Patent Document

BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates generally to a transmissive-type display device (“transmissive display device”). More particularly, the present invention relates to a dot matrix type display device having a display panel and multiple picture elements (“pixels”) arranged in a matrix to form a liquid crystal display (“LCD”), wherein the display panel is provided with an array of microlenses. 
     Description of the Related Art 
     In general, LCDs are comprised of upper and lower substrates facing each other as shown in  FIG. 1 . The lower substrate includes a plurality of pixel electrodes  13  formed on a transparent glass substrate  10 . Data bus lines  12  are formed parallel to each other in a horizontal direction, and gate bus lines  11  are formed parallel to each other in a vertical direction. Between the data bus lines  12  and the gate bus lines  11 , an array of the pixel electrodes  13  are formed. 
     On the transparent substrate  10 , switching elements such as thin film transistors  15  (“TFTs”) are disposed for the respective pixels at each crossing area where the gate bus lines  11  and the data bus lines  12  cross each other. The pixel electrodes  13  are electrically connected to the output electrodes (e.g., drains) of the TFTs  15 . 
     On the other hand, the upper substrate includes a color filter layer  21  formed on a transparent glass substrate  20  and common electrodes  22  formed on the color filter layer  21 . As shown in  FIG. 2 , the color filter layer  21  includes a red color filter  21 R, a green color filter  21 G, and a blue color filter  21 B successively formed on the substrate  20 . Among the different arrangements of color filters, the mosaic-array is employed in an audio video (AV) mode and the striped array is used in an office automation (OA) mode. 
     Once the upper and lower substrates are individually formed, it is necessary to join them for injecting liquid crystal  24  therebetween. The upper substrate and the lower substrate may be joined so that the color filter layer  21  faces the pixel electrodes  13  formed on the transparent glass substrate  10 . 
     Additionally, a black matrix  14  is formed over the gate bus lines  11  and the data bus lines  12  corresponding to the border of the each color filter  21 R,  21 G and  21 B. The black matrix  14  shields light which may have leaked from the gaps formed between the bus lines and the pixel electrodes  13 , and improves the contrast of the LCD by making the borders of the color filters more clear. 
     Generally, the size of the black matrix  14  is larger than that of each bus line because of the misalignment arising from joining the upper substrate with the lower substrate. The gate bus lines  11  and the data bus lines  12  are approximately 15 μm-40 μm and 10 μm-25 μm wide, respectively. Therefore, the black matrix  14  is slightly wider than the bus lines. 
     In the conventional LCDs having the above described elements, a light source is located at the backside of the transparent glass substrate  20 . The black matrix  14  is formed on the transparent glass substrate  10  to cover the gate bus lines  11  and data bus lines  12 . The light from the light source, as depicted with a straight line in  FIG. 2 , is transmitted through the transparent glass substrate  20 , the color filters  21 R,  21 G and  21 B, the common electrodes  22  and the liquid crystal  24 , sequentially. This light passes through the portion of transparent glass substrate  10  having the pixel electrodes  13  thereon. But, the light impinging on the gate and data bus lines  11  and  12  are blocked by the black matrix  14 . As a result, the aperture ratio of the LCD and the brightness of the device is reduced. 
     The aperture ratio is expressed by “the effective area of all the pixels” divided by “the total display area”. The aperture ratio equals the ratio of the recoverable light to all incident light (recoverable and unrecoverable light). (The unrecoverable light is the light blocked by the untransmissive portion of the display panel, and does not contribute to displaying.) As the size of the untransmissive portion increases, the aperture ratio decreases. The reduced aperture ratio leads to reproduction of dark pictures and poor image quality. 
     The LCDs may include a storage capacitor for assisting the cell capacitance of the LCDs. There are two types of storage capacitors. One is a storage-on-common type in which the storage capacitor is formed separately. The other is a storage-on-gate type in which a portion of gate line functions as a storage capacitor electrode. The former has a smaller effective area for forming the pixels than the latter. Therefore, the aperture ratio of such LCDs and the brightness of the display device is reduced. 
     In order to refine pictures on the display, the brightness of the backlight must be increased and the size of the untransmissive portion must be minimized. To increase the brightness of the backlight, more electricity (power) is required; however, such is undesirable because it is costly. 
