Patent Document

CROSS RFERENCE TO RELATED APPLICATION  
       [0001]     Reference is made to commonly assigned U.S. patent application Ser. No. 10/184,417 filed Jun. 27, 2002 by Andrea S. Rivers et al., entitled “Depositing an Emissive Layer for Use in an Organic Light-Emitting Display Device (OLED)” and commonly assigned U.S. patent application Ser. No. ______ filed ______, by Daniel D. Haas et al., entitled ______, the disclosures of which are herein incorporated by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to organic light-emitting display devices, in particular, to methods of manufacturing and inspecting organic light-emitting diodes (OLEDS) formed by thermal transfer.  
       BACKGROUND OF THE INVENTION  
       [0003]     OLEDs are useful in a variety of applications as discrete light-emitting devices, or as the active element of light-emitting arrays or displays, such as flat-panel displays in watches, telephones, laptop computers, pagers, cellular phones, calculators, and the like.  
         [0004]     Conventional OLED display structures are built on glass substrates in a manner such that a two-dimensional OLED array for image manifestation is formed. Each OLED in the array generally includes overlying layers, starting with a light-transmissive first electrode formed on the substrate, an organic electroluminescent (EL) emission medium deposited over the first electrode, and a metallic electrode on top of the organic electroluminescent medium. When an electrical potential is placed across the electrodes, holes and electrons are injected into the organic zones from the anode and cathode, respectively. Light emission results from hole-electron recombination within the device.  
         [0005]     Two primary technical challenges relating to OLED technology are materials and fabrication. Materials science, whether related to small molecules or polymers, holds the key to the industry&#39;s ability to improve lifetime and emission efficiency. Furthermore, given that the organic materials cannot come in contact with water or oxygen, fabrication is especially difficult. Well known shadow masked based vacuum deposition technology, using conventional vacuum chambers, is often used for manufacturing OLEDs. However, shadow mask based vacuum deposition technology is limited in the precision of the deposition geometry.  
         [0006]     A laser thermal transfer (LTT) process is an example of an emerging technology for manufacturing OLEDs with potential advantages over conventional deposition processes. LTT is a process that uses heat to transfer an organic donor material (emitter material that is being transferred) onto a substrate. The donor material and substrate are held in a predetermined spatial relationship with respect to one another. The donor material includes a support layer, a thermal absorber layer and a layer of electroluminescent organic material. The LTT process includes using a laser beam that generates heat by impinging upon the absorber layer of the donor material, thereby creating heat, which vaporizes the organic material, which is subsequently deposited upon the target substrate in a predefined pattern. For example, U.S. Pat. No. 6,582,875 describes the process of using a multichannel laser print head, which transfers organic material to a patterned substrate. Several technical challenges exist for manufacturing OLEDs using the LTT process, such as implementing process monitoring and control techniques for ensuring a high-quality OLED structure. For example, visual artifacts can result if the print head is not properly aligned with the patterned substrate, or if the motion of the print head is not properly coordinated relative to the patterned substrate.  
         [0007]     For example, U.S. Pat. No. 5,994,836 describes an organic light-emitting diode (OLED) array structure, and corresponding method of making the structure. Each OLED pixel includes a first electrode on a substrate, a second electrode on a substrate, and an organic emission layer disposed between the first and second electrodes so as to emit visible light when a suitable potential is applied thereto by the electrodes. In accordance with certain embodiments of this invention, a step covering or coverage layer is provided over step or edge areas of the first electrode in order to reduce the structure&#39;s susceptibility to breakdown at pixel edges, thereby improving yields. While U.S. Pat. No. 5,994,836 describes a suitable method of manufacturing an OLED structure, it provides no mention of process monitoring, in particular, process monitoring of an LTT process for manufacturing OLEDs.  
       SUMMARY OF THE INVENTION  
       [0008]     It is therefore an object of the invention to provide a way to provide for the reduction of visual artifacts in OLED devices produced by a thermal transfer process.  
