Magnetic recording tape having an elastic substrate

Abstract

One approach to magnetic recording tape includes a substrate comprising polyetheretherketone (PEEK), an underlayer disposed on the substrate, and a recording layer disposed on the underlayer.

Description

[Technical field]

[0001] The present invention relates to magnetic recording media, and more particularly to various configurations of substrates for magnetic recording tape media. [Background technology]

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

[0003] A continuing key goal of the data storage industry is to increase the density of data stored on the media. For tape storage systems, this goal has led to increasing the track and linear bit density on the recording tape, and decreasing the thickness of the magnetic tape media. However, the development of higher performance tape drive systems with smaller footprints has created a variety of challenges, ranging from designing tape head assemblies for use in such systems to dealing with dimensional instability of the tape.

[0004] One challenge that arises with increasing track and data density, and which is increasingly limiting formats, is the dimensional stability of the tape, especially in the lateral direction. Lateral contraction and expansion of the tape are well-known phenomena that arise due to numerous effects, including water absorption, thermal expansion and contraction, etc. As the tape width changes, many undesirable consequences can occur, including overwriting previously written data tracks when performing shingled writing, and the inability to read from data tracks that are no longer aligned with the reader (this is especially prevalent for tracks near the outer edges of the reader array).

[0005] More permanent changes in the lateral dimensions of the media can also occur, such as long-term media creep (also known in the art as "aging"). Long-term media creep tends to occur over time as the tape is wound around the hub of a tape cartridge. Long-term media creep is particularly problematic when dealing with tape dimensional stability issues, because the two ends of the tape exhibit different modes of creep. The inner wrap of the tape located closest to the cartridge hub tends to expand laterally over time due to the compressive stresses placed on the inner wrap by the wrap of tape wound around it. The wrap located closer to the outer diameter of the spool of tape is under less compressive stress, but experiences greater tensile stress, which tends to cause the tape to shrink laterally; i.e., the tape becomes smaller in width over time. Thus, both ends of the tape tend to exhibit opposing lateral dimensional changes.

[0006] Changing tape dimensions can cause various problems. It increases the chances of overwriting a single track during writing. Overwritten data is often unrecoverable. Similarly, if the tape width changes after the desired data has been written, the reader may no longer be positioned over the track that it is supposed to read, which can increase read errors.

[0007] The substrate is typically the thickest layer in a magnetic recording tape and therefore tends to have the greatest effect on the lateral stability of the tape, or stated another way, the substrate tends to dominate the overall laminate tape structure with respect to dimensional changes.

[0008] Current magnetic recording tape substrate materials, such as polyethylene naphthalate (PEN) and aramid, suffer from a variety of problems, such as poor tape dimensional stability (TDS), sensitivity to humidity, poor creep recovery or other shortcomings, or a combination thereof, which render them inadequate to meet the demand for magnetic recording tapes having higher data densities than are currently available on the market.

[0009] Current substrates are reaching the limits of possible modifications to improve the substrate's sensitivity to water and temperature and to solve the problems mentioned above.

[0010] Therefore, there is a need in the art to address the above-mentioned problems. Summary of the Invention

[0011] Viewed from a first aspect, the present invention provides a magnetic recording tape comprising a substrate comprising polyether ether ketone (PEEK), an underlayer over the substrate, and a recording layer over the underlayer.

[0012] Viewed from an additional aspect, the present invention provides a tape cartridge comprising a housing and a magnetic recording tape at least partially contained within the housing, the magnetic recording tape comprising a substrate comprising polyetheretherketone (PEEK), an underlayer over the substrate, and a recording layer over the underlayer.

[0013] Viewed from an additional aspect, the invention provides a method of making a magnetic recording tape, the method comprising bonding an underlayer to a substrate, the substrate comprising polyetheretherketone (PEEK).

[0014] Viewed from an additional aspect, the invention provides a method of manufacturing a magnetic recording tape, the method comprising bonding an underlayer to a substrate comprising polyetheretherketone (PEEK) by radiation-induced grafting, and bonding a recording layer to the underlayer.

[0015] According to one approach, a magnetic recording tape includes a substrate including polyetheretherketone (PEEK), an underlayer disposed on the substrate, and a recording layer disposed on the underlayer.

[0016] Magnetic recording tapes having a PEEK substrate have excellent elasticity for normal tape operation and exhibit stable creep and recovery for normal storage and operating temperatures of about 0° C. to about 60° C. Shrinkage of the PEEK substrate is expected to be less than 1% over a temperature range of 100° C., including the operating range noted above. Such advantages are achieved in a preferred manner where the chain length of the PEEK is greater than about 20, and more preferably where the chain length of the PEEK is about 50 to about 100.

[0017] Magnetic recording tape with a PEEK substrate also has low sensitivity to temperature and humidity throughout its operating range. PEEK is generally hydrophobic, which makes it stable to water. Water absorption is expected to be much less than 1% at 50% relative humidity, which is much lower than aramid, which tends to have a water absorption of about 10% at 50% relative humidity.

[0018] Magnetic recording tapes with PEEK substrates have stable mechanical properties. For example, both the tensile storage (E') modulus and the tensile loss (E"") modulus, measured using dynamic mechanical analysis techniques such as Dynamic Mechanical Thermal Analysis (DMTA) for typical operating and storage environments of the tape media, are lower than substrates of conventional media. In one embodiment, the tensile storage (E') modulus of the substrate, measured by dynamic thermal mechanical analysis, is in the range of about 4 GPa to about 20 GPa.

[0019] An added advantage of PEEK is that the PEEK raw material can be melted without degradation, allowing it to be processed into thin films at temperatures near its melting point without losing its desirable properties.

[0020] In one embodiment, the underlayer is grafted to the substrate, which results in a stronger bond between the layers than traditional bonding techniques, which is advantageous in terms of robustness and resistance to stress.

[0021] Each of the above is important to maintain dimensional stability both during use and during long term storage.

