MAGNETIC RECORDING LAYER FOR TAPE MEDIA

Abstract

Product that features: - a recording layer (1008) which includes: - encapsulated nanoparticles (1010) each comprising exactly one magnetic nanoparticle encapsulated by an aromatic, polymer (1014) based encapsulation layer, and - a polymeric binder (1016) that binds the encapsulated nanoparticles (1010), - a sublayer (1006), wherein the recording layer (1008) is formed on the sublayer (1006), wherein the recording layer (1008) is not physically mixed with the sublayer (1006) in the product, such that an upper surface of the sublayer (1006) is substantially flat, with a modulation of less than 25% of the thickness of an interface between the sublayer (1006) and the recording layer, wherein the sublayer is electrically conductive to assist in the dissipation of a charge in the product, and - wherein the sublayer comprises encapsulated magnetic nanoparticles (1010) with a coercive force of less than 200 Oersted (Oe).

Description

TECHNICAL AREA

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

[0002] In magnetic storage systems, magnetic transducers read data from and write data to magnetic recording media. Data is written to the magnetic recording media by moving a magnetic recording transducer to a position above 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 the data can be read from and written to the desired storage 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 increased track and linear bit density on the recording tape and a reduction in the thickness of the magnetic tape medium. However, the development of tape drive systems with a small footprint and higher performance presents several challenges, ranging from the design of tape head assemblies for use in such systems to addressing the dimensional instability of the tapes.

[0004] In this context, several publications already exist: For example, document US 2014 / 0340788A1 describes a magnetic storage medium with magnetic nanoparticles encapsulated in nanotubes. Document US 2009 / 0053512A1, on the other hand, describes a multifunctional polymer-coated magnetic nanocomposite material. This material has a metallic core and can be used, for example, for magnetic tapes or supercapacitances. Document US 2015 / 0262742A1 additionally describes multilayer magnetic nanoparticles for a magnetic recording method. This method utilizes three different magnetic layers with varying magnetic anisotrons. Furthermore, document US 2006 / 0204793A1 describes a manufacturing process for magnetic material and high-density magnetic recording media. This process utilizes aluminum nanoparticles.Document US 2009 / 0136783A1 describes another magnetic recording medium and a process for its fabrication. This process utilizes SmCo-based magnetic nanoparticles and a hydrophobic binder. Additionally, document US 2003 / 0157325A1 describes monodisperse nanoparticles that form thin films. Document US 2004 / 0106009A1 also describes a magnetic recording medium with improved resolution compared to previous technologies, without compromising thermal stability. Document US 2006 / 0177705A1 describes a mass storage device with an intermediate layer to maintain the uniformity and order of magnetic nanoparticles. Finally, the document by Zalich, Michael A. [et al.] entitled "Structural and magnetic properties of oxidatively stable cobalt nanoparticles encapsulated in graphite shells" describes [further information needed]. In: Chemistry of materials, Vol. 18, 2006, No. 11, p.2648-2655. - ISSN 1520-5002. DOI: 10.1021 / cm051346h how oxidatively stable magnetic cobalt nanoparticles can be produced by an annealing process with poly(styrene-b-4-vinylphenoxyphthalonitrile) block copolymers.

[0005] Nevertheless, there remains a need to improve the recording and carrier layers of magnetic tapes and to further increase their storage density. SUMMARY

[0006] This problem is solved by the subject matter of the independent claims. Further embodiments and configurations are described in the dependent claims and the following description.

[0007] In one embodiment (version), the average thickness of each encapsulation layer is less than 1 nanometer. Such thin shells improve the packing density of the magnetic particles in the recording layer, thus enabling a higher recording bit resolution.

[0008] In another embodiment (or embodiments), no abrasion particles are present in the sublayer. It has been found that such abrasion particles represent an increasingly unacceptable defect and a source of damage to the shrinking read and write structures in current and future recording heads.

[0009] In another embodiment (or embodiments), the product has a sublayer, with the recording layer formed on the sublayer. The recording layer is essentially not mixed with the sublayer. This feature solves a long-standing problem with magnetic recording tape products, namely the mixing of the layers at their interface and the well-known problems that such mixing entails.

[0010] In one embodiment (or design), the sublayer is electrically conductive. The electrical conductivity of the sublayer aids in dissipating the charge, for example, by transporting the charge to a grounded junction, thereby minimizing the charge scattering into the head and consequently reducing the risk of liquid condensation forming a conductive path between the tape and the head surface, which could otherwise lead to electrochemical corrosion of the recording head structures.

[0011] In a preferred embodiment, the recording layer is part of a magnetic recording tape.

[0012] According to another aspect, a product features a recording layer. This recording layer comprises encapsulated nanoparticles, each containing a magnetic nanoparticle encapsulated by an encapsulation layer and a polymeric binder that binds the encapsulated nanoparticles. The average diameter of the magnetic nanoparticles ranges from 2 to 20 nanometers. The average thickness of the recording layer is less than 0.2 microns.Several advantages of a magnetic recording product with the new recording layer include, but are not limited to, a thinner recording layer, a more uniform distribution of magnetic particles, a smoother, less indistinct transition between the sublayer and the recording layer, a higher glass transition temperature, and a reduced occurrence or near-complete elimination of gaps in the magnetic particles within the recording layer. Each of these advantages results in a magnetic recording product, such as a tape, exhibiting, but are not limited to, improved tear resistance, higher recording resolution down to and below 1 nm, reduced noise resulting in a higher signal-to-noise ratio.

[0013] Further aspects and approaches of the present invention will become apparent from the following detailed description, which, when considered in conjunction with the drawings, exemplifies the principles of the invention. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1A is a schematic diagram of a simplified tape drive system. Fig. Figure 1B is a schematic diagram of a tape cassette 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. 2B is a view of a belt support surface along line 2B in Fig. 2A. Fig. 2C is an accurate view of circle 2C in Fig. 2B. Fig. 2D is an accurate partial view of a belt contact surface of a module pair. Fig. Figure 3 is a partial view of the tape contact area of ​​a magnetic head with a read-write configuration. Fig. Figure 4 is a partial view of the tape contact area of ​​a magnetic head with a read-write-read configuration. Fig. Figure 5 is a side view of a magnetic tape head with three modules, in which all modules are basically located lengthwise in approximately parallel planes. Fig. Figure 6 is a side view of a magnetic tape head with three modules in a tangential (angled) configuration. Fig. Figure 7 is a side view of a magnetic tape head with three modules in a truncation configuration. Fig. Figures 8A-8C are schematic views illustrating the principles of band bulging. Fig. Figure 9 is a representative diagram of files and directories stored on a magnetic tape according to one aspect of the present invention. Fig. Figure 10 is a partial sectional view of the basic structure of a magnetic recording medium according to different approaches. Fig. Figure 11 is a graphic representation showing a dynamic mechanical analysis (DMA) of coatings to determine the critical pigment volume concentration (CPVC) according to different approaches. Fig. Figure 12 is a TEM image (TEM: transmission electron microscope) of a cross-section of a conventional recording tape. DETAILED DESCRIPTION

[0014] The following description serves 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 can be used in any of the different possible combinations and implementations in combination with other described features.

[0015] Unless otherwise specifically stated herein, all terms shall be interpreted in their broadest possible sense, including meanings implied by the description as well as meanings understandable to experts and / or defined in dictionaries, contracts, etc.

[0016] It should also be noted that the singular forms “ein”, “eine” and “der”, “die”, “das” include plural references in the sense used in the description and the accompanying claims, unless otherwise stated.

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

[0018] In a general approach, a product has a recording layer. The recording layer contains encapsulated nanoparticles, each of which has a magnetic nanoparticle encapsulated by an encapsulation layer. A polymeric binder binds the encapsulated nanoparticles.

[0019] In another general approach, a product features a recording layer. This recording layer comprises encapsulated nanoparticles, each containing a magnetic nanoparticle encapsulated by an encapsulation layer, and a polymeric binder that binds the encapsulated nanoparticles. The average diameter of the magnetic nanoparticles ranges from 2 to 20 nanometers. The average thickness of the recording layer is less than 0.2 microns. Exemplary operating environment

[0020] Fig. Figure 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 in 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.

[0021] As shown, a tape feed cassette 120 and a take-up roller 121 are provided for holding a tape 122. One or more of the rollers can form part of a removable cassette and are not necessarily part of the tape drive 100. The tape drive, as shown in Fig. Figure 1A can further comprise a drive motor (or motors) for driving the tape feed cassette 120 and the take-up reel 121 for moving the tape 122 over a tape head 126 of any type. Such a head can comprise an arrangement of reading devices, writing devices, or both.

[0022] 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 can be a processor and / or any logic for controlling any subsystem of the drive 100, or it can include such logic. The controller 128 typically controls, for example, head functions such as servo sequences, writing data, reading data, etc. The controller 128 can have at least one servo channel and at least one data channel, each of which includes data flow processing logic designed to process and / or store information to be written to and / or read from the tape 122.The controller 128 can operate using various approaches with logic known in engineering as well as any logic disclosed herein, and can thus be considered a processor with respect to any of the tape drive descriptions included herein. The controller 128 can be coupled to a memory 136 of any known type, in which instructions executable by the controller 128 can be stored. Furthermore, the controller 128 can be configured and / or programmable to execute or control part or all of the methodology presented herein. Thus, the controller 128 can be considered designed to execute different workflows by means of logic programmed into one or more chips, modules, and / or blocks; by software, firmware, and / or other instructions accessible to one or more processors, etc.; and by combinations thereof.

