Patent Application
20080030899
For a fuller understanding of aspects and examples disclosed herein, reference is made to the accompanying drawings in the following description.
The following description is presented to enable a person of ordinary skill in the art to make and use various aspects of the inventions. Descriptions of specific materials, techniques, and applications are provided only as examples. Various modifications to the examples described herein will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other examples and applications without departing from the spirit and scope of the inventions. For example, a variety of recording materials, layers, and configuration may be used according to the described examples; a variety of tape drive designs may operate according to the described examples; and a variety of methods may be used for creating a storage tape according to the described examples.
Magnetic tape drives generally operate by streaming storage tape from a cartridge reel and spooling the storage tape on a drive take-up reel, which may be described as operating in a forward direction; additionally, a magnetic tape drive may operate by pulling tape from the take-up reel and spooling back onto a cartridge reel, which may be designated as operating in a reverse direction. The tape path includes a data transducer head that has read and write head portions. During forward operation, the head is used to conduct read and/or write operations on a portion of the longitudinal tracks. After the storage tape has been pulled an amount (e.g., the tape has been entirely pulled from the cartridge reel and spooled on the take-up reel), the drive may operate in the reverse direction, whereby other of the longitudinal tracks not used during the forward operation may be read from and/or written to. By operating the drive in both forward and reverse directions, throughput of the drive may be increased as rewind operations are not required before further read/write operations may begin.
The ability to operate a linear tape drive in both forward and reverse operations is enabled, in part, by characteristics of conventional MP tape media. For example, generally, a Magnetic Particle (MP) coating applied to tape can be read and written in either the forward or reverse direction without negatively impacting the recording capacity.
In one example provided herein, a data storage tape includes a substrate having a recording layer disposed on opposite major sides thereof (or at least adjacent thereto, i.e., an additional layer of material may be disposed between one or both of the recording materials and the substrate). The recording layer comprises a uni-directional recording material (e.g., writing data to the material is more efficient or effective in one direction due to characteristics of the material or structure of the recording layer). One exemplary uni-directional recording material includes an Advanced Metal Evaporated (AME) coating. The recording layers are oriented in opposite directions with the substrate, e.g., a first direction on the first side of the substrate and in an opposite, second direction on the opposing second side of the substrate.
A data storage tape having dual sided, uni-directional recording layers may be used within a magnetic storage drive having heads positioned for data transfer functions on both major sides of the data storage tape. In one example, each head operates in a unidirectional fashion similar to conventional linear tape drives, and together may operate similar to conventional bi-directional magnetic storage tape described above. Certain uni-directional recording material, such as AME, may allow for increased storage capacity relative to conventional recording materials such as MP recording materials, thereby increasing the storage capacity for a given length of magnetic storage tape or cartridge size, and allowing for conventional bi-directional operation with a linear tape drive.
Certain features of the examples described herein may be aided by a brief description of general characteristics and manufacturing process of AME media (which is typically uni-directional). In contrast to storage tape including an MP recording layer, AME media is generally made by evaporating cobalt using, e.g., an electron beam, and providing a small amount of oxygen to create an oxide of the cobalt. The cobalt oxide forms a passive layer, isolating magnetic domains from each other, and passivating the tape substrate. Typically, AME designs are absent a binder material, which consumes volume of the recording layer, thereby reducing the volume available to active recording material and reducing the storage capacity of the media.
Further, AME media is generally uni-directional; for example, a write head may record more efficiently and/or at a greater density in one direction versus an opposite direction. The uni-directional nature of AME media is largely due to how AME media is typically manufactured as illustrated, for example, in
The cobalt molecules are largely shielded from being deposited directly one tape substrate 102 after evaporation by shields 105, 150, and 155; rather the cobalt condenses out onto substrate 102 as the cobalt cools. Further, oxygen is introduced to react with a portion of the cobalt to form cobalt oxide. The cobalt oxide forms a seed layer on tape substrate 102, passivates the elemental cobalt, as well as separate individual domain sites or columns of cobalt in the recording layer, resulting in data storage tape 120.
In this example, the cobalt is deposited on the substrate 102 as the substrate curves around the roller 115, which results in the cobalt being deposited on a moving surface. This results in the cobalt deposits depending on the incident direction of the deposition vapor. For example, because the roller is moving substrate 102 along a curve, the cobalt columns generally are not deposited in a straight vertical arrangement; rather, they deposit in a curved shape, which has traditionally been referred to in the art as a “banana” shape.
Recording to AME layer 230 is performed generally in a vertical fashion (e.g., along the direction of the thickness of the substrate 220 and tape 200), rather than longitudinally or parallel to the surface of the substrate 220, as is typical with MP media. Additionally, AME layer 230 is generally “keepered,” wherein the flux from adjacent bit cells tends to reinforce, rather than induce stress demagnetization as common with longitudinal recording. Both of these features will mitigate the issues of print-through and contact recording as discussed with MP media.
