Abstract:
A liquid crystal panel unit comprising an LCD panel having a pair of substrates and a liquid crystal layer arranged between the substrates and a holding substrate for holding the LCD panel by rigidly securing one of the substrates thereto is characterized in that a plurality of protuberances are formed on the surface of the holding substrate at a side thereof and the one of the substrates is rigidly secured to the holding substrate with the side carrying the protuberances facing inside.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a liquid crystal panel unit and also to a liquid crystal projector using such a panel unit. More particularly, the present invention relates to a panel unit applicable to a reflection type LCD panel to be used in the image display section of a projection type image display apparatus such as a linear projection display for audiovisual (AV) applications or a data projector for displaying computer outputs. 
     2. Related Background Art 
     FIG. 3 of the accompanying drawings schematically illustrates a known image display apparatus (LCD panel unit) comprising an LCD panel and a substrate for holding the LCD panel (hereinafter referred as holding substrate). 
     Referring to FIG. 3, the LCD panel  5  is typically constituted by a liquid crystal drive substrate (active matrix substrate)  1  formed by arranging pixel electrodes into a matrix on a semiconductor substrate, an opposite substrate  2  having a transparent electrode and a liquid crystal layer  4  held between the liquid crystal drive substrate  1  and the opposite substrate  2  and securely bonded to said holding substrate  10  by way of an adhesive layer  8 . 
     With the above arrangement, the image displaying surface of the LCD panel  5  can show a varying height within the effective image area of the LCD panel  5  as observed from the rear surface of the holding substrate  10  due to the varying thickness of the adhesive layer  8  held between the LCD panel  5  and the holding substrate  10 . 
     The image projected for viewing by a projection display comprising such an LCD panel unit is in fact an image obtained by magnifying the one produced on the LCD panel  5  by means of the projection lens of the projection display. The sharpness of such an enlarged and projected image is determined, if partly, by the focal point of the image that has to be located on the screen. In other words, the sharpness of the image displayed by the projection display depends on if the image displaying surface of the LCD panel  5  is found within the depth of field of the projection lens or not. 
     Currently, there is a strong trend of down-sizing the LCD panel by densely arranging dimensionally reduced pixels on the LCD panel in order to meet the demand for high definition images to be realized by down-sized display apparatus. Additionally, to survive the highly competitive scene for the technological development of projection displays, the magnification of the projection lens has to be raised to produce a remarkably enlarged projected image. However, the depth of field of the projection lens is inevitably reduced if the plane of projection is held invariable while the magnification of the projected image is increased. Then, the LCD panel has to be accurately and securely held to the local point of the projection lens. A projection lens with a magnification of fifty times will be required to project an image from a 1-inch LCD panel onto a 50-inch screen, although the magnification may vary depending on the distance of projection and the performance of the lens. Thus, if a projection lens with a magnification of the order of tens is used to produce a bright image, the depth of field of the projection lens will be as small as tens of several microns. 
     However, as pointed out above, known LCD panels has an image displaying surface that can show a height that varies by tens to hundreds of microns as observed from the rear surface of the holding substrate. 
     Then, if the distance between the holding substrate and the projection lens is accurate, the projected image can become blurred, although partly. 
     Meanwhile, a projection display comprising an LCD panel is required to produce a highly bright projected image. Then, light from the light source has to be made to strike the LCD panel with an enhanced intensity. The intensity of light striking the LCD panel is also raised as the LCD panel is dimensionally reduced. As a result, the temperature of the LCD panel will inevitably be raised in operation. In the case of a known LCD panel having a 1.3-inch diagonal and provided with a 250 W metal halide lamp, the temperature of the LCD panel rises to about 40° C. when a thermally not-highly-conductive adhesive agent is used for the adhesive layer of the LCD panel. If the adhesive agent is made to contain a heat-emitting filler material, the temperature rise shows only a limited improvement and the temperature of the LCD panel is raised to about 35° C. in operation. 
     Therefore, the effect of the adhesive layer arranged between the holding substrate and the LCD panel for emitting heat from the LCD panel to the holding substrate is currently not satisfactory and the temperature rise entails problems including a degraded image quality. 
     Japanese Patent Application Laid-Open Nos. 55-65928, 7-84267 and 8-211351 disclose the use of spacers between the paired substrates carrying thereon a liquid crystal layer in order to realize a uniform thickness for the liquid crystal layer. However, the above listed patent documents do not refer to any of the above identified problems. 
     SUMMARY OF THE INVENTION 
     In view of the above described circumstances, it is therefore an object of the present invention to provide an LCD panel of the above identified type having an image displaying surface that shows a uniform height as observed from the rear surface of holding substrate. 
     Another object of the present invention is to provide an LCD panel that can effectively reduce its temperature by emitting heat to the holding substrate in operation. 
     According to the invention, the above objects and other objects of the invention are achieved by providing a liquid crystal panel unit comprising an LCD panel having a pair of substrates and a liquid crystal layer arranged between said substrates and a holding substrate for holding the LCD panel by rigidly securing one of said substrates thereto, characterized in that a plurality of protuberances are formed on the surface of said holding substrate at a side thereof and said one of the substrates is rigidly secured to said holding substrate with the side carrying said protuberances facing inside. 
     According to the invention, the image displaying section of the LCD panel can be made to show a uniform height as observed from the rear surface of the holding substrate by securing the LCD panel to the holding substrate. With the above arrangement, an enhanced degree of sharpness can be ensured for the projected image over the entire plane of display by controlling the distance between the holding substrate and the projection lens. 
