Patent Publication Number: US-2009235835-A1

Title: Method and apparatus for processing flexographic printing plates

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an apparatus and method for exposing, thermally processing, and post-processing a flexographic plate at a single workstation. 
     Flexographic printing plates are well known for use in printing to a variety of printing surfaces. Flexographic printing plates typically consist of a photocurable material. An image or pattern is created on the flexographic printing plate by exposing select portions of the flexographic plate to a high intensity light, such as that described in U.S. Pat. No. 6,700,598. Exposing the photocurable material to high intensity light causes the cross linking of monomers and/or polymers within the photocurable material, resulting in a cross-linked compound that is more solid than the gel-like photocurable material. By exposing select portions of the photocurable material to high intensity light, a desired image or pattern can be created on the flexographic plate. 
     A number of steps are required to successfully process a flexographic plate. The first step is to create an image mask corresponding to the desired image. This can be done either digitally or by analog means. The digital method is used on flexographic plates manufactured with a carbon overcoat layer. A laser imaging source is scanned across the flexographic plate, selectively heating and removing the overcoat layer of the flexographic plate to create a mask corresponding to the desired image in a process known as “ablation”. The analog method involves creating a photomask or negative of the image to be plated, known as an image setter, which is then intimately attached to the surface of the flexographic plate. 
     After creating the image mask, the next step is to expose the flexographic plate (i.e., the unmasked portions of the flexographic plate) to high intensity UV light. The high intensity light cures or cross links the photocurable material, creating a solid cross-linked compound in the areas exposed to high intensity light. Both the front and the back of the flexographic plate are subjected to high intensity exposure. Exposing the back of the flexographic plate to high intensity light causes the back of the plate to solidify to about one half of the total depth of the flexographic plate. This creates a solid backing area or “floor” for the flexographic plate. High intensity exposure of the front of the masked flexographic plate, sometimes referred to as main exposure, results in the cross-linking or curing of those portions of the flexographic plate exposed by the image mask. Areas of the flexographic plate covered by the image mask are not exposed to the high intensity light, and the photocurable resin material in these areas remains in the non-solid, uncured photocurable state. 
     Following exposure of both the front and back of flexographic plate (which may be performed in any order), the next step is to remove the remaining uncured photocurable resin material from the front of the flexographic plate. This can be done either with a “wet” process which makes use of solvents and brushes to loosen and remove the uncured photocurable resin material, or by means of a “dry” process that employs thermal processing to heat (and partially liquefy) the remaining uncured photocurable resin material, which is removed from the flexographic plate by an absorbent material known as “blotter”. A well-known “dry” process is taught by the Cohen patent (U.S. Pat. No. 3,264,103), which employs a flat iron and filter paper to remove uncured photocurable resin material. Thermal processing of flexographic plates is more desirable than conventional wet processes, because it does not require the use of solvents such as volatile organic compounds (VOCs), which are hazardous and difficult to dispose safely. Also, thermal processing does not require extended drying times necessary to wet processes. 
     Following removal of the remaining uncured photocurable resin material, the following step is to once again expose the flexographic plate to high intensity light in what is known as post-processing exposure, which ensures that all remaining uncured photocurable resin material is cross-linked or cured. Following post-processing exposure, the surface of the photographic plate is exposed to short wavelength (less than 270 nanometers) UV light to insure the plate has a hard non-tacky surface, which is known as “detackification”. 
     In the conventional process, great care must be taken between each of the above steps, which are performed at separate stations. Flexographic plates are easily scratched or otherwise blemished in a way that renders useless the image represented on the plate. Flexographic plates are expensive, and losing plates due to corruption resulting from handling is therefore quite undesirable. It would therefore be beneficial if flexographic plates could be processed at a single station. Other improvements in the steps of the process would also be beneficial. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides a system and method of exposing, thermally processing, and post-processing a flexographic plate at a single workstation. In one embodiment, the system includes a workstation for receiving and holding a flexographic plate, an exposure light system, and a thermal processing system. The exposure light system provides high intensity UV light for curing the exposed photocurable material on the flexographic plate. The thermal processing system provides thermal energy to the surface of the flexographic plate, which causes the uncured photocurable material to liquefy. Absorbent material supplied between a heated element and the flexographic plate removes the uncured liquefied photocurable material. 
