Patent Publication Number: US-2002008022-A1

Title: Cross flow metalizing of compact disc

Description:
[0001] This is a continuation-in-part of U.S. patent application Ser. No. 08/355,664, filed Dec. 14, 1994. 
    
    
     
       FIELD OF THE INVENTION  
       [0002] This invention relates generally to the fabrication of compact discs and more particularly to a cross flow metalization system for increasing yield and decreasing complexity while permitting in-line metalization in the compact disc fabrication process.  
       BACKGROUND OF THE INVENTION  
       [0003] Compact discs or CDs are currently manufactured in a relatively complex process in which the information on the CD is first obtained for instance from a digital source. A premastering disc is created in a photo lithographic process which lays down the information in a spiral pattern. From the premastering disc, a master stamping disc is formed in an electroplating process. The master stamping disc is then used to hot stamp thermoplastic discs with the grooves or interstices which carry the information from the premastering disc.  
       [0004] Following the molding of the discs, the discs are “metalized” by placing them, via a vacuum lock, into a vacuum chamber where a thin coat of aluminum is deposited over the physical patterning on the surface of the disc (“substrate”) using a sputtering device comprising a magnetron. After metalization, the discs are spin coated to cover the metal with a protective coating such as lacquer. This is usually followed by an inspection step.  
       [0005] Compact discs were originally fabricated in a batch process in which individual discs were taken from station-to-station. Present processing requires continuous processing along an efficient flow path to take the discs from start to finish, so that more than 1,000 discs per hour can be manufactured.  
       [0006] The metalization step has caused significant throughput and quality problems in the past. Initially, the metalizer was located off-line (i.e., out of the main, direct line process flow) due to its size and complexity. These units simply could not conveniently be located in the flow path, but rather had to be located off to one side with resultant materials handling problems and complexity.  
       [0007] Metalizers can now be made part of the flow path and are currently available from Leybold in Germany and Balzers in Liechtenstein. The standard metalizers from these companies are similar in design and throughput performance. Both have rotational transport mechanisms which use a dial inside of a vacuum chamber for the transportation of a plurality of substrates (e.g., thermoplastic discs) under a single deposition source which includes a magnetron. Adjoining the vacuum chambers are external rotational transport mechanisms for bringing the substrates (discs) in and out of the vacuum chamber through a single vacuum lock. Internal and external transport mechanisms sequentially carry out the loading and unloading of the substrates.  
       [0008] These metalizers have permitted increased throughput by providing continuous processing. However, the continuous process permits only one title to be run at one time through the molding, metalizing, spin coating, and inspection process. This makes the overall investment for CD manufacturing very high because one metalizing machine must be assigned to each molding system.  
       [0009] It will be appreciated that for compact disc production, orders for compact discs are frequently in the hundreds as opposed to thousands or tens of thousands. Thus, it is very important to be able to either process different titles simultaneously or increase throughput speed to maintain the efficiency of the entire line.  
       [0010] Throughout speed is frequently increased by decreasing the dwell time under the sputtering device. This is accomplished by moving the magnetron closer to the substrate. However, this approach decreases overall quality of the disc and can render high density information discs unusable.  
       [0011] A different approach to increasing throughput speed and also permitting the simultaneous processing of multiple titles, has been developed by Leybold—a double magnetron, double vacuum lock system. Theoretically, this approach should increase disc throughput twofold. However, these machines require the disc to exit to the same vacuum lock it entered resulting in an inordinate amount of indexing complexity which significantly diminishes the theoretical increase.  
       [0012] Leybold&#39;s double lock machines have exceedingly large diameter dials, often greater than five feet. The sheer size of the vacuum deposition chamber to accommodate such large dials inhibits the insertion of this machine into the production line, to say nothing of the cost of the relatively large unit. With the use of this device a complicated process flow path is thus, inevitable.  
       [0013] The double magnetron machines also require a double index step in which “odd numbered” discs are processed by one magnetron and “even numbered” discs are processed by the second magnetron. However, with these machines, the both discs must pass under both magnetrons. It will be appreciated that with this approach, indexing errors rapidly become significant. When such errors occur during the processing of multiple CD titles, the titles become mixed up such that all of the mixed up discs must be discarded, as there is no way of identifying which disc was associated with which title.  