[0022] A tape cartridge according to one embodiment includes a housing and a magnetic recording tape at least partially contained within the housing, the magnetic recording tape having a structure as described above.

[0023] Other aspects and techniques of the present invention will become apparent from the following detailed description, which, when taken in conjunction with the drawings, illustrate by way of example the principles of the invention.

[0024] The invention will now be described, by way of example only, with reference to preferred embodiments illustrated in the following figures. [Brief description of the drawings]

[0025] [Figure 1A] 1 is a schematic diagram of a simplified tape drive system. [Figure 1B] 1 is a schematic diagram of a tape cartridge according to one embodiment of the present invention. [Figure 2A] FIG. 1 is a side view of a flat-lapped, bi-directional, two-module magnetic tape head according to one embodiment of the present invention. [Figure 2B] FIG. 2B is a view of the tape bearing surface taken from line 2B of FIG. 2A. [Figure 2C] FIG. 2C is a detail taken from circle 2C of FIG. 2B. [Diagram 3] FIG. 1 shows a tape layout according to one method. [Figure 4A] FIG. 2 illustrates a hybrid servo pattern written in a dedicated area of ​​a tape medium according to one technique. [Figure 4B] FIG. 1 is a detailed view of a portion of a TBS pattern according to one method. [Figure 5A] FIG. 13 is a partial top view showing the effects of tape expansion and contraction. [Figure 5B] FIG. 13 is a partial top view showing the effects of tape expansion and contraction. [Figure 5C] FIG. 13 is a partial top view showing the effects of tape expansion and contraction. [Figure 6] 1A to 1C are partial cross-sectional views of the basic structure of magnetic recording media according to various techniques. [Figure 7]1 is a graph comparing dynamic mechanical thermal analysis (DMTA) results for tensile storage modulus (E') in gigapascals (GPa) over a temperature range for an example of the current tape substrate with an 8 micron thick PEEK film. [Figure 8] 8 is a graph showing the data from FIG. 7 for a temperature range from 0° C. to 60° C. [Figure 9] 1A-1D illustrate exemplary PEEK according to various techniques. [Figure 10] 1A-1D illustrate exemplary PEEK according to various techniques. [Figure 11] 1A-1D illustrate exemplary PEEK according to various techniques. [Figure 12] 1A-1D illustrate exemplary PEEK according to various techniques. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] The following description is made for the purpose of illustrating the general principles of the present invention and is not intended to limit the inventive concepts described herein, and any particular feature described herein can be used in combination with other features described, in each of the various possible combinations and permutations.

[0027] Unless otherwise defined herein, all terms are to be given their broadest possible interpretation, including the meaning implied from this specification, as well as the meaning understood by a person of ordinary skill in the art and / or defined in dictionaries, scholarly treatises, and the like.

[0028] It should also be noted that, unless expressly stated otherwise, when used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents.

[0029] In the following description, various configurations of substrates that are particularly useful in magnetic recording tape media, as well as methods of forming the substrates and magnetic recording tape media, are disclosed.

[0030] In one general approach, a magnetic recording tape includes a substrate comprising polyetheretherketone (PEEK), an underlayer disposed on the substrate, and a recording layer disposed on the underlayer.

[0031] In another general approach, a tape cartridge includes a housing and a magnetic recording tape at least partially contained within the housing, the magnetic recording tape having a structure as described above.

[0032] Example Operating Environment Figure 1A illustrates a simplified tape drive 100 of a tape-based data storage system that may be used in connection with the present invention. It should be noted that while Figure 1A illustrates one particular embodiment of a tape drive, the techniques described herein may be implemented in connection with any type of tape drive system.

[0033] As shown, a tape supply cartridge 120 and take-up reel 121 are provided to support a tape 122. One or more of these reels may form part of a removable cartridge and do not have to be part of the tape drive 100. A tape drive, such as the tape drive shown in FIG. 1A, may further include a drive motor for driving the tape supply cartridge 120 and take-up reel 121 to move the tape 122 past any type of tape head 126. Such a head may include an array of readers or an array of writers, or both.

[0034] A guide 125 guides the tape 122 across a tape head 126. Such tape head 126 is coupled to a controller 128 via a cable 130. The controller 128 may be or may include a processor and / or any logic for controlling any subsystem of the drive 100. For example, the controller 128 typically controls head functions such as servo following, data writing, data reading, etc. The controller 128 may include at least one servo channel and at least one data channel, each of which includes data flow processing logic configured to process and / or store information to be written to and / or read from the tape 122. The controller 128 may operate under logic known in the art and disclosed herein, and thus may be considered a processor for any of the descriptions of tape drives in various ways contained herein. The controller 128 may be coupled to any type of known memory 136 that may store instructions executable by the controller 128. Additionally, the controller 128 may be configured to perform or control some or all of the methods presented herein, or may be programmable to perform or control them, or both. Thus, the controller 128 may be considered to be configured to perform various operations by, and combinations of, programmed logic in one or more chips, modules, or blocks, or combinations thereof; software, firmware, or other instructions available to one or more processors, or combinations thereof; and the like.

[0035] Cable 130 may include read / write circuitry for transmitting data to be recorded on tape 122 to tape head 126 and for receiving data read from tape 122 by tape head 126. An actuator 132 controls the position of tape head 126 relative to tape 122.

[0036] Additionally, an interface 134 may be provided for communication between tape drive 100 and a host (internal or external) to send and receive data, and for controlling the operation of tape drive 100 and communicating the status of tape drive 100 to the host, all as would be understood by one of ordinary skill in the art.