[0023] The cable 130 can have read / write circuits for sending data to be recorded on the tape 122 to the tape head 126 and for receiving data read from the tape 122 by the tape head 126. An actuator 132 controls the position of the tape head 126 relative to the tape 122.

[0024] An interface 134 for communication between the tape drive 100 and an (internal or external) host 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 can be seen by experts.

[0025] Fig. Figure 1B shows an exemplary tape cassette 150, which, depending on the approach, can incorporate any configuration of the magnetic recording media in tape form described here. Such a tape cassette 150 can be used with a system like the one described in Fig. Figure 1A is used. As shown, the tape cassette 150 has a housing 152, a tape 122 inside the housing 152, and an optional non-volatile memory 156 coupled to the housing 152. In some approaches, the non-volatile memory 156 can be embedded inside the housing 152, as shown in Fig. Figure 1B shows this. In other approaches, the non-volatile memory 156 can be located inside or outside the housing 152 without modification of the housing 152. The non-volatile memory can, for example, be embedded in a self-adhesive sticker 154. In a preferred approach, the non-volatile memory 156 can be a solid-state memory (e.g., flash memory), a solid-state storage device (ROM), etc., which is embedded in or coupled to the inside or outside of the tape cassette 150. The non-volatile memory can be accessed by the tape drive and the tape operating software (the driver software), and / or another device.

[0026] Fig. Figure 2A shows an exemplary side view of a flatly offset, bidirectional, two-module magnetic tape head 200, which can be implemented in the context of the present invention. As shown, the head has two bases 202, each provided with a module 204 and attached to each other at a small angle α. The bases can be U-profiles coupled to each other by means of an adhesive. Each module 204 has a substrate 204A and a closure 204B, commonly referred to as a "gap," with a thin-film section in which the read and / or write devices 206 are formed. In use, a tape 208 is moved along a media support surface (tape support surface) 209 over the modules 204 for reading and writing data to and from the tape 208 using the read and write devices as shown.The wrap angle θ of the band 208 at the edges leading onto and down from the flat media holding surfaces 209 is normally between about 0.1 degrees and about 3 degrees.

[0027] The substrates 204A are typically made of a wear-resistant material such as ceramic. The closures 204B may be made of the same or a similar ceramic as the substrates 204A.

[0028] The read and write devices can be arranged in a piggyback or co-opted configuration. An exemplary piggyback configuration has a (magnetically inductive) write device transducer on top of (or beneath) a (magnetically shielded) read device transducer (e.g., a magnetoresistive read device, etc.), with the write device poles and read device shields generally being separate. An exemplary co-opted configuration has a read device shield in the same physical layer as a write device pole (hence "co-opted"). The read and write devices can also be arranged in a nested configuration. Alternatively, any arrangement of channels can include only read devices or only write devices.Each of these arrangements can include one or more servo track readers for reading servo data from the medium.

[0029] Fig. 2B shows the belt support surface 209 of one of the modules 204 along line 2B in Fig. 2A. A representative tape 208 is shown in dashed lines. The module 204 is preferably long enough to hold the tape when the head moves between data tapes.

[0030] In this example, tape 208 contains 4 to 32 data tapes, e.g., as in Fig. Figure 2B shows 16 data tapes and 17 servo tracks 210 on a half-inch-wide tape 208. The data tapes are formed between the servo tracks 210. Each data tape can have a number of data tracks, for example, 1024 data tracks (not shown). During read / write operations, the read and / or write devices 206 are positioned at specific track positions within one of the data tapes. External read devices, sometimes referred to as servo read devices, read the servo tracks 210. The servo signals are, in turn, used to keep the read and / or write devices 206 aligned with a specific set of tracks during the read / write operations.

[0031] Fig. 2C shows several in a column 218 on module 204 in circle 2C in Fig. 2B trained read devices and / or write devices 206. As shown, the arrangement of read devices and write devices 206 includes, for example, 16 write devices 214, 16 read devices 216, and two servo read devices 212, although the number of elements may vary. Exemplary approaches include 8, 16, 32, 40, and 64 active read devices and / or write devices 206 per arrangement, and alternatively, nested constructions with odd numbers of read devices or write devices such as 17, 25, 33, etc. One exemplary approach includes 32 read devices per arrangement and / or 32 write devices per arrangement, where the actual number of converter elements may be larger, e.g., 33, 34, etc.This allows for slower tape movement, thereby reducing speed-induced overrun and mechanical difficulties, and / or requiring fewer "bulges" for filling or reading the tape. Although the read and write devices can be arranged in a piggyback configuration, as in . Fig. As shown in Figure 2C, the read devices 216 and write devices 214 can also be arranged in a nested configuration. Alternatively, each arrangement of read devices and / or write devices 206 can have only read devices or only write devices, and the arrangements can include one or more servo read devices 212. As can be seen from the overview of the Fig. As 2A and 2B-2C show, each module 204 can have a complementary set of reading devices and / or writing devices 206 for things like bidirectional reading and writing, the capacity to read and write simultaneously, backward compatibility, etc.

[0032] Fig. Figure 2D shows a partial view of the tape contact surface of complementary modules of a magnetic tape head 200 according to one approach. In this approach, each module has several read / write pairs (R / W pairs, R / W: read / write) formed on a common substrate 204A and an optional electrically insulating insulating layer 236 in a piggyback configuration. The write devices 214 and the read devices 216 are aligned across them parallel to an intended direction of movement of a tape medium to form an R / W pair, exemplified by R / W pairs 222. It should be noted that the intended direction of movement of the tape is occasionally referred to here as the direction of movement of the tape, and such terms may be used interchangeably. Such a direction of movement of the tape can arise from the structure of the system, e.g.This can be deduced by checking the guides; observing the actual direction of movement of the belt relative to the reference point; etc. Furthermore, in a system suitable for bidirectional reading and / or writing, the direction of movement of the belt is typically parallel in both directions, and thus both directions can be considered equivalent.

[0033] Several R / W pairs 222, such as 8, 16, 32 pairs, etc., can be provided. As shown, the R / W pairs 222 are aligned linearly across the arrangement in a direction generally perpendicular to the direction of movement of the belt. However, the pairs can also be aligned diagonally, etc. The servo reading devices 212 are positioned on the outside of the arrangement of R / W pairs, their function being generally known.

[0034] In general, the magnetic tape medium moves either in a forward or a reverse direction, as indicated by arrow 220. The magnetic tape medium and the head assembly 200 operate in a transducer relationship in a manner generally known in the art. The head assembly 200 comprises two thin-film modules 224 and 226 of generally identical construction.

[0035] Modules 224 and 226 are connected to each other to create a single physical unit for providing the capacity of simultaneous reading and writing by activating the writing device of the front module and the reading device of the rear module, which is aligned parallel to the direction of movement of the belt with respect to the writing device of the front module, with a space between their (partially shown) closures 204B.When a module 224, 226 of a magnetic tape head 200 is manufactured, layers are produced 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-zircon-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 writing device poles 228, 230 and a coil (not shown). The sensor can belong to any known type, including those based on magnetoresistance (MR), GMR, AMR, tunneling magnetoresistance (TMR), etc.

[0036] The first and second writing device poles 228, 230 can be made of materials with a high magnetic moment, 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. Examples of insulating materials include aluminum oxide and other oxides, insulating polymers, etc.

[0037] The tape head 126 can be configured with multiple modules, preferably three or more. In a write-read-write head (WRW head, WRW: write-read-write), outer modules for writing flank one or more inner modules for reading. Referring to Fig. Figure 3, which shows a WRW configuration, shows that the outer modules 252 and 256 each have one or more arrangements of writing devices 260. The inner modules 254 according to Fig. 3 feature one or more arrangements 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 variants, one or more of the modules may have read / write converter pairs. Furthermore, more than three modules may be present. In other approaches, two outer modules may flank two or more inner modules, e.g., in a WRRW, an RWWR arrangement, etc. For the sake of simplicity, a WRW head is mainly used here to illustrate aspects of the present invention. Those skilled in the art familiar with the present teachings will recognize how implementations of the present invention can be applied to configurations other than a WRW configuration.

[0038] Fig. Figure 5 shows a magnetic head 126 according to an approach comprising a first, second, and third module 302, 304, 306, each having a belt support surface 308, 310, 312, which may be flat, contoured, etc. It should be noted that, although the term "belt support surface" might seem to imply that the surface facing the belt 315 is in physical contact with the belt support surface, this is not necessarily the case. Rather, only a portion of the belt needs to be in constant or discontinuous contact with the belt support surface, with other sections of the belt sliding (or "floating") on a layer of air above the belt support surface, sometimes referred to as an "air bearing." The first module 302 is called the "front" module because it is the first module the belt encounters in a three-module design for a belt moving in the specified direction. The third module, 306, is referred to as the "rear" module.The rear module follows the middle module and is the last module the belt encounters in a three-module construction. The front and rear modules 302 and 306 are collectively referred to as the outer modules. It should also be noted that the outer modules 302 and 306 alternate as the front module depending on the direction of movement of the belt 315.

