Patent Publication Number: US-2010118238-A1

Title: Liquid crystal display device

Description:
TECHNICAL FIELD 
     The present invention relates to a reflection-type or transflective-type liquid crystal display device capable of performing display by utilizing reflected light. 
     BACKGROUND ART 
     Liquid crystal display devices (LCDs) include the transmission-type liquid crystal display device which utilizes backlight from behind the display panel as a light source for displaying, the reflection-type liquid crystal display device which utilizes reflected light of external light, and the transflective-type liquid crystal display device (reflection/transmission-type liquid crystal display device) which utilizes both reflected light of external light and backlight. The reflection-type liquid crystal display device and the transflective-type liquid crystal display device are characterized in that they have smaller power consumptions than that of the transmission-type liquid crystal display device, and their displayed images are easy to see in a bright place. The transflective-type liquid crystal display device is characterized in that its screen is easier to see than that of the reflection-type liquid crystal display device, even in a dark place. 
       FIG. 10  is a cross-sectional view showing an active matrix substrate  100  in a conventional reflection-type liquid crystal display device (e.g., Patent Document 1). 
     As shown in this figure, the active matrix substrate  100  includes an insulative substrate  101 , as well as a gate layer  102 , a gate insulating layer  104 , a semiconductor layer  106 , a metal layer  108 , and a reflective layer  110 , which are stacked on the insulative substrate  101 . After being stacked on the insulative substrate  101 , the gate layer  102 , the gate insulating layer  104 , the semiconductor layer  106 , and the metal layer  108  are subjected to etching by using one mask, thus being formed so as to have an island-like multilayer structure. Thereafter, the reflective layer  110  is formed on this multilayer structure, whereby a reflection surface  112  having ruggednesses is formed. Although not shown, transparent electrodes, a liquid crystal layer, a color filter substrate (CF substrate), and the like are stacked above the active matrix substrate  100 . 
       FIG. 11  is a cross-sectional view of a conventional transflective-type liquid crystal display device (e.g., Patent Document 2). 
     As shown in this figure, in the conventional transflective-type liquid crystal display device, an interlayer insulating film  204  is formed on a drain electrode  222  of a switching element (TFT)  203 , and a galvanic corrosion preventing film  205 , a reflection electrode film  206 , and an amorphous transparent electrode film  218  are stacked on the interlayer insulating film  204 . The region where the reflection electrode film  206  is formed is a reflection region of the transflective-type liquid crystal display device. Ruggednesses are formed in an upper portion of the interlayer insulating film  204  within the reflection region, and conforming to these ruggednesses, ruggednesses are also formed on the galvanic corrosion preventing film  205 , the reflection electrode film  206 , and the amorphous transparent electrode film  218 . 
     Moreover, in the case where ruggednesses are repeatedly disposed on a reflective layer at a uniform interval, a diffraction pattern (moiré) or coloration may occur in the reflected light due to interference of light. Patent Document 3 describes a liquid crystal display device in which some of the ruggednesses are disposed irregularly in order to suppress occurrence of such a diffraction pattern or the like. 
     [Patent Document 1] Japanese Laid-Open Patent Publication No. 9-54318 
     [Patent Document 2] Japanese Laid-Open Patent Publication No. 2005-277402 
     [Patent Document 3] Japanese Laid-Open Patent Publication No. 2002-14211 
     DISCLOSURE OF INVENTION 
     Problems to be Solved by the Invention 
     In the active matrix substrate  100  described in Patent Document 1, portions of the reflective layer  110  are formed so as to reach the insulative substrate  101  in portions where the gate layer  102  and the like are not formed (i.e., portions between the islands, hereinafter referred to as “gap portions”). Therefore, in the gap portions, the surface of the reflection surface  112  is recessed in the direction of the insulative substrate  101 , thus forming a plane having deep dents (or recesses). 
     In the reflection-type liquid crystal display device or the transflective-type liquid crystal display device, in order to perform bright display with a wide viewing angle, it is necessary to allow incident light entering the display device to be more uniformly and efficiently reflected by the reflection surface  112  across the entire display surface, without causing specular reflection in one direction. For this purpose, it is better if the reflection surface  112  has moderate ruggednesses rather than being a complete plane. 
     However, the reflection surface  112  of the aforementioned active matrix substrate  100  has deep dents. Therefore, light is unlikely to reach the reflection surface located in lower portions of the dents, and even if at all light reaches there, the reflected light thereof is unlikely to be reflected toward the liquid crystal layer, thus resulting in a problem in that the reflected light is not effectively utilized for displaying. Furthermore, many portions of the reflection surface  112  have a large angle with respect to the display surface of the liquid crystal display device, thus resulting in a problem in that so that the reflected light from those portions is not effectively utilized for displaying. 
       FIG. 12  is a diagram showing a relationship between the tilt of the reflection surface  112  and reflected light.  FIG. 12(   a ) shows a relationship between an incident angle a and an outgoing angle β when light enters a medium b having a refractive index Nb from a medium a having a refractive index Na. In this case, according to Snell&#39;s Law, the following relationship holds true. 
       Na×sin α=Nb×sin β 
       FIG. 12(   b ) is a diagram showing a relationship between incident light and reflected light when incident light perpendicularly entering the display surface of a liquid crystal display device is reflected from a reflection surface which is tilted by θ with respect to the display surface (or the substrate). As shown in the figure, the incident light perpendicularly entering the display surface is reflected from the reflection surface which is tilted by angle θ with respect to the display surface, and goes out in a direction of an outgoing angle φ. 
     Results of calculating the outgoing angle φ according to Snell&#39;s Law with respect to each angle θ of the reflection surface are shown in Table 1. 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 θ 
                 φ 
                 90 − φ 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 0 
                 0 
                 90 
               