       [0014] More particularly, when multiple titles are to be processed, the discs of a single title are loaded onto discrete spindles, with an average of six spindles being utilized during a run. These spindles each typically hold as many as 200 CDs. If during the process indexing problems occur, then the entire lot may have to be discarded because the manufacturer must guarantee the discs loaded on a given spindle come out with the same titles.  
       [0015] Thus while the double magnetron, double vacuum lock system permits processing of multiple titles simultaneously, the potential indexing problems are so severe that such processing is generally not practical.  
       [0016] There is therefore a necessity for providing an in-line system with efficient metalizing in which indexing problems are reduced to a minimum while at the same time being able to process multiple titles, to accommodate short production runs.  
       SUMMARY OF THE INVENTION  
       [0017] The present invention is an improved metalizer which, rather than employing a single vacuum lock, single magnetron system or a multiple magnetron system with each vacuum lock handling the same disc on entry and exit, is directed to a system in which the vacuum locks through which discs are introduced into the vacuum chamber are different from the vacuum locks through which the discs exit the vacuum chamber. This approach permits not only the creation of a smaller metalizer which is capable of being interposed in a linear process flow path, but also eliminates the interleaving of discs during the metalization process and the associated, inevitable indexing problems. In one embodiment the present invention permits the use of a dial having as few as four disc carriers within the vacuum chamber, versus utilization of a more than twelve disc carrier dial within a vacuum chamber for a Leybold double magnetron metalizer.  
       [0018] In a preferred embodiment of the present invention the vacuum locks are diametrically opposed to each other on either side of the dial. Moreover, the magnetrons utilized to metalize the discs are also diametrically opposed to each other on opposite sides of the dial such that the flow of a disc from input lock to exit lock requires that the disc travel under only one magnetron. For purposes of carrying out the invention, the magnetrons need not be diametrically opposed but rather need only be on different sides of the dial. While it is preferable to have the input and exit locks diametrically opposed to be able to most efficiently operate with a linear flow of product, the vacuum locks may be offset one from the other as required. It should be noted, however, that a non-diametric arrangement of the input and exit locks expands the overall size of the equipment.  
       [0019] In operation, a disc having a first title enters the vacuum chamber from a first lock, is moved around the dial, is metalized, and exits at a second lock preferably located opposite the first lock. A second title enters the vacuum chamber via the second lock and is moved around with the dial in the opposite direction, horizontally speaking, from the direction of movement of the first-title, to produce a “cross flow”. After metalizing, the second title exits the vacuum chamber via the first lock. Thus, the flow of product in one direction is for one title, while the flow of product in the other direction is for the second title. This flow pattern guarantees title integrity as all product emerging from a given lock must be associated with one title. Thus, the present invention provides title integrity while also providing a substantially higher throughput with a better economy of machinery.  
       [0020] With the improved throughput, standard deposition rate sources may be employed at either increased spacing between the magnetron and the disc or at lower electric consumption rates to prevent pitting. Thus, one and a half times the production rate achievable with prior machines can be achieved without comprising product quality.  
       [0021] Additionally, if a single magnetron metalizer is made in accordance with the present invention it can be instantly ungraded in the field simply by adding a second magnetron at a second position. This is not possible with the majority of present metalizers since they have only a single vacuum lock, and would thus, have to be remanufactured to provide a second vacuum lock.  
