Abstract:
In order to reduce cycle times for assembling at least two substrates ( 3,4 ) in order to form an optical data carrier in a low-pressure chamber ( 8 ), a method and a device are disclosed wherein an opening ( 11 ) of the low-pressure chamber is sealed in relation to the surrounding environment, the low-pressure chamber is pumped out, a transfer chamber ( 64 ) is formed between a first handling device ( 16 ) arranged in the low-pressure chamber and a second handling device ( 24 ) arranged outside the low-pressure chamber by respectively sealing the opening ( 11 ) of the low-pressure chamber ( 8 ). The transfer chamber ( 64 ) has a smaller volume than that of the low-pressure chamber ( 8 ); the substrates ( 3, 4 ) in the transfer chamber ( 64 ) are transferred from the second handling device ( 24 ) to the first handling device ( 16 ); the substrates are conveyed ( 3, 4 ) with the first handling device ( 16 ) to an assembly station ( 14 ) in the low-pressure chamber when low-pressure chamber is sealed by the second handling device ( 24 ), and the substrates ( 3,4 ) are assembled in the assembly station ( 14 ).

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a method and to an apparatus for joining at least two substrates together to form a data carrier. 
     Known as data carriers, are, for example, CDs, DVDs, DVRs, FMDs, etc. which comprise at least two substrates that are glued together. 
     Pursuant to one known apparatus for the manufacture of such data carriers, as is known, for example, from DE-A-100 29 400, that originates with the same applicant, the substrates are glued together by means of a double-sided adhesive film. In a laminating station, the double-sided adhesive film is applied to a first one of the substrates, and subsequently the laminated substrate is placed upon a receiving unit having a centering and holding pin. A second substrate is also placed upon the receiving unit, whereby the two substrates are held spaced from one another by the centering and holding pin. Subsequently, the receiving unit is moved into an assembly station having a hood, which is moved into contact with the receiving unit in order to form between them a closed chamber. In this position, the chamber is pumped out via a non-illustrated device in order during the subsequent joining together of the substrates to prevent air bubbles between them. When a specified underpressure is reached in the chamber, a ram or presser that is moveably disposed in the chamber is moved in order to press the substrates together. 
     With this method, it is necessary, prior to the joining together of substrates, to pump the chamber from ambient pressure to a desired underpressure, resulting in relatively long cycle times for the joining together of the substrates. 
     Proceeding from this state of the art, it is therefore an object of the present invention to provide a method and apparatus for the joining of at least two substrates together to form an optical data carrier, pursuant to which the cycle times for the joining together can be shortened. 
     SUMMARY OF THE INVENTION 
     Pursuant to the present invention, this object is realized with a method for the joining of at least two substrates together, to form a data carrier, in a low-pressure chamber that has at least one opening for the introduction and/or removal of substrates, with the following method steps: sealing off the opening relative to the surroundings; pumping out the low-pressure chamber; forming a transfer station between a first handling device disposed in the low-pressure chamber and a second handling device disposed externally of the low-pressure chamber by respectively sealing off the opening of the low-pressure chamber, whereby the transfer chamber has a smaller volume than does the low-pressure chamber. Transferring the substrates from the second handling device to the first handling device in the transfer chamber; transporting the substrates with the first handling device to an assembly station in the low-pressure chamber, with the low-pressure chamber being sealed off by the second handling device; joining the substrates together in the assembly station. 
     Pursuant to the inventive method, the low-pressure chamber is initially brought to a desired underpressure that is kept essentially constant during and between successive joining-together processes. The respective pumping out of the assembly station for each individual joining together can be eliminated, thereby considerably reducing the cycle times. The underpressure in the low-pressure chamber can be kept constant since the transfer chamber between the first and second handling devices has a considerably smaller volume than the volume of the low-pressure chamber, and thus during the opening of the transfer chamber to the low-pressure chamber only slight pressure fluctuations occur. Furthermore, at every point in time the opening of the low-pressure chamber is sealed off relative to the surroundings by the first and/or second handling device, so that pressure fluctuations occur only during the opening of the transfer chamber. 