               
                 2 
                 6.006121 
                 83.99388 
               
               
                 4 
                 12.04967 
                 77.95033 
               
               
                 6 
                 18.17181 
                 71.82819 
               
               
                 8 
                 24.42212 
                 65.57788 
               
               
                 10 
                 30.86588 
                 59.13412 
               
               
                 12 
                 37.59709 
                 52.40291 
               
               
                 14 
                 44.76554 
                 45.23446 
               
               
                 16 
                 52.64382 
                 37.35618 
               
               
                 18 
                 61.84543 
                 28.15457 
               
               
                 20 
                 74.61857 
                 15.38143 
               
               
                 20.5 
                 79.76542 
                 10.23458 
               
               
                 20.6 
                 81.12757 
                 8.872432 
               
               
                 20.7 
                 82.73315 
                 7.266848 
               
               
                 20.8 
                 84.80311 
                 5.19888 
               
               
                 20.9 
                 88.85036 
                 1.149637 
               
               
                 20.905 
                 89.79914 
                 0.200856 
               
               
                   
               
            
           
         
       
     
     The values in this Table are calculated by assuming that air has a refractive index of 1.0 and the glass substrate and the liquid crystal layer have a refractive index of 1.5. As shown in Table 1, when the angle θ of the reflection surface exceeds 20 degrees, the outgoing angle φ becomes very large (i.e., 90-φ becomes very small), so that most of the outgoing light does not reach the user. Therefore, even if ruggednesses are provided on the reflection surface of the reflective layer, in order to effectively utilize reflected light, it must be ensured in more portions of the reflection surface that the angle θ is 20 degrees or less. 
     Since the reflection surface  112  of the aforementioned active matrix substrate  100  has many portions which are greater than 20 degrees, reflected light is not very effectively used for displaying. In order to solve this problem, it might be possible to form an insulating layer under the reflective layer  110  and form the reflective layer  110  upon this insulating layer. However, in this case, a step of forming an insulating layer and a step of forming contact holes for connecting the reflective layer  110  to the drains of the TFTs in the insulating layer are needed, thus resulting in a problem of an increase in the material and the number of steps. 
     Moreover, in the transflective-type liquid crystal display device of Patent Document 2, after stacking the interlayer insulating film  204  on the drain electrode  222 , a step of forming ruggednesses in an upper portion thereof is needed, and a step of stacking the galvanic corrosion preventing film  205 , the reflection electrode film  206 , and the amorphous transparent electrode film  218  further thereupon is needed. Thus, the conventional transflective-type liquid crystal display device also has a problem in that the material and number of steps are increased for forming the reflection region. 
     Furthermore, in a conventional transflective-type liquid crystal display device, ruggednesses are formed on the surface of the amorphous transparent electrode film  218 , which is in contact with the liquid crystal layer  211 , and therefore the electric field which is formed across the liquid crystal layer  211  is not uniform, thus making it difficult to uniformly control the liquid crystal orientation in a desired direction in the reflection region. Moreover, although a slope which conforms to the end shape of the interlayer insulating film  204  is formed at an end of the amorphous transparent electrode film  218 , there is also a problem in that this slope disturbs the orientation of the liquid crystal near the end of the reflection region. 
     In the liquid crystal display device of Patent Document 3, ruggednesses are formed by photolithography technique on a photosensitive resin layer which is formed over switching elements, and thereafter a reflective layer is formed on the ruggednesses. Therefore, in this liquid crystal display device, too, problems similar to those of the transflective-type liquid crystal display device of Patent Document 2 described above will occur. 
     The present invention has been made in view of the above problems, and an objective thereof is to provide at low cost reflection-type and transflective-type liquid crystal display devices having a high image quality, in which moiré or coloration due to interference of reflected light and the like is reduced. 
     Means for Solving the Problems 