     Many different methods have been developed to improve the aperture ratio of the LCDs, e.g., enlarging the area of pixel electrodes or enlarging the pixel size. To enlarge the pixel size, however, the other elements of the LCD such as gate bus lines, source bus lines, TFTs and so on, need to be minimized. But, photo-lithography and etching has a limit on minimizing these elements. Further, the width of bus lines cannot be reduced below a certain level. Therefore, it is difficult to manufacture LCDs with an improved aperture ratio. But, even if the pixel size were increased by the above methods, the aperture ratio is generally 40% or 50% at best. 
     To solve the problems described above, an LCD with a different structure has been proposed in which the display panel with an array of microlenses are formed on one side or both sides of the panel. Such a structure is disclosed in Japanese Laid-Open Patent Publications No. 60-262131 and No. 61-11788. Referring to  FIG. 3 , one of the advantages of such known display devices is that the light rays incident onto the portion of display panel which does not contribute to displaying, are focused on the pixel electrodes using elements  31  and pass through elements  32 . As a result, the transmittance of the LCD having the same aperture ratio is increased. 
     Another proposal for further enhancing the above mentioned device is disclosed in U.S. Pat. No. 5,187,599. Referring to  FIG. 4 , such a display device comprises a first array of microlenses  31 ′ disposed on the incident side of the display panel, and a second array of microlenses  32 ′ disposed on the incident side of the other display panel, each microlens being disposed according to the respective pixels. The focal points of the first array of microlenses are identical with those of the second array of microlenses, and the focal length of each microlens in the first array is greater than that of the second array. Therefore, the light rays incident on the untransmissive portion of the display panel is redirected by condensing the diverging rays. 
     The above suggested structure of the LCD are to increase the transmittance of the light and to acquire the effect of having an increased aperture ratio, without actually increasing the aperture ratio. Each microlens covers the entire pixel electrode. The height of the microlenses need to be greater than 50 μm to cover the dimension of each pixel electrode having generally 100 μm×300 μm. However, in practice, it is difficult to form the LCD having microlenses greater than 50 μm in height, resulting relatively flat lenses. Accordingly, the transmittance of conventional LCDs cannot be effectively improved. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an LCD which has an improved transmittance. 
     Another object of the present invention is to provide a brighter LCD with low power consumption. 
     Still another object of the present invention is to provide an LCD which has an improved contrast ratio. 
     Still another object of the present invention is to provide an LCD which overcomes the disadvantages and problems encountered in the conventional LCDs. 
     In order to achieve the above and other objects, an LCD according to the present includes multi-microlenses corresponding to the border of the untransmissive portions of the LCD. More particularly, the LCD according to the embodied invention includes first and second transparent substrates facing each other, a plurality of gate and data bus lines formed on the first substrate, a plurality of color filters formed on the second substrate, and a plurality of microlenses formed corresponding to the gate and data bus lines. In case that storage capacitor lines including storage capacitors are formed on the first substrate for storage capacitance, it is desirable to have a plurality of microlenses at the position corresponding to the storage capacitor lines in order to improve the transmittance. 
     These and other objects of the present application will become more readily apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention and wherein: 
         FIG. 1  is a three-dimensional view showing a structure of a conventional LCD; 
         FIG. 2  is a partial, cross-sectional view showing a light path in the conventional LCD of  FIG. 1 ; 
         FIG. 3  is a cross-sectional view showing a light path in a conventional LCD; 
         FIG. 4  is a cross-sectional view showing a light path in another conventional LCD. 
         FIGS. 5A-5B, 6A-6B, and 7A-7B  are cross-sectional views showing examples of different configurations and shapes of microlenses for an LCD according to the embodiments of the present invention; 
         FIG. 8  is a cross-sectional view of an LCD according to a first example of a first embodiment of the present invention; 
         FIG. 9  is a cross-sectional view of an LCD according to a second example of the first embodiment of the present invention. 
         FIG. 10  is a cross-sectional view of an LCD according to a third example of the first embodiment of the present invention; 
         FIG. 11  is a cross-sectional view of an LCD according to a fourth example of the first embodiment of the present invention; 
         FIG. 12  is a cross-sectional view of an LCD according to a first example of a second embodiment of the present invention. 