         [0009]     This object is achieved by a method of inspecting an OLED device to locate and characterize defects in the registration of organic material(s) transferred from a donor in swaths in response to heat produced by a multichannel laser print head, comprising: 
        a) optically inspecting the OLED device after or during manufacture to identify the boundaries between swaths of transferred organic material(s); and     b) determining if the swaths overlap at a seam of the boundary or if there is a gap between swath edges at the seam or if there is an offset between the edges of adjacent swaths.        
 
         [0012]     A feature of the invention is that the present invention can be used to correct the manufacturing process to minimize visual artifacts. This can be accomplished either online or after manufacture. The swath boundary errors can be effectively used to correct the manufacturing process, providing continuous process monitoring and real time process control. In addition, the swath boundary errors can be used to guide the initial system setup. The methods of analyzing the physical characteristics of an OLED display device in accordance with the invention provide a way of ensuring and maintaining a high-quality fabrication process for OLED displays.  
         [0013]     It is an advantage of the present invention to use the swath boundaries produced in the thermal transfer of organic material(s) to determine if there are or will be visual artifacts in the OLED device.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  illustrates features of a laser thermal transfer, LTT, method or process showing the relationship between the multichannel print head portion of an LTT station and the substrate during the process of fabricating OLED displays;  
         [0015]      FIG. 2A  illustrates an expanded view of detail A of  FIG. 1  showing an ideal swath-to-swath seam;  
         [0016]      FIG. 2B  illustrates a cross-sectional view taken along the lines  2 - 2  of  FIG. 2A ;  
         [0017]      FIG. 3A  illustrates an expanded view of detail A of  FIG. 1  showing a first example of a misaligned swath-to-swath seam;  
         [0018]      FIG. 3B  illustrates a cross-sectional view taken along lines  3 - 3  of  FIG. 3A ;  
         [0019]      FIG. 4A  illustrates an expanded view of detail A of  FIG. 1  showing a second example of a misaligned swath-to-swath seam;  
         [0020]      FIG. 4B  illustrates a cross-sectional view taken along the lines  4 - 4  of  FIG. 4A ;  
         [0021]      FIG. 5A  illustrates an expanded view of detail A of  FIG. 1  showing a third example of a misaligned swath-to-swath seam;  
         [0022]      FIG. 5B  illustrates a cross-sectional view taken along the lines  5 - 5  of  FIG. 5A ;  
         [0023]      FIG. 6  shows a flow diagram of a method of an initial OLED display fabrication using an LTT process in accordance with the invention;  
         [0024]      FIG. 7  shows a flow diagram of a method of real-time process control for the fabrication of OLED display devices using an LTT process in accordance with the invention; and  
         [0025]      FIG. 8  shows a flow diagram of a method of continuous process monitoring and control for the fabrication of OLED display devices using an LTT process in accordance with the invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0026]     The present invention is a method of utilizing the inherent and unique swath-to-swath physical characteristics of an OLED display device formed with an LTT process  100 , whereby these unique swath-to-swath physical characteristics are optically observed and analyzed for the purpose of verifying initial system setup, real-time process control, and continuous process monitoring. The methods of analyzing the physical characteristics of an OLED display device in accordance with the invention provide a way of ensuring and maintaining a high-quality fabrication process for OLED displays.  
         [0027]     For a better understanding of the invention,  FIGS. 1, 2A ,  2 B,  3 A,  3 B,  4 A,  4 B,  5 A, and  5 B below are provided for background, while subsequent  FIGS. 6, 7 , and  8  relate to the specific embodiments of the invention.  