     Additionally, according to the invention, the protuberances of the holding substrate and the LCD panel may be held in tight contact. According to the invention, it may be so arranged that an adhesive layer containing no filler material is pinched between the flat tops of the protuberances and the LCD panel while an adhesive layer containing a filler material is laid to fill the space unoccupied by the protuberances between the holding substrate and the LCD panel. With such an arrangement, heat can be emitted quickly and efficiently to the holding substrate if the temperature of the LCD panel rises. 
     The adhesive layer containing a filler material and showing an high thermal conductivity that fills the space unoccupied by the protuberances between the holding substrate and the LCD panel can effectively promote the emission of heat from the LCD panel to the holding substrate and lower the temperature of the LCD panel. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic lateral view of a first embodiment of reflection type LCD panel unit according to the invention, illustrating its structure. 
     FIG. 2 is a schematic lateral view of a second or third embodiment of reflection type LCD panel unit according to the invention, illustrating its structure. 
     FIG. 3 is a schematic lateral view of a known reflection type LCD panel unit, illustrating its structure. 
     FIG. 4 is a schematic illustration of a liquid crystal projector using a liquid crystal apparatus, showing the underlying concept. 
     FIG. 5 is a schematic block diagram of the internal circuit of a liquid crystal projector according to the invention. 
     FIGS. 6A,  6 B and  6 C are schematic illustrations of an embodiment of the optical system of a projection type liquid crystal display apparatus according to the invention. 
     FIGS. 7A,  7 B and  7 C are graphs showing the spectrum reflection characteristics of the reflective dichroic mirrors selectively used for the optical system of a projection type liquid crystal display apparatus according to the invention. 
     FIG. 8 is a schematic perspective view of the color separation illumination section of the optical system of a projection type liquid crystal display apparatus according to the invention. 
     FIG. 9 is a schematic cross sectional view of an embodiment of liquid crystal panel according to the invention. 
     FIGS. 10A,  10 B and  10 C are schematic illustrations of the principle of color separation and color synthesis, underlying a liquid crystal panel according to the invention. 
     FIG. 11 is an enlarged partial plan view of an embodiment of liquid crystal panel according to the invention. 
     FIG. 12 is a schematic illustration of part of the projection optical system of a projection type liquid crystal display apparatus according to the invention. 
     FIG. 13 is a schematic block diagram of the drive circuit of a projection type liquid crystal display apparatus according to the invention. 
     FIG. 14 is an enlarged partial plan view of an image projected on the display screen of a projection type liquid crystal display apparatus according to the invention. 
     FIG. 15 is an enlarged schematic partial plan view of another embodiment of liquid crystal panel according to the invention. 
     FIG. 16 is an enlarged schematic partial cross sectional view of another embodiment of liquid crystal panel according to the invention. 
     FIGS. 17A and 17B are an enlarged partial plan view and a schematic cross sectional view of still another embodiment of liquid crystal panel according to the invention. 
     FIG. 18 is a schematic illustration of the liquid crystal panel of a liquid crystal apparatus, showing how fluxes of light proceed. 
     FIG. 19 is a schematic illustration of the arrangement of color pixels of the liquid crystal panel of a liquid crystal apparatus. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     Now, a first embodiment of the invention will be described by referring to FIG. 1, which illustrates an LCD panel  5  comprising a liquid crystal drive substrate  1  prepared by means of the semiconductor technology and an opposite substrate  2  having a transparent electrode  3  (not shown) with a liquid crystal layer  4  interposed therebetween. 
     The LCD panel  5  is held by protuberances  7  formed on a holding substrate  6  and operating as spacers and firmly secured to the latter by means of an adhesive layer  8 . The holding substrate  6  is punched out of a sheet of steel containing Ni—Cr alloy by means of a press to define the contour and then protuberances are produced by embossing. The protuberances  7  have the size of about 0.5 mm square and are arranged at regular intervals of 1 mm on the holding substrate  6 . 
     The top of each of the protuberances  7  is scraped off by means of a grinder so that they show a uniform height as observed from the rear surface of the holding substrate  6 . For this embodiment, a 0.7 mm thick steel sheet was used for the holding substrate  6 , which was embossed to produce protuberances  7  having a height of 0.1 mm and subsequently machined with an accuracy of 0.78±0.01 mm. As a result, a holding substrate  6  having spacers of 0.08±0.01 mm was obtained. 
     A thermosetting adhesive agent containing a heat emitting filler material (SE3880: tradename, available from Toshiba Silicon) was applied to the surface of the holding substrate  6  except the protuberances  7  produced by embossing while an adhesive agent containing no filler material was applied to the tops of the protuberances  7  and the LCD panel  5  was bonded to the holding substrate  6  by pressing them together with a force of 2 kg for 2 hours at constant temperature of 65° C. to allow the adhesive layer to set. As a result, a reflection type LCD panel unit comprising the LCD panel  5  whose image display surface is held to a position separated from the rear surface of the holding substrate  6  by 1.48±0.01 mm was prepared. 
     The prepared reflection type LCD panel unit was then fitted to a projection unit and an image was projected onto it from a display apparatus to find that an entirely and perfectly focused sharp image was produced. The temperature rise of the LCD panel  5  did not exceed 25° C. so that the LCD panel  5  kept on displaying a clear projected image and the quality of the displayed image was not degraded with time. For the purpose of the invention, it is recommended to use a metal material for the holding substrate because the material of the holding substrate has to be precision machined. While an appropriate metal material may be selected depending on the requirements to be met by the holding substrate, preferable candidates include copper, aluminum and alloys containing them as principal ingredients particularly when the material of the holding substrate is required to show a high thermal conductivity. Candidate materials having a low coefficient of thermal expansion include alloys of Permalloy (Ni—Cr alloy, 42 alloy, etc.) such as invar alloys. 
