Seamless tiled active matrix liquid crystal display

Abstract

A seamless tiled display employs active liquid crystal display (LCD) and backlight. The active matrix elements of active LCD are mounted on the inside or outside of the front plate or back plate of LCD. A thin front plate and a thin sealing wall are used to reduce the seam width of the tiled LCD. A laser cutting is used for a thin LCD sealing. A spacer added adhesive array is deposited between pixels and between front plate and back plate to guarantee the uniformity of LC cells thickness. A laser riveting is still used for making a robust plastic LCD. A reflective layer is deposited on the side wall of back plate to reflect the light emitted from the backlight and to reduce the apparent seam width. In the backlight, there can be at least one set of red, green and blue light source operated at color sequential mode to display a color image without the use of color filters.

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation-in-part of U.S. Provisional Application Ser. No. 60/077,675 filed on Mar. 12, 1998 and U.S. Provisional Application Ser. No. 60/081,085, filed on Apr. 8, 1998.

BACKGROUND OF THE INVENTION

[0002] This invention relates in general to a seamless tiled display and, in particular, to seamless tiled active liquid crystal display (LCD).

[0003] Tiled displays have been used frequently in super-large-screen displays for indoor and outdoor applications to display character and full-color image, such as sports stadiums, exhibition halls etc. Several types of tiled full color super-large-screen displays have been used or proposed. One type known as tiled flat CRT, such as Jumbotron, is a kind of flat matrix CRT which has a hot filament cathode, mesh grid and anode. The anode voltage is about 8 kv, and one display tile includes about 20 color pixels. This kind of display has a good color quality image, but a short lifetime and a high anode voltage.

[0004] Another conventional tiled display system currently used is known as a light emitting diode (LED) tiled display. One pixel includes several red, green and blue (R, G, B) LED lamps or chips. It can display a good quality fill color image and high brightness, and can be used in both indoor or outdoor applications. But this kind of tiled display is very expensive especially for a super-large-screen display, because it must employ a large number of small individual LEDs that have diameters of about 5 mm.

[0005] Another conventional tiled display system is a tiled liquid crystal display (LCD) as described in U.S. Pat. No. 5,557,436. In this kind of display, a passive LCD and a hot cathode fluorescent lamp (HCFL) back-light are used. The color quality, contrast and brightness are not quite satisfactory. Therefore, at present, this kind of display is only used for displaying characters. On the other hand, the seam width of this tiled display is normally quite large. This is caused by the use of a wide sealing wall, a thick front plate and thick back plate. This kind of display cannot be used for a high resolution tiled display.

SUMMARY OF THE INVENTION

[0006] This invention is based on active LCD and backlight to make a seamless tiled display. The problems described above with conventional tiled displays are alleviated or avoided altogether.

[0007] This invention reduces the visually apparent seam width of the tiled display. For this purpose, a thin glass or plastic front plate of LCD is used. The thickness of the front plate is preferably in the range of about 0.02 to 0.7 mm.

[0008] To reduce the visually apparent seam width of the tiled display, a reflective layer is employed on the side wall of the back plate to reflect the light emitted from the backlight. Therefore, the apparent seam width can be reduced.

[0009] As explained above, conventional LCD devices employ thick front and back plates because of the requirement that the device be mechanically sturdy. By using a back light or reflector with adequate mechanical strength and connecting LCD tiles to the back light or reflector to lend mechanical strength to the tiles, it is possible to use thin front and back plates in the LCD tiles, thereby reducing or eliminating apparent seam widths and so that the tiled display appears to be seamless.

[0010] A plastic LCD device may be conveniently made by aligning LC cells between two sheets of plastic and using a laser to cut the two sheets into smaller pieces by melting the plastic in the two sheets along the lines that are cut. The melting of the plastic at the edges of the smaller pieces causes the front and back portions of the pieces to bond and form a sealing wall. Where a sturdier sealing wall is desired, an adhesive material may be applied between the two sheets along the lines of cutting by the laser to bond the two sheets prior to the cutting process. Therefore, the heat of the laser will melt the plastic material of the two sheets as well as the adhesive material to form a sturdy sealing wall for the LCD devices formed.

[0011] To further enhance the mechanical strength of the plastic LCD's, rivets may be formed connecting the front and back plastic plates by applying a drilling laser to the device. The laser may be applied to form one or more holes in the device by melting the front and back sheets at selected spots and the melted plastic of the two sheets are bonded together to form a rivet. Alternatively, for high resolution displays, the rivets are formed without forming visible holes.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1a shows a side cross-sectional view of a conventional display with the apparent tiled seam width K of two adjacent tiled displays.

[0013] FIG. 1b shows a top view of FIG. 1a.

[0014] FIG. 2 shows a prior art thin seam tiled display.

[0015] FIG. 3a shows a top view of an embodiment of the seamless tiled display of the present invention.

[0016] FIG. 3b shows a side cross-sectional view of the display of FIG. 3a along line 3b-3b in FIG. 3a.

[0017] FIG. 4 shows the effect of the back plate thickness to the seam width of the tiled display.

[0018] FIG. 5 shows a side cross-sectional view of a seamless tiled display of the present invention employing a reflective layer on the side wall to illustrate another embodiment of the present invention.

[0019] FIG. 6a shows a top view of a seamless tiled display of the present invention employing a reflective layer on the side wall to illustrate yet another embodiment of the present invention.

[0020] FIG. 6b shows a side cross-sectional view of the display of FIG. 6a along line 6b-6b in FIG. 6a.

[0021] FIG. 7 shows a tiled active LCD display system, which has N×M tiles.

[0022] FIG. 8a shows the cross-sectional view of the portion of one more embodiment of seamless tiled LCD display of the invention.

[0023] FIG. 8b is the front view of the portion of FIG. 8a. FIG. 8a shows the cross-sectional view of the portion of FIG. 8b along the line 8a-8a in FIG. 8b.

[0024] FIG. 9 shows the cross-section view of the portion of another embodiment of seamless tiled LCD of the invention where multiple tiles share a backlight.

[0025] FIG. 10 shows a side cross-sectional view of an another embodiment of the seamless tiled display of the present invention.

[0026] FIG. 11a shows atop view of an embodiment of the laser sealed and riveted plastic LCD of the present invention.

[0027] FIG. 11b shows a cross-sectional view of the display of FIG. 11a along the line 11b-11b in FIG. 11a.

[0028] FIG. 12 shows the cross-sectional view of the portion of another embodiment of laser sealed and riveted plastic LCD of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0029] Each tile in a tiled display contains a number of pixels, where the adjacent pixels are separated by an inter-pixel spacing. In order to obtain a seamless tiled display, the actual apparent inter-pixel spacing between two adjacent tiles is preferably the same as the inter-pixel spacing within the display tile. That is the apparent seam width between two adjacent tiles is substantially the same as the inter-pixel spacing within the display tile so that a seamless image can be obtained.