         [0028]      FIG. 1  illustrates an example of a laser thermal transfer process, or LTT process  100 , during the process of fabricating OLED displays. LTT process  100  includes a conventional substrate  110  formed of, for example, glass, upon which an array layout of a plurality of pixel locations  112  is shown. LTT process  100  further includes a multichannel laser thermal print head  114  wherein a plurality of channels  1  through n of multichannel laser thermal print head  114  are each representative of a laser beams  116 ; thus, a plurality of laser beams  116  are generated. Further details of an LTT station are found in commonly assigned U.S. patent application Ser. No. ______ filed ______, by Daniel D. Haas et al., entitled ______, the disclosure of which is herein incorporated by reference. However, a summary of the operation of LTT process  100  as shown in  FIG. 1  is provided below.  
         [0029]     Multichannel laser thermal print head  114  is a conventional laser thermal print head that receives a single laser beam input (not shown) that is subsequently split into multichannels, for example,  256  channels, for generating output laser beams  116 . Multichannel laser thermal print head  114  permits for individual control of each channel, thereby providing on/off control of each individual laser beam  116 . The multichannel laser thermal print head  114  can, for example, be a Gen III KPG LT print head manufactured by Kodak Polychrome Graphics (Norwalk, Conn.) having 256 channels, a power range of between  16  and 24 watts, and an output wavelength of 808 nm. Multichannel laser thermal print head  114  is mounted upon a motion control system (not shown) that provides multichannel laser thermal print head  114  with precision X, Y, and theta (Θ) motion relative to substrate  110 . A donor (not shown) formed of a transparent substrate atop which is deposited an organic transfer layer, typically formed of electroluminescent organic material, is physically arranged between multichannel laser thermal print head  114  and substrate  110 .  
         [0030]     Although those skilled in the art will appreciate that a mix of pixel colors are possible, for simplicity, the operation of LTT process  100  is described with the assumption that all pixel locations  112  are of one color, for example, pixel locations  112  are all red, all green, or all blue. In operation, the input laser source that feeds multichannel laser thermal print head  114  is activated, thereby generating selected laser beams  116  based upon the predefined pattern array of pixel locations  112 , such as shown in  FIG. 1 . Laser beams  116  impinge upon the donor in this predefined pattern as multichannel laser thermal print head  114  sweeps across substrate  110  in a fast scan direction  115  as shown in  FIG. 1 . The conversion of the energy of laser beams  116  to heat sublimates the organic material of the donor, thereby vaporizing the organic material and depositing the organic material in the desired pattern upon substrate  110 .  
         [0031]     Since, in this example, the width of substrate  110  is greater than the width of multichannel laser thermal print head  114 , multichannel laser thermal print head  114  must make multiple passes to expose the entire area of substrate  110 . With continuing reference to  FIG. 1 , multichannel laser thermal print head  114  is initially positioned toward one edge of substrate  110  at step  117  and sweeps in the fast scan direction  115  along substrate  110 , thereby depositing a first swath  118  of organic material. Subsequently, multichannel laser thermal print head  114  is stepped the full width of multichannel laser thermal print head  114  in a direction perpendicular to the fast scan direction  115  to step  119  and again sweeps in the fast scan direction  115  along substrate  110 , thereby depositing a second swath  120  of organic material, which abuts an edge of swath  118 . Lastly, multichannel laser thermal print head  114  is stepped again the full width of multichannel laser thermal print head  114  in a direction perpendicular to the fast scan direction  115  to step  121  and again sweeps in the fast scan direction  115  along substrate  110 , thereby depositing a third swath  122  of organic material, which abuts an edge of swath  120 . In all cases, the appropriate channels, i.e., laser beams  116 , are activated in a manner that correlates to the width of swath  118 , swath  120 , or swath  122 , and to the desired pattern of pixel locations  112 .  
