Tape media with a magnetic recording layer and a sublayer

Abstract

A product that features: a sublayer (1006) which exhibits: first encapsulated nanoparticles (1012) each comprising a first encapsulated nanoparticle encapsulated by a first aromatic polymer (1014), and a first polymeric binder (1016) that binds the first encapsulated nanoparticles (1014); and a magnetic recording layer (1008) formed above the sublayer (1006), wherein the recording layer (1008) comprises: second encapsulated nanoparticles (1020), each comprising a second encapsulated nanoparticle (1020) encapsulated by an encapsulation layer (1022), and a second polymeric binder (1024) that binds the second encapsulated nanoparticles (1020).

Description

TECHNICAL AREA

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

[0002] In magnetic storage systems, magnetic transducers read and write data from magnetic recording media. Data is written to the magnetic recording media by moving a magnetic recording transducer to a position over the media where the data is to be stored. The magnetic recording transducer then generates a magnetic field that encodes the data into the magnetic media. Data is read from the media by similarly positioning the magnetic read transducer and then sensing the magnetic field of the magnetic media. Read and write operations can be independently synchronized with the movement of the media to ensure that data can be read from and written to the desired location on the media.

[0003] A key and ongoing goal of the data storage industry is to increase the density of data stored on a medium. In tape storage systems, this goal has led to increasing the track and linear bit density on the recording tape and reducing the thickness of the magnetic tape media. However, the development of smaller-footprint, higher-performance tape drive systems has presented several challenges, ranging from the design of tape head assemblies for use in such systems to addressing the dimensional instability of the tapes.

[0004] Documents have already been published in this context. Document US 2014 / 0 340 788 A1 describes a magnetic storage medium containing magnetic nanoparticles within nanotubes. Document US 9 036 289 B2 also describes a magnetic storage medium containing magnetic nanoparticles within nanotubes. Document US 2010 / 0 015 472 A1 additionally describes encapsulated particles that are said to be no larger than 40 nm and consist, for example, of ferromagnetic or ferrimagnetic materials. Furthermore, document US 2016 / 0 027 460 A1 describes conductive polymers for use in magnetic recording media.

[0005] Despite these advances, there is still a need to increase the density of magnetic tape storage media while keeping production costs relatively simple and low. SUMMARY

[0006] This object is achieved by the subject matter of the independent patent claims. Further embodiments emerge from the respective dependent patent claims. A product according to a first approach comprises a sublayer and a magnetic recording layer formed over the sublayer. The sublayer comprises first encapsulated nanoparticles, each comprising a first encapsulated nanoparticle encapsulated by a first aromatic polymer, and a first polymeric binder binding the first encapsulated nanoparticles. The recording layer comprises second encapsulated nanoparticles, each comprising a second encapsulated nanoparticle encapsulated by an encapsulation layer, and a second polymeric binder binding the second encapsulated nanoparticles.

[0007] Numerous advantages of a magnetic recording product with the new underlayer include, but are not limited to, one or more of a thinner recording layer, a more uniform magnetic particle dispersion in the recording layer, a smoother, less intermingled transition between the underlayer and the recording layer, a higher glass transition temperature, a reduced occurrence or almost complete elimination of voids in the magnetic particles in the recording layer, etc. Each of these advantages results in a magnetic recording product, such as a tape, that exhibits properties such as, but are not limited to, one or more of improved tear resistance, higher recording resolution down to and below 1 nm, reduced noise resulting in a higher signal-to-noise ratio, etc.

[0008] In one aspect, the underlayer is electrically conductive. The electrically conductive property of the underlayer assists in the dissipation of charge, e.g., by transporting the charge to a node coupled to a ground, thereby minimizing the charge leaking into the head and, accordingly, reducing the risk of liquid condensation forming a conductive path between the tape and the head surface, creating a pathway for electrochemical corrosion of the recording head structures.

[0009] In another aspect, there are no wear particles present in the underlayer. It has been determined that such wear particles represent an increasingly unacceptable defect and a source of damage to the shrinking read and write structures in current and future recording heads.

[0010] In one aspect, the encapsulation layer comprises a second aromatic polymer. Aromatic polymers are preferred as the encapsulation layer due to the aromatic ring structure(s) that encapsulate the surface of the magnetic nanoparticle. Aromatic rings exhibit very advantageous behavior, particularly with chemically reactive metal oxides such as chromium oxide, due to the unique property of aromaticity of such molecules, which provides improved stability and, when properly aligned with the magnetic axes of the magnetic nanoparticles, a degree of magnetic shielding at the surface of the magnetic nanoparticles. The aromatic ring structures can act, for example, as a magnetic field modifier due to their unique molecular electronic structure and their ability to moderate an external magnetic field.Aromatic polymers also provide magnetic shielding at the surface of the pigment and help isolate the magnetic nanoparticles from other particles to improve the independent switching of the encapsulated nanoparticles, resulting in higher bit resolution.

[0011] In one aspect, the recording layer is substantially unmixed with the underlayer. This feature solves a long-standing problem in magnetic recording tape products, namely the intermixing of the layers at their junction and the well-known problems that such intermixing causes.

[0012] In a preferred aspect, the magnetic recording medium is a magnetic recording tape.

[0013] Further aspects and approaches of the present invention will become apparent from the following detailed description, which, when taken in conjunction with the drawings, illustrates by way of example the principles of the invention. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1A is a schematic diagram of a simplified tape drive system. Fig. 1B is a schematic diagram of a tape cartridge according to one aspect of the present invention. Fig. Figure 2A shows a side view of a flat offset, bidirectional, two-module magnetic tape head according to one aspect of the present invention. Fig. Figure 2B is a view of a belt support surface along line 2B in Fig. 2A. Fig. 2C is a detailed view of circle 2C in Fig. 2B. Fig. 2D is a detailed partial view of a belt support surface of a module pair. Fig. Figure 3 is a partial view of the tape support surface of a magnetic head having a read-write configuration. Fig. Figure 4 is a partial view of the tape support surface of a magnetic head having a read-write-read configuration. Fig. Figure 5 is a side view of a three-module magnetic tape head in which all modules are generally arranged longitudinally in approximately parallel planes. Fig. Figure 6 is a side view of a three-module magnetic tape head in a tangential (angled) configuration. Fig. Figure 7 is a side view of a magnetic tape head with three modules in a spanning configuration. The Fig. 8A-8C are schematic views illustrating the principles of band buckling. Fig. 9 is a representative diagram of files and directories stored on a magnetic tape according to one aspect of the present invention. Fig. 10 is a partial sectional view of the basic structure of a magnetic recording medium according to various approaches. Fig. Figure 11 is a graphical representation showing a dynamic mechanical analysis (DMA) of coatings to determine the critical pigment volume concentration (CPVC) according to different approaches. Fig. 12 is a TEM (transmission electron microscope) image of a cross section of a conventional recording tape. DETAILED DESCRIPTION

[0014] The following description is intended to illustrate the general principles of the present invention and is not intended to limit the inventive concepts claimed herein. Furthermore, certain features described herein may be used in any of the various possible combinations and implementations in combination with other described features.

[0015] Unless specifically stated otherwise herein, all terms shall be given their broadest possible interpretation, including meanings implied by the description as well as meanings understood by those skilled in the art and / or defined in dictionaries, contracts, etc.

[0016] It should also be noted that the singular forms “a”, “an” and “the”, “the”, “which” as used in the description and the appended claims include plural references unless otherwise indicated.

[0017] The following description discloses different configurations of layers that are particularly useful for magnetic recording media, as well as methods for forming the layers.

[0018] In one general approach, a product comprises a sublayer and a magnetic recording layer formed over the sublayer. The sublayer comprises first encapsulated nanoparticles, each comprising a first encapsulated nanoparticle encapsulated by a first aromatic polymer, and a first polymeric binder binding the first encapsulated nanoparticles. The recording layer comprises second encapsulated nanoparticles, each comprising a second encapsulated nanoparticle encapsulated by an encapsulation layer, and a second polymeric binder binding the second encapsulated nanoparticles. Example operating environment

[0019] Fig. 1A shows a simplified tape drive 100 of a tape-based data storage system that can be used in the context of the present invention. Although Fig. 1A shows a specific implementation of a tape drive, it should be noted that the approaches described here can be implemented in the context of any type of tape drive system.

[0020] As shown, a tape supply cassette 120 and a take-up reel 121 are provided for holding a tape 122. One or more of the reels may form part of a removable cassette and are not necessarily part of the tape drive 100. The tape drive, such as the one shown in Fig. 1A may further include a drive motor(s) for driving the tape supply cassette 120 and the take-up reel 121 to move the tape 122 over a tape head 126 of any type. Such a head may include an array of reading devices, writing devices, or both.

[0021] Guides 125 direct the tape 122 over the tape head 126. Such a tape head 126 is in turn coupled to a controller 128 via a cable 130. The controller 128 may be or include a processor and / or any logic for controlling any subsystem of the drive 100. The controller 128 typically controls, for example, head functions such as servo sequencing, writing data, reading data, etc. The controller 128 may include at least one servo channel and at least one data channel, each including dataflow processing logic configured to process and / or store information to be written to and / or read from the tape 122.The controller 128 may, in various approaches, operate using logic known in the art, as well as any logic disclosed herein, and thus may be considered a processor with respect to any of the descriptions of tape drives incorporated herein. The controller 128 may be coupled to a memory 136 of any known type in which instructions executable by the controller 128 may be stored. Furthermore, the controller 128 may be configured and / or programmable to execute or control some or all of the methodology presented herein. Thus, the controller 128 may be considered to be configured to perform various operations using logic programmed into one or more chips, modules, and / or blocks; software, firmware, and / or other instructions accessible to one or more processors; etc., and combinations thereof.

[0022] Cable 130 may include read / write circuitry for sending data to be recorded on tape 122 to tape head 126 and for receiving data read from tape 122 by tape head 126. An actuator 132 controls the position of tape head 126 relative to tape 122.

[0023] An interface 134 for communication between the tape drive 100 and a host (internal or external) for sending and receiving data and for controlling the operation of the tape drive 100 and for communicating the status of the tape drive 100 to the host may also be provided, as will be appreciated by those skilled in the art.

[0024] Fig. Figure 1B shows an exemplary tape cartridge 150, which, in different approaches, may include any configuration of the magnetic recording media in tape form described herein. 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 interior of the housing 152, as shown in Fig. 1B. In other approaches, the non-volatile memory 156 may be mounted inside or outside the housing 152 without modifying the housing 152. For example, the non-volatile memory may be embedded in a self-adhesive sticker 154. In a preferred approach, the non-volatile memory 156 may be solid-state memory (e.g., flash memory), a read-only memory device (ROM), etc., embedded in or coupled to the inside or outside of the tape cartridge 150. The non-volatile memory may be accessed by the tape drive and tape operating software (driver software), and / or another device.