       [0022] In summary, a cross flow system for metalizing compact discs, capable of being interposed in-line in the production of the CDs after premastering, mastering, electro-forming, and molding preferably includes diametrically opposed vacuum locks for a vacuum chamber and multiple metalization sources in the form of magnetrons, with a cross flow including, the introduction of a disc to be metalized through one lock and the exit of the metalized disc preferably through a diametrically opposite lock. The double vacuum lock, diametrically opposed cross flow system eliminates the problems of throughput limitations, high rate deposition, substrate pitting, and indexing software complexity which makes prior systems both costly and inefficient. The system also permits processing of more than one substrate or CD title such that multiple CD titles can be processed simultaneously. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0023] These and other features of the subject invention will be better understood in conjunction with the Detailed Description taken in conjunction with the Drawings of which:  
     [0024]FIG. 1A is a schematic and block diagram of a prior art line for the production of compact discs;  
     [0025]FIG. 1B is a schematic and diagrammatic illustration of a process for the fabrication of compact discs having an inline flow path including an in-line metalizer;  
     [0026]FIG. 2A is a diagrammatic illustration of a prior art metalization chamber utilizing a single magnetron and a single vacuum lock;  
     [0027]FIG. 2B is a diagrammatic illustration of the prior art single chamber, single vacuum lock metalization unit described in connection with FIG. 2A;  
     [0028]FIG. 3 is a diagrammatic top view of the prior art single port, single magnetron metalization unit;  
     [0029]FIG. 4 is a diagrammatic and top view of a prior art multi-port, multi-magnetron system in which compact discs enter and exit the same vacuum lock.  
     [0030]FIG. 5 is a diagrammatic representation of the Subject metalizing system utilizing diametrically opposed vacuum locks used for loading and unloading discs and double magnetron metalization stations within a vacuum chamber to implement cross flow processing;  
     [0031]FIG. 6 is a cross sectional view of a portion of a compact disc which has been metalized in accordance with the Subject Invention;  
     [0032]FIG. 7 is a top schematic view of the Subject metalization unit illustration diametrically opposed input and exit vacuum locks and multiple magnetrons, also illustrating a cross flow system for product flow through the vacuum chamber; and  
     [0033]FIG. 8 is a perspective view of the substrate lock of the present invention. 
    
    
     DETAILED DESCRIPTION  
     [0034] Referring now to FIG. 1A, after a premastering step produces a master of the particular program material or content of the disc and after electroplating, the master provides a hot stamping, embossing, or stamping plate, used in the molding of an individual disc as illustrated at  10 . This step is followed in the prior art with off-line metalization accomplished through a metalizer  12 . After metalization of the disc, the disc is spin coated at  14  and inspected at  16  which returns the completed disc to a spindle module  18  where it is available for printing and packaging.  
     [0035] It will be appreciated that in the flow process illustrated in FIG. 1A, the metalizer is located off-line due to its single port configuration. By off-line it is meant that the metalizer is not serviced by the main conveyor used to transport the molded disc through the system.  
     [0036] In contradistinction as shown in FIG. 1B, a metalizer  12 ′is located in-line with the flow of product from the molding station through the metalization station to the spin coating station. With current technology, the inspection station can also be brought in-line with the spin coating station and the spindle module.  
     [0037] Referring to FIG. 2A, a prior art metalizer  12  as shown schematically in FIG. 1A, includes a chamber  20 , located above a pump and drive housing  22  directed by a microprocessor housed in Controls Cabinet  40 . A vacuum lock manipulator  24 , picks up discs  26 , after they have exited the molding apparatus  10 . The manipulator rotates and moves up and down in a vertical plane to bring the unmetalized discs to the entrance to the single vacuum lock of the chamber. The discs are brought into the chamber and placed in a substrate holder  30  within a dial  32  which rotates the discs under a metalizing unit in the form of a magnetron  34 . The features of this prior art metalizer are shown in more detail in FIG. 2B. in which disc  26  is located within substrate holder  30  located within dial  32 , with like reference characters referring to like elements between these two figures.  
     [0038] Referring to FIG. 3, such single magnetron, single vacuum lock machines are connected to an external transport  42  from which the manipulator  24  obtains a disc  44 . The manipulator  24  places the disc  44  through vacuum lock  46  into the substrate holder  30  positioned at the vacuum lock. Disc  44  is revolved around in the direction of arrow  45  via movement of rotary dial  30  until it is positioned underneath magnetron  34 . At this point the metalization of the surface of the disc is accomplished. The disc is then moved back towards vacuum lock  46 .  
     [0039] A two magnetron, two vacuum lock metalizer is shown in FIG. 4. These metalizers also include a rotary dial  58  which, is upwards of 5 feet in diameter with  24  substrate holders  60  which are divided for ease of reference into odd and even numbered substrate holders.  