[0039] In one approach, the band bearing 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 according to Fig. 6, to be included), and the belt bearing surface 310 of the second module 304 is located above the belt bearing surfaces 308, 312 of the first and third modules 302, 306. As described below, this has the effect of generating the desired wrap angle α2 of the belt with respect to the belt bearing surface 310 of the second module 304.

[0040] If the belt support surfaces 308, 310, 312 lie along parallel or nearly parallel, but offset, planes, the belt should intuitively detach from the belt support surface 308 of the front module 302. However, it was experimentally found that the vacuum generated by a lifting edge 318 of the front module 302 is sufficient to hold the belt in contact with the belt support surface 308 of the front module 302. A rear 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 across the belt support surface 310 of the second module 304. The belt remains in close proximity to the belt support surface until it is very close to the rear 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 specifically designed for read-write applications.

[0041] One benefit of these and other aspects described here 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 bearing surfaces 308, 310 and W is the width between the opposite ends of the belt bearing surfaces 308, 310. An exemplary inner wrap angle α2 lies in the range of approximately 0.3° to approximately 1.1°, although it can be any angle required by the design.

[0042] Advantageously, the inner wrap angle α2 on the side of module 304 that receives the belt (leading edge) is larger than the inner wrap angle α3 at the trailing edge, since the belt 315 slides over the trailing module 306. This difference is generally advantageous because a smaller α3 tends to counteract what was previously a more acute existing effective wrap angle.

[0043] It is noted that the belt bearing surfaces 308, 312 of the outer modules 302, 306 are positioned such that a negative wrap angle is achieved at the rear edge 320 of the front module 302. Provided that the position of the lever area formed on the belt where it detaches from the head is adequately taken into account, this is generally advantageous because it helps to reduce friction due to contact with the rear edge 320. This negative wrap angle also reduces flutter and chafing damage to the elements on the front module 302. Furthermore, the belt 315 on the rear module 306 hovers above the belt bearing surface 312, thus virtually eliminating wear on the elements when the belt moves in this direction. In particular, the belt 315 carries air and therefore does not slide significantly on the belt bearing surface 312 of the third module 306 (although some contact may occur).This is permissible because the front module 302 is writing, whereas the rear module 306 is inactive.

[0044] Write and read functions are performed by different modules at any given time. In one approach, the second module 304 has multiple data and optional servo read devices 331, but no write devices. The first and third modules 302 and 306 have multiple write devices 322, but no data read devices, except that the outer modules 302 and 306 may optionally have servo read devices. The servo read devices can be used to position the head during read and / or write operations. The servo read device(s) on each module is (are) typically located at the end of the array of read or write devices.

[0045] By placing only read devices or side-by-side write devices and servo read devices in the gap between the substrate and the closure, the gap length can be significantly reduced. Typical heads feature piggyback read and write devices, with the write device positioned above each read device. 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 achievable here exhibits fewer wear-related problems.

[0046] In some approaches, the second module 304 has a closure, whereas the first and third modules 302 and 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).

[0047] At the in Fig. In the approach shown in Figure 5, the first, second, and third modules 302, 304, 306 each have a closure 332, 334, 336 that extends along the tape bearing surface of the associated module, effectively positioning the read / write elements away from the edge of the tape bearing surface. The closure 332 on the second module 304 can be a ceramic closure of a type typically found on tape heads. However, the closures 334, 336 of the first and third modules 302, 306 can be shorter, measured parallel to a direction of movement of the tape across the respective module, than the closure 332 of the second module 304. This makes it possible to arrange the modules closer together. One way to produce shorter closures 334, 336 is to grind down the standard ceramic closures of the second module 304 by one size.Another method is the coating or deposition of thin-film closures over the elements during thin-film processing. For example, a thin-film closure made of a hard material such as Sendust or a nickel-iron alloy (e.g., 45 / 55) can be created on the module.

[0048] With ceramic or thin-film closures 334, 336 of reduced thickness or without closures on the outer modules 302, 306, the distance between the write and read gaps can be reduced to less than approximately 1 mm, e.g., to approximately 0.75 mm, or to 50% less than the spacing typically used in an open tape head for linear tapes (LTO tape head, LTO: linear tape open). The open space between the modules 302, 304, 306 can still be set to approximately 0.5 to 0.6 mm, which is ideal for stabilizing tape movement via the second module 304 in some applications.

[0049] Depending on the belt tension and strength, it may be desirable to angle the belt contact surfaces of the outer modules relative to the belt contact surface of the second module. Fig. Figure 6 shows a device in which the modules 302, 304, 306 have a tangential or nearly tangential (angled) configuration. In particular, the belt bearing surfaces of the outer modules 302, 306 are approximately parallel to the belt with the desired wrap angle α2 on the second module 304. In other words, the planes of the belt bearing 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. In this approach, the belt also jumps off the rear module 306, 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.

[0050] Typically, the strap wrap angles can be found approximately midway between those in the Fig. 5 and Fig. The 6 approaches shown will be used.

[0051] Fig. Figure 7 shows a device in which the modules 302, 304, 306 are arranged in a wrap-around configuration. Specifically, the tape contact surfaces 308, 312 of the outer modules 302, 306 are angled slightly more than the tape 315 when set to the desired wrap angle α2 with respect to the second module 304. In this approach, the tape does not jump off the rear module, thus 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 just written. Thus, these approaches are preferred for write-read-write, read-write-read, and write-write-read applications. In the latter approaches, the closures should be wider than the tape surfaces to ensure read capability. The wider closures may require a wider gap-to-gap spacing.Therefore, a preferred approach has a write-read-write configuration where shortened closures can be used, thus allowing shorter gap-to-gap distances.

[0052] Additional aspects of the in the Fig. 6 and Fig. The 7 approaches shown are similar to those listed above.

[0053] A 32-channel version of a Multi-Module Tape Head 126 can use Cable 350 with conductors spaced the same or closer to or than current 16-channel piggyback LTO modules, or alternatively, the connections on the module can be organically configured to reduce cable span by 50%. For the write devices, which may have integrated servo read devices, over / under unshielded write-pair cables can be used.

[0054] The outer wrap angles α1 can be adjusted in the drive unit, for example, by guides of any type known in engineering, such as adjustable rollers, slide rails, etc., or alternatively by cantilevers that are integrally formed with the head. For instance, rollers with an offset axis can be used to adjust the wrap angles. The offset axis creates a rotating arc that allows for precise adjustment of the wrap angle α1.

[0055] A conventional U-profile assembly can be used for the assembly of each of the approaches described above. Accordingly, compared to heads of previous generations, the mass of the resulting head can be maintained or even reduced. In other approaches, the module can be designed as a single-piece body. It will be apparent to those skilled in the art familiar with the present teachings that other known methods for manufacturing such heads can be adapted for use in the construction of such heads. Furthermore, unless otherwise specified, processes and materials of types known in the art can be adapted for use in different approaches in accordance with the present teachings, as will be apparent to those skilled in the art upon reading the present disclosure.

[0056] When a tape is guided over a module, it is preferable that the tape passes sufficiently close to the magnetic transducers on the module to ensure efficient reading and / or writing, e.g., with a low error rate. According to some approaches, tape bulging can be used to ensure that the tape passes close enough to the section of the module containing the magnetic transducers. For a better understanding of this process, the following are shown: Fig. 8A - 8C the principles of band bulging. Fig. Figure 8A shows a module 800 with an upper strip bearing surface 802 extending between opposing edges 804 and 806. A stationary strip 808 is shown wrapped around the edges 804 and 806. As shown, the bending stiffness of the strip 808 lifts the strip from the strip bearing surface 802. Strip tension tends to flatten the strip profile, as shown in Fig. Figure 8A shows that when the belt tension is minimal, the curvature of the belt is more parabolic than shown.

[0057] Fig. Figure 8B shows the belt 808 in motion. The leading edge, i.e., the first edge the belt encounters as it moves, can serve to vent air from the belt, thereby creating an air pressure below ambient pressure between the belt 808 and the belt support surface 802. Fig. 8B is the leading edge, which is the left edge, and the right edge is the trailing edge when the belt moves from left to right. As a result, the ambient pressure above the belt pushes it towards the belt support surface 802, creating a belt bulge near each of the edges. The belt's bending stiffness resists the effect of the ambient pressure, causing the belt bulge near both the leading and trailing edges. The model predicts that the two bulges will have very similar shapes.

[0058] Fig. Figure 8C shows how the pressure below the ambient pressure pulls the belt 808 towards the belt support surface 802 even when a rear guide 810 is arranged above the plane of the belt support surface.

[0059] It follows that tape curvature can be used to guide the path of a tape as it passes over a module. As previously explained, tape curvature can be used to ensure that the tape is guided 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.

[0060] Magnetic tapes can be stored in tape cartridges, which in turn are stored in memory slots or similar repositories within a data storage library. The tape cartridges can be stored in the library in such a way that they are accessible for physical retrieval. In addition to magnetic tapes and tape cartridges, data storage libraries can include data storage drives that store data on the magnetic tapes and / or retrieve data from them. Furthermore, tape libraries and the components they comprise can implement a file system that provides access to a tape and the data stored on it.

