Abstract:
A polymeric media with increased mechanical performance includes a signal transduction region having a nominal thickness and a clamp system integrally attached to the interior diameter of the disc. The thickness of the media is tailored, with respect to its modulus of elasticity, to provide planar stiffness at least equal to metal-based media, assuring stability at a small sacrifice and overall height of the drive system. The interior clamp, which is advantageously molded integrally with the signal transduction portion of the media, can incorporate a spacer section, so as to be seated on a shoulder on the spindle mechanism, or allow stacking of discs on a common spindle. The interior clamp configuration including conical fingers which snap into place on the spindle during installation and thereafter maintain concentricity during rotation, without other attachments. Protruding contact elements may be integrally formed along a radial band on the disc used for head landing area, so as to minimize stiction during starting and stopping.

Description:
REFERENCE TO PRIOR APPLICATION 
     This application claims the benefit of provisional application Ser. No. 60/109,109, entitled “INJECTION MOLDED MEDIA WITH INTEGRAL CLAMP AND SPACER,” filed on Nov. 18, 1998. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to planar media for high density recording and reproduction, and more particularly to devices and methods for providing low cost but high performance media and methods of fabricating the same. 
     BACKGROUND OF THE INVENTION 
     As the art of recording and reproducing data from rotating media have advanced, cost performance factors have reached levels that were once thought unobtainable. By improving the media surfaces so that surface asperities are of the order of a microinch or less, by using highly efficient transducers interactive with very narrow track widths, and by aerodynamic designs which maintain the transducers at microinch or less gaps from the media surface, the number of tracks per inch and the number of bits per inch along the track have been increased by orders of magnitude, and continue to increase. At the same time, the need for mass production of the discs, head access systems and transducer devices has been met so that at this time disc drives using magnetic and magneto optical technology are commercially available that have capacities in the gigabyte range at costs which are, even for single piece quantities, in the low hundreds of dollars. 
     This constant refinement and improvement continues, and advances in media technology are an area of significant interest. Whereas the conventional approach has been to utilize metal and metal-based discs, i.e., aluminum, some designers have more recently utilized polymeric materials, which can be molded to shape, and then surfaced with successive layers for the desired magnetic or magneto-optical properties. These approaches have been directed toward arrangements that are in large measure, the equivalent of aluminum discs. In other words, have been designed so as to be 1:1 equivalents of metal discs, in their form factors and methods of attachment to the drive spindle. An exception is a small disc which has been molded as a single piece, integral with the central spindle, but this is a specialized version of limited general utility, because it is designed for a low cost unit of very small form factor. 
     The strategy of using polymeric materials for higher performance units, continues to suffer performance drawbacks. Both track registration and flyability (transducer to media spacing) are adversely affected because the media is not sufficiently stable to meet the exactness required of transducer radial position and flying height reference. 
     SUMMARY OF THE INVENTION 
     Polymeric media in accordance with the invention are configured, in relation to a central supporting drive spindle, to be integral units having an interior clamp configuration that snaps into place on the spindle and thereafter maintains concentricity during rotation, without other attachments. Further, the thickness of the media is tailored, with respect to its modulus of elasticity, to provide planar stiffness at least equal to metal-based media, assuring stability at a small sacrifice and overall height of the drive system. Furthermore, the interior clamp, which is advantageously molded integrally with the signal transduction portion of the media, can incorporate a spacer section, so as to be seated on a shoulder on the spindle mechanism, or allow stacking of discs on a common spindle. Furthermore, protruding contact elements may be integrally formed along a radial band on the disc used for a head landing area, so as to minimize stiction during starting and stopping. 
     In an example of an integral polymeric disc in accordance with the invention, the active recording area includes a structure of uniform thickness in which the product of the modulus of elasticity and the cube of the disc thickness provides a stiffness at least equal to that of a metal-based disc. The disc includes an interior integral clamp area in the form of a shallow conical surface having interior fingers spaced circumferentially about an interior bore sized to fit with pressure on a given spindle. The spindle has an uppermost cap member with respect to which the fingers expand as the disc is moved down into position over the cap, and then snapped into place against the outer circumference of the spindle below the cap. A circumferential band on the surface of the media encompassing the head landing area for start and stop operations includes multiple integrally molded projections to reduce stiction and minimize wear. 
