Abstract:
The invention relates to a substrate for a transflective liquid crystal display that is used as a display of a portable electronic apparatus and that is capable of display in both of reflective and transmissive modes and relates to a liquid crystal display having the same. The invention is aimed at achieving high display characteristics at a low cost. A configuration is employed which includes a substrate that sandwiches a liquid crystal in combination with an opposite substrate formed with a common electrode on the opposing surface, a plurality of bus lines formed on a top surface of the substrate such that they intersect with each other with an insulation film interposed therebetween, thin film transistors formed in the vicinity of positions where the plurality of bus lines intersect with each other; and the plurality of pixel regions constituted of a plurality of reflective regions in which reflective electrodes for reflecting incident light from the side of the top surface of the substrate are formed in the form of a matrix and transmissive regions which are provided around the plurality of reflective regions and which transmit incident light from the side of a bottom surface of the substrate toward the top surface of the substrate.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a substrate for a transflective liquid crystal display that is used as a display of a portable electronic apparatus and that is capable of display in both of reflective and transmissive modes and to a liquid crystal display having the same.  
           [0003]    2. Description of the Related Art  
           [0004]    Liquid crystal displays are generally categorized into transmissive types in which a transparent electrode constituted of an ITO (indium tin oxide) is formed at each pixel and which have a backlight unit on a backside thereof and reflective types in which a reflective electrode made of aluminum (Al) is formed at each pixel. Among recent active matrix liquid crystal displays, reflective liquid crystal displays are drawing attention for their lighter weights, low profiles, and low power consumption. Single polarizer type reflective liquid crystal displays utilizing the TN (Twisted Nematic) mode as disclosed in Japanese Patent Laid-open No. 232465/1993 and Japanese Patent Laid-Open No. 338993/1996 have already been put in use. However, the visibility of a reflective liquid crystal display is greatly dependent on the brightness of the ambience, and a problem arises in that visibility is significantly reduced in a dark place where ambient brightness is relatively low.  
           [0005]    A transmissive liquid crystal display exhibits a high contrast ratio and high visibility even in a dark place because it is illuminated from the backside thereof with a backlight unit. However, it has a problem in that visibility is significantly reduced in a place where ambient brightness is relatively high such as the outdoor in good weather (a bright place). Further, since a backlight unit is always used, another problem arises in that power consumption is great.  
           [0006]    Liquid crystal displays that solve the above-described problems include front light type reflective liquid-crystal displays having a front light unit that provides illumination from the side of the display screen thereof. However, a front light type reflective liquid crystal display exhibits a contrast ratio lower than that of a transmissive liquid crystal display in a dark place because illumination light from the front light unit is reflected by not only the reflective electrodes but also the surface of the display screen. In a bright place, it presents darker display in a bright place compared to a normal reflective liquid crystal display because of light absorption at a light guide plate of the front light unit.  
           [0007]    Another approach involves a transflective liquid crystal display in which transflective reflecting films are used as pixel electrodes as disclosed in Japanese Patent Laid-Open No. 333598/1995. In general, metal thin films such as aluminum having a thickness of about 30 nm are used as the transflective reflecting films. However, this results in a reduction in utilization of light because the metal thin films have a high absorption constant. Further, since it is difficult to form transflective reflecting films having a uniform thickness in the plane of a substrate, there will be variations of light transmittance and reflectance in the plane of the substrate.  
           [0008]    A transflective liquid crystal display that solves the above-described problems was disclosed in Japanese Patent Laid-Open No. 281972/1999. FIG. 29 shows a configuration of a transflective liquid crystal display according to the related art. As shown in FIG. 29, a plurality of gate bus lines  104  extending in the vertical direction in the figure are formed in parallel with each other on a TFT substrate  102 . A plurality of drain bus lines  106  extending in the horizontal direction in the figure are formed in parallel with each other such that they intersect with the gate bus lines  104  with an insulation film which is not shown interposed therebetween. TFTs  108  are formed in the vicinity of the positions where the bus lines  104  and  106  intersect with each other. Drain electrodes  140  of the TFTs  108  are electrically connected to the drain bus lines  106 . Source electrodes  142  are electrically connected to reflective electrodes  110  made of aluminum through contact holes  144 . The regions where the reflective electrodes  110  are formed serve as reflective regions of respective pixels. Openings are provided in the middle of the reflective electrodes  110  to form transparent electrodes  112  made of ITO. The regions where the transparent electrodes  112  are formed serve as transmissive regions of respective pixels.  
           [0009]    [0009]FIG. 30 is a sectional view of the liquid crystal display taken along the line X-X in FIG. 29. As shown in FIG. 30, the liquid crystal display is constituted of the TFT substrate  102 , an opposite substrate  114 , and a liquid crystal layer  116  provided between the substrates  102  and  114 . The TFT substrate  102  has a planarization film  120  in reflective regions on a glass substrate  118 . A plurality of recesses and projections are formed on a surface of the planarization film  120 . Reflective electrodes  110  are formed on the planarization film  120 . On a surface of the reflective electrodes  110 , there are formed recesses and projections which are associated with the recesses and projections formed on the surface of the planarization film  120  located under the same. The reflective electrodes  110  have improved light scattering characteristics thanks to the plurality of recesses and projections on the surface thereof, and they reflect and scatter external light incident thereupon in various directions.  
           [0010]    Transparent electrodes  112  are formed in transmissive regions on the glass substrate  118 . The transparent electrodes  112  transmit light emitted by a backlight unit (not shown) provided under the same in the figure. The transparent electrodes  112  are electrically connected to the reflective electrodes  110  through barrier metal layers  136  made of titanium (Ti) or molybdenum (Mo).  
           [0011]    The counter substrate  114  has a common electrode  130  that extends throughout a top surface of the glass substrate  119 . Polarizers  132  and  134  are applied to surfaces of the substrates  102  and  114  counter to surfaces thereof facing each other, respectively.  
           [0012]    The liquid crystal display shown in FIGS. 29 and 30 achieves display in both of the reflective and transmissive modes by forming a reflective region and a transmissive region at each pixel.  
           [0013]    In the above-described configuration, however, it is necessary to form both of the reflective electrodes  110  made of Al and the transparent electrodes  112  made of ITO. Further, since corrosion attributable to a battery effect occurs when Al and ITO are formed in contact with each other, the barrier metal layers  136  must be formed between the reflective electrodes  110  and the transparent electrodes  112 . This has resulted in a problem in that the liquid crystal display involves complicated manufacturing steps and in that an increase in manufacturing cost occurs.  
           [0014]    In the above-described configuration, a reflective region and a transmissive region are formed at each pixel. Therefore, the display exhibits reflection characteristics lower than those of a reflective liquid crystal display and transmission characteristics lower than those of a transmissive liquid crystal display. However, when the area of the reflective regions is increased to achieve improved reflection characteristics, the area of the transmissive regions further decreases to degrade the transmission characteristics further. Similarly, when the area of the transmissive regions is increased to achieve improved transmission characteristics, the area of the reflective regions decreases to degrade the reflection characteristics further. Thus, in a transflective liquid crystal display in the related art, reflection characteristics and transmission characteristics are in the relationship of tradeoff, and a problem has arisen in that it is difficult to improve both of the reflection characteristics and the transmission characteristics.  
           [0015]    Further, while light incident upon the reflective regions pass through a color filter (CF) layer twice, the light passes through the CF layer only once in the transmissive regions. This results in a chromatic deviation between display in the reflective mode and display in the transmissive mode. While a chromatic deviation can be optically compensated to some degree, it can degrade display characteristics.  