[0061] File systems can be used to control how data is stored in and retrieved from storage. Thus, a file system can contain the processes and data structures that an operating system uses to track files in storage, such as how the files are organized within that storage. A linear tape file system (LTFS) is an exemplary file system format that can be implemented to enable access to compatible tapes in a given library. It should be acknowledged that different aspects described here can be implemented with a wide variety of file system formats, including, for example, IBM Spectrum Archive Library Edition (LTFS LE).However, to provide context and solely as an aid to the reader, some of the approaches described below may be described with reference to LTFS, which is a type of file system format. This is done merely as an example and should not be interpreted as limiting the invention as defined in the claims.

[0062] A tape cassette can be "loaded" by inserting the cassette into the tape drive, and the tape cassette can be "removed" by taking the tape cassette out of the tape drive. Once loaded into a tape drive, the tape in the cassette can be "threaded" through the drive by physically pulling the tape (the magnetic recording section) from the tape cassette and passing it over a magnetic head of a tape drive. Furthermore, the tape can be wound onto a take-up reel (see, for example, 121 in the preceding Fig. 1A) are attached to move the tape over the magnetic head.

[0063] Once threaded into the tape drive, the tape can be "installed" in the cartridge by reading metadata from the tape and putting it into a state where LTFS can use it as part of a file system. To "uninstall" a tape, metadata (e.g., a directory) is preferably written to the tape first, after which the tape can be removed from the state where LTFS can use it as part of a file system. Finally, to "unthread" the tape, it is removed from the take-up reel and physically placed back into the cartridge. The cartridge can remain loaded into the tape drive even after the tape is unthreaded, for example, to wait for another read and / or write request. In other cases, however, the tape cartridge may be emptied after the tape is unthreaded, such as...as described above, taken from the tape drive.

[0064] A 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 recording data to a tape with only one partition, metadata (e.g., mapping information) is continuously appended to the end of previously written data, as it is frequently updated and rewritten accordingly. This means that to access the most recent copy of the tape's metadata, the most recent information is read when the tape is initially mounted. This introduces a significant delay into the mounting process of any given tape.

[0065] To address the delay caused by tape media with a single partition, the LTFS format uses a tape divided into two partitions: a directory partition and a data partition. The directory partition can be designed to record metadata (meta-information) such as file association information (a directory), while the data partition can be designed to record the data itself, such as the data itself.

[0066] Becomes Fig. As shown in Figure 9, a magnetic tape 900 with a directory subdivision 902 and a data subdivision 904 is represented 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 the directory subdivision 902 at the beginning of the tape 906, as will be apparent to those skilled in the art upon reading this description.

[0067] When directory information is updated, the previous version is preferably overwritten, thus ensuring that the updated directory information is accessible at the beginning of the tape in the directory subdivision. According to the Fig. In the specific example shown in Figure 9, the latest version of the metadata for Directory 3 is recorded in directory subdivision 902 at the beginning of tape 906. In contrast, all three versions of the metadata for Directory 1, Directory 2, and Directory 3, as well as the data for File A, File B, File C, and File D, are recorded in data subdivision 904 of the tape. Although Directory 1 and Directory 2 are old (e.g., obsolete) directories, these old directories remain stored in data subdivision 904 on tape 900 without being overwritten, because information is written to the tape by appending it to the end of the previously written data, as described above.

[0068] Depending on the desired approach, the metadata in directory subdivision 902 and / or data subdivision 904 can be updated in the same or different ways. According to some approaches, the metadata in directory and / or data subdivision 902 and 904 can be updated in response to tape uninstallation, for example, so that the directory can be quickly read from the directory subdivision when the tape is remounted. Preferably, the metadata is also written to data subdivision 904 so that the tape can be remounted using the metadata recorded there, for example, as a backup option.

[0069] According to 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 period of time which can be set by the user, e.g. to reduce data loss in the event of a sudden power failure. Magnetic recording media and the fabrication of their layers

[0070] Fig. Figure 10 shows a partial sectional view, not to scale, of the basic structure of a magnetic recording medium 1000 according to various approaches described herein. As an option, the present magnetic recording medium 1000 can be implemented in conjunction with features of any other approach listed herein, such as those described with reference to the other figures. Of course, such a magnetic recording medium 1000 and others presented herein can be used for different applications and / or in implementations, which may, but need not, be specifically described in the exemplary approaches listed herein. Furthermore, the magnetic recording medium 1000 presented herein can be used in any desired environment.The magnetic recording medium 1000 was developed in various implementations disclosed herein to improve the stability and performance of tape storage media across the required environments for use and storage.

[0071] Unless otherwise specified herein, the various layers of the magnetic recording medium 1000 may have a conventional construction, design, and / or function. Different approaches may incorporate a new and novel layer alongside conventional layers. Other approaches may combine several new and novel layers with other conventional layers.

[0072] Unless otherwise described herein, the various layers of the magnetic recording medium 1000 can be produced using conventional methods, in particular if the respective layer is of a conventional construction.

[0073] The magnetic recording medium 1000 is preferably a magnetic recording tape, but in other aspects it is a different type of deformable media.

[0074] As in Fig. As shown in Figure 10, four base layers are present in the magnetic recording medium 1000. An optional backside coating 1002 is arranged along one side (the bottom side in the figure) of a substrate 1004. A sublayer 1006 is arranged along another side (the top side in the figure) of the substrate 1004. A recording layer 1008 is arranged over the sublayer 1006. In different approaches, additional layers of conventional construction can be present in the magnetic recording medium 1000. For example, the backside coating can be omitted, and to enable recording on both sides of the finished tape, multiple layers can be applied to both sides of the substrate. Back coating

[0075] The back-side coating 1002 may be present in the magnetic recording medium 1000, but this is not required. The back-side coating 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 back-side coating material may be used. Preferably, the back-side coating 1002 is composed of a material that offers one or more of the following advantages: facilitating separation from another section of tape wound on a reel above it, improving tribology, dissipating static electricity, etc. A preferred thickness of the back-side coating 1002 is less than about 0.3 microns, preferably less than about 0.2 microns. substrate

[0076] Substrate 1004 is preferably of conventional construction, design, and function. Substrate 1004 is typically the strongest layer. Exemplary materials for substrate 1004 include polyethylene terephthalate (polyester or PET), polyethylene naphthalate (PEN), super-tensile reinforced PEN, an aramid-like material (e.g., solubilized para-imide such as that offered under the trade name Mictron™, distributed by Toray Industries, Inc., with its registered office at Nihonbashi Mitsui Tower, 1-1, Nihonbashi-Muromachi, 2-Chrome, Chuo-Ku, Tokyo 103-8666, Japan), etc. lower class

[0077] The sublayer 1006 fulfills one or more of the following functions in the structure: attenuation of the magnetic signal passed through the recording layer, adhesion of the recording layer to the substrate 1004, etc. Accordingly, in most of the approaches described here, the function of the sublayer 1006 is not to retain the flux of the writing device, but rather to improve the writing flux field from the write head element when writing to the recording layer 1008. Furthermore, any retained magnetic moment alignment from the writing process is preferably weak or absent to minimize noise during readback.

[0078] A crucial attribute of the occupied magnetic coating in the sublayer, according to various approaches, is the rapid absorption of the stray field passing through the preceding recording layer during the very rapid magnetic switching that occurs during writing. The ideal sublayer should have a very low residual torque (M r ) so that it does not retain an orientation after the writing field has passed through this volume of the sublayer.

[0079] In some approaches, the sublayer 1006 has a new and novel structure. In one aspect, the new and novel sublayer 1006 can be present in the medium 1000 with a conventional recording layer 1008 above it. In another aspect, the new and novel sublayer 1006 can be present in the medium 1000 with a new and novel recording layer 1008 above it. In still other approaches, the sublayer 1006 has a conventional structure and is present in the medium 1000 with a new and novel recording layer 1008 above it.

[0080] In different approaches, the sublayer 1006 has one or more of the following properties, and preferably all of them: electrically conductive, slightly magnetic (a total magnetic strength in oersteds (Oe) of less than 200 Oe, and preferably less than 100 Oe). Ideally, to improve the transition to the recording layer 1008, the sublayer is applied and calendered before the recording layer 1008 is created, as described in more detail below. In a preferred embodiment, the sublayer 1006 has about one-tenth the coercivity of the recording layer 1008 (in oersteds) and a low residual magnetization, which allows the sublayer 1006 to act as a magnetic flux absorber without generating signal interference with the overlying recording layer 1008.

[0081] The electrical conductivity of the sublayer 1006 helps reduce corrosion of magnetic heads operating on a tape. Specifically, during tape unwinding, the separation of the recording layer generates a triboelectric potential and current that can trigger a static discharge in a dry environment and create an electrochemical pathway for head corrosion in a humid environment. Both of these situations are undesirable in terms of tape performance and durability, and both are believed to be significant contributors to head corrosion. The electrical conductivity of the sublayer 1006 aids in dissipating this charge, e.g.,by transporting the charge to a node coupled to an earthing point, thereby minimizing the charge scattering into the head and consequently reducing the risk of liquid condensation forming a conductive path between the tape and the head surface, which would create a pathway for electrochemical corrosion of the recording head structures.

[0082] The weak magnetic property reduces the amount of noise contributed by the magnetic fields emanating from the sublayer 1006 and improves the resolution of the written bits in the recording layer above the sublayer.

[0083] In approaches where the 1006 underlayer has a conventional structure and typically uses micron-sized particles with low coercivity and low moment, the coating is not optimized for high loading with very small particles (in the nanoscale). In some approaches, the underlayer is made with a weakly magnetic iron oxide using a conventional rubber-like polyester polyurethane resin with a poly(vinyl acetate-vinyl alcohol-vinyl chloride) hard 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 signal recording layer above it in the finished tape.