     A liquid crystal display device according to the present invention is a liquid crystal display device having a plurality of pixels, and comprising, in each of the plurality of pixels, a reflection region for reflecting incident light toward a display surface, wherein, the reflection region includes a metal layer, a semiconductor layer formed on the metal layer, and a reflective layer formed on the semiconductor layer; a plurality of first recesses or protrusions and a plurality of second recesses or protrusions are formed on a surface of the reflective layer; the plurality of first recesses or protrusions are formed so as to conform to the shapes of recesses (including apertures) or protrusions of the metal layer, and the plurality of second recesses or protrusions are formed so as to conform to the shapes of recesses (including apertures) or protrusions of the semiconductor layer; and the plurality of first recesses or protrusions have a plurality of first pairs of first recesses or protrusions adjoining along a first direction, the plurality of first pairs including two pairs whose intervals between recesses or protrusions are different from each other, or the plurality of second recesses or protrusions have a plurality of second pairs of second recesses or protrusions adjoining along a second direction, the plurality of second pairs including two pairs whose intervals between recesses or protrusions are different from each other. 
     In one embodiment, the plurality of first recesses or protrusions have a plurality of third pairs of first recesses or protrusions adjoining along a third direction which is different from the first direction, and the plurality of third pairs include two pairs whose intervals between recesses or protrusions are different from each other. 
     In one embodiment, the plurality of second recesses or protrusions have a plurality of fourth pairs of second recesses or protrusions adjoining along a fourth direction which is different from the second direction, and the plurality of fourth pairs include two pairs whose intervals between recesses or protrusions are different from each other. 
     In one embodiment, the plurality of first recesses or protrusions have a plurality of third pairs of first recesses or protrusions adjoining along a third direction which is different from the first direction, and the plurality of third pairs include two pairs whose intervals between recesses or protrusions are different from each other; and the plurality of second recesses or protrusions have a plurality of fourth pairs of second recesses or protrusions adjoining along a fourth direction which is different from the second direction, and the plurality of fourth pairs include two pairs whose intervals between recesses or protrusions are different from each other. 
     In one embodiment, on the surface of the reflective layer, at least either the plurality of first recesses or protrusions or the plurality of second recesses or protrusions are randomly disposed. 
     In one embodiment, on the surface of the reflective layer, both the plurality of first recesses or protrusions and the plurality of second recesses or protrusions are randomly disposed. 
     One embodiment comprises a semiconductor element provided corresponding to each of the plurality of pixels, wherein, the metal layer, the semiconductor layer, and the reflective layer are made of same materials as those of a gate electrode, a semiconductor portion, and source and drain electrodes of the semiconductor element, respectively. 
     One embodiment comprises a liquid crystal layer and an interlayer insulating layer and a pixel electrode interposed between the liquid crystal layer and the reflective layer, wherein a surface of the pixel electrode facing the liquid crystal layer is formed flat without conforming to shapes of the first recesses or protrusions and the second recesses or protrusions of the reflective layer. 
     Effects of the Invention 
     According to the present invention, reflection-type and transflective-type liquid crystal display devices having a high image quality, in which moiré or coloration due to interference of reflected light and the like is reduced, can be provided at low cost. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  A diagram schematically showing a cross-sectional shape of a liquid crystal display device according to Embodiment 1. 
         FIG. 2  Plan views showing a liquid crystal display device of Embodiment 1, where (a) shows the construction of a pixel region, and (b) shows the construction of a reflection section. 
         FIG. 3  Cross-sectional views showing the construction of a TFT section and a reflection section of Embodiment 1, where (a) shows the construction of a reflection section, and (b) shows the construction of a TFT section. 
         FIG. 4  A schematic diagram for comparison of a liquid crystal display device of Embodiment 1 and a conventional liquid crystal display device with respect to their reflection section constructions, where (a) is a diagram showing a cross section of a reflection section of Embodiment 1, (b) is a diagram showing a cross section of a reflection section of a conventional liquid crystal display device, and (c) is a diagram describing surface angles at a corner portion of the reflection section. 
         FIG. 5  Plan views showing a production method for a reflection section of Embodiment 1. 
         FIG. 6  Cross-sectional views showing a production method for a reflection section of Embodiment 1. 
         FIG. 7  A plan view showing a reflection section of a liquid crystal display device according to Embodiment 2. 
         FIG. 8  A plan view showing a reflection section of a liquid crystal display device according to Embodiment 3. 
         FIG. 9  A cross-sectional view showing a liquid crystal display device according to Embodiment 4. 
         FIG. 10  A cross-sectional view showing an active matrix substrate of a conventional reflection-type liquid crystal display device. 
         FIG. 11  A cross-sectional view of a conventional transflective-type liquid crystal display device. 
         FIG. 12  A diagram showing a relationship between a tilt of a reflection surface and reflected light in a liquid crystal display device, where (a) shows a relationship between an incident angle α and an outgoing angle β when light enters a medium b having a refractive index Nb from a medium a having a refractive index Na, and (b) is a diagram showing a relationship between incident light and reflected light as well as the angle of the display surface of the liquid crystal display device. 
     
