STRUCTURES AND METHODS FOR CONTROLLING CONTAMINATION OF PIXELS NEAR SEALS IN AMLCD TILES

Abstract: In an AMLCD display tile, the rubbed polyimide alignment layers determine the stable polarization state of the liquid crystals under zero electric field conditions. When these alignment layers on pixels are contaminated by the low molecular weight component of the epoxy seal at or near the seal front, visible defects in the AMLCD display occur. In tiled displays, the seal is positioned in the same area as close to the pixels (203) as possible without contaminating them. Unique methods for controlling the seal and its formation to decrease or eliminate the aforementioned contamination (202) are the subject of this invention. A high quality seal front is provided with controlled position of the seal inner perimeter (207) for narrow seals applied to AMLCD tiles.

Description: STRUCTURES AND METHODS FOR CONTROLLING CONTAMINATION OF PIXELS NEAR SEALS IN AMLCD TILES Related Patent Applications: This application is a continuation of U.S. provisional application Serial No. 60/177,448. This application is related to co-pending United States patent applications Serial Nos . 09/369/465, filed August 6, 1999; Serial No. 09/368,921, filed August 6, 1999; and Serial No. 60/153,962 filed September 15, 1999; as well as to Serial No. 08/949,357, filed October 14, 1997, now issued as United States Patent No. 5,963,281. Field of the Invention: This invention relates to design structures, materials and methods for fabricating active matrix liquid crystal display (AMLCD) tiles for assembly into tiled, flat panel displays having visually imperceptible seams and, more particularly, to methods for creating thin, inner perimeter seals for AMLCD tiles such that contamination of pixels adjacent such seams is minimized. BACKGROUND OF THE INVENTION There are many requirements for designing and processing tiled flat panel displays that operate with a visually seamless appearance. The optical design parameters and the mechanical and electrical design parameters have been disclosed in detail in United States Patent No. 5,661,531 and in co-pending United States patent applications Serial Nos. 09/369,465 and 09/368,921. All of these references teach that a plurality of tiles can be joined together to form a large, flat .panel display that has a seamless characteristic. In other words, the seams disposed between the tiles are visually imperceptible to a viewer. One of the most significant requirements for achieving a seamless appearance across the seams between neighboring tiles relates to the pitch between pixels across the seam. The pitch between pixels on either side of a seam must be substantially equal to the pixel pitch within the central regions of the tiles. The tolerance level of seam defects to the eye is very dependent on the viewing distance, which in turn is dependent on the pixel pitch. Large pixel pitches and smaller than normal aperture ratios (i.e., the ratio of light-emitting to dark space within the pixel) allow more space for the seam components. The seal inner perimeter (SIP) tolerance must allow for waviness of the seal front near the pixels for the two neighboring tiles as well as other tolerance factors discussed hereinbelow. Waviness is the dimensional variation of the seal edge from a straight line. The seal edge characteristics depend on: 1) the seal material; 2) the pre-cure condition; 3) the lamination and cure process; 4) the panel surface structure; and also 5) the optimal design of the panel surface structure. The seal material is a filled, two part epoxy with glass spacers added for cell gap control and reactive and flow control solvents added for flow and curing enhancement . The formation of the seal results in an inner seal edge with three distinct areas. The bulk of the formed seal is predominantly "filled" epoxy. The edges of the seal contain a "clear" region, which is made up of lower molecular weight, unfilled epoxy, squeezed forward during the lamination and cure process. Beyond the seal edge front, a very low molecular weight combination of residual solvent and epoxy wets the liquid crystal (LC) alignment layer, thereby creating a misalignment of the LC. This area is referred to as the "defect area", and can result in undesirable visible artifacts if positioned near or on an active pixel. These seal characteristics dominate the design constraints for minimizing the periphery of an LC cell. United States Patent No. 5,963,281 and co-pending patent application Serial No. 09/369,465 disclose detailed designs and methods for decreasing the waviness of the seal front and an accompanying defect area. These designs utilize dams, channels between dams and wetting structures to help control the formation of the seal front in the SIP area. Even so, these designs leave an allocation of approximately 50 microns insurance for the defect area within each SIP. This amounts to a 100 micron portion of the pixel pitch