[0084] In preferred approaches, the sublayer 1006 has a new composition in which the sublayer 1006 comprises particles 1010 that are weakly magnetic but also electrically conductive and dispersed in a low-stress UV-cured matrix, which ensures good adhesion to the substrate and provides mechanical stability and strain relief for the very thin recording layer above it.

[0085] The sublayer 1006 does not need to exhibit a narrow distribution of nanoparticle sizes in different approaches, although the use of smaller particles improves the surface roughness offered to the recording layer during deposition. When using the novel manufacturing processes described here, the sublayer 1006 is not attacked (caused to swell by the recording layer during deposition).

[0086] 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.

[0087] The mean 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 the range of about 40–75 vol%, in the range of about 45–75 vol%, in the range of about 50–75 vol%, in the range of about 35–50 vol%, in the range of about 40–60 vol%, or any other subrange within the aforementioned ranges. Ideally, the mean 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, durable coating.For coatings containing nanoparticles, a very large surface area can dramatically reduce the CPVC unless a novel encapsulation of the nanoparticles and binder design are implemented that enables a higher CPVC. The CPVC can be determined using dynamic mechanical analysis (DMA) of free films of the coating on a range of coatings with increasing vol% of filler. Conventional DMA techniques can be used for the novel compositions described here. The CPVC is determined at the vol% where the tensile storage modulus (E') reaches its maximum value. Fig. Figure 11 shows a graphical CPVC-DMA representation 1100 for different vol% of pigment in a sublayer according to various approaches. Such a graphical representation 1100 is an example of a graphical representation (graphical representations) that can be produced by persons skilled in the art following the teachings presented here and using conventional DMA representation techniques and without resorting to excessive experimentation.

[0088] The magnetic nanoparticles preferably consist of 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 exhibit a medium magnetic field strength that contributes a minimal signal when reading the overlying recording layer. Ideally, the final coating shows no detectable noise signal contribution to the observed response of the written bits in the data storage layer.

[0089] In preferred approaches, the magnetic nanoparticles exhibit a coercivity (H c The magnetic field strength of the nanoparticles is less than approximately 200 Oe, preferably less than 100 Oe and more than 50 Oe. An exemplary range of the field strength 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.

[0090] 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 feature one or more magnetic metal particles with an oxidized outer surface, or (at the expense of conductivity) oxides such as cobalt, nickel, or iron, and alloys thereof.

[0091] Depending on the material, the mean diameter of the magnetic nanoparticles is preferably in the range of 2 nanometers (nm) to 20 nm, more preferably 4 nm to 10 nm, although the mean diameter could be larger or smaller than this range in some approaches. One consideration regarding the mean diameter is that the smaller the size, the more difficult it may be for the binder to properly retain the pigments in the coating matrix. Accordingly, the mean diameter of the magnetic nanoparticles should be chosen such that the critical pigment volume is kept within an acceptable range. If the mean diameter is too small, there may be insufficient binder between adjacent particles, making the material brittle and prone to breakage.If the particles are too large, the transition between the sublayer 1006 and the recording layer 1008 loses the desired smoothness property described here.

[0092] In preferred approaches, the magnetic nanoparticles present in the sublayer are weakly magnetic and electrically conductive and are composed such that they result in a dried coating with negligible or no swelling caused by the solvent used to deposit the recording layer. The use of nanoparticles in the sublayer is preferred over the use of larger particles to enable a more uniform transition to the recording layer.

[0093] The encapsulated nanoparticles can exhibit a wide size distribution in various preferred implementations, as long as the resulting dried film does not exceed the critical pigment volume concentration.

[0094] Preferably, the majority of the particles in the sublayer 1006 are coated with sufficient binder to achieve a cohesive and stable coating with a minimal number of coated particle clumps or aggregates. The ideal coating would exhibit no clumps or aggregates in the final coating, such that nearly 100% of the particles are completely dispersed as individual particles in the binder matrix. Good particle dispersion in the matrix with minimal particle alignment further reduces the sublayer's contribution to noise in the signal recorded in the recording layer.

[0095] Similarly, the encapsulated nanoparticles are preferably not well aligned to one another, but are, for example, randomly aligned in sublayer 1006. This further improves the performance of the sublayer by reducing the formation of ordered magnetic regions in sublayer 1006, thereby reducing the noise generated in sublayer 1006. Nevertheless, although it is desirable to create a monodisperse, non-aggregated dispersion of encapsulated particles for the coating composition, it is not necessary for the sublayer, since the mechanical properties are more important than the magnetic signal performance.

[0096] The aromatic polymer encapsulating the magnetic nanoparticles can be one of numerous different aromatic polymers and / or comprise several different aromatic polymers, provided that 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.

[0097] The layer encapsulating the nanoparticles can be as thin as a monomolecular layer of, 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 within the coating decreases. This is not as critical in the sublayer as it is in the recording layer.

[0098] The average thickness of the aromatic polymer encapsulating the magnetic nanoparticles is preferably in the range of approximately 0.5 nm to approximately 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 here generally refer to the deposition thickness on the underlying structure, unless otherwise specified.

[0099] Aromatic polymers are preferred as encapsulation layers due to their aromatic ring structure, which encapsulates the surface of the magnetic nanoparticle. Aromatic rings exhibit highly advantageous behavior, particularly with chemically reactive metal oxides such as chromium oxide, because of the unique aromaticity of such molecules, which provides enhanced stability and, when correctly aligned with the magnetic axes of the magnetic nanoparticles, a degree of magnetic shielding at the surface of the magnetic nanoparticles. Due to their unique molecular electronic structure and their ability to moderate an external magnetic field, the aromatic ring structures can, for example, act as magnetic field modifiers.

[0100] Aromatic polymers also provide magnetic shielding on the surface of the pigment and help to isolate the magnetic nanoparticles from other particles, improving the independent switching of the encapsulated nanoparticles, which leads to a higher bit resolution.

[0101] A preferred aromatic polymer is a carbamate. A preferred example of an aromatic molecule known to react with chromium dioxide particles in such a way as 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 consists of methylenebisdiphenylcarbamate with a functional acrylic polyester as the ester segment of the aromatic carbamate. Upon UV irradiation, polymerization can occur to generate the encapsulating polymer film layer on the particle surface.

[0102] Particularly for use with magnetic chromium dioxide nanoparticles, the aromatic polymer is preferably an aliphatic-substituted aromatic compound, which, for example, has an oxidizable portion that reacts with chromium, thereby aiding in the adsorption of the aromatic polymer to the chromium dioxide microparticle. The benzylic carbon of the diphenylmethane dicarbamate is known to oxidize efficiently by chromium dioxide, thereby effectively binding the resulting diphenyl ketone to the particle surface.

[0103] In other approaches, the aromatic polymer features reactive functional substituents such as amines, alcohols, carboxylic acids, or nitrile groups. Cinnamic acid is one example, present as a copolymer with styrene to form a bonded polymer layer on the nanoparticle surface.

[0104] In other approaches, the aromatic polymer has one or more repeating units with substituents suitable for chemical adsorption and / or binding to the particle surface, such as amines, a carboxylic acid like cinnamic acid, and other functional aromatics that bind to the surface of the magnetic nanoparticle used.

[0105] In an alternative implementation, the encapsulation layer of the encapsulated microparticles does not consist of a fully aromatic polymer, but can be a copolymer such as a polyester polyurethane or an acrylic-modified polyurethane. Examples include aliphatic polymers of a known type, non-aromatic polymers of a known type, etc.

[0106] The polymeric binder that binds the encapsulated nanoparticles together can be a binder material of different types. In preferred formulations, 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 include components such as methyl methacrylate, acrylic acid, and others, depending on the formulation. In general, preferred polymeric binders are those with a number-average molecular weight of less than approximately 2400 and preferably less than approximately 1200.

[0107] In a preferred implementation, the polymeric binder, enabling bonding to the encapsulation layer of the encapsulated microparticles, exhibits UV curability. This functionality can be provided by acrylate groups, vinyl, etc.

[0108] 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 coatings coated with nanoparticles, the polymers have a much lower molecular weight (a much smaller size) than the materials used previously. Typically, the usable polymers have a length of fewer than 20 repeat units before UV curing.

[0109] The relative amounts of encapsulated nanoparticles to binder in the sublayer 1006 should be within a range not exceeding the critical pigment volume concentration (CPVC). Experts, once familiar with the novel compositions described here, could calculate the CPVC using established techniques based on the properties of the materials used, such as the binder, the particle surface area, etc. A general rule of thumb is to use less than approximately 50 vol% pigment (encapsulated nanoparticles) in the sublayer 1006 to maintain the structural integrity of the sublayer 1006, along with its other functions, such as structural stabilization of the magnetic layer, improved tape durability, and ensuring the 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.

[0110] Additional materials such as mobile lubricants and / or stabilizers, used to stabilize the dispersion prior to application and hardening, may be present in the sublayer 1006.

[0111] The resulting sublayer 1006 is preferably characterized by a weakly magnetic, electrically conductive, encapsulated nanoparticle dispersion in a binder firmly bonded to the pigment (to the encapsulated nanoparticles), such that a graphical representation of a dried coating with an initial glass transition temperature Tg in the tensile storage module (E') is achieved with respect to the 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 is, for most approaches, between 0°C and 60°C, but it can be higher or lower.