     Pursuant to one preferred embodiment of the invention, the transfer chamber is pumped out prior to and/or during the substrate transfer in order to still further reduce the pressure fluctuations in the low-pressure chamber. In this connection, it is not necessary for the pressure in the transfer chamber to be reduced to the pressure in the low-pressure chamber; rather, the pressure in the transfer chamber is pumped out to a pressure that lies between the ambient pressure and the pressure in low-pressure chamber. The pumping out of the transfer chamber is preferably limited to a time span that is necessary for the substrate transfer between the handling devices in order to optimize the cycle times. 
     To enable a simultaneous transfer of substrates at the opening and a joining together of further substrates in the assembly station, the first handling device preferably has at least two receiving means that are controlled in such a way that one receiving means carries the substrates during the joining together, while the other receiving means seals off the opening of the low-pressure chamber. 
     The first handling device is preferably brought into contact with the assembly station to form a joining chamber. The joining chamber is preferably pumped out to a pressure that lies below the pressure in the low-pressure chamber. In this way, it is not necessary to pump out the low-pressure chamber to the underpressure required for the joining process; rather, it is sufficient to bring the chamber to a pressure between the ambient pressure and the underpressure required for the joining process. Since the low-pressure chamber is already brought to an underpressure, the required pumping out times for the joining chamber are considerably reduced relative to the state of the art, where the joining chamber must always be brought from the ambient pressure to the underpressure required for the joining processes. 
     Pursuant to the invention, the object is also realized by an apparatus for joining at least two substrates together to form a data carrier, which apparatus has a low-pressure chamber having at least one opening for the introduction and/or removal of substrates, as well as a device for pumping out the low-pressure chamber, an assembly station in the low-pressure chamber, a first handling device for the carrying and transport of the substrates in the low-pressure chamber, the handling device being moveable from within into a position that seals off the opening, and a second handling device for the carrying and transport of the substrates externally of the low-pressure chamber, the second handling device being moveable from the outside into a position that seals off the opening. In this way there result the already aforementioned advantages that the opening for the introduction and/or removal of the substrates can always be sealed off by the first or second handling device, so that the pressure within the chamber can be kept essentially constant. 
     In their sealing positions, the handling devices preferably form an essentially closed transfer chamber having a volume that is smaller than the volume of the low-pressure chamber, so that when the transfer chamber is open to the low-pressure chamber only slight pressure fluctuations occur. To reduce the pressure fluctuations still further, a device is provided for pumping out the transfer chamber. 
     To enable a simultaneous joining together of substrates and an introduction and removal of further substrates into or out of the chamber, the first handling device has at least two substrate receiving means. The substrate receiving means each preferably have a housing having a U-shaped cross-section in order to enable a good chamber formation with the second handling device. For a good chamber formation, the second handling device preferably also has a housing having a U-shaped cross-section, as well as a moveable substrate holder. 
     To prevent the substrates from unintentionally coming into contact, the first and second handling devices carry the substrates in a spaced-apart manner prior to their being joined together. 
     For the formation of a joining chamber, the first handling device is preferably moveable into contact with the assembly station. Furthermore, a device for pumping out the joining chamber is advantageously provided. 
     Pursuant to an alternative embodiment of the invention, the apparatus has at least one further opening for the introduction and/or removal of substrates, whereby the first handling device is moveable into a position that seals off the further opening, and the apparatus has at least three substrate receiving means, and whereby at least one third handling device is provided for carrying and transporting the substrates externally of the low-pressure chamber, the handling device being moveable into a position that seals off the further opening. By means of the second opening, substrates can be simultaneously introduced into and removed from the low-pressure chamber, thereby reducing the cycle times still further. 
     The invention will be described in greater detail subsequently with the aid of preferred embodiments and with reference to the figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Shown are: 
         FIGS. 1A  to C a schematic illustration of one inventive apparatus for the assembly of data carriers, as well as a process cycle for the joining of the substrates; 
         FIG. 2  a schematic cross-sectional view of a transfer chamber formed by first and second handling devices; 
         FIG. 3  a schematic cross-sectional view of an assembly station. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     The  FIGS. 1A  to C schematically show an inventive apparatus  1  for the joining together of substrates  3 ,  4 , which are visible in  FIG. 2 . 