     Second Embodiment 
     Now, a second embodiment of the invention will be described by referring to FIG. 2, which illustrates an LCD panel  5  comprising a liquid crystal drive substrate  1  prepared by means of the semiconductor technology and an opposite substrate  2  having a transparent electrode  3  (not shown) with a liquid crystal layer  4  interposed therebetween. 
     The LCD panel  5  is held by protuberances  7  formed on a holding substrate  9  and operating as spacers and firmly secured to the latter by means of an adhesive layer  8 . The holding substrate  9  is produced by aluminum die casting and provided on the surface with protuberances  7 . The protuberances  7  have a diameter of about 0.5 mmφ and are arranged at regular intervals of 1 mm on the holding substrate  9 . 
     The tops the protuberances  7  are worked to make them show a uniform height as observed from the rear surface of the holding substrate  9 . For this embodiment, a 0.7 mm thick sheet-like die having 0.1 mm protuberances  7  was prepared and molten aluminum was poured into the die to produce a holding substrate  9  by die casting. The rear surface of the holding substrate  9  and the tops of the protuberances  7  were scraped off and subsequently the holding substrate  9  was subsequently machined with an accuracy of 0.78±0.01 mm. As a result, a holding substrate  9  having spacers of 0.08±0.01 mm was obtained. 
     A thermosetting adhesive containing a heat emitting filler material (SE3880: tradename, available from Toshiba Silicon) was applied to the surface of the holding substrate  9  except the worked protuberances  7  while an adhesive agent containing no filler material was applied to the tops of the protuberances  7  and the LCD panel  5  was bonded to the holding substrate  9  by pressing them together with a force of 2 kg for 2 hours at constant temperature of 65° C. to allow the adhesive layer to set. As a result, a reflection type LCD panel unit comprising the LCD panel  5  whose image display surface is held to a position separated from the rear surface of the holding substrate  6  by 1.48±0.01 mm was prepared. 
     The prepared reflection type LCD panel unit was then fitted to a projection unit and an image was projected onto it from a display apparatus to find that an entirely and perfectly focused sharp image was produced. The temperature rise of the LCD panel  5  did not exceed 25° C. so that the LCD panel  5  kept on displaying a clear projected image and the quality of the displayed image was not degraded with time. The second embodiment was rated higher than the first embodiment because the holding substrate was made of aluminum to improve the thermal conductivity. 
     Third Embodiment 
     The third embodiment of the invention has a configuration similar to that of the second embodiment. The LCD panel  5  of this embodiment comprises a liquid crystal drive substrate  1  prepared by means of the semiconductor technology and an opposite substrate  2  having a transparent electrode  3  (not shown) with a liquid crystal layer  4  interposed therebetween. 
     The LCD panel  5  is held by protuberances  7  formed on a holding substrate  9  and operating as spacers and firmly secured to the latter by means of an adhesive layer  8 . The holding substrate  9  of the third embodiment is produced by cutting an aluminum blank to produce a holding substrate  9  having protuberances  7  on the surface. The protuberances  7  have a diameter of about 0.5 mmφ and are arranged at regular intervals of 1 mm on the holding substrate  9 . 
     The tops the protuberances  7  are worked to make them show a uniform height as observed from the rear surface of the holding substrate  9 . For this embodiment, a 0.7 mm thick sheet-like die having 0.1 mm protuberances  7  was prepared by cutting an aluminum blank. Additionally, the rear surface of the holding substrate  9  and the tops of the protuberances  7  were scraped off and subsequently the holding substrate  9  was subsequently machined with an accuracy of 0.78±0.01 mm. As a result of the above process, a holding substrate  9  having spacers of 0.08±0.01 mm was obtained. 
     A thermosetting adhesive containing a heat emitting filler material (SE3880: tradename, available from Toshiba Silicon) was applied to the surface of the holding substrate  9  except the worked protuberances  7  while an adhesive agent containing no filler material was applied to the tops of the protuberances  7  and the LCD panel  5  was bonded to the holding substrate  9  by pressing them together with a force of 2 kg for 2 hours at constant temperature of 65° C. to allow the adhesive layer to set. As a result, a reflection type LCD panel unit comprising the LCD panel  5  whose image display surface is held to a position separated from the rear surface of the holding substrate  6  by 148±0.01 mm was prepared. 
     The prepared reflection type LCD panel unit was then fitted to a projection unit and an image was projected onto it from a display apparatus to find that an entirely and perfectly focused sharp image was produced. The temperature rise of the LCD panel  5  did not exceed 25° C. so that the LCD panel  5  kept on displaying a clear projected image and the quality of the displayed image was not degraded with time. The third embodiment was rated as high as the second embodiment because the holding substrate  9  was made of aluminum to improve the thermal conductivity. 
     Fourth Embodiment 
     Now, an optical system to which the fourth embodiment of reflection type liquid crystal panel is incorporated will be described by referring to FIG.  4 . Referring to FIG. 4, there are shown a light source  371  which may be a halogen lamp, a condenser  372  for converging rays of light coming from the light source, a pair of plane convex Fresnel lenses  373 ,  375 , a color separating optical device  374  for separating light into R, G and B, which may advantageously be a dichroic mirror or a diffraction grating. 