[0112] The binders used in conventional magnetic recording tapes result in a sublayer 1006 with a glass transition temperature of 20–30°C. This is too soft, causing the sublayer 1006 to be too compliant in use to ensure a stable and durable recording medium. However, the sublayer 1006 should be sufficiently elastic to remain robust and durable during use and storage. Accordingly, preferred embodiments provide a sublayer 1006 that has an initial Tg determined by a graphical DMA plot of E' with respect to temperatures above approximately 35°C, wherein the preferred initial Tg remains within the elastic range with a very wide response at 10 Hz up to at least 50°C.

[0113] The average thickness of the underlayer 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 cassette, smaller thicknesses are preferred.

[0114] In preferred formulations, no abrasive particles are present in the sublayer 1006, and ideally, no abrasive particles are present in the product at all. It has been found that abrasive particles, conventionally added for the purpose of cleaning the tape head and / or reducing static friction, represent an increasingly unacceptable defect and a source of damage to the shrinking read and write structures in current and future recording heads. However, in other formulations, abrasive particles may be present in the sublayer 1006.

[0115] The sublayer 1006 is preferably at least partially dried to minimize layer mixing and is cured before being applied to the substrate 1004 prior to the application of the magnetic recording layer 1008. Accordingly, in preferred formulations, the recording layer 1008 does not mix with the sublayer 1006 (and vice versa). This feature solves a long-standing problem in magnetic recording tape products.

[0116] Referring to Fig. Figure 12 shows a TEM image of a cross-section of a conventional 1200 recording tape. As shown, the transition between the recording layer and the underlying sublayer 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, gaps are present where no particles are found. In addition, the transition from the recording layer to the sublayer is relatively rough. Ideally, magnetic fields from a recording device pass through the recording layer perfectly perpendicularly. Unfortunately, magnetic fields expand or bend upon exiting the recording device, with the bending being more pronounced the further they are from the pole end of the recording device.The gaps, the wavy transition between the recording layer and the sublayer, and the uneven dispersion of the magnetic particles all amplify the effects of the expanding magnetic field of the writing device. Where a transition is written (e.g., the recording area facing down, then up 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, thus reducing the tape's resolution. On reverse playback, the transition is noisy because it is not sharp. An improvement of 1 dB in the signal-to-noise ratio (SNR) on reverse playback is a significant achievement.The inventor believes that by using the new and novel recording layer described here, which is produced on a hardened sublayer, thereby minimizing the mixing of the layers, an improvement in the signal-to-noise ratio (SNR) during back-reading of up to 5 or 6 dB can be achieved.

[0117] In preferred approaches, the upper surface of the sublayer is essentially flat with a modulation of less than about 25%, preferably less than about 5%, of the thickness of the transition boundary as seen in the TEM cross-section of the finished strip coating, such as the upper surface of the Fig. 12 recording layer shown. Process for manufacturing the lower layer

[0118] A method for manufacturing sublayer 1006, e.g., of a magnetic recording medium, according to various approaches, is presented below. As one option, the present method can be implemented to generate sublayers 1006 as described above. Of course, this and other methods presented here can be used to generate sublayers 1006 that may be related to the exemplary aspects listed here, but need not be. Furthermore, the methods presented here can be executed in any desired environment. In addition, more or fewer operations than those described below can be included in the method, depending on the approach. It should also be noted that each of the features listed above can be used in each of the approaches described according to the different methods.

[0119] The process generally comprises the production of a sublayer 1006 containing encapsulated nanoparticles, each having at least one magnetic nanoparticle encapsulated by an aromatic polymer, and a polymeric binder that binds the encapsulated nanoparticles.

[0120] Encapsulated nanoparticles can be purchased or manufactured. For example, some approaches may utilize commercially available encapsulated nanoparticles suitable for medical imaging and drug delivery applications.

[0121] In one approach, the production of 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 preceding section. The mixing includes, for example, ultrasonic dispersion of the encapsulated nanoparticles in the polymeric binder and the solvent, thereby creating a radiation-curable emulsion in the solvent.

[0122] 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 advanced ribbon structure presented here. Therefore, the compositions described here are unsuitable for conventional coating. All of the examples are best applied to the substrate as a sprayed aerosol coating, although other coating methods are being considered.

[0123] In general, the solvent used here should possess one or more, and preferably all, of the following properties: the solvent causes the polymeric binder to swell, but allows the polymers to collapse around the pigment instead of shrinking upon drying. The solvent causes the polymeric binder chain to uncoil and move towards its theta state (minimal free volume).

[0124] 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 due to the speed at which curing takes place when the polymeric binder is close to its theta state.

[0125] One of the solvent components should be a good solvent for the binder additive and helps to suspend the polymer-encapsulated magnetic particles. The second solvent can be a non-solvent for the polymer binder. As the phase of the "good" solvent evaporates, the remaining coating moves closer to a non-solvent-dominated coalescing coating. The coating rich in the second solvent 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 any waviness or rippling in the finished ribbon.

[0126] A preferred solvent is a water and tetrahydrofuran solvent system (THF solvent system) in relative concentrations that render the solvent system nearly 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, upon drying, the THF disappears first, followed by the water, which helps to keep the binder moving toward the theta state. In particular, the THF disappears first due to its higher volatility compared to water. The fact that the organic solvent disappears first allows the coalescence of the film to collapse and reduces the stress. The water then dominates the solvent transition, allowing the polymer to approach the theta state.

[0127] Only a slight increase in the water content compared to the azeotropic mixture concentrations (e.g., 6.7% by mass) is required to ensure optimal coating drying. This results in a solvent mixture of 7–8% water in 92–93% THF, which dries at 64°C. This lower drying temperature has the added benefit of reducing operating costs compared to current magnetic tape coating processes.

[0128] The resulting mixture (pigment + solvent) is applied to a structure such as substrate 1004. Any suitable application technique can be used. If the pigment and solvent mixture forms an emulsion, spray coating is a preferred technique, as it ensures rapid, uniform application without the streaks typical of brush coating or the lumps typical of blade coating. Other application techniques include blade coating, slot nozzle coating, the use of gravure rollers, etc.

[0129] In another approach, the generation of the sublayer 1006 involves mixing the polymeric binder with the encapsulated nanoparticles to create a microsuspension without the addition of dispersants or other additives to produce a stable dispersion.

[0130] The applied mixture is dried to remove at least some of the solvent or substantially all of it. 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 an 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, thus forcing the hydrophobic binder to collapse onto the pigments. This also minimizes residual stress in the dry coating, preventing issues such as ribbon wrinkling.Drying is preferably carried out using compressed air under low temperature conditions (less than about 75 °C).

[0131] The partially dried coating, which ultimately forms the substrate for the magnetic recording layer, can be cured, for example, using a thermally induced chemical reaction to harden the two layers, a radiation-induced chemical reaction to harden the two layers, etc. For instance, UV light or another known irradiation is used to induce cross-linking of the polymeric binder. If the correct solvent is selected for both coatings, the curing step results in minimal stress between the two layers and a stable (flat) coating.

[0132] In the case of thermally induced curing, a chemical reaction can be used to reduce solvent swelling in the coating and to 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 dense coating. The preferred approach is the use of 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 generally known that ultraviolet radiation (UV radiation) can activate the formation of free radicals, which can attack unsaturated carbon compounds such as olefins, vinyls, and acrylates, thereby initiating polymerization of these reactive species and generating more stable molecular structures. UV curing is also preferred because, during the formation of free radicals, the underlayer 1006 can also bind to some substrates 1004, thus improving the durability of the tape.

[0133] After the base layer 1006 has been hardened, a magnetic recording layer 1008 is produced on or over the base layer 1006. Drying and hardening the base layer 1006 before producing the magnetic recording layer 1008 of any type on top of it minimizes the mixing of the layers at the interface between the base layer and the recording layer. This eliminates a problem that was widespread in the manufacture of conventional magnetic recording tapes and led to a limitation of the achievable area-specific recording density of the tape.

[0134] 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 linked together with a functional acrylic polymer. A composition of the above materials is dispersed into an ultraviolet-curable (UV-curable) emulsion in a tetrahydrofuran (THF) and water solvent system using an ultrasonic dispersion process, applied to substrate 1004, dried, and cured.The dried coating contains the pigment encapsulated by the aromatic glassy polymer in such a way that the matrix is ​​highly populated with over 40% of the magnetic and electrically conductive pigment, maintaining an elastic, rubbery interparticle matrix formed from the polyester acrylate domains of the carbamate binder. Process for manufacturing encapsulated magnetic nanoparticles

[0135] In different approaches, the magnetic starting nanoparticles, which are later encapsulated using one of the novel processes disclosed herein, are produced using known techniques, e.g., milling. In other approaches, the magnetic starting particles are obtained in ready-to-use form and encapsulated using one of the novel processes disclosed herein.

[0136] The production of encapsulated magnetic nanoparticles can be carried out using various techniques. Previous approaches to encapsulating magnetic nanoparticles have proven unsuccessful. Instead of attempting to maintain the isolation of the precursors of the encapsulated nanoparticles (which have not yet been 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 on 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 then heated using ultrasonic dispersion energy to maintain the suspension.A high-boiling aromatic hydrocarbon such as anthracene, phenanthrene, pyrene, etc., is added to an approximate volume of toluene prior to distillation. The mixture is heated above the boiling point of toluene, and the distilled-off toluene leaves behind a molten suspension of the dispersed nanoparticles in a fully aromatic polyaromatic melt, similar to molten phenanthrene, which melts above 380 °C.