     The apparatus  1  has a housing  6  that in the interior forms a vacuum or low-pressure chamber  8 . An opening or passage  11  is provided in an upper wall of the housing  6 , as can be best seen in  FIG. 2 . Furthermore provided on the upper wall  10  is an assembly station  12 , which will be described in greater detail subsequently with reference to  FIG. 3 . 
     Provided in the base of the housing  6  is an exhaust line  13 , which is connected with a suction device  14 , such as a vacuum pump, to enable a pumping-out of the low-pressure chamber  8  to a prescribed value. 
     A first handling device  16 , in the form of a rotary table, is provided in the low-pressure chamber  8 . The rotary table  16  has a plate  17 , which extends essentially horizontally, as well as a rotary shaft  18  that extends perpendicular thereto. The plate  17  extends parallel to the upper wall  10  of the housing, and is moveable toward it and away from it via the shaft  18 . Furthermore, the plate  17  is rotatable about the axis of rotation of the shaft  18 . 
     Provided on the plate  17  are two substrate receiving means  20  that face toward the upper wall  10  of the housing  6 ; the two substrate receiving means have the same construction, and will described in greater detail subsequently with reference to  FIG. 2 . 
     Provided above the upper wall  10  of the housing  6  is a second handling device  24 , which is suited for the delivery and transport-away of substrates. The handling device  24  is provided with suitable axes of movement for the transport of the substrates, and can be moved from the outside against the upper wall  10  of the housing  6  in order to seal off the opening  11  in the upper wall  10  of the housing  6  relative to the surroundings, as will be described in greater detail subsequently with reference to  FIG. 2 . 
     With the aid of  FIG. 2 , the more detailed construction of one of the substrate receiving means  20 , as well as of the second handling device  24 , will now be described. 
       FIG. 2  shows one substrate receiving means  20  of the handling device  16  that is disposed upon the plate  17  of the rotary table. The substrate receiving means  20  is provided with a housing  26  having an essentially U-shaped cross-section, and that is mounted in a suitable manner on the plate  17 . The housing  26  can, of course, also be integrally or monolithically formed with the plate  17 . The housing  26  has a base wall  28  as well as a circumferential side wall  29 . 
     A centering and holding pin  32  is accommodated in the base wall  28  and is suited for centering the substrates  3 ,  4  and for keeping them spaced from one another. The centering and holding pin has, for example, a construction such as that known from DE-A-199 27 514, which originates with the same applicant and to which reference is made in order to avoid repetition. The centering and holding pin  32  has a central pin portion  34 , the outer periphery of which is adapted to the inner holes of the substrates  3 ,  4 . Provided on the pin portion are noses  36  that are moveable radially relative to the pin and upon which the substrates can rest. By means of a non-illustrated movement mechanism, the noses  36  can be moved radially toward the pin so that the substrates  3 ,  4  can move downwardly along the pin. Due to the linear outer surfaces of the noses  36 , the substrates  3 ,  4  are guided in a precisely centered manner during this movement. It can be seen in  FIG. 2  that a first substrate  4  has moved past the noses  36  of the centering and holding pin  32 , and rests upon the base wall  28  of the housing  26 . A second substrate  3  rests upon the noses  36  and in so doing is held parallel to, and spaced from, the lower substrate  4 . 
     It is to be understood that in place of the centering and holding pin  32 , the substrate receiving means  20  could also be provided with some other suitable mechanism that is in a position to receive the substrates  3 ,  4  and keep them spaced from one another, such as, for example, a pin having moveable balls, spring washers, or the like. 
     As can be seen in  FIG. 2 , there is provided on the lower substrate  4  a double-sided adhesive film  38  that was previously applied in a laminating station, as is known, for example, from DE-A-100 29 400, which originates with the same applicant and to which reference is made in order to avoid repetition. 
     The radial side wall  29  of the housing  26  has inner dimensions that are greater than the dimensions of the opening  11  in the upper wall  10  of the housing  6 . This makes it possible to seal-off the opening  11  from the side of the low-pressure chamber  8  when the side wall  29  is moved into contact with the upper wall  10  of the housing  6 . To ensure a good seal, a sealing means  40 , such as an O-ring, is provided in the upper wall  10  of the housing  6 ; the sealing means radially surrounds the opening  11  and provides a reliable sealing contact with an end face of the side wall  29  of the housing  26 . Of course, an appropriate sealing element can also be provided on or in the end face of the side wall  29  in order to provide a good seal with the upper wall of the housing  6 . 