     In another embodiment the system and method of exposing, thermally processing, and post-processing a flexographic plate includes a gantry system that includes a main exposure assembly, a pre-heater assembly, a thermal processing assembly, and a germicidal detack lamp assembly. The gantry system moves each of the attached assemblies over the flexographic plate as required to expose, thermally process, and post-process the flexographic plate located on the workstation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  are side view diagrams of a first embodiment of a flexographic plate exposure/thermal processing/post-processing system of the present invention. 
         FIGS. 2A and 2B  are side view diagrams of a second embodiment of a flexographic plate exposure/thermal processing/post-processing system of the present invention. 
         FIG. 3  is a cross-sectional view of the heated element used in systems shown in  FIGS. 1A ,  1 B,  2 A, and  2 B. 
         FIG. 4  is an exploded view of a thermal processing assembly. 
         FIGS. 5A-5C  are side view diagrams of several exemplary embodiments of a heated element used in the systems shown in  FIGS. 1A ,  1 B,  2 A and  2 B. 
         FIG. 6  is a flow chart of the steps used in processing a flexographic plate using the exposure/thermal processing/post-processing system of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1A  shows an exemplary embodiment of flexographic plate exposure/processing/post-processing system  10  (“flexographic system  10 ”) of the present invention. Flexographic system  10  provides a single work station for exposing and curing the photocurable material of flexographic plate  18 , removing excess uncured photocurable material through a thermal processing step, and post-processing (including detack) of the flexographic plate. 
     Flexographic system  10  includes exposure light system  12 , thermal processing system  14 , and work area  16 . In this embodiment, flexographic plate  18  is laid flat on work area  16 , which includes support plate  19  and support posts  21 . Clamps (not shown) secure flexographic plate  18  to support plate  19 . In one exemplary embodiment, support plate  19  regulates the temperature of the non-image (bottom side) of flexographic plate  18  during the thermal processing stages. In this exemplary embodiment, a plurality of water filled channels or tubes (not shown) are included within support plate  19 , allowing the temperature of support plate  19  (and thus the non-image side of flexographic plate  18 ) to be controlled by heating or cooling the water being pumped through the tubing. Maintaining the non-image side of the flexographic plate at a desired temperature prevents uneven thermal expansion of the flexographic plate. 
     In another exemplary embodiment, a conformal thermally conductive cushioned surface (not shown) is located between flexographic plate  18  and support plate  19 , creating a cushioned surface to support flexographic plate  18 . The conformal cushioned surface provides additional support that protects the flexographic plate from damage during the exposure/thermal processing/post-processing stages. The thermally conductive cushioned surface also conducts heat away from the non-image side of flexographic plate  18 . 
     As shown in  FIG. 1A , exposure light system  12  includes light source  20 , reflector  22 , and filter  24 . In one embodiment, exposure light system  12  is implemented as described in U.S. Pat. No. 6,700,598, assigned to Cortron Corporation and incorporated by reference herein. Light source  20  is a liquid cooled light source providing ultraviolet (UV) light to flexographic plate  18  located on work area  16 . Reflector  22  ensures uniform application of UV light to flexographic plate  18 . Filter  24  allows exposure light system  12  to be used in more than one capacity. For instance, during main exposure of flexographic plate  18  to cure the exposed photocurable material (creating a hardened cross-linked compound), UV light having a wavelength between 365 to 400 nanometers is desired. Therefore filter  24  is adjusted to remove light falling outside of this desired wavelength. During a later step known as “detackification”, UV light having a wavelength of less than 267 nanometers is desired to further harden the cured or cross-linked compound portions of flexographic plate  18 . In this case, filter  24  is adjusted such that light having a wavelength greater than 267 nanometers is removed. In one embodiment, adjustment of filter  24  is done manually by replacing a filter plate (not shown) located within filter  24 . In another embodiment, the filter plate is automatically adjusted based on the wavelength desired. 
