Patent Publication Number: US-2023133222-A1

Title: Display device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a Continuation Application of PCT Application No. PCT/JP2020/006510, filed Feb. 19, 2020 and based upon and claiming the benefit of priority from Japanese Patent Application No. 2019-041735, filed Mar. 7, 2019, the entire contents of all of which are incorporated herein by reference. 
    
    
     FIELD 
     Embodiments described herein relate generally to a display device. 
     BACKGROUND 
     In recent years, various illumination devices including a light modulation element exhibiting scattering property or transparency to light have been proposed. In one example, the light modulation element includes a polymer dispersed liquid crystal layer as the light modulation layer. The light modulation element is disposed behind a light guide and scatters light incident from a side surface of the light guide. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a plan view illustrating a configuration example of a display device DSP of the present embodiment. 
         FIG.  2    is a cross-sectional view illustrating a first configuration example of a display panel PNL illustrated in  FIG.  1   . 
         FIG.  3    is a plan view illustrating an example of a pixel PX illustrated in  FIG.  2   . 
         FIG.  4 A  is a plan view illustrating an example of a first common electrode CE 1  illustrated in  FIG.  2   . 
         FIG.  4 B  is a plan view illustrating an example of a second common electrode CE 2  illustrated in  FIG.  2   . 
         FIG.  5    is a plan view illustrating a state in which the first common electrode CE 1  and the second common electrode CE 2  illustrated in  FIGS.  4 A and  4 B  overlap. 
         FIG.  6    is a cross-sectional view illustrating an example of the display device DSP of the present embodiment. 
         FIG.  7    is a cross-sectional view illustrating an example of pixels PX 1  to PX 3 . 
         FIG.  8    is a schematic diagram illustrating an electric field distribution and an alignment state of liquid crystal molecules in the pixel PX 3 . 
         FIG.  9    is a schematic diagram illustrating an electric field distribution and an alignment state of the liquid crystal molecules in the pixel PX 1 . 
         FIG.  10    is a schematic diagram illustrating a luminance distribution and an alignment state of the liquid crystal molecules in the pixel PX 3  illustrated in  FIG.  8   . 
         FIG.  11    is a schematic diagram illustrating a luminance distribution and an alignment state of the liquid crystal molecules in the pixel PX 1  illustrated in  FIG.  9   . 
         FIG.  12    is a schematic diagram illustrating an electric field distribution and an alignment state of the liquid crystal molecules in the pixel PX 2 . 
         FIG.  13    is a cross-sectional view illustrating a second configuration example. 
         FIG.  14    is a cross-sectional view illustrating a third configuration example. 
         FIG.  15    is a cross-sectional view illustrating a fourth configuration example. 
         FIG.  16    is a cross-sectional view illustrating a power supply structure for applying a voltage to the first common electrode CE 1  and the second common electrode CE 2 . 
         FIG.  17    is a cross-sectional view illustrating a fifth configuration example. 
         FIG.  18    is a cross-sectional view illustrating a power supply structure for applying a voltage to the common electrode CE illustrated in  FIG.  17   . 
     
    
    
     DETAILED DESCRIPTION 
     In general, according to one embodiment, there is provided a display device including: a first substrate including a first transparent substrate, a switching element, and a pixel electrode electrically connected to the switching element; a second substrate including a second transparent substrate, a first common electrode, a second common electrode having the same electric potential as the first common electrode, and an insulating film disposed between the first common electrode and the second common electrode; and a liquid crystal layer that is disposed between the first substrate and the second substrate, and contains polymers and liquid crystal molecules, wherein the first common electrode is disposed between the liquid crystal layer and the insulating film, and includes a first opening and a first electrode portion, and the second common electrode is disposed between the insulating film and the second transparent substrate, and includes a second electrode portion overlapping the first opening. 
     According to the present embodiment, there is provided a display device including: a first substrate including a first transparent substrate, a switching element, a first pixel electrode and a second pixel electrode electrically connected to the switching element, and an insulating film disposed between the first pixel electrode and the second pixel electrode; a second substrate including a second transparent substrate, and a common electrode, and a liquid crystal layer that is disposed between the first substrate and the second substrate, and contains polymers and liquid crystal molecules, wherein the first pixel electrode is disposed between the insulating film and the liquid crystal layer, and includes a first opening and a first electrode portion, and the second pixel electrode is disposed between the first transparent substrate and the insulating film, and includes a second electrode portion overlapping the first opening. 