     There are also shown a mirror unit  376  for leading separated R, G and B lights respectively to R, G and B panels, a finder lens  377  for collimating convergent rays of light before illuminating the reflection type liquid crystal panel, a reflection type liquid crystal device  378  having an LCD panel unit arranged at a predetermined position as described above by referring to the first through third embodiments and a diaphragm section  379 . Additionally, there are also shown a projection lens  380  realized by combining a plurality of lens to operate as magnifier and a screen  381  that can display clear, bright and contrasty images when constituted by a Fresnel lens for collimating projected light and a lenticular lens for providing a wide viewing angle both vertically and horizontally. Note that, while FIG. 4 illustrates only a single panel for a single color, rays of light of three separated colors proceeds between the color separating optical device  374  and the diaphragm section  379  and actually three panels are required. However, it may be needless to say that the three panels can be replaced by a single panel by arranging a micro-lens array on the surface of the panel of the reflection type liquid crystal device to make different rays of incident light strike respectively different pixel regions. As a voltage is applied to the liquid crystal layer of the liquid crystal device, rays of light reflected by the pixels passes the diaphragm section  379  before they are projected onto the screen. 
     While no voltage is applied and the liquid crystal is a scattering body, rays of light entering the reflection type liquid crystal device are scattered isotropically so that only scattered rays of light directed to the aperture of the diaphragm section  379  can enter the projection lens. Only black will be displayed under this condition. As will be understood from the above description on the optical system, no polarization panel is required for the system. Additionally, since signal light is reflected by the entire surface of the pixel electrode before entering the projection lens, this arrangement can display an image brighter by two to three times than any comparable conventional arrangement. As described above, anti-reflection measures are taken on the surface and the interface of the opposite substrate so that noise factors are minimized for light and contrasty images can be displayed on the screen. Additionally, all the optical devices (lenses, mirrors, etc.) can be down-sized to reduce the cost and the weight because a small panel can be used. 
     Shadings and fluctuations of light and color of the light source can be prevented from being reflected on the screen by arranging an integrator (fly eye lens type, rod type) between the light source and the optical system. 
     Now, the peripheral electric circuit other than the liquid crystal panel will be described by referring to FIG.  5 . In FIG. 5, there are shown a bipartite power source  385  for supplying power to the lamps and also to the drive system for driving the panels and the signal processing circuit, a plug  386  and a lamp temperature sensor  387  adapted to cause the control board  388  to deenergize any lamps whose temperature is detected to be abnormal. The filter safety switch  389  is also controlled by the control board  388 . For example, if the lamp house box show high temperature, the box cannot be opened by way of precaution. Reference numeral  390  denotes a loudspeaker and reference numeral  391  denotes a sound board that can contain a processor for 3D sounds and surround sounds if required. Reference numeral  392  denotes extension board  1  having input terminals for receiving signals from S terminals and other external sources  396  of signals for composite images and sounds, a selection switch  395  for selecting a signal and a tuner  394 . Signals are sent from there to extension board  2  by way of a decoder  393 . The extension board  2  has Dsub 15  pin terminals to be connected to external video signal sources and computers and signals are converted into digital signals by an A/D converter  451  by way of a switch  450  for selecting the video signal from the decoder  393 . 
     Reference numeral  453  denotes a main board comprising a CPU and memories including a video RAM as principal components. The NTSC signals subjected to A/D conversion by the A/D converter  451  are temporarily stored in a memory and additional signals are generated by interpolation for vacant liquid crystal elements to satisfactorily assign signals to the large number of pixels for high definition, while other signal processing operations proceed, including gamma conversion edge gradation, brightness adjustment and bias adjustment. If high resolution XGA panels are used and computer signals such as VGA signals are applied in stead of NTSC signals, a resolution conversion processing operation will also be conducted on the main board. The main board  453  also operate for synthetically combining NTSC signals of data not only for a single image but also for a plurality of images with computer signals. The output of the main board  453  is subjected to a serial/parallel conversion and applied to the head board  454  in a form less adversely affected by noises. The head board  454  operates for carrying out a parallel/serial conversion and a D/A conversion for the output signal, which is divided according to the number of video lines of the panels and the signal is written onto the liquid crystal panels  455 ,  456  and  457  of B, G and R by means of respective drive amplifiers. Reference numeral  452  denotes a remote control panel with which computer images can be manipulated like TV images. The liquid crystal panels  455 ,  456  and  457  have an identical configuration that are same as the liquid crystal (LCD) panel described above for each of the first through third embodiments and provided with respective color filters of the corresponding colors. As described above, this embodiment of display apparatus can display neat and clear images. 
     Fifth Embodiment 
     FIGS. 6A,  6 B and  6 C are schematic illustrations of an embodiment of the optical system of a front and back projection type liquid crystal display apparatus according to the invention. FIG. 6A shows a plan view, FIG. 6B shows a front view and FIG. 6C shows a side view. Referring to FIGS. 6A,  6 B and  6 C, ther are shown a projection lens  1301  for projecting an image on the screen, a liquid crystal panel  1302  having a micro-lens, a polarization beam splitter (PBS)  1303 , an R (red light) reflecting dichoric mirror  1340 , a B/G (blue and green light) reflecting dichroic mirror  1341 , a B (blue light) reflecting dichroic mirror  1342 , a white light reflecting high reflection mirror  1343 , a Fresnel lens  1350 , a convex lens  1351 , a rod type integrator  1306 , an elliptic reflector  1307 , an arc lamp  1308  of, for example, metal halide or UHP. Note that the R (red light) reflecting dichroic mirror  1340 , the B/G (blue and green light) reflecting dichroic mirror  1341  and the B (blue light) reflecting dichroic mirror  1342  have respective spectrum reflection characteristics illustrated in FIGS. 7A,  7 B and  7 C. The dichroic mirrors and the high reflection mirror  1343  are three-dimensionally arranged as shown in the perspective view of FIG. 8 to divide illuminated white light and separate R, G and B light as will be described hereinafter and cause rays of light of the three primary colors to irradiate the liquid crystal panel  1302  with respective angles that are three-dimensionally different from each other. 