         [0032]     In this example, the boundaries of swath  118 , swath  120 , and swath  122  fall in the non-pixel region (i.e., between columns of pixel locations  112 ). However, it is noted that these swath boundaries, or “seams”, can fall anywhere across the width of substrate  110 , even within the pixel regions.  FIGS. 2A, 2B ,  3 A,  3 B,  4 A,  4 B,  5 A, and  5 B below show an expanded view of a detail A of  FIG. 1  and illustrate possible characteristics of a swath-to-swath boundary that are an indication of the process quality. These swath-to-swath boundary characteristics can be monitored via visual inspection using standard optical equipment. Such inspection equipment can include an Olympus Provis Research microscope equipped with fluorescent light at wavelengths of 365 and 470 nm and an instrumented stage with controlling hardware and software as well as image processing software. Both the instrumented stage and image processing software can be provided by Media Cybernetix, for example Image Pro software and Stage Pro software. It should be noted that this embodiment describes an optical inspection process. Other detection techniques such as, but not limited to capacitive measurements or spectroscopic ellipsometry could be used, as well.  
         [0033]      FIG. 2A  illustrates an expanded view of detail A of  FIG. 1  showing an ideal swath-to-swath seam  222  between swath  118  and swath  120 . More specifically, this expanded view shows that swath  118  is formed of an organic layer  210  and that swath  120  is formed of an organic layer  212 . Organic layer  210  is bounded by an edge  214  along the fast scan direction and an edge  216  perpendicular to the fast scan direction  115 . Similarly, organic layer  212  is bounded by an edge  218  along the fast scan direction  115  and an edge  220  perpendicular to the fast scan direction  115 . The boundary between edge  214  of organic layer  210  and edge  218  of organic layer  212  forms seam  222 .  
         [0034]      FIG. 2B  illustrates a cross-sectional view taken along the lines  2 - 2  of  FIG. 2A . With reference to  FIGS. 2A and 2B , it is shown that there is no overlap of or gap between edge  214  of organic layer  210  and edge  218  of organic layer  212 , thereby forming a seam  222  where edge  214  of organic layer  210  and edge  218  of organic layer  212  perfectly abut. Furthermore, edge  216  of organic layer  210  and edge  220  of organic layer  212  are likewise perfectly aligned at seam  222  along a line perpendicular to the fast scan direction. A device with such swath boundaries would exhibit minimal swath boundary image artifacts.  
         [0035]      FIG. 3A  illustrates an expanded view of detail A of  FIG. 1  showing a first example of a misaligned swath-to-swath seam  222  between swath  118  and swath  120 .  FIG. 3B  illustrates a cross-sectional view taken along the lines  3 - 3  of  FIG. 3A . With reference to  FIGS. 3A and 3B , it is shown that there is an overlap  310  formed by edge  214  of organic layer  210  overlapping edge  218  of organic layer  212 , thereby forming a seam  222  where edge  214  of organic layer  210  and edge  218  of organic layer  212  do not perfectly abut. However, edge  216  of organic layer  210  and edge  220  of organic layer  212  are perfectly aligned at seam  222  along a line perpendicular to the fast scan direction. A device with such swath boundaries would exhibit swath boundary image artifacts such as dark stripes if said boundaries occur within a pixel location  112 .  
         [0036]      FIG. 4A  illustrates an expanded view of detail A of  FIG. 1  showing a second example of a misaligned swath-to-swath seam  222  between swath  118  and swath  120 .  FIG. 4B  illustrates a cross-sectional view taken along the lines  4 - 4  of  FIG. 4A . With reference to  FIGS. 4A and 4B , it is shown that there is a gap  410  formed between edge  214  of organic layer  210  and edge  218  of organic layer  212 , thereby forming a seam  222  where edge  214  of organic layer  210  and edge  218  of organic layer  212  do not perfectly abut. However, edge  216  of organic layer  210  and edge  220  of organic layer  212  are perfectly aligned at seam  222  along a line perpendicular to the fast scan direction  115 . A device with such swath boundaries would exhibit swath boundary image artifacts such as bright stripes if said boundaries occur within a pixel location  112 .  
