Abstract:
A method of resizing a liquid crystal display (LCD) includes the steps of first determining a desired size for the LCD, thereby identifying an undesired portion of the LCD. Any tape automated bonding strips (TABs) corresponding to the undesired portions of the LCD are then removed. Any flex circuits, or portion thereof, corresponding to the undesired portion of the LCD are cut and removed. Any circuit boards, or portions thereof, corresponding to the undesired portion of the LCD are cut and removed. The display panel is cut to remove a portion of the display panel corresponding to the undesired portion of the LCD. Finally, the cut edge of the display panel is sealed.

Description:
RELATED APPLICATION 
     The present application claims the priority of U.S. Provisional Application No. 60/172,753, entitled Method of Resizing a Liquid Crystal Display, filed on Dec. 20, 1999, the entirety of which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to a liquid crystal display (LCD), and more particularly to a method of resizing an LCD. 
     2. Description of the Related Art 
     Liquid crystal displays (LCD) are well known throughout the art. An active matrix LCD includes row and column address lines and corresponding driving circuitry. This type of display is commonly known as an “X-Y active matrix type LCD.” The row and column address lines are typically driven from two to four sides of the LCD. That is, the row address lines are driven from one or two sides of the display and the column address lines are driven from one or two of the remaining sides of the display. In the case that two drivers are used for the row or column address lines, the lines are driven from opposing sides and are interdigitated. 
     The row and column address line driver chips are typically mounted on separate printed circuit boards disposed adjacent to the sides of the display panel and function to interface the driver chips with a central controller for controlling the output of the LCD. A flexible circuit assembly is often used for the driver chips. 
     FIG. 1 is a perspective view of one typical configuration of a conventional LCD. The LCD illustrated in FIG. 1 includes a display panel  10  and a plurality of flex circuits  11  and  14  that support row drivers  12  and column drivers  13 , respectively. The row and column drivers  12  and  13  supported on the flex circuits  11  and  14  are connected to the individual address lines (row or column) and extend to the edge of the display panel  10 . The flex circuits are typically orthogonal to the plane of the display panel  10  to minimize the additional border area required around the display. Circuit boards  15  and  16  and connectors  17  and  18  interface the driver chips to the central controller. 
     Another typical configuration for a conventional LCD includes individual driver TABs (tape automated bonding) along each of the sides of the LCD and providing a separate rigid circuit board adjacent each side of the display. Each circuit board interfaces the circuit board with the driver TABs mounted along the corresponding side of the display panel  10 . One such driver TAB is illustrated in FIG.  2 . The TAB  20  is mounted along an edge of the display panel  10  with the address lines electrically connected to the output leads  29  of driver TAB  20 . Window  25  is provided so that output lead support  32  may be mounted to the display panel  10  and base portion  21  can be bent orthogonally to the display panel  10 . The base portion  21  includes a plurality of copper input and output traces  31  and  29 , respectively. The driver chip  27  is electrically connected to input and output traces  31  and  29 , respectively. Input traces  31  receive input signals from the central controller via input connector  34 . 
     The conventional LCDs described above are typically available in various standard sizes. However, an intermediary manufacturer may find it necessary to reduce the size of, or resize, an LCD to conform to the precise specification requirements of the intended use of the LCD. For example, as illustrated in FIG. 3, the intermediary manufacturer may be required to reduce the size and/or change the aspect ratio of an LCD by physically cutting away the undesired portions  38  of the LCD, while maintaining the integrity of the desired portion  37 . In doing so, the LCD may optionally be converted from landscape mode to portrait mode, or vice versa. 
     However, resizing an LCD presents many obstacles due to its construction. The display panel  10  is a laminated glass structure, which includes a pair of opposing transparent glass plates sealed peripherally so as to define a planar cavity in which a liquid crystal layer is retained. When cutting the display panel  10  by scribing the glass plates, the lower plate (active plate) may be damaged by compressive stress when the upper plate (passive plate) is separated at the scribe. In addition, large gas bubbles may appear near the cut edge of the display panel  10  prior to sealing the cut edge, making the LCD unusable. 