[0025] Fig. 2A shows, by way of example, a side view of a shallow offset, bidirectional, two-module magnetic tape head 200 that can be implemented in the context of the present invention. As shown, the head comprises two bases 202, each provided with a module 204 and mounted at a small angle α with respect to one another. The bases may be "U-profiles" coupled together by adhesive. Each module 204 comprises a substrate 204A and a closure 204B, commonly referred to as a "gap," having a thin-film portion in which the reading and / or writing devices 206 are formed. In use, a tape 208 is moved along a media support surface (a tape support surface) 209 over the modules 204 for reading and writing data from and to the tape 208 using the reading and writing devices in the manner shown.The wrap angle θ of the belt 208 at the edges leading onto and off the flat media holding surfaces 209 is typically between about 0.1 degrees and about 3 degrees.

[0026] The substrates 204A are typically formed from a wear-resistant material such as ceramic. The closures 204B may be made from the same or a similar ceramic as the substrates 204A.

[0027] The readers and writers may be arranged in a piggyback or collapsible configuration. An exemplary piggyback configuration includes a (magnetically inductive) writer transducer on top of (or below) a (magnetically shielded) reader transducer (e.g., a magnetoresistive reader, etc.), with the writer poles and the reader shields generally separated. An exemplary collapsible configuration includes a reader shield in the same physical layer as a writer pole (hence "collapsed"). The readers and writers may also be arranged in an interleaved configuration. Alternatively, each array of channels may include only readers or only writers.Each of these arrangements may include one or more servo track reading devices for reading servo data on the medium.

[0028] Fig. Figure 2B shows the belt support surface 209 of one of the modules 204 along the line 2B in Fig. 2A. A representative tape 208 is shown in dashed lines. The module 204 is preferably long enough to support the tape when the head passes between data tapes.

[0029] In this example, the tape 208 has 4 to 32 data bands, e.g., as in Fig. 2B, with 16 data bands and 17 servo tracks 210 on a half-inch wide tape 208. The data bands are formed between the servo tracks 210. Each data band may have a number of data tracks, for example, 1024 data tracks (not shown). During read / write operations, the readers and / or writers 206 are positioned at specific track positions within one of the data bands. Outer readers, sometimes referred to as servo readers, read the servo tracks 210. The servo signals, in turn, are used to keep the readers and / or writers 206 aligned to a specific set of tracks during the read / write operations.

[0030] Fig. Figure 2C shows several in a gap 218 on the module 204 in the 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 of elements may vary. Example approaches include 8, 16, 32, 40, and 64 active readers and / or writers 206 per array, and alternatively, nested designs with odd numbers of readers or writers such as 17, 25, 33, etc. One example approach includes 32 readers per array and / or 32 writers per array, although the actual number of transducer elements may be greater, e.g., 33, 34, etc.This allows the tape to move more slowly, reducing speed-induced lag and mechanical difficulties, and / or requiring fewer "bulges" to fill or read the tape. Although the readers and writers may be arranged in a piggyback configuration, as shown in . Fig. 2C, the reading devices 216 and writing devices 214 may also be arranged in a nested configuration. Alternatively, each array of reading devices and / or writing devices 206 may include only reading devices or writing devices, and the arrays may include one or more servo reading devices 212. As can be seen from the synopsis of Fig. 2A and 2B-2C, each module 204 may include a complementary set of readers and / or writers 206 for things like bidirectional reading and writing, simultaneous reading and writing capacity, backward compatibility, etc.

[0031] Fig. 2D shows a partial view of the tape support surface of complementary modules of a magnetic tape head 200 according to one approach. In this approach, each module has a plurality of read / write (R / W) pairs formed on a common substrate 204A and an optional electrically insulating layer 236 in a piggyback configuration. The write devices 214 and the read devices 216 are aligned thereacross to form an R / W pair, exemplified by R / W pairs 222, parallel to an intended direction of travel of a tape medium. It should be noted that the intended direction of travel of the tape is occasionally referred to herein as the direction of travel of the tape, and such terms may be used interchangeably. Such a direction of travel of the tape may be determined from the design of the system, e.g.by checking the guides; observing the actual direction of movement of the tape relative to the reference point; etc. Furthermore, in a system capable of bidirectional reading and / or writing, the direction of movement of the tape is typically parallel in both directions, and thus both directions can be considered equivalent.

[0032] Multiple R / W pairs 222 may be provided, such as 8, 16, 32 pairs, etc. The R / W pairs 222 are, as shown, linearly aligned thereacross in a direction generally perpendicular to a direction of travel of the tape. However, the pairs may also be diagonally aligned, etc. The servo readers 212 are positioned on the outside of the array of R / W pairs, and their function is well known.

[0033] Generally, the magnetic tape media moves in either a forward or reverse direction, as shown by arrow 220. The magnetic tape media and head assembly 200 operate in a transducer relationship in a manner well known in the art. Head assembly 200 includes two thin-film modules 224 and 226 of generally identical construction.

[0034] The modules 224 and 226 are interconnected to create a single physical unit for providing the capacity of simultaneous reading and writing by activating the front module writing device and the rear module reading device aligned parallel to the direction of travel of the tape with respect thereto with the front module writing device, with a clearance between their shutters 204B (partially shown).When a module 224, 226 of a magnetic tape head 200 is manufactured, layers are created in the gap 218 created over an electrically conductive substrate 204A (partially shown) made of, for example, AlTiC, for the R / W pairs 222 in generally the following order: an insulating layer 236, a first shield 232, typically made of an iron alloy such as NiFe (-), cobalt-zirconium-tantalum (CZT) or Al-Fe-Si (Sendust), a sensor 234 for detecting a data track on a magnetic medium, a second shield 238, typically made of a nickel-iron alloy (e.g., -80 / 20 at% 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 magnetoresistance (MR), GMR, AMR, tunneling magnetoresistance (TMR), etc.

[0035] The first and second writing device poles 228, 230 may be made of high magnetic moment materials such as -45 / 55 NiFe. It should be noted that these materials are only examples, and other materials may be used. Additional layers such as insulation between the shields and / or pole ends and an insulating layer surrounding the sensor may be present. Example insulation materials include aluminum oxide and other oxides, insulating polymers, etc.

[0036] The configuration of the tape head 126 may include multiple modules, preferably three or more. In a write-read-write (WRW) head, outer modules for writing flank one or more inner modules for reading. Referring to Fig. 3, which shows a WRW configuration, the outer modules 252, 256 each have one or more arrays of writing devices 260. The inner modules 254 according to Fig. 3 have one or more arrays of reading devices 258 in a similar configuration. Variants of a multi-module head include an RWR head ( Fig. 4), an RRW head, a WWR head, etc. In further variations, one or more of the modules may include read / write pairs of transducers. Furthermore, there may be more than three modules. In other approaches, two outer modules may flank two or more inner modules, e.g., in a WRRW, an RWWR, etc. arrangement. For simplicity, a WRW head is primarily used herein to exemplify aspects of the present invention. Those skilled in the art having knowledge of the present teachings will recognize how implementations of the present invention are applicable to configurations other than a WRW configuration.

[0037] Fig. Figure 5 shows a magnetic head 126 according to one approach, which includes first, second, and third modules 302, 304, 306, each having a tape support surface 308, 310, 312, which may be flat, contoured, etc. It should be noted that although the term "tape support surface" seems to imply that the surface facing the tape 315 is in physical contact with the tape support surface, this is not necessarily the case. Rather, only a portion of the tape need be in constant or intermittent contact with the tape support surface, with other portions of the tape sliding (or "floating") on a layer of air, sometimes referred to as an "air bearing," above the tape support surface. The first module 302 is referred to as the "front" module because it is the first module encountered by the tape in a three-module design for a tape moving in the specified direction. The third module 306 is called the “rear” module.The rear module follows the middle module and is the last module the belt encounters in a three-module design. The front and rear modules 302, 306 are collectively referred to as the outer modules. It should also be noted that the outer modules 302, 306 alternate as the front module depending on the direction of travel of the belt 315.

[0038] In one approach, the band support surfaces 308, 310, 312 of the first, second and third modules 302, 304, 306 lie on approximately parallel planes (the parallel and nearly parallel planes, e.g. between parallel and tangential as in accordance with Fig. 6, and the belt support surface 310 of the second module 304 is located above the belt support surfaces 308, 312 of the first and third modules 302, 306. As described below, this has the effect of producing the desired wrap angle α2 of the belt with respect to the belt support surface 310 of the second module 304.

[0039] When the belt support surfaces 308, 310, 312 lie along parallel or nearly parallel, yet offset planes, the belt should intuitively detach from the belt support surface 308 of the front module 302. However, it has been experimentally determined that the vacuum created by a lift-off edge 318 of the front module 302 is sufficient to keep the belt adhered to the belt support surface 308 of the front module 302. A trailing edge 320 of the front module 302 (the end at which the belt leaves the front module 302) is the approximate reference point that determines the wrap angle α2 over the belt support surface 310 of the second module 304. The belt remains in close proximity to the belt support surface until close to the trailing edge 320 of the front module 302. Accordingly, converters 322 can be arranged near the rear edges of the outer modules 302, 306. These approaches are particularly designed for read-write applications.

[0040] A benefit of these and other aspects described herein is that, due to the attachment of the outer modules 302, 306 with a fixed offset to the second module 304, the inner wrap angle α2 is fixed when the modules 302, 304, 306 are coupled together or otherwise attached in a head. The inner wrap angle α2 is approximately tan -1 (δ / W), where δ is the height difference between the planes of the belt support surfaces 308, 310 and W is the width between the opposite ends of the belt support surfaces 308, 310. An exemplary inner wrap angle α2 is in a range of about 0.3° to about 1.1°, although it can be any angle required by the design.

[0041] Advantageously, the inner wrap angle α2 on the side of the module 304 receiving the belt (leading edge) is greater than the inner wrap angle α3 on the trailing edge, as the belt 315 slides over the trailing module 306. This difference is generally advantageous, as a smaller α3 tends to counteract what was previously a more acute existing effective wrap angle.

[0042] It should be noted that the belt support surfaces 308, 312 of the outer modules 302, 306 are positioned to achieve a negative wrap angle at the trailing edge 320 of the leading module 302. This is generally advantageous, provided that the position of the leverage zone formed on the belt as it separates from the head is properly considered, in that it helps reduce friction due to contact with the trailing edge 320. This negative wrap angle also reduces flutter and chafing damage to the elements on the leading module 302. Furthermore, the belt 315 on the trailing module 306 floats above the belt support surface 312, resulting in virtually no wear on the elements as the belt moves in this direction. In particular, the belt 315 entrains air and therefore does not slide significantly on the belt support surface 312 of the third module 306 (some contact may occur).This is permissible because the front module 302 is writing, whereas the rear module 306 is inactive.