[0030] The seam width may be reduced by using a thin front plate. By using a thin front plate, the apparent seam width is reduced. An active matrix LCD may also be used. The active matrix elements of active LCD may be mounted on the interior surface of the substrate of LCD, or more preferably mounted on the outside of the substrate as described in U.S. Pat. No. 5,510,915 named outside-active matrix LCD (OAM-LCD). The active matrix element acts as a switch to control the electrical signal applied to a given LC cell and to eliminate the cross-talk between the LC cells, so that good quality and good contrast images can be obtained.

[0031] In order to improve the uniformity of the LC cells thickness, it is preferable to employ an adhesive array has one or more spacers deposited among pixels and between front plate and back plate of the LCD. The sealing wall and the front plate can be one piece or separated. The former can be made of plastic and latter can be made of the same material or different materials; for example, the front plate is made of glass or plastic, and the sealing wall is made of plastic.

[0032] The active matrix elements of an active LCD may be mounted on the interior surface of the substrate of LCD, or more preferably mounted on the outside of the substrate as described in U.S. Pat. No. 5,510,915 named outside-active matrix LCD (OAM-LCD). The active matrix element acts as a switch to control the electrical signal applied to a given LC cell and to eliminate the cross-talk between the LC cells, so that good quality and good contrast images can be obtained.

[0033] In the case of OAM-LCD tiled display, the active matrix elements are mounted on the outside of the front plate or back plate. The electrodes of the active elements are connected to the electrodes of the LC cell through the conductive pin hidden in the front plate or the back plate. On the other hand, the electrodes of the active elements are connected to the display system electronics through the conductive connectors. These connectors are deposited on the sealing wall, the outside surface of the front plate or the back plate. Therefore, the LCD can modulate the light emitted from the backlight and to display a image.

[0034] Due to reduced front plate thickness, sealing wall thickness and depositing a reflective layer on the side wall of the back plate, a seamless tiled display can be made having high resolution.

[0035] The invention teaches a full-color tiled display using at least a set of red, green and blue (R, G, B) cold cathode fluorescent lamp (CCF) or light emitting diode (LED) backlight. The R, G, B CCF or LED can be operated in a color sequential mode according to the display signal from the display system electronics. The LCD is also operated according to display signal. The image signal is divided into three sub-field, R, G, B sub-field, when LCD displays red image, the red CCF or LED is lighted, then LCD displays green image, the green CCF or LED is lighted, then blue. Therefore a full-color image can be displayed. In this case, the filter is needless and the brightness of the image will be higher.

[0036] To increase the resolution of the tiled display and to get a kind of high resolution tiled LCD, the high resolution tiled LCD comprises of a large screen spacer-shadowless backlight and some tiles. The tiles are mounted on the front diffusing plate of the backlight to form a high resolution tiled LCD.

[0037] A laser sealing method may be used for making a plastic LCD. Using the laser to cut the plastic LCD along the sealing area, because the front and back plates of the plastic LCD will be melted during laser cutting, a thin sealing wall will be formed. The laser sealing method can be used for LCD tile and single piece LCD sealing. A good robustness riveted plastic LCD comprises a thin front plastic plate and a thin back plate. In the LCD, there are some rivets riveting said two plates by laser beam. The riveting method can be used for plastic LCD tile and single piece plastic LCD, to get a very robust LCD and large screen plastic LCD.

[0038] FIG. 1a shows a side cross-sectional view of a prior art LCD display illustrating the concept of the apparent seam width K of two adjacent tiled displays.

[0039] FIG. 1b shows a top view of the display in FIG. 1a.

[0040] Adjacent LCD display tiles 101 and 102 are shown in FIGS. 1a, 1b, with gap 103 between the two adjacent display tiles. Each tile has a front plate 104, back plate 105, column electrode 106, row electrode 107 and sealing wall 108. 109 is a side circuit plate, which has conductive connector 110. The connector 110 connects the electrodes 106 and 107 to the driving circuit of the display system. 111 is a LC layer. 112 is a black matrix. The width M of the black matrix is the inter-pixel spacing within the display tile.

[0041] The apparent seam width K between two adjacent display tiles depends on the following factors:

[0042] the gap width H between two display tiles;

[0043] the sealing wall width W of the display tile;

[0044] the thickness C of the side circuit plate of the display tile;

[0045] the thickness TF of the front plate of the display tile, because the light ray 113 from the pixel 114 proceeding to the side wall 109 will be obstructed by the side wall;

[0046] the thickness TB of the back plate of the display tile, because the light ray 116 from a backlight or a back reflector proceeding towards the side wall 109 will be obstructed by the side wall;

[0047] the non-uniformity of the luminance and the color near the tiled seam area. If the luminance or color is non-uniform near the tiled seam, e.g., the luminance of the area 115 is lower than the area 114 or the color is different, the apparent seam width K will be larger.

[0048] The actual apparent tiled seam width K is the sum of factors mentioned above.

[0049] For a seamless tiled display, the luminance and the color should be uniform in the whole active display area, and the apparent tiled seam width K should be the same as the inter-pixel spacing M within the display tile.

[0050] FIG. 2 shows a prior art thin seam passive tiled LCD (e.g., U.S. Pat. No. 5,557,436), which has a thin sealing wall 208 and thin side tape 209. 204 and 205 are the front plate and back plate. 206 and 207 are row and column electrodes of the display. 210 is the conductive connector located on the side tape 209. The conductive connector 210 connects the electrodes 206 and 207 to the driving circuit (not shown) of the display system. 211 is a LC layer operated at passive mode. 217 are polarizers.

[0051] In the conventional tiled LCD, thick front and back plates are used to assure that the LC layer 211 has uniform thickness, so that the LCD displays a uniform image. The thick front and back plates make the apparent tiled seam width K larger.

[0052] On the other hand, in the conventional tiled LCD, the row and the column electrodes of the display are extended from the front and back plate interior surfaces to the side surfaces of the plates through the rectangle edges 216 of the plates. In this case, the electric connection can easily become broken at or near the edges, resulting in an open circuit, which means the reliability of this structure is usually rather poor.

[0053] In the conventional tiled LCD, a passive LCD is used. In this case, the contrast and image quality are usually less than satisfactory, because of the cross-talk between LC cells. In addition, in the conventional tiled LCD, a hot cathode fluorescent lamp back-light (HCFL-BL) is used for tiled LCD. Hence the brightness of the display may be inadequate for some applications and the life-time of the display is short.