     According to the present embodiment, there is provided a display device including: a first substrate; a second substrate; a liquid crystal layer that is disposed between the first substrate and the second substrate, and contains polymers and liquid crystal molecules, and a light emitting element facing a side surface of the second substrate, wherein the first substrate or the second substrate includes a transparent substrate, a first transparent electrode, a second transparent electrode having the same electric potential as the first transparent electrode, and an insulating film disposed between the first transparent electrode and the second transparent electrode, each of the first transparent electrode and the second transparent electrode includes a plurality of openings, the openings of the first transparent electrode and the openings of the second transparent electrode do not overlap each other, and the first transparent electrode includes a first opening and a third opening, and the first opening is disposed between the light emitting element and the third opening, and has a width larger than the third opening. 
       FIG.  1    is a plan view illustrating a configuration example of a display device DSP of the present embodiment. In one example, a first direction X, a second direction Y, and a third direction Z are orthogonal to each other, but may intersect at an angle other than 90 degrees. The first direction X and the second direction Y correspond to a direction parallel to a main surface of a substrate constituting the display device DSP, and the third direction Z corresponds to a thickness direction of the display device DSP. It is assumed that there is an observation position where the display device DSP is observed on a distal end side of an arrow indicating the third direction Z, and a view from this observation position toward an X-Y plane defined by the first direction X and the second direction Y is referred to as a plan view. 
     In the present embodiment, a liquid crystal display device to which a polymer dispersed liquid crystal is applied will be described as an example of the display device DSP. The display device DSP includes a display panel PNL, a wiring board  1 , an IC chip  2 , and light emitting elements LD. 
     The display panel PNL includes a first substrate SUB 1 , a second substrate SUB 2 , a liquid crystal layer LC, and a sealant SE. The first substrate SUB 1  and the second substrate SUB 2  are formed in a flat plate shape parallel to the X-Y plane. The first substrate SUB 1  and the second substrate SUB 2  overlap each other in plan view. The first substrate SUB 1  and the second substrate SUB 2  are bonded by the sealant SE. The liquid crystal layer LC is held between the first substrate SUB 1  and the second substrate SUB 2 , and is sealed by the sealant SE. In  FIG.  1   , the liquid crystal layer LC and the sealant SE are indicated by different oblique lines. 
     As schematically illustrated in an enlarged manner in  FIG.  1   , the liquid crystal layer LC includes a polymer-dispersed liquid crystal containing polymers  31  and liquid crystal molecules  32 . In one example, the polymers  31  are liquid-crystal polymers. The polymers  31  are formed in a streak shape extending along the first direction X. The liquid crystal molecules  32  are dispersed in gaps between the polymers  31 , and are aligned such that long axes are along the first direction X. Each of the polymers  31  and the liquid crystal molecules  32  has optical anisotropy or refractive index anisotropy. The responsiveness of the polymers  31  to an electric field is lower than the responsiveness of the liquid crystal molecules  32  to the electric field. 
     In one example, an alignment direction of the polymers  31  hardly changes regardless of the presence or absence of the electric field. On the other hand, an alignment direction of the liquid crystal molecules  32  changes according to the electric field in a state in which a high voltage equal to or higher than a threshold value is applied to the liquid crystal layer LC. In the state in which the voltage is not applied to the liquid crystal layer LC, optical axes of the polymers  31  and the liquid crystal molecules  32  are parallel to each other, and light incident on the liquid crystal layer LC is transmitted without being almost scattered in the liquid crystal layer LC (transparent state). In the state in which the voltage is applied to the liquid crystal layer LC, the optical axes of the polymers  31  and the liquid crystal molecules  32  intersect each other, and the light incident on the liquid crystal layer LC is scattered in the liquid crystal layer LC (scattering state). 
     The display panel PNL includes a display area DA in which an image is displayed, and a frame-shaped non-display area NDA that surrounds the display area DA. The sealant SE is disposed in the non-display area NDA. The display area DA includes pixels PX arranged in a matrix in the first direction X and the second direction Y. 
     As illustrated in an enlarged manner in  FIG.  1   , each pixel PX includes a switching element SW, a pixel electrode PE, a common electrode CE, a liquid crystal layer LC, and the like. The switching element SW includes, for example, a thin film transistor (TFT), and is electrically connected to scanning lines G and signal lines S. 