     After main exposure of flexographic plate  18  to UV light, in which the exposed areas of the photocurable material are cured and solidified, thermal processing system  14  is used to remove the remaining excess photocurable material (which is uncured and gel-like). Thermal processing system  14  transfers thermal energy to the surface of flexographic plate  18 , causing only the surface of the remaining photocurable material to become more viscous. Thermal processing system  14  is controlled to move over the surface of flexographic plate  18  as an absorbent material known as “blotter” is pulled between the thermal processing system  14  and the surface of flexographic plate  18 , removing the viscous photocurable material. 
       FIG. 1B  shows a detailed side view of the components included in thermal processing system  14 . Thermal processing system  14  includes supply roll  26 , take-up roll  28 , a number of absorbent material rollers  29 ,  30 ,  31 ,  32 , and  33 , gear drive  34 , heated element  36 , top rollers  38  and  39 , bottom rollers  40  and  41 , rack  42 , rail  44 , and press device  46 . Gear drive  34 , top rollers  38  and  39 , bottom rollers  40  and  41 , rack  42 , and rail  44  form a gantry system that allows heated element  36  to be moved over flexographic plate  18 . Gear drive  34  uses rack  42  in a rack and pinion system to move thermal processing system  14  longitudinally along rail  44 . Thermal processing system may also be moved laterally (into and out of the page) to process flexographic plates with a width greater than the width of heated element  36 . Top roller  38  and  39  support the weight of thermal processing system  14  as well as guide thermal processing system  14  along rail  44 . Bottom rollers  40  and  41  secure thermal processing system  14  to rail  44 , as well as guide thermal processing system  14  along rail  44 . 
     In general, press device  46  causes heated element  36  to be pressed against flexographic plate  18 . In one embodiment, press device  46  is a direct acting large displacement cylinder that is either hydraulic or pneumatic. In one embodiment, the pressure generated by press device  46  is regulated by a cam (shown with respect to  FIG. 2A ) that precisely control the height of heated element  36  with respect to flexographic plate  18 . Heat generated within heated element  36  is transferred to flexographic plate  18 , which partially liquefies the non-cured photocurable material. Absorbent material supplied by supply roll  26  is pressed between heated element  36  and flexographic plate  18 , causing the partially liquefied non-cured photocurable material to be removed from the surface of flexographic plate  18 . The gantry system moves heated element along the surface of flexographic plate  18  until all absorbent material has been removed. 
     Absorbent material or blotter is wound around supply roll  26 , and threaded in a serpentine path determined by the location of absorbent material rollers  29 ,  30 ,  31 , and  32 , to take-up roller  28 . Absorbent material roller  31  is known as a “capstan” roller, which applies torque to the absorbent material to continually pull absorbent material from supply roll  26  across heated element  36  during thermal processing. To maintain tension on the absorbent material, supply roll  26  may also include an overdrive unit (not shown) that is controllable to create the desired amount of tension. In another embodiment the overdrive unit may be replaced by a back tensioner (not shown) that may also be employed to provide the requisite amount of tension to the absorbent material. Absorbent material is pulled across the portion of heated element  36  facing flexographic plate  18  to continually provide new absorbent material to the surface of flexographic plate  18  being thermally processed. In one exemplary embodiment, the absorbent material pulled across heated element  36  has a width greater than the width of heated element  36 , resulting in the absorbent material overlapping the sides of heated element  36 . Providing absorbent material with a width greater than the width of heated element  36  can result in improved guidance of the absorbent material over heated element  36 . The wider absorbent material can also act to ensure heated element  36  is kept clean, i.e., it prevents heated element  36  from coming into contact with the gel-like photocurable material being removed from flexographic plate  18 . Thus, the absorbent material continually wipes both the image side of flexographic plate  18  and heated element  36 , providing a self-cleaning mechanism to prevent removed photocurable material from adhering to heated element  36 . 
