Patent Publication Number: US-2006007384-A1

Title: Liquid crystal display device and electronic apparatus

Description:
BACKGROUND OF THE INVENTION  
      1. Technical Field  
      The present invention relates to a liquid crystal display device and an electronic apparatus, and, more particularly, to a technology which provides a display having a wide viewing angle range and a high contrast in a liquid crystal display device using homeotropic liquid crystal.  
      2. Related Art  
      A transflective liquid crystal display device having a reflection mode and a transmission mode is known as a liquid crystal display device. A transflective liquid crystal display device of a type in which a liquid crystal layer is disposed between an upper substrate and a lower substrate and a reflective film (a metallic film, such as an aluminum film, having a window for transmitting light) is disposed at the inner surface of the lower substrate and functions as a transflective plate has been proposed. In this case, in the reflection mode, incident outside light from the upper substrate passes through the liquid crystal layer, is then reflected by the reflective film, then passes through the liquid crystal layer again, and then exits from the upper substrate to the outside, as a result of which the light is used for a displaying operation. In contrast, in the transmission mode, incident light emitted from a backlight and traveling to the lower substrate passes through the liquid crystal layer from the window of the reflective film, and then exists from the upper substrate to the outside, as a result of which the light is used for a displaying operation. Therefore, of a reflective film formation area, an area where the window is formed corresponds to a transmissive display area and the area where the window is not formed corresponds to a reflective display area.  
      However, the related transflective liquid crystal display device has a problem in that the viewing angle is narrow in transmissive display. This is because optical design freedom is small due to a restriction that reflective display must be performed with only one polarizer at an observer side since the transflective plate is disposed at the inner surface of a liquid crystal cell so as to prevent parallax. To overcome this problem, Jisaki et al. discloses a novel liquid crystal display device using homeotropic liquid crystal in Japanese Unexamined Patent Application Publication No. 2002-350853 and “Development of transflective LCD for high contrast and wide viewing angle by using homeotropic alignment,” Asia Display/IDW &#39;01, pp. 133-136(2001). The features are as follows: 
          (1) A vertical alignment (VA) mode in which liquid crystal having a negative dielectric anisotropy are aligned vertically with respect to a substrate and tilted by application of a voltage is used;     (2) A multi-gap structure in which the thickness of a portion of a liquid crystal layer at a transmissive display area and the thickness of a portion of the liquid crystal layer at a reflective display area (cell gaps) are different is used (refer to, for example, Japanese Unexamined Patent Application Publication No. 11-242226; and     (3) The transmissive display area has a regular octagonal shape and a protrusion is disposed at the center of the transmissive display area on an opposing substrate so that the liquid crystal is tilted in all directions in this area. In other words, an “alignment segmentation structure” is used.        

      As described above, in the liquid crystal display device using homeotropic liquid crystal (having a negative dielectric anisotropy) which is subjected to alignment segmentation alignment without rubbing, it is necessary to control the direction in which the liquid crystal molecules are tilted as a result of distorting an electrical field in a pixel area by forming an opening in a portion of an electrode in the pixel area or a dielectric protrusion on a portion of the electrode in the pixel area. If the liquid crystal alignment is not sufficiently controlled, the liquid crystal molecules are tilted in random directions while domains of certain sizes are maintained in a plane. In such a state, an area having a different viewing angle property is formed in a portion of the display area. As a result, the display appears uneven.  
      In the related liquid crystal display device, spherical spacers used for maintaining the thickness of the liquid crystal layer are randomly disposed in any location in the liquid crystal layer. Therefore, the liquid crystal is brought out of alignment, causing the display to appear uneven. When one pixel area is defined by a pixel electrode, an area between the pixel electrode and an adjacent pixel electrode, a switching element connected to the pixel electrode, and a metallic wire connected to the switching element, it is desirable that, in the homeotropic liquid crystal in an alignment segmentation structure, any effect on the alignment of the liquid crystal in a pixel electrode plane be minimized by forming a columnar space (primarily formed of resin) at the area between the adjacent pixels. In addition, when the columnar spacer is disposed so as to overlap the switching element, it is possible to reduce the electrical field generated from the switching element, thereby preventing the liquid crystal from becoming misaligned.  
      Since bubbles tend to be formed in a liquid crystal panel as the number of columnar spaces per unit area increases, the columnar spaces cannot be disposed in all pixel areas in a plane, particularly, in a high-definition liquid crystal display device. In this case, a pixel area having a columnar space disposed thereat and the other pixel areas not having columnar spaces disposed thereat produce different liquid crystal alignments, thereby giving rise to differences in display characteristics in a plane. In addition, for a liquid crystal display device including switching elements, the liquid crystal is brought out of alignment by an electrical field generated from the switching elements in pixel areas where columnar spaces are not disposed. This deteriorates display quality.  
     SUMMARY  
      An advantage of the invention is that it provides a highly reliable liquid crystal display device which provides a higher display quality and a high definition.  
      A liquid crystal display device according to a first aspect of the invention comprises a pair of opposing substrates and a liquid crystal layer disposed between the pair of substrates, the liquid crystal layer being formed of liquid crystal which has a negative dielectric anisotropy and which is vertically aligned in an initial alignment state. At least one columnar spacer is disposed at at least one of the substrates for separating the opposing substrates. Pixel areas are disposed in a matrix at either one of the pair of substrates in a plane thereof, each pixel area including a pixel electrode, a gap between the pixel electrode and an adjacent pixel electrode, a switching element connected to the pixel electrode, and a metallic line connected to the switching element. The spacer is disposed in at least one of the gaps or so as to overlap at least one of the switching elements in at least one of the pixel areas. At least one first protrusion having a height that is less than the height of the spacer is disposed in at least one of the pixel areas where the spacer is not provided. The location where the spacer is disposed and the location where the first protrusion is disposed in the respective pixel areas are in correspondence with each other.  