     The handling device  24  also has a housing  46  having a U-shaped cross-section and an upper wall  48  and a circumferential side wall  49 . A substrate holder  51 , which is in a position to receive and deposit two substrates independently of one another and to keep them spaced from one another, extends through an opening  52  in the upper wall  48 . The substrate holder  51  is, for example, provided with a combination of an inner hole gripper  53  and an external gripper  54  in the form of a vacuum gripper, as is known, for example, from DE-A-198 18 479, which originates with the same applicant. The inner hole gripper  53  and the external gripper  54  are moveable relative to one another and relative to the housing  46  via suitable, non-illustrated movement mechanisms along an axis of movement that extends perpendicular to the upper housing wall  48 . 
     In order to seal off the opening  52  in the upper wall  48  of the housing  46 , a sealing device  56 , for example a bellows, extends between a back side of the external gripper  54  and an inner side of the upper wall  48 . 
     Furthermore provided in the upper wall  48  is an exhaust opening  58  that communicates with a suction device  60 , such as a vacuum pump. 
     The side wall  49  of the housing  46  is moveable from the outside against the upper wall  10  of the housing  6  in order to seal off the opening  11  relative to the surroundings. To improve the seal, there is provided in the upper wall  10  of the housing  6  a sealing means  62 , such as an O-ring. Of course, a suitable sealing element can also be provided on or in an end face of the side wall  49  in order to provide a seal between the housing  46  and the upper wall  10  of the housing  6 . 
     If the first and second handling devices  16 ,  24 , i.e., the housings  26  and  46  respectively thereof, as illustrated in  FIG. 2 , are moved into contact with the upper wall  10 , there is formed between the two handling devices a sealed-off transfer chamber  64 . The transfer chamber can be pumped out via the exhaust opening  58  and the vacuum pump  60 . The volume of the transfer chamber  64  is considerably less than the volume of the low-pressure chamber  8 , as a result of which when the transfer chamber  64  is opened to the low-chamber  8 , only slight pressure fluctuations occur in the low-pressure chamber, which can be rapidly compensated for by the vacuum pump  14 . This is particularly applicable if, prior to being opened to the low-pressure chamber  8 , the transfer chamber  64  is pumped out via the vacuum pump  60  to a pressure that is between the ambient pressure and the pressure existing in the low-pressure chamber  8 , as will be described in greater detail subsequently. 
       FIG. 3  shows the presently preferred assembly station  12 , which is mounted on the upper wall  10  of the housing  6 . In the region of the assembly station  12 , the upper wall  10  of the housing  6  is provided with an opening  66 . The assembly station  12  has a lower portion that is formed by the substrate receiving means  20  described in conjunction with  FIG. 2 . During an assembly or joining-together process, the substrate receiving means  20 , as is illustrated in  FIG. 3 , is moved from the inside against the upper wall  10 . A sealing element  68 , such as an O-ring, in the upper wall  10  radially surrounds the opening  66  and faces the low-pressure chamber, and provides a good seal between the housing  26  and the upper wall  10 . An upper portion of the assembly station  12  is formed upon the outer side of the upper wall  10 . This upper portion has a housing  70  having a U-shaped cross-section. The housing  70  has an upper wall  72  as well as a circumferential side wall  73  that radially surrounds the opening  66  in the wall  10  of the housing  6 . The side wall  73  is connected in a sealing manner with the upper wall  10  of the housing  6 . 
     Provided in the housing  70  is a flexible membrane  74  that completely spans the interior of the housing  70  and thereby forms a closed-off air chamber  75  on that side of the flexible membrane  74  that faces away from the low-pressure chamber  8 . 
     The air chamber  75  is subjected to underpressure or partial vacuum via a suction device  78  and an appropriate conduit  79  in the upper wall  72  of the housing  70 . 
     A plate  82 , which faces the low-pressure chamber  8 , is mounted in a suitable manner on the membrane  74 , so that the plate  82  is moveable along with the flexible membrane  74 . 