    
    
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
           10  liquid crystal display device 
           12  TFT substrate 
           14  counter substrate 
           16  liquid crystal 
           18  liquid crystal layer 
           22  transparent substrate 
           26  interlayer insulating layer 
           28  pixel electrode 
           30  reflection section 
           31  layer 
           32  TFT section 
           34  counter electrode 
           36  CF layer 
           38  transparent substrate 
           40  display surface 
           42  reflection region 
           44  TFT region 
           46  transmission region 
           50  pixel 
           52  source line 
           54  gate line 
           56  Cs metal layer 
           58  contact hole 
           61  gate insulating layer 
           62  semiconductor layer 
           63  reflective layer 
           65  aperture 
           67  protrusion 
           68 ,  69  recess 
           100  active matrix substrate 
           101  insulative substrate 
           102  gate layer 
           104  gate insulating layer 
           106  semiconductor layer 
           108  metal layer 
           110  reflective layer 
           112  reflection surface 
           203  switching element 
           204  interlayer insulating film 
           205  galvanic corrosion preventing film 
           206  reflection electrode film 
           211  liquid crystal layer 
           218  amorphous transparent electrode film 
           222  drain electrode 
       
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Embodiment 1 
     Hereinafter, with reference to the drawings, a first embodiment of the liquid crystal display device according to the present invention will be described. 
       FIG. 1  is a diagram schematically showing a cross-sectional shape of a liquid crystal display device  10  of the present embodiment. The liquid crystal display device  10  is a transflective-type liquid crystal display device (LCD) by an active matrix method. As shown in  FIG. 1 , the liquid crystal display device  10  includes a TFT (Thin Film Transistor) substrate  12 , a counter substrate  14  such as a color filter substrate (CF substrate), and a liquid crystal layer  18  containing liquid crystal  16  which is sealed between the TFT substrate  12  and the counter substrate  14 . 
     The TFT substrate  12  includes a transparent substrate  22 , an interlayer insulating layer  26 , and a pixel electrode  28 , and includes reflection sections  30  and TFT sections  32 . Note that gate lines (scanning lines), source lines (signal lines), Cs lines (storage capacitor electrode lines), and the like are also formed on the TFT substrate  12 , which will be described later. 
     The counter substrate  14  includes a counter electrode  34 , a color filter layer (CF layer)  36 , and a transparent substrate  38 . The upper face of the transparent substrate  38  serves as a display surface  40  of the liquid crystal display device. Note that although the TFT substrate  12  and the counter substrate  14  each have an alignment film and a polarizer, they are omitted from the figure. 
     In the liquid crystal display device  10 , a region where a reflection section  30  is formed is referred to as a reflection region  42 , whereas a region where a TFT section  32  is formed is referred to as a TFT region  44 . In the reflection region, light entering from the display surface  40  is reflected by the reflection section  30 , and travels through the liquid crystal layer  18  and the counter substrate  14  so as to go out from the display surface  40 . Furthermore, the liquid crystal display device  10  has transmission regions which are formed in regions other than the reflection regions  42  and the TFT regions  44 . In the transmission regions  46 , light which is emitted from a light source in the liquid crystal display device  10  travels through the TFT substrate  12 , the liquid crystal layer  18 , and the counter substrate  14  so as to go out from the display surface  40 . 
     Note that, by providing a layer  31  made of transmissive resin or the like on the counter substrate  14  side above each reflection section  30  as shown in  FIG. 1 , it is possible to reduce the thickness of the liquid crystal layer  18  in the reflection region  42  to a half of the thickness of the liquid crystal layer  18  in the transmission region  46 . As a result, the optical path length can be made equal between the reflection region  42  and the transmission region  46 . Although  FIG. 1  illustrates the layer  31  as being formed between the counter electrode  34  and the CF layer  36 , the layer  31  may be formed on the face of the counter electrode  34  facing the liquid crystal layer  18 . 
       FIG. 2  is plan views more specifically showing the construction of the pixel regions and the reflection sections  30  of the liquid crystal display device  10 . 
       FIG. 2(   a ) is a plan view of a portion of the liquid crystal display device  10 , as seen from above the display surface  40 . As shown in the figure, a plurality of pixels  50  are disposed in a matrix shape in the liquid crystal display device  10 . The aforementioned reflection section  30  and TFT section  32  are formed in each pixel  50 , with a TFT being formed in the TFT section  32 . 
     In the border of the pixel  50 , source lines  52  extend along the column direction (up-down direction in the figure), and gate lines (also referred to as gate metal layers)  54  extend along the row direction (right-left direction in the figure). In the central portion of the pixel  50 , a Cs line  56  (Cs metal layer or metal layer  56 ) extends along the row direction. In the interlayer insulating layer  26  of the reflection region  30 , a contact hole  58  for connecting the pixel electrode  28  and the drain electrode of the TFT is formed. 
       FIG. 2(   b ) is a plan view schematically showing the construction of the reflection section  30  above the Cs metal layer  56 . In this figure, the contact hole  58  is omitted from illustration. As will be described later with reference to  FIG. 3 , the reflection section  30  includes a gate insulating layer  61  formed on the Cs metal layer  56 , a semiconductor layer  62  formed on the gate insulating layer  61 , and a reflective layer  63  formed on the semiconductor layer  62 . 
     As shown in the figure, a plurality of protrusions and recesses  68  are provided on the surface of the reflective layer  63 . Although 18 recesses  68  and 11 protrusions  67  are illustrated herein for ease of understanding the construction, more recesses  68  may actually be formed. The plurality of recesses  68  are formed so as to conform to the shapes of the apertures (or recesses)  65  in the Cs metal layer  56 , whereas the protrusion  67  are formed so as to conform to the shapes of the semiconductor layer  62 , which is formed in island shapes. 