      According to the first aspect of the invention, the term “pixel area” does not refer to an area including only a pixel electrode. It refers to an area also including a signal line and an active element associated with one pixel electrode and a portion between the pixel electrode and an adjacent pixel electrode.  
      In this structure, since the number of columnar spacers can be reduced to the minimum required by disposing at least one columnar spacer only at at least one of the predetermined pixel areas in the display surface of the liquid crystal display device, it is possible to prevent bubbles from being produced in the liquid crystal layer particularly, at a low temperature. Hitherto, a difference had occurred between the liquid crystal alignment state of a pixel area where a columnar spacer is not disposed and that of a pixel area where a columnar spacer is disposed due to the influence of the columnar spacer, thereby reducing the display quality.  
      According to the structure, in the pixel area or areas where a columnar spacer or columnar spacers are not disposed, instead of the columnar spacer or columnar spacers, a protrusion or protrusions formed of, for example, resin is/are disposed substantially at a location or locations in correspondence with where the columnar spacer or columnar spacers are disposed in order to control the liquid crystal alignment. By making similar the influence of the columnar spacer or columnar spacers on the liquid crystal alignment and the influence of the first protrusion or first protrusions on the liquid crystal alignment, it is possible to reduce the difference between the liquid crystal alignment states at the pixel areas regardless of whether or not a columnar spacer is provided. Therefore, a high quality, highly reliable liquid crystal display device can be provided.  
      It is preferable that an area of an area where the spacer is disposed and an area of an area where the first protrusion is disposed be substantially the same.  
      The effect of the protrusion or protrusions on liquid crystal alignment control is greatly related to the area or areas where the protrusion or the protrusions are formed. The aforementioned structure makes it possible to further reduce the difference between the influence of the columnar spacer or columnar spacers on the liquid crystal alignment and the influence of the first protrusion or first protrusions on the liquid crystal alignment.  
      It is preferable that the spacer and the first protrusion be disposed on the same substrate.  
      The aforementioned structure makes it possible to make similar the influence of the columnar spacer or columnar spacers on the liquid crystal alignment and the influence of the first protrusion or first protrusions on the liquid crystal alignment.  
      A plurality of the columnar spacers and the first protrusions may be disposed in one pixel area.  
      It is desirable that the columnar spacer or columnar spacers and the first protrusion or first protrusions be formed so as to overlap the switching elements in plan view. It is more desirable to directly dispose the columnar spacer or columnar spacers and the first protrusion or first protrusions on the switching elements.  
      In a structure in which switching elements are provided, distortion of an electrical field generated from the switching elements destroys the symmetry of the electrical field in the liquid crystal layer and is thus a major cause of disturbing the liquid crystal alignment. By disposing the columnar spacer or columnar spacers and the first protrusion or first protrusions so as to overlap the switching elements, it is possible to reduce the distortion of the electrical field. The aforementioned structure makes it possible to reduce any disturbance in the liquid crystal alignment, such as disclination, caused by the switching elements, thereby providing a high display quality. In addition, since the switching element or switching elements are covered with the first protrusion or first protrusions formed of, for example, resin, the first protrusion or first protrusions act as protective layers for the switching element or switching elements, thereby preventing the switching element or switching elements from becoming damaged due to external pressure. Therefore, it is possible to provide a highly reliable liquid crystal display device which withstands pressure very well and which generates little bubbles.  
      Second protrusions may be disposed at areas other than the areas where the first protrusions are disposed at the pixel areas, that is, on pixel electrodes or metallic lines connected to switching elements. Unlike the first protrusion or first protrusions disposed only at the pixel area or pixel areas where columnar spacer or columnar spacers are not disposed, the second protrusions having shapes that are similar to those of the first protrusion or first protrusions are disposed at all of the pixel areas used for a displaying operation regardless of whether or not the columnar spacer or columnar spacers or the first protrusion or first protrusions are disposed. The first and second protrusions are formed of the same material and have the same height. When the first and second protrusions are formed on the same substrate, it is desirable that the first and second protrusions be formed by the same process.  
      The second protrusions are formed for controlling liquid crystal alignment. Forming the first and second protrusions at the same time can reduce cost burden.  
      It is desirable that the second protrusions be disposed so as to overlap the metallic lines, such as scanning lines or signal lines, connected to the switching elements. A relatively high voltage applied to the metallic lines causes the electrical field generated from the metallic lines to symmetrically distort the electrical field in the liquid crystal layer and thus to disturb the liquid crystal alignment. The aforementioned structure can reduce the distortion of the electrical field from the metallic lines by blocking the electrical field. Covering substantially the entire metallic lines with the protrusions makes it possible to maximally reduce the threshold distortion in the liquid crystal layer, or covering only portions of the metallic lines with the protrusions makes it possible to fix the location where disclination of the liquid crystal alignment occurs to a particular location.  
      The liquid crystal display device according to the first aspect may be such that the first protrusion/first protrusions or the first and second protrusions are provided, a transmissive display area and a reflective display area are provided in one pixel area, and a liquid crystal layer thickness adjusting layer for making the thickness of a portion of the liquid crystal layer at the reflective display area smaller than the thickness of a portion of the liquid crystal layer at the transmissive display area is disposed between the liquid crystal layer and at least one of the pair of substrates.  
      In the transflective liquid crystal display device comprising the liquid crystal layer thickness adjusting layer, the columnar space or columnar spaces are disposed so as to overlap the liquid crystal layer adjusting layer. The switching elements are frequently disposed at locations overlapping the liquid crystal layer thickness adjusting layer in plan view, as a result of which the height of a portion of the liquid crystal layer in the area where the switching elements are disposed is relatively small. Therefore, the switching elements tend to be damaged by external pressure, such as push pressure. In the structure according to the first aspect of the invention, the first protrusion or first protrusions are provided, so that damage to the switching element or switching elements by external pressure occurs less frequently.  
