] In a preferred approach, the underlayer 1006 comprises a novel composition including particles 1010 dispersed in a low stress UV cured matrix such that the underlayer 1006 is weakly magnetic but also electrically conductive, provides sufficient adhesion to the substrate, and provides mechanical stability and stress relief for the very thin recording layer overlying it.

[0083] The underlayer 1006 does not need to have a narrow distribution in nanoparticle size in various approaches, although the use of small particles improves the surface roughness presented to the recording layer when the recording layer is applied. With the novel manufacturing process described herein, the underlayer 1006 is not attacked (swelled by the recording layer during application thereover).

[0084] In a preferred approach, the sublayer 1006 includes a novel composition including encapsulated nanoparticles 1010, each containing at least one magnetic nanoparticle 1012, preferably only one magnetic nanoparticle 1012, encapsulated by an aromatic polymer 1014. A polymer binder 1016 binds the encapsulated nanoparticles together in the sublayer 1006.

[0085] The average concentration of encapsulated nanoparticles in the lower layer 1006 is preferably at least about 35% by volume, such as 40%, 45%, 50%, 55%, 60%, greater than about 60%, in the range of about 40-75% by volume, in the range of about 45-75% by volume, in the range of about 50-75% by volume, in the range of about 35-50% by volume, in the range of about 40-60% by volume, or any other subrange within the ranges mentioned above. Ideally, the average concentration of encapsulated nanoparticles does not exceed the critical pigment volume concentration (CPVC) at which the coating loses its mechanical integrity and no longer functions as a viable, durable coating. In the case of nanoparticle-filled coatings, the very large surface area can dramatically reduce the CPVC unless novel encapsulation of nanoparticles and binder designs are implemented to allow for a higher CPVC. The CPVC can be determined using dynamic mechanical analysis (DMA) of the free film of the coating for a series of coatings with increasing volume percentages of filler. Conventional DMA techniques can be used with the novel formulations described herein. The CPVC is determined at the volume % where the tensile storage modulus (E') reaches its maximum value. Figure 11 shows a DMA plot 1100 of the CPVC for various volume % of pigment in the sublayer by various approaches. This plot 1100 is illustrative of a plot that one of ordinary skill in the art may generate by following the teachings herein and using conventional DMA plot techniques without resorting to undue experimentation.

[0086] The magnetic nanoparticles preferably comprise a weakly ferrimagnetic material. By the term "weakly ferrimagnetic" is meant magnetic nanoparticles that have a high coercivity (H c ) or magnetic moment (Mr ), but has an average magnetic field strength that contributes minimal signal during readout of the overlying recording layer. The final coating ideally provides no detectable noise signal contribution to the observed response to written bits in the data storage layer.

[0087] In a preferred approach, the magnetic nanoparticles have a coercivity (H c ), more preferably less than 100 Oersted and greater than 50 Oersted. An exemplary range of magnetic field strength for the magnetic nanoparticles is 50-200 Oersted. The magnetic nanoparticles are also preferably characterized by a low remanent moment, e.g., less than 12 emu / g.

[0088] A preferred material for magnetic nanoparticles is chromium dioxide, which is weakly magnetic, electrically conductive, and very hard. In another approach, the magnetic nanoparticles include one or more of the magnetic metal particles having an oxidized outer surface or oxide thereon (at the expense of electrical conductivity), such as cobalt, nickel, or iron, and their alloys.

[0089] The average diameter of the magnetic nanoparticles is preferably in the range of 2 nanometers (nm) to 20 nm, more preferably 4 nm to 10 nm, depending on the material, although the average diameter may be higher or lower in some approaches. A consideration regarding the average diameter is that the smaller the size, the more difficult it may be for the binder to adequately hold the pigment in the coating matrix. Thus, the average diameter of the magnetic nanoparticles should be selected to keep the marginal pigment volume within an acceptable range. If the average diameter is too small, there may be insufficient binder between adjacent particles, making the material brittle and prone to breakage. If the particles are too large, the interface between the underlayer 1006 and the recording layer 1008 loses the desired flatness characteristic described herein.

[0090] In a preferred approach, the magnetic nanoparticles present in the underlayer are formulated to be weakly magnetic, electrically conductive, and to result in a dried coating with negligible or no swelling by the solvent used to apply the recording layer. The use of nanoparticles in the underlayer is preferred using larger particles to allow for a flat interface with the recording layer.

[0091] The encapsulated nanoparticles in various preferred implementations can have a wide distribution of sizes, so long as the resulting dried film does not exceed a critical pigment volume concentration.

[0092] Preferably, the majority of the particles in the underlayer 1006 are coated with enough binder to achieve a cohesive and stable coating, with only a minimal number of particles in the coated particle clusters or agglomerates. An ideal coating would have close to 100% of the particles completely dispersed as individual particles in the binder matrix, with no clusters or agglomerates in the final coating. Proper particle dispersion in the matrix and minimal particle orientation reduces the contribution of underlayer noise to the recorded signal in the recording layer.

[0093] Again, preferably, the encapsulated nanoparticles are not well aligned with respect to one another, e.g., randomly oriented in the sublayer 1006. This further improves the performance of the sublayer by suppressing the formation of oriented magnetic domains in the sublayer 1006, thereby reducing noise generated in the sublayer 1006. However, while it is desirable to produce a monodisperse, non-agglomerated dispersion of encapsulated particles in preparation for coating, this is not necessary for the sublayer since mechanical properties are more important than magnetic signal performance.

[0094] The aromatic polymer that encapsulates the magnetic nanoparticles can be and / or include any of a number of different aromatic polymers, so long as the aromatic polymer encapsulates at least about 80% of the surface of the magnetic nanoparticles, preferably at least about 90% of the surface of the magnetic nanoparticles, and ideally nearly 100% of the magnetic nanoparticles in the underlying layer 1006. Thus, the aromatic polymer forms at least a partial shell, and preferably a complete shell, around the magnetic nanoparticles.

[0095] The layer that encapsulates the nanoparticles can be as thin as a monolayer, e.g., less than 0.4 nm, but a more robust layer is achieved with a thickness of about 1-2 nm. As the layer gets thicker, the loading of the nanoparticles into the coating decreases. This is not a critical issue in the lower layer, because the lower layer is not the recording layer.