     Further, a method of cutting the associated TABs, flex circuits and/or circuit boards described above is required. That is, a method is needed to remove undesired portions, while maintaining the integrity of the desired portions of the associated TABs, flex circuits and/or circuit boards such that their final size corresponds to the desired size of the display panel. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a method of resizing an LCD while maintaining the integrity of all remaining desired portions of the LCD. 
     It is another object of the present invention to provide a method of resizing a display panel of the LCD without damaging the active plate of the display panel. 
     It is still another object of the present invention to provide a method for repairing the cut edge by replacing accumulated gas bubbles with liquid crystal material. 
     It is still another object of the present invention to provide a method for sealing the cut edge of the display panel, which allows gas bubbles to escape from the seal region into the sealing adhesive. 
     It is yet another object of the present invention to provide a method for removing undesired portions of any associated TABs, flex circuits and/or circuit boards, while maintaining the integrity of the desired portions corresponding to the desired size of the display panel. 
     To achieve the above objects, provided in accordance with the present invention is a method of resizing a liquid crystal display (LCD). The method includes the steps of first determining a desired size for the LCD, thereby identifying an undesired portion of the LCD. Any tape automated bonding strips (TABs) corresponding to the undesired portions of the LCD are then removed. Any flex circuits, or portion thereof, corresponding to the undesired portion of the LCD are cut and removed. Any circuit boards, or portions thereof, corresponding to the undesired portion of the LCD are cut and removed. The display panel is cut to remove a portion of the display panel corresponding to the undesired portion of the LCD. Finally, the cut edge of the display panel is sealed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above objects, features, and advantages of the present invention will become more apparent in light of the following detailed description of exemplary embodiments thereof taken in conjunction with the attached drawings in which: 
     FIG. 1 is a perspective view of a conventional LCD utilizing flex circuits and circuit boards; 
     FIG. 2 illustrates a conventional TAB which may optionally be utilized in a conventional LCD; 
     FIG. 3 illustrates an overall view of resizing an LCD in accordance with the present invention; 
     FIG. 4 is a flow chart illustrating a general procedure for resizing an LCD in accordance with the present invention; 
     FIGS. 4A,  5  and  6  illustrate the procedure of FIG. 4 on an LCD in accordance with the present invention; 
     FIGS. 7 and 8 illustrate a method for resizing a display panel in accordance with the present invention; 
     FIGS. 9-12 illustrate a method of sealing a panel assembly in accordance with the present invention; and 
     FIG. 13 illustrates a method of cutting a flex circuit in accordance with the present invention. 
    
    
     DESCRIPTION OF THE INVENTION 
     Turning again to the drawings, in which like reference numerals identify similar or identical elements throughout the several views, the present invention provides a method of reducing, or resizing, an oversized LCD to conform to size constraints. Referring again to FIG. 3, an overall size of the LCD is reduced to a desired size  37  by removing an undesired portion  38 . In some cases, the aspect (width vs. height) of the LCD may change from landscape (aspect&gt;1) to portrait (aspect&lt;1) or may become square (aspect=1). 
     FIG. 4 outlines an overall procedure for resizing an LCD. In Step  40 , the polarizer (and compensator) films are removed from the top and bottom substrates in the area to be cut. In step  41 , the TABs, flex circuit and/or circuit board are cut and the undesired portions are removed. The display panel is then cut in step  42 , and the cut side is examined for damage and resulting gas bubbles. If gas bubbles are detected, the edge is repaired in step  46 . The cut edge is then sealed with an adhesive in step  48 . Each step in the procedure of FIG. 4 is further detailed hereinbelow. 
     FIG. 4A further details step  40 . The films are removed from the front and back surfaces in the undesired portion  43  so that the cutting tool can directly contact the glass substrates along the cutting path  45 . This ensures a repeatable, high quality scribe mark. In some cases, all of the film may be removed from both substrates. This may be done, for example, to replace the existing films with new films, which will further enhance the optical and/or environmental performance of the resized LCD. 
     FIGS. 5-6 further detail step  40 . FIG. 5 illustrates a top view of an LCD to be resized, which includes a display panel  50 , a plurality of TABs  52 , a row driver board  54  and a column driver board  56 . 