     The operation of the optical system will be described in terms of the proceeding route of a flux of light. Firstly, the flux of light emitted from the lamp  1308  of the light source of the system is that of white light and converged by the elliptic reflector  1307  toward the inlet port of the integrator  1306  arranged in front of it. As the flux of light proceeds through the integrator  1306  with repeated reflections, the spatial intensity distribution of the flux of light is uniformized. After coming out of the integrator  1306 , the flux of light is collimated along the x-direction (as shown in the front view of FIG. 6B) by the convex lens  1351  and the Fresnel lens  1350  before getting to the B reflecting dichroic mirror  1342 . Only B light (blue light) is reflected by the B reflecting dichroic mirror  1342  and directed to the R reflecting dichroic mirror  1340  along the z-axis or downwardly in FIG. 6B, showing a predetermined angle relative to the z-axis. 
     Meanwhile, light than B light (R/G light) passes through the B reflecting dichroic mirror  1342  and reflected rectangularly by the high reflection mirror  1343  into the direction of the z-axis (downwardly) and also directed to the R reflecting dichroic mirror  1340 . Referring to the front view of FIG. 6A, both the B reflecting dichroic mirror  1342  and the high reflection mirror  1343  are arranged to reflect the flux of light coming from the integrator  1306  (along the direction of the x-axis) into the direction of the z-axis (downwardly), the high reflection mirror  1343  being tilted around the axis of rotation, or the y-axis, exactly by 45 relative to the x-y plane. On the other hand, the B reflecting dichroic mirror  1342  is tilted around the axis of rotation, or the y-axis, by an angle less than 45° relative to the x-y plane. Thus, while R/G light reflected by the high reflection mirror  1343  is directed rectangularly toward the z-axis, B light reflected by the B reflecting dichroic mirror  1342  is directed downwardly, showing a predetermined angle relative to the z-axis (tilted in the x-z plane). Note that the extent of shifting the high reflection mirror  1343  and the B reflecting dichroic mirror  1342  relative to each other and the angle of tilt of the B reflecting dichroic mirror will be so selected that the principal beams of light of the three primary colors intersect each other on the liquid crystal panel  1302  in order to make B light and R/B light show an identical coverage on the liquid crystal panel  1302 . 
     The downwardly directed fluxes of R/G/B light (along the z-axis) then proceeds to the R reflecting dichroic mirror  1340  and the B/G reflecting dichroic mirror  1341 , which are located below the B reflecting dichroic mirror  1342  and the high reflection mirror  1343 . The B/G reflecting dichroic mirror  1341  is tilted around the axis of rotation, or the x-axis by  450  relative to the x-z plane, whereas the R reflecting dichroic mirror  1340  is tilted around the axis of rotation, or the x-axis, by an angle less than 45° relative to the x-z plane. Thus, of the incoming fluxes of R/G/B light, those of B/G light firstly pass through the R reflecting dichroic mirror  1340  and reflected rectangularly by the B/G reflecting dichroic mirror  1341  into the positive direction of the y-axis before they are polarized and illuminate the liquid crystal panel  1302  arranged horizontally on the x-z plane. Of the fluxes of B/G light, that of B light shows a predetermined angle relative to the x-axis (tilted in the x-z plane) so that, after having been reflected by the B/G reflecting dichroic mirror  1341 , it maintains the predetermined angle relative to the y-axis (tilted in the x-y plane) and illuminates the liquid crystal panel  1302  with an angle of incidence equal to the predetermined angle (relative to the x-y plane). 
     On the other hand, the flux of G light is reflected rectangularly by the B/G reflecting dichroic mirror  1341  and proceeds into the positive direction of the y-axis before it is polarized and hits the liquid crystal panel  1302  perpendicularly with an angle of incidence of 0°. The flux of R light is reflected by the R reflecting dichroic mirror  1340  which is arranged upstream relative to the B/G reflecting dichroic mirror  1341  as pointed out above into the positive direction of the y-axis and proceeds along the positive direction of the y-axis, showing a predetermined angle relative to the y-axis (titled in the y-z plane) as shown in FIG. 6C (lateral view) before it is polarized by the PBS  1303  and hits the liquid crystal panel  1302  with an angle incidence equal to the predetermined angle (relative to the y-z plane). As pointed out above, the extent of shifting the B/G reflecting dichroic mirror  1341  and the R reflecting dichroic mirror  1340  relative to each other and the angle of tilt of the R reflecting dichroic mirror will be so selected that the principal beams of light of the three primary colors intersect each other on the liquid crystal panel  1302  in order to make the fluxes of R/G/B light show an identical coverage on the liquid crystal panel  1302 . 
     Referring to FIGS. 7A,  7 B and  7 C, the cutting frequency of the B reflecting dichroic mirror  1342  is 480 nm as shown in FIG.  7 A and that of the B/G reflecting dichroic mirror  1341  is 570 nm as shown in FIG. 7B, whereas that of the R reflecting dichroic mirror  1340  is 600 nm. Thus, unnecessary orange light is discarded after passing through the B/G reflecting dichroic mirror  1341  to realize an optimal color balance. 