[0054] FIG. 3a shows a top view of a portion of an embodiment of a seamless tiled outside-active-matrix LCD (OAM-LCD) of the invention, and FIG. 3b is a cross-sectional view of the LCD of FIG. 3a along the line 3b-3b in FIG. 3a. In FIG. 3a and FIG. 3b, 304 is a thin front plate, and 305 is the back plate. 304 and 305 are transparent substrate, e.g., glass or plastic. 308 is a thin sealing wall, which can be one integral piece with the front plate 304 or a separate piece. 306 is a separated electrode array of LCD, and 307 is a common electrode of LCD. Electrodes 306 and 307 define a matrix LCD. 311 is a LC layer. 318 is an adhesive array having at least one spacer but preferably a plurality of spacers 319 deposited among pixels and between front plate 304 and back plate 305. This adhesive array can guarantee the uniformity of the LC cell's thickness to get a uniform display image.

[0055] 320 is a series of conductive pins hidden in the front plate 304. One terminal of the pin 320 is connected to the separated electrode 306, the other terminal of the pin 320 is connected to the source electrode (S) of the outside active matrix device 321, which may for example be a field effect transistor (FET), and which is preferably mounted on the outside surface of the front plate 304. Instead of a FET, the outside active matrix control device 321 may also be a diode, bipolar transistor, switch, or varistor etc. As shown in FIG. 3a, one outside active device 321 controls one LC cell, i.e. one color dot. But these active devices can also be integrated into an integrated circuit chip, i.e. one chip controls one group of LC cells. 322 is another conductive pin hidden in the front plate 304, one terminal of the pin being connected to the common electrode 307 through a conductive means 323, i.e., silver (Ag) paste, and the other terminal of the pin 322 being connected to the conductive connector 324 and then connected to the system driving circuit (not shown) through the printed circuit board (PCB) 329. 325 is a series of another conductive pin hidden in the front plate 304, one terminal of the pin 325 is connected to the row scanning electrode 326, and the other terminal of the pin 325 is connected to the gate electrode (G) of the outside active matrix device 321. The, row scanning electrode 326 is connected to the PCB 329 through conductive connector 339, then connected to the system driving circuit (not shown) through the connector 330′. 327 is a column signal electrode, one terminal of the electrode 327 being connected to the drain electrode (D) of the outside active matrix device 321, and the other terminal to the PCB 329 through connector 328, then to the system driving circuit (not shown).

[0056] 317 are two polarizers, one is located at the outside surface of the front plate 304, and other one is located at the outside surface of the back plate 305. 330 are color filters, deposited on the outside surface of the front polarizer 317. For a monochrome or black/white display, this filter may be omitted. 331 is a black matrix.

[0057] 332 is an outside sealing cover, which is an anti-reflective plate, a transparent or diffusing plate, or having the optical function to change the light direction to alter the viewing angle, e.g., micro-lens plate or holographic plate and the like. This cover may cover only one tile, or two or more tiles up to the entire screen of the display. If this cover does not cover the entire screen, more than one cover may be employed to cover all the tiles of the screen.

[0058] 333 is a reflective layer deposited on the side wall of the back plate 305, the operating principle of which is illustrated below in reference to FIG. 5.

[0059] 334 is a back-light, which has at least one CCF, HCFL or LED 335 as its light source. 336 is a driver for CCF, HCFL or LED 335. The driver 336 has a brightness adjustment circuit to adjust the brightness of the backlight by manual or a sensor to automatically adjust the brightness in order to guarantee the brightness uniformity in the whole tiled screen. To adjust the brightness manually, one may adjust a potentiometer in the circuit, for example. To adjust the brightness automatically, a photodiode in the circuit may be used to provide feedback signal so as to adjust the brightness, for example. 337 is a reflective chamber of the backlight 334. 338 is a diff-user and a brightness enhancement film (BEF) of the backlight 334.

[0060] In this embodiment, thin front plate, thin sealing wall and back plate side wall reflector are used, so the apparent seam width can be very small, therefore, the high resolution seamless tiled display can be made. For example, the thickness of front plate 304, TF, may be in a range of about 0.02 to 0.7 mm, and the thickness of back plate 305, TB, may be in a range of about 0.02 to 4 mm. With the front and back plates of such thicknesses, the apparent seam width is much reduced compared to the conventional displays.

[0061] FIG. 4 shows a cross-sectional view of a tiled display, which shows the effect of a thick back plate on the apparent seam width of the tiled display. 401 and 402 are two adjacent tiled LCDs. 404 and 405 are the front plate and back plate. 406 is the separated electrode (similar to 306 in FIG. 3) and 407 is the common electrode. 411 is a LC layer, and 417 are the polarizers. 434 is a backlight.

[0062] In FIG. 4, “A” shows a location which is far from the sealing wall 408. In this area, the light rays in all directions, 440, 441 and 442, can go through the display, however, at or near the sealing wall area B, the light beams in the directions 443 and 444 can go through the display, but the light beam 445 will be obstructed by the sealing wall 408. 434 may be a backlight in a transmissive LCD or a light reflector in a reflective LCD. The light beam 446 emitted from backlight 434 (for transmissive LCD) or reflected by reflector 434 (for reflective LCD), (equivalent to beam 445 from the area B), will be also obstructed by the sealing wall 408. Therefore, the apparent seam width will be wider. The thicker the back plate TB, the bigger the apparent seam width.

[0063] In order to eliminate or reduce the effect of the thick back plate on the apparent seam width, a reflective layer can be deposited on the side wall of the back plate. FIG. 5 shows the reflective layer 533, which is deposited on the side wall of the back plate 505;,which can reflect the light beams 545 and 546 to illuminate the LC cell. The light beams 545 and 546 are similar to 547 and 548, which are emitted from backlight 534 for a transmissive LCD or reflector 534 for a reflective LCD. In other words, where 534 is a backlight, device 500 is a transmissive LCD; where 534 is a reflector, device 500 is a reflective LCD. Therefore, the effect of the back plate thickness on the seam width can be eliminated or reduced, and a high resolution seamless tiled display can be obtained.

[0064] FIG. 6a shows a top view of the portion of another embodiment of a seamless tiled OAM-LCD of the invention, and FIG. 6b is the cross-section view of the LCD of FIG. 6a along line 6b-6b in FIG. 6a. In this embodiment, a thin front plate and the R, G, B CCF or LED backlight are used. This display can be operated at color sequential mode to get the full-color image without using color filters. In FIG. 6a and FIG. 6b, 604 is a thin front plate, and 605 is a back plate. The plates 604 and 605 are transparent substrate, e.g., glass or plastic. 608 is a thin sealing cover, and made of plastic. 606 is a separated electrode array of LCD, and 607 is the common electrode of LCD. Electrodes 606 and 607 define a matrix LCD. 675 is a LC layer. 618 is an adhesive array which has spacer 619 deposited between pixels and between front plate 604 and back plate 605. This adhesive array can guarantee the uniformity of the LC cells thickness to get a uniform display image.