     The Cs metal layer  56  may be formed in island shapes, and protrusions may be formed so as to conform to their shapes, instead of apertures (or recesses)  65 . Apertures (or recesses) may be formed in a semiconductor layer  62  which is formed so as to cover the reflection section  30 , and recesses may be formed so as to conform to their shapes, instead of protrusions  67 . In the present specification, any recess  68  or a protrusion replacing it will be referred to as a first recess or protrusion, and any protrusion  67  or a recess replacing it will be referred to as a second recess or protrusion. 
     The recesses  68  (or first recesses or protrusions) and the protrusions  67  (or second recesses or protrusions) are both randomly disposed. However, the protrusions  67  and the recesses  68  do not need to be perfectly randomly disposed, but may be randomly disposed in portions of the surface of the reflective layer  63 . Moreover, a layout lacking symmetry or an anisotropic layout may be adopted. 
     In either case, a plurality of pairs (first pairs) of recesses  68  adjoining along a direction (first direction) include two pairs whose intervals between recesses  68  are different from each other. Moreover, a plurality of pairs (second pairs) of protrusions  67  adjoining along a direction (second direction) include two pairs whose intervals between protrusions  67  are different from each other. 
     Moreover, a plurality of pairs (third pairs) of recesses  68  adjoining along a direction (third direction) which is different from the first direction may include two pairs whose intervals between recesses  68  are different from each other, and a plurality of pairs (fourth pairs) of protrusions  67  adjoining along a direction (fourth direction) which is different from the second direction may include two pairs whose intervals between protrusions  67  are different from each other. With such layout methods, it becomes possible to reduce occurrence of moiré or coloration due to interference of reflected light. 
     Next, with reference to  FIG. 3 , the construction of the reflection section  30  and the TFT section  32  will be described more specifically. 
       FIG. 3(   a ) shows a cross section of the reflection section  30  (a cross section of a portion shown by arrow B in  FIG. 2(   b )). As shown in the figure, in the reflection section  30 , the Cs metal layer (metal layer)  56 , the gate insulating layer (insulating layer)  61 , the semiconductor layer  62 , and the reflective layer  63  are stacked. The semiconductor layer  62  is composed of an intrinsic amorphous silicon layer (Si(i) layer) and an n+ amorphous silicon layer (Si(n+) layer) which is doped with phosphorus, for example. 
     The Cs metal layer  56  has an aperture  65 , such that a portion of the semiconductor layer  62 , which is formed in an island shape, is located inside the aperture  65 . A recess  68  is formed on the surface of the reflective layer  63  above the aperture  65 , whereas a protrusion  67  is formed on the surface of the reflective layer  63  above the semiconductor layer  62 . Moreover, the portion of the surface of the reflective layer  63  where no underlying semiconductor layer is formed becomes a recess  69 . Level differences are formed in the reflective layer  63  on the semiconductor layer  62  inside the recess  68 . 
     The recess  68  is formed by the gate insulating layer  61 , the semiconductor layer  62 , and the reflective layer  63  being formed above the aperture  65  of the Cs metal layer  56 , whereby the reflective layer  63  becomes dented. On the other hand, the protrusion  67  is created by the reflective layer  63  being formed on the semiconductor layer  62 , whereby the reflective layer  63  protrudes. Note that, a recess (dent) may be formed in the Cs metal layer  56 , instead of an aperture  65 . In that case, the recess  68  is to be formed in accordance with that recess of the Cs metal layer. 
     By adding a level difference to the side face of the aperture  65  of the Cs metal layer  56 , a level difference may be introduced to the slope of the recess  68 . Moreover, by adding a level difference to the side face of the semiconductor layer  62 , a level difference may be introduced to the slope of the protrusion  67 . 
       FIG. 3(   b ) is a diagram showing the construction of the gate metal layer (metal layer)  54 , the gate insulating layer  61 , the semiconductor layer  62 , and the reflective layer  63  in the TFT section  32 , and is a cross-sectional view of a portion at arrow A in  FIG. 2(   a ). The gate metal layer  54  in the TFT section  32  is formed concurrently with and from the same member as the Cs metal layer  56  in the reflection section  30 . Similarly, the gate insulating layer  61 , the semiconductor layer  62 , and the reflective layer  63  in the TFT section  32  are formed concurrently with and from the same members as, respectively, the gate insulating layer  61 , the semiconductor layer  62 , and the reflective layer  63  in the reflection section  30 . The reflective layer  63  is connected to the drain electrode of the TFT. 
       FIG. 4  is cross-sectional views for structural comparison between the reflection section  30  of Embodiment 1 and the reflection section of the conventional liquid crystal display device shown in  FIG. 10 .  FIG. 4(   a ) schematically shows the structure of the reflection section  30  of Embodiment 1, and  FIG. 4(   b ) schematically shows the structure of the reflection section of the conventional liquid crystal display device. Note that, in these figures, for simplicity, the slopes of each layer of the reflection section  30  and the slopes of each layer of the conventional liquid crystal display device are illustrated as vertical planes, and the corner portions of each level difference (portions shown by dotted circles in the figure) are illustrated as making perpendicular turns. 
     As shown in these figures, on the surface of the reflective layer  63  in the reflection section  30  of Embodiment 1, a total of eight corner portions are formed by one recess  68  and one protrusion  67 . On the other hand, in the conventional liquid crystal display device, only four corner portions are formed in one recess of the reflection section. 
     Although these corner portions are illustrated as being perpendicular in  FIG. 4 , in an actual corner portion, as shown in  FIG. 4(   c ), a face having angles which are larger than 20 degrees (exemplified as 30 degrees in this figure) with respect to the substrate is continuously formed from a plane (with an angle of 0 degrees) which is parallel to the substrate. Therefore, by forming more recesses in the reflection section, it becomes possible to form more faces (effective reflection surfaces) whose angle with respect to the substrate is 20 degrees or less on the surface of the reflective layer. 
     Moreover, since the effective reflection surfaces that are formed in a corner portion have various tilting angles which are different from one another, the reflected light will not travel in one fixed direction. Therefore, by forming more recesses, it becomes possible to obtain more reflected light which spans a broad range. Moreover, by increasing the number of recesses and ensuring that the tilting angle of the side face of any recess is 20 degrees or less, more reflected light which spans an even broader range can be obtained. 