     In FIG. 6, the undesired portion of the LCD is represented. Here, the undesired portion  60  of the display panel  50 , the corresponding TAB  62  and the undesired portion  66  of the column driver board  56 , which corresponds to TAB  62 , are illustrated. TAB  62  is removed from the display panel  50  using any suitable means, for example, using a heat bar, a hot knife, a cold knife or simply by peeling TAB  62  away by hand. Using a hot knife is currently the best-known method for removing TAB  62 . Here, the TAB  62  removed directly corresponds to the column address lines present in the undesired portion  60  of the display panel  50 . 
     The column driver circuit board  56  is correspondingly reduced in size using any suitable means, such as performing an end mill, as is typically utilized in the printed circuit board industry. Special care must be taken to avoid damaging needed traces that serve the last active TAB  68 . Therefore, the circuit board must first be examined and the location of the traces serving the last active TAB  68  must be noted. The column driver board  56  is then carefully cut, removing undesired portion  66 , while making sure to maintain the integrity of the noted traces serving the last active TAB  68 . Once a proper cutting pattern has been identified, all similarly manufactured column boards may be cut using the same pattern. Additionally, mechanical fixtures may be used to aid in the aforementioned processes, to increase both precision and yield, as well as the processes described hereinafter. 
     A functional test of the LCD may preferably be conducted to ensure that the remaining desired portions of the LCD are completely functional in order to avoid unnecessary expenditures on a permanently damaged assembly. 
     The procedure outlined above may be used for removing multiple TABs  62 . Additionally, while a method of removing a columnar portion of the LCD has been described, a row or horizontal portion may similarly be removed along with the corresponding TABs  62  and corresponding portion of the row driver circuit board  54 . Likewise, both a columnar and horizontal portion of the LCD may be removed. 
     However, where an LCD contains interdigitated row address lines, which are supplied from both opposing sides (right and left), a columnar portion may not be removed without reducing the density of the display. Likewise, where an LCD contains interdigitated column address lines, which are supplied from both opposing sides (top and bottom), a horizontal portion may not be removed without reducing the density of the display. 
     Another step in the resizing of the LCD involves resizing the display panel  50 . A procedure for reducing the size of the display panel, as represented by step  42  of FIG. 4, begins with identifying the undesired portion  50  of the display as shown in FIG.  6 . Once the undesired portion has been identified and the TABs are removed as described above, the polarizers  72  and  74  are removed from the display panel as shown in FIG.  7 . The display panel  50  will typically be a plate assembly  70 , a front polarizer  72  and rear polarizer  74 . The front and rear polarizers  72  and  74  may be removed from the entire display panel, or only the section to be removed. In some cases, the polarizers  72  and  74  may be laminated to other films, such as compensation films. For the purposes of brevity, polarizers  72  and  74  are assemblies, which may include various laminates. 
     In all cases, proper electrostatic discharge (ESD) procedures must be followed to avoid damaging the voltage sensitive devices within the display panel or within the row and column assemblies. This is especially true when removing the adhesive-backed films from the glass substrates. As is well known in the art, removing tape from a surface leads to an effect called tribocharging. When two materials are brought into close contact and separated, a transfer of electrons occurs between them. The materials acquire opposite charges, and in the case of non-conductors, the charge imbalance stays localized on the surface at the point of separation. Since both the film and glass substrate are non-conductors, ESD must be controlled by using ionizers, regulating the speed of the separation process and controlling the relative humidity. 
     Referring to FIG. 8, the plate assembly  70  comprises active plate  82  and passive plate  80 , which enclose the liquid crystal material  81 . The passive plate  80  and the active plate  82  are each scribed, creating scribes  84  and  86 , the closest of which is offset from an active area of the display panel by a first offset distance  87 , preferably 3 mm or greater. The active area is the portion of the resized LCD that is functional for display purposes. The first offset functions to minimize migration of the edge seal adhesive into the active area, thereby causing degradation in optical performance. In the preferred embodiment, scribes  84  and  86  are offset by a second offset distance  88 , which is preferably 1-2mm. The purpose for the second offset  88  is to provide ample area for the sealing operation. Either the active plate  82  or the passive plate  80  may contain the additional surface area, to allow ample area for the adhesive. In any case, it is preferable to have an overall offset (first offset  87  plus second offset  88 ) of at least 5 mm. In the preferred embodiment shown in FIG. 8, the passive plate  80  overhangs the active plate  82  in order to protect the active plate from being exposed to potential sources of damage prior to edge sealing. The offset  88  further serves to prevent short circuits in the desired portion of the active plate  82  resulting from compressive stress induced on the active plate  82  when the passive plate  80  is broken at scribe  86 . 