which, in current designs with pixel pitches of 1 mm, amounts to 10% of the pitch. This decreases the aperture ratio of the pixels by approximately 40% in a 2 X N tile array and approximately 20% in a 1 X N tiled array. Seams appear only in one direction in the 1 X N array.. Because the brightness of the display is directly dependent upon the pixel aperture ratio, it is important to maximize the aperture ratio. One way to accomplish this is to decrease the size of the defect area. As the demand for large tiled displays with higher resolution increases, the seam areas must be decreased in order to maintain a reasonable aperture ratio. This seam dimension decrease results in a need to modify the panel structure near the edge thereof, the epoxy composition and the process for manufacturing the display. The present invention provides methods for decreasing defect areas at the seal inner edge within the SIP, thereby creating a narrower finished tile edge seal . Such improvements in seal control allow aperture ratios to be Z rt X rt X Φ Ω 0 0 rt ii 0 X-x 0 Hi CQ Φ 0 X-x < 0 X-x 0 3 Φ ø ø i X-x 0 Ω ø rt μ- 0 ø rt tr φ Ω X-x φ 0 ti may be run with a predetermined width with less than 5% variability without further volume measurement and process adjustments . A pre-bake of the seal material in the range of 90 degrees C for a short time (e.g., approximately 15 minutes) cross links the polymer sufficiently for supporting the assembly of the two substrates, CF and TFT, in readiness for lamination. Prior to placement and registration of the two substrates, the desired spacer spheres, being approximately 5 μm diameter, create the LC cell gap and are distributed over the TFT substrates, the seal material having been preferably dispensed on the CF substrate. Moreover, a second set of spacer spheres or rods (preferably glass) is mixed in the epoxy prior to dispensing. The second set of spacers (preferably spheres) is of a complementary diameter to minimize cell gap variations near the seal . The TFT substrate is then registered and laminated to the CF substrate. During this process, the seal material is extruded from a wet width to a final width as the TFT and CF plates are squeezed or laminated together with a selected force or vacuum. For example, if the wet width is 200 microns, and the wet height of the seal material averages 20 microns, a seal 800 microns wide results after lamination, when 5 micron spacers are used. In this example, the lamination process causes the seal inner edge or front to move 300 microns toward the pixels. During the lamination process, the seal front becomes wavy, and a clear, unfilled, polymeric material appears in front of the silica-filled polymer material. Some wetting of the surfaces by the reactive solvent results in the defect area (not easily detectable) appearing in front of the clear polymeric material. Thus, in the defect area, the solvent is thin and merely wets the surfaces without bridging the gap therebetween. If and when this contaminant reaches the pixels near the seam, a visible defect appears. The character of the defect may be a lack of electronic activation of a portion of the contaminated pixels (i.e., continuously lit portions of sub-pixels) or partially-lit larger areas containing many pixels. The defect area is then easily observed in a completed AMLCD panel filled with liquid crystal material by observing the panel when it is placed between uncrossed polarizers (black state) . The defect area appears lit when tested at these conditions. None of the control parameters listed above, except viscosity and solvent content, can be used effectively to decrease the tendency for this type of defect. However, the use of dams and flow-directing structures may be employed to limit the defect area to less than 50 microns. In comparison, normal practice produces defect areas as large as 1000 microns. United States Patent No. 5,963,281 and patent application Serial Nos. 09/369,465 and 09/368,921 disclose examples of dams and/or channel like structures that direct the flow of the solvent at the front of the seal on the CF substrate to achieve defect areas as small as 50 μm . However, a further decrease in the defect area to substantially less than 50 μm is desired to achieve a narrow seal width for tiling high resolution, AMLCD flat panel displays (FPDs) . The current 50 micron insurance area between the dams and pixels constitutes approximately 25% of the allowed seam width. Consequently, this area has a large effect on the pixel design (e.g., decreasing aperture ratio, increasing pixel size, or decreasing resolution) for tiled displays. SUMMARY OF THE INVENTION The present invention teaches methods for decreasing the size of the defect area at the seal front near the edge pixels at the SIP area on AMLCD tiles. The inventive methods allow the formation of extremely narrow perimeter seals on individual display tiles designed for assembly into tiled, flat panel displays (FPDs) . The methods