     As shown in  FIGS. 4(   a ) and ( b ), more recesses and protrusions than in the conventional liquid crystal display device are formed in the reflection section  30  of Embodiment 1. Since more corner portions are therefore formed, it is possible to form more effective reflection surfaces on the surface of the reflective layer  63 , whereby more light can be reflected toward the display surface across a broad range. Moreover, the recess  68  and the protrusion  67  are formed in accordance with the shapes to which the Cs metal layer  56  and the semiconductor layer  62  are shaped. Therefore, the shapes, depths, and the slope tilting angles of the recess and protrusion can be easily adjusted during the shaping of the Cs metal layer  56  and the semiconductor layer  62 . 
     Moreover, the reflective layer  63  which is located inside the recess  68  in Embodiment 1 is formed above the gate insulating layer  61 , or above the gate insulating layer  61  and the semiconductor layer  62 . On the other hand, in the conventional liquid crystal display device, the reflective layer inside the recess is directly formed on the glass substrate, via neither the gate insulating layer nor the semiconductor layer. Therefore, the bottom face of the recess  68  of Embodiment 1 is formed so as to be shallower than the bottom face of a recess of the conventional liquid crystal display device. As a result, incident light can be reflected more effectively across a broad range. 
     In the conventional liquid crystal display device, the bottom face of a recess is formed at a deep position, so that the tilting angle of the recess inner surface is large, which makes it difficult to form a large number of effective reflection surfaces having a tilt of 20 degrees or less within the recess. Moreover, since this recess is formed by forming the gate layer  102 , the gate insulating layer  104 , and the semiconductor layer  106 , and thereafter altogether removing these layers, it has been difficult to increase the effective reflection surface by controlling the tilting angle of the recess inner surface. 
     Moreover, in the display device of the present embodiment, a recess  68  and a protrusion  67  are formed in accordance with the shapes of the Cs metal layer  56  and the semiconductor layer  62 , and therefore the position, size, and shape of the recess  68  and the protrusion  67  can be adjusted when stacking these layers. As a result, the tilt of the slopes of the recess  68  and the protrusion  67  can be controlled, whereby a larger number of effective reflection surfaces with a tilt or 20 degrees or less can be formed, thus allowing more light to be reflected toward the display surface. 
     Furthermore, in the liquid crystal display device of the present embodiment, as shown in  FIG. 1 , the faces of the interlayer insulating layer  26  and the pixel electrode  28  that are on the liquid crystal layer  18  side are formed flat without conforming to the shapes of the recesses  68  and the protrusions  67  of the reflective layer  63 , similarly to the face of the counter electrode  34  that is on the liquid crystal layer  18  side. Therefore, as compared to the conventional transflective-type liquid crystal display device shown in  FIG. 11 , the electric field which is formed across the liquid crystal layer  18  becomes uniform, thus making it possible to uniformly control the orientation of the liquid crystal of the reflection region  42  in a desired direction. 
     Moreover, since no level differences are formed in the pixel electrode  28  near the ends of the reflection section  30 , the liquid crystal orientation is not disturbed. As a result, according to the present embodiment, a liquid crystal display device can be provided which has a high transmittance and excellent viewing angle characteristics, with little display unevenness. 
     Next, a production method for the TFT substrate  12  will be described with reference to  FIG. 5  and  FIG. 6 .  FIG. 5  is plan views showing a production process, in the reflection region  42 , for the TFT substrate  12 ; and  FIG. 6  is cross-sectional views showing a production process, in the reflection region  42 , for the TFT substrate  12  (a portion shown at arrow B in  FIG. 2(   b )). 
     As shown in  FIG. 5(   a ) and  FIG. 6(   a ), first, by a method such as sputtering, a thin metal film of Al (aluminum) is formed on the transparent substrate  22  having been cleaned. Other than Al, this thin metal film may be formed by using Ti (titanium), Cr (chromium), Mo (molybdenum), Ta (tantalum), W (tungsten), or an alloy thereof, etc., or formed from a multilayer body of a layer of such materials and a nitride film. 
     Thereafter, a resist film is formed on the thin metal film, and after forming a resist pattern through an exposure-development step, a dry or wet etching is performed to form the Cs metal layer (metal layer)  56  having the apertures  65 . The thickness of the Cs metal layer  56  is  50  to 1000 nm, for example. Note that, although the apertures  65  are illustrated as being formed in the Cs metal layer  56 , a projecting shape of Cs metal layer  56  (or an island-shaped layer) may be formed at the position of each aperture, by using a resist pattern in which the light shielding portions and the transmitting portions are inverted. In this step, the gate line (gate metal layer)  54  shown in  FIG. 2(   a ) and the gate metal layer  54  of the TFT section  32  shown in  FIG. 3(   a ) are also formed concurrently from the same metal. 
     Next, as shown in  FIG. 5(   b ) and  FIG. 6(   b ), by using P-CVD technique and a gaseous mixture of SiH 4 , NH 3 , and N 2 , the gate insulating layer  61  composed of SiN (silicon nitride) is formed across the entire substrate surface. The gate insulating layer  61  may also be composed of SiO 2  (silicon oxide), Ta 2 O 5  (tantalum oxide), Al 2 O 3  (aluminum oxide), or the like. The thickness of the gate insulating layer  61  is 100 to 600 nm, for example. In this step, the gate insulating layer  61  of the TFT section  32  shown in  FIG. 3(   b ) is also formed concurrently. 
     Next, on the gate insulating layer  61 , an amorphous silicon (a-Si) film and an n + a-Si film obtained by doping amorphous silicon with phosphorus (P) are formed. The thickness of the a-Si film is 30 to 300 nm. The thickness of the n + a-Si film is 20 to 100 nm. Thereafter, these films are shaped by photolithography technique, whereby the semiconductor layer  62  is formed in island shapes. Recess (dents) or apertures may be formed in the semiconductor layer  62  by using a resist pattern in which the light shielding portions and the transmitting portions are inverted. In this step, the semiconductor layer  62  of the TFT section  32  shown in  FIG. 3(   b ) is also formed concurrently. 