      A electronic apparatus according to a second aspect of the invention comprises any one of the above-described liquid crystal display devices. Therefore, it is possible to provide at a low cost an electronic apparatus comprising a highly reliable display unit providing excellent display quality. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements, and wherein:  
       FIG. 1  is an equivalent circuit diagram of a liquid crystal display device according to a first embodiment of the invention;  
       FIG. 2  is a plan view of a dot structure of the liquid crystal display device;  
       FIG. 3A  is a schematic plan view of the main portion of the liquid crystal display device;  
       FIG. 3B  is a schematic sectional view of the main portion of the liquid crystal display device;  
       FIG. 4A  is a schematic plan view of the main portion of a liquid crystal display device according to a second embodiment of the invention;  
       FIG. 4B  is a schematic sectional view of the main portion of the liquid crystal display device according to the second embodiment of the invention;  
       FIG. 5A  is a schematic plan view of the main portion of a liquid crystal display device according to a third embodiment of the invention;  
       FIG. 5B  is a schematic sectional view of the main portion of the liquid crystal display device according to the third embodiment of the invention;  
       FIG. 6  is a perspective view of an example of an electronic apparatus in accordance with the invention. 
    
    
     DESCRIPTION OF THE EMBODIMENTS  
     First Embodiment  
      While referring to FIGS.  1  to  3 , a first embodiment of the invention will be described. In the figures, each layer and each member are shown with sizes large enough to be seen, so that each layer and each member are shown using different scales.  
      A liquid crystal display device of the first embodiment described below is an active matrix liquid crystal display device using thin film diodes (hereunder abbreviated as “TFDs”) as switching elements, and is, in particular, a transflective liquid crystal display device which can provide a reflective display and a transmissive display.  
       FIG. 1  shows an equivalent circuit for a liquid crystal display device  100  according to the embodiment. The liquid crystal display device  100  includes a scanning signal drive circuit  110  and a data signal drive circuit  120 . In the liquid crystal display device  100 , signal lines, that is, a plurality of scanning lines  13  and a plurality of data lines  9  intersecting the scanning lines  13  are provided, with the scanning lines  13  being driven by the scanning signal drive circuit  110  and the data lines  9  being driven by the data signal drive circuit  120 . In each pixel area  150 , a TFD element  40  and a liquid crystal display element  160  (liquid crystal layer) are connected in series between the associated scanning line  13  and data line  9 . Although, in  FIG. 1 , the TFD elements  40  are connected to the scanning lines  13  and the liquid crystal display elements  160  are connected to the data lines  9 , the TFD elements  40  may be connected to the data lines  9  and the liquid crystal display elements  160  may be connected to the scanning lines  13 .  
      Referring to  FIG. 2 , the planar structure (pixel structure) of electrodes in the liquid crystal display device  100  according to the embodiment will be described. As shown in  FIG. 2 , in the liquid crystal display device  100  according to the embodiment, pixel electrodes  31  which are rectangular in plan view and connected to the scanning lines  13  via the TFD elements  40  are disposed in a matrix, and common electrodes  9  opposing the pixel electrodes  31  perpendicularly to the plane of the figure are disposed in stripes. The common electrodes  9  comprise the data lines and intersect the scanning lines  13  in the form of stripes. In the embodiment, an area where the associated pixel electrode  31  is provided, an area between the associated pixel electrode  31  and an adjacent pixel electrode  31 , the associated TFD element  40  connected to the associated pixel electrode  31 , and the associated data line  9  connected to the associated TFD element  40  is defined as one dot area. The TFD elements  40  are provided in the respective dot areas disposed in a matrix, so that a displaying operation can be performed at each dot area.  
      Here, the TFD elements  40  are switching elements connected to the respective scanning lines  13  and pixel electrodes  31 . Each TFD element  40  has an MIM structure comprising a first conductive film whose main component is Ta, an insulating film formed on the surface of the first conductive film and whose main component is Ta 2 O 3 , and a second conductive film formed on the surface of the insulating film and whose main component is Cr. The first conductive films of the TFD elements  40  are connected to the scanning lines  13 , and the second conductive films of the TFD elements  40  are connected to the pixel electrodes  31 .  
      Referring to  FIGS. 3A and 3B , the pixel structure of the liquid crystal display device  100  according to the embodiment will be described.  FIG. 3A  is a plan view of the pixel structure of the liquid crystal display device  100 , and, more particularly, of the structure of the pixel electrodes  31 .  FIG. 3B  is a schematic sectional view taken along line  111 B-IIIB shown in  FIG. 3A . As shown in  FIG. 2 , the liquid crystal display device  100  according to the embodiment has dot areas including the respective pixel electrodes  31  disposed inwardly of the respective data lines  9 , the scanning lines  13 , etc. As shown in  FIG. 3 , in each dot area, one coloring layer for one of the three primary colors is disposed, so that pixel areas including respective coloring layers  22 B (blue),  22 G (green), and  22 R (red) are formed at three dot areas D 1 , D 2 , and D 3 . The portion defined by dotted lines in  FIG. 3  defines the pixel area  150  shown in  FIG. 1 . The pixel area  150  includes, for example, the associated pixel electrode  31 , TFD element  40 , data line  9 , and a columnar spacer or a protrusion associated with the data line  9 .  