[0096] The average thickness of the aromatic polymer encapsulating the magnetic nanoparticles is preferably in the range of about 0.5 nm to about 8 nm, e.g., 1-4 nm, 3-5 nm, 4-5 nm, 4-7 nm, 5-7 nm, etc., but can be slightly higher or lower than these ranges. Thickness, as used herein, generally refers to the thickness of the deposition over underlying structures unless otherwise specified.

[0097] Aromatic polymers are suitable as sealing layers because the aromatic ring structures seal the surface of the magnetic nanoparticles. Aromatic rings have excellent behavior, especially in relation to chemically reactive metal oxides such as chromium oxide, due to the unique properties of aromaticity in their molecules, which provide improved stability and some magnetic shielding at the surface of the magnetic nanoparticles when properly aligned with the magnetic axis of the magnetic nanoparticles. For example, aromatic ring structures can act as magnetic field modifiers due to their unique molecular electronic structure and ability to suppress external magnetic fields.

[0098] The aromatic polymer also provides magnetic shielding at the surface of the pigment, helping to isolate the magnetic nanoparticles from other particles to improve independent switching of the encapsulated nanoparticles, resulting in higher bit resolution.

[0099] A suitable aromatic polymer is a carbamate. A suitable example of an aromatic molecule known to react with chromium dioxide particles to effectively encapsulate the particles and isolate them from their neighbors in a close-packed matrix is ​​methylene bis diphenyl carbamate. Ideally, the encapsulating polymer will be composed of methylene bis diphenyl carbamate along with a functional acrylic polyester as the ester segment for the aromatic carbamate when used with chromium dioxide nanoparticles. Upon UV irradiation, polymerization at the particle surface can proceed to form an encapsulating polymer film layer.

[0100] In particular, for use with chromium dioxide magnetic nanoparticles, the aromatic polymer is preferably an aliphatic-substituted aromatic, which has an oxidizable moiety that reacts with chromium, for example, thereby aiding in the absorption of the aromatic polymer into the chromium dioxide microparticle. The benzylic carbon of diphenyl methane dicarbamate is known to be efficiently oxidized by chromium dioxide, ensuring the binding of the resulting diphenyl ketone to the particle surface.

[0101] In other approaches, aromatic polymers contain reactive functional substituents such as amine, alcohol, carboxylic acid or nitrile groups. One example is cinnamic acid, which exists as a copolymer with styrene that forms a polymer layer attached onto the nanoparticle surface.

[0102] In yet another approach, the aromatic polymer contains one or more repeat units with substituents capable of chemically adsorbing and / or bonding to the particle surface, such as amines, carboxylic acids such as cinnamic acid, and other functional aromatics that bind to the surface of the magnetic nanoparticles being used.

[0103] In alternative implementations, the encapsulation layer of the encapsulated particulates may be a copolymer, such as a polyester-polyurethane or an acrylic modified polyurethane, rather than an all-aromatic polymer. Examples include known types of aliphatic polymers, known types of non-aromatic polymers, etc.

[0104] The polymer binder that holds the encapsulated nanoparticles together can be and / or include various types of binder materials. In a preferred approach, the binder comprises an acrylic polymer, e.g., an acrylic acid or acrylate polymer, preferably a functional acrylic polymer. Exemplary acrylic polymers suitable for use as binders in the various approaches include components such as methyl methacrylate, acrylic acid, etc. In general, suitable polymer binders are those having a number average molecular weight of less than about 2400, preferably less than about 1200.

[0105] In a preferred implementation, the polymer binder has a UV curing functionality that allows for bonding of the encapsulated particles to the encapsulation layer. This functionality can be provided by acrylate groups, vinyl, etc.

[0106] In some approaches, the binder includes vinyl chloride, vinyl acetate-vinyl alcohol copolymers. In yet other approaches, the binder includes polyester or polyether polyurethanes. For nanoparticle filled coatings, the polymer is of much lower molecular weight (size) than traditionally used materials. Typically, useful polymers are less than 20 repeat units in length before UV curing.

[0107] The relative amount of encapsulated nanoparticles to binder in the underlayer 1006 should be in a range that does not exceed the critical pigment volume concentration (CPVC). Once one is aware of the novel formulations described herein, one of ordinary skill in the art will be able to calculate the CPVC using known techniques based on the properties of the materials used, such as the binder used, the surface area of ​​the particles, etc. A general rule of thumb is less than about 50% by volume pigment (encapsulated nanoparticles) in the underlayer 1006, which maintains the structural integrity of the underlayer 1006, improves tape durability, and provides adhesion of the recording layer 1008, along with other functions of the underlayer 1006, such as structurally stabilizing the magnetic layer. The pigment loading is preferably high enough to provide adequate mechanical integrity as measured using DMA, and sufficient conductivity to mitigate undesirable triboelectric properties.

[0108] Additional materials may be present in the sublayer 1006, such as migration lubricants and / or stabilizers used for stability of the dispersion prior to application and curing.

[0109] The resulting underlayer 1006 is preferably characterized by a dispersion of encapsulated nanoparticles (encapsulated nanoparticles) in a weakly magnetic, electrically conductive, binder tightly bound to the pigment to achieve a dried coating with an onset glass transition temperature Tg on a graph of tensile storage modulus (E') versus temperature from 0 to 60 degrees Celsius. Tg should be greater than 35 degrees Celsius, and preferably greater than about 45 degrees Celsius, and should be an absolute value for E' measured at 10 Hz via DMA at about 20 degrees Celsius, from at least about 6 gigapascals (GPa) to about 16 GPa or slightly higher, such as about 8 GPa, about 10 GPa, about 11 GPa, about 12 GPa, about 15 GPa, about 16 GPa, etc. In most approaches, the normal operating range for the tape falls in the range of 0 to 60 degrees Celsius, but can be higher or lower.

[0110] Binders used in conventional magnetic recording tapes result in an underlayer 1006 that has a glass transition temperature of 20-30 degrees Celsius. This is too soft, resulting in an underlayer 1006 that is too flexible to provide a stable and consistent recording medium during use. However, the underlayer 1006 must be sufficiently elastic to be robust and durable during use and storage. Thus, the preferred embodiment results in an underlayer 1006 that has an onset Tg determined by a DMA plot of E' vs. temperature that is greater than about 35 degrees Celsius, and preferably a very broad response suitable onset Tg that remains in the flexible range up to at least 50 degrees Celsius at 10 Hz.

[0111] The average thickness of the lower layer 1006 is less than 1 micron, and preferably less than about 0.6 microns, a thinner thickness being preferred to allow more tape to be wound into a fixed volume of a given tape cartridge.