     Next, as shown in  FIG. 5(   c ) and  FIG. 6(   c ), a thin metal film of Al or the like is formed across the entire substrate surface by sputtering technique or the like, thus forming the reflective layer  63 . For the thin metal film, the materials which are mentioned above as materials for the Cs metal layer  56  may be used. The thickness of the reflective layer  63  is 30 to 1000 nm or less. 
     At this time, the recess  68  is formed on the surface of the reflective layer  63  above each aperture  65  in the Cs metal layer  56 , and the protrusion  67  is formed on the surface of the reflective layer  63  above the semiconductor layer  62 . In this step, the reflective layer  63  of the TFT section  32  shown in  FIG. 3(   b ) is also formed concurrently, and in the TFT section  32 , the reflective layer  63  forms a source electrode and a drain electrode of the TFT. Also at this time, the source line  52  in  FIG. 2(   a ) is also formed as a portion of the reflective layer  63 . 
     Next, as shown in  FIG. 5(   d ) and  FIG. 6(   d ), a photosensitive acrylic resin is applied by spin-coating, whereby the interlayer insulating layer (interlayer resin layer)  26  is formed. The thickness of the interlayer insulating layer  26  is 0.3 to 5 μm. Although a thin film such as SiN x  or SiO 2  may be formed by P-CVD technique as a protection film between the reflective layer  63  and the interlayer insulating layer  26 , such is omitted from the figure. The thickness of the protection film is 50 to 1000 nm. The interlayer insulating layer  26  and the protection film are formed not only on the reflection region  42 , but also on the entire upper surface of the transparent substrate including the TFT region  44 . Thereafter, through a development process using an exposure apparatus, a contact hole  58  is formed near the center of the reflection section  30 . 
     Next, as shown in  FIG. 5(   e ) and  FIG. 6(   e ), a transparent electrode film of ITO, IZO, or the like is formed on the interlayer insulating layer  26  by sputtering technique or the like, and this transparent electrode film is subjected to pattern shaping by photolithography technique, whereby the pixel electrode  28  is formed. The pixel electrode  28  is formed not only on the reflection region  42  but also on the entire upper surface of the pixel including the TFT region  44 . 
     In the reflection region  42 , the pixel electrode  28  is formed above the interlayer insulating layer  26  and the contact hole  58 , such that the metal member of the pixel electrode  28  is in contact with the reflective layer  63  via the contact hole  58 . As a result, the drain electrode of the TFT in the TFT section  32  is electrically connected to the pixel electrode  28  via the contact hole  58 . In the above step, the upper face of the interlayer insulating layer  26  and the surface of the pixel electrode  28  are formed fiat without conforming to the shapes of the recesses  68  and the protrusions  67  of the reflective layer  63 . 
     Preferably, as many recesses  68  and protrusions  67  as possible are formed on the reflective layer  63 . Therefore, it is preferable that as many apertures in the Cs metal layer  56  and island shapes of semiconductor layer  62  as possible are formed on the reflection surface, within the limitations of the masks and photoexposure during the production step. The preferable maximum width of each aperture in the Cs metal layer  56  and the semiconductor layer  62  is 2 to 17 μm. 
     According to the present embodiment, it is possible to provide a liquid crystal display device which is capable of performing high-quality displaying with a high luminance, in which reflected light is efficiently utilized and moiré and coloration due to interference of reflected light is reduced. 
     Embodiment 2 
     Hereinafter, a second embodiment of the liquid crystal display device according to the present invention will be described. Constituent elements which are identical to the constituent elements of Embodiment 1 are denoted by like reference numerals, and the descriptions thereof are omitted. 
     The liquid crystal display device of the present embodiment basically has the same construction as that of the liquid crystal display device  10  of Embodiment 1 described above, except only for the layout of the recesses  68  and the protrusions  67  which are formed on the reflection section  30 . Therefore, the layout of the recesses  68  and the protrusions will be mainly described below, while omitting the descriptions of any other portions. 
       FIG. 7  is a plan view schematically showing the reflection section  30  of the liquid crystal display device according to Embodiment 2, which corresponds to  FIG. 2(   b ) showing the reflection section  30  of Embodiment 1. On the surface of the reflective layer  63  in the reflection section  30 , as shown in the figure, a plurality of protrusions  67  and recesses  68  are formed. Similarly to Example 1, the Cs metal layer  56  may be formed in island shapes, and protrusions may be formed so as to conform to their shapes, instead of apertures (or recesses)  65 . Apertures (or recesses) may be formed in the semiconductor layer  62 , and recesses may be formed so as to conform to their shapes, instead of protrusions  67 . 
     As shown in the figure, recesses  68  (or first recesses or protrusions) are disposed at equal intervals along the vertical direction and along the lateral direction, whereas the protrusions  67  (or second recesses or protrusions) are randomly disposed similarly to Embodiment 1. Note that the protrusions  67  do not need to be perfectly randomly disposed, but may be randomly disposed in portions of the surface of the reflective layer  63 . Moreover, a layout lacking symmetry or an anisotropic layout may be adopted. 
     In either case, a plurality of pairs (second pairs) of protrusions  67  adjoining along a direction (second direction) include two pairs whose intervals between protrusions  67  are different from each other. Moreover, a plurality of pairs (fourth pairs) of protrusions  67  adjoining along a direction (fourth direction) which is different from the second direction may include two pairs whose intervals between protrusions  67  are different from each other. With such layout methods, it becomes possible to reduce occurrence of moiré or coloration due to interference of reflected light. 
     Embodiment 3 
     Hereinafter, a third embodiment of the liquid crystal display device according to the present invention will be described. Constituent elements which are identical to the constituent elements of Embodiment 1 are denoted by like reference numerals, and the descriptions thereof are omitted. 
     The liquid crystal display device of the present embodiment basically has the same construction as that of the liquid crystal display device  10  of Embodiment 1 described above, except only for the layout of the recesses  68  and the protrusions  67  which are formed on the reflection section  30 . Therefore, the layout of the recesses  68  and the protrusions will be mainly described below, while omitting the descriptions of any other portions. 