      Referring to the sectional structure, as shown in  FIG. 3B , the liquid crystal display device  100  according to the embodiment comprises a pair of substrates  10  and  25  opposing each other via a rectangular frame-shaped sealant (not shown) and a liquid crystal layer  50  disposed between the pair of substrates  10  and  25 . The liquid crystal layer  50  comprises liquid crystal which is initially aligned vertically, that is, a liquid crystal material which has a negative dielectric anisotropy. In the embodiment, a panel according to the invention is formed by the substrates  10  and  25  opposing each other via the sealant, with the liquid crystal layer  50  being sealed in the panel so as to be surrounded by the substrates  10  and  25  and the sealant.  
      A substrate body  10 A of the lower substrate (opposing substrate) is formed of a light-transmissive material, such as quartz or glass. A reflective film  20  (metallic film formed of a metal having high reflectivity such as aluminum or silver) is formed on a part of the surface of the substrate via an insulating film  24 . A color filter  22  (the red coloring layer  22 R in  FIG. 3B ) is disposed on the area of the substrate where the reflective film  20  is not formed and the area of the substrate where the reflective film  20  is formed from thereabove. Here, the area where the reflective film  20  is formed is a reflective display area R, and the area where the reflective film  20  is not formed, that is, an opening  21  in the reflective film  20  is a transmissive display area T. Accordingly, the liquid crystal display device  100  according to the embodiment is a liquid crystal display device comprising the homeotropic liquid crystal layer  50  and is a transflective type which can provide a reflective display and a transmissive display.  
      A surface of the insulating film  24  formed on the substrate body  10 A has an bumpy portion  24   a , and a surface of the reflective film  20  is bumpy in accordance with the bumpy portion  24   a . Since reflected light is scattered by the bumpy surface, external glare is prevented from occurring, so that a display with a wide viewing angle range can be achieved. The insulating film  24  having the bumpy portion  24   a  is formed by, for example, patterning a resin resist and applying another layer of resin thereon. In addition, the resin resist subjected to the patterning may have its form adjusted by subjecting it to heat treatment.  
      The color filters  22  are formed at the reflective display area R and the transmissive display area T. Edges of the coloring layers forming the color filters  22  are surrounded by a black matrix BM formed of, for example, chromium. The black matrix BM forms the boundaries of the dot areas D 1 , D 2 , and D 3  (see  FIG. 3A ).  
      An insulating film  26  is further formed on the substrate body  10 A in correspondence with the location of the reflective display area R. The insulating film  26  is selectively formed at the reflective display area R so as to be disposed above the reflective film  20 . The formation of the insulating film  26  causes the thickness of a portion of the liquid crystal layer  50  at the reflective display area R and the thickness of a portion of the liquid crystal layer  50  at the transmissive display area T to be different. The insulating film  26  has a thickness of, for example, on the order of from 0.5 μm to 2.5 μm, and is formed of, for example, acrylic resin. Near the boundary between the reflective display area R and the transmissive display area T, the insulating film  26  has an inclined surface for continuously varying its thickness. The thickness of the liquid crystal layer  50  where the insulating film  26  is not provided is on the order of from 1 μm to 5 μm, so that the thickness of the portion of the liquid crystal layer  50  at the reflective display area R is approximately half of the thickness of the portion of the liquid crystal layer  50  at the transmissive display area T. Accordingly, the insulating film  26  functions as a liquid crystal layer thickness adjusting layer (liquid crystal layer thickness controlling layer) causing the thickness of the portion of the liquid crystal layer  50  at the reflective display area R and the thickness of the portion of the liquid crystal layer  50  at the transmissive display area T to be different by the thickness of the insulating film  26 .  
      The common electrodes  9 , formed of indium tin oxide (hereunder abbreviated as “ITO”), are formed in stripes on the insulating film  26  and the color filters  22  so as to extend perpendicularly to the plane of the figure. The common electrodes  9  are formed at respective dot areas disposed in a row perpendicular to the plane of the figure. Openings  29  for controlling liquid crystal alignment are formed in the common electrodes  9  at the transmissive display area and the reflective display area R. When these openings  29  are formed, an oblique electrical field is generated between the electrodes  9  and  31  at the opening area. In accordance with the oblique electrical field, the tilting direction of initially vertically aligned liquid crystal molecules based on voltage application is restricted, so that the alignment of the liquid crystal molecules can be controlled. In particular, since transverse electric field in the reflective display area is larger than that in the transmissive display area by an amount in correspondence with a smaller cell thickness, the restricting force on the alignment of the liquid crystal molecules is increased. The openings  29  in the common electrodes  9  are alternately formed in plan view on both sides of slits  32  (described later) in the pixel electrodes  31 . As a result, the tilting direction of liquid crystal molecules LC can be alternately restricted between the openings  29  and the slits  32 .  
      Although, in the embodiment, the reflective film  20  and the common electrodes  9  are separately formed, the reflective film (metallic film) may be used as portions of the common electrodes at the reflective display area R.  
      An alignment layer  37 , formed of, for example, polyimide, is formed on the common electrodes  9 . The alignment layer  37  acts as a vertical alignment layer for aligning the liquid crystal molecules vertically with respect to the plane of the layer, and is not subjected to an alignment operation such as rubbing.  
      In the upper substrate (element substrate)  25 , the pixel electrodes  31  (transparent conductive films formed of, for example, ITO) are disposed in a matrix on a surface of a substrate body  25 A (formed of a light-transmissive material such as glass or quartz) facing the liquid crystal layer. As in the lower substrate  10 , an alignment layer  33 , formed of, for example, polyimide subjected to a vertical alignment operation is formed so as to cover the pixel electrodes  31 .  