     Next, the plate assembly  70  is broken at each scribe  84 ,  86 . In a preferred embodiment, the passive plate  80  is broken first to further protect the integrity of the active plate  82 . An angular displacement of approximately 1° is required to break the plate assembly  70  along each scribe  84 ,  86 . 
     Referring to FIG. 11, the panel assembly  70  may then be inspected along cut side  110  for damage or gas bubbles  112  resulting from the break. The gas bubbles may then be eliminated by positioning the cut edge  110  oblique or vertical, as illustrated in FIG.  12 . Some liquid crystal material  120  is applied to edge  110  while the vertical orientation of the panel assembly  70  is maintained. Here, the liquid crystal may be doped or undoped material. Preferably, the liquid crystal is doped to match the liquid crystal of the raw panel. The panel assembly  70 , still oblique or vertical, is placed in a vacuum to allow the gas bubbles to escape from the cut edge  110 . Once the gas bubblesl 2  have escaped, the liquid crystal  120  added will fill the void created, thereby replacing the gas bubbles  112  with liquid crystal  120 . This process may be facilitated by optionally preheating the plate assembly  70  prior to placing it in the vacuum. 
     Referring to FIG. 9, a method of sealing the panel assembly  70  is illustrated, as represented by step  48  of FIG.  4 . The panel assembly is sealed by applying an adhesive  90  to the cut edge  110 . Many suitable adhesives may be used, including UV (ultraviolet), air, and heat cured adhesives. In a preferred embodiment, a UV cured adhesive is used. The panel assembly  70  is tilted to a small angle  92  to raise the sealed region. The tilt allows any remaining gas bubbles  112  to escape into the adhesive  90 , where they may safely reside without seriously compromising the effectiveness of the seal. The edge  110  does not have to be cleaned prior to applying adhesive  90 , since any residual liquid crystal material  81  will dissolve into the adhesive  90 . After the adhesive  90  has been properly applied, it is cured using methods appropriate for the adhesive type, and commonly known in the art. 
     FIG. 10 illustrates the preferred embodiment of a sealed panel assembly  70 . 
     Referring now to FIG. 13, a flex circuit  138  is illustrated, as represented by step  40  of FIG.  4 . The flex circuit  138  is interposed between the display panel  50  and a circuit board  56 . The flex circuit  138  includes driver chip  132 , input traces  136 , and output traces  134 . The input traces  136  transfer electrical signals from the circuit board  56  to the driver chip  132 , and may not be cut or damaged. The output traces  134  correspond to the address lines served by the driver chip  132  for the corresponding portion of the display panel  50 . Some of the output traces  134  may drive address lines in the undesired portion  60  of the display panel  50 . In such a case, the output traces  134  and the corresponding portion of the flex circuit  138  may be cut and discarded. 
     The flex circuit is carefully examined to determine which of the output traces  134  are no longer needed. The number of output traces  134  typically outnumbers the number of input traces  136 . Therefore, all the input traces  136  are typically gathered on the side of the driver chip facing the circuit board  56 , while the output traces  134  are typically found on all sides of the driver chip  132 . Next, an optical axis  130  of the cut line must be determined such that only output traces  134  no longer required are cut, without damaging the remaining output traces  134  or any of the input traces  136 . The cut then is made using a sharp edge. An X-acto knife is preferably used to make the cut. Once again, proper ESD procedures are preferably employed. 
     In a case where the polarizers are removed prior to resizing, new films are laminated to the display at this time. The lamination and orientation of the polarizers are well known in the art. 
     Accordingly, using the procedure outlined in FIG.  4  and further detailed above, a novel method of resizing an LCD is disclosed. 
     While the present invention has been described in detail with reference to the preferred embodiments, they represent mere exemplary applications. Thus, it is to be clearly understood that many variations may be made by anyone having ordinary skill in the art while staying within the spirit and scope of the present invention as defined by the appended claims.