[0037] FIG. 1B illustrates an exemplary tape cartridge 150, which in various approaches can include any of the configurations of magnetic recording media described herein in the form of a tape. Such a tape cartridge 150 can be used with a system such as the system illustrated in FIG. 1A. As shown, the tape cartridge 150 includes a housing 152, a tape 122 within the housing 152, and an optional non-volatile memory 156 coupled to the housing 152. In some approaches, the non-volatile memory 156 can be embedded inside the housing 152, as illustrated in FIG. 1B. In many approaches, the non-volatile memory 156 can be attached to the inside or outside of the housing 152 without modifying the housing 152. For example, the non-volatile memory can be embedded in an adhesive label 154. In one preferred approach, non-volatile memory 156 may be solid-state memory (e.g., flash memory), a read-only memory (ROM) device, or the like, embedded within or coupled to the inside or outside of tape cartridge 150. This non-volatile memory may be accessed by the tape drive and tape operating software (driver software), or another device, or a combination thereof.

[0038] By way of example, FIG. 2A shows a side view of a flat-wrap bi-directional two-module magnetic tape head 200 that may be implemented in conjunction with the present invention. As shown, the head includes a pair of bases 202, each with a module 204, fixed at a small angle α relative to one another. The bases may be "U-beams" bonded together with an adhesive. Each module 204 includes a substrate 204A and a closure 204B having a thin film portion, commonly referred to as a "gap," in which a reader and / or writer 206 is formed. In use, to read and write data on the tape 208 using the reader and writer, the tape 208 is moved along a media (tape) support surface 209 over the modules 204 as shown. The wrap angle θ of the tape 208 at the edge that rests on and exits the flat media support surface 209 is typically between about 0.1 degrees and about 3 degrees.

[0039] The substrate 204A is typically constructed of a wear-resistant material such as a ceramic. The closure 204B can be made of the same ceramic as the substrate 204A or the same type of ceramic as the substrate 204A.

[0040] The readers and writers can be arranged in a piggyback or merged configuration. An exemplary piggyback configuration has a (magnetically inductive) writer transducer on top of (or underneath) a (magnetically shielded) reader transducer (such as a magnetoresistive reader), with the writer pole and reader shield generally being separate. An exemplary merged configuration has one writer pole and one reader shield in the same physical layer (hence the term "merged"). The readers and writers can also be arranged in an interleaved configuration. Alternatively, each array of a channel can be only readers or only writers. Any of these arrays can include one or more servo track readers for reading servo data on the media.

[0041] Figure 2B shows the tape support surface 209 of one of the modules 204, taken from line 2B of Figure 2A. A typical tape 208 is shown in dashed lines. The module 204 is preferably long enough to support the tape as the head steps between the data bands.

[0042] In this example, the tape 208 includes 4 to 32 data bands, e.g., 16 data bands and 17 servo tracks 210 as shown in FIG. 2B on a 1 / 2 inch wide tape 208. The data bands are defined between the servo tracks 210. Each data band may include several data tracks, e.g., 1024 data tracks (not shown). During a read / write operation, the reader and / or writer 206 is positioned at a specific track location within one of the data bands. An outer reader, sometimes called a servo reader, reads the servo tracks 210. These servo signals are then used to keep the reader and / or writer 206 aligned with a particular set of tracks during a read / write operation.

[0043] FIG. 2C illustrates multiple readers and / or writers 206 formed in gaps 218 on a module 204 in circle 2C of FIG. 2B. As shown, the array of readers and writers 206 includes, for example, 16 writers 214, 16 readers 216, and two servo readers 212, although the number of elements may vary. Exemplary approaches include 8, 16, 32, 40, and 64 active readers and / or writers 206 per array, or an interleaved design having an odd number of readers or writers, such as 17, 25, 33, etc. One exemplary approach includes 32 readers per array and / or 32 writers per array, although the actual number of transducer elements may be greater than 32, for example, 33, 34, etc. This allows the tape to move slower, thereby reducing velocity induced tracking and mechanical difficulties, or allows the tape to perform fewer "wraps" to fill or read the tape, or both. The readers and writers can be arranged in a piggyback configuration as shown in FIG. 2C, but the readers 216 and writers 214 can also be arranged in an interleaved configuration. Alternatively, each array of readers and / or writers 206 can be readers only or writers only, and the array can include one or more servo readers 212. It will be noted from a joint review of FIGS. 2A and 2B-2C that each module 204 can include a complementary set of readers and / or writers 206 for bidirectional reading and writing, read-while-writing capabilities, backward compatibility, etc.

[0044] Timing Based Servo The write and read elements magnetize magnetic regions in the recording layer of the magnetic recording tape to enable the formation of magnetic segment bits that appear as rectangular sections that display increased or decreased magnetic signals when detected by a magnetically sensitive detector, such as a magnetic force microscopic (MFM) detector.

[0045] In order to place the data on separate tracks, real-time position information is required regarding the location of existing written information on the tape to prevent accidental erasure of previously written information. When data is first written to a blank, formatted tape, the position of the first data band must be carefully controlled and recorded to allow subsequent data bands to be accurately positioned so as not to overwrite or corrupt previously written data.

[0046] Modern high density tape formats use a highly accurate servo pattern known to those skilled in the art as a timing-based servo. A description of an exemplary timing-based servo scheme is provided below.

[0047] This track-following servo contains transitions recorded in two or more azimuthal orientations across the width of the servo track. Signal timing derived by reading at any point across the width of a written pattern created on the tape media in a controlled and precise factory formatting operation is used to calculate the position of the magnetic recording head in real time. This pattern is read by a servo reader that has a small width compared to the width of the servo track. The combination of a wide servo pattern and a narrow servo reader provides excellent position sensing linearity and dynamic range.

[0048] Position sensing with a timing-based servo system is achieved by deriving the ratio of two servo pattern spacings and is therefore insensitive to tape speed during readback of the recorded signal. Detection of the center of the servo pattern during tape motion provides a precise reference point for each data band. The difference between the centers of the two servo readers used in each read or write motion of the tape across the recording head is a measure of the spacing between the two servo bands on the tape that was previously recorded during factory formatting. The servo readers are fixed within the head structure but move on the very small nanometer scale due to stress and environmental factors. Thus, the actual positions of the spacing between the servo bands written on the tape move relative to each other, resulting in a change in the actual spacing between data bands that pre-exist or are written over existing data tracks.