[0065] 620 is a series of conductive pins hidden in the front plate 604, one terminal of the pin 620 is connected to the separated electrode 606, the other terminal of the pin 620 is connected to the source electrode (S) of the outside active matrix device 621, e.g. FET, which is mounted on the outside surface of the front plate 604. As the outside active matrix device, diode, switch, varistor etc. can also be used. As shown in FIG. 6, one outside active device control one LC cell, i.e. one color dot. But these active devices can also be integrated into the chip, i.e. one chip controls one group of LC cells. 622 is another conductive pin hidden in the front plate 604, one terminal of the pin 622 is connected to the common electrode 607 through a conductive means 623, i.e., Ag paste, and the other terminal of the pin 622 is connected to the conductive connector 624 (which bends down at sealing wall 608 to reach PCB 629) and then connected to the system driving circuit through the PCB 629. 625 is a series of another conductive pin hidden in the front plate 604, one terminal of the pin 625 is connected to the row scanning electrode 626, and the other terminal of the pin 625 is connected to the gate electrode (G) of the outside active matrix device 621. The row scanning electrode 626 is connected to the PCB 629 through conductive connector 639, then connected to the system driving circuit through the connector 630. 627 is a column signal electrode, one terminal of the electrode 627 is connected to the drain electrode (D) of the outside active matrix device 621, and the other terminal is connected to the PCB 629 through connector 628, then to the system driving circuit (not shown) through connector 630.

[0066] 617 are two polarizers, one is located at the outside surface of the sealing cover 608, and an other is located at the outside surface of the back plate 605. 631 is a black matrix.

[0067] 632 is an outside sealing cover, which is an anti-reflective plate, a transparent or diffusing plate, or having the optical function to change the light direction to change the viewing angle, e.g., micro-lens plate or holographic plate and the like. 633 is a reflective layer deposited on the side wall of the back plate 605.

[0068] 634 is a backlight, which has at least one set of R, G, B light sources, such as HCFLs, CCFLs or LEDs 635. 636 is a driver for HCFLs, CCFLs or LEDs 635. 637 is a reflective chamber of the backlight 634. 638 is a diffuser and a brightness enhancement film (BEF) of the backlight 634.

[0069] The R, G, B HCFLs, CCFLs or LEDs 635 can be operated in a color sequential mode according to the display signal from the display system electronics. At the same time, the LCD is also operated according to display signals. The image signal is divided into three sub-field, i.e. R, G, B sub-field. When LCD displays red image, the red CCF or LED is lighted; then LCD displays green image, the green CCF or LED is lighted; and then blue. Therefore a full-color image can be displayed. In this case, color filter need not be used so that the brightness of the image will not be reduced by the filters and will be higher than otherwise.

[0070] FIG. 7 shows a tiled active LCD display system, which has N by M tiles 701, where N, M are positive integers, Each tile has a backlight with HCFLs, CCFLs or LEDs (not shown) and a driver 736 (performing the same function as driver 636 of FIG. 6) for driving the backlight, and a connector 730 similar to connectors 330, 630 of FIGS. 3b and 6b. 750 is a control and driving circuit of the system. 749 is a cable connecting each tile to circuit 750 through connectors 730. Thus, the system driver circuit 750 controls the driver circuits 736 which in turn drives the backlight of the tiles 701. Circuit 750 also controls the voltages applied to the common electrode (not shown in FIG. 7) which are similar to the common electrodes 307 and 607 in FIGS. 3a, 3b, 6a, 6b, and the separated electrode array (not shown in FIG. 7) similar to arrays 306 and 606 in FIGS. 3a, 3b, 6a, 6b. Circuit 750 is connected to the common electrode and separated electrode array through connector 730 of each tile, where connector 730 serves the same function as connectors 330, 630 of FIGS. 3a, 3b, 6a, 6b. In this manner, circuit 750 controls the sequential addressing of the entire display comprising N×M tiles. As shown in FIG. 7, the connector 730 of each tile are connected to circuit 750 by means of cable 749. The drivers 736 of all the tiles are connected to the circuit 750. In the particular design illustrated in FIG. 7, each tile has its own backlight and backlight and backlight driver, which is controlled by circuit 750 so that the N×M tiles act as one display.

[0071] FIG. 8a shows the cross-sectional view of a portion of another embodiment of seamless tiled LCD of the invention; and FIG. 8b is the front view of FIG. 8a. In this embodiment, the LCD tiles have thin front plate 804 and thin back plate 805, and are mounted on a backlight or reflector 834 with good mechanical strength so that the LCD in the tiles will have uniform thickness. The backlight or reflector 834 is used as a base plate of the display screen, and can be made a very light weight, thin profile, very strong large screen and super-large screen display. The tiled display is like a single piece display. In other'words, by relying on the backlight for strength to maintain the LCD at a uniform thickness, it is possible to reduce the thicknesses of both the front and back plates to reduce apparent seam width.

[0072] In FIGS. 8a and 8b, 801a, 801b, 801c and 801d are the portions of four adjacent LCD tiles. The LCD tile can be a transmissive LCD, reflective LCD, scattering LCD or outside-active-matrix LCD (OAM-LCD).

[0073] In FIGS. 8a, 834 is a backlight or reflector device with good mechanical strength. For a transmissive tiled LCD, 1034 is a backlight, which has at least one light source 835, e.g. hot cathode fluorescent lamp (HCFL), cold cathode fluorescent lamp (CCF) or LED. 852 is a good mechanical strength frame, which is made of metal or plastic, e.g. aluminum alloy and steel. 853 is a reflective chamber, which has high reflective walls 854, and the front face of the reflective chamber 853 is a diffusing plate 838 to make the brightness of the backlight very uniform. In order to increase the brightness of the backlight, the diffusing plate 838 can also have a brightness enhancement function, e.g. with a brightness enhancement film. 855 is a spacer of the backlight, which is located between the front diffusing plate 838 and the bottom surface of the reflective chamber 853, so that the good mechanical strength of the frame 852 lends support also to the diffusing plate 838 through the spacer 855, thereby enabling the diffusing plate to have a very flat surface.

[0074] The spacers 855 can be a transparent round pole, cone shape or other shape, which is made of a transparent material, e.g. plastic or glass. The top of the spacers 855 are polished, mounted and attached on the diff-using plate 838 by transparent adhesive 856. The other end of the spacers 855 are fixed on the frame 852 by screw(s) 857. The frame 852, reflective chamber 853, front diffusing plate 838 and spacer 855 formed a very bright backlight with good mechanical strength.