      One pixel electrode  31  is provided at each of the dot areas D 1  to D 3 . Voltages are separately applied to the respective dot areas D 1  to D 3  by the TFDs disposed at the respective dot areas. In the embodiment, a columnar spacer  51  formed of acrylic resin and used as a support along the height of the liquid crystal layer  50  is disposed so as to overlap the TFD element at the dot area D 1 . First protrusions  27  having a height that is less than the height of the columnar spacer  51  and having the substantially same shape as the columnar spacer  51  in plan view are disposed so as to overlap the TFD elements at the dot areas D 2  and D 3 . Each first protrusion  27  is formed of photoresist comprising novolac resin and can be subjected to patterning by photolithography techniques. The first protrusions  27  block the electrical field from the TFD elements in order to reduce differences between liquid crystal alignments at the dot areas, and protects the TFD elements at the dot areas D 2  and D 3  from external pressure. Although, in the embodiment, as regards the dot areas D 1  to D 3  for respective color filter colors, the columnar spacer  51  is disposed at the dot area D 1  and the first protrusions  27  are disposed at the dot areas D 2  and D 3 , they may be disposed independently of the order of the colors of the color filters or randomly. In addition, although in the embodiment, the columnar spacer  51  and the first protrusions  27  are disposed so as to overlap the TFD elements, they may be disposed at areas other than where the TFD elements are disposed. In this case, although the electrical field from the TFD elements cannot be blocked, this structure is effective in reducing the difference between the liquid crystal alignments at the dot areas. It is also effective in preventing damage to the TFD elements by push pressure because the opposing substrate  10  can be supported by the first protrusions  27 .  
      In the embodiment, second protrusions  28 , formed of the same material as the first protrusions, are selectively disposed at adjacent areas in the transmissive display area T of the scanning lines  13  of the dot areas D 1  to D 3 . The first protrusions are disposed only at the pixel areas where columnar spacers are not disposed, whereas the second protrusions are disposed at all of the pixel areas regardless of whether or not columnar spacers are provided. The second protrusions block the electrical field generated from the scanning lines. The liquid crystal molecules are vertically disposed with respect to the inclined surfaces of the second protrusions  28 . Selectively forming the second protrusions at the scanning lines makes it possible to fix the disclination to a particular location.  
      In the embodiment, each pixel electrode  31  comprises island-shaped portions (island-shaped portions  31   a  and  31   b  in  FIG. 3 ) and a connecting portion  39  electrically connecting the adjacent island-shaped portions  31   a  and  31   b . Each of the island-shaped portions  31   a  and  31   b  forms a sub-dot, so that one dot comprises divided sub-dots. Although the sub-dots (island-shaped portions  31   a  and  31   b ) have regular octagonal shapes in  FIG. 3A , they may be, for example, circular or polygonal. Each slit  32  is formed in a portion of its associated pixel electrode  31  (the portion excluding the associated connecting portion  39 ) so as to be disposed between the island-shaped portions  31   a  and  31   b . Each slit  32  is disposed near the center between the sub-dots (island-shaped portions  31   a  and  31   b ) and between the electrode openings  29  in the substrate body  10 A of the lower substrate  10  in plan view.  
      A retardation film  18  and a polarizer  19  are disposed at the outer surface of the lower substrate  10  (at a side opposite to the side where the liquid crystal layer  50  is sandwiched), and a retardation film  16  and a polarizer  17  are disposed at the outer surface of the upper substrate  25 , so that circularly polarized light can impinge upon the inner surfaces of the respective substrates facing the liquid crystal layer  50 . The retardation film  18  and the polarizer  19  and the retardation film  16  and the polarizer  17  form circularly polarizing units. The polarizers  17  and  19  are formed so as to pass only linearly polarized light having a polarization axis of a predetermined direction, and the retardation films  16  and  18  are λ/4 retardation films. Each circularly polarizing unit may comprise a combination of a polarizer, a λ/4 retardation film and a λ/2 retardation film (wide band circularly polarizing unit). In this case, it is possible to provide an achromatic color of a higher degree in a dark display. In addition, each circularly polarizing unit may comprise a combination of a polarizer, a λ/4 retardation film, a λ/2 retardation film, and a c plate (retardation film having an optical axis in the film thickness direction), so that a wider viewing angle range can be achieved. A backlight  15 , which is a light source for transmissive display, is disposed at the outer side of the polarizer  19  of the lower substrate  10 .  
      In the embodiment, the first protrusions  27  having substantially the same shape as the columnar spacer  51  in plan view are disposed so as to overlap the TFD elements at the pixel areas where columnar spacers  51  are not disposed, so that the difference between the liquid crystal alignments at the pixel areas is eliminated and the electrical field from the TFD elements is blocked in order to reduce symmetrical distortion of the electrical field in the liquid crystal layer. Therefore, it is possible to provide a liquid crystal display device providing a higher display quality. The liquid crystal display device is a transflective liquid crystal display device. In the transflective type, in order to reduce the influence of the electrical field from the TFD elements, the liquid crystal layer thickness adjusting layer  26  is formed at an area facing the TFD elements at the lower substrate  10 , as a result of which the TFD elements tend to become damaged by push pressure. In the embodiment, the first protrusions protect the TFD elements, so that a more reliable structure is provided.  
      The above-described liquid crystal display device  100  according to the embodiment can provide the following advantages.  
      In the liquid crystal display device  100  according to the embodiment, since the insulating film  26  is disposed at the reflective display area R, the thickness of the portion of the liquid crystal layer  50  at the reflective display area R is substantially half of the thickness of the portion of the liquid crystal layer  50  at the transmissive display area T, so that retardation contributing to reflective display and retardation contributing to transmissive display are substantially the same, as a result of which contrast is increased.  
      In the embodiment, since the oblique electrical field based on the inclined surfaces of the second protrusions  28  and the openings  29  and the slits  32  can regulate the tilting direction of the liquid crystal when a voltage is applied, for example, an after image resulting from disclination or a stain-like unevenness seen when observed obliquely is not easily produced, so that a high-quality display is provided.  