[0112] In a preferred approach, there are no wear particles in the underlying layer 1006, and ideally there would be no wear particles in the product at all. Previously, wear particles added for purposes of cleaning the tape head and / or reducing stiction have been found to be an increasingly unacceptable source of defects and damage to shrinking read and write structures in current and future recording heads. However, in other approaches, wear particles may be present in the underlying layer 1006.

[0113] The underlayer 1006 is preferably applied to the substrate 1004, at least partially dried, and cured before being applied to the magnetic recording layer 1008 to minimize turbidity between the layers. Thus, in a preferred approach, the recording layer 1008 is substantially not intermixed with the underlayer 1006 (and vice versa). This feature overcomes a long-standing problem in magnetic recording tape production.

[0114] Referring to FIG. 12, a TEM image of a cross section of a conventional recording tape 1200 is shown. As shown, the interface between the recording layer and the underlying underlayer is well defined. The bright particles in the recording layer are barium ferrite particles. As shown, the barium ferrite particles are not monodispersed or densely packed in the recording layer. Furthermore, voids exist where there are no particles. Also, the interface between the recording layer and the underlayer is fairly rough. Ideally, the magnetic field would pass through the recording layer perfectly perpendicular from the writer. Unfortunately, the magnetic field expands or curves as it exits the writer, and the curvature becomes more severe the further away from the tip of the writer pole. The voids, the wavy interface between the recording layer and the underlayer, and the uneven distribution of magnetic particles all produce the effect of an expanding writer field. If a transition is written (e.g., the write field points down and then points up as the tape passes the writer) and the field expands, say by 10-20%, as it passes the recording layer, the transition is not sharp and reduces the resolution of the tape. During read-back, the transition is not sharp and therefore noisy. A 1 dB improvement in signal-to-noise ratio (SNR) during read-back is a significant achievement. The inventors believe that with the new and novel recording layer described herein, which is formed on a hardened underlying layer to minimize interlayer turbidity, the signal-to-noise ratio (SNR) during read-back may improve by as much as 5 or 6 dB.

[0115] In a preferred approach, the upper surface of the underlying layer is substantially flat and varies less than about 25% of the thickness of the interface between the layers, preferably less than about 5%, when imaged in a TEM cross section of the final tape coating, such as the upper surface of the recording layer shown in Figure 12. Process for manufacturing the lower layer

[0116] Methods for manufacturing, for example, a sublayer 1006 of a magnetic recording medium according to various approaches are presented below. Optionally, the method according to the present invention can be implemented to manufacture a sublayer 1006 such as the one described above. However, it is of course possible that this method and other methods presented herein can be used to form a sublayer 1006 that may or may not be related to the exemplary embodiments listed herein. Furthermore, the methods presented herein can be performed in any desired environment. Also, according to various approaches, the method may include more or fewer operations than those described below. It should be noted that any of the features described above may be used in any of the approaches described according to various methods.

[0117] The method generally includes forming an underlying layer 1006 having encapsulated nanoparticles, each of which includes at least one magnetic nanoparticle encapsulated by an aromatic polymer, and a polymer binder that binds the encapsulated nanoparticles together.

[0118] The encapsulated nanoparticles can be purchased or can be manufactured, for example, some approaches use commercially available encapsulated nanoparticles that can be used for medical imaging and drug delivery applications.

[0119] In one approach, forming the sublayer 1006 includes mixing a polymer binder with the encapsulated nanoparticles and a solvent (solvent system) to form a mixture. The relative amounts of the encapsulated nanoparticles and binder are preferably selected to provide the properties listed in the previous section. For example, the mixing may include ultrasonically dispersing the encapsulated nanoparticles in the polymer binder and solvent to produce a radiation curable emulsion in the solvent.

[0120] Conventional coating methods would require formulation to achieve useful viscosities and would likely require binders with much higher molecular weights than would be optimal for current target designs for advanced tape constructions. As a result, described herein are examples of formulations that are not suitable for conventional coating. All of the examples are most suitably applied to a substrate as a sprayed aerosol coating, although other coating methods are contemplated.

[0121] In general, the solvents used herein should provide one or more, and preferably all, of the following properties: swell the polymer binder, but allow the polymer to collapse around the pigment during drying rather than shrinking. The solvent causes the polymer binder chains to free up and move in a direction toward their θ condition (minimum free volume).

[0122] The layer is most stable when the polymer binder is in the θ condition, at which point curing should occur. When the polymer binder is close to its θ condition, UV curing is preferred due to the speed at which curing occurs.

[0123] One of the solvent components should be a suitable solvent for the binder additive, helping to suspend the polymer-encapsulated magnetic particles. The second solvent can be a non-solvent for the polymer binder. When the "suitable" solvent phase evaporates, the remaining coating approaches a non-solvent dominated coalesced coating. The second solvent-rich coating thus passes a point in the drying process where the binder and encapsulated magnetic particles are near their minimum free volume or θ condition. This creates minimal residual stress in the final dried coating, which in turn eliminates curl and warping in the final tape.

[0124] A preferred solvent is a water and tetrahydrofuran (THF) solvent system in relative concentrations that make the solvent system almost completely azeotropic. This solvent system is preferred for use with acrylic polymer binders because it dries well, is environmentally friendly, consumes less energy, and, as an azeotrope, is less susceptible to combustion or explosion. A THF / water solvent is also preferred because during drying, the THF leaves first, followed by the water, which helps to maintain the binder toward the theta condition. Specifically, THF leaves first because it is more volatile than water. The organic solvent leaves first, allowing the film to collapse and reduce stress, and the water dominates the solvent interface, allowing the polymer to approach the theta condition.

[0125] For example, a slight increase in the water ratio to the azeotrope concentration of 6.7% by weight is required to provide optimal coating drying. This results in a solvent mixture ranging from 92-93% THF to 7-8% water drying at 64 degrees Celsius. This lower drying temperature has the added benefit of reducing operating costs compared to current magnetic tape coating processes.

[0126] The resulting mixture (pigment + solvent) is applied onto a structure such as substrate 1004. Any suitable technique can be used to apply the mixture. When the pigment and solvent mixture forms an emulsion, a preferred technique is spray coating, which provides fast, uniform application without the streaks typical of brush coating or the lumps typical of blade coating. Other application techniques include blade coating, slot die coating, use of a gravure roll, and the like.