[0075] FIGS. 8a and 8b show an embodiment of a seamless tiled OAM-LCD of the invention. 801a, 801b, 801c and 801d are the portions of four adjacent OAM-LCD tiles. The tiles are mounted on the diffusing plate 838 by adhesive 858. 803 are gaps between the adjacent LCD tiles. Gaps 803 between tiles may be filled by adhesive 858. The thin front plate 804 and thin back plate 805 are made of glass or plastic, and their thicknesses range from 0.01 to 4 mm, to reduce obstruction of light from the backlight and the apparent seam width. 830 and 812 are respectively the filter and the black matrix, which can be deposited on the inside surface or outside of the thin front plate 804 or back plate 805. 811 is a LC layer, including transmissive LC, e.g. TN, STN, and scattering LC, e.g. polymer dispersed LC (PD-LC). 817a and 817b are two polarizers, one of which is located at the outside of the thin front plate 804, and the other is located at the front surface of the diffusing plate 838, or at the outside of the back plate 805 of the LCD tile. The polarizers can be one sheet per display screen or one sheet per tile. In the case of scattering LC, the polarizers may be omitted. 808 is a sealing wall, which has spacer 819. 806 is a separated electrode array of LCD, and 807 is a common electrode of LCD. One separated electrode and the common electrode defined one LC cell. Each separated electrode 806 has one corresponding color filter 830 for color display.

[0076] In order to increase the viewing angle and contrast of the display image, an optical front plate 859 is located at the front of the tiled screen. The optical front plate has some optical function, e.g. diffusing, anti-reflection, viewing angle changing etc. to increase viewing angle, contrast, and brightness.

[0077] The black matrices 812 may absorb a significant portion of the light originating from the backlight. In order to increase the light utilization of the backlight despite the black matrices, reflective matrices 860 are deposited at the outside surface of the back polarizer 817a or the outside of the front diffusing plate 838. Each of the reflective matrices is aligned with a corresponding black matrix 812, and reflects back towards the chamber 853 the light which is emitted by the backlight and which otherwise would be directed towards and be absorbed by the corresponding black matrix. This increases the light utilization of the backlight.

[0078] Each LCD tile has at least one row electrode 826, which is deposited on the inside surface of the front plate 804, and at least one column signal electrode 827, which is deposited on the outside surface of the front plate 804. 861 is an out-side-active-matrix (OAM) chip, which has at least one active device of OAM-LCD and is mounted on the outside surface of the front plate 804. In the case of FIG. 8a, the chip 861 has 12 active devices (e.g. FETs) to control four pixel (each pixel having 3 LC cells for red, green and blue light for a total of 12 LC cells). For example, one chip 861 has 12 FETs, and each set of 6 FETs have one common gate electrode. Two row electrodes 826 for row m and row (m+1), m ranging from 0 to 511, for example, are connected through pins (not shown) to two gate electrodes of FETs respectively; and 6 column signal electrodes 827 are connected to the D (drain) electrodes of FETs respectively. Twelve S electrodes of FETs are connected to twelve separated electrodes 806 through the conductive pins 820, which are hidden in the front plate 804. When one row, e.g. row m, is applied a row scanning voltage, all the FETs connected with this row are turned on. The video display signal will be applied to the related D electrodes of FETs through related column electrodes 827 and related FETs, and apply to the related LC cells 811 to change the transmittance of the LC cells, and to display the image. Once an LC cell is turned on, its transmittance remains unchanged until it is again addressed, so that a full color display results from the sequential addressing.

[0079] Between the LCD tiles, the column electrodes 827 are connected by a connector 862, made of a transparent means, e.g. transparent film, with some electrically conductive leads 863 deposited, which connect the related column electrodes between the adjacent LCD tiles through the electrically conductive connection pads 864. Between the LCD tiles, the row electrodes 826 are connected by a connector 865, which is made of a transparent means, e.g. transparent film with some electrically conductive leads 866 deposited. The connector connects the related row electrodes between the adjacent LCD tiles through the electrically conductive pins 825, which are hidden in the front plate 804. One LCD tile has one common electrode 807. The connector 867 is made of a transparent means, e.g. transparent film, and the conductive lead 868 is deposited, which is used for connecting the common electrodes 807 of the adjacent LCD tiles through conductive pins 869 and conductive material 870, e.g. silver paste.

[0080] In other words, each OAM chip includes 12 FETs, one for controlling each of 12 LC cells. In reference to FIG. 8b, for example, chip 861 would control the three LC cells in each of the four pixels immediately adjacent to the chip. Chip 861 would receive addressing signals from an outside controller (not shown) through two row electrodes 826: rows m and m+1. The addressing signal in row m would control the addressing of the pixels immediately above it and the addressing signals in row m+1 would control the addressing of the pixels immediately below the row as shown in FIG. 8b. When the addressing signal to row m is asserted, this causes the six FETs addressing the two pixels immediately above row m and adjacent to chip 861 to be turned on. Each of the six LC cells in the two pixels immediately above row m is controlled by a corresponding column signal electrode 827. Therefore, the brightness of the display in each pixel is controlled by three corresponding column signal electrodes 827. The video signals on the, corresponding column signal electrode 827 would then be applied to the drain electrode of the FET corresponding to each of the six LC cells to control the brightness of the image displayed by such cell. As shown in FIG. 8b, two column electrodes 827 is shown to overlap the connector 862 on the left portion of the figure and are connected to the chip 861 through lines 827′ and four column signal electrodes are shown to overlap the connector 862 on the right-hand portion of the figure. Of such six column signal electrodes, three are used for controlling the brightness of the pixel in between the two adjacent connectors 862. Row electrodes 826 and column electrodes 827 are then connected to the system driver-circuit (not shown) for controlling the addressing of the LC cells.

[0081] In order to reduce the resistance of the row electrodes, column electrodes and the common electrodes, and also to increase the connector reliability, the auxiliary electrodes 871 can be used, which can be deposited on the outside of the front plate 804 or on the connectors 862, 865 and 868. If the auxiliary electrodes 871 are located on the connectors 862, 865 and 868, said connectors should be the prolong tapes, e.g. shown as 868, and the auxiliary electrodes are in parallel with the related electrodes.

[0082] FIG. 9 shows the cross-section view of the portion of anther embodiment of a high resolution seamless tiled LCD of the invention. In this embodiment, the LCD comprises of thin LCD tiles 901 and backlight 934. 901a and 901b are the adjacent LCD tiles. The LCD tile can be a transmissive LCD, scattering LCD or OAM-LCD.