     The scanning line G is electrically connected to the switching element SW in each of the pixels PX arranged in the first direction X. The signal line S is electrically connected to the switching element SW in each of the pixels PX arranged in the second direction Y. The pixel electrode PE is electrically connected to the switching element SW. The common electrode CE is provided in common for the plurality of pixel electrodes PE. Each of the pixel electrodes PE faces the common electrode CE in the third direction Z. The liquid crystal layer LC (in particular, liquid crystal molecules  32 ) is driven by an electric field generated between the pixel electrode PE and the common electrode CE. A capacitance CS is formed, for example, between an electrode having the same electric potential as the common electrode CE and an electrode having the same electric potential as the pixel electrode PE. 
     As will be described later, the scanning line G, the signal line S, the switching element SW, and the pixel electrode PE are provided on the first substrate SUB 1 , and the common electrode CE is provided on the second substrate SUB 2 . In the first substrate SUB 1 , the scanning line G and the signal line S are electrically connected to the wiring board  1  or the IC chip  2 . 
     The wiring board  1  is electrically connected to an extension portion Ex of the first substrate SUB 1 . The wiring board  1  is a bendable flexible printed circuit board. The IC chip  2  is electrically connected to the wiring board  1 . The IC chip  2  incorporates, for example, a display driver that outputs a signal necessary for image display. The IC chip  2  may be electrically connected to the extension portion Ex. 
     The light emitting elements LD overlap the extension portion Ex in plan view. The plurality of light emitting elements LD is arranged at intervals along the first direction X. 
     First Configuration Example 
       FIG.  2    is a cross-sectional view illustrating a first configuration example of the display panel PNL illustrated in  FIG.  1   . The liquid crystal layer LC is provided between the first substrate SUB 1  and the second substrate SUB 2 . 
     The first substrate SUB 1  includes a first transparent substrate  10 , insulating films  11  and  12 , a capacitance electrode  13 , switching elements SW, a pixel electrode PE, and an alignment film AL 1 . The first transparent substrate  10  includes a main surface (lower surface)  10 A and a main surface (upper surface)  10 B opposite to the main surface  10 A. The switching elements SW are arranged on the main surface  10 B side. The insulating film  11  covers the switching elements SW. The scanning lines G and the signal lines S illustrated in  FIG.  1    are arranged between the first transparent substrate  10  and the insulating film  11 , but are not illustrated here. The capacitance electrode  13  is disposed between the insulating films  11  and  12 . The pixel electrode PE is disposed for each pixel PX between the insulating film  12  and the alignment film AL 1 . The pixel electrode PE is electrically connected to the switching element SW via an opening OP of the capacitance electrode  13 . The pixel electrode PE overlaps the capacitance electrode  13  with the insulating film  12  interposed therebetween to form the capacitance CS of the pixel PX. The alignment film AL 1  covers the pixel electrode PE. The alignment film AL 1  is in contact with the liquid crystal layer LC. 
     The second substrate SUB 2  includes a second transparent substrate  20 , a first common electrode CE 1 , a second common electrode CE 2 , an insulating film  21 , and an alignment film AL 2 . The second transparent substrate  20  includes a main surface (lower surface)  20 A and a main surface (upper surface)  20 B opposite to the main surface  20 A. The main surface  20 A of the second transparent substrate  20  faces the main surface  10 B of the first transparent substrate  10 . The second substrate SUB 2  may include a light shielding layer immediately above the scanning lines G, the signal lines S, and the switching elements SW. 
     The insulating film  21  is provided between the first common electrode CE 1  and the second common electrode CE 2 . In one example, the insulating film  21  is a transparent organic insulating film, but may be an inorganic insulating film. The first common electrode CE 1  and the second common electrode CE 2  are arranged over the plurality of pixels PX, and face the plurality of pixel electrodes PE in the third direction Z. 
     The first common electrode CE 1  is provided between the liquid crystal layer LC and the insulating film  21 . The first common electrode CE 1  includes first openings AP 1  and first electrode portions EL 1  that define the first openings AP 1 . In other words, a region of the first common electrode CE 1  that is not the first opening AP 1  is referred to as the first electrode portion EL 1 . The alignment film AL 2  covers the first common electrode CE 1 . The alignment film AL 2  is in contact with the insulating film  21  in the first openings AP 1 . The alignment film AL 2  is in contact with the liquid crystal layer LC. 