     According to a first aspect of the invention, there is provided a rotatable device for signal recording and reproduction operations where the device has a rotatable spindle and a planar disc body. The planar disc body includes a molded member of polymeric material which has a signal transduction portion of a constant thickness. The thickness is large enough to reduce off track motion due to nonrepeatable runouts. Also included is a deformable inner radial hub coupled to an inner radial disc region of the planar body where the deformable inner radial hub has resilient members disposed about a central bore and sized to seat against the spindle circumference. 
     According to a second aspect of the invention, there is provided a rotatable device that has a rotatable spindle and a planar disc body. The planar disc body includes a molded member of polymeric material that has a principal signal transduction portion of constant thickness. The thickness is large enough to reduce off track motion due to non-repeatable runout. Also included is a deformable inner radial hub coupled to an inner radial disc region of the planar body. 
     According to a third aspect of the invention, there is provided a device for reducing frictional heating and friction between a recordable disc and a read/write head during the initiation and termination of disc rotation. The device includes a planar disc body with a plurality of protrusions in a radial band along a control bore of the disc and a read/write head wherein a pad is coupled to a contact surface of the head, interposed between the head and the central bore. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A better understanding of the invention may be had by reference to the following description, taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a side view of portions of a conventional disc drive system and recording disc; 
     FIG. 2 is a side sectional view of a polymeric disc in accordance with the invention, having transition, clamp and landing regions; 
     FIG. 3 is a side view of the landing zone region of the polymeric disc in FIG. 3 is accordance with the invention; 
     FIG. 4 is a fragmentary sectional view of the transition and clamp regions of the polymeric disc in FIGS. 2 and 3, showing further details thereof; 
     FIG. 5 is a fragmentary sectional view showing an alternative form of the transition and clamp regions of the polymeric disc in FIG. 4 in accordance with the invention; 
     FIG. 6 is a perspective view of the polymeric disc in FIGS. 2-4 during installation on a spindle in accordance with the invention; 
     FIG. 7 is a partial sectional view of the hub region of the spindle and polymeric disc of FIG. 6; 
     FIG. 8 is a partial sectional view of the hub region of the spindle and polymeric disc in FIG. 7 after installation in accordance with the invention; 
     FIG. 9 is a partial sectional view of an alternative embodiment of a polymeric disc in accordance with the invention; 
     FIG. 10 is a partial sectional view of the disc in FIG. 9 in a disc stack configuration in accordance with the invention; and 
     FIG. 11 is fragmentary sectional view of the spacer and integral spacer regions of the discs stacked in FIG. 10 in accordance with the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Conventional disc drive systems typically include one or more recording discs mounted for relatively high speed rotation on a central spindle. For example, FIG. 1 shows a side view of portions of a conventional disc drive system, including a conventional data storage or recording disc  40  supported on a spindle  100 . A disc drive motor (not shown) is operatively coupled to the spindle  100  for rotation of the spindle and the disc supported thereon. A recording and/or reading head  20  is supported by suitable head support structure (not shown) adjacent the recording surface of the disc. To simplify the disclosure, FIG. 1 is shown with a single recording disc  40  having a single recording surface and a single head  20 . However, other conventional disc drive systems employ multiple discs, double-sided discs (discs with recording surfaces on both surfaces) and multiple heads. 
     Typically, multiple center-open discs and spacer rings are alternately stacked on a spindle motor hub. The hub, defining the core of the stack, serves to align the discs and spacer rings around a common axis. Collectively the discs, spacer rings and spindle motor hub define a disc pack assembly. 
     The surfaces of the stacked discs are accessed by the read/write heads which are mounted on a complementary stack of actuator arms which form a part of an actuator assembly. Generally, the actuator assembly has an actuator body that pivots about a pivot mechanism disposed in a medial portion thereof. A motor selectively positions a proximal end of the actuator body. This positioning of the proximal end in cooperation with the pivot mechanism causes a distal end of the actuator body, which supports the read/write heads, to move radially across the recording surfaces of the discs, such that the head may be selectively positioned adjacent any recording location on the recording surface as the disc is rotated. 