[0043] 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 read devices 331 and no write devices. The first and third modules 302, 306 include multiple write devices 322 and no data read devices, except that the outer modules 302, 306 may optionally include servo read devices. The servo read devices may be used to position the head during read and / or write operations. The servo read device(s) on each module is (are) typically located toward the end of the array of read devices or write devices.

[0044] By providing only readers or page-by-page writers and servo readers in the gap between the substrate and the shutter, the gap length can be significantly reduced. Typical heads have piggyback readers and writers, with the writer positioned above each reader. A typical gap is 20–35 microns wide. However, irregularities on the tape can tend to sink into the gap and cause gap erosion. Thus, the smaller the gap, the better. The smaller gap enabled here exhibits fewer wear-related problems.

[0045] In some approaches, the second module 304 has a closure, whereas the first and third modules 302, 306 do not. Where no closure is present, a hard coating is preferably added to the module. A preferred coating is diamond-like carbon (DLC).

[0046] In the Fig. 5, the first, second, and third modules 302, 304, 306 each have a shutter 332, 334, 336 extending along the tape support surface of the associated module, effectively positioning the read / write elements away from the edge of the tape support surface. The shutter 332 on the second module 304 may be a ceramic shutter of a type typically found on tape heads. However, the shutters 334, 336 of the first and third modules 302, 306 may be shorter, measured parallel to a direction of travel of the tape across the respective module, than the shutter 332 of the second module 304. This makes it possible to arrange the modules closer together. One way to produce shorter shutters 334, 336 is to grind the standard ceramic shutters of the second module 304 down an additional size.Another method is to coat or deposit thin-film sealants over the elements during thin-film processing. For example, a thin-film seal made of a hard material such as Sendust or a nickel-iron alloy (e.g., 45 / 55) can be created on the module.

[0047] With reduced-strength ceramic or thin-film shutters 334, 336, or no shutters on the outer modules 302, 306, the distance from the write to read gap can be reduced to less than about 1 mm, e.g., to about 0.75 mm, or 50% less than the spacing typically used in an open tape head for linear tapes (LTO). The open clearance between the modules 302, 304, 306 can still be adjusted to approximately 0.5 to 0.6 mm, which is ideal for stabilizing tape movement across the second module 304 in some approaches.

[0048] Depending on the belt tension and strength, it may be desirable to angle the belt support surfaces of the outer modules with respect to the belt support surface of the second module. Fig. 6 shows a device in which the modules 302, 304, 306 have a tangential or near-tangential (angled) configuration. In particular, the belt support surfaces of the outer modules 302, 306 are approximately parallel to the belt at the desired wrap angle α2 on the second module 304. In other words, the planes of the belt support surfaces 308, 312 of the outer modules 302, 306 are aligned approximately at the desired wrap angle α2 of the belt 315 with respect to the second module 304. The belt also jumps off the rear module 306 in this approach, thereby reducing wear on the elements in the rear module 306. These approaches are particularly useful for read-write applications. Additional aspects of these approaches are similar to those listed above.

[0049] Typically, the belt wrap angles can be approximately midway between the Fig. 5 and Fig. 6 approaches shown.

[0050] Fig. Figure 7 shows a device in which the modules 302, 304, 306 are in a wrap-around configuration. In particular, the tape support surfaces 308, 312 of the outer modules 302, 306 are angled slightly more than the tape 315 when adjusted to the desired wrap angle α2 with respect to the second module 304. With this approach, the tape does not jump from the rear module, enabling its use for writing or reading. Accordingly, both the front and middle modules can perform read and / or write functions, while the rear module can read any data being written. Thus, these approaches are preferred for read-write-write, read-write-read, and write-write-read applications. In the latter approaches, the shutters should be wider than the tape surfaces to ensure read capacity. The wider shutters may require a wider gap-to-gap spacing.Therefore, a preferred approach has a read-write configuration where shortened shutters can be used, thus allowing shorter gap-to-gap distances.

[0051] Additional aspects of the Fig. 6 and Fig. The approaches shown in Figure 7 are similar to those listed above.

[0052] A 32-channel version of a multi-module tape head 126 can use cables 350 with conductors spaced at the same or smaller distances as current 16-channel piggyback LTO modules, or alternatively, the connections on the module can be organically configured for a 50% reduction in cable span. Overhead / underhead unshielded write pair cables can be used for the write devices, which may have integrated servo read devices.

[0053] The outer wrap angles α1 can be adjusted in the drive, for example, by guides of any type known in the art, such as adjustable rollers, slide rails, etc., or alternatively by cantilevers formed integrally with the head. For example, rollers with an offset axis can be used to adjust the wrap angles. The offset axis creates a rotational arc that allows for precise adjustment of the wrap angle α1.

[0054] A conventional U-channel assembly may be used to assemble any of the approaches described above. Accordingly, with respect to heads of previous generations, the mass of the resulting head may be maintained or even reduced. In other approaches, the module may be constructed as a single-piece body. Those skilled in the art having knowledge of the present teachings will appreciate that other known methods of manufacturing such heads may be adapted for use in constructing such heads. Furthermore, unless otherwise indicated, processes and materials of types known in the art may be adapted for use in different approaches in accordance with the present teachings, as will become apparent to those skilled in the art upon reading the present disclosure.

[0055] When a tape is passed over a module, it is preferable that the tape is passed sufficiently close to magnetic transducers on the module so that reading and / or writing is carried out efficiently, e.g., with a low error rate. According to some approaches, tape buckling can be used to ensure that the tape is passed sufficiently close to the section of the module with the magnetic transducers. To better understand this process, the Fig. 8A - 8C the principles of band bulging. Fig. Figure 8A shows a module 800 with an upper belt support surface 802 extending between opposing edges 804, 806. A stationary belt 808 is shown wrapped around the edges 804, 806. As shown, the flexural rigidity of the belt 808 lifts the belt from the belt support surface 802. Belt tension tends to flatten the belt profile, as shown in Fig. 8A. When the band tension is minimal, the band's curvature is more parabolic than shown.

[0056] Fig. 8B shows the belt 808 in motion. The leading edge, i.e., the first edge encountered by the belt as it moves, can serve to deflect air from the belt, thereby creating a sub-ambient air pressure between the belt 808 and the belt support surface 802. In Fig. In Figure 8B, the leading edge is the left edge, and the right edge is the trailing edge as the belt moves from left to right. As a result, the ambient pressure above the belt pushes the belt toward the belt support surface 802, creating a belt bulge near each edge. The flexural stiffness of the belt resists the effect of the ambient pressure, causing the belt bulge near both the leading and trailing edges. Modeling predicts that the two bulges have very similar shapes.

[0057] Fig. Figure 8C shows how the sub-ambient pressure pulls the belt 808 toward the belt support surface 802 even when a rear guide 810 is disposed above the plane of the belt support surface.

[0058] It follows that tape camber can be used to steer the trajectory of a tape as it passes over a module. As previously stated, tape camber can be used to ensure that the tape passes sufficiently close to the section of the module containing the magnetic transducers, preferably so that reading and / or writing is performed efficiently, e.g., with a low error rate.

[0059] Magnetic tapes may be stored in tape cartridges, which in turn are stored in storage slots or the like in a data storage library. The tape cartridges may be stored in the library so that they are accessible for physical retrieval. In addition to magnetic tapes and tape cartridges, data storage libraries may include data storage drives that store data on and / or retrieve data from the magnetic tapes. Furthermore, tape libraries and the components they comprise may implement a file system that provides access to a tape and data stored on the tape.

[0060] File systems can be used to control how data is stored in and retrieved from storage. Thus, a file system might include the processes and data structures an operating system uses to keep track of files in storage, such as the way the files are organized in the storage. A linear tape file system (LTFS) is an example file system format that might be implemented to provide access to compatible tapes in a given library. It should be appreciated that different aspects described here can be implemented using a wide variety of file system formats, including, for example, IBM Spectrum Archive Library Edition (LTFS LE).However, to provide context and solely as a convenience to the reader, some of the approaches below may be described with reference to LTFS, which is one type of file system format. This is provided merely by way of example and should not be construed as limiting the invention defined in the claims.

[0061] A tape cartridge can be "loaded" by inserting the cartridge into the tape drive, and the tape cartridge can be "removed" by removing the tape cartridge from the tape drive. Once loaded into a tape drive, the tape in the cartridge can be "threaded" through the drive by physically pulling the tape (the magnetic recording portion) out of the tape cartridge and passing it over a magnetic head of a tape drive. Furthermore, the tape can be wound on a take-up reel (see, for example, 121 in the above Fig. 1A) to move the tape over the magnetic head.

[0062] Once threaded into the tape drive, the tape can be "installed" in the cartridge by reading metadata from the tape and putting the tape into a state where LTFS can use the tape as part of a file system. Furthermore, to "uninstall" a tape, metadata (e.g., as a directory) is preferably first written to the tape, after which the tape can be removed from the state where LTFS can use the tape as part of a file system. Finally, to "unthread" the tape, the tape is removed from the take-up reel and physically inserted back into the interior of a tape cartridge. The cartridge can remain loaded into the tape drive even after the tape has been unthreaded, for example, to wait for another read and / or write request. In other cases, however, the tape cartridge can wait for the tape to be unthreaded, such asdescribed above, from the tape drive.

[0063] Magnetic tape is a sequential-access medium. Therefore, new data is written to the tape by appending it to the end of previously written data. Consequently, when data is recorded on a single-segment tape, metadata (e.g., mapping information) is continuously appended to one end of the previously written data because it is frequently updated and rewritten to the tape accordingly. This results in the last-most information being read to access the most recent copy of the metadata corresponding to the tape when a tape is initially mounted. However, this introduces a significant amount of delay into the process of mounting a given tape.

[0064] To address this delay caused by single-partition tape media, the LTFS format features a tape divided into two partitions, including a directory partition and a data partition. The directory partition can be designed to record metadata (metainformation), such as file allocation information (a directory), whereas the data partition can be designed to record the existence of the data, such as the data itself.

[0065] Becomes Fig. Referring to Figure 9, a magnetic tape 900 is shown having a directory partition 902 and a data partition 904 according to one approach. As shown, data files and directories are stored on the tape. The LTFS format allows directory information to be recorded in directory partition 902 at the beginning of tape 906, as will be apparent to those skilled in the art upon reading this specification.

[0066] When the directory information is updated, the previous version of the directory information is preferably overwritten, which allows the currently updated directory information to be accessible at the beginning of the volume in the directory partition. According to the Fig. In the specific example shown in Figure 9, a latest version of metadata Directory 3 is recorded in directory division 902 at the beginning of tape 906. In contrast, all three versions of metadata Directory 1, Directory 2, Directory 3, and data File A, File B, File C, and File D are recorded in data division 904 of the tape. Although Directory 1 and Directory 2 are old (e.g., obsolete) directories, these old directories Directory 1, Directory 2 remain stored in data division 904 on tape 900 without being overwritten because information is written to the tape by appending it to the end of previously written data, as described above.