     As shown in  FIG. 1B , heated element  36  includes rigid portion  47 , heaters  48   a ,  48   b , and  48   c  (collectively, “heaters  48 ”), and cushioned layer  49 . Heaters  48  run longitudinally along the length of heated element  36 . Depending on the application, heaters may be implemented with either tubular, cartridge, or ribbon heaters. Cartridge heaters and ribbon heaters are controllable to provide “zonal heating.” Zonal heating allows the heat profile of heated element  36  to be varied as desired. For instance, a potential problem with heated elements is the decrease of thermal energy provided by the ends of heated element  36 . This temperature variance is often due to the lack of adjacent heater elements at each end of heated element  36 . Zonal heating provided by cartridge or ribbon heaters compensate for this problem by generating excess thermal energy at both ends of heated element  36 , resulting in a uniform temperature profile being generated along the length of heated element  36 . Heat ribbons are discussed in detail with respect to  FIG. 4  below. Cartridge heaters may include either a number of individual heating elements, each controllable to generate the desired heat profile, or may contain a single heating element that is custom designed for a particular application, such as by varying the configuration of windings at different regions to generate a desired heat profile. An exemplary cartridge heater for use in heated element  36  is the FireRod® Cartridge Heater manufactured and sold by Watlow Electric Manufacturing Company. The FireRod® Cartridge Heaters can be designed to specification to meet the zonal heating requirements of a particular application. 
     In other embodiments, the heat profile of heated element  36  (i.e., the distribution of temperature across the width of heated element  36 ) can be varied to suit a particular application. For instance, in one embodiment, it may be desirable to provide a higher temperature at the leading edge of heated element  36 , in order to rapidly increase the temperature of the photocurable material. In this case, heater  48   a  would be selected or positioned to provide a greater amount of heat to flexographic plate  18 . In other embodiments, different heat profiles may be advantageous, in which heaters  48   a ,  48   b , and  48   c  would be positioned or selected to provide a desired heat profile to flexographic plate  18 . 
     Rigid portion  47  and cushioned layer  49  operate to transfer heat (created by heaters  48 ) and pressure to flexographic plate  18 . Force generated by press assembly  46  is transferred through rigid portion  47  to press cushioned layer  49  into flexographic plate  18 . The rigidity inherent within rigid portion  47  results in an equal amount of pressure being applied along the length of heated element  36 . 
     While the inherent rigidity of rigid portion  47  results in consistent pressure being applied between heated element  36  and flexographic plate  18 , cushioned layer  49  results in the absorbent material being pressed in between the cured cross-linked compound regions to provide better contact, and there better absorption of the remaining uncured photocurable material. In one embodiment, cushioned layer  49  is made of a low durometer silicon rubber. Physical properties of cushioned layer  49  are selected based on the properties of the flexographic plate  18  being processed. The durometer and thickness of cushioned layer  49  can be varied to accommodate different processing depths and plate durometers. A clamp may be used to secure cushioned layer  49  to rigid portion  47 . The clamp (along with tension created by the absorbent material) holds cushioned layer  49  securely against rigid portion  47 . Because cushioned layer  49  is not fixedly attached to rigid portion  47 , cushioned layer  49  may be replaced with a new cushioned layer. For example, in different applications, it may be desirable to use a different thickness and durometer cushioned layer. The present invention allows cushioned layer  49  to be easily updated to accommodate changes in applications. 
     In other embodiments, cushioned layer  49  includes a heat transfer composition to better transport heat from rigid portion  47  to flexographic plate  18 . In yet another embodiment, cushioned layer  49  is coated with a slip coat material formed on the bottom portion of cushioned layer  49 . The slip coat material provides a low-resistance surface for the absorbent material, allowing the absorbent material to slide more easily between heated element  36  and flexographic plate  18 . In one embodiment, the slip coat is made of glass reinforced teflon. 
     The region of contact between heated element  36  and flexographic plate  18  is known as the “nip”. By altering the profile of heated element  36 , the nip geometry can be changed. The nip geometries may be altered depending on the application to provide efficient thermal processing of the flexographic plate. As shown in  FIG. 1B , the portion of heated element  36  that contacts flexographic plate  18  (hereinafter, the “bottom” of heated element  36 ) is cylindrical in shape. In other embodiments, shown in  FIGS. 3A-3C , the bottom of heated element  36  is configured to provide various nip configurations. The selected geometry of heated element  36 , along with the rigidity of rigid portion  47 , allows a controllable amount of pressure to be applied along the bottom of heated element  36 , improving the removal of uncured photocurable material. 