[0127] In another approach, forming the underlayer 1006 includes mixing the encapsulated nanoparticles with a polymer binder to form a fine suspension without the need for adding dispersants or other additives to produce a stable dispersion.

[0128] The applied mixture is dried to remove at least a portion of the solvent or to substantially completely dry it. For example, the applied mixture may be dried to increase the non-solvent content in the drying film by removing more volatile organic solvents (e.g., THF). The polymer binder disintegrates between the encapsulated particles as the solvent is removed during drying. For example, in embodiments where the binder is hydrophobic, the last solvent to leave the applied mixture is water, which is a non-solvent for the binder, forcing the hydrophobic binder to disintegrate onto the pigment. This also minimizes residual stresses in the dried coating, thereby preventing the tape from curling. Drying is preferably performed with forced air under cool conditions (less than about 75 degrees Celsius).

[0129] The partially dried coating, which will ultimately provide the sublayer for the magnetic recording layer, may be cured using, for example, a heat-induced chemical reaction that cures the two layers, a radiation-induced chemical reaction that cures the two layers, etc. For example, exposure to UV light or other known radiation may be applied to cause crosslinking of the polymer binder. If appropriate solvent selection is made for both coatings, the curing step results in minimal stress between the two layers, resulting in a stable (flat) coating.

[0130] In the case of thermally induced curing, chemical reactions can be used to reduce solvent swelling in the coating and improve the mechanical properties of the cured coating. Chemical curing in dry films is slow and inefficient in achieving the desired uniformity of the cured highly filled coating. A preferred approach is to use radiation induced chemical curing. Fortunately, current and future magnetic recording layers used in tape applications are all thin enough today to allow efficient transport of light through the coating and cause chemical reactions within the binder rich regions that are the target of such curing reactions. It is widely known that ultraviolet (UV) radiation can activate the formation of free radicals that can attack unsaturated carbon bonds such as olefins, vinyls and acrylics to initiate polymerization of these reactive species to form more robust molecular structures. UV curing is also preferred because during free radical formation, the underlying layer 1006 also bonds to some substrates 1004, which can improve the durability of the tape.

[0131] After the underlayer 1006 is cured, a magnetic recording layer 1008 is formed on or above the underlayer 1006. By drying and curing the underlayer 1006 before forming any type of magnetic recording layer 1008 thereon, interlayer turbidity at the interface between the underlayer and the recording layer is minimized, thereby overcoming a problem prevalent in conventional magnetic recording tape manufacturing that results in limited achievable areal recording density of the tape.

[0132] In one exemplary approach, nanoparticles of a weakly magnetic material (chromium dioxide) are coated with an aromatic polymer shell (methylene bis diphenyl carbamate with a functional acrylic polyester as the ester segment to the aromatic carbamate) and interconnected with the functional acrylic polymer. The above blend of materials is dispersed in an ultraviolet (UV) curable emulsion in a tetrahydrofuran (THF) and water solvent system using ultrasonic dispersion, applied onto a substrate 1004, dried, and cured. The dried coating has pigments encapsulated with aromatic glassy polymer such that the matrix is ​​highly filled with magnetic and conductive pigments to greater than 40% while maintaining a resilient, rubbery interparticle matrix formed from the polyester-acrylic salt domains of the carbamate binder. Process for producing encapsulated magnetic nanoparticles

[0133] In various approaches, base magnetic nanoparticles are prepared using known techniques, such as milling, that are subsequently encapsulated using any of the novel processes disclosed herein. In another approach, the base magnetic particles are obtained in a ready to use form and are encapsulated using any of the novel processes disclosed herein.

[0134] The formation of encapsulated magnetic nanoparticles can be carried out using a variety of techniques. Previous approaches to encapsulating magnetic nanoparticles have been unsuccessful. Rather than attempting to maintain isolation of the encapsulated nanoparticle precursors (not yet converted to the final magnetic state by high heat conversion), a preferred approach is to mix the magnetic nanoparticles with an organic solvent in the presence of an aromatic dispersant. Absorption of the aromatic species to the nanoparticles allows for a stable suspension of the particles in an initial solvent such as toluene, which is a good solvent for many suitable aromatic dispersants. This mixture is heated with ultrasonic dispersion energy applied to maintain the suspension. A high boiling aromatic hydrocarbon, such as anthracene, phenanthrene, pyrene, etc., is added to an approximately correct volume of toluene prior to distillation. The mixture is heated above the boiling point of toluene and the toluene is removed by distillation, leaving a molten suspension of dispersed nanoparticles in a melt of a fully aromatic polyaromatic, such as molten phenanthrene, which has a melting point above about 380 degrees Celsius.

[0135] In one exemplary approach, the mixture is heated in a pressure vessel to 400 degrees Celsius and held there for 4-6 hours. The iron nanoparticles are converted to the magnetic epsilon form of iron oxide. This process keeps the magnetic particles surrounded by a fully aromatic shell.

[0136] The mixture is then cooled to room temperature before processing is carried out to extract the encapsulated particles. Once cooled to room temperature, the waxy solid with the dispersed nanoparticles is dissolved in a solvent such as toluene to obtain a dispersion of the nanoparticles in the solvent with the aromatics once again mixed in. To this, sufficient chloroform or the like is added to allow the aromatic layer to separate and be poured off from the particles suspended in the chloroform.

[0137] The dried particles can be recovered by distillation of the chloroform or, if the aromatic sealing layer is modified to have sufficient remanence to allow stable dispersion in water, by exchange into water so that the suspension maintained by the solvent forms an emulsion. Recording layer

[0138] In some approaches, the recording layer 1008 has a new and novel configuration. The new and novel recording layer 1008 may, in one embodiment, be present in the medium 1000 with a conventional underlayer 1006 below it. In another embodiment, the new and novel recording layer 1008 may be present in the medium 1000 with a new and novel underlayer 1006 below it. In other approaches, the recording layer 1008 has a conventional configuration and is present in the medium 1000 with a new and novel underlayer 1006 below it.

[0139] In an approach where the recording layer 1008 has a conventional construction, a dispersion of weakly magnetic particles dispersed in a binder system that does not attempt to seal the particles in a glass sealing layer prior to dispersion may be used as a flux distribution layer, as has been done in current tape media construction for over a decade. These sublayers may or may not have additional particles added for improved conductivity or polishing strength.