[0067] The metadata may be updated in the directory partition 902 and / or the data partition 904 in the same way or differently, depending on the desired approach. According to some approaches, the metadata in the directory and / or data partition 902, 904 may be updated in response to the uninstallation of the tape, e.g., so that the directory can be quickly read from the directory partition when that tape is remounted. The metadata is preferably also written to the data partition 904 so that the tape can be mounted using the metadata recorded in the data partition 904, e.g., as a backup option.

[0068] As an example, which is not intended to limit the invention in any way, LTFS LE can be used to provide the functionality of writing a directory to the data partition when a user explicitly instructs the system to do so, or at a time determined by a predetermined time period that can be set by the user, e.g., to mitigate data loss in the event of a sudden power failure. Magnetic recording media and their layer manufacturing

[0069] Fig. 10 shows a partial, not-to-scale, cross-sectional view of the basic structure of a magnetic recording medium 1000 according to various approaches described herein. Optionally, the present magnetic recording medium 1000 may be implemented in conjunction with features of any other approach presented herein, such as those described with reference to the other figures. It should be understood, however, that such a magnetic recording medium 1000 and others presented herein may be used for different applications and / or in implementations that may or may not be specifically described in the exemplary approaches presented herein. Furthermore, the present magnetic recording medium 1000 may be used in any desired environment.The magnetic recording medium 1000 has been developed in various implementations disclosed herein to improve the stability and performance of tape storage media across the required usage and storage environments.

[0070] Unless otherwise described herein, the various layers of the magnetic recording medium 1000 may have a conventional construction, design, and / or function. In various approaches, a new and novel layer may be used with conventional layers. In other approaches, multiple new and novel layers may be used together with other conventional layers.

[0071] Unless otherwise described herein, the various layers of the magnetic recording medium 1000 may be formed using conventional techniques, particularly if the respective layer is of conventional construction.

[0072] The magnetic recording medium 1000 is preferably a magnetic recording tape, but in other aspects it is another type of deformable media.

[0073] As in Fig. 10, four base layers are present in the magnetic recording medium 1000. An optional backcoat 1002 is disposed along one side (the lower side in the figure) of a substrate 1004. An underlayer 1006 is disposed along another side (the upper side in the figure) of the substrate 1004. A recording layer 1008 is disposed over the underlayer 1006. In different approaches, additional layers of conventional construction may be present in the magnetic recording medium 1000. For example, the backcoat may be omitted, and multiple layers may be applied to both sides of the substrate to enable recording on both sides of the finished tape. Back coating

[0074] The backcoat 1002 may, but need not, be present in the magnetic recording medium 1000. The backcoat 1002 may be of conventional construction, design, and function, and in some approaches, may have a conventional composition comprising a conductive carbon black dispersed in a polymer binder system, as has been common practice in the industry for decades, although again, 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: facilitating separation from another portion of the tape wound on a spool thereabove, improving tribology, dissipating static electricity, etc. A preferred thickness of the backcoat 1002 is less than about 0.3 microns, more preferably less than about 0.2 microns. Substrat

[0075] The substrate 1004 is preferably of conventional construction, design, and function. The substrate 1004 is typically the strongest layer. Example materials for the substrate 1004 include polyethylene terephthalate (polyester or PET), polyethylene naphthalate (PEN), super-tensile PEN, an aramid-type material (e.g., solubilized para-imide such as one sold under the trade name Mictron™, which is sold by Toray Industries, Inc., with a business location at Nihonbashi Mitsui Tower, 1-1, Nihonbashi-Muromachi, 2-Chrome, Chuo-Ku, Tokyo 103-8666, Japan), etc. lower class

[0076] The underlayer 1006 performs one or more of the following functions in the structure: attenuation of the magnetic signal conducted through the recording layer, adhesion of the recording layer to the substrate 1004, etc. Accordingly, in most approaches described herein, the function of the underlayer 1006 is not to hold a storage of the flux of the writing device, but rather to enhance the write flux field from the write head element when writing to the recording layer 1008. Moreover, any held magnetic moment alignment from writing is preferably weak or nonexistent to minimize noise during readback.

[0077] According to various approaches, a very important attribute of the populated magnetic coating in the underlayer is the rapid absorption of the stray field passing through the above recording layer during the very fast magnetic switching that occurs during writing. The ideal underlayer should have a very low residual moment (M r ) so that it does not maintain alignment after the writing field has passed through this volume of the underlayer.

[0078] In some approaches, the underlayer 1006 has a new and novel structure. In one aspect, the new and novel underlayer 1006 may be present in the medium 1000 with a conventional recording layer 1008 thereover. In another aspect, the new and novel underlayer 1006 may be present in the medium 1000 with a new and novel recording layer 1008 thereover. In further approaches, the underlayer 1006 has a conventional structure and is present in the medium 1000 with a new and novel recording layer 1008 thereover.

[0079] In various approaches, the underlayer 1006 has one or more of the following properties, and preferably all of the following properties: electrically conductive, slightly magnetic (a total magnetic strength in Oersteds (Oe) that is less than 200 Oe and preferably less than 100 Oe). Ideally, to improve the transition to the recording layer 1008, the underlayer is deposited and calendered thereon prior to the formation of the recording layer 1008, as described in more detail below. In a preferred embodiment, the underlayer 1006 has about one-tenth the coercivity of the recording layer 1008 (in Oersteds) and a low residual magnetization, thereby enabling the underlayer 1006 to act as a magnetic field flux absorber without creating signal interference with the overlying recording layer 1008.

[0080] The electrical conductivity property serves to reduce corrosion of magnetic heads operating on a tape. In particular, during tape unwinding, the separation of the recording layer generates a triboelectric potential and current, which can trigger a static discharge in a dry environment and create an electrochemical pathway for head corrosion in a humid environment. These situations are both undesirable in terms of tape performance and durability, and both are believed to be a significant factor in head corrosion. The electrical conductivity property of the underlayer 1006 helps dissipate the charge, e.g.by transporting the charge to a node coupled to a ground, thereby minimizing the charge leaking into the head and correspondingly reducing the risk of liquid condensation forming a conductive path between the tape and the head surface, creating a pathway for electrochemical corrosion of the recording head structures.

[0081] The weak magnetic property reduces the amount of noise contributed by the magnetic fields emanating from the underlayer 1006 and improves the resolution of the written bits in the recording layer above the underlayer.

[0082] In approaches where the underlayer 1006 has a conventional construction, typically utilizing micron-sized particles with low coercivity and low moment, the coating is not optimized for a high loading of very small (nanoscale) particles. The underlayer, in some approaches, is fabricated with a weakly magnetic iron oxide using a conventional rubbery polyester polyurethane resin with a poly(vinyl acetate-vinyl alcohol-vinyl chloride) resin cured with a poly(isocyanate), as used in previous tape product formats. However, such conventional coatings were not specifically designed or developed as an optimal underlayer for the overlying signal recording layer in the finished tape.

[0083] In preferred approaches, the underlayer 1006 has a novel formula in which the underlayer 1006 comprises particles 1010 that are weakly magnetic but also electrically conductive and dispersed in a low-strain UV-cured matrix that ensures good adhesion to the substrate and provides mechanical stability and strain relief for the overlying, very thin recording layer.

[0084] The underlayer 1006 does not need to have a narrow distribution of nanoparticle sizes in different approaches, although the use of small particles improves the surface roughness offered to the recording layer during deposition of the recording layer. Using the novel manufacturing processes described here, the underlayer 1006 is not attacked (swelled by the recording layer during deposition of the recording layer thereon).

[0085] In preferred approaches, the sublayer 1006 has a novel composition in which the sublayer 1006 contains encapsulated nanoparticles 1010, each comprising at least one magnetic nanoparticle 1012, and preferably only one magnetic nanoparticle 1012, encapsulated by an aromatic polymer 1014. A polymeric binder 1016 binds the encapsulated nanoparticles in the sublayer 1006.

[0086] An average concentration of the encapsulated nanoparticles in the sublayer 1006 is preferably at least about 35 vol%, e.g., 40 vol%, 45 vol%, 50 vol%, 55 vol%, 60 vol%, more than about 60 vol%, in a range of about 40-75 vol%, in a range of about 45-75 vol%, in a range of about 50-75 vol%, in a range of about 35-50 vol%, in a range of about 40-60 vol%, or any other subrange within the aforementioned ranges. Ideally, the average concentration of the encapsulated nanoparticles does not exceed the critical pigment volume concentration (CPVC), at which the coating would lose its mechanical integrity and no longer function as a usable, long-lasting coating.For coatings containing nanoparticles, a very high surface area can dramatically reduce the CPVC unless a novel nanoparticle encapsulation and binder design is implemented that allows for higher CPVC. The CPVC can be determined using dynamic mechanical analysis (DMA) of free films of the coating on a series of coatings with increasing vol% of filler. For the novel compositions described here, conventional DMA techniques can be used. The CPVC is determined at the vol% at which the tensile storage modulus (E') reaches its maximum value. Fig. Figure 11 shows a CPVC DMA plot 1100 for varying vol% pigment in an underlayer according to various approaches. Such a plot 1100 is exemplary of a plot(s) that can be created by those skilled in the art following the present teachings and using conventional DMA plotting techniques without resorting to undue experimentation.

[0087] The magnetic nanoparticles preferably comprise a weakly ferrimagnetic material. “Weakly ferrimagnetic” means that the magnetic nanoparticles do not have a high coercivity (H c ) or no high magnetic moment (M r), but rather have a moderate magnetic field strength that contributes a minimal signal when reading the overlying recording layer. Ideally, the final coating will exhibit no detectable noise signal contribution to the observed response of the written bits in the data storage layer.

[0088] In preferred approaches, the magnetic nanoparticles have a coercivity (H c ) of less than about 200 Oe, more preferably less than 100 Oe and more than 50 Oe. An exemplary field strength range of the magnetic nanoparticles is 50-200 Oe. The magnetic nanoparticles are preferably also characterized by a low residual moment, e.g., <12 emu / g.

[0089] A preferred material for the magnetic nanoparticles is chromium dioxide, which is weakly magnetic, electrically conductive, and very hard. In other approaches, the magnetic nanoparticles comprise one or more magnetic metal particles with an oxidized outer surface or (at the expense of conductivity) oxide such as cobalt, nickel, or iron, and alloys thereof.

[0090] Depending on the material, the mean diameter of the magnetic nanoparticles is preferably in a range of 2 nanometers (nm) to 20 nm, more preferably 4 nm to 10 nm, although in some approaches the mean diameter could be larger or smaller than this range. One consideration regarding the mean diameter is that the smaller the size, the more difficult it may be for the binder to properly hold the pigments in the coating matrix. Accordingly, the mean diameter of the magnetic nanoparticles should be chosen to keep the critical pigment volume within an acceptable range. If the mean diameter is too small, insufficient binder may be present between adjacent particles, making the material brittle and prone to breakage.If the particles are too large, the transition between the underlayer 1006 and the recording layer 1008 loses the desired smoothness property described here.