     The second common electrode CE 2  has the same electric potential as the first common electrode CE 1 , and the first and second common electrodes are electrically connected to each other in the non-display area NDA as will be described later. The first common electrode CE 1  and the second common electrode CE 2  are electrically connected to the capacitance electrode  13 , and have the same electric potential as the capacitance electrode  13 . The second common electrode CE 2  is provided between the insulating film  21  and the second transparent substrate  20 . The second common electrode CE 2  includes second electrode portions EL 2  overlapping the first openings AP 1 . In the example illustrated in  FIG.  2   , the second common electrode CE 2  includes second openings AP 2  defined by the second electrode portions EL 2 . A region of the second common electrode CE 2  that is not the second opening AP 2  is referred to as the second electrode portion EL 2 . The insulating film  21  is in contact with the second transparent substrate  20  at the second openings AP 2 . The first electrode portion EL 1  overlaps the second opening AP 2 . 
     In the third direction Z, the pixel electrode PE faces the first electrode portion EL 1 , and in the first opening AP 1 , faces the second electrode portion EL 2 . 
     The first transparent substrate  10  and the second transparent substrate  20  are insulating substrates such as a glass substrate and a plastic substrate. The insulating film  11  is made of a transparent insulating material such as a silicon oxide, a silicon nitride, a silicon oxynitride, or an acrylic resin. In one example, the insulating film  11  includes an inorganic insulating film and an organic insulating film. The insulating film  12  is an inorganic insulating film such as a silicon nitride. The capacitance electrode  13 , the pixel electrode PE, the first common electrode CE 1 , and the second common electrode CE 2  are transparent electrodes made of a transparent conductive material such as an indium tin oxide (ITO) or an indium zinc oxide (IZO). An alignment treatment is performed on the alignment films AL 1  and AL 2  along, for example, the first direction X. The alignment treatment may be a rubbing treatment or a photo-alignment treatment. 
       FIG.  3    is a plan view illustrating an example of the pixel PX illustrated in  FIG.  2   . The scanning lines G extend in the first direction X, and the signal lines S extend in the second direction Y. The switching element SW is provided at an intersection of the scanning line G and the signal line S. The switching element SW includes a semiconductor layer SC. The semiconductor layer SC overlaps a gate electrode SWG integrated with the scanning line G. A source electrode SWS integrated with the signal line S and a drain electrode SWD are electrically connected to the semiconductor layer SC. The pixel electrode PE is provided between the adjacent scanning lines G and between the adjacent signal lines S. The pixel electrode PE overlaps the drain electrode SWD and is electrically connected to the switching element SW. 
       FIGS.  4 A and  4 B  are plan views illustrating examples of the first common electrode CE 1  and the second common electrode CE 2  illustrated in  FIG.  2   . Here, four pixel electrodes PE arranged two by two in each of the first direction X and the second direction Y are indicated by dotted lines. 
     As illustrated in  FIG.  4 A , the first common electrode CE 1  includes three first openings AP 1  overlapping one pixel electrode PE. Each of the plurality of first openings AP 1  extends in the first direction X and is arranged in the second direction Y. The plurality of first openings AP 1  may be arranged in the first direction X and extend in the second direction Y. A shape of the first opening AP 1  is not limited to a rectangle of the example illustrated in  FIG.  4 A , and may be other shapes such as a square, a circle, and an ellipse. The first common electrode CE 1  may include the plurality of first openings AP 1  arranged in the first direction X and the second direction Y in a region overlapping one pixel electrode PE. The first electrode portion EL 1  defines the first opening AP 1 , and overlaps each pixel electrode PE. A part of the first electrode portions EL 1  overlaps over the pixel electrodes PE adjacent in the first direction X and the second direction Y. 
     As illustrated in  FIG.  4 B , the second common electrode CE 2  includes four second openings AP 2  overlapping one pixel electrode PE. A part of the second openings AP 2  overlaps over the pixel electrodes PE adjacent in the second direction Y. The second opening AP 2  is formed in a region overlapping the first electrode portion EL 1 . Each of the plurality of second openings AP 2  extends in the first direction X and is arranged in the second direction Y. Similarly to the first opening AP 1 , a layout and a shape of the second opening AP 2  are not limited to the illustrated example. The second electrode portion EL 2  defines the second opening AP 2  and overlaps each pixel electrode PE. The second electrode portion EL 2  is formed in a region overlapping at least the first opening AP 1 . In other words, a shape of the second electrode portion EL 2  may be appropriately deformed in accordance with the shape of the first opening AP 1 . 
       FIG.  5    is a plan view illustrating a state in which the first common electrode CE 1  and the second common electrode CE 2  illustrated in  FIGS.  4 A and  4 B  overlap. 
     The first common electrode CE 1  is indicated by a dot pattern, and the second common electrode CE 2  is indicated by oblique lines. Each of the pixel electrodes PE overlaps the first electrode portion EL 1 , and overlaps the second electrode portion EL 2  in the first opening AP 1 . In plan view, it is desirable that there is no gap between the first electrode portion EL 1  and the second electrode portion EL 2 . 