         [0037]      FIG. 5A  illustrates an expanded view of detail A of  FIG. 1  showing a third example of a misaligned swath-to-swath seam  222  between swath  118  and swath  120 .  FIG. 5B  illustrates a cross-sectional view taken along the lines  5 - 5  of  FIG. 5A . With reference to  FIGS. 5A and 5B , it is shown that there is no overlap of or gap between edge  214  of organic layer  210  and edge  218  of organic layer  212 , thereby forming a seam  222  where edge  214  of organic layer  210  and edge  218  of organic layer  212  perfectly abut. However, edge  216  of organic layer  210  and edge  220  of organic layer  212  are not perfectly aligned at seam  222  along a line perpendicular to the fast scan direction, thereby forming an offset  510 . A device with such swath boundaries would exhibit swath boundary image artifacts if said boundaries occur within a pixel location  112 . The resulting image artifacts would involve incomplete coverage with organic material of various pixel locations  112 .  
         [0038]     The swath-to-swath characteristics as described above in  FIGS. 2A, 2B ,  3 A,  3 B,  4 A,  4 B,  5 A, and  5 B are illustrative in nature; any combination of overlap  310 , gap  410 , or offset  510  is possible together with other structural characteristics along seam  222 . For example, in the case in which seam  222  (ideal or otherwise) falls within pixel location  112 , a discontinuity in the light emission of the affected pixel is observable. All such characteristics/defects are observable and measurable with standard optical instrumentation and are an indicator of process quality. Furthermore, these inherent structural swath-to-swath characteristics, such as those described in  FIGS. 2A, 2B ,  3 A,  3 B,  4 A,  4 B,  5 A, and  5 B, are unique to an LTT process  100  using a multichannel laser thermal print head  114 , such as LTT process  100 . Thus, the manufacturing process of an OLED display can be determined by simple visual observation. For example, an OLED display manufactured using a shadow mask deposition process does not possess these same structural characteristics, particularly those characteristics associated with swaths.  
         [0039]     Alternately, the swath-to-swath characteristics as described above in  FIGS. 2A, 2B ,  3 A,  3 B,  4 A,  4 B,  5 A, and  5 B are illustrative in nature; any combination of overlap  310 , gap  410 , or offset  510  is possible together with other structural characteristics along seam  222 . For example, in the case in which seam  222  (ideal or otherwise) falls outside of a pixel location  112 , the emissions in response to the appropriate wavelength of light enable the observation of the seam. Such observations would require examination of the substrate following the deposition step and prior to further processing of the device. All such characteristics/defects are observable and measurable with standard optical instrumentation and are an indicator of process quality. Furthermore, these inherent structural swath-to-swath characteristics, such as those described in  FIGS. 2A, 2B ,  3 A,  3 B,  4 A,  4 B,  5 A, and  5 B, are unique to an LTT process  100  using a multichannel laser thermal print head  114 , such as LTT process  100 . Thus, the manufacturing process of an OLED display is determined by a simple visual observation. For example, an OLED display manufactured using a shadow mask deposition process does not possess these same structural characteristics, particularly those characteristics associated with swaths.  
         [0040]      FIG. 6  shows a flow diagram of a method  600  of initial OLED display fabrication using an LTT process in accordance with the invention. Method  600  is suitable for use in the initial system setup for verifying the functionality of a raster image processor (RIP), for verifying proper control software implementation (proper CAD file-to-print head control conversion), for verifying positioning accuracy of the equipment, and for verifying proper equipment operation. Method  600  includes the following steps:  
         [0041]     In step  610 , a CAD file associated with a given OLED display device is received from a designer and processed with conventional methods such as parsing and design rule checking. Optionally, the CAD file can include data for forming a test pattern upon the OLED display device. Method  600  proceeds to step  615 .  
         [0042]     In step  615 , the CAD file is converted to a file format suitable for input to an LTT print head, such as multichannel laser thermal print head  114  of LTT process  100  ( FIG. 1 ). More specifically, a CAD file representing a given OLED display is converted via the RIP to an image file that provides input to LTT process  100 . For example, the process for converting the CAD file to a print head input file can include converting to a binary map, followed by creating an image file, followed by generating a corrected binary map and a machine instruction file, which is subsequently fed into LTT process  100 . Method  600  proceeds to step  620 .  