     In operation, the head  20  is moved in the radial direction to align or register with a desired track location on the recording surface of the disc. Once aligned or registered with the desired track location, the head  20  reads or writes information onto the recording surface. Because the tracks are very narrow and very closely spaced, in the present state of the art, dimensional precision and stability are of paramount importance. It is important not only to properly register the head  20  with the track location to effect accurate reading and writing operations, but also to have a surface that enables the head flying height to be stable at the extreme spacings that are currently used. To achieve these physical properties with an economically justifiable mass produceable product, the principal approach has been to employ metal (e.g. aluminum) substrates with active media layers. Currently, disc drives using magnetic and magneto optical technology are commercially available, however, magneto optical disc suffer a number of performance drawbacks, as both track registration and liability (transducer to media spacing) are adversely affected because the media is not sufficiently stable to meet the precision demanded as a transducer radial position and flying height. 
     The present invention is more specifically directed to a polymeric data storage disc fabricated with improvements so as to improve mechanical stability in terms of the accuracy of track registration, minimization of stiction/friction between the disc and head, and flyability performance. FIG. 2 depicts a preferred embodiment of such a disc. The disc  40  comprises a track registration region  48 , a landing zone  46 , a transition region  44  and a clamp system  42 . 
     In preferred embodiments of the invention, the track registration region  48 , having a nominal thickness  41 , comprises a composition of polymers which perform under the forces of operating conditions with mechanical properties at least as good as existing aluminum discs. To minimize flyability variations, the stiffness of the disc  40  within the registration region  48  is improved over a conventional polymeric disc. To achieve the goal of making the polymeric disc media  40  as stiff as existing aluminum discs, the polymeric disc thickness  41  is increased such that the ratio of the Young&#39;s modulus of the polymeric disc  40  by the cube of the disc thickness  41  is greater than that of an aluminum disc, or E p t p   3 &gt;E Al t Al   3 . For example, a polymer based disc with a thickness of 100 mils will be mechanically superior to aluminum disc of 31 mils thickness. The thickness  41  of the polymeric disc  40  may be in the range of about 75-125 mils, and is most preferably about 100 mils. More generally, the thickness is selected to provide a stiffness that is large enough to reduce off track motion due to nonrepeatable runouts. 
     A head landing zone  46  is located along the inner diameter of the registration region  48 . As shown in FIG. 3, the landing zone has a texturized surface, including a plurality of radially spaced protrusions or bumps  60  in a circumferential band about the central axis. The bumps  60 , having a height of approximately 50-200 Å are somewhat conical in shape and include a rounded tip  61  and a base  62 , wherein the base  62  is preferably wider than the tip  61 . The bumps  60  are integrally molded into the inner diameter of the registration region  48  as the disc is fabricated. The landing zone is most effective when used in combination with a slider head  20  having diamond-like-carbon (dlc) coated pads  21  on its lower surface to minimize wear of the polymer based media  40  and reduce frictional heating and friction between the disc  40  and the slider head  20  during takeoff and landing. Because there are spaces between the small protrusions  60  and only limited contact areas with the slider head  20 , stiction is not a problem. 
     With reference to FIG. 4, the transition region  44  couples the track registration region  48  to the clamp system  42 . The transition region  44  includes a single row of circumferentially spaced perforations  43 , which aid in providing flexibility within the inner regions of the disc. In alternative embodiments, the transition region  44  may include solid polymer material. 
     Coupled to the transition region  44  of the disc  40  is a clamp system  42 . In preferred embodiments, the clamp  42  is integrally fabricated with the disc  40  during the molding operation and uses the same material used in the disc registration region  48 . The design of the clamp  42  is not particularly limited in form or shape so long as it functions to secure the disc  40  to the spindle  100 . It is preferred that no additional components, other than the clamp  42 , are required to assemble the disc  40  on to the spindle  100 . One embodiment of the integral clamp system  42  is a snap-fit clamp comprising a clamp base  56 , a plurality of fingers  54  and a retaining ring  52 . The base  56  is an annular disc having an inner diameter  55 , an outer diameter  57  and a contact surface  53 . The outer diameter  57  of the base  56  is integrally coupled to the inner diameter of the registration region  48  at the transition region  44 . 