of the instant invention work well with control structures such as dams and wetting structures. The individual, hermetically sealed tiles produced in accordance with the invention are suitable for use in tiled, flat panel displays having visually imperceptible seams. Consequently, it is an object of the invention to provide process methods which decrease the defect area, thereby allowing the production of narrower seals with controlled SIPs. It is another object of the invention to provide optimized seal material by modifying the molecular weight distribution of the reactive solvent material in such a manner as to decrease the proportion of short chain length molecules . It is a further object of the invention to design a seal material having a molecular weight distribution readily manufacturable by an adhesive material vendor at a reasonable cost. It is an additional object of the invention to modify the "B stage" temperature profile in the process sequence to allow selective diffusion of the lower molecular weight chains in the reactive and volatile solvents, thus allowing the chains time to bond to a reactive epoxy termination prior to panel lamination or to be evaporated. It is a still further object of the invention to decrease the fraction of reactive solvent component in the seal material. It is yet another object of the invention to improve seal formation and minimize pixel contamination by reducing the amount of volatile solvent in the seal material . It is a still further object of the invention to form a narrow (smaller volume seal) in the range of 500 to 700 μm width which exhibits a minimum of waviness. It is an additional object of the invention to substitute glass spheres for glass rods to be used as spacers in the seal material . It is also an object of the invention to reduce the SIP dimension from 185 to 135 μm. BRIEF DESCRIPTION OF THE DRAWINGS A complete understanding of the present invention may be obtained by reference to the accompanying drawings, when considered in conjunction with the subsequent detailed description, in which: FIGURE 1 is a graph showing seal waviness as a function of seal width, with and without dams and wetting control structures on the color filter; FIGURE 2a is a top view of a typical epoxy seal between the CF and TFT substrates near pixels; FIGURE 2b is a sectional view of the epoxy seal shown in FIGURE 2a; FIGURE 3 is a top view of a typical epoxy seal between the CF and TFT substrates near pixels, showing selective wetting of the epoxy, creating a defect area along an interconnection line on a TFT substrate and along the edge of three sub-pixels; FIGURE 4 is a top view of a typical epoxy seal between the CF and TFT substrates near pixels in an SDTV FPD, showing the relationship between dams and wetting structures designed into the CF film layers to control the dimensions of the seal inner perimeter; and FIGURE 5 is a top view of a typical epoxy seal between the CF and TFT substrates near pixels in an HDTV FPD, showing the relationship between dams and wetting structures designed into the CF thin films to control the dimensions of the SIP for an alternate, HDTV/XGA design. For purposes of both clarity and brevity, like elements and components will bear the same designations and numbering throughout the FIGURES . DESCRIPTION OF THE PREFERRED EMBODIMENT Generally speaking, the invention features apparatus and methods for manufacturing AMLCD display tiles wherein the seal inner perimeter (SIP) width is controlled and a defect area at or near the seam regions of the display tiles is minimized. AMLCD tile perimeter seals are formed in accordance with the present invention from seal materials having lower molecular weight components than material used in the prior art. In addition, the adhesive mixture has a portion of low viscosity cross linking solvent. Surface wetting occurs at the leading edge of the seal material as the seal is squeezed out during lamination of the color filter (CF) and the thin-film transistor (TFT) substrates. This solvent is designed to be assimilated into the cross linking matrix of epoxy molecules making up the seal. It is a reactive cross linking solvent for the epoxy, designed to be mixed in proportions so as to provide a robust cross linked epoxy matrix after curing. Before curing (cross linking) , the combination of the reactive solvent and the adhesive decrease the viscosity of the seal and provide the wetting ability of the adhesive epoxy seal. In spite of structure designed to control the spread of the material, the leading edge of the material advances unevenly, leaving at least some degree of edge waviness . The degree of edge waviness increases with the width of the seal, increasing approximately 15 microns for every 100 microns increase in seal width, for seal widths in the range of 500 to 800 microns. FIGURE 1 is a graph showing seal edge waviness as a function of seal width and of the absence or presence of seal material