     As described in greater detail hereinafter, rays of R/G/B light are reflected and polarized for modulation by the liquid crystal panel  1302  and return to the PBS  1303 , where the fluxes reflected into the positive direction of the x-axis by the PBS plane  1303   a  of the PBS  1303  are used as light for producing enlarged and projected images on the screen (not shown) by way of the projection lens  1301 . Since the fluxes of R/G/B light striking the liquid crystal panel  1302  have respective angles of incidence that are different from each other, the fluxes of light reflected by it and coming out therefrom shows respective angles that are also different from each other. However, the projection lens  1301  has a lens diameter and an aperture that are large enough for accommodating the differences. Note that the fluxes of light striking the projection lens  1301  are collimated as they pass through the micro-lens array twice per each to maintain a predetermined angle for striking the liquid crystal panel  1302 . 
     With a known transmission type liquid crystal display apparatus as shown in FIG. 14, the flux of light exiting the liquid crystal panel is diametrically significantly enlarged partly due to the converging effect of the micro-lens array so that the projection lens for catching the flux is required to have a greater numerical aperture, making the projection lens costly. On the other hand, with this embodiment, the expansion of the flux of light coming from the liquid crystal panel  2  is relatively limited so that a sufficiently bright image can be projected on the screen by using a projection lens having a relatively small numerical aperture. While a stripe type display mode using vertically long stripes of same colors as shown in FIG. 19 may be used for this embodiment, such a mode of display is not preferable for a liquid crystal panel using a micro-lens array as will be described hereinafter. 
     Now, the liquid crystal panel  1302  of this embodiment will be described. FIG. 9 is an enlarged schematic cross sectional view of the liquid crystal panel  1302  (taken along the y-z plane of FIG.  8 ). Referring to FIG. 9, there are shown a micro-lens substrate  1321 , a number of micro-lenses  1322 , a sheet glass  1323 , a transparent opposite electrode  1324 , a liquid crystal layer  1325 , a number of pixel electrodes  1326 , an active matrix drive circuit  1327  and a silicon semiconductor substrate  1328 . Reference numeral  1352  denotes a peripheral seal section. In this embodiment, R, G and B pixels are intensively arranged on a single panel so that each single pixel inevitably has reduced dimensions. Thus, it is important that the panel shows a large aperture ratio and a reflection electrode should be found within the area covered by converged light so that the use of any of the arrangements of the first through fifth embodiments is significant for this embodiment. The micro-lenses  1322  are formed on the surface of a glass substrate (alkali glass)  1321  by means of a so-called ion-exchange technique and arranged in two-dimensional array at a pitch twice as high as that of the pixel electrodes  1326 . 
     ECB mode nematic liquid crystal such as DAP or HAN that is adapted to a reflection type display is used for the liquid crystal layer  1325  and a predetermined orientation is maintained by means of an orientation layer (not shown). It will be appreciated that the circuit configuration and other arrangement of this invention is highly effective particularly for this embodiment because a voltage lower than its counterpart of the fourth embodiment is used in this embodiment and hence the accuracy of the potential of the pixel electrodes  1326  is highly important. Additionally, the LCD panel unit of any of the first through third embodiments may effectively be used for this embodiment because a large number of pixels are arranged on a single panel in this embodiment. The pixel electrodes  1326  are made of aluminum and operate as reflector. Therefore, they are processed by a so-called CMP treatment technique after the patterning operation in order to improve the smoothness and the reflectivity of the surface. 
     The active matrix drive circuit  1327  is a semiconductor circuit arranged on the silicon semiconductor substrate  1328  to drive the pixel electrodes  1326  in an active matrix drive mode. Thus, gate line drivers (vertical registers, etc.) and signal line drivers (horizontal registers, etc.) (not shown) are arranged in the peripheral area of the circuit matrix (as will be discussed in detail hereinafter). The peripheral drivers and the active matrix drive circuit are so arranged as to write primary color video signals of RGB on the respective RGB pixels in a predetermined fashion. Although the pixel electrodes  1326  are not provided with color filters, they are identified respectively as RGB pixels by the primary color image signals to be written onto them by said active matrix drive circuit as they are arranged in array. 
     Take, for example, rays of G light that illuminate the liquid crystal panel  1302 . As described above, G light is polarized by the PBS  1303  and then perpendicularly strikes the liquid crystal panel  1302 . FIG. 9 shows a beam of G light that enters the micro-lens  1322   a  in a manner as indicated by arrow G (in/out). As shown, the beam of G light is converged by the micro-lens  1322  to illuminate the surface of the G pixel electrode  1326   g  before it is reflected by the aluminum-made pixel electrode  1326 G and goes out of the panel through the same micro-lens  1322   a . As the beam of G light (polarized light) moves through the liquid crystal layer  1325 , it is modulated by the electric field generated between the pixel electrode  1326   g  and the opposite electrode  1324  by the signal voltage applied to the pixel electrode  1326   g  before it returns to the PBS  1303 . 
     Thus, the quantity of light reflected by the PBS surface  1303   a  and directed to the projection lens  1301  changes depending on the extent of modulation to define the gradation of the related pixel. On the other hand, R light enters the cross sectional plane (the y-z plane) of FIG. 9 slantly in a manner as described above after having been polarized by the PBS  1303 . Take, now, a beam of R light striking the micro-lens  1322   b . It is converged by the micro-lens  1322   b  in a manner as indicated by arrow R (in) in FIG. 9 to illuminate the surface of the R pixel electrode  1326   r  located at a position shifted to the left in FIG. 9 from the spot right below it before it is reflected by the pixel electrode  1326   r  and goes out of the panel through the adjacently located micro-lens  1322   a  (in the negative direction of the z-axis) (R(out)). 