[0091] In preferred approaches, the magnetic nanoparticles present in the underlayer are weakly magnetic and electrically conductive and are composed to produce a dried coating with negligible or no swelling due to the solvent used to apply the recording layer. The use of nanoparticles in the underlayer is preferred over the use of larger particles to enable a smoother transition to the recording layer.

[0092] The encapsulated nanoparticles can have a broad size distribution in various preferred implementations as long as the resulting dried film does not exceed the critical pigment volume concentration.

[0093] Preferably, the majority of the particles in the underlayer 1006 are coated with sufficient binder to achieve a coherent and stable coating with a minimal number of coated clumps of particles or aggregates. The ideal coating would exhibit no clumps or aggregates in the final coating, so that nearly 100% of the particles are fully dispersed as individual particles in the binder matrix. Good dispersion of the particles in the matrix with minimal particle alignment further reduces the contribution of the underlayer noise to the signal recorded in the recording layer.

[0094] Likewise, the encapsulated nanoparticles are preferably not well aligned with each other, but are, for example, randomly aligned in the sublayer 1006. This further improves the performance of the sublayer by reducing the formation of ordered magnetic domains in the sublayer 1006, thereby reducing the noise generated in the sublayer 1006. Nevertheless, while it is desirable to create a monodisperse, non-aggregated dispersion of encapsulated particles for the coating composition, it is not required for the sublayer because mechanical properties are more important than magnetic signal performance.

[0095] The aromatic polymer encapsulating the magnetic nanoparticles may be and / or comprise any of a wide variety of aromatic polymers, as long as the aromatic polymer encapsulates at least about 80% of the surface area of ​​the magnetic nanoparticle, preferably at least about 90% of the surface area of ​​the magnetic nanoparticle, and ideally approximately 100% of the magnetic nanoparticle in the sublayer 1006. Accordingly, the aromatic polymer forms at least a partial shell and preferably a complete shell around the magnetic nanoparticles.

[0096] The layer encapsulating the nanoparticles can be as thin as a monolayer, for example, less than 0.4 nm, but a more robust layer is achieved at a thickness of approximately 1-2 nm. As the layer becomes thicker, the packing of the nanoparticles in the coating decreases. This is not as critical in the sublayer as it is in the recording layer.

[0097] The average thickness of the aromatic polymer encapsulating the magnetic nanoparticles is preferably in a 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 could be slightly higher or lower than these ranges. The thicknesses used herein generally refer to the deposition thickness on the underlying structure, unless otherwise stated.

[0098] Aromatic polymers are preferred as encapsulation layers due to the aromatic ring structure(s) that encapsulate the surface of the magnetic nanoparticle. Aromatic rings exhibit highly advantageous behavior, particularly with chemically reactive metal oxides such as chromium oxide, due to the unique property of aromaticity of such molecules, which provides improved stability and, when properly aligned with the magnetic axes of the magnetic nanoparticles, a degree of magnetic shielding at the surface of the magnetic nanoparticles. The aromatic ring structures can act, for example, as magnetic field modifiers due to their unique molecular electronic structure and their ability to moderate an external magnetic field.

[0099] Aromatic polymers also provide magnetic shielding at the surface of the pigment and help isolate the magnetic nanoparticles from other particles to improve the independent switching of the encapsulated nanoparticles, resulting in higher bit resolution.

[0100] A preferred aromatic polymer is a carbamate. A preferred 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 densely packed matrix is ​​methylenebisdiphenylcarbamate. Ideally, when used with chromium dioxide nanoparticles, the encapsulating polymer is formed from methylenebisdiphenylcarbamate with a functional acrylic polyester as the ester segment of the aromatic carbamate. Upon UV irradiation, polymerization can occur to create the encapsulating polymer film layer on the surface of the particle.

[0101] Particularly for use with magnetic chromium dioxide nanoparticles, the aromatic polymer is preferably an aliphatically substituted aromatic compound, for example, containing an oxidizable moiety that reacts with chromium, thereby aiding in the adsorption of the aromatic polymer onto the chromium dioxide microparticle. The benzylic carbon of diphenylmethane dicarbamate is known to be efficiently oxidized by chromium dioxide, effectively binding the resulting diphenyl ketone to the particle surface.

[0102] In other approaches, the aromatic polymer contains reactive functional substituents such as amines, alcohols, carboxylic acids, or nitrile groups. One example is cinnamic acid, which is present as a copolymer with styrene to form a bound polymer layer on the nanoparticle surface.

[0103] In further approaches, the aromatic polymer comprises one or more repeating units with substituents suitable for chemical adsorption and / or binding to the particle surface, such as amines, a carboxylic acid such as cinnamic acid, and other functional aromatics that bind to the surface of the magnetic nanoparticle used.

[0104] In an alternative implementation, the encapsulation layer of the encapsulated microparticles is not made of a fully aromatic polymer, but can be a copolymer such as a polyester polyurethane or acrylic-modified polyurethane. Examples include aliphatic polymers of a known type, non-aromatic polymers of a known type, etc.

[0105] The polymeric binder that binds the encapsulated nanoparticles together can be and / or comprise binder materials of various types. In preferred approaches, the binder comprises an acrylic polymer, e.g., a polymer of acrylic acid or an acrylate, and preferably a functional acrylic polymer. Exemplary acrylic polymers suitable for use as binders in various approaches include components such as methyl methacrylate, acrylic acid, and others. Generally, preferred polymeric binders are those having a number-average molecular weight of less than about 2400, and preferably less than about 1200.

[0106] In a preferred implementation, the polymeric binder has UV-curability functionality to enable bonding to the encapsulating layer of the encapsulated microparticles. This functionality can be provided by acrylate groups, vinyl, etc.

[0107] In some approaches, the binder contains vinyl chloride or vinyl acetate-vinyl alcohol copolymers. In other approaches, the binder contains polyester or polyether polyurethanes. In the nanoparticle-coated coatings, the polymers have a much lower molecular weight (much smaller size) than the materials used previously. Typically, the usable polymers have a length of fewer than 20 repeat units before UV curing.

[0108] The relative amounts of encapsulated nanoparticles to binder in the sublayer 1006 should be in a range not exceeding the critical pigment volume concentration (CPVC). Those skilled in the art, once familiar with the novel compositions described herein, could calculate the CPVC using known techniques based on the properties of the materials used, such as the binder used, the particle surface area, etc. A general rule of thumb is to use less than about 50 vol% pigment (encapsulated nanoparticles) in the sublayer 1006 to maintain the structural integrity of the sublayer 1006, along with other functions of the sublayer 1006 such as structural stabilization of the magnetic layer, improving tape durability, and ensuring adhesion of the recording layer 1008.The pigment content is preferably high enough to ensure adequate mechanical integrity as measured by DMA while maintaining sufficient electrical conductivity to reduce undesirable triboelectric properties.

[0109] Additional materials such as mobile lubricants and / or stabilizers used to stabilize the dispersion prior to application and curing may be present in the underlayer 1006.

[0110] The resulting underlayer 1006 is preferably characterized by a weakly magnetic, electrically conductive, encapsulated nanoparticle dispersion in a binder tightly bound to the pigment (to the encapsulated nanoparticles) to achieve a graphical representation of a dried coating with a glass transition onset temperature Tg in the tensile storage modulus (E') with respect to temperature from 0° Celsius (C) to 60°C. Tg should be higher than 35°C, preferably above about 45°C, and an absolute value of E' measured at 10 Hz by DMA at 20°C should be at least about 6 gigapascals (GPa) to about 16 GPa, or slightly more, e.g., about 8 GPa, about 10 GPa, about 11 GPa, 12 GPa, about 15 GPa, about 16 GPa. The normal operating range of a belt for most approaches is in the range of 0°C to 60°C, but can be higher or lower.

[0111] Binders used in conventional magnetic recording tapes result in an underlayer 1006 with a glass transition temperature of 20-30°C. This is too soft, resulting in the underlayer 1006 being too compliant in use to ensure a stable and durable recording medium. However, the underlayer 1006 should be sufficiently elastic to remain durable and long-lasting during use and storage. Accordingly, preferred embodiments result in an underlayer 1006 having an initial Tg determined by a graphical DMA plot of E' with respect to temperatures above about 35°C, with the preferred initial Tg remaining in the elastic range with a very broad response at 10 Hz to at least 50°C.

[0112] An average thickness of the backsheet 1006 is less than 1 micron, and preferably less than about 0.6 microns. To allow more tape to be wound into the fixed volume of a given tape cartridge, lower thicknesses are preferred.

[0113] In preferred approaches, no wear particles are present in the underlayer 1006, and ideally, no wear particles are present in the product at all. Wear particles, conventionally added for the purpose of cleaning the tape head and / or reducing stiction, have been found to be an increasingly unacceptable deficiency and a source of damage to the shrinking read and write structures in current and future recording heads. However, in further approaches, wear particles may be present in the underlayer 1006.

[0114] To minimize intermixing of the layers, the underlayer 1006 is preferably at least partially dried and cured prior to the application of the magnetic recording layer 1008 to the substrate 1004. Accordingly, in preferred approaches, the recording layer 1008 is substantially non-intermixed with the underlayer 1006 (and vice versa). This feature solves a long-standing problem in magnetic recording tape products.

[0115] Referring to Fig. Figure 12 shows a TEM image of a cross-section of a conventional recording tape 1200. As shown, the transition between the recording layer and the underlying underlayer is clearly defined. The bright particles in the recording layer are barium ferrite particles. As shown, the barium ferrite particles in the recording layer are neither monodisperse nor densely packed. Furthermore, there are gaps where no particles are located. Furthermore, the transition from the recording layer to the underlayer is relatively rough. Ideally, magnetic fields from a writing device pass through the recording layer completely perpendicularly. Unfortunately, magnetic fields expand or bend upon leaving the writing device, with the bend becoming more pronounced the farther from the pole end of the writing device.The gaps, the wavy transition between the recording layer and the underlayer, and the uneven dispersion of the magnetic particles all amplify the effects of the expanding field of the writing device. Where a transition is being written (e.g., writing field directed downwards, then upwards as the tape moves past the writing device), and the field expands by, say, 10-20% as it passes the recording layer, the transition is not sharp, reducing the tape's resolution. When read back, the transition is noisy because it is not sharp. A 1 dB improvement in the signal-to-noise ratio (SNR) during readback is a significant achievement.The inventor believes that an improvement in the readback signal-to-noise ratio (SNR) of up to 5 or 6 dB can be achieved using the new and novel recording layer described herein, which is formed on a cured underlayer, thereby minimizing intermixing of the layers.