         SUMMARY OF THE INVENTION  
         [0016]    The invention provides a substrate for a liquid crystal display that provides high display characteristics at a low cost and a liquid crystal display having the same.  
           [0017]    According to the invention, there is provided a substrate for a liquid crystal display, characterized in that it has a substrate that sandwiches a liquid crystal in combination with an opposite substrate provided opposite thereto, a plurality of bus lines formed on a top surface of the substrate such that they intersect with each other with an insulation film interposed therebetween, thin film transistors formed in the vicinity of positions where the plurality of bus lines intersect with each other, and a pixel region constituted of a plurality of reflective regions in which reflective electrodes for reflecting incident light from the side of the top surface of the substrate are formed in the form of a matrix and transmissive regions which are provided around the plurality of reflective regions and which transmit incident light from the side of a bottom surface of the substrate toward the top surface of the substrate. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    [0018]FIG. 1 is a diagram showing a liquid crystal display according to a first basic configuration in a first mode for carrying out the invention;  
         [0019]    [0019]FIG. 2 is a diagram showing the liquid crystal display according to the first basic configuration in the first mode for carrying out the invention;  
         [0020]    [0020]FIG. 3 is a diagram showing a liquid crystal display according to a second basic configuration in the first mode for carrying out the invention;  
         [0021]    [0021]FIG. 4 is a diagram showing a liquid crystal display having a combination of the first and second basic configurations in the first mode for carrying out the invention;  
         [0022]    [0022]FIGS. 5A and 5B show microphotographs of states of display of predetermined images on the liquid crystal display according to a first embodiment in the first mode for carrying out the invention.  
         [0023]    [0023]FIGS. 6A and 6B show states of display of predetermined images on the liquid crystal display according to the first embodiment in the first mode for carrying out the invention;  
         [0024]    [0024]FIGS. 7A and 7B schematically show a sectional configuration of a liquid crystal display according to a second embodiment in the first mode for carrying out the invention;  
         [0025]    [0025]FIG. 8 shows an arrangement of optical axes of the liquid crystal display according to the second embodiment in the first mode for carrying out the invention;  
         [0026]    [0026]FIGS. 9A and 9B schematically show a sectional configuration of the liquid crystal display according to the second embodiment in the first mode for carrying out the invention;  
         [0027]    [0027]FIGS. 10A to  10 D show states of display of the liquid crystal display in a reflective mode according to the second embodiment in the first mode for carrying out the invention;  
         [0028]    [0028]FIGS. 11A to  11 D show states of display of the liquid crystal display in a transmissive mode according to the second embodiment in the first mode for carrying out the invention;  
         [0029]    [0029]FIG. 12 shows an arrangement of optical axes of a liquid crystal display according to a third embodiment in the first mode for carrying out the invention;  
         [0030]    [0030]FIGS. 13A to  13 D show states of display of the liquid crystal display in the reflective mode according to the third embodiment in the first mode for carrying out the invention;  
         [0031]    [0031]FIGS. 14A to  14 D show states of display of the liquid crystal display in the transmissive mode according to the third embodiment in the first mode for carrying out the invention;  
         [0032]    [0032]FIG. 15 shows an arrangement of optical axes of a liquid crystal display according to a fourth embodiment in the first mode for carrying out the invention;  
         [0033]    [0033]FIGS. 16A to  16 D show states of display of the liquid crystal display in the reflective mode according to the fourth embodiment in the first mode for carrying out the invention;  
         [0034]    [0034]FIGS. 17A to  17 D show states of display of the liquid crystal display in the transmissive mode according to the fourth embodiment in the first mode for carrying out the invention;  
         [0035]    [0035]FIG. 18 shows an arrangement of optical axes of a liquid crystal display according to a fifth embodiment in the first mode for carrying out the invention;  
         [0036]    [0036]FIGS. 19A to  19 D show states of display of the liquid crystal display in the reflective mode according to the fifth embodiment in the first mode for carrying out the invention;  
         [0037]    [0037]FIGS. 20A to  20 D show states of display of the liquid crystal display in the transmissive mode according to the fifth embodiment in the first mode for carrying out the invention;  
         [0038]    [0038]FIG. 21 shows a configuration of a liquid crystal display according to a sixth embodiment in the first mode for carrying out the invention;  
         [0039]    [0039]FIGS. 22A and 22B show a configuration of a substrate for a liquid crystal display according to a seventh embodiment in the first mode for carrying out the invention;  
         [0040]    [0040]FIG. 23 is a graph showing a relationship between reflectivity and average inclinations that is a prerequisite for the seventh embodiment in the first mode for carrying out the invention;  
         [0041]    [0041]FIG. 24 shows a configuration of a liquid crystal display according to an eighth embodiment in the first mode for carrying out the invention;  
         [0042]    [0042]FIG. 25 shows a modification of the configuration of the liquid crystal display according to the eighth embodiment in the first mode for carrying out the invention;  
         [0043]    [0043]FIG. 26 shows another modification of the configuration of the liquid crystal display according to the eighth embodiment in the first mode for carrying out the invention;  
         [0044]    [0044]FIG. 27 shows a configuration of a liquid crystal display in a second mode for carrying out the invention;  
         [0045]    [0045]FIG. 28 shows a modification of the configuration of the liquid crystal display in the first mode for carrying out the invention;  
         [0046]    [0046]FIG. 29 shows a configuration of a transflective liquid crystal display according to the related art; and  
         [0047]    [0047]FIG. 30 is a sectional view showing the configuration of the transflective liquid crystal display according to the related art. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0048]    First Mode for Carrying Out the Invention  
         [0049]    A description will now be made with reference to FIGS.  1  to  26  on a substrate for a liquid crystal display and a liquid crystal display having the same in a first mode for carrying out the invention. First, a description will be made with reference to FIGS. 1 and 2 on a first basic configuration according to the invention that is a prerequisite of the present embodiment. FIG. 1 shows a liquid crystal display having the first basic configuration. As shown in FIG. 1, a plurality of gate bus lines  10  (FIG. 1 shows only one of them) extending in the vertical direction in the figure are formed in parallel with each other on a TFT substrate (base substrate)  2 . A plurality of drain bus lines  12  extending in the horizontal direction in the figure are formed in parallel with each other such that they intersect with the gate bus lines  10  with an insulation film that is not shown interposed therebetween. TFTs  14  are formed in the vicinity of the intersections between the bus lines  10  and  12 . Drain electrodes  16  of the TFTs  14  are extracted from the drain bus lines  12  and are formed such that their ends are located on edges of active semiconductor layers formed of amorphous silicon (a-Si) on the gate bus lines  10  and channel protection films formed on the same on one side thereof (the layers and films are both omitted in the figure).  
         [0050]    Source electrodes  18  of the TFTs  14  are formed such that they are located on other edges of the active semiconductor layers and channel protection films on another other side thereof. In such a configuration, the gate bus lines  10  located directly under the channel protection films serve as gate electrodes of the TFTs  14 . Reflective electrodes  20  are formed above the intersections between the bus lines  10  and  12  and the TFTs  14 . The source electrodes  18  of the TFTs  14  are electrically connected to the reflective electrodes  20  through contact holes  22 .  