     As in the case of G light described above, as the beam of R light (polarized light) moves through the liquid crystal layer, it is modulated by the electric field generated between the pixel electrode  1326   r  and the opposite electrode  1324  by the signal voltage applied to the pixel electrode  1326   r  before it goes out of the liquid crystal panel and returns to the PBS  1303 . Then, as described above in terms of G light, light from the pixel is projected through the projection lens  1301 . While the beams of G light and R light on the pixel electrodes  1326   g  and  1326   r  may appear overlapping and interfering with each other in FIG. 9, it is because the liquid crystal layer is shown excessively thick, although it has a thickness between 1 and 5 μm in reality, which is very small if compared with the sheet glass  1323  having a thickness between 50 and 100 μm so that no such interference actually takes place regardless of the size of each pixel. 
     FIGS. 10A,  10 B and  10 C are schematic illustrations of the principle of color separation and color synthesis, underlying the liquid crystal panel  1302  of this embodiment. FIG. 10A is a schematic plan view of the liquid crystal panel, whereas FIGS. 10B and 10C respectively show schematic cross sectional views taken along line  10 B— 10 B (along the x-direction) and line  10 C— 10 C (along the z-direction) of FIG.  10 A. As indicated by dotted broken lines in FIG. 10A, each micro-lens  1322  corresponds to a half of a set of two-color pixels adjacently located with a G light pixel arranged at the center. Note that FIG. 10C corresponds to the cross sectional view of FIG. 9 taken along the y-z plane and shows how beams of G light and R light enter and go out from the respective micro-lenses  1322 . As seen, each G pixel electrode is located right below a corresponding micro-lens and each R pixel electrode is located right below the boundary line of corresponding two adjacent micro-lenses. Therefore, the angle of incidence θ of R light is preferably so selected that tan θ is equal to the ratio of the pitch of pixel arrangement (B and R pixels) to the distance between the micro-lenses and the pixel electrode. On the other hand, FIG. 10B corresponds to a cross section of the liquid crystal panel  1302  taken along the x-y plane. As for the cross section along the x-y plane, it will be understood that B pixel electrodes and G pixel electrodes are arranged alternately as shown in FIG.  10 C and each G pixel electrode is located right below a corresponding micro-lens whereas each B pixel electrode is located right below the boundary line of corresponding two adjacent micro-lenses. 
     B light for irradiating the liquid crystal panel enters the latter slantly as viewed from the cross section (the x-y plane) of FIGS. 6A,  6 B and  6 C after having been polarized by the PBS  1303  as described above. Thus, just like R light, each beam of B light entering from a corresponding micro-lens  1322  is reflected by a corresponding B pixel electrode  1326   b  as shown and goes out of the panel through the adjacently located micro-lens  1322  in the x-direction. The mode of modulation by the liquid crystal on the B pixel electrodes  1326   b  and that of projection of B light coming out of the liquid crystal panel are same as those described above by referring to G light and R light. 
     Each B pixel electrode  1326  is located right below the boundary line of corresponding two adjacent micro-lenses. Therefore, the angle of incidence θ of B light is preferably so selected that tan θ is equal to the ratio of the pitch of pixel arrangement (G and B pixels) to the distance between the micro-lenses and the pixel electrode. The pixels of the liquid crystal panel of this embodiment are arranged RGRGRG . . . in the z-direction and BGBGBG . . . in the x-direction. FIG. 10A shows the pixel arrangement as viewed from above. As seen, each pixel has a size equal to a half of a micro-lens for both longitudinally and transversally so that the pixels are arranged at a pitch twice as high as the micro-lenses. As viewed from above, each G pixel is located right below a corresponding micro-lens, while each R pixel is located right below the boundary line of corresponding two adjacent micro-lenses in the z-direction and each B pixel is located right below the boundary line of corresponding two adjacent micro-lenses in the x-direction. Each micro-lens has a rectangular contour (and is twice as large as a pixel). 
     FIG. 11 is an enlarged partial plan view of the liquid crystal panel of this embodiment. Each square  1329  defined by broken lines indicates a unit of RGB pixels. In other words, when the RGB pixels of the liquid crystal panel are driven by the active matrix drive circuit section  1327 , the unit of RGB pixels in each broken line square  1329  is driven by corresponding RGB picture signals. Now, take the picture unit of R pixel electrode  1326   r , G pixel electrode  1326   g  and B pixel electrode  1326   b . The R pixel electrode  1326   r  is illuminated by R light coming from the micro-lens  1322   b  and striking the pixel electrode aslant as indicated by arrow r 1  and reflected R light goes out through the micro-lens  1322   a  as indicated by arrow r 2 . The B pixel electrode  1326   b  is illuminated by B light coming from the micro-lens  1322   c  and striking the pixel electrode aslant as indicated by arrow b and reflected B light goes out through the micro-lens  1326   a  as indicated by arrow b 2 . Finally, the G pixel electrode  1326   g  is illuminated by G light coming from the micro-lens  1322   a  and striking the pixel electrode perpendicularly (downwardly in FIG. 11) as indicated by arrow g 12  showing only the back and reflected G light goes out through the same micro-lens  1322   a  perpendicularly (upwardly in FIG.  11 ). 
     Thus, while the beams of light of the three primary colors striking the picture unit of RGB pixels enters through different micro-lenses, they go out through a same micro-lens ( 1322   a ). The above description applies to all the picture unit (of RGB pixels) of the embodiment. 
     Therefore, when light emitted from the liquid crystal panel of this embodiment is projected onto the screen  1309  by way of the PBS  1303  and the projection lens  1301  in such a way that a focused image of the micro-lenses  1322  of the liquid crystal panel  1302  is projected on the screen by regulating the optical system, the projected image will show the picture units of RGB pixels for the corresponding respective micro-lenses as perfect white light obtained by mixing the beams of light of the three primary colors. The net result will be the display of high quality color images free from the mosaic of RGB as shown in FIG. 19 for a conventional liquid crystal panel. 