[0140] In a preferred approach, the recording layer 1008 comprises a novel composition in which the recording layer 1008 includes encapsulated nanoparticles 1018, each containing at least one, and preferably only one, magnetic nanoparticle 1020, encapsulated by an encapsulation layer 1022, and a polymer binder 1024 that binds the encapsulated nanoparticles together. In general, the magnetic strength of the magnetic nanoparticles in the recording layer 1008 is significantly higher than the magnetic strength of the nanoparticles in the underlying layer 1006, if present.

[0141] The average concentration of encapsulated nanoparticles in the recording layer 1008 is preferably at least about 35 weight percent (wt%), for example, in the range of about 45-50 wt%, about 30-50 wt%, preferably about 46-50 wt%, or any other subrange within the above ranges.

[0142] The magnetic nanoparticles in the encapsulated nanoparticles of the recording layer 1008 can be constructed of any magnetic material suitable for the intended application, such as magnetic recording. Additionally, magnetic materials that can be used in magnetic imaging can be used in the magnetic nanoparticles in some approaches. In various approaches, the magnetic nanoparticles include at least one magnetic material selected from the group consisting of alloys or oxides of nickel, cobalt, and iron, or combinations thereof, including mixed compounds, and crystals using combinations of nickel, cobalt, and iron, such as barium iron, NiFe, barium ferrite, and cobalt platinum.

[0143] The approach described herein is compatible with other nanoparticles, such as MnAl, which are not typically useful for tape storage layers at present, and SiC and SiO, which are useful for sandpaper and other abrasives. 2 It should be noted that this is applicable even to non-magnetic dispersions that can benefit from improved control of coating integrity such as dispersion, etc. Thus, any known type of magnetic nanoparticle can be used in the various approaches.

[0144] In a preferred approach, the magnetic nanoparticles are Co 3 O 4 , CoFe, Fe 3 O 4 , alpha-iron oxide (α-Fe 2 O 3 ), epsilon-iron oxide (ε-Fe 2 O 3 In other approaches, the magnetic nanoparticles may include manganese-aluminum alloys, oxides of magnetic metals, and spinel ferrites.

[0145] The average diameter of the magnetic nanoparticles in the recording layer 1008 is preferably in the range of about 2 nm to about 20 nm, and particularly for epsilon-iron oxide particles, preferably in the range of about 2 nm to about 10 nm. The average diameter can be higher or lower than this range, depending on the size at which the magnetic nanoparticles lose their remanent polarization and become superparamagnetic. In general, a smaller average radius is better for increasing bit resolution.

[0146] Preferably, the encapsulated nanoparticles used in the recording layer have the same composition, crystal structure and morphology, and have a very narrow particle size range, so as to optimize the response of the final recording layer to the external magnetic field applied during data writing.In a preferred approach, more than about 80% of the encapsulated nanoparticles have only one magnetic nanoparticle therein, more preferably more than about 90%, even more preferably more than about 98%, and ideally at least about 100% of the encapsulated nanoparticles have only one magnetic nanoparticle therein.

[0147] As long as the aromatic polymer encapsulates at least about 75% of the surface of the magnetic nanoparticles, preferably at least about 90% of the surface of the magnetic nanoparticles, and ideally nearly 100% of the magnetic nanoparticles in the lower layer 1006, and especially for the optimization of the magnetic nanoparticles in the recording layer, the aromatic polymer encapsulating the magnetic nanoparticles can be any of many different aromatic polymers and / or can include any of many different aromatic polymers. In the recording layer, the efficiency of particle encapsulation should be close to 100% so as to be obtainable by a viable process that can be used to actually build large quantities. Thus, the aromatic polymer forms at least a partial shell, preferably a complete shell, around the magnetic nanoparticles. The average thickness of the aromatic polymer encapsulating the magnetic nanoparticles is preferably less than 1 nm in the final recording layer 1008. Preferably, the average thickness of the aromatic polymer shell is in the range of about 0.5 nm to about 1 nm, e.g., 0.5-0.75 nm, 0.6-0.8 nm, 0.7-1 nm, 0.8-1 nm, etc., but may be slightly higher or lower than these ranges. In some cases, clusters or aggregates of partially coated nanoparticles may form during the encapsulation process that may persist through the formation process to the final coating. As long as these clusters and aggregates are not a substantial proportion of the coating (e.g., less than 10% by volume) and are smaller than the final coating thickness (e.g., less than 60% of the thickness at the diameter of the final dried coating) so as not to cause surface roughness and defects, the presence of clusters and aggregates should not be a limitation on the desired functionality of the layer.

[0148] In embodiments in which the encapsulated nanoparticles are pyrolyzed, the average thickness of the resulting carbon shells ranges from about 0.05 nm to about 1 nm.

[0149] Such a thin shell can improve the packing density of the magnetic grains in the recording layer 1008 and therefore increase the recorded bit resolution.

[0150] Aromatic structures are preferred as encapsulation layers for the isolation of magnetic nanoparticles due to their unique electronic properties which, in the final closely packed dry coating, provide somewhat weak but significant isolation of each nanoparticle from the magnetic fields that bind them to their near neighbors.

[0151] The aromatic polymer preferably contains functional groups that have an affinity for attachment to iron oxides when iron magnetic nanoparticles are used. Exemplary functional groups include carboxylic acid functional groups, nitrile functional groups, and others.

[0152] A suitable aromatic polymer is a radiation curable substituted aromatic polymer. In another approach, the aromatic polymer is a styrene, such as polystyrene. Ideally, the aromatic polymer is polystyrene with a copolymer having rubbery polymer chains in the para positions on the styrene monomer. Preferably, the sealing layer comprises a polyaromatic film.

[0153] In another approach, aromatic polymers are known precursors that can be used to create graphite, carbon fibers, carbon nanotubes, etc. Thus, the encapsulation layer can be a graphite-like dominated continuous film.

[0154] The polymer binder that binds the encapsulated nanoparticles together can be and / or include various types of binder materials.

[0155] Approaches considered have attempted to incorporate encapsulated magnetic nanoparticles into conventional binder systems, but it has been discovered that such approaches result in recording layers with much more noise and much poorer signal performance than would be predicted from the assumption that the particles are smaller and more packed into the alignment layer. While the reasons for such poor performance in the conventional binder system approach are not fully understood, the inventors have found that the novel techniques described herein result in new recording layers that exhibit much better recording performance than the aforementioned approaches using conventional binder systems.