         FIG. 13  is a cross-sectional view of an LCD according to a second example of the second embodiment of the present invention; 
         FIG. 14  is a cross-sectional view of an LCD according to a third example of the second embodiment of the present invention; 
         FIG. 15  is a cross-sectional view of an LCD according to a first example of a third embodiment of the present invention; 
         FIG. 16  is a cross-sectional view of an LCD according to a second example of the third embodiment of the present invention; and 
         FIG. 17  is a cross-sectional view of an LCD according to an example of a fourth embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The LCDs according to the preferred embodiments of the present invention will be described with reference to  FIGS. 5 through 17 . The LCD according to the first through fourth embodiments of the present invention includes a plurality of microlenses for effectively redirecting light from a light source all onto the pixel electrodes of the LCD, with simplicity. Generally, a path of light is depicted in the Figures by a line with arrow. 
       FIGS. 8-11  show cross-sectional views of examples of an LCD according to the first embodiment of the present invention. 
     As shown in  FIG. 8 , the first example of the LCD according to the first embodiment of the present invention includes a plurality of microlenses  131  formed on a color filter layer  121  containing color filters  121 R,  121 G and  121 B. The color filter layer  121  is formed on a second transparent glass substrate  120 . The microlenses  131  are covered with an overcoat material, such as acrylic resin to form an overcoat layer  132 . Common electrodes  122  are formed on the overcoat layer  132  and constitute a transparent conductive layer made of ITO. Pixel electrodes  113  are formed on a first transparent glass substrate  110 , and a black matrix  114  is formed to cover gaps between the pixel electrodes  113  and data bus lines  112  and gaps between the pixel electrodes  113  and gate bus lines. 
     As shown in  FIG. 9 , the second example of the LCD according to the first embodiment of the present invention includes a plurality of microlenses  231  formed directly on a second glass substrate  220  and covered with an overcoat layer  232  made of acrylic resin. A color filter layer  221  having red, blue, and green filters  221 R,  221 B,  221 G is then formed on the overcoat layer  232 . On the color filter layer  221 , common electrodes  222  are formed. Other elements, such as the data bus lines  112 , pixel electrodes  113 , black matrix  114  and gate bus lines are formed on the first substrate  110  in a manner similar to the LCD of  FIG. 8 . 
     As shown in  FIG. 10 , the third example of the LCD according to the first embodiment of the present invention includes a plurality of microlenses  331  formed on the outer surface of a second transparent glass substrate  320 . The microlenses  331  are covered with an overcoat layer  332  made of acrylic resin. On the inner surface of the second substrate  320 , a color filter layer  321  having red, blue, and green filters  321 R,  321 B,  321 G is formed. Then on the color filter layer  321 , common electrodes  322  are formed. Other elements, such as the data bus lines  112 , pixel electrodes  113 , black matrix  114  and gate bus lines are formed on the first substrate  110 , in a manner similar to the LCDs of  FIGS. 8 and 9 . 
     As shown in  FIG. 11 , the fourth example of the LCD according to the first embodiment of the present invention includes a plurality of microlenses  431  formed by selectively etching the outer surface portion of an overcoat layer  432  formed on a second transparent glass substrate  420 . The spaces formed by etching the overcoat layer  432  are filled with a material different from the material constituting the overcoat layer  432  in refraction index. For example, the overcoat layer  432  may be formed of acrylic resin and the microlenses  431  may be formed of an organic material, such as benzocyclobutene (“BCB”). Similarly the overcoat layer  432  may be formed of BCB and the microlenses  431  may be formed of acrylic resin. 
     On the inner surface of the second substrate  420 , a color filter layer  421  having red, blue and green filters  421 R,  421 B,  421 G is formed. Then on the color filter layer  421 , common electrodes  422  are formed. Other elements, such as the data bus lines  112 , pixel electrodes  113 , black matrix  114  and gate bus lines are formed on the first substrate  110 , in a manner similar to the LCDs of  FIGS. 8, 9 and 10 . 
     The microlenses  131 ,  231 ,  331  and  431  are preferred to be about 6 μm in width and about 3 μm in height, in view of the distance between the color filter layer and data bus lines  112  (or gate bus lines), and in view of the width of each bus line and the refraction index of the microlenses. 
     According to the first embodiment, the light from the backlight, which is shielded by the bus lines in the conventional LCDs, is refracted when arriving at the surface of each microlens  131 ,  231 ,  331  and  431 , and passes through the pixel electrodes  113  and first transparent glass substrate  110 . As a result, almost all incident light can be transmitted, increasing the transmittance substantially. 
     In these cases, a micro black matrix whose width is narrower than that of bus lines can be additionally disposed between the color filters on the second transparent substrate, in order to further emphasize the color difference with clear boundaries. 