     As the active matrix drive circuit  1327  is located under the pixel electrodes  1326  as shown in FIG. 9, the drain of each pixel FET is connected to the corresponding one of the RGB pixel electrode electrodes arranged two-dimensionally as shown in FIG.  11 . 
     FIG. 13 is a schematic block diagram of the drive circuit of the embodiment of projection type liquid crystal display apparatus. Reference numeral  1310  denotes a panel driver for inverting the polarity of each RGB picture signal and producing liquid crystal drive signals with a voltage amplified in a predetermined fashion and also drive signals and various timing signals for the opposite electrode  1324 . Reference numeral  1312  denotes an interface for decoding various picture signals and control transmission signals into standard picture signals and standard control signals respectively. Reference numeral  1311  denotes a decoder for decoding/transforming the standard picture signals from the interface  1312  into picture signals for the RBG primary colors and synchronizing signals, or video signals adapted to the liquid crystal panel  1302 . Reference numeral  1314  denotes a lighting circuit for driving and lighting the arc lamp  1308  in the elliptic reflector  1307 . Reference numeral  1315  denotes a power supply circuit for feeding the circuit blocks with power. Reference numeral  1313  denotes a controller containing a control panel (not shown) for comprehensively controlling the circuit blocks. Thus, it will be seen that a projection type liquid crystal display apparatus according to the invention comprises a drive circuit that is rather popular and common to any known single panel type projectors. In other words, a liquid crystal display apparatus according to the invention can display high quality images free from the mosaic of RGB as shown in FIG. 19 without applying any heavy load on the drive circuit. 
     FIG. 15 is an enlarged partial plan view of another liquid crystal panel that can be used for this embodiment. In this panel, each B pixel electrode  1326   b  is arranged right below a corresponding micro-lens  1322  and sided transversally by a pair of G pixel electrodes  1326   g  and longitudinally by a pair of R pixel electrodes  1326   r . With this arrangement, the panel operates exactly same as the above described panel as B light is made to strike it perpendicularly while R/G light is made to enter it slantly (with a same angle of incidence but in different directions) so that the beams of reflected light of the three primary colors come out of the respective RGB pixel electrodes of the corresponding picture unit through a common micro-lens. Alternatively, each R pixel electrode may be arranged right below a corresponding micro-lens  1322  and sided by a pair of G pixel electrodes and a pair of B pixel electrodes. 
     Sixth Embodiment 
     FIG. 16 is an enlarged schematic partial cross sectional view of a sixth embodiment of liquid crystal panel  1320  according to the invention. This embodiment differs from the fifth embodiment in that a piece of sheet glass  1323  is used as opposite glass substrate and the micro-lenses  1220  are formed on the sheet glass  1323  by means of thermoplastic resin and a reflowing technique. Additionally, column spacers  1251  are formed in non-pixel areas by means of photosensitive resin and photolithography. FIG. 17A shows a schematic partial plan view of the liquid crystal panel  1320 . As seen, column spacers  1251  are formed in non-pixel areas at selected corners of the micro-lenses  1220  at a predetermined pitch. FIG. 17B shows a schematic cross sectional view of the embodiment taken along line  17 B— 17 B in FIG.  17 A and across a column spacer  1251 . Column spacers  1251  are preferably arranged at a pitch of every 10 to 100 pixels so as to show a matrix. Care has to be taken so that the number of column spacers can satisfy the two contradictory requirements of the planeness of the sheet glass  1323  and the pourability of liquid crystal. 
     Still additionally, a light shielding layer  1221  of patterned metal film is arranged in this embodiment to prevent stray light from entering through boundary areas of the micro-lenses. This can effectively prevent any degradation of color saturation and contrast due to stray light. Thus, a projection type display apparatus comprising the embodiment of liquid crystal panel can display images of even higher quality particularly in terms of color saturation and contrast. 
     Any of the fourth through sixth embodiments of liquid crystal panel or projection type display apparatus described above can be made to display sharp and well defined images by using an LCD panel unit comprising liquid crystal pixels as described earlier by referring to the first through third embodiments, where a highly uniform surface layer is realized including areas around the chips and both the distance between the holding substrate and the projection lens and the position of the local point are rigidly secured. 
     As described above, according to the invention, an LCD panel is arranged directly on the top of the protuberances of a holding substrate having a uniform height. Thus, the distance between the image displaying plane of the LCD panel and the rear surface of the holding substrate are made even and uniform so that the projected image is held in focus over the entire display screen to make the image very clear and sharp. 
     Additionally, an adhesive agent containing no filler material is applied to the protuberances of the holding substrate to securely bond the LCD panel to the substrate with an improved thermal conductivity. 
     The overall thermal conductivity can be further improved by using an adhesive agent containing a filler material in areas other than the protuberances. Then, the temperature rise during the operation of the LCD panel can be reduced by about 15° C. 
     Meanwhile, a projection type liquid crystal display apparatus according to the invention comprises a reflection type liquid crystal panel provided with micro-lenses and an optical system adapted to emit beams of light of the three primary colors in different respective directions but, once modulated and reflected by the liquid crystal, the beams from each picture unit of RGB pixels of moves through a same micro-lens. Then, the color images displayed by the apparatus are of high quality and free from a mosaic appearance of RGB. 
     Finally, the flux of light from each pixel is collimated as it passes through the micro-lens array twice so that a projection lens that has a small numerical aperture and hence is not expensive can be used to project bright images onto the screen.