flow control structures such as dams and dam separation channels. The seal material generally consists of an epoxy base mixed with a solvent which has a reactive component proportionally mixed with some volatile compound to achieve a desired viscosity. In addition, the mixture usually contains a substantial amount of finely ground silica, and glass spacer spheres or rods. The seal material may be deposited by screening or dispensing in the desired patterns from a small orifice, such as a pen, hollow needle, or syringe. Deposition is preferably on the CF substrates although deposition on the TFT, either alone or in addition to the CF, is also possible. After deposition, the seal is pre-baked and dried to a desired level of polymerization, usually referred to as "B" stage. Referring now to FIGURES 2a and 2b, there are shown top and sectional views, respectively, of a region of the epoxy seal near a pixel at the edge of an AMLCD panel . After lamination (i.e., assembling the CF to the TFT and compressing the " sandwich" ) and curing, the seal edge appears to be made up of three distinct components: a 10 (_ KJ O M ι-> in o in o in o in ø Hi 0 H φ 3 Φ ø rt μ- 0 ø Φ Pi < CQ μ- tr x- χ Φ 13 0 X-x > < 3 Φ ii CQ Φ ø X-x Hi ϋ O 0 rt 0 ϋ CQ φ ø μ- ø 0 Φ ϋ edge, by approximately 50 microns. Sometimes the contamination may run freely along some local feature, such as an interconnection line 206 on the TFT substrate 205, sometimes producing undesired visual effects or defect areas over entire pixels, and as much as several hundred microns or more near the inner edge of the seal . It has therefore been necessary in prior art seals to position the seal far away (e.g., more than 1 mm) from the pixels. This is the common practice for making notebook displays and the like. The commonly used process for laminating and curing the seal is to first prebake (partially cure or B stage) the seal in the range of 90 degrees C. This partially dries and also cross links some of the reactive solvent component to the epoxy molecules. The seal is then tacky and can be handled more easily. The substrates are then aligned to each other using fiducial marks for registration. With the increased viscosity of the seal due to prebake, the subsequent lamination process and flow of the seal material is an extrusion-like process requiring a combination of pressure and temperature to complete the sealing process. During the lamination process, the cell gap between CF and TFT plates closes to meet the spacer diameters without creating splash or voids. It is important that the two substrates are flat and parallel, providing a consistent cell gap in the seal area. If this is not the case, the seal extrusion will not be uniform in directional flow and the midpoint of the center of the seal width will shift from the predetermined desired position. To achieve the parallelism, CF structure is designed into the perimeter of the tile outside of the seal, equal in height to the CF in the center area of the tiles. Spacers for equal cell gap are used there as well as in the tile interior. The temperature during the lamination process is increased in a profiled oven to the range of 180 degrees C where the cure or cross linking of the seal material becomes complete. Commonly, the panel is then vacuum annealed before filling with the liquid crystal. During the vacuum annealing process, residual solvent can boil out if it is not fully cross linked into the epoxy matrix. In the invention, however, this step can be eliminated due to alternatives (composition, structure and method) developed to reduce the contamination at the front of the seal and thereby to decrease the defect area. Although the viscosity decreases exponentially with temperature, during the cure cycle the cross linking reaction progress counters this. The last molecules to cross link are the largest chains, while the smallest chains diffuse more rapidly in the epoxy matrix and find a reactive epoxy chain link for bonding. If the solvent molecules are in excess or do not find an epoxy bond, they are easily extruded ahead of the moving seal front by pressured permeation. That is, the lower viscosity solvent and lower molecular weight portion is preferentially extruded to the seal front . Thus the defect area in front of the seal edge is determined by the solvent component that is not effectively cross linked to the epoxy during the B staging or during the temperature ramp to achieve a final cure state during the lamination process. The contamination front is therefore the rapidly permeating component of the solvent or smallest molecular chain lengths of the molecular weight distribution in the solvent. Experiments have in fact shown that a smaller defect area will result if partial cures are used substantially below the commonly used prebake temperature of 90 degrees C. An approved process for bonding the reactive solvent is added to the process in the range of 50 degrees C. The reason for this is that the