[0049] Briefly referring to FIG. 3, an exemplary tape layout according to one approach is shown. As shown, tape 300 has a tape layout implementing five servo bands, namely servo band 0 through servo band 4, and four data bands, namely data band 0 through data band 3, as defined in the LTO (LTO is a trademark of HP. IBM Corp. Quantum) and IBM® Enterprise formats. IBM is a trademark of International Business Machines Corporation, registered in many jurisdictions worldwide. The height H of each servo band is measured in a cross-track direction 304 generally perpendicular to the length L of tape 300. According to one example, the height H of each servo band may be approximately 186 microns according to the LTO format. Additionally, the pitch β between the illustrated servo bands may be approximately 2859 microns, also according to the LTO format.

[0050] Also shown is an exemplary tape head 302 having two modules and disposed over a portion of the tape 300 according to one approach. Read and / or write transducers may be disposed in any of the modules of the tape head 302 according to any approach described herein and may be used to read and / or write data from and / or to the data bands. Additionally, the tape head 302 may include servo readers according to any approach described herein and may be used to read servo patterns in the servo bands. It should also be noted that the dimensions of the various components included in FIG. 3 are provided by way of example only and are in no way intended to limit the invention.

[0051] Some tape drives may be configured to operate at slow tape speeds or nanometer head position settings, or both. These tape drives may target barium ferrite (BaFe) tape media, four or eight data bands, 32 or 64 data channel operation, and use servo formats that allow for very slow speed operation, support large bandwidth actuator operation, and improve parameter estimation to minimize the standard deviation of the position error signal (PES), thereby enabling track density scaling for tape cartridge capacities of 100TB or more.

[0052] However, according to some approaches, magnetic tape can be further enhanced with additional features that provide additional functionality. Accordingly, instead of the standard TBS servo pattern as shown in Figure 3, for example, a HD servo pattern can be implemented. This HD servo pattern can be used to improve track following performance.

[0053] In yet another approach, a standard TBS servo pattern (e.g., as shown in FIG. 3) may be implemented in combination with one or more HD servo patterns (see, e.g., FIG. 4A below). One embodiment includes a hybrid servo pattern scheme in which the standard TBS pattern is maintained and additional HD patterns are provided in a dedicated area of ​​the tape media, preferably an area that is not currently in use. In some approaches, this type of pattern may be implemented by increasing the number of data channels from 16 to 32 and reducing the width of the TBS pattern from 186 microns to 93 microns.

[0054] FIG. 4A shows a hybrid servo pattern 410 including a standard TBS pattern 402 written in a servo band of a tape medium 408 and an HD pattern 404 written in an HD band (e.g., a dedicated area). Furthermore, each HD pattern 404 includes several HD tracks, each HD track having its own periodic waveform. In some approaches, important features of the original TBS pattern 402 are maintained, such as a servo frame structure consisting of four servo bursts including several servo stripes. These servo bursts are written with alternating azimuth angles of the servo stripes of adjacent servo bursts. Other parameters of the conventional servo pattern, such as the height and other geometric dimensions of the servo pattern and the number of servo stripes per burst, can be changed as desired.

[0055] The HD pattern 404 may include periodic waveforms of various frequencies written alternately along the longitudinal axis of the tape in the length direction L. The standard TBS pattern 402 may be used to provide initial identification of the servo bands (e.g., by providing a servo band ID); initial positioning of the head 406 to the appropriate servo position; and initial acquisition of servo channel parameters such as tape speed, head lateral position, head-tape skew, and longitudinal position (LPOS). Additionally, the HD pattern 404 may enable more accurate and more frequent estimation of the servo channel parameters, thereby achieving improved head positioning over a much wider tape speed range, and support for larger bandwidth head actuation. This may enable track density scaling for much larger cartridge capacities, and may further improve data rate scaling with host computer requirements by supporting a wider speed range.

[0056] Referring again to Figure 4A, which shows a tape layout 400 with a hybrid servo pattern 410 according to one approach, in the hybrid servo pattern 410, an HD pattern 404 is written in the space next to a standard TBS pattern 402. According to this approach, since the TBS pattern 402 is used, no quadrature sequence is included, which is the opposite of what happens when a servo function is implemented in a hard disk drive.

[0057] Briefly referring now to FIG. 4B, a detailed view of a portion of a TBS pattern 402 (e.g., a TBS frame) is shown according to one exemplary approach. As shown, a plurality of servo stripes 412 form a servo burst 414, and corresponding pairs of servo bursts 414 form a servo subframe. Thus, the illustrated TBS frame has four servo bursts 414 and two servo subframes. In this approach, the servo bursts 414 in the left servo subframe each have five servo stripes 412, and the servo bursts 414 in the right servo subframe each have four servo stripes 412. The servo stripes 412 in a given servo burst 414 are oriented such that the azimuth gradient of the servo stripes 412, represented by angle α, is the same. Additionally, corresponding pairs of servo bursts 414 have opposite azimuth gradients, thereby forming a chevron-type pattern. The height H and width t of the servo stripes 412 may vary depending on the servo writer used to write the TBS pattern 402. According to one exemplary approach, which is in no way intended to be limiting, the height H may be approximately 186 μm, the angle α may be approximately 6°, and the width t may be approximately 2.1 μm. Additionally, the spacing S between each servo stripe 412 and / or the distance d between servo bursts 414 having the same azimuthal gradient may vary depending on the desired approach. According to one exemplary approach, which is in no way intended to be limiting, the spacing S may be approximately 5 μm and the distance d is approximately 100 μm. As discussed above, transitions through a pattern such as that shown in FIG. 4B allow an estimate of the lateral position of the head to be determined by evaluating the relative timing of pulses generated by a servo reader reading the servo stripes 412 of the servo bursts 414 as they pass over the servo reader.