     In other embodiments, the rigidly connected heated element may be replaced with a heated roller. In this embodiment, as the heated roller turns, absorbent material is passed between the heated roller and the flexographic plate, causing uncured photocurable material to be removed from the surface of the flexographic plate. If a heated roller is employed, then either a tubular heater or a cartridge heater should be used to provide the required thermal energy. Once again, the cartridge heater is often advantageous due to the ability to provide zonal heating that results in a constant temperature along heated element  36 . 
     In another aspect of the invention, the orientation of heated element  36  is capable of being fixed at a selected angle with respect to flexographic plate  18 . By adjusting the orientation of heated element  36 , different parts of cushioned layer  49  can selectively be used to apply pressure between heated element  36  and flexographic plate  18 . Periodically readjusting the angle of heated element  36  prevents a single portion of cushioned layer  49  from being worn down, resulting in the entire cushioned layer  49  having to be prematurely replaced. Adjusting the orientation of heated element  36  also allows different nip geometries to be implemented with the same heated element  36 . 
     Therefore, during the thermal processing stage of processing flexographic plate  18 , thermal processing system  14  is moved by the gantry system in a longitudinal (i.e., horizontal direction) along flexographic plate  18 . Press device  46  applies vertical or downward pressure on heated element  36  to create the necessary amount of pressure between heated element  36  and flexographic plate  18 . Thermal energy generated by heaters  48  within heated element  36  causes the remaining excess photocurable material to become more viscous, allowing absorbent material pressed between flexographic plate  18  and heated element  30  to remove the remaining excess, and now viscous, photocurable material. 
       FIG. 2A  shows another exemplary embodiment of flexographic plate exposure/processing/post-processing system  50  (“flexographic system  50 ”) of the present invention. Flexographic system  50  provides exposure, thermal processing, and post-processing (including detackification) at a single workstation. Flexographic system  50  includes gantry assembly  52 , feed roller  54 , take-up roller  56 , and work area  58 . Gantry assembly  52  is mounted on linear bearings  60  and  62 . Gear drive  64  connected to rack  62  allows gantry assembly  52  to be moved laterally (i.e., in the directions shown by arrow  66 ), which allows gantry assembly  52  to operate over the entire surface of a flexographic plate. As shown in  FIG. 2A , gantry assembly  52  is shown in a first or home position (i.e., removed from work area  58 ). In this embodiment, the flexographic plate is laid flat and clamped to work area  58 . 
     Gantry assembly  52  includes main exposure lamp system  68 , pre-heater assembly  70 , heated element  72 , germicidal detackification lamp assembly  74 , cam assembly  76 , press apparatus  78 , absorbent material rollers  80 ,  82 , and  84 , and plenum  86 . As discussed above, gantry assembly  52  is movable in the direction indicated by arrow  66 , allowing each of the devices included in gantry assembly  52  to be moved relative to work area  58 . This allows flexographic system  50  to provide exposure, thermal processing, and post-processing of a flexographic plate at a single workstation. 
     During the exposure step, main exposure lamp  68  provides high intensity UV light to the exposed portions of the flexographic plate. As discussed above, the high intensity light cross-links and cures the exposed portions to create a solid cross-linked compound in the exposed areas. Gantry assembly  52  moves along the surface of the flexographic plate (by way of gear motor  64 ) as necessary to provide exposure to the entire surface of the flexographic plate. This mode of exposure, in which main exposure lamp  68  moves over different portions of the flexographic plate is known as “scanning”. This is in contrast with the fixed light source described with respect to  FIG. 1A , although either embodiment may be employed in a flexographic system that provides exposure, thermal processing and post-processing at a single workstation. 