         [0051]    [0051]FIG. 2 shows a section of the liquid crystal display taken along the line A-A in FIG. 1. The liquid crystal display has a TFT substrate  2 , a counter substrate  4 , and a liquid crystal layer  24  located between the substrates  2  and  4 . The TFT substrate  2  and the counter substrate  4  are provided opposite to each other with a cell gap dl interposed therebetween. For example, the TFT substrate  2  has a planarization film  28  having a thickness substantially equal to the cell gap dl on a glass substrate  26 . A plurality of recesses and projections are formed on a surface of the planarization film  28 . Reflective electrodes  20  and  20 ′ made of Al are formed at each pixel on the planarization film  28 . On a surface of the reflective electrodes  20  and  20 ′, there are formed recesses and projections which are associated with the recesses and projections formed on the surface of the planarization film  28  located under the same. The reflective electrodes  20  and  20 ′ have improved light scattering characteristics thanks to the plurality of recesses and projections formed on the surface of the same, and external light incident upon the reflective electrodes  20  and  20 ′ is scattered and reflected in various directions. The reflective electrodes  20  and  20 ′ are provided at an interval w+w′.  
         [0052]    The opposite electrode  4  has a common electrode  30  constituted of an ITO that covers a surface of a glass substrate  27  entirely. Predetermined polarizers  32  and  34  are applied to surfaces of the substrates  2  and  4  opposite to surfaces thereof facing each other, respectively. A backlight unit (not shown) is provided under the TFT substrate  2  in the figure.  
         [0053]    The regions where the reflective electrodes  20  are formed constitute reflective regions R that reflect external light incident thereupon. Similarly, the regions where the reflective electrodes  20 ′ are formed constitute reflective regions R′. Regions where the reflective electrodes  20  and  20 ′ are not formed constitute transmissive regions T and T′ that transmit light emitted by the backlight unit. The transparent electrodes Tare located within ranges where they are at a distance w (≅d 1 ) or closer to edges of the reflective electrodes  20 , and the transparent electrodes T′ are located within ranges where they are at a distance w′ (≅d 1 ) or closer to edges of the reflective electrodes  20 ′. That is, a reflective region R constitutes one pixel in combination with a transmissive region T provided in the neighborhood of the same. A reflective region R′ constitutes one pixel in combination with a transmissive region T′ provided in the neighborhood of the same. No transparent electrode  112  as shown in FIG. 30 is formed in the transmissive regions T and T′.  
         [0054]    [0054]FIG. 2 shows a state of a reflective electrode  20  in which a predetermined grayscale voltage is applied thereto. The broken lines in the figure indicate an electric field between the reflective electrode  20  and the common electrode  30 . In the transmissive region T, an oblique field is generated between the common electrode  30  and an edge of the reflective electrode  20  at an angle to a direction perpendicular to the substrate surface. Liquid crystal molecules in the transmissive region T are driven by the oblique field substantially similarly to liquid crystal molecules in the reflective region R. In the transmissive region T′ an oblique field is generated between the common electrode  30  and an edge of the reflective electrode  20 ′. Liquid crystal molecules in the transmissive region T′ are driven by the oblique field substantially similarly to liquid crystal molecules in the reflective region R′.  
         [0055]    The planarization film  28  is removed in the transmissive regions T and T′. A cell gap d 2  between the transmissive regions T and T′ is substantially twice the cell gap d 1  between the reflective regions R and R′, because the thickness of the planarization film  28  is substantially similar to the cell gap d 1 . Therefore, retardation (Δn·d) that occurs in the liquid crystal layer  24  when liquid crystal molecules are aligned in parallel with the substrate surface is λ/4 in the reflective regions R and R′, and it is doubled or λ/2 in the transmissive regions T and T′.  
         [0056]    In the first basic configuration of the invention, the reflective electrodes  20  are provided at the intersections between the bus lines  10  and  12  and on the TFTs  14  to reduce the area of the bus lines  10  and  12  exposed in the transmissive regions T and T′ significantly, which increases the area of the transmissive regions T and T′ without decreasing the area of the reflective regions R and R′. That is, in the first basic configuration, bus line wiring regions that have not been used as reflective regions nor as transmissive regions in a transflective liquid crystal display in the related art are used as the transmissive regions T and T′. Therefore, transmission characteristics can be improved without degrading reflection characteristics to improve utilization of light. Further, no transparent electrode  112  is formed in the transmissive regions T and T′ in the first basic configuration. Therefore, steps for forming transparent electrodes  112  and forming barrier metal layers  136  can be omitted to reduce the manufacturing cost.  
         [0057]    A second basic configuration of the invention will now be described with reference to FIG. 3. FIG. 3 shows a liquid crystal display having the second basic configuration. Components having functions and effects like those in the liquid crystal display having the first basic configuration shown in FIG. 1 are indicated by like reference numerals and will not be described. As shown in FIG. 3, reflective electrodes  20   a  to  20   e  constituting reflective regions R are formed in regions defined by gate bus lines  10  and drain bus lines  12 . The reflective electrodes  20   a  to  20   e  have openings  36   a  to  36   e  that are formed in various configurations such as slits and circular and polygonal holes.  
         [0058]    For example, the reflective electrode  20   a  is formed with an opening  36   a  which is constituted of one slit extending in parallel with longer sides of the reflective electrode  20   a  and a plurality of slits extending at an angle to the longer sides of the reflective electrodes  20   a . The reflective electrode  20   b  is formed with a plurality of straight openings  36   b  extending in parallel with shorter sides of the reflective electrode  20   b . The reflective electrode  20   c  is formed with a plurality of elongate rhombic openings  36   c  extending in parallel with shorter sides of the reflective electrode  20   c . The reflective electrode  20   d  is formed with a plurality of circular openings  36   d . The reflective electrode  20   e  is formed with a plurality of wedge-shaped openings  36   e  extending in parallel with longer sides of the reflective electrode  20   e.    
         [0059]    The regions where the openings  36   a  to  36   e  are formed serve as transmissive regions T. No transparent electrode  112  as shown in FIG. 30 is formed at the openings  36   a  to  36   e . Liquid crystal molecules in the transmissive regions T are driven by an oblique field between edges of the reflective electrodes  20   a  to  20   e  and a common electrode  30  (not shown in FIG. 3) substantially similarly to liquid crystal molecules in reflective regions R.  
         [0060]    The openings  36   a  to  36   e  in each pixel may have the same configuration. The openings  36   a  to  36   e  may have a configuration to regulate alignment of liquid crystal molecules. As a result, in a VA (Vertical Aligned) mode liquid crystal display in which liquid crystal molecules are aligned substantially perpendicularly to the substrate surface, separate alignments can be achieved without a process of rubbing the alignment film. The present basic configuration may be used in a liquid crystal display in the TN mode utilizing a horizontal alignment film or the HAN (Hybrid Aligned Nematic) mode utilizing a horizontal alignment film in one direction and a vertical alignment film in another, although a rubbing process is required.  
         [0061]    In the second basic configuration of the invention, since no transparent electrode  112  is formed in the transmissive regions T, steps for forming transparent electrodes  112  and barrier metal layers  136  can be omitted to reduce the manufacturing cost just as in the first basic configuration.  
         [0062]    [0062]FIG. 4 shows a liquid crystal display according to a combination of the first and second basic configurations. As shown in FIG. 4, reflective electrodes  20   a  to  20   f  are formed at intersections between bus lines  10  and  12  and above TFTs  14 . The reflective electrodes  20   a  to  20   f  have openings  37   a  to  37   f  that are formed in various configurations.  
         [0063]    For example, the reflective electrode  20   a  is formed with a plurality of openings  37   a  constituted of V-shaped slits extending at an angle to longer sides of the reflective electrodes  20   a . The reflective electrode  20   b  is formed with a plurality of triangular openings  37   b . The reflective electrode  20   c  is formed with a plurality of elongate rhombic openings  37   c  extending in parallel with shorter sides of the reflective electrode  20   c . The reflective electrode  20   d  is formed with a plurality of hexagonal openings  37   d . The reflective electrode  20   e  is formed with a plurality of straight openings  37   e  extending in parallel with shorter sides of the reflective electrode  20   e . The reflective electrode  20   f  is formed with a plurality of straight openings  37   f  extending in parallel with shorter sides of the reflective electrode  20   f.    