[0156] In a preferred approach, the binder comprises an acrylic polymer, preferably a functional acrylic polymer, such as an acrylic acid or acrylate polymer. In a particularly preferred approach, the polymer binder comprises a radiation curable rubbery acrylic polymer. Exemplary acrylic polymers suitable for use as binders in the various approaches include acrylic terminated polyesters and those containing moieties such as methyl methacrylate and acrylic acid. For example, the binder may comprise an acrylic terminated aliphatic polyester or aliphatic polyether polymer. In general, suitable polymer binders are those having a number average molecular weight of less than about 2400, preferably less than about 1200.

[0157] In various approaches, the binder used in the recording layer 1008 can be the same as or different from the binder used in the underlying layer 1006 .

[0158] The recording layer 1008 must be flexible (rubber-like in nature) over the operating temperature range in use while providing tear and impact resistance. Thus, preferred embodiments result in a recording layer 1008 that has a glass transition temperature above about 35 degrees Celsius, preferably above about 45 degrees Celsius, and ideally at least about 50 degrees Celsius. This can be achieved through binder selection.

[0159] Additional materials, such as lubricants, may be present in the recording layer 1008. However, one advantage of the various approaches disclosed herein is that they allow for the elimination of traditional additive materials, such as wear particles, in the recording layer.

[0160] The average thickness of the recording layer 1008 measured perpendicular to its formation surface is less than about 0.2 microns, and preferably less than 0.1 microns. One advantage of this thickness of the recording layer 1008 is that the UV light reaches all parts of the recording layer 1008, even the pigments therein, thereby ensuring fast and consistent curing throughout the layer. Conventional recording layers, due to their thickness, cannot be cured by UV and therefore rely on other types of curing that are not as fast. Thus, once a conventional tape is formed, curing continues as the tape is wound onto the spool. However, as the tape is wound onto the spool, tensions and pressures are created throughout the tape (e.g., radial compression), resulting in changes in the mechanical properties of the tape that vary from the tape inside the hub to the tape outside the hub.

[0161] If the recording layer 1008 is formed directly on the underlying layer 1006, the recording layer 1008 is preferably applied after the underlying layer 1006 has cured to minimize intermixing between the layers. Thus, in a preferred approach, the recording layer 1008 does not substantially intermix with the underlying layer 1006 (and vice versa).

[0162] Preferably, the sublayer 1006 has a bulk magnetic field strength, measured in Oersteds, of less than 200 Oersted, more preferably less than 100 Oersted. The sublayer 1006 may have similar composition and / or properties to the sublayers disclosed elsewhere herein.

[0163] In some embodiments, lubricant molecules 1030 are bound to the surface of the recording layer 1008. The lubricant molecules can be bound to the surface, embedded in the surface, or both. Preferably, the amount of lubricant molecules along the surface of the recording layer 1008 is less than would form a continuous lubricant film along the surface of the recording layer 1008.

[0164] In a preferred approach, there are no wear particles present in the recording layer 1008, and ideally there are no wear particles at all in the product itself. However, in alternative approaches, there may be wear particles present in the recording layer 1008 and / or pass through the recording layer 1008 from the underlayer 1006. The above mechanical design of the recording layer 1008 with the conductive underlayer 1006 is expected to achieve the desired low friction and head erosion characteristics of the tape surface without the need for the inclusion of wear particles, which constitute an increasingly unacceptable defect and source of damage to shrinking read and write structures in current and future recording heads. Process for manufacturing the recording layer

[0165] A method for manufacturing a recording layer 1008 of a magnetic recording medium according to various approaches is presented below. Optionally, the method can be implemented to manufacture a recording layer 1008 such as the one already described. However, it is of course possible that the method and the method presented herein can be used to form a recording layer 1008 that may or may not be related to the exemplary embodiments listed herein. Furthermore, the method presented herein can be performed in any desired environment. Also, according to various approaches, the method may include more or less operations than those described below. It should also be noted that any of the above-mentioned features can be used in any of the approaches described by various methods.

[0166] The method generally includes forming a magnetic recording layer 1008, the magnetic recording layer 1008 including encapsulated nanoparticles, each including at least one magnetic nanoparticle encapsulated by an aromatic polymer, and a polymer binder that binds the encapsulated nanoparticles together.

[0167] In one approach, forming the recording layer 1008 involves heating the magnetic nanoparticles and aromatic polymer to a temperature that results in the suspension of the magnetic nanoparticles in the aromatic polymer. Typically, for most aromatic polymers, this temperature ranges from about 200 degrees Celsius to about 538 degrees Celsius, depending on the aromatic polymer being used.

[0168] Where the aromatic polymer has a simple aromatic structure, temperatures below 200 degrees Celsius may be used. The relative amounts of magnetic nanoparticles and aromatic polymer in the suspension are preferably selected to provide the properties listed in the previous section and to avoid the formation of nanoparticle clusters.

[0169] An organic solvent may be mixed with the nanoparticles and aromatic polymer to create a suspension that avoids clustering and sintering of the nanoparticles. Such a solvent may include dissolved aromatic solvents such as phenanthrene. Preferably, the solvent is one that does not result in an oxidation reaction with the magnetic nanoparticles. Toluene or similar may be added to shift the mixture toward a more emulsion-like liquid.

[0170] In some approaches, the encapsulated particles are pyrolyzed, resulting in magnetic nanoparticles that are encapsulated in a carbon shell.

[0171] A warm suspension of magnetic nanoparticles and aromatic polymer is mixed with a polymer binder and a solvent to form a mixture. Ultrasonic dispersion is preferably used to create an emulsion. This technique of encapsulated nanoparticle synthesis and polymer encapsulation effectively eliminates the need for milling and redispersion of particles from agglomerated clusters, which is typical of conventional manufacturing techniques.

[0172] In general, the solvent mixture should provide one or more, and preferably all, of the following properties: the most volatile solvent (the first to leave during drying) will swell the polymer binder; the second or last to leave during drying is ideally a poor solvent for that binder, forcing the solution to pass through the theta condition for that binder during drying and forcing the binder to collapse around the pigment, rather than shrinking during drying and resulting in undesirable pressure in the final coating. The last solvent to leave during drying is a non-solvent for the binder, so it forces the swollen chains to coil and enter a minimum free volume state, referred to as the theta condition, as they move from being fully dissolved by the first solvent to being surrounded by a non-solvent rich environment during drying. The layer is most stable when the polymer binder is in the theta condition, and it is at this point that curing begins. UV curing is preferred when the polymer binder is close to its theta condition because of the speed at which curing occurs.