     Furthermore, according to the first embodiment of the present invention, the microlenses  131 ,  231 ,  331 , and  431  are formed on the second substrate corresponding to the edge portions of the pixel electrodes and to cover the bus lines and the gaps between the bus lines and pixel electrodes. The middle portions of the pixel electrodes  113  may not be covered by the microlenses. 
       FIGS. 12-14  show cross-sectional views of examples of an LCD according to the second embodiment of the present invention. In the second embodiment, microlenses are disposed on the lower substrate and the backlight is disposed behind the lower substrate. 
     As shown in  FIG. 12 , the first example of the LCD according to the second embodiment of the present invention includes a plurality of microlenses  155  formed on the inner surface of a first transparent glass substrate  150 . The microlenses  155  are covered with an overcoat layer  156  made of acrylic resin. On the overcoat layer  156 , other elements, such as the data bus lines  152 , pixel electrodes  153 , a black matrix  154  and gate bus lines are formed. 
     In the upper substrate, a color filter layer  121 ′ having red, blue and green filters  121 R′,  121 B′ and  121 G′ is formed on a second transparent glass substrate  120 ′. On the color filter layer  121 ′, common electrodes  122 ′ are formed. 
     Further, the backlight is disposed behind the first transparent substrate  150  and directs the light toward the second transparent substrate  120 ′. The incident light is focused by the microlenses  155  so that it is directed to the pixel electrodes  153  and not to the data and gate bus lines. As a result, the microlenses  155  redirect light which would have been blocked and scattered by the bus lines onto the edge portions of the pixel electrodes  153 . Accordingly, the transmittance is increased and the LCD with an increased brightness and increased power efficiency is produced. 
     As shown in  FIG. 13 , the second example of the LCD according to the second embodiment of the present invention includes a plurality of microlenses  165  formed on the outer surface of a first transparent glass substrate  160 . These microlenses  165  are covered with an overcoat layer  166  made of benzocyclobutene or acrylic resin. On the inner surface of the first transparent substrate  160 , other elements, such as data bus lines  162 , pixel electrodes  163 , a black matrix  164  and gate bus lines are formed. 
     In the upper substrate, common electrodes  122 ′, a color filter layer  121 ′ having color filters  121 R′,  121 B′,  121 G′, and a second transparent glass substrate  120 ′ are formed in a manner similar to the upper substrate of the LCD in  FIG. 12 . 
     As shown in  FIG. 14 , the third example of the LCD according to the second embodiment of the present invention includes a plurality of microlenses  175  formed by selectively etching the outer surface portion of an overcoat layer  176  formed on a first transparent glass substrate  170 . The spaces formed by etching the overcoat layer  176  may be filled with a material such as acrylic resin or BCB. For example, if the overcoat layer  176  is made of acrylic resin, the spaces may be filled with BCB. If the overcoat layer  176  is made of BCB, the spaces may be filled with acrylic resin. On the inner surface of the first transparent substrate  170 , other elements, such as data bus lines  172 , pixel electrodes  173 , a black matrix  174  and gate bus lines are formed. 
     In the upper substrate, common electrodes  122 ′, a color filter layer  121 ′ having color filters  121 R′,  121 B′,  121 G′, and a second transparent glass substrate  120 ′ are formed in a manner similar to the LCDs of  FIGS. 12 and 13 . 
     According to the second embodiment of the present invention, the light source is positioned at the backside of the first transparent glass substrate  150 ,  160  and  170 . When the light from the light source hits the surface of the microlenses  155 ,  165  and  175 , it is refracted. That is, the light which is blocked by the gate and data bus lines in the conventional LCDs is refracted as it passes through the microlenses. The refracted light then passes through the pixel electrodes  153 ,  163  and  173  and the second transparent substrate  120 ′. As a result, almost all incident light can be transmitted and the transmittance is consequently increased. 
     In these cases, a micro black matrix whose width is less than that of the bus lines can be additionally disposed between the color filters on the second transparent substrate, to emphasize the different colors. 
       FIGS. 15 and 16  show cross-sectional views of examples of an LCD according to the third embodiment of the present invention. 
     As shown in  FIG. 15 , the first example of the LCD according to the third embodiment of the present invention includes a plurality of microlenses  531  formed by selectively etching the outer surface portion of a second transparent glass substrate  520 . The spaces formed by etching the second substrate  520  may be filled with a material  532 , such as acrylic resin. 