         [0064]    Like the first and second basic configurations, such a configuration also makes it possible to omit the steps for forming transparent electrodes  112  and barrier metal layers  136  for a reduced manufacturing cost.  
         [0065]    Substrates for a liquid crystal display having the first and second basic configurations and liquid crystal displays having the same will now be described with reference to first through seventh embodiments of the invention.  
         [0066]    First, a liquid crystal display according to the first embodiment of the invention will now be described with reference to FIGS. 5 and 6. Since the liquid crystal display of the present embodiment has a configuration substantially similar to the first basic configuration shown in FIGS. 1 and 2, the description will be made with reference to FIGS. 1 and 2. As shown in FIGS. 1 and 2, in the liquid crystal display of the present embodiment, horizontal alignment films made of, for example, polyimide resin are formed on opposite surfaces of a TFT substrate  2  and an opposite substrate  4 , and a predetermined rubbing process is performed on the same. The substrates  2  and  4  are combined with a cell gap dl (of 3 μm, for example) left therebetween, and a nematic liquid crystal having positive dielectric anisotropy (Δn=0.67) is sealed between the substrates  2  and  4 . The alignment of the liquid crystal molecules is a homogeneous alignment in which the major axes of the liquid crystal molecules are in parallel with each other and also in parallel with the substrate surfaces.  
         [0067]    A polarizer  32  is a circular polarization plate that is constituted of a λ/4 phase difference plate  39  provided on a glass substrate  26  and a linear polarization plate  38  provided outside the same. The polarization axis (light transmission axis) of the linear polarization plate  38  and the optic axis (delay axis) of the λ/4 phase difference plate  39  are provided at an angle of 45 degrees. The delay axis denotes the bigger one of the refractive index nx, ny toward inner surfaces of the optical films. Similarly the polarization plate  34  is a circular polarization plate that is constituted of a λ/4 phase difference plate  41  provided on side of the glass substrate  27  and a linear polarization plate  40  outside it. Polarization axis of the linear polarization plate  40  and the delay axis of λ/4 phase difference plate  41  are rotated and fixed at an angle of 45 degrees.  
         [0068]    In the present embodiment, reflective electrodes  20  are provided at intersections between the bus lines  10  and  12  and on the TFTs  14  just as in the first basic configuration, which reduces the area of the bus lines  10  and  12  exposed in the transmissive regions T and T′ to increase the area of the transmissive regions T and T′ without reducing the area of the reflective regions-R and R′. That is, in the present embodiment, regions which have not been used as reflective regions nor transmissive regions in a transflective liquid crystal display according to the related art are used as the transmissive regions T and T′. This makes it possible to improve transmission characteristics without degrading reflection characteristics.  
         [0069]    A display operation of the liquid crystal display of the present embodiment will now be described with reference to FIGS. 5A, 5B,  6 A, and  6 B. FIGS. 5A, 5B,  6 A, and  6 B show states of display of predetermined images on the liquid crystal display of the present embodiment. FIGS. 5A and 5B are microphotographs showing states of display of predetermined images on the liquid crystal display of the present embodiment that are enlarged with a relatively high magnification (about 30×). FIGS. 6A and 6B are microphotographs of states of display of predetermined images on the liquid crystal display of the present embodiment that are enlarged with a relatively low magnification (about 15×). FIGS. 5A and 6A show states of display in the reflective mode, and FIGS. 5B and 6B show states of display in the transmissive mode. As shown in FIGS. 5A, 5B,  6 A, and  6 B, the present embodiment allows display in the transmissive mode without sacrificing high display characteristics in the reflective mode.  
         [0070]    The polarizer  32  used in the present embodiment is a circular polarizer that is a combination of a linear polarizing plate  38  and a λ/4 phase difference plate  39 . Display characteristics of a transmissive display depend on the film used as the λ/4 phase difference plate  39 . Table 1 shows differences in transmission characteristic depending on the λ/4 phase difference plate  39  that forms a part of the polarizer  32  on the backlight side.  
                                   TABLE 1                                       White   Black                   display   display           λ/4 phase difference   (cd/m 2 )   (cd/m 2)     CR                           plate 39 of polarizer 32   5.1   1.9   2.7           one ARTON film           Phase difference film   5.3   1.7   3.0           with reciprocal           wavelength dispersal           No film (linear   6.1   1.2   5.0           polarizer 38 only)                      
 
         [0071]    As shown in Table 1, when a sheet of ARTON film is used as the λ/4 phase difference plate  39  of the polarizer  32 , it provides luminance of 5.1 cd/m 2  for a white display and luminance of 1.9 cd/m 2  for a black display. It provides a contrast ratio (CR) of 2.7.  
         [0072]    When a phase difference film with reciprocal wavelength dispersion is used as the λ/4 phase difference plate  39  of the polarizer  32 , it provides luminance of 5.3 cd/m 2  for a white display and luminance of 1.7 cd/m 2  for a black display. It provides a contrast ratio of 3.0.  
         [0073]    When only the linear polarizer  38  is used without the λ/4 phase difference plate  39 , it provides luminance of 6.1 cd/m 2  for a white display and luminance of 1.2 cd/m 2  for a black display. It provides a contrast ratio 5.0. In this case, however, since brightness and darkness in a display are inverted between the transmissive mode and the reflective mode, grayscale signals must be converted in synchronism with the turning on of the backlight to achieve a desired display.  
         [0074]    It is apparent from the above that the liquid crystal display of the present embodiment can achieve transmission characteristics sufficient for use in a dark place, although it has a contrast ratio lower than that of a transmissive liquid crystal display.  
         [0075]    A description will now be made with reference to FIGS. 7A to  11  on a substrate for a liquid crystal display and a liquid crystal display having the same according to a second embodiment of the invention. Since the liquid crystal display of the present embodiment has a configuration substantially similar to the second basic configuration shown in FIG. 3, the description will be made with reference to FIG. 3. As shown in FIG. 3, in the present embodiment, reflective electrodes  20   a  to  20   e  that constitute reflective regions R are formed in regions defined by gate bus lines  10  and drain bus lines  12 . The reflective electrodes  20   a  to  20   e  have openings  36   a  to  36   e  formed in various configurations. The regions where the openings  36   a  to  36   e  are formed constitute transmissive regions T.  
         [0076]    For example, horizontal alignment films made of polyimide resin are formed on surfaces of a TFT substrate  2  and an opposite substrate  4  (not shown in FIG. 3), and a predetermined rubbing process is performed on the same. The substrates  2  and  4  are combined with a cell gap of 2 μm therebetween for example, and a nematic liquid crystal having positive dielectric anisotropy is sealed between the substrates  2  and  4 . The alignment of the liquid crystal molecules is a homogeneous alignment in which the major axes of the liquid crystal molecules are in parallel with each other and also in parallel with the substrate surfaces.  
         [0077]    A description will now be made with reference to FIGS. 7A to  11 D on principles behind operations of the liquid crystal display of the present embodiment that is in the normally white mode. First, a principle behind operations in the reflective mode will be described. FIGS. 7A and 7B schematically show a sectional configuration of the liquid crystal display of the present embodiment taken in a reflective region R. FIG. 7A shows a white display (a bright state), and FIG. 7B shows a black display (a dark state). A λ/4 phase difference plate  41  is provided on a side of a liquid crystal layer  24  in the reflective region R, the side facing toward a viewer (upward in the figure). A linear polarizer  40  is provided closer to a viewer than is the λ/4 phase difference plate  41 . The linear polarizer  40  has a polarization axis in a direction in parallel with the plane of the drawing. A reflective electrode  20  is provided on the side of the liquid crystal layer  24  opposite to the viewer&#39;s side (facing downward in the figure).  
