Patent Application
20080050521
The following detailed description of the embodiments of the present invention can best be understood when read in conjunction with the following drawings, in which the various features are not necessarily drawn to scale but rather are drawn as to best illustrate the pertinent features, in which like reference numerals are employed throughout to designate similar features, wherein:
The present invention is based upon recognition by the inventors that the above-described disadvantages and drawbacks associated with the available vapor sources for vapor depositing thin films of a material, e.g., a polymeric lubricant, on substrate surfaces, e.g., magnetic and/or MO media substrates. Specifically, according to current practice as described above, the lubricant vapor continuously diffuses out from the interior space of the source via openings in a front wall which function as orifices for lubricant vapor and as a diffusion plate. As a consequence, outward diffusion of lubricant vapor occurs even when a disc is not positioned opposite the orifices for deposition thereon. Since the interval for deposition of a lubricant layer of desired or requisite thickness on a given disc is shorter than the idle or transport interval between consecutive discs, a significant amount of lubricant vapor exiting the source is not deposited on the disks, resulting in unnecessary consumption (loss), of expensive lubricant, thereby incurring an economic disadvantage. In addition, according to current practice, only a back wall of the enclosure of the vapor source is heated, whereby other portions of the enclosure, e.g., transversely extending sidewalls, are at a lower temperature during operation. As a consequence of this unequal heating, there is a tendency for lubricant build-up to occur on the inner surfaces of the lower temperature walls, e.g., the aforementioned sidewalls. This results in higher lubricant consumption compared to conventional dip-lubricant coating processing, along with attendant higher material-per-disc cost.
According to the invention, the above-described disadvantages and drawbacks associated with use of currently available vapor sources are eliminated, or at least minimized, by providing the vapor deposition apparatus or system with at least one improved vapor source including a shutter device for limiting flow of vapor therefrom to a predetermined interval necessary for depositing a thin film of desired thickness. As a consequence, unnecessary consumption of expensive coating material, e.g., fluorine-based polymeric lubricants utilized in the manufacture of magnetic and MO recording media, is eliminated or at least substantially reduced, thereby improving the economic competitiveness of vapor deposition processing in the automated fabrication of such products. In addition, according to the present invention, modification of the heater configuration of the vapor source effectively eliminates, or at least minimizes, accumulation of liquid material on portions of the source which do not contribute to vapor generation, e.g., sidewalls of the source.
The utility and advantageous performance of the improved vapor source according to the present invention will now be described in detail with respect to an in-line type pass-by apparatus such as disclosed in U.S. Pat. No. 6,808,741 B1 described above. However, it should be emphasized that the improved vapor source of the present invention is not limited to use with such linearly configured apparatus, but rather may be utilized to advantage in any of the above-described types of vapor deposition apparatus and systems, including, but not limited to, static, circularly configured pass-by, and linearly configured pass-by apparatus and systems.
Referring now to
More specifically, apparatus 10 comprises a series of linearly elongated, vacuum chambers interconnected by gate means G of conventional design, including a centrally positioned deposition chamber 1 including at least one, preferably a pair of spaced-apart, opposingly facing, linearly elongated lubricant vapor sources 2, and a pair of buffer/isolation chambers 3, 3′ at opposite lateral ends of central deposition chamber 1 for insertion and withdrawal, respectively, of a plurality of vertically oriented substrates/workpieces, illustratively a plurality disc-shaped substrates 4 carried by substrate/workpiece mounting/support means 5, e.g., a perforated, flat planar pallet including conventional means (not shown in the drawing for illustrative simplicity) for releasably mounting/supporting the disc-shaped substrates 4 such that each of the opposing surfaces thereof faces a respective linearly elongated lubricant vapor source 2 during “pass-by” transport. Chambers 6, 6′ respectively connected to the distal ends of inlet and outlet buffer/isolation chambers 3, 3′ are provided for use of apparatus 10 as part of a larger continuously operating, in-line apparatus wherein substrates/workpieces 4 receive processing antecedent and/or subsequent to processing in apparatus 10.
Apparatus 10 is provided with conventional vacuum means (not shown in the drawing for illustrative simplicity) for maintaining the interior spaces of each of the constituent chambers 1, 3, 3′, etc. at a reduced pressure below atmospheric pressure, e.g., from about 10−5 to about 10−9 Torr, and is further provided with a substrate/workpiece conveyor/transporter means of conventional design (not shown in the drawings for illustrative simplicity) for linearly transporting substrate/workpiece mounting/supporting means 5 through the respective gate means G from chamber-to-chamber in its travel through apparatus 10.
As indicated above, according to a preferred embodiment of the present invention of particular utility in the manufacture of disc-shaped magnetic and/or MO recording media, the substrates/workpieces 4 carried by the substrate/workpiece mounting/supporting means 5 are in the form of annular discs, with inner and outer diameters corresponding to those of conventional hard disc-type magnetic and/or MO media, and the central, deposition chamber 1 of apparatus 10 is provided with a pair of opposingly facing, linearly extending vapor deposition sources 2 for deposition of a lubricant thin film on each surface of each of the plurality of discs carried by the perforated pallet mounting/supporting means 5.