      In the embodiment, the columnar spacer  51  and the first protrusions  27  at the TFD elements reduce the difference between the liquid crystal alignments at the pixel areas regardless of whether or not any columnar spacers are provided. In addition, electrical field generated from the TFD elements is blocked in order to reduce disturbance to the liquid crystal alignments. Further, the first protrusions  27  cover and protect the TFD elements in order to prevent damage to the elements by push pressure. Therefore, it is possible to provide a more reliable liquid crystal display device providing a high display quality.  
     Second Embodiment  
      A second embodiment of the invention will be described with reference to  FIGS. 4A and 4B .  
       FIGS. 4A and 4B  are a plan view and a sectional view of a liquid crystal display device of the second embodiment, respectively, and are schematic views in correspondence with those of  FIGS. 3A and 3B  showing the first embodiment. Parts in the second embodiment corresponding to those in the first embodiment are given the same reference numerals.  
      A liquid crystal display device  200  according to the second embodiment is a transmissive liquid crystal display device which does not have a reflective display area. As shown in  FIG. 4A , the liquid crystal display device  200  has dot areas including respective pixel electrodes  31  disposed inwardly of data lines  9 , scanning lines  13 , etc. In each dot area, one coloring layer for one of the three primary colors is disposed, so that pixel areas including respective coloring layers  22 B (blue),  22 G (green), and  22 R (red) are formed at three dot areas D 1 , D 2 , and D 3 . Similarly, pixel areas including respective coloring layers  22 B (blue),  22 G (green), and  22 R (red) are formed at dot areas D 1 ′, D 2 ′, and D 3 ′ adjacent to these dot areas D 1 , D 2 , and D 3  in the transverse direction with respect to the plane of the figure.  
      Referring to the sectional structure, as shown in  FIG. 4B , the liquid crystal display device  200  according to the embodiment comprises a pair of substrates  10  and  25  opposing each other via a rectangular frame-shaped sealant (not shown) and a liquid crystal layer  50  disposed between the pair of substrates  10  and  25 . The liquid crystal layer  50  comprises liquid crystal which is initially aligned vertically, that is, a liquid crystal material which has a negative dielectric anisotropy. In the embodiment, a panel according to the invention is formed by the substrates  10  and  25  opposing each other via the sealant, with the liquid crystal layer  50  being sealed in the panel so as to be surrounded by the substrates  10  and  25  and the sealant.  
      In the lower substrate (opposing substrate)  10 , common electrodes  9 , formed of ITO, are formed on a surface of a substrate body  10 A, formed of a light-transmissive material such as quartz or glass. Openings  29  for controlling liquid crystal alignment are formed in the common electrodes  9 .  
      The common electrodes  9  are disposed in the form stripes extending perpendicularly to the plane of the figure and in the respective dot areas disposed in a row perpendicularly to the plane of the figure. An alignment layer  37 , formed of polyimide or the like, is formed on the common electrodes  9 . The alignment layer  37  acts as a vertical alignment layer for aligning liquid crystal molecules vertically with respect to the plane of the layer, and is not subjected to an alignment operation such as rubbing.  
      Pixel electrodes  31  (transparent conductive films formed of, for example, ITO) are disposed in a matrix between the upper substrate body  25 A and the liquid crystal layer  50 . As in the lower substrate  10 , an alignment layer  33 , formed of, for example, polyimide subjected to a vertical alignment operation is formed so as to cover the pixel electrodes  31 . Also, a color filter  22  (red coloring layer  22 R in  FIG. 4B ) is provided at the lower substrate  10  side.  
      One pixel electrode  31  is provided at each of the dot areas D 1  to D 3  and each of the dot areas D 1 ′ to D 3 ′. Voltages are separately applied to the respective dot areas by TFDs disposed at the respective dot areas.  
      In the embodiment, a columnar spacer  51  serving as a support along the height of the liquid crystal layer  50  is disposed so as to overlap the TFD element at the dot area D 1 . First protrusions  27  having a height that is less than the height of the columnar spacer  51  are disposed so as to overlap the TFD elements at the dot areas D 2  and D 3  and D 1 ′ to D 3 ′. The first protrusions  27  block the electrical field from the TFD elements in order to reduce differences between liquid crystal alignments at the dot areas, and protect the TFD elements at the dot areas D 2  and D 3  from external pressure. Although, in the embodiment, the columnar spacer  51  and the first protrusions  27  are disposed so as to overlap the TFD elements, they may be disposed at areas other than where the TFD elements are disposed. In this case, although the electrical field from the TFD elements cannot be blocked, this structure is effective in reducing the difference between the liquid crystal alignments at the dot areas. It is also effective in preventing damage to the TFD elements by push pressure because the opposing substrate  10  can be supported by the first protrusions  27 .  
      In the embodiment, second protrusions  28  are disposed entirely at the scanning lines  13  at the dot areas D 1  to D 3  and the dot areas D 1 ′ to D 3 ′. At the pixel areas where the first protrusions are disposed, the first protrusions and the second protrusions are connected, so that an electrical field generated from the scanning lines is more effectively blocked than in the first embodiment. In addition, the liquid crystal molecules can be disposed perpendicularly to inclined surfaces of the second protrusions  28 . The first and second protrusions are formed at the same time by the same process, so that the cost burden in the second embodiment is less than that in the first embodiment.  
      In the embodiment, each pixel electrode  31  comprises island-shaped portions (island-shaped portions  31   a ,  31   b , and  31   c  in  FIG. 4 ) and connecting portions  39  electrically connecting the adjacent island-shaped portions. Each of the island-shaped portions  31   a ,  31   b , and  31   c  forms a sub-dot, so that one dot comprises divided sub-dots. Although the sub-dots (island-shaped portions  31   a ,  31   b , and  31   c ) have octagonal shapes in  FIG. 4A , they may be, for example, circular or polygonal. Slits  32  are formed in portions of the associated pixel electrode  31  (the portions excluding the connecting portions  39 ) so as to be disposed between the island-shaped portions  31   a  and  31   b  and island-shaped portions  31   b  and  31   c . The slits  32  are disposed near the center between the sub-dots (island-shaped portions  31   a  and  31   b  and island-shaped portions  31   b  and  31   c ) and between the electrode openings  29 .  