       FIG.  6    is a cross-sectional view illustrating an example of the display device DSP of the present embodiment. Only main parts are illustrated in the display panel PNL, and the first common electrode CE 1  and the second common electrode CE 2  are illustrated in a simplified manner. 
     The second transparent substrate  20  includes a side surface  20 C facing the light emitting element LD in the second direction Y. The light emitting element LD is electrically connected to a wiring board F. The light emitting element LD is, for example, a light emitting diode, and includes a red light emitting portion, a green light emitting portion, and a blue light emitting portion although not described in detail. 
     Next, light L 1  emitted from the light emitting element LD will be described with reference to  FIG.  6   . 
     The light emitting element LD emits the light L 1  toward the side surface  20 C. The light L 1  emitted from the light emitting element LD travels along a direction of an arrow indicating the second direction Y, and is incident on the second transparent substrate  20  from the side surface  20 C. The light L 1  incident on the second transparent substrate  20  travels inside the display panel PNL while being repeatedly reflected. The light L 1  incident on the liquid crystal layer LC to which the voltage is not applied is transmitted through the liquid crystal layer LC without being almost scattered. The light L 1  incident on the liquid crystal layer LC to which the voltage is applied is scattered by the liquid crystal layer LC. The display device DSP can be observed from the main surface  10 A side and can also be observed from the main surface  20 B side. The display device DSP can observe a background of the display device DSP via the display device DSP even when the background is observed from the main surface  10 A side or the main surface  20 B side. 
     In the display panel PNL illustrated in  FIG.  6   , respective configurations of a pixel PX 3  close to the light emitting element LD, a pixel PX 1  farther away from the light emitting element LD than the pixel PX 3 , and a pixel PX 2  farther away from the light emitting element LD than the pixel PX 1  will be described. For example, the pixel PX 1  may be disposed substantially at a center of the display panel PNL. 
       FIG.  7    is a cross-sectional view illustrating an example of the pixels PX 1  to PX 3 . Here, only main parts of the pixels PX 1  to PX 3  are illustrated. 
     In the pixel PX 1 , the first common electrode CE 1  includes the first opening AP 1  and the first electrode portion EL 1 . The first opening AP 1  has a width W 11  along the second direction Y. The first electrode portion EL 1  has a width W 12  along the second direction Y. The second common electrode CE 2  includes the second opening AP 2  overlapping the first electrode portion EL 1  and the second electrode portion EL 2  overlapping the first opening AP 1 . A width of the second opening AP 2  is equal to the width W 12 , and a width of the second electrode portion EL 2  is equal to the width W 11 . The pixel electrode PE 1  overlaps the first electrode portion EL 1  and the second electrode portion EL 2 . The first opening AP 1  and the second opening AP 2  do not overlap each other in the third direction Z, and the first electrode portion EL 1  and the second electrode portion EL 2  do not overlap each other. A part of the first opening AP 1  and a part of the second opening AP 2  may overlap each other, or a part of the first electrode portion EL 1  and a part of the second electrode portion EL 2  may overlap each other. 
     In the pixel PX 2 , the first common electrode CE 1  includes a third opening AP 3  and a third electrode portion EL 3  that defines the third opening AP 3 . In other words, a region of the first common electrode CE 1  of the pixel PX 2  that is not the third opening AP 3  is defined as the third electrode portion EL 3 . The third electrode portion EL 3  is formed integrally with the first electrode portion EL 1 , and has the same electric potential as the first electrode portion EL 1 . The third opening AP 3  has a width W 21  different from the width W 11  along the second direction Y. The third electrode portion EL 3  has a width W 22  different from the width W 12  along the second direction Y. 
     The second common electrode CE 2  includes a fourth opening AP 4  and a fourth electrode portion EL 4  that defines the fourth opening AP 4 . In other words, a region of the second common electrode CE 2  of the pixel PX 2  that is not the fourth opening AP 4  is referred to as the fourth electrode portion EL 4 . The fourth electrode portion EL 4  is formed integrally with the second electrode portion EL 2  and has the same electric potential as the second electrode portion EL 2 . The fourth opening AP 4  overlaps the third electrode portion EL 3 , and the fourth electrode portion EL 4  overlaps the third opening AP 3 . A width of the fourth opening AP 4  is equal to the width W 22 , and a width of the fourth electrode portion EL 4  is equal to the width W 21 . The pixel electrode PE 2  overlaps the third electrode portion EL 3  and the fourth electrode portion EL 4 . 