     On the inner surface of the second transparent substrate  520 , a color filter layer  521  having red, blue and green filters  521 R,  521 B and  521 G is formed. Between these color filters, a black matrix  514  having a width larger than the width of each bus line is formed, in accordance with the joining margin of the second transparent substrate  520  and a first transparent glass substrates  510 . On the color filter layer  521 , common electrodes  522  are formed. 
     In the lower substrate, data bus lines  512 , pixel electrodes  513 , and gate bus lines are formed on the first transparent glass substrate  510 . 
     Here, a backlight is located behind the second substrate  520 . The light which would have been blocked by the black matrix  514  is redirected onto the color filter layer  521  and passes through the pixel electrodes  513 . 
     As shown in  FIG. 16 , the second example of the LCD according to the third embodiment of the present invention includes a plurality of microlenses  631  formed in the lower substrate. By selectively etching the outer surface portion of the first transparent glass substrate  610 , the microlenses  631  are shaped. The spaces formed by etching the first substrate  610  may be filled with a material  632 , such as an acrylic resin. 
     On the inner surface of the first transparent substrate  610 , data bus lines  612 , pixel electrodes  613 , and gate bus lines are formed. In the upper substrate, a color filter layer  621  having red, blue and green filters  621 R,  621 B and  621 G is formed on a second transparent glass substrate  620 . Between these color filters, a black matrix  614  having a width larger than the width of each bus line is formed, in accordance with the joining margin of the first and second transparent substrates  610  and  620 . On the color filter layer  621 , common electrodes  622  are formed. 
     Here, the backlight is located behind the first substrate  610 . The light which would have been blocked by the black matrix  614  is redirected onto the color filter layer  621  and passes through the pixel electrodes  613 . 
     Therefore, according to the third embodiment of the present invention, the transmittance and aperture ratio of the LCD is increased with increased power efficiency. 
       FIG. 17  shows a cross-sectional view of an LCD according to the fourth embodiment of the present invention. 
     The LCDs according to the first and second embodiments comprise a BM (black matrix) formed on arrays of TFTs formed on a first substrate. The transmittance can be increased by enlarging the size of pixel electrodes, avoiding the BM-on-array structure. The LCD according to the fourth embodiment of the present invention is formed with enlarged pixel electrodes, which includes pixel electrodes formed on a passivation layer made of benzocyclobutene. 
     The LCD according to the fourth embodiment further includes microlenses formed at each pixel border area of the color filter layer corresponding to the gate bus lines and the data bus lines. The microlenses  731  are covered with an overcoat layer  732  made of an organic film such as BCB or acrylic resin. The overcoat layer is formed to enhance stability in rubbing and to improve leveling. The overcoat layer may not be necessary if stability in rubbing and improvement in leveling are already obtained. 
     This embodiment provides pixel electrodes  713  larger than those of an LCD comprising a typical BM-on-array structure. 
     As shown in  FIG. 17 , the LCD includes a plurality of microlenses  731  formed on the inner surface of a color filter layer  721 . The color filter layer having red, green and blue filters  721 R,  721 G and  721 B is formed on the inner surface of a second transparent glass substrate  720 . On the microlenses  731 , an overcoat layer  732  made of benzocyclobutene is formed, and common electrodes  722  are formed thereon. 
     In the lower substrate, a passivation layer  715  made of an organic material, such as benzocyclobutene is formed between data bus lines  712  and pixel electrodes  713 , so that larger pixel electrodes can be formed. A black matrix is formed only on the gate bus lines formed on a first transparent glass substrate  710 . 
     In the fourth embodiment of the present invention, a light from the backlight travels straight through the second substrate  720  and is refracted at the surface of the microlenses  731 . The refracted light impinges on the pixel electrodes  713 , but not on the gate and data bus lines. Consequently, most of the light from the light source is transmitted through the first transparent glass substrate  710 . 
     According to the first through fourth embodiments of the present invention, when the microlenses ( 131 ,  155 ,  165 ,  175 ,  231 ,  331 ,  431 ,  531 ,  631  and  731 ) are formed at the positions corresponding to the gate and source bus lines, almost no incident light is lost. Consequently, the aperture ratio is improved up to 90%, compared to at most 70% in the conventional LCDs. Therefore, an LCD which is driven by a low power and has a high transmittance is obtained. 