       FIG. 8  is a plan view schematically showing the reflection section  30  of the liquid crystal display device of Embodiment 3, which corresponds to  FIG. 2(   b ) showing the reflection section  30  of Embodiment 1. On the surface of the reflective layer  63  in the reflection section  30 , as shown in the figure, a plurality of protrusions  67  and recesses  68  are formed. Similarly to Example 1, the Cs metal layer  56  may be formed in island shapes, and protrusions may be formed so as to conform to their shapes, instead of apertures (or recesses)  65 . Aperture (or recesses) may be formed in the semiconductor layer  62 , and recesses may be formed so as to conform to their shapes, instead of protrusions  67 . 
     As shown in the figure, the recesses  68  (or first recesses or protrusions) are randomly disposed similarly to Embodiment 1, whereas the protrusions  67  (or second recesses or protrusions) are disposed at equal intervals along the vertical direction and along the lateral direction. Note that the recesses  68  do not need to be perfectly randomly disposed, but may be randomly disposed in portions of the surface of the reflective layer  63 . Moreover, a layout lacking symmetry or an anisotropic layout may be adopted. 
     In either case, a plurality of pairs (first pairs) of recesses  68  adjoining along a direction (first direction) include two pairs whose intervals between recesses  68  are different from each other. Moreover, a plurality of pairs (third pairs) of recesses  68  adjoining along a direction (third direction) which is different from the first direction may include two pairs whose intervals between recesses  68  are different from each other. With such layout methods, it becomes possible to reduce occurrence of moiré or coloration due to interference of reflected light. 
     Embodiment 4 
     Hereinafter, with reference to the drawings, a fourth embodiment of the liquid crystal display device according to the present invention will be described. Constituent elements which are identical to the constituent elements of Embodiments 1 to 3 are denoted by like reference numerals, and the descriptions thereof are omitted. 
       FIG. 9  is a diagram schematically showing a cross-sectional shape of the liquid crystal display device of the present embodiment. This liquid crystal display device is based on the liquid crystal display devices of Embodiments 1 to 3 from which the interlayer insulating layer  26  is excluded, and is identical to the liquid crystal display devices of Embodiments 1 to 3 except for the points discussed below. Note that, in  FIG. 9 , the detailed structure of the counter substrate  14  and the TFT section  32  are omitted from illustration. 
     As shown in the figure, in Embodiment 4, no interlayer insulating layer  26  is formed, and therefore the pixel electrode  28  is formed upon the reflective layer  63  in the reflection section  30  and the TFT section  32 , via an insulative film not shown. The structure and production method for the reflection section  30  and the TFT section  32  are the same as those which were described in Embodiment 1 except that the interlayer insulating layer  26  is eliminated. The pixel layout and wiring structure in the display device are also similar to what is shown in  FIG. 2(   a ). Also with this construction, similarly to Embodiments 1 to 3, the effective reflection surface of the reflective layer  63  is expanded in area, so that more light can be reflected toward the display surface. 
     Embodiments 1 to 4 illustrate that the apertures  65  in the Cs metal layer  56 , the semiconductor layer  62 , the protrusions  67 , and the recesses  68  are circular, but they may be formed into ellipses, polygons such as triangles or rectangles, or formed into various shapes such as recesses or protrusions with sawtoothed edges, or combinations thereof. 
     As has been illustrated by the above Embodiments, a liquid crystal display device according to the present invention includes a large number of level differences and corner portions on the surface of a reflective layer, as well as a large number of slopes with a tilting angle of 20 degrees or less, and therefore acquires reflection regions with broad effective reflection surfaces and excellent scattering characteristics. Moreover, since the shape of the reflective layer surface is not likely to have symmetry, occurrence of moiré and coloration due to interference of reflected light can be reduced or prevented. Thus, a liquid crystal display device having a high brightness and being capable of clear displaying can be provided. 
     Moreover, since the level differences and corner portions on the reflection surface are formed in accordance with the shapes of the Cs metal layer and the semiconductor layer just when they are shaped, reflection regions having excellent reflection characteristics can be easily obtained without increasing the production steps. Furthermore, since the liquid crystal display device according to the present invention is formed by the above-described production method, it can be produced with the same material and the same steps as those of a transmission-type liquid crystal display device. Therefore, a high-quality liquid crystal display device can be provided inexpensively. 
     Furthermore, according to the present invention, the face of a pixel electrode facing the liquid crystal layer is formed flat, similarly to its face on the counter electrode side, and no level difference is formed in the pixel electrode near the end of the reflection section, thus making it possible to uniformly control the orientation of liquid crystal in a desired direction. Therefore, it is possible to provide a liquid crystal display device which has a high transmittance, excellent viewing angle characteristics, and little display unevenness. 
     The liquid crystal display device according to the present invention encompasses display apparatuses, television sets, mobile phones, etc., in which a liquid crystal panel is utilized. Although the present embodiment employs a transflective-type liquid crystal display device as an example, a reflection-type liquid crystal display device or the like having a configuration similar to the aforementioned reflection section is also encompassed as an embodiment of the present invention. 
     INDUSTRIAL APPLICABILITY 
     According to the present invention, a transflective-type liquid crystal display device and a reflection-type liquid crystal display device having a high image quality can be provide inexpensively. Liquid crystal display devices according to present invention are suitably used for various liquid crystal display devices, and are suitably used for transflective-type and reflection-type liquid crystal display devices which perform display by utilizing reflected light, e.g., mobile phones, onboard display devices such as car navigation systems, display devices of ATMs and vending machines, etc., portable display devices, laptop PCs, and the like.