[0137] In one exemplary approach, the mixture is heated in a pressure vessel to raise the temperature to 400 °C and maintain it 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 fully enclosed in an aromatic shell.

[0138] 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 re-disperse the nanoparticles in the mixed aromatic solvents. Sufficient chloroform or a similar solvent is then added to allow separation and decantation of the aromatic layer from the particles suspended in the chloroform.

[0139] Dry particles can be recovered to produce an emulsion by distillation of the chloroform or a suspension obtained by solvent exchange to water, provided that the aromatic encapsulation layer is modified to exhibit sufficient residual polar functionality to enable stable dispersion in water. Recording layer

[0140] In some approaches, the recording layer 1008 has a new and novel structure. In one aspect, the new and novel recording layer 1008 can be located on the medium 1000 with a conventional sublayer 1006 underneath. In another aspect, the new and novel recording layer 1008 can be located on the medium 1000 with a new and novel sublayer 1006 underneath. In still other approaches, the recording layer 1008 has a conventional structure and is located on the medium 1000 with a new and novel sublayer 1006 underneath.

[0141] In approaches where the recording layer 1008 has a conventional structure, a dispersion of weakly magnetic particles dispersed in a binder system that does not attempt to encapsulate the particles in a glass-like encapsulation layer prior to dispersion 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 be added to these sublayers to improve conductivity or abrasion resistance, but this is not necessary.

[0142] In preferred approaches, the recording layer 1008 has a novel composition in which the recording layer 1008 comprises encapsulated nanoparticles 1018, each containing at least one magnetic nanoparticle 1020 and preferably only a single magnetic nanoparticle 1020, which is 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 considerably higher than the magnetic strength of the nanoparticles in the sublayer 1006, if present.

[0143] A mean concentration of the encapsulated nanoparticles in the recording layer 1008 is preferably at least about 35 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 aforementioned ranges.

[0144] 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 suitable for magnetic imaging, magnetic materials usable as magnetic nanoparticles can be employed. In various 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, for which combinations of nickel, cobalt, and iron such as iron-barium, NiFe, barium ferrite, and cobalt-platinum are used.

[0145] It should be noted that the approach described here is applicable to other nanoparticles, such as MnAl, which are not currently typically used for tape storage layers, and even to non-magnetic dispersions that could benefit from improved control of coating integrity, such as SiC and SiO2 dispersions, which are useful for sandpaper and other abrasives. Accordingly, any known type of magnetic nanoparticle can be used in different approaches.

[0146] 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 other approaches, the magnetic nanoparticles may comprise manganese-aluminum alloys, oxides of magnetic metals, and Pinel ferrites.

[0147] The mean diameter of the magnetic nanoparticles in the recording layer 1008 is preferably in the range of about 2 nm to about 20 nm, more preferably in the range of about 2 nm to about 10 nm, particularly for the epsilon iron oxide particles. The mean diameter can be larger or smaller than this range depending on the size at which the magnetic nanoparticle loses its remanence and becomes superparamagnetic. Generally, a smaller mean diameter is preferable for increasing the bit resolution.

[0148] Preferably, to optimize the final response of the recording layer to an external field applied during data writing, the encapsulated nanoparticles used for the recording layer 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%, and 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.

[0149] The aromatic polymer encapsulating the magnetic nanoparticles can be any of numerous different aromatic polymers and / or comprise several different aromatic polymers, provided that in the sublayer 1006, and particularly to optimize the magnetic nanoparticles in the recording layer, the aromatic polymer encapsulates at least approximately 75% of the surface area of ​​the magnetic nanoparticle, preferably at least approximately 90% of the surface area of ​​the magnetic nanoparticle, and ideally approximately 100% of the magnetic nanoparticle. In the recording layer, the particle encapsulation effectiveness 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 completed recording layer 1008 is preferably less than 1 nm. Preferably, the average thickness of the aromatic polymer shell is in the range of approximately 0.5 nm to approximately 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, clumps or aggregates of partially coated nanoparticles may form during the encapsulation process and may persist in the final coating beyond the initial application process. As long as these clumps and aggregates do not constitute a significant proportion of the coating (e.g., less than 10% by volume) and are smaller than the thickness of the final coating, they do not cause surface roughness or defects (e.g.,(having a diameter of < 60% of the thickness of the final dried coating), the presence of accumulations and aggregates should not restrict the desired functionality of the layer.

[0150] In embodiments where the encapsulated nanoparticles are pyrolyzed, the average thickness of the resulting carbon shell is in the range of approximately 0.05 nm to approximately 1 nm.

[0151] Such thin shells improve the packing density of the magnetic particles in the recording layer 1008 and thus enable a higher recording bit resolution.

[0152] Aromatic structures are preferred as encapsulation layers for isolating magnetic nanoparticles due to their unique electronic properties, which ensure a weak but essential separation of each nanoparticle from the magnetic field that couples it to its close neighbors in the final, densely packed, dry coating.

[0153] The aromatic polymer preferably comprises functional groups exhibiting 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.

[0154] 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 rubber-like polymer chain in the paraposition to the styrene monomer. Preferably, the encapsulation layer comprises a polyaromatic film.

[0155] In other approaches, the aromatic polymer is a known precursor used to produce graphite, carbon fiber, carbon nanotubes, etc. Accordingly, the encapsulation layer can be a graphite-dominated, continuous film.

[0156] The polymeric binder that binds the encapsulated nanoparticles together can comprise and / or consist of different types of binder material.

[0157] Previous approaches considered involved incorporating encapsulated magnetic nanoparticles into conventional binder systems; however, such approaches were found to produce recording layers with significantly more noise and considerably lower signal performance than would be expected 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 found that the novel techniques described here produce a new recording layer exhibiting excellent recording performance, far superior to approaches using conventional binder systems.

[0158] In preferred formulations, 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 formulations, the polymeric binder contains a radiation-cured, rubber-like acrylic polymer. Exemplary acrylic polymers suitable for use as binders include, in different formulations, acrylic-terminated polyester and those containing components such as methyl methacrylate, acrylic acid, and others. The binder may, for example, contain an acrylic-terminated aliphatic polyester or an aliphatic polyether polymer. In general, preferred polymeric binders are those with a number-average molecular weight of less than about 2400 and preferably less than about 1200.

[0159] The binder used in the recording layer 1008 can be the same as, or different from, the binder used in the sublayer 1006, depending on the approach.

[0160] The recording layer 1008 should be flexible (rubber-like) over the operating temperature range, while simultaneously offering tear and impact resistance. Accordingly, preferred embodiments provide a recording layer 1008 that has a glass transition temperature of above approximately 35°C, preferably above approximately 45°C, and ideally at least approximately 50°C. This can be achieved by selecting the appropriate binder.

[0161] Additional materials such as lubricants may be present in the recording layer 1008. However, an advantage of the various approaches disclosed here is that they allow the elimination of conventional additives such as abrasive particles in the recording layer.

[0162] The mean thickness of the recording layer 1008, measured perpendicular to the plane of its production, 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, thus ensuring rapid, continuous curing of the entire layer. Conventional recording layers, which are thicker, could not be UV-cured and therefore relied on other, slower curing methods. Accordingly, in the production of the conventional tape, curing continued while the tape was being wound onto a reel. However, winding the tape onto the reel created tensile stresses and other stresses (e.g.,a radial compression) throughout the entire band, resulting in changes in the mechanical properties of the band that differed from the band inside at the center to the band outside the center.

[0163] If the recording layer 1008 is produced directly on a sublayer 1006, the recording layer 1008 is preferably applied after the sublayer 1006 has been hardened to minimize mixing of the layers. Accordingly, in preferred approaches, the recording layer 1008 does not essentially mix with the sublayer 1006 (and vice versa).

[0164] Preferably, the sublayer 1006 has a total magnetic field strength in Oe of less than 200 Oe and preferably less than 100 Oe. The sublayer 1006 may have a similar structure and / or similar properties to the sublayers disclosed elsewhere herein.

[0165] In some aspects, lubricant molecules 1030 are coupled to a surface of the recording layer 1008. The lubricant molecules can be bound to the surface, embedded in the surface, or both. Preferably, the amount of lubricant molecules along the surface of the recording layer 1008 is less than an amount that would form a continuous lubricant film along the surface of the recording layer 1008.

[0166] In preferred approaches, no abrasive particles are present in the recording layer 1008, and ideally, no abrasive particles are present in the product at all. However, in other approaches, abrasive particles may be present in the recording layer 1008 and / or pass through from a sublayer 1006. It is expected that the aforementioned mechanical design of the recording layer 1008 with an electrically conductive sublayer 1006 will achieve the desired low friction and head corrosion properties of the tape surface without the need to incorporate abrasive particles, which represent an increasingly unacceptable deficiency and a source of damage to the shrinking read and write structures in current and future recording heads. Process for manufacturing the recording layer

[0167] A method for fabricating the recording layer 1008, e.g., of a magnetic recording medium, according to different approaches, is presented below. As one option, the present method for fabricating recording layers 1008 can be implemented as described above. Of course, this method and others presented here can be used to fabricate recording layers 1008 that may be related to the exemplary aspects listed here, but need not be. Furthermore, the methods presented here can be carried out in any desired environment. In addition, more or fewer operations than those described below can be included in the method, depending on the approach.It should also be noted that each of the aforementioned features can be used in each of the approaches described in connection with the different procedures.