Referring to
Mounted at spaced locations along the inner surface of back wall 8 of enclosure 7 (or integrally formed therewith) are a plurality of liquid lubricant reservoirs, illustratively, but not limitatively, lubricant reservoirs 16A, 16B, and 16C, each fabricated from a block of thermally conductive material, e.g., a metal such as copper. At least one heater element 17, typically an electrical resistance heater, is mounted on or within the outer surface 8′ of the back wall 8 of enclosure 7 for heating and vaporizing liquid lubricant 18 contained in each of the reservoirs 16A, 16B, and 16C. Thermocouples (not shown in the figure for illustrative simplicity) are also provided in order to control the temperature of the vapor source as to maintain a constant lubricant vapor flux.
Generally, the deposition rate of the lubricant vapor is controlled by regulating the temperature of the at least one heater element 17, and vapor phase lubrication processing as described supra typically affords a number of advantages vis-à-vis conventional dip-coating, including solvent-free processing and more uniform lubricant thicknesses. However, design deficiencies of a vapor source such as source 2 result in several disadvantages in vapor phase lubrication processing of recording media. Specifically, according to the current design of the lubricant vapor source 2, the lubricant vapor continuously diffuses out from the interior space of the source via the openings 15 in the front wall 9 functioning as orifices for lubricant vapor and forming a diffusion plate 14. As a consequence, outward diffusion of lubricant vapor occurs even when a disc is not positioned opposite the orifices for deposition thereon. Since the interval for deposition of a lubricant layer of desired or requisite thickness on a given disc is shorter than the idle or transport interval between consecutive discs, a significant amount of lubricant vapor exiting the source is not deposited on the disks, resulting in unnecessary consumption (loss), of expensive lubricant, thereby incurring an economic disadvantage.
Another disadvantage associated with a lubricant vapor source, such as source 2, results from placement of the heater element 17 on or within the back wall 8′ of enclosure 7. Since the heater element 17 contacts only the back wall of the enclosure or reservoir, the transversely extending sidewalls (illustratively sidewalls 11, 11′) are at a lower temperature than that of the back wall 8 and liquid reservoirs 16A, 16B, and 16C during operation, and, as a consequence, there is a tendency for a quantity of lubricant build-up 18′ to occur on the inner surfaces of the sidewalls (illustratively along the interior surface of sidewall 11′. This phenomenon also results in higher lubricant consumption compared to conventional dip-lubricant coating processing, along with attendant higher material-per-disc cost.
Adverting to
Operation of in-line, pass-by apparatus 10 provided with the improved vapor source(s) 20 according to the invention involves controllable actuation of at least one shutter 21A, 21B, and 21C of each source to effectuate vapor flow therefrom for selected (predetermined) intervals consistent with deposition of thin films of selected (predetermined) thickness. Controllable actuation of the shutters for permitting vapor outflow to occur only during desired intervals is accomplished in conventional manner, e.g., by means of a control unit and solenoid devices, pneumatic actuators, etc., not shown in the drawing for illustrative simplicity. The inventive apparatus and methodology therefore effect significant reduction in consumption of expensive liquid material, e.g., fluorine-based polymericant lubricant, by limiting outflow of vapor from the vapor source to only that amount required for forming a thin film of requisite thickness, thereby enhancing cost-effectiveness of the vapor deposition processing.
Referring to
The present invention thus provides a number of advantages over conventional vapor deposition apparatus and methodology, and is of particular utility in cost-effective automated manufacturing processing of thin film magnetic and MO recording media requiring deposition of uniform thickness lubricant topcoat layers for obtaining improved tribological properties. Specifically, the present invention provides for lubricant deposition with substantially reduced lubricant consumption vis-à-vis vapor deposition apparatus and methodology utilizing vapor sources which emit vapor continuously and include temperature gradients resulting in vapor condensation on interior surfaces of the source. Further, the inventive apparatus and methodology can be readily utilized as part of conventional manufacturing apparatus/technology in view of their full compatibility with all other aspects of automated manufacture of magnetic and MO media. Finally, the inventive apparatus and methodology are broadly applicable to a variety of vapor deposition processes utilized in the manufacture of a number of different products, e.g., mechanical parts, gears, linkages, etc., requiring lubrication.
In the previous description, numerous specific details are set forth, such as specific materials, structures, processes, etc., in order to provide a better understanding of the present invention. However, the present invention can be practiced without resorting to the details specifically set forth. In other instances, well-known processing materials, structures, and techniques have not been described in detail in order not to unnecessarily obscure the present invention.
Only the preferred embodiments of the present invention and but a few examples of its versatility are shown and described in the present invention. It is to be understood that the present invention is capable of use in various other embodiments and is susceptible of changes and/or modifications within the scope of the inventive concept as expressed herein.