     Following exposure of the flexographic plate with main exposure lamp  68 , pre-heater  70  and thermal processing assembly  72  (in conjunction with absorbent material rollers  80 ,  82  and  84 ) are used to remove uncured, excess photocurable material from the flexographic plate. In one embodiment, pre-heater  70  is a long wave emitter that provides thermal energy only to the image-side of the flexographic place, thus reducing the need to provide cooling to the back or non-image side of the flexographic plate. Feed roller  54  provides absorbent material (i.e., blotter webbing) to gantry assembly  52 . Absorbent material, wound in a serpentine path from feed roller  54  to take-up roller  56  through rollers  82 ,  84 , heated element  72  and roller  80 , is pressed against the flexographic plate by thermal processing apparatus  72 . Additional rollers other than the ones shown in this embodiment may be used to generate the desired tension in the absorbent material as it is passed between thermal processing apparatus and the flexographic plate being processed. Thermal energy provided by pre-heater assembly  70  and heated element  72  is provided to the surface of the flexographic plate, causing uncured photocurable material to partially liquefy. The partially liquefied photocurable material is absorbed by the absorbent material provided between heated element  72  and the flexographic plate. 
     Following thermal processing of the flexographic plate, main exposure lamp  68  may be used once again to provide post-processing of the flexographic plate. This step ensures the curing of all remaining photocurable material in the flexographic plate. Following exposure using main exposure lamp  68 , germicidal detackification lamp assembly  74  generates short-wavelength UV light to detackify the surface of the flexographic plate. As described above, detackification of a flexographic plate insures a hard, non-tacky surface of the flexographic plate. Once again, gantry assembly  52  is moved as required to detackify the entire surface of the flexographic plate. 
       FIG. 2B  shows a detailed view of gantry assembly  52  during the thermal processing stage. As shown, gantry assembly  52  is located over work area  58 . Press apparatus  78  causes heated element  72  to be pressed downward against the flexographic plate located on work area  58 . As described above, press apparatus  78  is a direct acting large displacement cylinder that may be either hydraulic or pneumatic in nature. Press apparatus provides consistent pressure between heated element  72  and the flexographic plate. The height of heated element  72  relative to the flexographic plate is determined by the position of cam assembly  76 . Mechanical stops (not shown) move downward towards cam assembly  76  as press apparatus  78  causes heated element  72  to be pressed downward towards the flexographic plate. When the mechanical stops contact cam assembly  76 , heated element  72  is held at the current height relative to the flexographic plate. By rotating cam assembly  76 , the desired height of heated element  72  relative to the flexographic plate can be altered. Precise height adjustment of heated element  72  allows the pressure applied to the image side of the flexographic plate to be precisely controlled. Precise height control of heated element  72  improves the efficiency of the system. For example, precise height adjustment of heated element  72  is particularly useful in instances in which several passes are required to fully remove all remaining uncured photocurable material. In each successive pass of heated element  72 , the relative height of heated element  72  with respect to the flexographic plate can be lowered to increase the pressure created between heated element  72  and the flexographic plate. This allows for the better quality processing of a flexographic plate as the depth of heated element  72  is adjusted on each successive pass to match the absorbancy of the absorbent material. 
     Gantry assembly  52  further includes plenum  86  that is used to capture, contain, and filter effluent material generated in the thermal processing of the flexographic plate. Within plenum  86  is a number of charcoal filters that act to filter harmful components of the effluent material. In one embodiment, an air/vacuum generator is used to create a negative pressure differential between the environment within plenum  86  and the outside environment. This forces the captured effluent through the charcoal filters. After passing through the charcoal filters, the filtered air exits plenum  86 . 
       FIG. 3  is a cross section of an alternative embodiment of heated element  72  taken along line  3 - 3  as shown in  FIG. 2B . Heated element  72  includes rigid portion  87 , at least one cartridge heater  88  located within rigid portion  87 , and cushioned layer  89 . In this embodiment, cushioned layer  89  has a tapered edge at both the left and right edge of heated element  72 . The tapered edge provides a graduation of pressure applied from heated element  88  to a flexographic plate. The tapered edge is particularly useful in embodiments that require heated element  72  to be moved laterally in a stepped process in order the process a flexographic plate with a width greater than the width W of heated element  72 . After processing a first longitudinal section of a flexographic plate, heated element  72  is moved laterally to process a second longitudinal section of the flexographic plate. Overlapping the longitudinal sections processed by heated element  72  (i.e., the tapered edged portions) results in consistent removal of uncured photocurable material along each longitudinal section. 