[0173] The preferred solvent is a water and THF solvent system with a slight excess of water in relative concentrations that make the solvent system predominantly azeotropic, to force the final dried coating to pass through theta conditions during drying. THF leaves first due to its higher volatility than water. The departure of the organic solvent allows the film coalescence to collapse and reduces the pressure. Thus, water dominates the solvent interface, allowing the polymer to approach theta conditions.

[0174] In other approaches, the solvent system may be dominated by water, in which case the coating is a true emulsion, with the imbibed binder acting as an emulsifier and providing the rubber phase resin in the final coating. In a further approach, useful solvents may include mixtures of volatile polar organics with higher boiling point non-solvents for the binder, such as MEK / toluene, acetone / methyl isobutyl ketone, etc.

[0175] The resulting emulsion / solvent is applied onto a structure such as the underlying layer 1006 described above or another substrate. Any suitable technique may be used to apply the emulsion / solvent. A preferred technique is specially designed low pressure, high volume spray coating, which provides fast, uniform application without the streaks typical of brush coating, or interfacial thickness variations and modulations caused by high shear blade or die extrusion coating methods for such very thin coatings.

[0176] The applied mixture is partially dried to remove at least a portion of the solvent or is substantially completely dried. The polymer binder collapses onto the encapsulated particulates as the solvent is removed during drying. For example, in embodiments where the binder is hydrophobic, it is water, a non-solvent for the binder, that leaves the applied mixture last, which forces the hydrophobic binder to collapse onto the pigment. This also minimizes residual pressure in the dried coating. Drying is preferably performed with forced air under cool conditions (less than about 75 degrees Celsius).

[0177] The at least partially dried applied mixture is cured to limit further expansion or contraction in the as-coated, pressure-relieved layer during subsequent processing and exposure to environmental stresses, producing a thin, dense recording layer 1008 with closely packed magnetic nanoparticles. In one approach, the at least partially dried applied mixture is exposed to radiation, e.g., UV light or other known radiation exposure is applied to cause crosslinking of the polymer binder. In another approach, a different curing process is performed by applying heat to increase the reaction of the thermally reactive functional groups in the encapsulated nanoparticle layer with the rubbery binder phase of the dried film.

[0178] Optionally, lubricant may be added during formation of the recording layer 1008, with lubricant molecules 1030 eventually becoming bound to the surface of the recording layer 1008 as it is formed. The lubricant molecules may be bound to the surface, embedded in the surface, or both. Again, preferably, the amount of lubricant molecules along the surface of the recording layer 1008 is less than that which would form a continuous film of lubricant along the surface of the recording layer 1008. In one exemplary approach, the lubricant molecules are positioned to be spaced apart along the surface of the recording layer 1008 such that, on average, the lubricant molecules are spaced apart from one another along the surface of the recording layer 1008 at a distance in the range of about 2 to about 15 molecule radii from center to center.

[0179] In one approach, the lubricant molecules 1030 are dispersed in an organic solvent phase and are delivered to the surface during drying where they are implanted onto the surface during curing to form a stable low friction layer without transferring the lubricant molecules to the drive bearing and head surface, which in turn reduces contamination of the head.

[0180] In another approach, the lubricant is applied to the outer surface of the completed recording layer 1008 .

[0181] In one exemplary case, Co was encapsulated with an aromatic polymer. 3 O 4 , CoFe, Fe 3 O 4 A primarily monodisperse suspension of magnetic nanoparticles, such as Co(fcc), is mixed with a rubbery polymer that has radiation-curable end groups and side chains of sufficient chain length to provide a rubbery phase when bonded to the radiation-curable end groups on the aromatic encapsulation layer of the dispersed nanoparticles during curing. The resulting suspension is used to build a densely packed thin recording layer 1008 capable of high density recording. The rubbery chains attached to the aromatic encapsulation layer are terminated with acrylic or methacrylic functionalities that can be UV cured to form a highly crosslinked matrix in which the magnetic nanoparticles are fully encapsulated by an aromatic glassy polymer, e.g., a low molecular weight polyester with acrylic ends added in a solvent, which is held in a coherent coating through swelling of the rubbery phase. UV curing of the solvent swollen coating and polyester is performed during drying.

[0182] Compared to current magnetic recording media, various advantages of the magnetic recording tape having the new underlayer and the new recording layer thereon include, but are not limited to, one or more of the following: a thinner recording layer, a more uniform distribution of magnetic particles, a flatter layer, less turbidity at the interface between the underlayer and the recording layer, a higher glass transition temperature, less or substantially no voiding of magnetic particles in the recording layer, etc. Each of these advantages results in a magnetic recording tape that exhibits properties such as, but not limited to, one or more of the following: greater dimensional stability, greater tear resistance, recording resolution down to less than 1 nm, lower noise resulting in a higher signal-to-noise ratio, etc.

[0183] It will be apparent that the various features of the systems and / or methods described above may be combined in any manner, thereby resulting in multiple combinations from the description provided above.

[0184] It will be further appreciated that embodiments of the present invention may be provided in the form of a service deployed on behalf of a customer.

[0185] The inventive concepts disclosed herein have been presented by way of examples illustrating its myriad features as a number of example scenarios, embodiments or implementations or combinations thereof. It should be understood that the concepts disclosed generally should be considered modular and may be implemented as any combination, permutation or composition thereof. Furthermore, any modifications, variations or equivalents of the features, functions and concepts disclosed herein that may be understood by a person skilled in the art upon reading this description should be considered to be within the scope of the present disclosure.

[0186] Descriptions of various embodiments of the present invention have been presented above for illustrative purposes, but are not intended to be exhaustive or limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope of the described embodiments. The terms used in this specification have been selected to best explain the principles of the embodiments and their practical applications or technical improvements compared to the technology found in the market, or to enable other skilled in the art to understand the embodiments disclosed herein.

Claims

1. A lower layer, first encapsulated nanoparticles, each of which comprises a first magnetic nanoparticle encapsulated by a first aromatic polymer; a first polymer binder that binds the first encapsulated nanoparticles; and the lower layer including a magnetic recording layer formed over the underlying layer, second encapsulated nanoparticles each including a second magnetic nanoparticle encapsulated by an encapsulation layer; a second polymer binder that binds the second encapsulated nanoparticles; and the magnetic recording layer, Including, the underlying layer being electrically conductive to dissipate charge within the product by at least the first magnetic nanoparticles being electrically conductive; product.