[0168] The process generally comprises the production of a magnetic recording layer 1008, which includes encapsulated nanoparticles, each having at least one magnetic nanoparticle encapsulated by an aromatic polymer, and a polymeric binder that binds the encapsulated nanoparticles.

[0169] In one approach, the creation of 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 within the aromatic polymer. Generally, for most aromatic polymers, the temperature ranges from approximately 200 degrees Celsius to approximately 538 degrees Celsius, depending on the specific aromatic polymer used.

[0170] 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 preceding section and to avoid the formation of nanoparticle aggregates.

[0171] 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 towards an emulsion.

[0172] In some approaches, the encapsulated particles are pyrolyzed, resulting in a magnetic nanoparticle encapsulated in a carbon shell.

[0173] The warm suspension of magnetic nanoparticles and aromatic polymer is mixed with a polymeric binder and a solvent to create a mixture. Preferably, ultrasonic dispersion is used to generate an emulsion. This technique for synthesizing encapsulated nanoparticles and polymer encapsulation advantageously eliminates the need for milling and redispersion from aggregated particle clusters, which is typical in conventional manufacturing techniques.

[0174] 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 upon drying the solution passes through theta states of this binder and forces the binder to collapse around the pigment, rather than shrinking upon drying, which results in undesirable tension in the finished coating.The final solvent, which evaporates during drying and is a non-solvent for the binder, forces the swollen chains to coil up into their minimal free volume state, known as the theta state, as they transition from being well solvated by the initial solvent to being enveloped by a non-solvent-rich environment during 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 because of the speed at which curing takes place when the polymeric binder is close to its theta state.

[0175] A preferred solvent is a water-THF solvent system in relative concentrations that make the solvent system predominantly azeotropic, with a slight excess of water to force the final drying coating to pass through theta states during drying. The THF evaporates first due to its higher volatility than water. This initial evaporation of the organic solvent allows the film coalescence to collapse and reduces stress. The water then dominates the solvent transition, enabling the polymer to approach theta states.

[0176] In other approaches, the system can be water-dominated, resulting in a true emulsion coating. The absorbed binder acts as an emulsifier, ensuring the rubber-phase resin remains in the final coating. In further 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.

[0177] The resulting emulsion / solvent is applied to a structure such as the aforementioned sublayer 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 streaking or thickness variations typical of brush coatings and without the modulation of transitions that result from high-shear blade coating or die-casting processes in these very thin coatings.

[0178] The applied mixture is partially or substantially completely dried to remove at least some of the solvent. As the solvent is removed during drying, the polymeric binder collapses onto the encapsulated microparticles. In the case of a hydrophobic binder, the last solvent to disappear from the applied mixture, such as water, is non-solvent for the binder, thus forcing the hydrophobic binder to collapse onto the pigments. This also minimizes residual stress in the dry coating. Drying is preferably carried out using compressed air under low-temperature conditions (less than approximately 75 °C).

[0179] The applied mixture, at least partially dried, is cured to limit further expansion or contraction in the stress-free layers during subsequent processing and exposure to environmental influences, in order to create a thin, high-density recording layer 1008 with densely packed magnetic nanoparticles. In one approach, the applied mixture, at least partially dried, is irradiated. For example, UV light or another known irradiation method is used to induce cross-linking of the polymeric binder. In another approach, a different curing process, such as heating, is carried out to enhance the reaction of thermally reactive functional groups in the encapsulated nanoparticle layer with the rubber-like binder phase of the dried film.

[0180] As an option, a lubricant can be added during the production of the recording layer 1008, wherein the lubricant molecules 1030 are ultimately coupled to a surface of the recording layer 1008 during its production. The lubricant molecules can be bound to the surface, embedded in the surface, or both. Again, the amount of lubricant molecules along the surface of the recording layer 1008 is preferably less than the amount required to produce 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, at a distance in the range of about 2 to about 15 molecular radii.

[0181] In one approach, lubricant molecules 1030 are dispersed in the organic solvent phase and transported to the surface during drying. During hardening, they are grafted onto the surface in such a way that they form a stable, low-friction layer without any movement of the lubricant molecules to the bearing and head surfaces. This, in turn, reduces head contamination.

[0182] In other approaches, a lubricant is applied to the outer surface of the completed recording layer 1008.

[0183] In an illustrative example, a predominantly monodisperse suspension of aromatic polymer-encapsulated magnetic nanoparticles such as Co3O4, CoFe, Fe3O4, or Co(fcc) is combined with a rubber-like polymer having radiation-curable end groups and side chains of sufficient chain length to ensure a rubber-like phase upon bonding to the radiation-curable end groups on the aromatic encapsulation layers of the dispersed nanoparticles during curing. The resulting suspension is used to create a densely packed, thin recording layer 1008 in which a high-density recording can be made.The rubber-like chain associated with the aromatic encapsulation layer terminates in a functional acrylic or methacrylic group. This group 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 coherent coating by swelling of the rubber-like phase. For example, a low molecular weight, acrylic-terminated polyester added to the solvent can be used. UV curing of the solvent-swelled coating and the polyester occurs during drying.

[0184] Compared to current magnetic recording media, the advantages of a magnetic recording tape with the new sublayer and the new recording layer formed on it include, but are not limited to, a thinner recording layer, a more uniform distribution of magnetic particles, a smoother, less obscured transition between the sublayer and the recording layer, a higher glass transition temperature, and a reduced occurrence or near-complete elimination of gaps in the magnetic particles of the recording layer. Each of these advantages results in a magnetic recording tape with properties such as higher dimensional stability, greater tensile strength, higher recording resolution down to and below 1 nm, and lower noise, resulting in a higher signal-to-noise ratio.demonstrates, but is not limited to.

[0185] It becomes 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.

[0186] It is further understood that embodiments of the present invention can be provided in the form of a service provided on behalf of a customer.

[0187] The inventive concepts disclosed herein have been presented by way of several exemplary scenarios, embodiments, and / or implementations to illustrate the multitude of their features. It should be noted that the generally disclosed concepts are to be considered modular and can be implemented in any combination, implementation, or synthesis thereof. Furthermore, any modification, alteration, or equivalent of the features, functions, and concepts disclosed herein that is obvious to persons skilled in the art upon reading the present descriptions is to be considered to be within the scope of this disclosure.

Claims

[1] Product which features: - a recording layer (1008) which includes: - encapsulated nanoparticles (1010) each comprising exactly one magnetic nanoparticle encapsulated by an aromatic, polymer (1014) based encapsulation layer, and - a polymeric binder (1016) that binds the encapsulated nanoparticles (1010), - a sublayer (1006), wherein the recording layer (1008) is formed on the sublayer (1006), wherein the recording layer (1008) is not physically mixed with the sublayer (1006) in the product, such that an upper surface of the sublayer (1006) is substantially flat, with a modulation of less than 25% of the thickness of an interface between the sublayer (1006) and the recording layer, wherein the sublayer is electrically conductive to assist in the dissipation of a charge in the product, and - wherein the sublayer comprises encapsulated magnetic nanoparticles (1010) with a coercive force of less than 200 Oersted (Oe). [2] The product according to claim 1, wherein the magnetic nanoparticles (1010) comprise at least one magnetic material selected from the group consisting of nickel, cobalt and iron. [3] The product according to claim 1, wherein the magnetic nanoparticles (1010) comprise at least one magnetic material selected from the group consisting of Co3O4, CoFe, Fe2O3, Fe3O4 and Co(fcc). [4] The product according to any of the preceding claims, wherein the mean diameter of the magnetic nanoparticles (1010) is in a range of 2 nanometers to 20 nanometers. [5] The product according to any of the preceding claims, wherein the aromatic polymer (1014) based encapsulation layer (1022) is a graphite-dominated continuous film. [6] The product according to any of the preceding claims, wherein the mean thickness of each encapsulation layer (1022) is less than 1 nanometer. [7] The product according to any of the preceding claims, wherein the polymeric binder (1016) that binds the encapsulated nanoparticles (1010) is a radiation-cured rubber-like acrylic polymer. [8] The product according to any of the preceding claims, wherein the mean thickness of the recording layer (1008) is less than 0.2 microns. [9] The product according to any of the preceding claims, wherein the mean thickness of the recording layer (1008) is less than 0.1 microns. [10] The product according to any of the preceding claims, comprising lubricant molecules (1030) coupled to a surface of the recording layer, wherein an amount of lubricant molecules along the surface of the recording layer (1008) is less than an amount sufficient to form a continuous lubricant film along the surface of the recording layer (1008). [11] The product according to any of the preceding claims, wherein the quantity of lubricant molecules along the surface of the recording layer (1008) is less than the quantity required to produce a continuous lubricant film along the surface of the recording layer (1008). [12] A magnetic recording tape (1000) comprising the product according to any one of the preceding claims. [13] A tape cassette (150) which contains: a case (152); and a magnetic recording tape (1000) according to claim 12, which is at least partially housed in the casing (152). [14] The tape cassette (150) according to claim 13, which has a non-volatile memory coupled to the housing (152).

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