[0058] Tape Dimensional Stability Issues 5A-5C illustrate the effect of lateral tape expansion and contraction on transducer array position relative to the tape, and are not intended to be limiting of the present invention in any way. FIG. 5A illustrates a transducer array 500 relative to a tape 502, which has a nominal width. As shown, transducers 504 are conveniently aligned with data tracks 506 on the tape 502. However, FIG. 5B illustrates the effect of lateral tape contraction. As shown, the tape contraction causes the data tracks to shrink, resulting in the outermost transducers 505 being positioned along the outer edge of the outer data tracks. Additionally, FIG. 5C illustrates the effect of lateral tape expansion. In this illustration, the tape expansion causes the data tracks to move farther apart, resulting in the outermost transducers 505 being positioned along the inner edge of the outer data tracks. If the lateral contraction of the tape were greater than that shown in Figure 5B, or if the lateral expansion of the tape were greater than that shown in Figure 5C, the outermost transducers 505 would straddle adjacent tracks, causing adjacent tracks to be overwritten during a write operation, or the wrong track to be read back during a read back operation, or both. Additionally, tape skew and lateral shift effects can exacerbate such problems, especially for tapes with a single data track.

[0059] Thus, lateral expansion and contraction of tape is an ongoing challenge in tape development and currently remains a limiting factor in further increasing data density on tape.

[0060] Manufacturing of magnetic recording media and layers thereof FIG. 6 shows a partial cross-sectional view of the basic structure of a magnetic recording medium 600 according to various approaches described herein. This view is not drawn to scale. Optionally, this magnetic recording medium 600 can be implemented with features of other approaches described herein, such as features described with respect to other figures. However, it will be appreciated that such magnetic recording medium 600 and other magnetic recording media presented herein can be used in various applications or permutations or combinations thereof that may or may not be expressly stated in the exemplary approaches described herein. Furthermore, the magnetic recording medium 600 presented herein can be used in any desired environment. The various permutations of the magnetic recording medium 600 disclosed herein have been developed to improve the stability and performance of tape storage media across the environments required for use and storage.

[0061] Unless otherwise stated herein, the various layers of the magnetic recording medium 600 may have conventional structures, designs, or functions, or combinations thereof. In various approaches, new and novel layers may be used in conjunction with conventional layers. In additional approaches, multiple new and novel layers may be used in conjunction with other conventional layers.

[0062] Unless otherwise stated herein, the various layers of the magnetic recording medium 600 may be formed using conventional methods, particularly when each layer has a conventional structure.

[0063] Preferably, magnetic recording medium 600 is a magnetic recording tape, although in other embodiments, magnetic recording medium 600 is a different type of medium that is deformable.

[0064] As shown in Figure 6, there are typically four basic layers in a magnetic recording medium 600. An optional backcoat 602 is disposed along one side (the bottom side in Figure 6) of a substrate 604. An underlayer 606 is disposed along the other side (the top side in Figure 6) of the substrate 604. A recording layer 608 is disposed above the underlayer 606. In various approaches, additional layers of conventional construction may be present in the magnetic recording medium 600.

[0065] Backcourt The backcoat 602 may or may not be present in the magnetic recording medium 600. The backcoat 602 may be made of known materials and may be selected as a material that can be grafted to the substrate 604 by radiation induced grafting. The backcoat 602 is preferably constructed from a material that provides one or more of the following advantages: ease of separation of the tape wound on the backcoat from another section on a spool, improved tribology, dissipation of static electricity, etc. The preferred thickness of the backcoat 602 is less than about 0.3 microns, preferably less than about 0.2 microns.

[0066] Base material The substrate 604 has a new and novel structure as disclosed herein. The substrate 604 is formed of polyetheretherketone (PEEK). As used herein, PEEK refers more broadly to a class of materials collectively known in the art as PEEK materials, including various types of polyaryletherketones (PAEK), polyetheretherketones, and other similar materials.

[0067] Magnetic recording tape with PEEK substrate 604 has stable mechanical properties. For example, both the tensile storage (E') modulus and the tensile loss (E"") modulus, measured using dynamic mechanical analysis techniques such as dynamic mechanical thermal analysis (DMTA), for the normal operating and storage environment of the tape media are lower than conventional media substrates. Generally, the normal operating and storage environment of the tape media ranges from about 0° C. to about 60° C. and a relative humidity of about 5% to about 80%.

[0068] Magnetic recording tape with PEEK substrate 604 also has low sensitivity to temperature and humidity throughout its operating range. PEEK is generally hydrophobic, which makes it stable to water. Water absorption is expected to be much less than 1% at 50% relative humidity, which is much lower than aramid, which tends to have about 10% water absorption at 50% relative humidity.

[0069] Magnetic recording tape having PEEK substrate 604 further has excellent elasticity for normal tape operation and exhibits stable creep and recovery for normal storage and operating temperatures of about 0° C. to about 60° C. Shrinkage of the PEEK substrate is expected to be less than 1% over a temperature range of 100° C., which includes the operating range mentioned above.

[0070] An added advantage of PEEK is that the PEEK raw material can be melted without degradation, allowing it to be processed into thin films at temperatures near its melting point without losing its desirable properties.

[0071] Each of the above is important to maintain dimensional stability both during use and during long term storage.

[0072] PEEK has never been considered a suitable material for use in magnetic recording tape because it has been focused on its use in capacitors and other applications. PEEK has also never been one of the materials used by tape media substrate manufacturers for other applications. Furthermore, the conventional wisdom in attempting to improve the dimensional stability of tape media to address the change in tape width and therefore the stability of data track placement has been to seek an increase in the transverse direction (TD) stiffness or modulus of the substrate. However, in the process, the composition of the conventional substrate must be adjusted to achieve an increase in the substrate's TD modulus. Thus, the inventive findings disclosed herein regarding the use of PEEK as a substrate material go in the opposite direction to conventional wisdom.