2. A lower layer, first encapsulated nanoparticles, each of which comprises a first magnetic nanoparticle encapsulated by a first aromatic polymer; a first polymer binder that binds the first encapsulated nanoparticles; and the lower layer including a magnetic recording layer formed over the underlying layer, second encapsulated nanoparticles each including a second magnetic nanoparticle encapsulated by an encapsulation layer; a second polymer binder that binds the second encapsulated nanoparticles; and the magnetic recording layer, Including, The article of manufacture, wherein the first magnetic nanoparticles have an average magnetic field strength of less than 200 Oersteds (Oe).

3. A lower layer, first encapsulated nanoparticles, each of which comprises a first magnetic nanoparticle encapsulated by a first aromatic polymer; a first polymer binder that binds the first encapsulated nanoparticles; and the lower layer including a magnetic recording layer formed over the underlying layer, second encapsulated nanoparticles each including a second magnetic nanoparticle encapsulated by an encapsulation layer; a second polymer binder that binds the second encapsulated nanoparticles; and the magnetic recording layer, Including, The article of manufacture, wherein the sublayer has an onset glass transition temperature of at least 35 degrees Celsius in a plot of tensile storage modulus (E') versus temperature.

4. A lower layer, first encapsulated nanoparticles, each of which comprises a first magnetic nanoparticle encapsulated by a first aromatic polymer; a first polymer binder that binds the first encapsulated nanoparticles; and the lower layer including a magnetic recording layer formed over the underlying layer, second encapsulated nanoparticles each including a second magnetic nanoparticle encapsulated by an encapsulation layer; a second polymer binder that binds the second encapsulated nanoparticles; and the magnetic recording layer, Including, The first magnetic nanoparticles have an average diameter in the range of 2 nanometers to 15 nanometers.

5. A lower layer, first encapsulated nanoparticles, each of which comprises a first magnetic nanoparticle encapsulated by a first aromatic polymer; a first polymer binder that binds the first encapsulated nanoparticles; and the lower layer including a magnetic recording layer formed over the underlying layer, second encapsulated nanoparticles each including a second magnetic nanoparticle encapsulated by an encapsulation layer; a second polymer binder that binds the second encapsulated nanoparticles; and the magnetic recording layer, Including, The first aromatic polymer has an average thickness in the range of 1 nanometer to 8 nanometers.

6. A lower layer, first encapsulated nanoparticles, each of which comprises a first magnetic nanoparticle encapsulated by a first aromatic polymer; a first polymer binder that binds the first encapsulated nanoparticles; and the lower layer including a magnetic recording layer formed over the underlying layer, second encapsulated nanoparticles each including a second magnetic nanoparticle encapsulated by an encapsulation layer; a second polymer binder that binds the second encapsulated nanoparticles; and the magnetic recording layer, Including, The article, wherein the average thickness of said sublayer is less than 1 micron.

7. A lower layer, first encapsulated nanoparticles, each of which comprises a first magnetic nanoparticle encapsulated by a first aromatic polymer; a first polymer binder that binds the first encapsulated nanoparticles; and the lower layer including a magnetic recording layer formed over the underlying layer, second encapsulated nanoparticles each including a second magnetic nanoparticle encapsulated by an encapsulation layer; a second polymer binder that binds the second encapsulated nanoparticles; and the magnetic recording layer, Including, The second magnetic nanoparticles have an average diameter in the range of 2 nanometers to 20 nanometers.

8. A lower layer, first encapsulated nanoparticles, each of which comprises a first magnetic nanoparticle encapsulated by a first aromatic polymer; a first polymer binder that binds the first encapsulated nanoparticles; and the lower layer including a magnetic recording layer formed over the underlying layer, second encapsulated nanoparticles each including a second magnetic nanoparticle encapsulated by an encapsulation layer; a second polymer binder that binds the second encapsulated nanoparticles; and the magnetic recording layer, Including, The article, wherein each encapsulating layer has an average thickness of less than 1 nanometer.

9. A lower layer, first encapsulated nanoparticles, each of which comprises a first magnetic nanoparticle encapsulated by a first aromatic polymer; a first polymer binder that binds the first encapsulated nanoparticles; and the lower layer including a magnetic recording layer formed over the underlying layer, second encapsulated nanoparticles each including a second magnetic nanoparticle encapsulated by an encapsulation layer; a second polymer binder that binds the second encapsulated nanoparticles; and the magnetic recording layer, Including, The recording layer has an average thickness of less than 0.2 microns.

10. 10. The article of claim 1, wherein the average concentration of the first encapsulated nanoparticles in the sublayer is at least 35% by volume.

11. 10. The article of claim 1, wherein the first magnetic nanoparticles comprise chromium oxide.

12. 10. The article of claim 1, wherein the first aromatic polymer comprises a carbamate.

13. 10. The article of claim 1, wherein the first polymer binder comprises an acrylic polymer.

14. 10. The article of manufacture of claim 1, wherein the second magnetic nanoparticles comprise at least one magnetic material selected from the group consisting of nickel, cobalt, and iron.

15. The second magnetic nanoparticles are Co ３ O ４ , CoFe, Fe ３ O ４ , Fe ２ O ３ 10. The article of claim 1, further comprising at least one magnetic material selected from the group consisting of Co(fcc), Co(fcc), and Co(fcc).

16. 10. The article of claim 1, wherein the sealing layer is a layer selected from the group consisting of polyaromatic films and graphitic dominant continuous films.

17. 10. The article of claim 1, wherein the second polymer binder is an acrylic polymer.

18. 10. A product according to any one of the preceding claims, wherein the recording layer is free of wear particles.

19. 10. An article according to any one of claims 1 to 9, comprising lubricant molecules bound to a surface of the recording layer.

20. 10. The article of claim 1, wherein the sealing layer comprises a second aromatic polymer.

21. 10. An article according to any preceding claim, wherein the recording layer is substantially unmixed with the underlying layer.

22. 22. A magnetic recording tape comprising the product of any one of claims 1 to 21.

23. Housing and 23. A tape cartridge comprising: the magnetic recording tape of claim 22 at least partially contained within said housing.

24. 24. The tape cartridge of claim 23 further comprising a non-volatile memory coupled to the housing.

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