     [0040] In operation, discs of the first title, here labeled “1” are loaded into the vacuum chamber (not shown) at vacuum lock  54 , where they are placed in the substrate holder currently at that position. The second title, here labeled title “2”, is loaded through vacuum lock  56  into a substrate holder designated with an even number. By use of an indexing system (not shown), the discs are positioned under one or the other magnetron, so that magnetron  52  metalizes only the second title and magnetron  50  metalizes only the first title. This indexing pattern also causes the first and second titles to exit through the same vacuum lock each respectively entered. As noted above, when indexing problems occur with this system, all of the discs in the run have to be discarded.  
     [0041] Referring now to FIGS. 5 and 7, unlike the prior art systems, the metalization unit  70  of the present invention is interposed in the line in which load lock manipulators  72  and  76  can each receive incoming discs  74  from a molding apparatus.  
     [0042] The load lock manipulators  72  and  76  each bring their respective newly molded disks to an aperture above a vacuum lock—aperture  96  and vacuum lock  98  for manipulator  72  and aperture  104  and vacuum lock  106  for manipulator  76 —for entry into the vacuum chamber  78 . Discs entering through vacuum lock  106  (“A” discs), move around the “top” of the arc defined by the dial  100  (as shown in FIG. 7), passing under magnetron  82 . After being metalized via magnetron  83  (the end result of which is shown in FIG. 6 where the metal coating is designated  89  and the substrate is  88 ) these discs are passed out of the vacuum chamber  78  through vacuum lock  98  where they are picked up by manipulator  72 . Conversely, discs which enter vacuum chamber  78  via vacuum lock  98  (“B” discs), pass along the “bottom” of the arc under magnetron  80  and exit via vacuum lock  106 . This procedure and configuration thus, substantially reduce indexing complexity and the likelihood of indexing errors.  
     [0043] In one preferred embodiment of the present invention Disc “A” and Disc “B” are the same title being metalized via a cross flow pattern. In another embodiment, Disc “A” and Disc “B” represent different titles being simultaneously metalized and flowing in and out of the metalizer in different directions (i.e., in the cross flow pattern).  
     [0044] In yet another preferred embodiment of the present invention, the second magnetron  80  is eliminated and the disc flow is only along the “top” of the arc of dial  100 . Obviously, such a configuration lends itself to the simple addition of second magnetron  80  at a later time.  
     [0045] In still further embodiments of the present invention, the size of the dial  100  can be expanded to include more substrate holders to provide space for additional vacuum locks, manipulators and magnetrons. In other words, but for space considerations and manipulator interference, an unlimited number of vacuum locks and magnetrons, in pairs, can be employed to increase processing throughput and title handling. For example, adding one more magnetron and one more vacuum lock could allow the present invention to simultaneously process three titles. It will be appreciated by one of skill in the art however, that these additions can significantly complicate flow paths and materials handling to the point where no useful gain is realized.  
     [0046] A further feature of the present invention is shown in FIG. 8. That is, the presence of a substrate lock  120  associated with a centering pin  122  used in conjunction with the substrate holder. The centering pin  122  is used with prior art devices to precisely locate the substrate in the substrate holder. However, because of the rotational speeds of the dial  100  possible with the present invention, the substrates could become disengaged from the substrate holder. As such, the provision of substrate lock  120 , preferably in the form of spring biased steel balls, provides the ability to maintain the precision placement of the substrate in the substrate holder, throughout the substrate&#39;s travel through the vacuum chamber.  
     [0047] What has been achieved is a materials handling system which significantly improves the quality and speed with which compact discs or other articles can be manipulated through a vacuum chamber in a cross flow process in which, in a preferred embodiment, entrance and exit locks are diametrically opposed. The system is not only capable of handling compact discs which must be metalized but is also useful in semi-conductor processing in which various other substrates such as semiconductor wafers, ceramics, plastics and metals can be metalized via vacuum deposition or otherwise processed via the cross flow.  
     [0048] While reference has been made to certain preferred embodiments of the present invention, these are meant as illustrative only and it will occur to those skilled in the art that modifications can be made without departing from the spirit or intent of the invention.