         [0043]     In step  620 , if available, equipment characterization data is applied to LTT process  100 . In this case, the corrected binary map and machine instruction file are modified to reflect the characteristics of the manufacturing equipment. Method  600  proceeds to step  625 .  
         [0044]     In step  625 , the OLED display device is fabricated using an LTT process such as LTT process  100  according to the specifications of the CAD file received in step  610 . This OLED display device can optionally include a test pattern printed thereon. Method  600  proceeds to step  630 .  
         [0045]     In step  630 , the finished OLED display device is optically inspected using conventional optical instrumentation, such as an Olympus Provis Research microscope equipped with fluorescent light at wavelengths of  365  and  470  nm and an instrumented stage with controlling hardware and software as well as image processing software. Both the instrumented stage and image processing software can be provided by Media Cybernetix, for example Image Pro software and Stage Pro software. Optical data is converted via image processing software and custom software into data, which characterizes the fabricated OLED display device. This data is used by, for example, a controller associated with LTT process  100 . The optical data includes information, for example, relating to the physical characteristics of the swath-to-swath boundary (seam  222 ), variations of which are described in reference to  FIGS. 2A, 2B ,  3 A,  3 B,  4 A,  4 B,  5 A, and  5 B. Method  600  proceeds to step  635 .  
         [0046]     In step  635 , a user or software application analyzes the optical data generated in step  630  for all phases of the fabrication process of the OLED display device. Examples of data analysis include analysis of any misregistration between the transfer area relative to the target area, i.e., verifying the corner locations of the transfer area relative to the corner locations of a sampling of pixel locations  112 ; and analysis of the swath boundaries, i.e., identifying and verifying the locations and physical characteristics of swath overlap, gap or offset. Method  600  proceeds to step  640 .  
         [0047]     In decision step  640 , based upon the optical data analysis of step  635 , a user or software application determines whether the quality of the physical characteristics of the fabricated OLED display device is satisfactory. For example, are the swath overlap, gap or offset are sufficient to require correction. If no correction is deemed appropriate, method  600  ends. If correction is required, method  600  proceeds to step  645 .  
         [0048]     In decision step  645 , it is determined whether the poor results as indicated via the optical data analysis are due to a suspected hardware problem. The following are three examples, for illustration. In one case, a multichannel laser thermal print head  114  failure can be noted. Here, a lack of coverage can be detected in all swaths and can be associated with a failure of specific channels within the multichannel laser thermal print head  114 . In another case, a distortion can be gradually introduced during the creation of a display device. Should the vacuum chamber fail to maintain the vacuum level within the acceptable limits during the LTT process  100  for a substrate  110 , misregistration between the transfer area relative to the target area will change from swath to swath in accordance with the changes to the vacuum loading of the window through which the multichannel laser thermal print head  114  light passes. And finally, the third case involves a failure of the motion control system feedback system. Since this feedback system is utilized to drive the transfer of data to the multichannel laser thermal print head  114 , a disruption of this signal will cause a related disruption of organic deposition. For example, should the position feedback device have been damaged, or become misaligned, a region within the travel of the print head can experience a short distance during which the feedback signals dropout. Should this occur, the length in the fast scan direction shall be extended by a distance proportional to the number of dropouts and subsequent misregistration between the transfer area relative to the target area will demonstrate a consistent shift of the same magnitude. If yes, method  600  proceeds to step  655 . If no, method  600  proceeds to step  650 .  
         [0049]     In step  650 , adjustments are made to the equipment characterization data to accommodate the changing performance of the laser thermal transfer process. The resulting changes are then processed via the RIP and an adjusted image file is provided as input to LTT process  100 . Method  600  returns to step  620 .  