         [0078]    [0078]FIG. 8 shows an arrangement of optical axes of optical films of the liquid crystal display of the present embodiment as viewed from the viewer&#39;s side. As shown in FIG. 8, an optical axis  44  of the λ/4 phase difference plate  41  on the viewer&#39;s side is rotated counterclockwise at 45 degrees relative to a polarization axis  42  of the linear polarizer  40  on the viewer&#39;s side. A polarization axis  50  of the polarizer  38  on the backlight unit side is rotated clockwise at 45 degrees relative to an optical axis  48  of the λ/4 phase difference plate  39 . Liquid crystal molecules  60  are aligned in parallel with the substrate surfaces.  
         [0079]    In FIGS. 7A and 7B, external light is represented by a linearly polarized light beam Li having a polarization direction in parallel with the polarization axis  42  of the linear polarizer  40  and a linearly polarized light beam L 2  having a polarization direction which is orthogonal to the light beam Li and which is perpendicular to the plane of the drawing. Retardation (Δn·d 1 ) that occurs in the liquid crystal layer  24  in the reflective region R becomes λ/4 when the liquid crystal molecules  60  are aligned in parallel with the substrate surfaces and becomes zero when the liquid crystal molecules  60  are aligned perpendicularly to the substrate surfaces.  
         [0080]    As shown in FIG. 7A, when external light enters the linear polarizer  40  from the viewer&#39;s side, the light beam L 2  is absorbed by the linear polarizer  40 , and only the light beam LI is transmitted by the linear polarizer  40 . When the light beam Li thereafter enters the λ/4 phase difference plate  41  having the optical axis  44  that is rotated counterclockwise at 45 degrees to the polarization direction of the same as viewed from the viewer&#39;s side, it becomes a light beam L 3  that is circularly polarized counterclockwise as viewed from the viewer&#39;s side. Next, the light beam L 3  enters the liquid crystal layer  24 . No voltage is applied to the liquid crystal molecules  60  in the liquid crystal layer  24 , in which state they are aligned substantially in parallel with the substrate surfaces. In this state, the liquid crystal molecules  60  have refractive index anisotropy, which results in retardation of λ/4 in the liquid crystal layer  24 . As a result, the light beam L 3  becomes a linearly polarized light beam L 4  having a polarization direction in parallel with the plane of the drawing, is reflected by reflective electrode  20  and enters the liquid crystal layer  24 . Because of retardation in the liquid crystal layer  24 , the light beam L 4  becomes a light beam L 5  that is circularly polarized clockwise as viewed from the viewer&#39;s side. Then, the light beam L 5  enters the λ/4 phase difference plate  41  and becomes a linearly polarized light beam L 6  which is in parallel with the plane of the drawing and which exits the λ/4 phase difference plate  41 . Since the light beam L 6  has a polarization axis in parallel with the polarization axis  42  of the linear polarizer  40 , it passes through the linear polarizer  40  to exit the same toward the viewer, which results in a white display.  
         [0081]    As shown in FIG. 7B, when external light enters the linear polarizer  40  from the viewer&#39;s side, the light beam L 2  is absorbed by the linear polarizer  40 , and only the light beam L 1  is transmitted by the linear polarizer  40 . Then, the light beam L 1  enters the λ/4 phase difference plate  41  and becomes a light beam L 3  that is circularly polarized counterclockwise as viewed from the viewer&#39;s side. Next, the light beam L 3  enters the liquid crystal layer  24 . A predetermined voltage is applied to the liquid crystal molecules  60  in the liquid crystal layer  24 , in which state they are aligned substantially perpendicularly to the substrate surfaces. In this state, since the liquid crystal molecules  60  have no refractive index anisotropy, there is substantially zero retardation in the liquid crystal layer  24 . Thus, the light beam L 3  enters the reflective electrode  20  while remaining in the counterclockwise circularly polarized state as viewed from the viewer&#39;s side. The light beam L 3  remains in the counterclockwise circularly polarized state as viewed from the viewer&#39;s side though it is reflected by the reflective electrode  20  and becomes a light beam L 7  to enter the liquid crystal layer  24  again. Since there is substantially zero retardation in the liquid crystal layer  24 , the light beam L 7  enters the λ/4 phase difference plate  40  while remaining in the counterclockwise circularly polarized state as viewed from the viewer&#39;s side. It then becomes a linearly polarized light beam L 8  which is perpendicular to the plane of the drawing and which exits the λ/4 phase difference plate  40 . The light beam L 8  is absorbed by the linear polarizer  40  because it has a polarization direction orthogonal to the polarization axis  42  of the linear polarizer  40 , and the light does not exit toward the viewer, which results in a black display.  
         [0082]    A principle of operations in the transmissive mode will be described. FIGS. 9A and 9B schematically show a sectional configuration of the liquid crystal display of the present embodiment taken in a transmissive region T. FIG. 9A shows a white display, and FIG. 9B shows a black display. A λ/4 phase difference plate  39  is provided on a side of liquid crystal layer  24  in the transmissive region T, the side facing toward a backlight unit (downward in the figure). A linear polarizer  38  is provided closer to the backlight unit than is the λ/4 phase difference plate  39 .  
         [0083]    Referring to FIG. 8 again, the optical axis  44  of the λ/4 phase difference plate  41  on the viewer&#39;s side is rotated counterclockwise at 45 degrees relative to the polarization axis  42  of the linear polarizer  40  on the viewer&#39;s side. The polarization axis  50  of the polarizer  38  on the backlight unit side is rotated clockwise at 45 degrees relative to the optical axis  48  of the λ/4 phase difference plate  39 .  
         [0084]    In FIGS. 9A and 9B, illumination light from the backlight unit is represented by a linearly polarized light beam L 11  having a polarization direction in parallel with the polarization axis  50  of the linear polarizer  38  and a linearly polarized light beam L 12  having a polarization direction which is orthogonal to the light beam L 11 . Retardation (Δn·d 2 ) that occurs in the liquid crystal layer  24  in the transmissive region T becomes λ/2 when the liquid crystal molecules  60  are aligned in parallel with the substrate surfaces and becomes substantially zero when the liquid crystal molecules  60  are aligned perpendicularly to the substrate surfaces.  
         [0085]    As shown in FIG. 9A, when the illumination light from the backlight unit enters the linear polarizer  38 , the light beam L 12  is absorbed by the linear polarizer  38 , and only the light beam L 11  is transmitted by the linear polarizer  38 . When the light beam L 11  thereafter enters the λ/4 phase difference plate  39  having the optical axis  48  that is rotated counterclockwise at 45 degrees to the polarization direction of the same as viewed from the viewer&#39;s side, it becomes a light beam L 13  that is circularly polarized counterclockwise as viewed from the viewer&#39;s side. Next, the light beam L 13  enters the liquid crystal layer  24 . No voltage is applied to the liquid crystal molecules  60  in the liquid crystal layer  24 , in which state they are aligned substantially in parallel with the substrate surfaces. In this state, the liquid crystal molecules  60  have refractive index anisotropy, which results in retardation of λ/2 in the liquid crystal layer  24 . As a result, the light beam L 13  becomes a clockwise circularly polarized light beam L 14  as viewed from the viewer&#39;s side. Then, the light beam L 14  enters the λ/4 phase difference plate  41  and becomes a linearly polarized light beam L 15  in parallel with the plane of the drawing to exit the λ/4 phase difference plate  41 . Since the light beam L 15  has a polarization direction in parallel with the polarization axis  42  of the linear polarizer  40 , it passes through the linear polarizer  40  to exit the same toward the viewer, which results in a white display.  