lower molecular weight components of the reactive solvent diffuse more rapidly than the higher molecular weight components at these lower temperatures. Thus, the lower molecular weight components selectively find and bond to the reactive epoxy molecular chain ends. This modification to the process also reduces the volatile solvent as well as the reactive solvent prior to the lamination process, thereby reducing the pressure driven permeation of the low molecular weight component, which causes the contamination at the seal front in the SIP area. AMLCD tile perimeter seals are formed in accordance with the present invention from the same materials as those used in the prior art. The component fractions, however, are different and are optimized in process to provide a smaller defect area. The two lowest molecular weight solvents that form in the seal front by pressure permeation during lamination (extrusion) must be decreased. The volatile solvent, which is added to the seal material to manage the viscosity for dispensing, should be minimized either in the formulation or by more complete drying prior to lamination. The reactive solvent must be accurately balanced to the molecular content of the base epoxy so that none is left over after the final curing reaction. For this to happen, a temperature hierarchy is used to optimize the ability of the reactive solvent molecules to diffuse throughout the base epoxy matrix and find enough reactive sites for complete bonding. Seal components are mixed in lots which are stored and used in manufacturing in a variety of practices. The solid filler material, generally Si0 2 , has a variety of particle sizes and surface areas and fractional content which are different from lot to lot and user to user. Furthermore, the polymer components are substantially variable in molecular reactivity determined by molecular content and thermal history. A further complication is that the processes of lamination in time and temperature, force, and seal front excursion vary with the particular design being manufactured. Therefore, the invention depends on a method of functional test to determine the defect area characteristics for the particular manufacturing process and design being practiced. The sequence is as follows: 1) determine the defect area at the seal front as described in the figures and discussed hereinabove for the particular materials, process, and tools for the desired design with predetermined seal width, cell gap, dams and wetting structures; and 2) minimize the defect area by one or more actions described hereinbelow. Several process methods can be implemented to decrease the defect area for implementation of narrower seals with controlled SIPs. First, there is the opportunity to modify the molecular weight distribution of the reactive solvent material by decreasing the proportion of short chain length molecules. Centrifuging of the material followed by decanting can be used to achieve an improved molecular weight distribution. Clearly, a specification for the reactive solvent should contain a molecular weight distribution with a cut off of the lowest chain lengths. These are modifications that can be implemented by the vendors of the seal adhesive components. Secondly, a staged temperature profile in the process sequence can be modified to contain a temperature stage in the range of 50 degrees C as well as a prebake typically at 90 degrees C, to allow selective diffusion of the lower molecular weight chains in the reactive solvent . This allows such lower molecular weight chains time to bond to a reactive epoxy termination or to be evaporated prior to lamination. Alternatively, an optimized prebake temperature time profile beginning at substantially lower temperatures than 90 degrees C may be used to selectively bond the lower molecular weight components fraction of the reactive solvent and also to increase the amount of solvent evaporated. Still another method of control is to decrease the fraction of reactive solvent component to preferably be in balance with the molecular epoxy content, rather than to produce an excess of solvent. Still another method of control is to reduce the volatile solvent so that none is left after prebake. As noted earlier, a complementary reduction of the defect area in the SIP at the front can be accomplished by dams, dam separations, and wetting structures previously disclosed in the aforementioned related issued patents and patent applications. However, to take advantage of the current invention on the seal process, the dams and wetting structures designed and processed into the CF are preferably located in an optimum position closer to the pixels which depends on the dimension of the defect area. This is most easily understood by citing an example wherein the finished tile and resultant SIP area is controlled to be a certain width, say 135 μm, as disclosed in copending patent application serial no. 09/490,776, filed January 24, 2000 and