     Counter supports  84  are provided in the air chamber  75  to limit an upward movement of the membrane  74 , and the plate  82  mounted thereon, i.e. into the air chamber  75 . 
     By means of a spring  86 , which extends between the upper wall  72  and the membrane  74 , the membrane  74  is preloaded against the counter supports  84 . The force of the spring  86  is such that upon pressure equilibrium above and below the membrane, the spring lightly draws the membrane against the counter supports  84  in order to hold it in the position shown in  FIG. 3 . Some other preloading device can, of course, also be provided in order to hold the membrane  74 , and the plate  82  mounted thereon, in the position shown in  FIG. 3 . 
     The region disposed below the membrane  74  forms, together with the substrate receiving means  20 , a joining chamber  90 . The joining chamber  90  can be subjected to underpressure or partial vacuum via a suction device  92 , for example a vacuum pump, and an appropriate line  93  in the side wall  73  of the housing  70  in order to reduce the pressure within the joining chamber  90  to below the pressure in the low-pressure chamber  8 . 
     The function of the assembly station  12  will now be briefly described in conjunction with  FIG. 3 . First, the substrate receiving means  20  is moved into the position shown in  FIG. 3  in order together with the external housing  70  to form the joining chamber  90 . At this point in time, the same pressure exists in the joining chamber  90  as in the low-pressure chamber  8 . The pressure in the air chamber  75  is similarly at or below the pressure of the low-pressure chamber in order to ensure that the membrane  74  and the plate  82  are in the position shown in  FIG. 3 . The pressure in the joining chamber  90  is now reduced still further by means of the suction device  92 . The pressure in the air chamber  75  is also further reduced to the extent that this is necessary in order to ensure that the pressure in the joining chamber  90  is not lower than the pressure in the air chamber  75 , as a result of which the membrane  74  is held in the position shown in  FIG. 3 . 
     When the desired underpressure in the joining chamber  90  is achieved that prevents air bubbles between the substrates, the pressure in the air chamber  75  is raised in a controlled manner to ambient pressure. As a consequence of the thereby-resulting pressure difference between the chamber  75  and the lower pressure in the joining chamber  90 , the membrane  74 , with the plate  82  mounted thereon, is deflected downwardly in a controlled manner, as a result of which the plate first comes into contact with the upper substrate  3  and subsequently presses the latter against the substrate  4  disposed below it. As a result of the floating mounting of the plate  82  on the membrane  74 , there results a good adaptation of the plate  82  to the support, i.e. the lower wall  28  of the housing  26 , disposed below the substrate, so that a uniform compression force is applied over the substrate. 
     The pressure in the chamber  75  is subsequently reduced further, while the pressure in the joining chamber  90  is again raised to the pressure in the low-pressure chamber  8 , so that the membrane  74 , with the plate  82  mounted thereon, is moved back into the raised position shown in  FIG. 3 . At this point in time, the joining process is concluded. Alternatively, the described membrane station can also be provided in the substrate receiving means, so that the substrate is floatingly mounted and is pressed against a stationary plate for the joining-together. 
     With the aid of  FIGS. 1A  to C, the operation of the apparatus  1  for the joining of substrates together will be described in greater detail subsequently. 
     The handling device  16  is first moved upwardly, as illustrated by the arrow  100 . The two substrate receiving means  20  are, as a result, moved from within against the upper housing wall  10 , and in particular in such a way that they radially surround the openings  11  and  66  and seal them from within. The low-pressure chamber  8 , which is sealed relative to the surroundings, is now brought to a desired underpressure via the suction device  14 , and is subsequently held at this underpressure. The movement of the substrate receiving means  20  against the housing wall can also be effected by a relative movement between the plate  17  and the substrate receiving means  20 . The handling device  24  is moved from the outside against the upper wall  10  of the housing  6  into the position shown in  FIG. 2 , as illustrated by the arrow  102 , so that the opening  11  is sealed from the outside against the surroundings. A transfer chamber  64  is formed between the housing  26  of the substrate receiving means  20  and the housing  46  of the handling device  24 ; the transfer chamber is evacuated by the suction device  60  to a pressure that lies between the ambient pressure and the pressure in the low-pressure chamber  8 . Two substrates that are to be joined together are transferred from the substrate holder  51  of the handling device  24  to the substrate receiving means  20 , and in particular in such a way that the substrates are held spaced from one another prior to, during and after the transfer. 