     With respect to forming the microlenses, a discussion on how large the scale of microlenses is and where the microlenses are formed is provided below. 
     In order to design the microlenses for condensing or dispersing the incident light, the relationship between the incident angle and the refracted angle of the light is considered. The refraction angle of the light is calculated from the following equation (1) known as the Snell&#39;s law, which shows the relationship between refraction indices and refraction angles.
 
 n   2   /n   1 =sin θ 1 /sin θ 2   (1)
 
     According to the equation (1), the refraction angle θ 2  of incident light at an angle θ 1  to the normal line of each microlens is determined by the refraction index of the material (n 1 ) of the microlens and the refraction index of the material (n 2 ) being in contact with the microlens. 
     In the present invention, considering the effects of the microlenses and easiness of making them, microlenses having the width of 4 μm-30 μm and the height of greater than 0.5 μm are suggested. 
     The microlenses according to the embodiments of the present invention are formed at the positions according to the gate bus lines and the data bus lines so as to obtain the best effect. In a case where the light source is positioned at the backside of the second substrate having a color filter layer, it is desirable to form the microlenses on the outer or inner side of the second substrate. In a case where the light source is positioned at the backside of the first substrate having pixel electrodes, it is desirable to form the microlenses on the outer or inner side of the first substrate. However, the position of the microlenses is not restricted to the above. That is, as long as the microlenses function to focus and redirect the light which travels to the gate bus lines and the data bus lines, the shape of microlenses can be varied. 
       FIGS. 5A-7B  are cross-sectional and plan views showing examples of different configurations and shapes of microlenses for the LCDs according to the present invention. These examples are applicable to the first through fourth embodiments of the present invention. Each of the microlenses of the present invention can be formed to be equal to or greater (e.g., more than 30 μm) than each line width at the positions corresponding to the gate data lines and data bus lines. 
     As shown in  FIGS. 5A and 5B , the microlens ( 141 ) cover each data bus line  142  and each gate bus line  144 . The microlenses  141  are positioned so that the border therebetween is substantially aligned with the center of each bus line (shown by the dotted line). Also, a width of the gate bus line  144  or the data bus line  142  extends substantially between centers of the micro lenses ( 141 ). Two microlenses ( 141 ) are disposed over the gate bus lines ( 144 ) in a width direction of each gate bus line ( 144 ), and two microlenses ( 141 ) are disposed over the data bus lines ( 142 ) in a width direction of each data bus line ( 142 ). The two microlenses  141  are positioned so that the border therebetween is substantially aligned with the center of each bus line (shown by the dotted line). As further shown by  FIG. 5B , at least three microlenses are disposed over each of the gate and data bus lines corresponding to one pixel in a length direction. In  FIGS. 6A and 6B , moreover, the microlenses ( 145 ) can also be formed at any position in the LCD panel, including where the pixel electrodes  143  are. 
     As shown in  FIGS. 7A and 7B , the microlens ( 146 ) having the same size as the color filter layer can be formed at a position corresponding to each color filter layer, covering the corresponding array of pixel electrodes  143 . The microlens  146  includes edge portions which are curved and which cover the area in which the color filter layer overlaps the gate bus lines  141  and data bus lines  142 . These edge portions correspond to a light shielding area (non-transmissive portion), such as gate and data bus lines, a black matrix, and storage capacitor lines. The shape of the edge portions allows the incident light to be focused onto the transmissive portion. The microlens  146  further includes a substantially flat portion for allowing the light to pass straight through the pixel electrodes  143 . 
     The microlenses according to the first through fourth embodiments of the present invention can be made of a different material or can be formed by patterning LCD elements such as a color filters, pixel electrodes, insulating layers, a transparent glass substrate, etc. into the shape of a lens. As described above, an overcoat layer is formed on the microlenses for increased stability in rubbing and upgrading the uniformity of the substrate surface. 
     According to the present invention, although the amount of an incident light is not increased, the amount of the transmitted light is increased. In other words, though the aperture ratio, namely the size of transmissive portion, is not increased, the same effect of having an increased aperture ratio is achieved. 
     The effect of the present invention is increased when it is applied to the LCD structures, in which the pixel electrodes overlap the data bus lines and an organic insulator such as BCB is inserted between the pixel electrodes and the bus lines, for increasing the size of the pixels. The effect is also increased by forming a black matrix (BM-on-array) on the first transparent glass substrate. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.

Technology Category: 3