[0073] Figure 7 is a graph 700 comparing DMTA results for tensile storage modulus (E') in GPa over a temperature range for example current tape substrates with an 8 micron thick PEEK film from Shin Etsu, Ltd. (DMTA @ 10 Hz). The current tape substrates used in this experiment are TORAY Spaltan™, a blend of polyethylene terephthalate (PET) with chopped modified aramid (Mictron), TORAY Mictron™, a modified aramid, and TD Tensilized PEN from TEIJEN Ltd.

[0074] Graph 800 in FIG. 8 further expands this comparison across the temperature range (0° C. to 60° C.) where tapes are typically used and stored. Only two substrates, Toray Spaltan™ and the PEEK film sample, show a stable mechanical response across this temperature. Toray Spaltan™ was found to show good transverse dimensional stability (TDS). Good TDS is an increasingly important attribute of tapes to enable higher track densities. However, Toray Spaltan™ suffers from sensitivity to humidity and poor creep recovery. The PEEK substrate by various approaches disclosed herein addresses and solves these issues.

[0075] The tensile storage modulus E' of the PEEK substrate according to various embodiments is preferably in the range of about 4 GPa to about 20 GPa, more preferably in the range of about 5 GPa to about 15 GPa, and ideally in the range of about 5.5 GPa to about 12 GPa, preferably towards the upper end of this range. The tensile storage modulus E' can be controlled to some extent by controlling the molecular weight of the PEEK, and potentially improved by increased crystalline chain orientation of higher molecular weight PEEK materials that are not currently available but will become available in light of the teachings presented herein, potentially once the need for them is established for future tape media.

[0076] For the substrate material, in various approaches, PEEK materials are preferred, having an aromatic polyaryletherketone chemical structure and a chain length n of at least n = 20. The chain length is preferably n = 40 or more, such as n = 50 to 100. The chain length should not be so long that the PEEK becomes unworkable or brittle.

[0077] A variety of aromatic polyaryletherketones can be used in a variety of ways that fall within the scope of the present invention. Some exemplary PEEK materials are described below. The descriptions are provided by way of example only, and are not intended to be limiting, to illustrate some of the various types of PEEK that can be used in many aspects of the present invention.

[0078] Referring again to FIG. 6, the substrate 604 may be the thickest layer in the magnetic recording tape. The use of PEEK allows for a thinner substrate than conventional substrates currently in use, thereby allowing for more tape to be spooled into a conventional tape cartridge. In some approaches, the substrate has a thickness measured perpendicular to the plane of the tape of about 2.5 microns or greater, such as a thickness in the range of about 3 microns to about 8 microns, and preferably a thickness in the range of about 3 microns to about 4.5 microns, although the substrate can be thicker or slightly thinner than the upper and lower limits of these ranges.

[0079] Exemplary PEEK Materials FIG. 9 illustrates an exemplary PEEK 900 according to various approaches described herein. Optionally, this PEEK 900 can be implemented with features of other approaches described herein, such as those described with respect to other figures. However, it will be appreciated that such PEEK 900 and other PEEKs presented herein can be used in a variety of applications or permutations or combinations thereof that may or may not be expressly stated in the exemplary approaches described herein. Furthermore, the PEEK 900 presented herein can be used in any desired environment. The various permutations of PEEK 900 disclosed herein improve the stability and performance of tape storage media throughout the required environments of use and storage.

[0080] FIG. 10 shows another exemplary PEEK 1000 according to the various approaches described herein. Optionally, this PEEK 1000 can be implemented with features of other approaches described herein, such as those described with respect to other figures. However, it should be understood that such PEEK 1000 and other PEEKs presented herein can be used in various applications or permutations or combinations thereof that may or may not be expressly stated in the exemplary approaches described herein. Furthermore, the PEEK 1000 presented herein can be used in any desired environment. The various permutations of PEEK 1000 disclosed herein improve the stability and performance of tape storage media throughout the required environments of use and storage.

[0081] Known manufacturing techniques can be used to produce PEEK feedstock that can be used to form substrates. Some approaches use a step growth condensation polymerization reaction.

[0082] FIG. 11 illustrates another exemplary PEEK 1100 according to various approaches described herein. Optionally, this PEEK 1100 can be implemented with features of other approaches described herein, such as those described with respect to other figures. However, it should be understood that such PEEK 1100 and other PEEKs presented herein can be used in various applications or permutations or combinations thereof that may or may not be expressly stated in the exemplary approaches described herein. Furthermore, the PEEK 1100 presented herein can be used in any desired environment. The various permutations of PEEK 1100 disclosed herein improve the stability and performance of tape storage media throughout the required environments of use and storage.

[0083] FIG. 12 shows another exemplary PEEK 1200 and its exemplary formation route according to the various approaches described herein. Optionally, this PEEK 1200 can be implemented with features of other approaches described herein, such as those described with respect to other figures. However, it should be understood that such PEEK 1200 and other PEEKs presented herein can be used in various applications or permutations or combinations thereof that may or may not be expressly stated in the exemplary approaches described herein. Furthermore, the PEEK 1200 presented herein can be used in any desired environment. The various permutations of PEEK 1200 disclosed herein improve the stability and performance of tape storage media throughout the required environments of use and storage.

[0084] As mentioned above, PEEK1200 can be manufactured using a step-growth condensation polymerization reaction. An exemplary step-growth condensation polymerization reaction process shown in Figure 12 involves reacting a diphenyl ether such as diphenyl oxide with terephthalic acid chloride (TPC) in the presence of a metal chloride such as AlCl3 or FeCl3, liberating HCL as a by-product. The reaction is usually carried out in a melt or aromatic hydrocarbon solvent at high temperature so that HCL is released as a gas, leading to a very efficient chain growth reaction.

[0085] The end groups of the PEEK1200 can be similar to those shown in FIG. 9 or other figures.