      A retardation film  18  and a polarizer  19  are disposed at the outer surface of the lower substrate  10  (at a side opposite to the side where the liquid crystal layer  50  is sandwiched), and a retardation film  16  and a polarizer  17  are disposed at the outer surface of the upper substrate  25 , so that circularly polarized light can impinge upon the inner surfaces of the respective substrates facing the liquid crystal layer  50 . The retardation film  18  and the polarizer  19  and the retardation film  16  and the polarizer  17  form circularly polarizing units. The polarizers  17  and  19  are formed so as to pass only linearly polarized light having a polarization axis of a predetermined direction, and the retardation films  16  and  18  are λ/4 retardation films. Each circularly polarizing unit may comprise a combination of a polarizer, a λ/4 retardation film and a λ/2 retardation film (wide band circularly polarizing unit). In this case, it is possible to provide an achromatic color of a higher degree in a dark display. In addition, each circularly polarizing unit may comprise a combination of a polarizer, a λ/4 retardation film, a λ/2 retardation film, and a c plate (retardation film having an optical axis in the film thickness direction), so that a wider viewing angle range can be achieved. A backlight  15 , which is a light source for transmissive display, is disposed at the outer side of the polarizer  19  of the lower substrate  10 .  
      As in the first embodiment, even in the second embodiment, the first protrusions  27  having substantially the same shape as the columnar spacer  51  in plan view are disposed so as to overlap the TFD elements at the pixel areas where columnar spacers  51  are not disposed, so that the difference between the liquid crystal alignments at the pixel areas is eliminated and the electrical field from the TFD elements is blocked in order to reduce symmetrical distortion of the electrical field in the liquid crystal layer  50 . Therefore, it is possible to provide a liquid crystal display device providing a higher display quality. Since the first protrusions  27  protect the TFD elements, the TFD elements are prevented from becoming damaged due to external pressure such as push pressure, so that the structure of the liquid crystal display device according to the second embodiment is highly reliable.  
      Unlike the liquid crystal display device according to the first embodiment, the liquid crystal display device according to the second embodiment is a transmissive type. Therefore, the first and second protrusions  27  and  28  can easily be formed at the same time, thereby considerably reducing costs. In addition, since the first and second protrusions  27  and  28  are formed at the same time, they can be easily joined together, so that the electrical field generated from the TFD elements and the scanning lines  13  can be effectively blocked, thereby improving the line-of-flow property of the internal structure of the liquid crystal layer  50 .  
      In the second embodiment, since one columnar spacer  51  is disposed at one of the six dot areas D 1  to D 3  and D 1 ′ to D 3 ′, resiliency with respect to external shock is increased and failure due to bubbles is less likely to occur. In addition, since the first protrusions  27  protect the TFD elements, the TFD elements are not damaged, so that a more reliable liquid crystal display device can be provided.  
     Third Embodiment  
      A third embodiment of the invention will be described with reference to  FIGS. 5A and 5B .  
       FIGS. 5A and 5B  are a plan view and a sectional view of a liquid crystal display device of the third embodiment, respectively, and are schematic views in correspondence with those of  FIGS. 3A and 3B  showing the first embodiment. Parts in the third embodiment corresponding to those in the first embodiment are given the same reference numerals.  
      A liquid crystal display device  200  according to the third embodiment is a transmissive liquid crystal display device which does not have a reflective display area. As shown in  FIG. 5A , the liquid crystal display device  200  has dot areas including respective pixel electrodes  31  disposed inwardly of data lines  9 , scanning lines  13 , etc. In each dot area, one coloring layer for one of the three primary colors is disposed, so that pixel areas including respective coloring layers  22 B (blue),  22 G (green), and  22 R (red) are formed at three dot areas (D 1 , D 2 , and D 3 ).  
      Referring to the sectional structure, as shown in  FIG. 5B , the liquid crystal display device  200  according to the embodiment comprises a pair of substrates  10  and  25  opposing each other via a rectangular frame-shaped sealant (not shown) and a liquid crystal layer  50  disposed between the pair of substrates  10  and  25 . The liquid crystal layer  50  comprises liquid crystal which is initially aligned vertically, that is, a liquid crystal material which has a negative dielectric anisotropy. In the embodiment, a panel according to the invention is formed by the substrates  10  and  25  opposing each other via the sealant, with the liquid crystal layer  50  being sealed in the panel so as to be surrounded by the substrates  10  and  25  and the sealant.  
      In the lower substrate (opposing substrate)  10 , common electrodes  9 , formed of ITO, are formed on a surface of a substrate body  10 A, formed of a light-transmissive material such as quartz or glass.  
      The common electrodes  9  are disposed in the form of stripes extending perpendicularly to the plane of the figure and in the dot areas disposed in a row perpendicularly to the plane of the figure. An alignment layer  37 , formed of polyimide or the like, is formed on the common electrodes  9 . The alignment layer  37  acts as a vertical alignment layer for aligning liquid crystal molecules vertically with respect to the plane of the layer, and is not subjected to an alignment operation such as rubbing.  
      Pixel electrodes  31  (transparent conductive films formed of, for example, ITO) are disposed to in between the upper substrate body  25 A and the liquid crystal layer  50 . As in the lower substrate  10 , an alignment layer  33 , formed of, for example, polyimide subjected to a vertical alignment operation is formed so as to cover the pixel electrodes  31 . Also a color filter  22  (red coloring layer  22 R in  FIG. 5B ) is provided at the lower substrate  10  side.  