[0116] In preferred approaches, the upper surface of the underlayer is substantially flat with a modulation of less than about 25%, preferably less than about 5% of the thickness of the transition boundary when imaged in the TEM cross-section of the finished coil coating, such as the upper surface of the Fig. 12 shown recording layer. Process for manufacturing the base layer

[0117] A method for manufacturing the underlayer 1006, for example, of a magnetic recording medium according to various approaches is presented below. As an option, the present method can be implemented for creating sublayers 1006 such as those described above. Of course, however, this and other methods presented here can be used for creating sublayers 1006 that may or may not be related to the exemplary aspects listed here. Furthermore, the methods presented here can be carried out in any desired environment. Furthermore, according to different approaches, more or fewer operations than those described below can be included in the method. It should also be noted that each of the features listed above can be used in any of the approaches described according to the different methods.

[0118] The method generally comprises forming a sublayer 1006 containing encapsulated nanoparticles, each comprising at least one magnetic nanoparticle encapsulated by an aromatic polymer, and a polymeric binder that binds the encapsulated nanoparticles.

[0119] Encapsulated nanoparticles can be purchased or manufactured. For example, some approaches utilize commercially available encapsulated nanoparticles suitable for medical imaging and drug delivery applications.

[0120] In one approach, creating the sublayer 1006 involves mixing the polymeric binder with the encapsulated nanoparticles and a solvent (a solvent system) to create a mixture. The relative amounts of encapsulated nanoparticles and binder are preferably selected to ensure the properties listed in the previous section. For example, the mixing includes ultrasonically dispersing the encapsulated nanoparticles in the polymeric binder and the solvent, thereby creating a radiation-curable emulsion in the solvent.

[0121] Conventional coating processes would require a composition to achieve a usable viscosity and likely binders with a significantly higher molecular weight than would be optimal for the target design of the present advanced tape construction. Therefore, the examples described here are examples of compositions that are not suitable for conventional coating. All of the examples are best applied to the substrate as a sprayed aerosol coating, although other coating methods are contemplated.

[0122] In general, the solvent used here should offer one or more, and preferably all, of the following properties: the solvent causes the polymeric binder to swell, but allows the polymers around the pigment to collapse rather than shrink upon drying. The solvent causes the polymeric binder chain to uncoil and move to its theta state (minimal free volume).

[0123] The layer is most stable when the polymer binder is in the theta state, and this is where curing should occur. UV curing is preferred when the polymer binder is close to its theta state due to the speed at which curing occurs.

[0124] One of the solvent components should be a good solvent for the binder additive and helps suspend the polymer-encapsulated magnetic particles. The second solvent can be a non-solvent for the polymer binder. As the 'good' solvent phase evaporates, the remaining coating moves closer to a non-solvent-dominated coalescing coating. The second solvent-rich coating thus passes through a point in the drying process where the binder and the encapsulated magnetic particles are at approximately their minimum free volume, or theta states. This creates minimal residual stress in the finished, dried coating. This, in turn, eliminates curling and rippling in the finished tape.

[0125] A preferred solvent is a water and tetrahydrofuran (THF) solvent system in relative concentrations that make the solvent system nearly completely azeotropic. This solvent system is preferred for use with acrylic polymer binders because it dries well, is environmentally friendly, consumes less energy, and is less prone to combustion or explosion than an azeotrope. The THF / water solvent is also preferred because the THF disappears first during drying, followed by the water, which helps maintain the binder toward the theta state. In particular, the THF disappears first due to its higher volatility than water. Having the organic solvent disappear first allows for the film's coalescence to collapse and the stress to decrease. The water then dominates the solvent transition, allowing the polymer to approach theta states.

[0126] Only a slight increase in the water content compared to the azeotropic mixture concentrations (e.g., 6.7 mass percent) is required to ensure optimal drying of the coating. This results in a solvent mixture in the range of 7-8% water in 92-93% THF, which dries at 64°C. This lower drying temperature has the additional benefit of reducing operating costs compared to current magnetic tape coating processes.

[0127] The resulting mixture (pigment + solvent) is applied to a structure such as substrate 1004. Any suitable technique can be used to apply the mixture. If the pigment and solvent mixture forms an emulsion, a preferred technique is spray coating, which ensures 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, the use of gravure rollers, etc.

[0128] In another approach, the formation of the sublayer 1006 includes mixing the polymeric binder with the encapsulated nanoparticles to create a microsuspension without the addition of dispersants or other additives to create a stable dispersion.

[0129] The applied mixture is dried to remove at least a portion of the solvent, or is dried substantially completely. For example, the applied mixture may be dried to remove the more volatile organic solvent (e.g., THF), thereby increasing the non-solvent content in the drying film. The polymeric binder collapses between the encapsulated microparticles as the solvent is removed during drying. In one aspect where the binder is hydrophobic, the last solvent to disappear from the applied mixture, such as water, is not a solvent for the binder, thereby forcing collapse of the hydrophobic binder onto the pigments. This also minimizes residual stress in the dry coating, preventing things like ribbon curling.Drying is preferably carried out using compressed air under low temperature conditions (less than about 75 °C).

[0130] The partially dried coating, which ultimately forms the underlayer for the magnetic recording layer, can be cured using, for example, a thermally induced chemical reaction to cure the two layers, a radiation-induced chemical reaction to cure the two layers, etc. For example, UV light or other known irradiation is used to cause crosslinking of the polymeric binder. If the correct solvent selection is made for both coatings, the curing step results in minimal stress between the two layers and a stable (flat) coating.

[0131] In the case of thermally induced curing, a chemical reaction can be used to reduce solvent swelling in the coating and improve the mechanical properties of the cured coating. Chemical curing in a dry film is slow and inefficient for achieving the desired uniformity of a cured, highly populated coating. The preferred approach is to use radiation-induced chemical curing. Fortunately, all current and future magnetic recording layers used for tape applications are now thin enough to allow efficient movement of light through the coating and to induce chemical reactions in the binder-rich regions that are the target of such curing reactions.It is well known that ultraviolet radiation (UV radiation) can activate the formation of free radicals that can attack unsaturated carbon compounds such as olefins, vinyls, and acrylates, initiating polymerization of these reactive species and creating more stable molecular structures. UV curing is also preferred because the underlayer 1006 can also bond to some substrates 1004 during the formation of free radicals, thereby improving the durability of the tape.

[0132] After curing the underlayer 1006, a magnetic recording layer 1008 is formed on or over the underlayer 1006. By drying and curing the underlayer 1006 prior to forming any type of magnetic recording layer 1008 thereon, interlayer mixing at the interface between the underlayer and the recording layer is minimized. This overcomes a problem that was widespread in the manufacture of conventional magnetic recording tapes and limited the achievable areal recording density of the tape.

[0133] In one exemplary approach, nanoparticles of a weakly magnetic material (chromium dioxide) are coated with an aromatic polymer shell (methylenebisdiphenylcarbamate with a functional acrylic polyester as the ester segment of the aromatic carbamate) and bonded together with a functional acrylic polymer. A composition of the above materials is dispersed into an ultraviolet-curable (UV-curable) emulsion using an ultrasonic dispersion process in a tetrahydrofuran (THF) and water solvent system, applied over the substrate 1004, dried, and cured.The dried coating contains the pigment encapsulated by the aromatic glassy polymer such that the matrix is ​​highly populated with over 40% of the magnetic and electrically conductive pigment, while maintaining an elastic, rubber-like interparticle matrix formed from the polyester acrylate regions of the carbamate binder. Process for the production of encapsulated magnetic nanoparticles

[0134] In different approaches, the magnetic starting nanoparticles, which are later encapsulated using one of the novel processes disclosed here, are produced using known techniques, e.g., milling. In other approaches, the magnetic starting particles are obtained in a ready-to-use, encapsulated form using one of the novel processes disclosed here.

[0135] The production of encapsulated magnetic nanoparticles can be achieved using various techniques. Previous approaches to encapsulating magnetic nanoparticles have proven unsuccessful. Rather than attempting to maintain the isolation of the encapsulated nanoparticle precursors (not yet converted to the final magnetic state by high-temperature conversion), preferred approaches involve mixing the magnetic nanoparticles with an organic solvent containing an aromatic dispersant. The absorption of the aromatic species onto the nanoparticles enables a stable suspension of the particles in the initial solvent, such as toluene, which is a good solvent for many suitable aromatic dispersants. The mixture is heated using ultrasonic dispersion energy to maintain the suspension.A high-boiling aromatic hydrocarbon such as anthracene, phenanthrene, pyrene, etc., is added to the approximate volume of toluene prior to distillation. The mixture is heated above the boiling point of toluene, and the distilled toluene leaves behind a molten suspension of the dispersed nanoparticles in the fully aromatic polyaromatic melt, such as molten phenanthrene, which melts above 380 °C.

[0136] In one exemplary approach, the mixture is heated in a pressure vessel to allow the temperature to be increased to 400 °C and maintained for four to six hours. The iron nanoparticles are converted into the magnetic epsilon form of iron oxide. During this process, the magnetic particles remain enclosed in a fully aromatic shell.

[0137] The mixture is then cooled to room temperature before processing to extract the encapsulated particles. Once cooled to room temperature, the waxy solid containing the dispersed nanoparticles is dissolved in a solvent such as toluene to redisperse the nanoparticles in the mixed aromatic solvents. Sufficient chloroform or the like is then added to allow separation and decantation of the aromatic layer from the particles suspended in the chloroform.

[0138] Dry particles can be recovered to produce an emulsion by distillation of the chloroform or a suspension obtained by solvent exchange to water if the aromatic encapsulation layer is modified to have sufficient residual polar functionality to enable stable dispersion in water. Recording layer

[0139] In some approaches, the recording layer 1008 has a new and novel structure. In one aspect, the new and novel recording layer 1008 may be provided on the medium 1000 with a conventional sublayer 1006 underneath. In another aspect, the new and novel recording layer 1008 may be provided on the medium 1000 with a new and novel sublayer 1006 underneath. In other approaches, the recording layer 1008 has a conventional structure and is provided on the medium 1000 with a new and novel sublayer 1006 underneath.

[0140] In approaches 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 encapsulate the particles prior to dispersion in a glassy encapsulating layer can be used as the flux diffusion layer, as has been the practice for over a decade in the manufacture of current tape media. Additional particles may, but are not required, be added to these sublayers to improve conductivity or abrasion resistance.

[0141] In preferred approaches, the recording layer 1008 comprises a novel composition in which the recording layer 1008 comprises encapsulated nanoparticles 1018, each comprising at least one magnetic nanoparticle 1020, and preferably only a single magnetic nanoparticle 1020, encapsulated by an encapsulation layer 1022, and a polymeric binder 1024 that binds the encapsulated nanoparticles. Generally, the magnetic strength of the magnetic nanoparticles in the recording layer 1008 is significantly higher than the magnetic strength of the nanoparticles in the underlayer 1006, if present.