         [0050]     In step  655 , hardware diagnostics are performed on the equipment included in the LTT manufacturing process. Examples of potentially failed equipment include a system controller; an X, Y, and θ motion control system; a vacuum chamber and associated controls; a laser source and associated optical devices; and a print head, such as multichannel laser thermal print head  114 . Method  600  proceeds to step  660 .  
         [0051]     In step  660 , a user or software application interprets the results of the hardware diagnostics to determine whether a hardware failure is present. If yes, method  600  proceeds to step  665 . If no, method  600  proceeds to step  650 .  
         [0052]     In step  665 , a user or technician makes the appropriate hardware repair, thus eliminating the hardware failure and restoring the operable condition of LTT process  100 . Method  600  returns to step  625 .  
         [0053]      FIG. 7  shows a flow diagram of a method  700  of real-time process control for the fabrication of OLED display devices using an LTT process in accordance with the invention. Method  700  includes the following steps:  
         [0054]     In step  710 , an LTT process, such as LTT process  100 , is initiated for the continuous manufacturing of OLED display devices that are fabricated according to predetermined design specifications. More specifically, specifications are generated via a CAD file representing a given OLED display. The CAD file is then is converted via a RIP into an image file that provides input in the form of instructions that can be interpreted by LTT process  100 . Method  700  proceeds to step  715 .  
         [0055]     In step  715 , periodically during the manufacturing process a sample OLED display device is optically inspected using conventional optical instrumentation, such as listed above. Such inspection equipment can include an Olympus Provis Research microscope equipped with fluorescent light at wavelengths of 365 and 470 nm with controlling hardware and software as well as image processing software. The image processing software can be provided by Media Cybernetix, for example Image Pro software and Stage Pro software. Optical data associated with the characterization of this sample OLED display device is generated and stored in, for example, a controller associated with LTT process  100 . The optical data includes information relating to, for example, the physical characteristics of the swath-to-swath boundary (seam  222 ), variations of which are described in reference to  FIGS. 2A, 2B ,  3 A,  3 B,  4 A,  4 B,  5 A, and  5 B. Method  700  proceeds to step  720 .  
         [0056]     In step  720 , a user or software application performs real-time analysis of the optical data generated in step  715  for all phases of the fabrication process of the OLED display device. Examples of data analysis include analysis of the location of a test pattern in relation to a fiducial; analysis of any misregistration between the transfer area relative to the target area, i.e., verifying the corner locations of the transfer area relative to the corner locations of a sampling of pixel locations  112 ; and analysis of the swath boundaries, i.e., identifying and verifying the locations and physical characteristics of swath overlap, gap or offset. Method  700  proceeds to step  725 .  
         [0057]     In step  725 , based upon the optical data analysis of step  720 , a user or software application determines whether the quality of the physical characteristics of the fabricated OLED display device is satisfactory. For example, are the swath overlap, gap or offset are sufficient to require correction. If no correction is deemed appropriate, method  700  ends. If correction is required, method  700  proceeds to step  730 .  
         [0058]     In step  730 , real-time adjustments are made to LTT process  100  as warranted by the results of the optical data analysis. Examples of real-time process adjustments include, but are not limited to, adjusting the angle of the print head (i.e., multichannel laser thermal print head  114 ), making adjustments for mechanical thermal variations, recalibrating position sensors, recalibrating the print head and generating a new corrected binary map and metadata file. Method  700  then returns to step  710 .  
         [0059]      FIG. 8  shows a flow diagram of a method  800  of continuous process monitoring and control for the fabrication of OLED display devices using an LTT process in accordance with the invention. Method  800  can be differentiated from method  700  in that method  700  provides for correcting the manufacturing process during production of the OLED device, while method  800  provides for correcting the manufacturing process after production of the OLED device. In both cases correcting the manufacturing process is prompted by the determination that the overlap, gap or offset were sufficient to require manufacturing process correction. Method  800  includes the following steps:  
         [0060]     In step  810 , an LTT process, such as LTT process  100 , is initiated for the continuous manufacturing of OLED display devices that are fabricated according to predetermined design specifications. More specifically, specifications are generated via a CAD file representing a given OLED display. The CAD file is then is converted via a RIP into an image file that provides input in the form of instructions that can be interpreted by LTT process  100 . Method  800  proceeds to step  815 .  