     The plurality of conically shaped fingers  54  includes polymeric materials having compliant mechanical properties. The fingers  54  include a base surface  58  and a contact surface  59 . The fingers  54  are integrally coupled to the inner diameter  55  of the base  56  along the base surface  58  and extend radially inward, in an L-shaped configuration, such that the contact surface  59  locks within the spindle groove. 
     Coupled to the contact surface  53  of the base  56  is the annularly shaped retainer ring  52 . The retainer ring  52  is designed to engage an annular groove within the spindle hub, for retaining and aligning the disc  40  relative to the spindle assembly. 
     The polymeric material used in the disc  40  is not particularly limited so long as it is preferably relatively free from impurities and fillers. Examples of polymers which may be useful in the invention include but are not limited to Ultem from General Electric or a polycarbonate. 
     In preferred embodiments, the disc  40  is formed by injection molding of a polymer into a mold of suitable thickness. Alternatively, disc  40  may be formed by a sandwich structure using a solid core material. 
     In alternative embodiments, as depicted in FIG. 5, the clamp  42  is attached to the inner region of disc  40  in the transition region  44  at an interface surface  60 . The clamp  42  is secured to the inner region of the disc  40  at the interface surface  60  by an adhesive or other securing means, including, but not limited to, threaded fasteners, or it can be secured by an interference fit, for example. In this embodiment, a plurality of depressions  61  are radially positioned along the interface surface  60  to receive a plurality of protruding members  62 , which extend from a contact surface  63  of the clamp  42 . The members  62  aid in avoiding disc slippage during a sudden shock or jolt of the device. 
     As depicted in FIGS. 6-8, attachment of the disc  40  to the spindle  100  results when a downward pressure  105  is applied to the inner diameter of the disc  40  as it is placed over the spindle top  101 . The applied downward force  105  deforms the clamp  42 , enabling the fingers  54  to insert into the spindle groove  102 . Once within the spindle groove  102 , a clamping force  107  is generated because of the conical clamp deformation and this force presses the clamp finger  54  against the spindle groove  102 , and the tab  52  against a spindle retaining groove  104  to hold the disc securely in place. The disc  40  is further secured to the spindle  100  at the spindle top  101 , at the contact surface  59  of the conical fingers  54  locks in contact against the lower surface  106  of the spindle top  101 . Support and alignment of the disc  40  relative to the spindle axis takes place along the spindle hub  103 , as the clamp contact surface  53  rests against the contact support surface  105 . 
     In a second embodiment, shown in FIG. 9, the polymeric disc  40  comprises a spacer  70  integrally coupled to the base surface  58  of the clamp  42 . The spacer  70  is fabricated during the molding operation and includes the same material as used in the disc registration region  48 . The design of the spacer  70  is not particularly limited in form or shape so long as it functions to engage the disc  40  with a lateral surface  105  of the spindle hub  103  and separate discs within a disc stack. The spacer  70  can be designed so as to be a defined thickness  76  in order to accommodate a head-arm assembly in between the two discs which the spacer  70  separates. The spacer  70  is located in the inner diameter of the disc  40 , and is preferably located centrally to the transition zone  44 , beneath the lowermost surface of the readable portion of the disc  48 . The retaining ring  74  snaps into the spindle retaining groove  104 . 
     In a further embodiment, as depicted in FIG. 10, a number of discs are stacked in a multiple disc unit, with the uppermost disc  200  including a clamp  42  and spacer  70  and subsequent discs  210  including only a spacer  70 . In this embodiment, as shown in FIG. 11, the spacer  70  may have elements  74  on the upper or lower surface, for example tabs or slots as shown in FIG. 11, which interact with mating elements  215  on the surface of an adjacent disc or the spindle which facilitate and secure the alignment of discs in the stack. In a preferred embodiment, a retaining ring  74  is coupled to the integral spacer  70  along a contact surface  72 . The retaining ring  74  snaps into the spindle retaining groove  104  (see FIG. 9) or a spacer retaining groove  215 , where there are more than one disc in a stack, to hold the disc or discs in place. 
     The above specification, examples and data provide a complete description of the manufacture and use of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.