[0083] In FIG. 9, 934 is a backlight which with good mechanical strength. In the backlight 934, there are at least one light source 935, e.g., HCFL, CCF or LED. 952 is a good mechanical strength frame, which is made of metal or plastic, e.g., alloy and steel. 953 is a reflective chamber, which has high reflective walls 945. The front face of the reflective chamber 953 is a diffusing plate 938, which makes the brightness of the backlight very uniform. 972 is a transparent back plate of the backlight 934, which is used for eliminating the spacer shadow and to improve the brightness uniformity of the backlight. The coefficient of thermal expansion of the transparent back plate 972 is matched with (that is, substantially the same as) front diffusing plate 938 to assure that the backlight does not bend at different operating temperatures and its mechanical strength is maintained over a wide range of operating temperatures. 955 is the transparent spacer of the backlight, which is located between the front diffusing plate 938 and the transparent back plate 972. 973 is the side wall of the backlight 934. The fame 952, front diffusing plate 938, transparent back plate 972, spacers 955 and side wall 972 forms a backlight with good mechanical strength.

[0084] The diffusing plate 938 can be a thick diffusing plate or comprises of a transparent plate 938a and one side or both sides diffusing layers 938b. In order to increase the brightness of the backlight, the diffusing plate 938 can also have a brightness enhancement function, e.g. with a brightness enhancement film.

[0085] The spacer 955 can be a transparent cone spacer or other shape spacer, which is made of a transparent material, e.g. plastic or glass. The top of the spacers 955 are polished, mounted and attached on the diffusing plate 938 by adhesive 956.

[0086] FIG. 9 shows an embodiment of a seamless OAM-LCD tiled LCD. 901a and 901b are two adjacent OAM-LCD tiles, which have thin front plate 904 and thin back plate 905, and are mounted on the diffusing plate 938 of the backlight 934 by adhesive, e.g. anisotropic adhesive. The thin front plate 904 and thin back plate 905 are made of glass or plastic, and their thicknesses range from 0.01 to 8 mm, to reduce obstruction of light from the backlight and the apparent seam width. The front and back plates can be very thin since they rely on the backlight for support so that they remain flat and uniform. 911 is LC cell, which with electrodes, filter, black matrix, alignment layer and LC layer. 908 is the sealing wall of LCD. 917 are the polarizers. 903 are the gaps between the adjacent LCD tiles. Adhesive 958 may fill gaps 903. The details of the gap and the LCD tile structure are shown in FIG. 10 which is an exploded view of a portion of the device in FIG. 9. The backlight can be made in any dimensions. A large backlight of the construction described herein can have a diagonal dimension of not less than 20 inches.

[0087] In FIG. 9, 961 are the OAM chips, which are mounted on the tile 901 by adhesive 956, e.g. anisotropic adhesive or wire bonding and adhesive. The chips 961 are connected to the row and column electrode driving electronics 974 through the hidden conductors 920 and conductors 975, which are deposited on the surface of the diffusing plate 938 of the backlight 934. 975 is preferably located underneath the black matric layer so that it does not block light from the back light towards the pixels. 936 is the display system driving circuit, for driving the common and addressing electrodes (not shown) and the light source 935.

[0088] FIG. 10 shows an enlarged cross-sectional view of the adjoining portions of two adjacent LCD tiles in the seamless tiled structure of FIG. 9. 1001a and 1001b are the adjacent tiles. 1004 and 1005 are the front plate and the back plate. 1008 is the sealing wall. 1006 and 1007 are the electrodes of LCD cell. 1011 is a LC layer, including transmissive LC, e.g. TN, STN and scattering LC, e.g. PD-LC. 1012 is the black matrix. 1030 is the color filter. The black matrix 1012 and the color filter 1030 can be located at the inside surface or outside surface of the front plate 1004 or the back plate 1005.

[0089] In FIG. 10, 1003 is the gap between two adjacent LCD tiles. 1076 is the polished side walls of the back plates 1005 of the two adjacent tiles. Between the side walls 1076, a transparent adhesive 1058, is filled. The refractive index of the adhesive 1058 is similar to the refractive index of the back plate 1005. 1077 is a soft black side wall of the LCD tile. The side wall 1077 is located at the top of the gap 1003 between the adjacent tiles. It can eliminate the leaking light from the backlight 1034 through the gap, and protect the LCD tiles from cracking, especially where the front plates 1004 are made of glass.

[0090] As shown in FIG. 10, the maximum angle &thgr; is the critical angle of the material of the back plate 1005. 1040 is the light from the backlight with the maximum incident angle. In order to get a seamless tiled display, the following conditions should be satisfied:

[0091] TF≦(M−H)/(2 tan&thgr;), where TF is the thickness of the front plate 1004, M is the width of the black matrix 1012, H is the width of the gap 1003;

[0092] W≦(M−H)/2, where W is the width of the sealing wall 1008;

[0093] P≦(M−H)/tan&thgr;, where P is the height of the soft side wall 1077.

[0094] From FIG. 10 we can see, if the thickness TB of the back plate 1005 is equal or less than (M−H)/(2 tan&thgr;), the transparent adhesive 1058 may be omitted in the gap 1003.

[0095] FIG. 11a shows a top view of the portion of another embodiment of a thin plastic LCD 1101, where the portion contains four pixels. FIG. 11b shows the cross-sectional view of the LCD. 1178 is one of the four pixels of the LCD, which can be a monochrome LCD or a color LCD which with R, G, B color filter. The thin front plate 1104 and the thin back plate 1105 of the LCD 1101 are plastic plates, e.g. polyester or polycarbinate film. 1111 is the LC cell, including electrodes, alignment layer, black matrix, and color filter, where these components are not separately shown. The LCD 1101 can be a transmissive LCD, reflective LCD or scattering LCD. 1117 are the polarizers. 1118 is the spacer of LCD.

[0096] The plastic LCD 1101 is sealed by laser beam during LCD device laser cutting. Because the thin front plate 1104 and thin back plate 1105 will be melted during laser cutting, a thin sealing wall 1108 will be formed along the cutting edge. The width of the sealing wall 1108 can be range of 0.01 to 10 mm. In other words, the LCD 1101 may be made by first aligning the LC cells 1111 between two large thin sheets of plastic materials. A laser beam may be directed towards the sheets to cut them into smaller pieces such as the LCD 1101, where by cutting along lines that form the edges of the smaller piece 1101, also seals the front and back sheets together to form the side sealing walls 1108 of the LCD 1101.

[0097] The plastic LCD 1101 also can be riveted by laser beam to increase the strength of the plastic LCD. 1179 are rivets formed by laser beam. By directing a laser beam towards the LCD 1101 at selected locations to drill holes at, for example 1180, the plastic material around the hole will melt to form one of the rivets 1179 bonding the front and back plates together. 1181 is the wall of the hole 1180 formed during hole laser drilling. Thus, the embodiment of FIGS. 11a, 11b is particularly easier to make.