During the writing process, the orientation of the final flux through each domain or column 232 as it passes through flux path 242 determines the recorded magnetization. Accordingly, if the media moves from right to left as shown in
Accordingly, if the media is moving from left to right, the leading domains (columns 232) form an extension of the leading pole tip 241 below the written domains, and vertical recording is achieved (with all of the advantages of vertical recording such as potentially higher density recording). Additionally, depending on the maximum run length written and the geometry of column 232, the depth of magnetic recording may be limited to the upper portion of column 232, which may reduce saturation in an MR read element and reduce or eliminate the need to write equalize.
Accordingly, in one example, the AME layer 230 is preferably recorded in a direction taking advantage of the curved shape of columns 232, and is thus generally considered a uni-directional media (e.g., where the media is more effectively and/or efficiently written from right to left than left to right in this instance).
Additionally, in one example, at least one of the AME layers 230a and 230b may include material or a manufacturing process designed to allow for separation from the opposing AME layers when in contact (e.g., when wound on a reel). In other examples, a coating or layer shown as separation layer 250 may be disposed over one or both of AME layers 230a and 230b. Separation layer 250 may include various materials such as Diamond Like Coatings (DLC), or the like, which may reduce adhesion and allow separation from the opposing surface when wound on a reel. Separation layer 250 or similar coating(s) may also generally provide protection and or lubrication to the surface thereof.
AME layers 230a and 230b may be disposed sequentially onto substrate 220 in any suitable fashion, including two sequential passes through a system similar to that shown in
Substrate 220 may include various flexible materials including a plastic substrate such as PolyEthylene Terephthalate (PET), PolyEthylene Naphthalene (PEN), PolyAramid (PA), or the like. Further, although shown and described as a single layer, it should be understood that substrate 220 may include any number of layers or different materials depending on the particular application.
It will be recognized that the thickness of AME layers 230a, 230b, separation layer 250, and substrate 220 are not drawn to scale. For example, the thickness of substrate 220 may be on the order of microns, and in one example between 3 and 5 microns; the thickness of AME layers 230a and 230b may be less than 1 micron, and in one example between 30 nm and 200 nm; and the thickness of separation layer 250 may be on the order of nano-meters or less, and in one example between 5-15 nm. Of course, these thickness values and ranges are for illustrative purposes and thickness values greater or less than stated here are contemplated.
It is noted that AME layers 230a and 230b record information in a vertical fashion (e.g., along the vertical depth of columns 232). This provides the potential advantage of increasing the volume of the recorded bit cell over a longitudinal orientation, thereby increasing the potential storage density for a give surface area of tape 300. For example, a recorded bit cell extends deeper into the recording layer than in the case of MP media, providing a portion of the bit-cell that is under less stress.
AME layers 230a and 230b are also “keepered,” wherein the flux from a given bit-cell tends to return to itself though adjacent bits and thus the flux from adjacent bit cells tends to reinforce, rather than induce stress-demagnetization (as typically with longitudinal recording such as with MP media). Both characteristics would tend to mitigate the issue of print-though and contact recording when tape 300 is wound on a reel and AME layers 230a and 230b are in contact (or at least disposed in closed proximity).
In one example, as media 500 is pulled from cartridge 514 and wound on take-up reel 517, a forward data transducer head 540f is active and performs data transfer operations on media 500, while a reverse data transducer head 540r is inactive (e.g., does not perform data transfer operations). As the direction of transport of media 500 is reversed and spooled back to the reel of cartridge 514, forward data transducer head 540f is inactive and reverse data transducer head 540r is active for performing data transfer operations. In this manner, tape drive 501 may operate in a bi-directional manner within a linear tape drive using uni-directional media.
The control and operation of media 500 and data transducer heads 540f and 540r may be controlled by a drive controller 510 included with tape drive 501 and base 502, or alternatively, by a host system. For example, drive controller 510 includes or accesses logic for carrying out various aspects described herein. Such logic may be included in hardware, software, firmware, or combinations thereof as will be recognized by one of ordinary skill in the art.
In other examples, data transducer heads 540r and 540f may be active during both forward and reverse directions of tape transport for data transfer functions. Further, in some examples, one of the first transducer head 540r and 540f may be active for data transfer functions and the other active to perform servo functions. Further, it will be recognized that various other features and configurations of tape drive 501 are possible and contemplated. For example, the number and position of guide rollers 528, transducer heads, guide surfaces, and the like included with drive 501 may be altered for various different application and design considerations.
It is noted that the use of the term “tape” herein is used for illustrative purposes, and refers generally to any flexible magnetic storage media, and does not require the use of a media having a substantially longer longitudinal dimension than width as with conventional tape media.
The above detailed description is provided to illustrate various examples and is not intended to be limiting. It will be apparent to one of ordinary skill in the art that numerous modifications and variations within the scope of the present invention are possible. Further, throughout this description, particular examples have been discussed and how these examples are thought to address certain disadvantages in related art. This discussion is not meant, however, to restrict the various examples to methods and/or systems that actually address or solve the disadvantages. Accordingly, the present invention is defined by the appended claims and should not be limited by the description herein.