      One pixel electrode  31  is provided at each of the dot areas D 1  to D 3 . Voltages are separately applied to the respective dot areas by TFDs disposed at the respective dot areas.  
      In the embodiment, at the dot area D 1 , a columnar spacer  51  serving as a support along the height of the liquid crystal layer  50  is disposed in a gap between the pixel electrode and an adjacent pixel electrode. First protrusions  27  having a height that is less than the height of the columnar spacer  51  are disposed in the gaps between the pixel electrodes at the dot areas D 2  and D 3 . Although the first protrusions  27  cannot block the electrical field from the TFD elements as they do in the first and second embodiments, they are effective in reducing differences between liquid crystal alignments at the dot areas. In addition, they are effective in preventing damage to the TFD elements by push pressure because the opposing substrate  10  can be supported by the first protrusions  27 .  
      In the embodiment, second protrusions  28  for controlling alignment are disposed so as to overlap the pixel electrodes  31  at the dot areas D 1  to D 3 . In the embodiment, the second protrusions  28  are provided in place of the openings  29  in the first and second embodiments, and have an alignment restricting force of an azimuthal component that is higher than that resulting from the alignment control by the openings. By virtue of this structure, the diameters of the second protrusions are smaller than when the openings are formed, so that the area of the pixel electrodes used for a displaying operation can be made wider. As a result, a liquid crystal display device providing a brighter display can be provided. The first and second protrusions are formed at the same time by the same process, so that the cost burden in the third embodiment is less than that in the first embodiment.  
      In the embodiment, each pixel electrode  31  comprises island-shaped portions (island-shaped portions  31   a ,  31   b , and  31   c  in  FIG. 5 ) and connecting portions  39  electrically connecting the adjacent island-shaped portions. Each of the island-shaped portions  31   a ,  31   b , and  31   c  forms a sub-dot, so that one dot comprises divided sub-dots. Although the sub-dots (island-shaped portions  31   a ,  31   b , and  31   c ) have octagonal shapes in  FIG. 5A , they may be, for example, circular or polygonal. Slits  32  are formed in portions of the associated pixel electrode  31  (the portions excluding the connecting portions  39 ) so as to be disposed between the island-shaped portions  31   a  and  31   b  and island-shaped portions  31   b  and  31   c . The slits  32  are disposed near the center between the sub-dots (island-shaped portions  31   a  and  31   b  and island-shaped portions  31   b  and  31   c ) and between electrode openings  29 .  
      A retardation film  18  and a polarizer  19  are disposed at the outer surface of the lower substrate  10  (at a side opposite to the side where the liquid crystal layer  50  is sandwiched), and a retardation film  16  and a polarizer  17  are disposed at the outer surface of the upper substrate  25 , so that circularly polarized light can impinge upon the inner surfaces of the respective substrates facing the liquid crystal layer  50 . The retardation film  18  and the polarizer  19  and the retardation film  16  and the polarizer  17  form circularly polarizing units. The polarizers  17  and  19  are formed so as to pass only linearly polarized light having a polarization axis of a predetermined direction, and the retardation films  16  and  18  are λ/4 retardation films. Each circularly polarizing unit may comprise a combination of a polarizer, a λ/4 retardation film and a λ/2 retardation film (wide band circularly polarizing unit). In this case, it is possible to provide an achromatic color of a higher degree in a dark display. In addition, each circularly polarizing unit may comprise a combination of a polarizer, a λ/4 retardation film, a λ/2 retardation film, and a c plate (retardation film having an optical axis in the film thickness direction), so that a wider viewing angle range can be achieved. A backlight  15 , which is a light source for transmissive display, is disposed at the outer side of the polarizer  19  of the lower substrate  10 .  
      In the third embodiment, the first protrusions  27  having substantially the same shape as the columnar spacer  51  in plan view are disposed in the gaps at the pixel areas where columnar spacers  51  are not disposed, so that the difference between the liquid crystal alignments at the pixel areas is eliminated. Therefore, it is possible to provide a liquid crystal display device providing a higher display quality. The first protrusions  27  act as supports and thus prevent the TFD elements from becoming damaged by external pressure such as push pressure. Therefore, the structure of the liquid crystal display device according to the third embodiment is highly reliable.  
      Electronic Apparatus  
      A specific example of an electronic apparatus comprising the liquid crystal display device according to any one of the embodiments of the invention will be described.  
       FIG. 6  is a perspective view of an example of a cellular phone. In  FIG. 6 , reference numeral  1000  denotes a cellular phone body and reference numeral  1001  denotes a display unit using any one of the above-described liquid crystal display devices. When the liquid crystal display device according to any one of the aforementioned embodiments is used in the display unit of the electronic apparatus such as a cellular phone, the electronic apparatus comprises a liquid crystal display unit which provides a highly reliable bright display having a high contrast and a wide viewing angle range regardless of the environment in which the apparatus is used.  
      The liquid crystal display device according to any one of the aforementioned embodiments may be suitably used as image displaying means not only in the cellular phone but also in an electronic book, a personal computer, a digital still camera, a liquid crystal television, a view finder or a monitor direct viewing video tape recorder, a car navigation system, a pager, an electronic notebook, a calculator, a word processor, a work station, a television telephone, a POS terminal, or a touch panel. Therefore, any of these electronic apparatuses can provide a highly reliable display having a high contrast and a wide viewing angle range.  
      The technical scope of the invention is not limited to the above-described embodiments, so that various modifications may be made without departing from the gist of the invention.  
      Although, in the above-described embodiments, the invention is applied to an active matrix liquid crystal display device using TFDs as switching elements, the invention is also applicable to, for example, an active matrix liquid crystal display device using TFTs as switching elements and to a passive matrix liquid crystal display device.