         [0086]    As shown in FIG. 9B, when the illumination light from the backlight unit enters the linear polarizer  38 , the light beam L 12  is absorbed by the linear polarizer  38 , and only the light beam L 11  is transmitted by the linear polarizer  38 . Then, the light beam L 11  enters the λ/4 phase difference plate  39  and becomes a counterclockwise circularly polarized light beam L 16  as viewed from the viewer&#39;s side. Next, the light beam L 16  enters the liquid crystal layer  24 . A predetermined voltage is applied to the liquid crystal molecules  60  in the liquid crystal layer  24 , in which state they are aligned substantially perpendicularly to the substrate surfaces. In this state, since the liquid crystal molecules  60  have no refractive index anisotropy, there is substantially zero retardation in the liquid crystal layer  24 . Thus, the light beam L 16  exits the liquid crystal layer  24  while remaining in the counterclockwise circularly polarized state as viewed from the viewer&#39;s side. The light beam L 16  enters the λ/4 phase difference plate  41  and becomes a linearly polarized light beam L 17  which is perpendicular to the plane of the drawing and which exits the λ/4 phase difference plate  41 . The light beam L 18  is absorbed by the linear polarizer  40  because it has a polarization direction orthogonal to the polarization axis  42  of the linear polarizer  40 , and the light does not exit toward the viewer, which results in a black display.  
         [0087]    [0087]FIGS. 10A to  10 D show states of display of the liquid crystal display of the present embodiment in the reflective mode, and FIGS. 11A to  11 D show states of display of the liquid crystal display of the present embodiment in the transmissive mode. FIGS. 10A and 11A show states of display at a grayscale voltage of 0 V. FIGS. 10B and 11B show states of display at a grayscale voltage of 4.3 V. FIGS. 10C and 11C show states of display at a grayscale voltage of 5 V. FIGS. 10D and 11D show states of display at a grayscale voltage of 8 V.  
         [0088]    As shown in FIG. 10A, the plurality of openings  36  are in the form of a rhombus having a width of 36 μm and a height of 4 μm, for example. Intervals between openings  36  adjacent to each other in the horizontal direction of the figure are 24 μm, and intervals between openings  36  adjacent to each other in the vertical direction of the figure are 20 μm.  
         [0089]    As shown in FIGS. 10A to  10 D, in the reflective mode, the liquid crystal display of the present embodiment provides a white display at the grayscale voltage of 0 V and provides darker displays as the grayscale voltage increases. The liquid crystal display of the present embodiment provides a black display at the grayscale voltage of 8 V. As shown in FIGS. 11A to  11 D, in the transmissive mode, the liquid crystal display of the present embodiment provides a white display at the grayscale voltage of 0 V and provides darker displays as the grayscale voltage increases. The liquid crystal display of the present embodiment provides a black display at the grayscale voltage of 8 V. Thus, the present embodiment provides good display characteristics in both of the reflective and transmissive modes as shown in FIGS. 10A to  11 D.  
         [0090]    A description will now be made with reference to FIGS.  12  to  14 D on a substrate for a liquid crystal display and a liquid crystal display having the same according to a third embodiment of the invention. The present embodiment is different from the second embodiment in that vertical alignment films made of polyimide resin, for example, are formed on surfaces of a TFT substrate  2  and an opposite substrate  4  facing each other. The substrates  2  and  4  are combined with a cell gap of 3 μm therebetween for example, and a nematic liquid crystal having negative dielectric anisotropy (Δn=0.08; ΔE=−4) is sealed between the substrates  2  and  4 . The alignment of the liquid crystal molecules is a homeotropic alignment in which the major axes of the liquid crystal molecules are in parallel with each other and are perpendicular to the substrate surfaces.  
         [0091]    [0091]FIG. 12 shows an arrangement of optical axes of optical films of the liquid crystal display of the present embodiment as viewed from the viewer&#39;s side. Unlike the second embodiment shown in FIG. 8, the alignment of liquid crystal molecules  60  is oriented in a direction perpendicular to the plane of the drawing when no voltage is applied thereto. The arrangement of the optical axes of the optical films is similar to that in the second embodiment.  
         [0092]    [0092]FIGS. 13A to  13 D show states of display of the normally black mode liquid crystal display of the present embodiment in the reflective mode, and FIGS. 14A to  14 D show states of display of the normally black mode liquid crystal display of the present embodiment in the transmissive mode. FIGS. 13A and 14A show states of display at a grayscale voltage of 0 V. FIGS. 13B and 14B show states of display at a grayscale voltage of 4.3 V. FIGS. 13C and 14C show states of display at a grayscale voltage of 5 V. FIGS. 13D and 14D show states of display at a grayscale voltage of 8 V.  
         [0093]    As shown in FIGS. 13A to  13 D, in the reflective mode, the liquid crystal display of the present embodiment provides a black display at the grayscale voltage of 0 V and provides brighter displays as the grayscale voltage  3  increases. The liquid crystal display of the present embodiment provides a white display at the grayscale voltage of 8 V. As shown in FIGS. 14A to  14 D, in the transmissive mode, the liquid crystal display of the present embodiment provides a black display at the grayscale voltage of 0 V and provides brighter displays as the grayscale voltage increases. The liquid crystal display of the present embodiment provides a white display at the grayscale voltage of 8 V. Thus, the present embodiment provides good display characteristics in both of the reflective and transmissive modes as shown in FIGS. 13A to  14 D.  
         [0094]    A description will now be made with reference to FIGS.  15  to  17 D on a substrate for a liquid crystal display and a liquid crystal display having the same according to a fourth embodiment of the invention. The liquid crystal display of the present embodiment has a configuration substantially similar to that of the second embodiment except for the orientation of the alignment of liquid crystal molecules  60  and the shape of openings  36 .  
         [0095]    [0095]FIG. 15 shows an arrangement of optical axes of optical films of the liquid crystal display of the present embodiment as viewed from a viewer&#39;s side. Unlike the second embodiment shown in FIG. 8, the alignment of liquid crystal molecules  60  is oriented in a direction in parallel with a phase-delay axis  44  of a λ/4 phase difference plate  41  when no grayscale voltage is applied thereto. The arrangement of the optical axes of the optical films is similar to that in the second embodiment.  
         [0096]    [0096]FIGS. 16A to  16 D show states of display of the normally white mode liquid crystal display of the present embodiment in the reflective mode, and FIGS. 17A to  17 D show states of display of the normally white mode liquid crystal display of the present embodiment in the transmissive mode. FIGS. 16A and 17A show states of display at a grayscale voltage of 0 V. FIGS. 16B and 17B show states of display at a grayscale voltage of 4.3 V. FIGS. 16C and 17C show states of display at a grayscale voltage of 5 V. FIGS. 16D and 17D show states of display at a grayscale voltage of 8 V. As shown in FIG. 16A, the plurality of openings  36  are in the form of a rhombus having a width of 37 μm and a height of 5 μm, for example. Intervals between openings  36  adjacent to each other in the horizontal direction of the figure are 23 μm, and intervals between openings  36  adjacent to each other in the vertical direction of the figure are 5 μm.  