         [0061]     In step  815 , periodically throughout the manufacturing process a sample OLED display device is selected and optically inspected using conventional optical instrumentation. Such equipment can include, for example, a high-resolution Sony CCD camera equipped with fluorescent light at wavelengths of  365  and  470  nm and image processing software provided by Media Cybemetix, for example Image Pro software or IMAQ provided by National Instruments. Optical data associated with the characterization of this sample OLED display device is generated and stored in, for example, a controller associated with LTT process  100 . The optical data includes information relating to, for example, the physical characteristics of the swath-to-swath boundary (seam  222 ), variations of which are described in reference to  FIGS. 2A, 2B ,  3 A,  3 B,  4 A,  4 B,  5 A, and  5 B. Method  800  proceeds to step  820 .  
         [0062]     In step  820 , a user or software application analyzes the optical data generated in step  815  for all phases of the fabrication process of the OLED display device. Examples of data analysis include analysis of the location of a test pattern in relation to a fiducial; analysis of any misregistration between the transfer area relative to the target area, i.e., verifying the corner locations of the transfer area relative to the corner locations of a sampling of pixel locations  112 ; and analysis of the swath boundaries, i.e., identifying and verifying the locations and physical characteristics of swath overlap, gap or offset. Method  800  proceeds to step  825 .  
         [0063]     In step  825 , based upon the optical data analysis of step  820  over time, a user or software application identifies trends within the fabrication process that adversely affect the quality of the fabricated OLED display devices and thus warrant adjustments within the fabrication process. For example, trends in swath overlap, gap or offset can be identified. Other trends can be identified that indicate a gradual deterioration of some phase of the fabrication process, such as a gradual deterioration of the laser source, the print head, or the alignment system or changes related to trends in system temperature or vacuum levels. Alternately a trend can be found to occur during the creation of a single substrate. If process adjustments are needed, method  800  proceeds to step  830 . If not, method  800  ends.  
         [0064]     In step  830 , adjustments are made to LTT process  100  as warranted by the results of the optical data analysis. Examples of process adjustments include, but are not limited to, replacing or calibrating the print head (i.e., multichannel laser thermal print head  114 ), selecting another RIP file, adjusting the gap between substrate  110  and multichannel laser thermal print head  114 , adjustment to machine control parameters such that parameters which impact trends occurring within the manufacture of one substrate can be modified such that an optimal distribution of visual artifacts is achieved, and calibrating the alignment system. Method  800  then returns to step  810 .  
         [0065]     Methods  600 ,  700 , and  800  of the present invention can generally apply to any LTT printing deposition process used, for example, for thick film circuitry deposition, where a multichannel print head deposition process is used in lieu of other well known deposition processes, such as a shadow mask process.  
         [0066]     The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.  
         [heading-0067]     Parts List  
         [none]    
       
           100  LTT process  
           110  substrate  
           112  pixel locations  
           114  multichannel laser thermal print head  
           115  fast scan direction  
           116  laser beams  
           117  step  
           118  swath  
           119  step  
           120  swath  
           121  step  
           122  swath  
           210  organic layer  
           212  organic layer  
           214  edge  
           216  edge  
           218  edge  
           220  edge  
           222  seam  
           310  overlap  
           410  gap  
           510  offset  
           600  method  
           610  block  
           615  block  
           620  block  
           625  block  
           630  block  
           635  block  
           640  block  
           645  block  
           650  block  
           655  block  
           660  block  
           665  block  
           670  method  
           710  block  
           715  block  
           720  block  
           725  block  
           730  block  
           800  method  
           810  block  
           815  block  
           820  block  
           825  block  
           830  block

Technology Category: 5