[0086] In some approaches, PEEK raw material can be purchased commercially from a manufacturer or supplier of PEEK raw material. In a preferred approach, a manufacturer can manufacture suitable PEEK material having desired properties, such as chain length, at the request of a magnetic recording tape manufacturer following the guidelines set forth herein. PEEK is typically sold in pellet form, and the pellets can be processed as described below to form substrates for magnetic recording tapes. In other approaches, PEEK substrate sheets can be manufactured or purchased, or both manufactured and purchased, for use in the tape manufacturing process.

[0087] KETASPIRE® PEEK material is available from Solvay (Solvay Specialty Polymers USA, LLC, 4500 McGinnis Ferry Road, Alpharetta. GA 30005-3914 USA).

[0088] PEEK material is also available from Victrex (Victrex USA, Inc., 300 Conshohocken State Road Suite 120, West Conshohocken, PA, 19428 USA).

[0089] Currently produced PEEK films are not well suited for use as a tape substrate, however, by using the teachings presented herein, one skilled in the art can produce suitable PEEK films having the appropriate thickness, molecular weight, extrudability and molecular orientation for use as a tape substrate.

[0090] PEEK is particularly advantageous for tape applications because it has a very low hygroscopic coefficient of expansion and is insoluble in organic solvents. Thus, PEEK substrates are not susceptible to water-induced dimensional changes. However, PEEK can be melted and formed into films. PEEK does not degrade at the high temperatures used during manufacturing, for example, in melt extrusion. In contrast, aramids used in conventional tape products are modified to be soluble. This is because aramids degrade during melting and cannot be melt extruded into films. To make aramids soluble in very hot polar organic solvents, the aramid chains must be modified to increase solubility. This results in increased water absorption and reduced overall dimensional stability at normal use and storage temperatures of the tape medium.

[0091] To form the substrate, according to one approach, PEEK feedstock is extruded by melt extrusion and oriented to align the crystalline regions of the resulting substrate so that they are generally aligned with one another. The melt extrusion process involves heating the PEEK feedstock to a temperature at which it can be extruded by a melt extrusion apparatus to form a film of a desired thickness. The melt extrusion apparatus and melt extrusion process can be of known design for PEEK materials used in other industries and generally include a die (e.g., nozzle, rollers, etc.) through which the PEEK is extruded and a mechanism for pulling the extruded PEEK. An exemplary substrate manufacturing line may use melt extrusion and a process called tenting, which uses grippers on rails and chain frames that grab the edges of the extruded sheet and pull the sheet laterally and longitudinally through a heated furnace to achieve very controlled MD and TD orientation or tensilization.

[0092] As will be appreciated by those skilled in the art upon learning this description, the temperature used during melt extrusion should be below the degradation temperature of the PEEK feedstock, which varies from material to material and is usually significantly higher than the melting temperature as determined by conventional thermal analysis techniques such as differential scanning calorimetry (DSC) or thermogravimetric analysis (TGA). Typically, PEEK polymers are very stable up to temperatures well above their softening or true melting point. Depending on the molecular structure and chain length of the PEEK polymer, softening occurs at temperatures well above 150°C. For some PEEK polymers, degradation in air can occur when heated to temperatures above 300°C, but 300°C is considered to be well above the effective processing temperature actually used in forming films suitable for magnetic tape substrates. In general, the processing temperatures used in film manufacturing processes are optimized around the specific properties of the polymer feed to the initial extrusion die head to allow good flow and orientation of the initial sheet as it is picked up by the gripper. The grippers then pull the films simultaneously in both the transverse and longitudinal directions of the web to achieve the desired orientation or tensilization of the final cooled film.

[0093] Conventional conditions that align the crystalline domains of conventional substrate films can also be used with PEEK in a manner that would be understood by one of ordinary skill in the art in the knowledge of this disclosure. For example, as molten PEEK is drawn during melt extrusion, the molecular chains tend to align in the direction of flow and toward the smallest free volume. Orienting the film to align the crystalline domains would allow for the production of films with higher modulus and nearly perfect elastic creep recovery without sensitivity to water, which is expected to provide the control of TDS that current tension compensation schemes require.

[0094] The resulting PEEK sheet can be stored for further processing at a later time, or additional layers can be added to the PEEK sheet. In one embodiment, the PEEK sheet is wound onto a spool. In another embodiment, one or more additional layers are added to the PEEK sheet.

[0095] The PEEK sheet with or without the additional layers can be cut to a width required for further processing, or to meet the specifications of the final product, or both. For example, a wide PEEK sheet can be cut into strips of a width suitable for use in conventional coating equipment to add the additional layers to the sheet.

[0096] lower layer According to various approaches, any underlayer 606 known in the art can be used with the PEEK substrate 604. The underlayer 606 can be made of any known material, and is preferably made of a material that can be grafted to the substrate 604 by radiation-induced grafting.

[0097] Recording layer Any recording layer 60 known in the art can be used with the PEEK substrate 604 according to various approaches.

[0098] Exemplary Tape Manufacturing Techniques As will be discussed in more detail below, to manufacture a magnetic recording tape, one or more additional layers, such as an underlayer or a backcoat, or both, are bonded to the PEEK substrate.

[0099] Current magnetic recording tape manufacturing techniques rely on solvent interactions to adhere the layers together or require surface treatments such as plasma cleaning prior to coating. A significant drawback of this surface modification is that the modified substrate is susceptible to water-induced dimensional changes.

[0100] One or more additional layers may also be added to the PEEK film to improve adhesion of coatings or to provide controlled roughness for improved handling, as is currently used in tape substrates. Modification of PEEK films to improve adhesion of coatings, perhaps used to manufacture future magnetic recording tape products, may require modification of the PEEK film surface by co-extruding another film material onto one surface, or by oxidizing one surface using plasma treatment, as is currently done with existing tape substrates. In the case of radiation cured coatings, particularly those for very thin coatings anticipated in future tape designs, sufficient activation of the locations on the PEEK film may be achieved with UV light to solve adhesion problems and eliminate the need for additional surface treatments. Modification of the monomers used to build PEEK specifically optimized for use as a substrate for magnetic media may completely solve any adhesion problems and introduce functional groups into the PEEK film that are activated upon exposure to UV light and can react with functional groups of the coating to further improve the performance of the film for application to magnetic tape media.