         [0097]    As shown in FIGS. 16A to  16 D, in the reflective mode, the liquid crystal display of the present embodiment provides a white display at the grayscale voltage of 0 V and provides darker displays as the grayscale voltage increases. The liquid crystal display of the present embodiment provides a black display at the grayscale voltage of 8 V. As shown in FIGS. 17A to  17 D, in the transmissive mode, the liquid crystal display of the present embodiment provides a white display at the grayscale voltage of 0 V and provides darker displays as the grayscale voltage increases. The liquid crystal display of the present embodiment provides a black display at the grayscale voltage of 8 V. Thus, the present embodiment provides good display characteristics in both of the reflective and transmissive modes as shown in FIGS. 16A to  17 D.  
         [0098]    A description will now be made with reference to FIGS.  18  to  20 D on a substrate for a liquid crystal display and a liquid crystal display having the same according to a fifth embodiment of the invention. The liquid crystal display of the present embodiment has a configuration substantially similar to that of the fourth embodiment except for the shape of openings  36 .  
         [0099]    [0099]FIG. 18 shows an arrangement of optical axes of optical films of the liquid crystal display of the present embodiment as viewed from a viewer&#39;s side. The arrangement of the optical axes of the optical films is similar to that in the second embodiment.  
         [0100]    [0100]FIGS. 19A to  19 D show states of display of the normally white mode liquid crystal display of the present embodiment in the reflective mode, and FIGS. 20A to  20 D show states of display of the normally white mode liquid crystal display of the present embodiment in the transmissive mode. FIGS. 19A and 20A show states of display at a grayscale voltage of 0 V. FIGS. 19B and 20B show states of display at a grayscale voltage of 4.3 V. FIGS.  19 C and  20 C show states of display at a grayscale voltage of 5 V. FIGS. 19D and 20D show states of display at a grayscale voltage of 8 V. As shown in FIG. 19A, the plurality of openings  36  are in the form of a rectangle having a width of 30 μm and a height of 6 μm, for example. Intervals between openings  36  adjacent to each other in the horizontal direction of the figure are 30 μm, and intervals between openings  36  adjacent to each other in the vertical direction of the figure are 25 μm.  
         [0101]    As shown in FIGS. 19A to  19 D, in the reflective mode, the liquid crystal display of the present embodiment provides a white display at the grayscale voltage of 0 V and provides darker displays as the grayscale voltage increases. The liquid crystal display of the present embodiment provides a black display at the grayscale voltage of 8 V. As shown in FIGS. 20A to  20 D, in the transmissive mode, the liquid crystal display of the present embodiment provides a white display at the grayscale voltage of 0 V and provides darker displays as the grayscale voltage increases. The liquid crystal display of the present embodiment provides a black display at the grayscale voltage of 8 V. Thus, the present embodiment provides good display characteristics in both of the reflective and transmissive modes as shown in FIGS. 19A to  20 D.  
         [0102]    A description will now be made with reference to FIG. 21 on a substrate for a liquid crystal display and a liquid crystal display having the same according to a sixth embodiment of the invention. As shown in FIG. 21, the liquid crystal display of the present embodiment is an IPS (In-Plane Switching) mode liquid crystal display in which liquid crystal molecules are driven by a transverse electric field. A comb-shaped reflective electrode  21  and a comb-shaped common electrode  31  facing the reflective electrode  21  are provided in each pixel region on a TFT substrate  2 . The region where the reflective electrode  21  and the common electrode  31  are formed serves as a reflective region R, and the region between the electrodes  21  and  31  serves as a transmissive region T. Alignment films formed on the TFT substrate  2  and an opposite substrate  4  may be either horizontal alignment films or vertical alignment films. The present embodiment can provide advantages similar to those of the first embodiment.  
         [0103]    A substrate for a liquid crystal display according to a seventh embodiment of the invention will now be described with reference to FIGS. 22A and 22B and FIG. 23. FIGS. 22A and 22B show a schematic configuration of the substrate for a liquid crystal display of the present embodiment. FIG. 22A shows a sectional configuration of a TFT substrate  2  of the present embodiment, and FIG. 22B shows the section of the TFT substrate  2  before the formation of openings  36 .  
         [0104]    As shown in FIG. 22A, a plurality of recesses and projections are formed on a surface of a planarization film  28 . A reflective electrode  20  is formed on the planarization film  28 . On a surface of the reflecting film  20 , recesses and projections are formed in association with the recesses and projections formed on the surface of the planarization film  28  located under the same. A plurality of openings  36  are formed on the reflective electrode  20 . The openings  36  are formed in substantially flat regions  72  as shown in FIG. 22B where the surface of the reflective electrode  20  is at an average inclination of 5 degrees or less to the substrate surface.  
         [0105]    [0105]FIG. 23 shows changes in reflectivity Y of the reflective electrode  20  depending on an average inclination k. The abscissa axis represents the average inclination k (deg.) of the reflective electrode  20  relative to the substrate surface, and the ordinate axis represents the reflectivity Y (%) in a direction perpendicular to the substrate surface. Parallel light at incident angles of 0 deg., 15 degrees, 30 degrees, and 40 degrees and diffuse light produced using an integrating sphere are used as incident light.  
         [0106]    As shown in FIG. 23, the greater the incident angle of parallel light, the greater the average inclination k that yields the maximum reflectivity Y. It is apparent that an average inclination k in a range of 5 degrees or less does not contribute to improvement of reflection characteristics in an actual environment because light enters the liquid crystal display in various directions in an actual environment of use. Therefore, transmission characteristics can be improved while suppressing reduction of reflection characteristics by forming the openings  36  in the substantially flat regions  72  where the average inclination k is 5 degrees or less. The present embodiment makes it possible to provide a transflective liquid crystal display that utilizes light with high efficiency.  
         [0107]    A description will now be made with reference to FIGS.  24  to  26  on a substrate for a liquid crystal display and a liquid crystal display having the same according to an eighth embodiment of the invention. FIG. 24 shows a sectional configuration of the substrate for a liquid crystal display and the liquid crystal display having the same of the present embodiment. FIG. 24 omits a planarization film  28  that makes a cell gap dl in a reflective region R substantially equal to one-half of a cell gap d 2  in a transmissive region T. As shown in FIG. 24, an opposite substrate  4  has a CF layer  70  on a glass substrate  27 . The CF layer  70  is formed such that it has a thickness in a transmissive region T that is substantially twice the thickness of the same in a reflective region R and is formed with different degrees of color purity. The present embodiment provides improved display characteristics because there is no chromatic deviation between the reflective mode and transmissive mode.  
         [0108]    [0108]FIG. 25 shows a modification of the substrate for a liquid crystal display and the liquid crystal display having the same of the present embodiment. FIG. 25 omits a planarization film  28  that makes a cell gap dl in a reflective region R substantially equal to one-half of a cell gap d 2  in a transmissive region T. As shown in FIG. 25, a TFT substrate  2  has a CF layer  70  on a glass substrate  20 . Since the surface of the CF layer  70  is substantially flatly formed, the CF layer  70  is formed such that it is different in thickness between a reflective region R where a reflective electrode  20  is formed and a transmissive region T where no reflective electrode  20  is formed. The present embodiment provides improved display characteristics because there is no chromatic deviation between the reflective mode and transmissive mode.  
         [0109]    [0109]FIG. 26 shows another modification of the substrate for a liquid crystal display and the liquid crystal display having the same of the present embodiment. FIG. 26 omits a planarization film  28  that makes a cell gap d 1  in a reflective region R substantially equal to one-half of a cell gap d 2  in a transmissive region T. As shown in FIG. 26, a thickness adjusting film  74  for adjusting the thickness of a CF layer  70  in reflective regions R is formed under reflective electrodes  20 . For example, the thickness adjusting film  74  is formed of the same material as that of a protective film (not shown) for TFTs  14  at the same time when the latter is formed. Since the surface of the CF layer  70  is substantially flatly formed, the CF layer  70  is formed such that it is different in thickness between the reflective regions R and transmissive regions T. The present embodiment provides improved display characteristics because there is no chromatic deviation between the reflective mode and transmissive mode.  