shown in FIGURE 5. Tiles are approximately dimensioned by making 1 3 tiled FPD arrays for HDTV and/or XGA resolution. In this case, the dams are located approximately 25 μm from the pixels as a buffer zone to prevent the contamination from reaching the pixel. This is a reduction of 25 microns over the dimensions used for the SDTV tiled FPD. The dams for the HDTV resolution are also narrower: about 20 microns and spaced apart about 25 microns, creating a channel in the CF S Pi 3 Z Φ Φ 0 X ø Hi X-x Φ φ Ω Φ Ω Ω tr i rt H 0 0 l-x Z rt ø 0 φ X ii 0 ii rt ø Φ Pi in 0 ø Pi μ- Φ Ul li rt μ- Φ Φ rt μ- <P X-x Q X 0 tr Φ 0 Φ ø rt Ω μ- H rt ii Φ rt Ul μ- Φ 0 0 < Pi μ- X-x φ Q rt < X-x Hi tr Φ • O ø ro ø ii CD rt 13 Ω ro ø ø 0 Hi li 0 ø Pi H ø ø Ω 0 X-x Pi φ Hi 0 I- 1 X-x ii Hi rt Φ μ- ø ro • X-x ø fi ιp rt Φ tt tr 0 0 i 0 Ω ø rt Φ rt i Ul tr μ- rt φ ø X CQ Φ 0 13 Φ 3 tB Ω ii 0 Φ 0 3 ø ø 3 Φ ø X-x 13 ø Hi CQ ø rt SD fi μ- Ω Z μ- ø rt Q CQ ø X-x 0 ii X-x 0 X-x μ- 0 ø tr 0 Z CQ φ Hi • Therefore, a modification to the sequential drawing of the seal is preferable to increase the strength by redundancy. Thus more than one seal width may be applied by sequential and continuous drawing of the seal to the wide seal sides . This procedure compensates for the removal of seal by cutting in the predetermined narrow seal sides. Redundancy is also used on the narrow seal sides to provide a supporting system during cutting. In the future, improved wetting structures are projected with multiple dams and channels that are designed to create greater capillary forces to control the solvent front as the seal is formed during lamination. These designs and processes may be optimized for adhesion strength by removing the weaker materials interfacing the seal. Thus the edge of the seal where it is cut may be selectively chosen from the material hierarchy. On the CF substrate the selection can be made to be one of polyimide, ITO, dielectric layer, or the substrate glass. In summary, a method for modifying the process by selecting a material and/or solvent ratio and adjusting the manufacturing process may be stated as a series of steps : 1) Mix seal adhesive to a predetermined composition and add spherical spacers of a first diameter; 2) Provide two glass substrates covered sequentially with ITO thin film and an alignment layer; 3) Deposit a seal of predetermined width around the outer edge of one of two glass substrates; 4) Prebake the seal at a predetermined temperature and time profile; 5) Deposit spherical spacers of a second diameter on the other surface with the desired diameter to meet a predetermined cell gap; 6) Laminate the two glass substrates together with predetermined force and/or vacuum; 7) Cure the seal with a predetermined temperature/time profile; 8) Fill the glass substrates with LC; 9) Place the substrates between crossed polarizers and inspect the defect area for desired dimensions; 10) If the defect area is larger than a predetermined specification, decrease the seal volume or the solvent proportion by a small decrement (one percent of solvent component) and proceed through steps (3) to (9) and repeat this cycle, decreasing solvent each time, until the predetermined specification is met; alternatively, if the defect is larger than the predetermined specification, increase the prebake time in step (4) by approximately 30% and repeat steps (2) to (9) , adding 30% time increments to the prebake in step (4) until the predetermined specification is met; alternatively, if the defect is larger than the predetermined specification, add a gel stage step in the range of 50 to 70 degrees C equal to prebake in time, and repeat this cycle increasing the gel stage time in equal increments until the predetermined specification is met; and 11) Standardize the aforementioned, optimized parameters for future displays. It is obvious that in a complex manufacturing operation such as assembling a tiled, flat panel display, the least intrusive changes to operations are preferable. The preferable step (10) changes the solvent cut of the seal material external to the assembly line, whereas alternative steps may also be substituted but may have a greater effect on the assembly line. Since other modifications are changes varied to fit particular operating conditions and environments or designs will be apparent to those skilled in the art, the invention is not considered limited to the examples chosen for purposes of disclosure, and covers changes and modifications which do not constitute departures from the true scope of this invention. Having thus described the invention, what is desired to be protected by letters patents is presented in the subsequently appended claims . WHAT IS CLAIMED IS:

Claims: 1. A method for producing active matrix liquid crystal display (AMLCD) tiles for use in a flat panel display, the steps comprising: a) producing a first AMLCD tile having predetermined materials in accordance with a predetermined process by the use of predetermined tools; b) determining and analyzing a defect area in said first AMLCD tile; c) improving one or more of said materials, said process and said tools in response to said determining and analyzing step (b) , in order to minimize said defect area and to optimize said AMLCD tile production; and d) producing a second, optimized AMLCD tile using one or more of said improved materials, improved process and improved tools. 2. The method for producing AMLCD tiles in accordance with claim 1, the steps further comprising: ■ e) standardizing said improved materials, improved process and improved tools for use in producing future AMLCD tiles. 3. The method for producing AMLCD tiles in accordance with claim 1, wherein said predetermined materials are used to form a seal, said predetermined seal material comprising: i) silica filled epoxy; ii) a reactive solvent; iii) a volatile solvent for viscosity control and cross linking; and iv) first spacers, having a first diameter, for controlling cell gap. 4. The method for producing AMLCD tiles in accordance with claim 3, further comprising: v) second spacers, having a second diameter complementary to said first spacer diameter, to minimize cell gap variations near said seal. 5. The method for producing AMLCD tiles in accordance with claim 4, wherein said first and second spacers comprise spherical spacers. 6. The method for producing AMLCD tiles in accordance with claim 4, wherein said second spacers comprise glass. 7. The method for producing AMLCD tiles in accordance with claim 1, further comprising flow control structures for regulating the quantity of said materials dispensed along a seal area of said AMLCD tiles. 8. The method for producing AMLCD tiles in accordance with claim 7, wherein said flow control structures are selected from the group of dams, channels between dams and wetting structures. 9. The method for producing AMLCD tiles in accordance with claim 8, wherein said flow structures are redesigned and optimized in accordance with said determining and analyzing step (b) . 10. The method for producing AMLCD tiles in accordance with claim 3, wherein said reactive solvent comprises a predetermined molecular weight and said steps further comprise: e) modifying the molecular weight distribution of said reactive solvent to decrease the proportion of short chain length molecules therein. 11. The method for producing AMLCD tiles in accordance with claim 3 , wherein said predetermined seal material is cured at said seal in a prebake procedure in accordance with a predetermined temperature profile for a predetermined curing time to allow selective diffusion of lower molecular weight chains in said reactive solvent, thus allowing said chains time to bond to said silica filled epoxy. 12. The method for producing AMLCD tiles in accordance with claim 11, wherein said improving step (c) comprises adjusting and optimizing said predetermined temperature profile. 13. The method for producing AMLCD tiles in accordance with claim 11, wherein said improving step (c) comprises adjusting and optimizing said predetermined curing time. 14. The method for producing AMLCD tiles in accordance with claim 3 , wherein said determining and analyzing step (b) comprises determining whether said defect area is larger than predetermined specifications therefor. 15. The method for producing AMLCD tiles in accordance with claim 14, wherein said improving step (c) comprises decrementally and repeatedly, if necessary, decreasing the volume of said seal . 16. The method for producing AMLCD tiles in accordance with claim 14, wherein said improving step (c) comprises decrementally and repeatedly, if necessary, decreasing the proportion of said reactive solvent. 17. The method for producing AMLCD tiles in accordance with claim 13, wherein said improving step (c) comprises incrementally and repeatedly, if necessary, increasing said prebaking time. 18. The method for producing AMLCD tiles in accordance with claim 11, wherein said determining and analyzing step (b) comprises determining whether said defect area is larger than predetermined specifications therefor, and further comprising the step of performing a gel stage substantially equal to said prebake in time but lower in temperature. 19. The method for producing AMLCD tiles in accordance with claim 3, wherein said seal is formed by producing a bead of said seal material the wet width cross section thereof being measured. 20. The method for producing AMLCD tiles in accordance with claim 3, wherein said seal is applied to a substrate by screening. 21. The method for producing AMLCD tiles in accordance with claim 3, wherein said seal is applied to a substrate by dispensing. 22. The method for producing AMLCD tiles in accordance with claim 21, wherein said seal material is dispensed by an implement having an orifice. 