[0101] In a preferred approach, one or more additional layers, such as an underlayer or a backcoat, or both, are bonded to the PEEK substrate by radiation-induced grafting, e.g., photoinduced curing (e.g., crosslinking), of these layers to the substrate. For example, an underlayer can be extruded next to the PEEK substrate, laminated onto the PEEK substrate, and grafted to the PEEK substrate in real time by exposure to ultraviolet (UV) light or other radiation, or both. The aromatic compounds in PEEK tend to be photoactive and thus tend to lend themselves to the desired radiation-induced curing. Additionally, as will be appreciated by those of skill in the art upon reading this description, the PEEK feedstock or adjacent layers, or both, can be manufactured to have the desired chemical structure that allows for radiation-induced grafting. In some approaches, no adhesive is present between the underlayer and the substrate.

[0102] However, the degree of cure is not required to be high. The chemical bonds are much stronger than the weak bonding techniques used in conventional tape media, so a few chemical bonds per 100 monomer units are sufficient for good adhesion. The chemical bonds of the preferred embodiment are also advantageous in terms of robustness and resistance to stress, since the chemical bonds must be broken to separate the layers.

[0103] Generally, UV light does not penetrate plastics that are more than 1 micron thick. However, the underlayer used in the preferred procedure is less than 1 micron thick, thus allowing UV curing to occur.

[0104] Various advantages of magnetic recording tapes having the novel PEEK substrate compared to current magnetic recording tape media include, but are not limited to, one or more of: higher dimensional stability, greater tear resistance, greater resistance to the effects of aging (creep), and the like.

[0105] It will be apparent from the foregoing description that various features of the above systems and / or methods can be combined in various ways to produce multiple combinations.

[0106] It will also be appreciated that the techniques of the present invention may be provided in the form of a service that is deployed for customers.

[0107] The ideas of the present invention disclosed herein are presented as examples to illustrate the myriad features thereof in a number of exemplary scenarios, embodiments or implementations, or combinations thereof. It should be understood that the ideas generally disclosed should be considered as modules and can be implemented in any combination, permutation or synthesis thereof. In addition, any changes, modifications or equivalents of the features, functions and ideas disclosed herein that would be understood by a person skilled in the art upon reading the description of this specification should also be considered to be within the scope of this disclosure.

[0108] The description of various embodiments of the present invention is provided for illustrative purposes, and is not intended to be exhaustive or limited to the disclosed embodiments. Many changes and modifications that do not depart from the scope of the described embodiments will be apparent to those skilled in the art. The terms used in this specification are selected to best explain the principles of the embodiments, practical applications, or technical improvements not found in the art on the market, or to enable other skilled in the art to understand the embodiments disclosed herein.

Claims

1. A magnetic recording tape comprising: A substrate including polyetheretherketone (PEEK); an underlayer over the substrate; a recording layer on the lower layer; wherein the chain length of the PEEK is greater than 20; Magnetic recording tape.

2. A magnetic recording tape comprising: A substrate including polyetheretherketone (PEEK); an underlayer over the substrate; a recording layer on the lower layer; The tensile storage modulus of the substrate measured by dynamic thermomechanical analysis is 4 GPa or more. in the range of 0.2 to 20 GPa, Magnetic recording tape.

3. 2. The magnetic recording tape of claim 1, wherein the PEEK has a chain length of 50 to 100.

4. 4. The magnetic recording tape of claim 1, wherein the substrate has a tensile storage modulus in the range of 5.5 GPa to 12 GPa as measured by dynamic thermomechanical analysis.

5. 5. The magnetic recording tape of claim 1, wherein the crystalline domains of the substrate are generally aligned with one another.

6. 6. The magnetic recording tape of claim 1, wherein the thickness of the substrate is in the range of 2.5 to 8 microns.

7. 7. The magnetic recording tape of claim 1, wherein the substrate has a thickness in the range of 3 to 4.5 microns.

8. 8. The magnetic recording tape of claim 1, wherein the underlayer is grafted to the substrate.

9. 9. The magnetic recording tape of claim 1, wherein there is no adhesive between the underlayer and the substrate.

10. 1. A tape cartridge comprising: Housing and a magnetic recording tape at least partially contained within said housing; The magnetic recording tape is the magnetic recording tape according to any one of claims 1 to 9. Tape cartridge.

11. 1. A method for manufacturing a magnetic recording tape, the method comprising bonding an underlayer to a substrate, the substrate comprising polyetheretherketone (PEEK), the PEEK having a chain length greater than 20.

12. 1. A method for manufacturing a magnetic recording tape, the method comprising bonding an underlayer to a substrate, the substrate comprising polyetheretherketone (PEEK), the substrate having a tensile storage modulus in the range of 4 GPa to 20 GPa as measured by dynamic thermomechanical analysis.

13. The method of claim 11 , wherein the PEEK has a chain length of 50 to 100.

14. 14. The method of any of claims 11 to 13, wherein the substrate has a tensile storage modulus in the range of 5.5 GPa to 12 GPa as measured by dynamic thermomechanical analysis.

15. 15. The method of any of claims 11 to 14, wherein the crystalline regions of the substrate are generally aligned with one another.

16. 16. The method of any of claims 11 to 15, wherein the thickness of the substrate is in the range of 2.5 microns to 8 microns.

17. 17. The method of any of claims 11 to 16, wherein the thickness of the substrate is in the range of 3 microns to 4.5 microns.

18. 18. The method of any of claims 11 to 17, wherein no adhesive is present between the underlayer and the substrate.

19. 1. A method for manufacturing a magnetic recording tape, the method comprising: bonding an underlayer to a substrate comprising polyetheretherketone (PEEK) by radiation-induced grafting; and bonding a recording layer to the underlayer.

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