         [0110]    As described above, in the present mode for carrying out the invention, it is possible to provide a substrate for a liquid crystal display and a liquid crystal display having the same which achieve excellent display characteristics at a low cost.  
         [0111]    Second Mode for Carrying Out the Invention  
         [0112]    Second Mode for Carrying Out the Invention  
         [0113]    A liquid crystal display in a second mode for carrying out the invention will now be described with reference to FIGS. 27 and 28. FIG. 27 shows a configuration of the liquid crystal display in the present mode for carrying out the invention. Components having functions and effects like those in the liquid crystal display in the first mode for carrying out the invention are indicated by like reference numerals and will not be described here. As shown in FIG. 27, reflective electrodes  20   a  to  20   e  that constitute reflective regions of a transflective liquid crystal display are formed in regions defined by gate bus lines  10  and drain bus lines  12 . The reflective electrodes  20   a ,  20   b ,  20   d , and  20   e  are respectively formed with openings  36   a ,  36   b ,  36   d , and  36   e  formed in various configurations such as slits and circular holes. Notches  36   a ′ to  36   e ′ in various configurations such as slits and circular or polygonal holes are formed at the periphery of the reflective electrodes  20   a  to  20   e , respectively.  
         [0114]    For example, the reflective electrode  20   a  is formed with one opening  36   a  in the form of a slit extending substantially in parallel with longer sides of the reflective electrode  20   a  and a plurality of notches  36   a ′ in the form of slits that are inwardly cut at the two longer sides of the reflecting electrode  20   a  opposite to each other and that extend at an angle to the longer sides. The reflective electrode  20   b  is formed with a plurality of opening  36   b  in the form of slits extending substantially in parallel with shorter sides of the reflective electrode  20   b  and a plurality of notches  36   b ′ in the form of slits that are inwardly cut at two longer sides of the reflecting electrode  20   b  and that extend substantially in parallel with the shorter sides thereof. The reflective electrode  20   c  has a plurality of notches  36   c ′ adjacent to each other in the form of wedges that are inwardly cut at two longer sides of the reflective electrode  20   c  and that extend substantially in parallel with shorter sides of the reflective electrode  20   c . The reflective electrode  20   d  is formed with a plurality of circular openings  36   d  and a plurality of circular notches  36   d ′ that are inwardly cut at two longer sides and two shorter sides of the reflecting electrode  20   d . The reflective electrode  20   e  is formed with one opening  36   e  in the form of a slit extending substantially in parallel with longer sides of the reflective electrode  20   e  and a plurality of notches  36   e ′ in the form of wedges that are inwardly cut at two longer sides of the reflecting electrode  20   e  and that extend substantially in parallel with shorter sides of the reflective electrode  20   e.    
         [0115]    The regions where the reflective electrodes  20   a  to  20   e  are formed serve as reflective regions. The regions where the openings  36   a ,  36   b ,  36   d , and  36   e  and the regions at the periphery of the reflective electrodes  20   a  to  20   e  where the notches  36   a ′ to  36   e ′ are formed serve as transmissive regions. No transparent electrode is formed at the openings  36   a ,  36   b ,  36   d , and  36   e  and the notches  36   a ′ to  36   e ′. Liquid crystal molecules in the transmissive regions are driven by an oblique field that is present between edges of the reflective electrodes  20   a  to  20   e  and a common electrode  52  (not shown in FIG. 27) at the opposite substrate  4  substantially similarly to liquid crystal molecules in the respective reflective regions at the same pixels.  
         [0116]    While the openings  36   a ,  36   b ,  36   d , and  36   e  and the notches  36   a ′ to  36   e ′ in FIG. 27 are formed in configurations that vary from pixel to pixel, the openings  36   a ,  36   b ,  36   d , and  36   e  and the notches  36   a ′ to  36   e ′ may be formed in the same configuration in the respective pixels. The openings  36   a ,  36   b ,  36   d , and  36   e  and the notches  36   a ′ to  36   e ′ may have a configuration to regulate alignment of liquid crystal molecules. As a result, in a VA (Vertical Aligned) mode liquid crystal display in which liquid crystal molecules are aligned substantially perpendicularly to the substrate surface, separate alignments can be achieved without a process of rubbing the alignment film. The present mode for carrying out the invention may be applied to a liquid crystal display in the TN mode utilizing a horizontal alignment film or the HAN (Hybrid Aligned Nematic) mode utilizing a horizontal alignment film in one direction and a vertical alignment film in another, although a rubbing process is required. In the present mode for carrying out the invention, it is possible to achieve transmission characteristics higher than those of a transflective liquid crystal display in the related art.  
         [0117]    [0117]FIG. 28 shows a modification of the configuration of the liquid crystal display in the present mode for carrying out the invention. As shown in FIG. 28, reflective electrodes  20   f  to  20   k  are formed at intersections between bus lines  10  and  12  and above TFTs  14 . Openings  36   i  and notches  36   f ′ to  36   k ′ having various configurations are formed at the reflective electrodes  20   f  to  20   k.    
         [0118]    For example, the reflective electrode  20   f  is formed with a plurality of notches  36   f ′ that are inwardly cut at two longer sides and one shorter side of the reflective electrode  20   f  and that extend at an angle to the longer sides of the reflective electrode  20   f . The reflective electrode  20   g  is formed with a plurality of triangular notches  36   g ′ that are inwardly cut at two longer sides of the reflective electrode  20   g . The reflective electrode  20   h  is formed with a plurality of notches  36   h ′ adjacent to each other in the form of wedges that are inwardly cut at two longer sides of the reflective electrode  20   h  and that extend substantially in parallel with shorter sides of the reflective electrode  20   h . The reflective electrode  20   i  is formed with a plurality of hexagonal openings  36   i  and a plurality of hexagonal notches  36   i ′ that are inwardly cut at two longer sides of the reflecting electrode  20   i . The reflective electrode  20   j  is formed with a plurality of notches  36   j ′ in the form of slits that are inwardly cut at a shorter side of the reflective electrode  20   j  and that extend substantially in parallel with longer sides of the reflective electrode  20   j . The reflective electrode  20   k  is formed with a plurality of notches  36   k ′ in the form of slits that are inwardly cut at two longer sides of the reflective electrode  20   k  and that extend substantially in parallel with shorter sides of the reflective electrode  20   k . The ends of the notches  36   k ′ are circularly rounded.  
         [0119]    The regions where the reflective electrodes  20   f  to  20   k  are formed serve as reflective regions. The regions where the openings  36   i  are formed, the regions at the periphery of the reflective electrodes  20   f  to  20   k  where the notches  36   f ′ to  36   k ′ are formed, and the regions around the reflective electrodes  20   f  to  20   k  serve as transmissive regions. The present modification makes it possible to achieve transmission characteristics higher than those of a transflective liquid crystal display in the related art.  
         [0120]    The invention is not limited to the above-described modes for carrying out the same, and various modifications are possible. For example, while light scattering characteristics are improved by recesses and projections formed on the surface of the reflective electrodes  20  in the above-described modes for carrying out the invention, the invention is not limited to the same. Light scattering characteristics may be improved by forming the reflective electrodes  20  may be formed with a flat surface (mirror surface) and by providing a forward scattering plate on the opposite substrate  4  on the viewer&#39;s side.  
         [0121]    As described above, the invention makes it possible to provide a substrate for a liquid crystal display and a liquid crystal display having the same which achieve excellent display characteristics at a low cost.