[0098] FIG. 12 shows an another embodiment of a riveted plastic LCD 1201 that is substantially the same as the embodiment of FIGS. 11a, 11b, except that, instead of through holes in the LCD, the drilling laser does not drill all the way through, so that the area occupied by the rivet subsequently formed can be made smaller. Furthermore, the rivets will not be visible by the viewer even at fine resolution. In this embodiment, the back plate 1205 is thinner than the front plate 1204. The front plate and the back plate can be plastic films, e.g. polyester or polycarbinate film. 1211 is the LC cell, including electrodes, alignment layer, black matrix, color filter and LC layer. The LCD 1201 can be a transmissive LCD, reflective LCD or scattering LCD. 1217 are the polarizers. 1218 is the spacer of LCD. 1208 is the sealing wall formed by laser cutting. The laser drilling is started from the back plate using a small diameter laser beam. The laser beam do not make a through hole, and the drilling is stopped when both the front and back plates 1204, 1205 are melted and attached together at a point to form a rivet 1279 as shown in FIG. 12 without puncturing the front plate. A transparent adhesive 1256 can be filled in the pit 1282 drilled and left by laser beam to improve the brightness uniformity of the image. This structure and process can be used for making the high resolution plastic LCD and large screen plastic LCD, including transmissive LCD and reflective LCD, and can be used for making mosaic LCD and single piece LCD.

[0099] To make an even sturdier sealing wall between the front and back plate of the LCD, after the LC cells have been placed are aligned onto one large thin sheet of plastic material, an adhesive material may be applied along lines marking the boundaries of the smaller pieces into which the sheet is to be cut and another large sheet of plastic material is placed on top so that the adhesive material will bond the two sheets with the LC cells aligned between the two sheets. A laser beam may then be directed towards the locations along the two large sheets that are bonded by the plastic material, so as to melt the adhesive material together with the plastic material of the two thin sheets, thereby cutting the two large sheets along the lines of the adhesive material into smaller pieces and thereby securely bonding the smaller pieces together at the edges by bonding the adhesive material together with portions of the two thin sheets so that they form one integral piece at the edges of the smaller pieces.

[0100] Although the invention has been described in detail in the foregoing for purpose of illustration, it is to be understood that such details are solely for the purpose and that variations that may be made therein by those skilled in the art with out departing from the spirit and scope of the invention are described in the following claims.

Claims

1. A tiled active liquid crystal display device, comprising a plurality of LCD tiles, each tile comprising:

an active matrix liquid crystal display, said display having a thin front plate and liquid crystal (LC) cells;

a backlight with a light source;

means for applying the signals to said display to modulate transmittance of the liquid crystal (LC) cells, and of light from the backlight transmitted by said LC cells to display an image;

said device further comprising means assembling said LCD tiles to form a super-large-screen display.

2. The device of claim 1, wherein thickness of said thin front plate is in the range of about 0.02 to 0.7 mm.

3. The device of claim 1, wherein each of at least some of said LCD tiles has an outside active matrix control device mounted on an outside surface of such LCD tile.

4. The device of claim 3, wherein said outside active matrix control device is a field effect transistor, bipolar transistor, diode or varistor.

5. The device of claim 3, wherein said outside active matrix control device controls one LC cell or one group of LC cells.

6. The device of claim 1, wherein said light source is a cold cathode fluorescent lamp (CCF), hot cathode fluorescent lamp (HCFL) or light emitting diode (LED).

7. The device of claim 1, wherein said light source includes a white light source, and a color filter array on surfaces of said LCD tiles to display a multi-color or full-color image or characters etc.

8. The device of claim 1, wherein said light source comprises at least one set of red, green, blue (R, G, B) CCFLs or LEDs, and wherein said applying means causes said tiled LCD to be operated at a color sequential mode to display a full-color image or characters.

9. The device of claim 1, wherein said light source includes a driver for controlling light intensity, said driver including a brightness adjustment circuit for adjusting the brightness of said light source manually or automatically, to adjust brightness in order to enhance brightness uniformity across the LCD tiles.

10. A seamless active tiled LCD device, comprising:

a LCD with a thin front plate, a sealing side wall and a back plate, said LCD having a LC layer and pixels;

a thin sealing cover over the thin sealing wall of the LCD; and

an adhesive array having at least one spacer between the pixels and between the front and back plates to enhance thickness uniformity of the LC layer in the LCD.

11. The device of claim 10, wherein said front plate and back plate comprises a transparent substrate, said substrate including glass or plastic.

12. The device of claim 10, wherein said front plate and sealing wall form an integral piece or are two separate pieces.

13. The device of claim 10, wherein said outside sealing cover, which is an anti-reflective plate, a transparent or diffusing plate, or having the optical function to change the light direction, i.e. to change the viewing angle, e.g., micro-lens plate or holographic plate and the like.

14. The device of claim 10, wherein said LCD is an active LCD, the active matrix devices are mounted on the interior surface of the substrate of LCD or mounted on the outside of the substrate of LCD.

15. The device of claim 10, wherein a series of conductive pins hidden in the plate to connect the electrodes of LC cells and outside circuits to guarantee the reliability of the electric connection.

16. A tiled,.transparent LCD, comprising:

a transmissive LCD having a back plate with a side wall, and a reflective layer on the side wall of the back plate; and

a backlight;

said reflective layer reflecting light emitted from the backlight to reduce the apparent seam width of the LCD.

17. A tiled reflective LCD, comprising:

a transmissive LCD having a back plate with a side wall, and a reflective layer on the side wall of the back plate; and

a reflector located near the back plate of the LCD;

said reflective layer reflecting light reflected by the back reflector to reduce the apparent seam width of the tiled display.

18. A tiled active LCD display system comprising:

a display screen having N by M thin seamless active LCD tiles;

each tile having at least one backlight with a light source and driver and at least one connector;

a driving and control circuit;

wherein all tiles are connected to said circuit through said connector;

means for applying voltage and signals to the driving and control circuit and tiles to display information and images according to the signals.

19. A seamless tiled LCD, comprising:

a good mechanical strength backlight, which serves as a base plate of a display screen, said backlight comprising:

(a) at least one light source;

(b) a reflective chamber having a first and a second opposing surface and housing said light source, said first surface being flat;

(c) a good mechanical strength frame holding said chamber and said diffusing front plate;

at least one transparent spacer located between the opposing surfaces of said reflective chamber to maintain the flat shape of said first surface;

at least two thin LCD tiles, said tiles connected to the first surface so that they are supported by the first surface, said tiles having electrodes; and

at least one set of connectors located between said tiles to connect the electrodes of adjacent tiles.

20. The device of claim 19, further comprising a diffusing front plate, the first surface of said chamber being a surface of the diffusing front plate; and

means connecting said diff-using plate to the thin LCD tiles and to said backlight so that such plate is between the tiles and the backlight.