     After the substrates have been accommodated in the substrate receiving means  20 , the handling device  16  is lowered, as illustrated by the arrow  104  in  FIG. 1B . Due to the fact that the handling device  24  seals the opening  11  in the upper wall  10  of the housing  6  from the outside, the pressure in the low-pressure chamber is prevented from rising significantly. It is merely necessary to compensate for a slight pressure difference, which results from the transfer chamber  64  being opened to the low-pressure chamber  8 . Due to the considerably lower volume of the transfer chamber  64  relative to the low-pressure chamber  8 , and due to the fact that the transfer chamber  64  is at least partially pumped out, the pressure in the low-pressure chamber is, however, essentially constant. In the lowered position, the plate  17  is rotated with the substrate receiving means  20  about the rotary shaft  18  by 180 degrees, as illustrated by the arrow  106  in  FIG. 1B . 
     As a result, the just loaded substrate receiving means  20  is positioned below the assembly station  12 , while the substrate receiving means  20  that was previously positioned below the assembly station  12  is positioned below the opening  11 . The handling device  16  is raised, as illustrated by the arrow  108  in  FIG. 1C . The substrate receiving means  20  with the loaded substrates, which are held spaced from one another, is moved into the position shown in  FIG. 3 , and the substrates are joined together, as was described with reference to  FIG. 3 . 
     At the same point in time, the other substrate receiving means  20  seals the opening  11  from within, as shown in  FIG. 2 . To the extent that an optical data carrier assembled from two substrates is disposed in this substrate receiving means, this data carrier can be received by the handling device  24  and transported away. Since the opening  11  is now sealed relative to the surroundings from the inside, no pressure drop results in the low-pressure chamber  8  when the handling device  24  is moved away from the opening  11 . New substrates can now be loaded into the substrate receiving means  20 , as was described with reference to  FIG. 1A . 
     The foregoing description clearly shows that the low-pressure chamber  8  need be pumped-out only one time from the ambient pressure to a prescribed underpressure, and can then be held essentially constant at the prescribed underpressure, since the opening  11  in the upper wall  10  of the housing  6  is always sealed off by the first and/or the second handling device. 
     Although the invention was described with the aid of preferred embodiments, it should be noted that it is not limited to the concretely illustrated embodiments. In particular, it is not necessary that the handling device  24  be provided with a combination of an inner hole gripper and external gripper. Rather, any substrate holder can be utilized that is capable of supporting the substrates that are to be joined together in a manner spaced from one another and to transfer them to the substrate receiving means  20 . The shape of the centering and holding pin  32  of the substrate receiving means  20  can also deviate from the illustrated shape. It is only important that the substrates be held spaced from one another prior to being joined together. The configuration of the assembly station  12  can also deviate from the illustrated configuration. For example, instead of a floatingly mounted plate  82 , a non-floatingly mounted presser can also be used to join the substrates together. The substrates can also be joined together by the stroke movement of the substrate receiving means in the direction of the assembly station. In this case, the joining chamber would be eliminated, and the assembly station would be provided only with a suitable abutment for the substrate receiving means. The inventive apparatus is especially suitable for the production of conventional optical data carriers such as, for example, CDs, DVDs and DVRs. However, it is also suitable for new storage media, such as, for example, FMDs, which contain fluorescing media in a plurality of layers. Furthermore, it is not necessary for each of the handling devices to have a housing having a U-shaped cross-section. Rather, the handling devices can also have a flat cover plate, whereby the necessary transfer chamber is formed by the thickness of the upper wall and/or crosspieces or elements mounted thereon. 
     The specification incorporates by reference the disclosure of German priority document 101 00427.3 filed 08 Jan. 2001 and PCT/EP01/14662 filed 13 Dec. 2001. 
     The present invention is, of course, in no way restricted to the specific disclosure of the specification and drawings, but also encompasses any modifications within the scone of the appended claims.