23. An active matrix liquid crystal display (AMLCD) comprising a plurality of tiles and seams therebetween, said AMLCD being produced by a process, the steps thereof comprising: a) producing a first AMLCD tile having a predetermined structure and having predetermined materials in accordance with a predetermined process; b) determining and analyzing a defect area in said first AMLCD tile; c) improving one or more of said materials, said process and said structure in response to said determining and analyzing step (b) , in order to minimize said defect area; and d) producing a second, optimized AMLCD tile using one or more of said improved materials, improved process and improved structure. 24. AMLCD in accordance with claim 23, the steps further comprising: e) standardizing said improved materials, improved process and improved structure for use in producing future, optimized AMLCD tiles. 25. The AMLCD in accordance with claim 23, wherein said predetermined materials are used to form a seal, said predetermined seal material comprising: i) silica filled epoxy; ii) a reactive solvent; iϋ) a volatile solvent for viscosity control and cross linking; and iv) first spacers, having a first diameter, for controlling cell gap. 26. The AMLCD in accordance with claim 25, further comprising: v) second spacers, having a second diameter complementary to said first spacer diameter, to minimize cell gap variations near said seal. 27. The AMLCD in accordance with claim 26, wherein said first and second spacers comprise spherical spacers. 28. The AMLCD in accordance with claim 26, wherein said second spacers comprise glass. 29. The AMLCD in accordance with claim 23, further comprising flow control structures for regulating the quantity of said materials dispensed along a seal area of said AMLCD tiles. 30. The AMLCD in accordance with claim 29, wherein said flow control structures are selected from the group of dams, channels between dams, and wetting structures. 31. The AMLCD in accordance with claim 30, wherein said flow control structures are redesigned and optimized in accordance with said determining and analyzing step (b) . 32. The AMLCD in accordance with claim 25, wherein said reactive solvent comprises a predetermined molecular weight and said steps further comprise: e) modifying the molecular weight distribution of said reactive solvent to decrease the proportion of short chain length molecules therein. 33. The AMLCD in accordance with claim 25, wherein said predetermined seal material is partially cured at said seal in a prebake procedure in accordance with a predetermined temperature profile for a predetermined time to allow selective diffusion of lower molecular weight chains in said reactive solvent, thus allowing said chains time to bond to said silica filled epoxy. 34. The AMLCD in accordance with claim 33, wherein said improving step (c) comprises adjusting and optimizing said predetermined temperature profile. 35. The AMLCD in accordance with claim 33, wherein said improving step (c) comprises adjusting and optimizing said predetermined curing time. 36. The AMLCD in accordance with claim 25, wherein said determining and analyzing step (b) comprises determining whether said defect area is larger than predetermined specifications therefor. 37. The AMLCD in accordance with claim 36, wherein said improving step (c) comprises decrementally and repeatedly, if necessary, decreasing the volume of said seal, thereby shifting the center of said seal material towards pixels of said AMLCD. 38. The AMLCD in accordance with claim 36, wherein said improving step (c) comprises decrementally and repeatedly, if necessary, decreasing the proportion of said reactive solvent. 39. The AMLCD in accordance with claim 35, wherein said improving step (c) comprises incrementally and repeatedly, if necessary, increasing said curing time. 40. The AMLCD in accordance with claim 33, wherein said determining and analyzing step (b) comprises determining whether said defect area is larger than predetermined specifications therefor, and further comprising the step of performing a gel stage substantially equal to said prebake in time but lower in temperature. 41. The AMLCD in accordance with claim 25, wherein said seal is formed by producing a bead of said seal material the wet width cross section thereof being measured after pre-baking thereof, and wherein the volume of said seal material is adjusted to fill said cell gap to a predetermined position near pixels of said AMLCD. 42. The AMLCD in accordance with claim 25, wherein said seal is applied to a substrate by screening. 43. The AMLCD in accordance with claim 25, wherein said seal is applied to a substrate by dispensing. 44. The AMLCD in accordance with claim 43, wherein said seal material is dispensed by an implement having an orifice.

Inventors: SERAPHIM DONALD P, SKINNER DEAN W, SERAPHIM, DONALD, P., SKINNER, DEAN, W.
Applicants: RAINBOW DISPLAYS INC, SERAPHIM DONALD P, SKINNER DEAN W, RAINBOW DISPLAYS, INC., SERAPHIM, DONALD, P., SKINNER, DEAN, W.
Application year: 2001
Main classification: G02F1
IPC codes: G02F1