21. The device of claim 20, wherein said diffusing front plate includes a brightness enhancement film.

22. The device of claim 20, wherein said spacer is mounted on said diffusing front plate with transparent adhesive to obtain a shadowless backlight.

23. The device of claim 19, further comprising one or more optical plates adjacent to the tiles, said optical plate having the function of anti-reflection, diffusing, contrast enhancement or/and viewing angle changing.

24. The device of claim 23, wherein said front optical plate can be one piece for one screen or one piece for one tile.

25. The device of claim 19, wherein said at least one light source comprises at least one hot cathode fluorescent lamp, cold cathode fluorescent lamp or light emitting diode.

26. The device of claim 19, wherein each of at least some of said LCD tiles comprises a thin front plate and a thin back plate, wherein the thicknesses of these plates are in the range of about 0.02 to 5 mm.

27. The device of claim 19, wherein each of said LCD tiles is a transmissive LCD, reflective LCD or scattering LCD.

28. The device of claim 19, wherein each of at least some of said LCD tiles has LC cells a spacer mixed adhesive array located between said the front plate and back plate to keep the LC cells uniform in the whole tile.

29. The device of claim 19, wherein said LCD tile is an outside-active-matrix (OAM) LCD, including an active control device that includes a field effect transistor, bipolar transistor, diode, or varistor.

30. The device of claim 29, wherein said OAM device is at least one chip, one chip has at least one active device to control the related LC cell.

31. The device of claim 19, wherein said seamless tiled LCD is a color LCD, and a color filter array and a black matrix are deposited on the inside surface or outside of said thin front plate or back plate of said LCD tiles.

32. The device of claim 27, wherein said spacer mixed adhesive is still deposited at OAM mounted area between said thin front plate and thin back plate to increase the mechanical strength.

33. The device of claim 19, wherein said connector is made of a transparent substrate and at least one conductive means is deposited, and used for connecting the electrodes of the tiles between the adjacent tiles.

34. The device of claim 19, wherein said connectors have auxiliary electrical connectors, which are connected in parallel with the related column electrodes, row electrodes and the common electrodes to reduce the resistance of the electrodes and to increase the reliability of the connections.

35. A light utilization improved structure comprises:

a reflective 'matrix is deposited on the outside surface of the front plate of the backlight or on the outside surface of said thin back plate, said reflective matrix can reflect the light, which emitting to black matrix and could being absorbed by black matrix, to the backlight reflector to increase the light utilization factor of the backlight.

36. A seamless tiled LCD, comprising:

a good mechanical strength reflector, which is as a base plate of the display screen, and comprises of diffusing reflective plate or a mirror and a good mechanical strength frame.

at least two thin LCD tiles, said LCD tiles are mounted on the outside surface of said diffusing front plate;

at least one set of connector located between said tiles to connect the electrodes of the adjacent tiles; and

means mounting said thin LCD tiles on a good mechanical strength reflector, to form a thin profile, light weight and very strong large screen display.

37. The LCD of claim 36, further comprising a front optical plate, which has the function of anti-reflection, diffusing, contrast enhancement or/and viewing angle changing;

38. A sealing method for thin sealing wall LCD sealing, which comprises

a spacer mixed adhesive is deposited at the sealing area, e.g. by printing, between said thin front plate and thin back plate, then cured;

cutting by laser along the sealing wall;

means using laser cutting to form a very thin sealing wall, because the thin front plate and thin back plate will be melted during laser cutting. At the same time, at said cutting area still has sealing adhesive, different sealing wall can be obtained depending on sealing adhesive pattern design; the width of sealing wall van be range of 0.01 to 10 mm.

39. A large screen spacer-shadowless backlight, comprising:

at least one light source;

one front diff-using plate and one transparent back plate;

at least one transparent spacer located between said front diffusing plate and transparent back plate;

a side wall located at the four sides of the front diffusing plate and the transparent back plate and between said plates;

a reflective layer located at the outside of the back plate and the side wall to form a reflective chamber;

a good mechanical strength frame;

means the front diffusing plate, the transparent back plate, spacer, side wall, reflective layer and mechanical frame forming a large screen spacer-shadowless good mechanical strength backlight.

40. The device of claim 39, wherein said light source is HCFL, CCFL or LED.

41. The device of claim 39, wherein said front diffusing plate and transparent back plate have the same or similar coefficient of thermal expansion.

42. The device of claim 39, wherein said front diffusing plate and transparent back plate can be one piece plate or combined of two or more pieces plates.

43. The device of claim 39, wherein said spacer is a cone shape spacer or other shape spacer, and fixed on the inside surface of the front diffusing plate by transparent adhesive.

44. The device of claim 39, wherein a diagonal dimension of the backlight is not less than 20 inches.

45. A tiled LCD, comprising:

a large screen spacer-shadowless backlight;

at least two thin LCD tiles;

means mounting the tiles on the outside surface of the front diffusing plate of said backlight to form a tiled LCD.

46. The device of claim 45, wherein a diagonal dimension of the backlight is not less than 20 inches.

47. The device of claim 45, wherein a series of conductors are deposited on the outside of the front diffusing plate of said backlight, used for connecting tiles and connecting tiles to the driving electronics of the display system.

48. A sealing method for plastic LCD sealing, which comprises a front plastic plate and a back plastic plate, which with electrodes and other LCD parts, and aligned each other and fixed;

cutting by laser along the sealing area;

means using laser cutting to form a thin sealing wall at sealing area, because the front plate and back plate will be melted during laser cutting at sealing area, and a thin sealing wall will be formed. The width of the sealing wall can be range of 0.01 to 10 mm.

49. A riveted plastic LCD, which comprises

a front plastic plate and a back plastic plate, which with electrodes and other LCD parts, and aligned each other and fixed;

at least one rivet made by laser beam to melt said front plate and said back plate to form the rivet;

means making at least one rivet, riveting said front plate and said back plate to form a robust plastic LCD.

50. The device of claim 49, wherein said LCD can be a transmissive LCD, reflective LCD or scattering LCD.

51. The device of claim 49, wherein said rivet is a through hole drilling by laser beam, and along the hole has a thin sealing wall formed by the melted plastic, and formed the rivet.

52. The device of claim 49, wherein said back plastic plate is thinner than said front plastic plate. The laser drilling is started from the back plate using a small diameter laser beam. The laser beam do not make a through hole, the drilling is stopped at both of front plate and back plate are melted and attached together, and to form the rivet. This structure and process can be used for making the high resolution plastic LCD, and can be used for making mosaic LCD and single piece LCD.

53. The device of claim 49, wherein said back plastic plate and said back plate are a plastic film, e.g. polyester, polycarbinate or other plastic film.