[0142] An average concentration of the encapsulated nanoparticles in the recording layer 1008 is preferably at least about 35 weight percent (wt%), e.g., about 45-50 wt%, in a range of about 35-50 wt%, preferably in a range of about 46-50 wt%, or any other subrange within the above-mentioned ranges.

[0143] The magnetic nanoparticles in the encapsulated nanoparticles of the recording layer 1008 can be formed from any magnetic material suitable for the intended application, such as magnetic recording. Furthermore, in some approaches, magnetic materials suitable for magnetic imaging can be used as the magnetic nanoparticles. In different approaches, the magnetic nanoparticles comprise at least one magnetic material selected from the group consisting of alloys and / or oxides of nickel, cobalt, and iron, including mixed compounds and crystals using combinations of nickel, cobalt, and iron, such as iron-barium, NiFe, barium ferrite, and cobalt-platinum.

[0144] It should be noted that the approach described here is applicable to other nanoparticles, such as MnAl, that are not currently typically used for tape storage coatings, and even to non-magnetic dispersions that could benefit from improved control of coating integrity, such as SiC and SiO2 dispersions useful for sandpaper and other abrasives. Accordingly, any known type of magnetic nanoparticle can be used in different approaches.

[0145] In preferred approaches, the magnetic nanoparticles comprise at least one magnetic material selected from the group consisting of Co3O4, CoFe, Fe3O4, alpha iron oxide (α-Fe2O3), epsilon iron oxide (ε-Fe2O3), and Co(fcc). In further approaches, the magnetic nanoparticles may comprise manganese-aluminum alloys, oxides of magnetic metals, and Pinel ferrites.

[0146] The average diameter of the magnetic nanoparticles in the recording layer 1008 is preferably in a range of about 2 nm to about 20 nm, preferably in a range of about 2 nm to about 10 nm, especially for the epsilon iron oxide particles. The average diameter can be larger or smaller than this range depending on the size at which the magnetic nanoparticle loses its remanence and becomes superparamagnetic. In general, a smaller average diameter is better for increasing bit resolution.

[0147] To optimize the ultimate response of the recording layer to an external field applied during data writing, the encapsulated nanoparticles used for the recording layer preferably have the same composition, crystal structure, and morphology, as well as a very limited particle size range. In preferred approaches, more than about 80%, more preferably more than about 90%, even more preferably more than about 98% of the encapsulated nanoparticles contain only a single magnetic nanoparticle, and ideally, at least about 100% of the encapsulated nanoparticles contain only a single magnetic nanoparticle.

[0148] The aromatic polymer encapsulating the magnetic nanoparticles can be and / or comprise any of numerous different aromatic polymers, as long as the aromatic polymer in the sublayer 1006, and particularly for optimizing the magnetic nanoparticles in the recording layer, encapsulates at least about 75% of the surface area of ​​the magnetic nanoparticle, preferably at least about 90% of the surface area of ​​the magnetic nanoparticle, and ideally approximately 100% of the magnetic nanoparticle. In the recording layer, the effectiveness of particle encapsulation should be as close to 100% as can be achieved by a cost-effective process used in practice for large-scale production. Accordingly, the aromatic polymer forms at least a partial shell and preferably a complete shell around the magnetic nanoparticles.The average thickness of the aromatic polymer encapsulating the magnetic nanoparticles in the finished recording layer 1008 is preferably less than 1 nm. Preferably, the average thickness of the aromatic polymer shell is in a range from 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 could be slightly above or below these ranges. In some cases, clusters or aggregates of partially coated nanoparticles may form during the encapsulation process, which may persist in the final coating beyond the batch process. As long as these clusters and aggregates do not constitute a significant portion of the coating (e.g., less than 10% by volume) and are smaller than the thickness of the final coating, so that they do not cause surface roughness and defects (e.g.,a diameter of < 60% of the thickness of the final dried coating), the presence of agglomerations and aggregates should not limit the desired functionality of the layer.

[0149] In embodiments where the encapsulated nanoparticles are pyrolyzed, the average thickness of the resulting carbon shell ranges from about 0.05 nm to about 1 nm.

[0150] Such thin shells improve the packing density of the magnetic particles in the recording layer 1008 and thus enable a higher recording bit resolution.

[0151] Aromatic structures are preferred as an encapsulation layer for isolating magnetic nanoparticles due to their unique electronic properties, which ensure a weak but substantial separation of each nanoparticle from the magnetic field that couples it to its near neighbors in the final, densely packed, dry coating.

[0152] The aromatic polymer preferably has functional groups that exhibit an affinity for adhesion to iron oxide when magnetic iron nanoparticles are used. Examples of functional groups include carboxylate functional groups, nitrile functional groups, and others.

[0153] A preferred 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 a rubbery polymer chain in the paraposition to the styrene monomer. Preferably, the encapsulating layer comprises a polyaromatic film.

[0154] In further approaches, the aromatic polymer is one that is a known precursor used for the production of graphite, carbon fiber, carbon nanotubes, etc. Accordingly, the encapsulation layer can be a graphite-dominated continuous film.

[0155] The polymeric binder that binds the encapsulated nanoparticles together may comprise and / or include different types of binder material.

[0156] Considered approaches have attempted to incorporate encapsulated magnetic nanoparticles into conventional binder systems; however, such approaches have been found to yield recording layers with significantly higher noise and significantly lower signal performance than predicted based on the assumption that the particles are smaller and more densely packed in an aligned film. Although the reason for such poor performance in approaches using conventional binder systems is not fully understood, the inventor has determined that the novel techniques described herein produce a new recording layer that exhibits excellent recording performance far superior to approaches using conventional binder systems.

[0157] In preferred approaches, the binder contains an acrylic polymer, e.g., a polymer of acrylic acid or an acrylate, and preferably a functional acrylic polymer. In particularly preferred approaches, the polymeric binder contains a radiation-curable, rubbery acrylic polymer. Exemplary acrylic polymers suitable for use as binders include, in various approaches, acrylic-terminated polyesters and those containing components such as methyl methacrylate, acrylic acid, and others. The binder may contain, for example, an acrylic-terminated aliphatic polyester or an aliphatic polyether polymer. Generally, preferred polymeric binders are those having a number average molecular weight of less than about 2400, and preferably less than about 1200.

[0158] The binder used in the recording layer 1008 may be the same as or different from the binder used in the underlayer 1006 in different approaches.

[0159] The recording layer 1008 should be flexible (rubber-like) throughout the operating temperature range in use, while also providing tear resistance and impact resistance. Accordingly, preferred embodiments provide a recording layer 1008 having a glass transition temperature above about 35°C, preferably above about 45°C, and ideally at least about 50°C. This can be achieved through the selection of the binder.

[0160] Additional materials such as lubricants may be present in the recording layer 1008. However, an advantage of various approaches disclosed herein is that they allow for the omission of conventional additives such as abrasive particles in the recording layer.

[0161] An average thickness of the recording layer 1008, measured perpendicular to the plane of its formation, is less than about 0.2 microns, and preferably less than about 0.1 microns. An advantage of this thickness of a recording layer 1008 is that the UV light, even with the pigment contained therein, can reach all sections of the recording layer 1008, thereby ensuring rapid, continuous curing of the entire layer. Conventional recording layers that are thicker could not be UV-cured and therefore relied on other types of curing that were not as fast. Accordingly, in the production of the conventional tape, curing continued while the tape was wound onto a spool. However, winding the tape onto the spool created tensile stresses and strains (e.g.radial compression) throughout the band, resulting in changes in the mechanical properties of the band that differed from the band inside the center to the band outside the center.

[0162] When the recording layer 1008 is formed directly on a sublayer 1006, the recording layer 1008 is preferably applied after curing the sublayer 1006 to minimize intermixing of the layers. Accordingly, in preferred approaches, the recording layer 1008 substantially does not intermix with the sublayer 1006 (and vice versa).

[0163] Preferably, the underlayer 1006 has a total magnetic field strength in Oe of less than 200 Oe, and preferably less than 100 Oe. The underlayer 1006 may have a similar structure and / or similar properties as the underlayers disclosed elsewhere herein.

[0164] In some aspects, lubricant molecules 1030 are coupled to a surface of the recording layer 1008. The lubricant molecules may 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 an amount that would form a continuous lubricant film along the surface of the recording layer 1008.

[0165] In preferred approaches, no wear particles are present in the recording layer 1008, and ideally, no wear particles are present at all in the product. However, in further approaches, wear particles may be present in the recording layer 1008 and / or pass through from an underlayer 1006. The above mechanical construction of the recording layer 1008 with an electrically conductive underlayer 1006 is expected to achieve the desired low friction and head corrosion properties of the tape surface without the need for the inclusion of wear particles, which are an increasingly unacceptable defect and a source of damage to the shrinking read and write structures in current and future recording heads. Process for manufacturing the recording layer

[0166] A method for manufacturing the recording layer 1008, e.g., of a magnetic recording medium, according to different approaches is presented below. As an option, the present method can be implemented for manufacturing recording layers 1008 such as those described above. Of course, however, this method and others presented here can be used for manufacturing recording layers 1008 that may or may not be related to the exemplary aspects listed here. Furthermore, the methods presented here can be carried out in any desired environment. Furthermore, according to different approaches, more or fewer operations than those described below can be included in the method.It should also be noted that each of the features mentioned above can be used in any of the approaches described in relation to the different methods.

[0167] The method generally comprises forming a magnetic recording layer 1008 comprising encapsulated nanoparticles, each comprising at least one magnetic nanoparticle encapsulated by an aromatic polymer, and a polymeric binder that binds the encapsulated nanoparticles.

[0168] In one approach, creating the recording layer 1008 involves heating the magnetic nanoparticles and the aromatic polymer to a temperature that results in a suspension of the magnetic nanoparticles in the aromatic polymer. Generally, for most aromatic polymers, the temperature ranges from about 200 degrees Celsius to about 538 degrees Celsius, depending on the aromatic polymer used.

[0169] If the aromatic polymer has a simple aromatic structure, a temperature of less than 200 degrees Celsius can be used. The relative amounts of magnetic nanoparticles and aromatic polymer in the suspension are preferably selected to ensure the properties listed in the previous section and to avoid the formation of nanoparticle clusters.

[0170] An organic solvent can be mixed with the nanoparticles and the aromatic polymer to create a suspension that prevents clustering and sintering of the nanoparticles. Such solvents can include molten aromatic solvents such as phenanthrene. Preferably, the solvent is one that does not lead to oxidative reactions with the magnetic nanoparticles. Toluene or the like can also be added to further shift the mixture toward an emulsion.

[0171] In some approaches, the encapsulated particles are pyrolyzed, resulting in a magnetic nanoparticle encapsulated in a carbon shell.