       FIG. 4  shows an exploded view of heated element  74 . It should be noted that thermal processing assembly  74  as shown in  FIG. 4  may also be used in conjunction with flexographic system  10  shown in  FIGS. 1A and 1B , replacing the cylindrical or cartridge type heaters shown in that embodiment. Thermal processing assembly  72  includes mounting base  90 , insulating layer  92 , clamp plate  94 , first U-shaped heating ribbon  96   a  and second U-shaped heating ribbon  96   b , center heating ribbon  98  (collectively, “the heating ribbons”), and anvil element  100  having slots for each heating ribbon. 
     Mounting base  90  connects thermal processing assembly to press assembly  78 . Insulating layer  92  is placed between mounting base  90  and clamp plate  94 . Insulating layer  92  forces the heat generated by the heating ribbons to be directed downward through anvil element  100  to the flexographic plate. Clamp plate  94  provides means for securing and holding the heating ribbons within anvil element  100 . Typically, mounting base  90 , insulating layer  92 , clamp plate  94 , and anvil element  100  are secured together with bolts or screws (or equivalent hardware). This component-based construction of thermal processing apparatus (as opposed to casted equipment which cannot be disassembled) allows a service technician to easily replace worn or damaged components (such as heating ribbons). 
     First U-shaped heating ribbon  96   a  and second U-shaped heating ribbon  96   b , along with center heating ribbon  98  fit within slots created in anvil element  100 . Center heating ribbon  98  extends along the entire length of anvil element  100 . First U-shaped heating ribbon  96  provides additional heating to the near side of anvil element  100 , while second U-shaped heating ribbon  98  provides additional heating to the far side of anvil element  100 . Each heating ribbon has leads that are connected to a controller, allowing the power provided to each ribbon heater to be varied depending on the application. For instance, a typical problem in heating elements is the uneven distribution of temperature at the ends of the heating elements (due in part to the increased surface area at the end of the heating elements). By applying additional energy to U-shaped heating ribbons  96   a  and  96   b , the temperature along the length of anvil element  100  may be maintained at a constant level. To ensure that the uncured photocurable material is heated to a liquefied state, it is important for the heating ribbons to provide uniform heat along the entire length of anvil element  100 . In one embodiment, a controller responsible for the energy provided to each heating ribbon is a PID controller, capable of precisely controlling the temperature along the bottom of anvil element  100 . 
       FIGS. 5A-5C  shows side views of three exemplary embodiments of heated elements  102   a - 102   c  highlighting the nip geometries (bottom side) that may be employed. Each of the heated elements  102   a - 102   c  shown in  FIGS. 5A-5C  may be employed in the systems described with respect to  FIGS. 1A ,  1 B,  2 A, and  2 B. The possible configurations of heated elements is not limited to the exemplary embodiments shown in  FIGS. 5A-5C . Each configuration shown in  FIGS. 5A-5C  provides a different nip profile, or contact geometry between heated elements  102   a - 102   c  and a flexographic plate. The ability to vary the nip profile allows the thermal processing system of the present invention to accommodate different processing depths, different plate durometers and different viscous thermal needs. The heated elements  102   a - 102   c  are described with special emphasis placed on the nip geometry, and it should be noted that the structure of each of the heated elements  102   a - 102   c  may be similar to the exploded view shown in  FIG. 4  of heated element  72 , which included the use of ribbons heaters. However, the heated elements  102   a - 102   c  shown in these embodiments make use of a cartridge heater to achieve the desired heat profile. As discussed above, cartridge heaters may contain multiple controllable heating elements that allow the cartridge heater to provide zonal heating. 
       FIG. 5A  shows an embodiment in which heated element  102   a  (including rigid portion  104   a  and cushioned layer  106   a ) is formed with a convex bottom (as shown in  FIGS. 1A ,  1 B,  2 A and  2 B). Cartridge heater  108  is positioned a set distance from the bottom portion of heated element  90   a , following the convex curve of heated element  102   a.    
