FLAT PANEL LIGHT SOURCE FOR LIQUID CRYSTAL DISPLAYS

Abstract: A liquid crystal display is provided using a flat panel of microlamps being formed from gas discharge display structures and made by the method of making the same utilizing integrated circuit fabrication techniques. The flat panel of microlamps is formed into an array for providing light to individual pixels, or a small number of pixels, in a liquid crystal display. Such microlamp lighting can increase the illumination of LCDs.

Description: Flat panel light source for liquid crystal displays. The invention relates to a significantly improved liquid crystal display (LCD) having a flat panel of microlamps to provide the light source for the display. The use of a panel of microlamps, according to the present invention, in a flat panel array has been found to be extremely attractive for liquid crystal displays. The array of microlamps according to the present invention enables a higher screen brightness of optical transmission in Active Matrix Liquid Crystal Displays (AMLCDs). Typically, such AMLCDs have an optical transmission of less than 30% because of an array of colour filters and polarizers over the AMLCD. Further, use of TFT arrays in such displays causes a low aperture ratio. These problems of conventional AMLCDs require a high intensity light source, particularly in projection systems, in order to obtain a reasonable screen brightness. The array of individual micro-light sources of the present invention solves these problems. The individual microlamps have a reflector integrated with the micro-light source and a microlens to project and focus the light into each pixel or at most several pixels of the LCD. The combined array of individual microlamps provides a large area light display of high intensity light. This significantly improves the use of flat panel LC displays and enables improved projection displays as well as forming a useful area spot lighting arrangement. Accordingly, the present invention is directed to a flat panel light source of microlamps. In addition, the present invention is directed to a liquid crystal display having a flat panel light source. Further, the present invention is directed to an area lighting scheme using a microlamp arrays. In particular, the flat panel light source of the present invention comprises an array of microlamps having a micro-reflector for each microlamp light source cavity directing light through a micro-lens associated with the light source. An array of such microlamps is provided to direct light through a LCD, such as used in projection displays. Finally, such an array of microlamps according to the present invention is provided as an area lighting scheme. For better understanding of the invention, reference is made to the following drawings which are to be taken in conjunction with the detailed description to follow: Figure 1 is a cross-sectional view of a microlamp array according to the present invention; Figure 2 is a cross-sectional illustration of a microlamp array directing light to a projection LCD according to the present invention; Figure 3 is an illustration of a conventiorial HID lamp for area illumination; Figure 4 shows a microlamp array according to the present invention used for area illumination; and Figure 5 shows a cross-section of a display device incorporating a microlamp array of the invention. Figure 1 shows a partial cross-section of an array 400 of microlamps according to the present invention. This array has a number of microlamps 440 each formed by individual microlamps of a light source cavity 418, a reflective surface 420 and lens 430. This structure is similar to that found in U.S. patent application Serial No. (1504-0928, PHA 21.987 US) filed the same day as the present application and having common inventor Such an array of microlamps is used according to the present invention i a projection display, such as the LCD display in Figure 2. In this structure the microlamp array 400, according to the present invention, directs light from each microlamp to a liquid crystal panel 500. The LCD panel is formed of polarizers 510, TFT electrode structure 520 liquid crystal 530 and electrode 540. Images formed in the LC display are projected as ligh formed from each microlamp 440 through the liquid crystal panel 500 to a projection lens lens system 600, such as used in projection television devices. The individual light sources 440 from the array 400 provide high intensity illumination of the liquid crystal display which enhances the final image formed without loss of light as occurs in conventional schemes. That is, the optical transmission o Active Matrix Liquid Crystal Displays (AMLCD) is typically less than 30%. The use of individual microlamps as light sources for the LCD according to the present invention significantly improves light coupling from the light source into the LC display. Moreover, the individual light sources of the microlamp array of the present invention form an expanded light viewing angle for the LCD since each microlamp can focus light into individual pixels of the LCD or at most only several pixels, providing a significant increase in brightness. Thus, significant increases in the amount of light going through the LCD device occur. The formation of such microlamp arrays according to the present invention using ultra-violet (UV) light from fluorescent type light can produce significant increases in the use of AMLCDs. Such structures using florescent lighting for the individual microlamp light sources enable the provision of direct view flat panel light sources. The resulting structure then provides improved brightness, uniformity of the light and compactness of the display. The distance between the microlamp light array and the LC panel results in variable viewing angles of the display. A UV flat light source having florescent microlamps without phosphors can be used in such displays. In mis instance the colour phosphors for the display are formed in a pattern on the front of the LC panel and the LC modulates the UV light with the phosphor pattern converting the UV into visible light. Such an arrangement would provide a wide viewing angle light display. Figure 5 shows such a display device 800, in which flat panel light source fluorescent microlamp array 802 emits UV light, indicated by the solid arrows, which UV light is modulated by LC panel 804, indicated by me dashed arrows. The modulated UV light falls on patterned colour phosphor layer 806, containing phosphors which emit visible light, indicated by the solid arrows, upon excitation by the UV light. Relative to area displays Figure 3 shows a conventional high intensity discharge light source 700 having an HID lamp 710 within a reflector 720. This light source is used to provide area spot lighting. According to the present invention as seen in Figure 4, a microlamp array 400 is formed with a holding luminaire structure 810. Such an arrange¬ ment according to the present invention provides a higher lumen output of the lamps. Moreover, the microlamp structure of the present invention enables a predetermined illuminated area to be formed by the design of the optical elements. The above described structures and methodology are merely illustrative of the principles of the present invention. Numerous modifications and adaptations thereof will be readily apparent to those skilled in the art without departing from the spirit and scope of the present invention and the appended claims.

Claims: Claims: 1. A flat panel illumination device comprising an array of microlamps, each of said microlamps including a light source cavity, a reflector and a lens. 2. A lighting arrangement for liquid crystal displays comprising a liquid crystal panel, and an adjacently disposed illumination system including an array of microlamps, each of said microlamps including a light source cavity, a reflector and a lens. 3. An area lighting device comprising an array of microlamps within a luminaire structure, each of said microlamps including a light source cavity, a reflector and a lens. 4. Flat panel display device comprising an ultra violet light emitting microlamp array, a liquid crystal panel positioned in front of the array for modulating the ultra violet light in accordance widi a display signal, and a phosphor layer on the front of the liquid crystal panel for converting the modulated ultra violet light into visible light. 5. The flat panel display device of claim 4, in which the microlamp array comprises fluorescent microlamps. 6. The flat panel display device of claim 4 or 5, in which the liquid crystal panel is an active matrix liquid crystal display (AMLCD) panel. 7. The flat panel display device of claim 4, 5 or 6, in which the phosphor layer comprises a pattern of colour phosphors.

Inventors: CAMMACK DAVID A, JANSSEN PETER J, KHAN BABAR A, PINKER RONALD D, CAMMACK, DAVID, A., JANSSEN, PETER, J., KHAN, BABAR, A., PINKER, RONALD, D.
Applicants: PHILIPS ELECTRONICS NV, PHILIPS NORDEN AB, PHILIPS ELECTRONICS N.V.
Application year: 1996
Main classification: G09F9
IPC codes: G02F1