[0172] The warm suspension of magnetic nanoparticles and aromatic polymer is mixed with a polymeric binder and a solvent to create a mixture. Ultrasonic dispersion is preferably used to create an emulsion. This technique for synthesizing encapsulated nanoparticles and polymer encapsulation advantageously eliminates the need for milling and redispersion from aggregated clusters of particles, which is typical of conventional manufacturing techniques.

[0173] In general, the solvent mixture should offer one or more, and preferably all, of the following properties: the most volatile solvent (the first to disappear upon drying) causes the polymeric binder to swell, the second or last solvent to disappear upon drying is ideally a poor solvent for the binder so that the solution undergoes theta states of this binder upon drying and forces the binder to collapse around the pigment rather than shrinking upon drying, which leads to undesirable stress in the finished coating.The final solvent, which disappears upon drying and is a non-solvent for the binder, forces the swollen chains to coil into their minimal free volume state, known as the theta state, as they transition from being well solvated by the first solvent to being enclosed by a non-solvent-rich environment upon drying. The layer is most stable when the polymeric binder is in the theta state, and this is the point at which curing should occur. UV curing is preferred when the polymeric binder is close to its theta state due to the speed at which curing occurs.

[0174] A preferred solvent is a water and THF solvent system in relative concentrations that make the solvent system predominantly azeotropic, with a slight excess of water to force the final coating to undergo theta states upon drying. The THF disappears first due to its higher volatility than water. Having the organic solvent disappear first allows for the film's coalescence to collapse and the stress to be reduced. The water then dominates the solvent transition, allowing the polymer to approach theta states.

[0175] In other approaches, the system can be water-dominated, resulting in a true emulsion, with the absorbed binder acting as an emulsifier and ensuring the rubber phase resin in the final coating. In other approaches, suitable solvents can include mixtures of volatile polar organic compounds with higher-boiling non-solvents for the binders, such as MEK / toluene, acetone / methyl isobutyl ketone, etc.

[0176] The resulting emulsion / solvent is applied to a structure such as the aforementioned undercoat layer 1006 or another substrate. Any suitable technique may be used to apply the emulsion / solvent. A preferred technique is a specially developed low-pressure, high-volume spray coating, which ensures rapid, uniform application without the streaks or thickness variations typical of a brush-stroke coating and modulation of the transitions that result from these very thin coatings from high-shear blade coating or die extrusion coating processes.

[0177] The applied mixture is partially dried or substantially completely dried to remove at least a portion of the solvent. The polymeric binder collapses onto the encapsulated microparticles as the solvent is removed during drying. In one aspect where the binder is hydrophobic, the last solvent to disappear from the applied mixture, such as water, is a non-solvent for the binder, thereby forcing the hydrophobic binder to collapse onto the pigments. This also minimizes residual stress in the dry coating. Drying is preferably performed using forced air under low-temperature conditions (less than about 75°C).

[0178] The at least partially dried applied mixture is cured to limit further expansion or contraction in the as-coated stress-free layers during subsequent processing and environmental stress to produce a thin, high-density recording layer 1008 with densely packed magnetic nanoparticles. In one approach, the at least partially dried applied mixture is irradiated. For example, UV light or other known irradiation is used to cause crosslinking of the polymeric binder. In another approach, a different curing process, such as heating, is performed to enhance a reaction of thermally reactive functional groups in the encapsulated nanoparticle layer with the rubbery binder phase of the dried film.

[0179] As an option, a lubricant may be added during the formation of the recording layer 1008, with the lubricant molecules 1030 ultimately being coupled to a surface of the recording layer 1008 during the formation of the recording layer 1008. The lubricant molecules may be bound by the surface, embedded in the surface, or both. Again, an amount of lubricant molecules along the surface of the recording layer 1008 is preferably less than an amount to create a continuous lubricant film along the surface of the recording layer 1008. In an exemplary approach, the lubricant molecules along the surface of the recording layer 1008 are positioned on average center-to-center apart by a distance in a range of about 2 to about 15 molecular radii.

[0180] In one approach, lubricant molecules 1030 are dispersed in the organic solvent phase and transported to the surface during drying, where they are grafted onto the surface during curing, forming a stable, low-friction layer without movement of the lubricant molecules to the drive bearing and head surfaces. This, in turn, reduces head contamination.

[0181] In further approaches, a lubricant is applied to the outer surface of the completed recording layer 1008.

[0182] In one illustrative example, a predominantly monodisperse suspension of magnetic nanoparticles encapsulated with an aromatic polymer, such as Co3O4, CoFe, Fe3O4, or Co(fcc), is combined with a rubbery polymer having radiation-curable end groups and side chains with a chain length sufficient to ensure a rubbery phase upon binding to radiation-curable end groups on the aromatic encapsulation layers of the dispersed nanoparticles upon curing. The resulting suspension is used to create a densely packed, thin recording layer 1008 in which a high-density recording can be recorded.The rubbery chain connected to the aromatic encapsulation layer terminates in an acrylic or methacrylic functional group, which can be UV-cured to create a highly cross-linked matrix in which the magnetic particles are completely encapsulated by an aromatic glassy polymer held in a continuous coating by swelling of the rubbery phase. For example, a low-molecular-weight acrylic-terminated polyester added to the solvent is used. UV curing of the solvent-swollen coating and the polyester occurs upon drying.

[0183] Compared to current magnetic recording media, various advantages of a magnetic recording tape with the new underlayer and the new recording layer formed thereon include, but are not limited to, a thinner recording layer, a more uniform distribution of the magnetic particles, a smoother, less blurred transition between the underlayer and the recording layer, a higher glass transition temperature, a reduced occurrence or almost complete elimination of gaps in the magnetic particles in the recording layer, etc. Each of these advantages results in a magnetic recording tape that has properties such as one or more of higher dimensional stability, greater tear resistance, higher recording resolution down to and below 1 nm, less noise, resulting in a higher signal-to-noise ratio, etc.shows, but is not limited to.

[0184] It is clear that the different features of the above systems and / or methodologies can be combined in any way, resulting in numerous combinations of the descriptions presented above.

[0185] It is further understood that embodiments of the present invention may be provided in the form of a service provided on behalf of a customer.

[0186] The inventive concepts disclosed herein have been exemplified using several exemplary scenarios, embodiments, and / or implementations to illustrate the variety of their features. It should be appreciated that the generally disclosed concepts are to be considered modular and may be implemented in any combination, implementation, or synthesis thereof. Furthermore, any modification, alteration, or equivalent of the presently disclosed features, functions, and concepts that would become apparent to one of ordinary skill in the art upon reading the present descriptions is also to be considered within the scope of this disclosure.

[0187] The descriptions of the various embodiments of the present invention have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the disclosed embodiments. Numerous modifications and variations will be apparent to those skilled in the art without departing from the scope of the described embodiments. The terminology used herein has been chosen to best explain the principles of the embodiments, their practical application, or technical improvement over current technologies, or to enable others of ordinary skill in the art to understand the disclosed embodiments.

Claims

[1] A product that has: a sub-layer (1006) comprising: first encapsulated nanoparticles (1012), each comprising a first encapsulated nanoparticle encapsulated by a first aromatic polymer (1014), and a first polymeric binder (1016) that binds the first encapsulated nanoparticles (1014); and a magnetic recording layer (1008) formed over the underlayer (1006), the recording layer (1008) comprising: second encapsulated nanoparticles (1020), each comprising a second encapsulated nanoparticle (1020) encapsulated by an encapsulation layer (1022), and a second polymeric binder (1024) that binds the second encapsulated nanoparticles (1020). [2] The product of claim 1, wherein the first magnetic nanoparticles (1012) have an average magnetic field strength of less than 200 Oersted (Oe). [3] The product of claim 1, wherein an average concentration of the first encapsulated nanoparticles (1012) in the underlayer (1006) is at least 35 vol%. [4] The product according to claim 1, wherein the backing layer (1006) characterized by is that it has a glass transition onset temperature of at least 35° Celsius in a graphical representation of a tensile storage modulus (E') with respect to temperature. [5] The product of claim 1, wherein the backing layer is electrically conductive to assist in the dissipation of charge in the product. [6] The product of claim 1, wherein the first magnetic nanoparticles (1012) comprise chromium oxide. [7] The product according to claim 1, wherein an average diameter of the first magnetic nanoparticles (1012) is in a range of 2 nanometers to 15 nanometers. [8] The product of claim 1, wherein the first aromatic polymer (1014) comprises a carbamate. [9] A product that has: a sub-layer (1006) comprising: first encapsulated nanoparticles (1012), each comprising a first encapsulated nanoparticle (1012) encapsulated by a first aromatic polymer (1014), and a first polymeric binder (1016) that binds the first encapsulated nanoparticles (1012); and a magnetic recording layer (1008) formed over the underlayer (1006), the recording layer (1008) comprising: second encapsulated nanoparticles (1020), each comprising a second encapsulated nanoparticle encapsulated by an encapsulation layer (1022), and a second polymeric binder (1024) binding the second encapsulated nanoparticles (1020), wherein the first polymeric binder (1016) comprises a methylene bis-diphenyl carbamate. [10] The product of claim 1, wherein an average thickness of the first aromatic polymer (1014) is in a range of 1 nanometer to 8 nanometers. [11] The product of claim 1, wherein the first polymeric binder (1014) comprises an acrylic polymer [12] The product of claim 1, wherein an average thickness of the underlayer (1006) is less than 1 micrometer. [13] The product of claim 1, wherein the second magnetic nanoparticles (1020) comprise at least one magnetic material selected from the group consisting of nickel, cobalt and iron. [14] The product of claim 1, wherein the second magnetic nanoparticles (1020) comprise at least one magnetic material selected from the group consisting of Co3O4, CoFe, Fe3O4, Fe2O3 and Co(fcc). [15] The product according to claim 1, wherein an average diameter of the second magnetic nanoparticles (1020) is in a range of 2 nanometers to 20 nanometers. [16] The product of claim 1, wherein the encapsulating layer (1024) is a layer selected from the group consisting of a polyaromatic film and a graphite-dominated continuous film. [17] The product of claim 1, wherein an average thickness of each encapsulation layer (1022) is less than 1 nanometer. [18] The product of claim 1, wherein the second polymeric binder (1024) is an acrylic polymer. [19] The product of claim 1, wherein an average thickness of the recording layer (1008) is less than 0.2 microns. [20] The product of claim 1, wherein no abrasion particles are present in the recording layer (1008). [21] The product of claim 1, comprising lubricant molecules coupled to a surface of the recording layer (1008). [22] The product of claim 21, wherein an amount of the lubricant molecules along a surface of the recording layer (1008) is less than an amount for forming a continuous lubricant film along the surface of the recording layer (1008). [23] The product of claim 1, wherein the encapsulation layer (1022) comprises a second aromatic polymer. [24] The product of claim 1, wherein the recording layer (1008) is substantially unmixed with the underlayer (1006). [25] A magnetic recording tape (1000) comprising the product according to any one of the preceding claims.

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