       FIG. 5B  shows an embodiment in which heated element  102   b  (including rigid portion  104   b  and cushioned layer  106   b ) is formed with a flat bottom. This configuration provides a larger surface for contacting a flexographic plate. In this embodiment, cartridge heater  108  is positioned a set distance from the bottom portion of heated element  102   b , following the flat portion of heated element  102   b.    
       FIG. 5C  shows an embodiment in which heated element  102   c  (including rigid portion  104   c  and cushioned layer  106   c ) is formed with a concave bottom. This geometric shape may be particularly useful in applications involving a cylindrical sleeve, in which case the concave shape of heated element  102   c  can be formed to fit to the shape of the cylindrical sleeve. 
       FIG. 6  is a flowchart illustrating the steps performed by a flexographic processing system of the present invention. At step  110  a masked or ablated flexographic plate is placed on a workspace (either flat or cylindrical). Clamps or similar clamping devices are used to secure the flexographic plate to the workspace. For example, work area  16  as shown in  FIG. 1A  is an exemplary embodiment of the workspace used in step  86 . 
     At step  112  the flexographic plate is exposed to UV light in what is called “main exposure”.  FIGS. 1A and 1B  illustrate one method of exposing the flexographic plate to UV light using a light exposure system that is stationary above the workspace.  FIGS. 2A and 2B  illustrate another method of exposing the flexographic plate to UV light, in which a main exposure lamp is mounted on a gantry assembly that allows the main exposure lamp to scan over the flexographic plate. Main exposure causes exposed areas of the photocurable material to be cured, converting the photocurable material into a cross-linked compound that is rigid and solid. Areas of the flexographic plate not exposed during the main exposure step remain in an uncured, gel-like state. 
     At step  114  a thermal process is performed to remove the remaining uncured photocurable material. Heat is applied to the surface of the flexographic plate using a heated element, liquefying the uncured photocurable material. At step  116 , absorbent material, known as “blotter” or “wicking material” is applied under pressure between the heated element and the flexographic plate as shown in  FIGS. 1A ,  1 B,  2 A and  2 B to remove the excess remaining uncured photocurable material. At step  118 , the flexographic plate is again exposed to UV light in a post-processing step. Applying UV light to the flexographic plate a second time cures all remaining photocurable material. This step would be performed by light exposure system  12  as shown in  FIG. 1A , or main exposure lamp system  68  as shown in  FIGS. 2A and 2B . At step  120 , the flexographic plate is again exposed to UV light, albeit shorter wavelength UV light in a process known as “detack.” Exposing the flexographic plate to light having wavelengths less than 267 nanometers causes a hardening of the already cured cross-linked compound, ensuring that the flexographic plate has a hard, non-tacky surface. Exposure light system  12  having light source  20  and interchangeable filter  24  as shown in  FIG. 1  is one exemplary embodiment capable of performing step  120 . Germicidal detack lamp assembly  74  connected to gantry assembly  52  as shown in  FIGS. 2A and 2B  is another exemplary embodiment of an apparatus capable of performing this step. 
     Therefore, a flexographic plate processing system has been described, wherein exposure and thermal processing of a flexographic plate are performed at a single workstation. By providing exposure and thermal processing at a single workstation the number of flexographic plates damaged during transition between workstations is reduced. Thermal processing of the flexographic plate is performed with a heated element, mounted to a press device for generating pressure between the heated element and the flexographic plate. The press device maintains consistent pressure between the heated element and the flexographic plate. At least one heater (either tubular, cartridge, or ribbon type) located within the heated element provides the necessary thermal energy to at least partially liquefy the uncured photocurable material on the flexographic plate. The heated element uses zonal heating (either through multiple heaters, or by configuring the placement of windings) to ensure uniform heat is supplied by the heated element to the surface of the flexographic plate. By applying uniform pressure and temperature to the surface of the flexographic plate, uncured photocurable material is uniformly removed from the surface of the flexographic plate. 
     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.