     In the first common electrode CE 1 , the first opening AP 1  is provided between the light emitting element LD and the third opening AP 3  along the second direction Y. The width W 21  of the third opening AP 3  is smaller than the width W 11  of the first opening AP 1 . The first electrode portion EL 1  is provided between the light emitting element LD and the third electrode portion EL 3  along the second direction Y. The width W 22  of the third electrode portion EL 3  is smaller than the width W 12  of the first electrode portion EL 1 . 
     The number of third openings AP 3  overlapping the pixel electrode PE 2  is larger than the number of first openings AP 1  overlapping the pixel electrode PE 1 . The number of edges of the third electrode portion EL 3  that defines the third opening AP 3  is larger than the number of edges of the first electrode portion EL 1  that defines the first opening AP 1 . That is, the first common electrode CE 1  is more subdivided in the pixel PX 2  than in the pixel PX 1 . 
     In the pixel PX 3 , the first common electrode CE 1  includes a fifth electrode portion EL 5 . The fifth electrode portion EL 5  is formed integrally with the first electrode portion EL 1 , and has the same electric potential as the first electrode portion EL 1 . The first common electrode CE 1  may include a fifth opening, but is not illustrated here. The second common electrode CE 2  includes a sixth opening AP 6  overlapping the fifth electrode portion EL 5 . It is desirable that the second common electrode CE 2  includes a sixth electrode portion overlapping the fifth opening when the first common electrode CE 1  includes the fifth opening. The pixel electrode PE 3  overlaps the fifth electrode portion EL 5 . When the second common electrode CE 2  includes the sixth electrode portion, the pixel electrode PE 3  overlaps the sixth electrode. 
       FIG.  8    is a schematic diagram illustrating an electric field distribution and an alignment state of liquid crystal molecules in the pixel PX 3 . When a voltage is applied to the pixel PX 3 , an electric field is formed between the pixel electrode PE 3  and the fifth electrode portion EL 5  of first common electrode CE 1 . At this time, each of equi-electric potential surfaces is substantially parallel to the X-Y plane. That is, a line of electric force substantially parallel to the third direction Z is formed between the pixel electrode PE 3  and the fifth electrode portion EL 5 . The liquid crystal molecules LM have positive dielectric anisotropy, and are aligned such that long axes are along the line of electric force. That is, in the liquid crystal layer LC between the pixel electrode PE 3  and the fifth electrode portion EL 5 , substantially all the liquid crystal molecules LM are aligned along the third direction Z. 
       FIG.  9    is a schematic diagram illustrating an electric field distribution and an alignment state of the liquid crystal molecules in the pixel PX 1 . When a voltage is applied to the pixel PX 1 , electric fields are formed between the pixel electrode PE 1  and the first electrode portion EL 1  of the first common electrode CE 1 , and between the pixel electrode PE 1  and the second electrode portion EL 2  of the second common electrode CE 2 . At this time, equi-electric potential surfaces between the pixel electrode PE 1  and the first electrode portion EL 1  are substantially parallel to the X-Y plane. An interval between equi-electric potential surfaces between the pixel electrode PE 1  and the second electrode portion EL 2  extends in the third direction Z, and a part of the equi-electric potential surfaces is formed beyond the first opening AP 1  toward the second electrode portion EL 2 . Equi-electric potential surfaces are inclined with respect to the X-Y plane in the vicinity of boundaries between the first electrode portion EL 1  and the second electrode portion EL 2  (or an edge E 1  of the first electrode portion EL 1 ). 
     The liquid crystal molecules LM between the pixel electrode PE 1  and the first electrode portion EL 1  are aligned along the third direction Z. In the vicinity of the boundaries between the first electrode portion EL 1  and the second electrode portion EL 2 , the liquid crystal molecules LM are obliquely aligned with respect to the third direction Z under the influence of the inclined equi-electric potential surfaces. 
       FIG.  10    is a schematic diagram illustrating a luminance distribution and an alignment state of the liquid crystal molecules in the pixel PX 3  illustrated in  FIG.  8   . A luminance distribution B 3  in the drawing corresponds to a distribution of scattering intensity of light propagated from the light emitting element to the pixel PX 3  when a voltage is applied to the pixel PX 3 . Luminance BA between the pixel electrode PE 3  and the fifth electrode portion EL 5  is substantially constant regardless of a location. 
       FIG.  11    is a schematic diagram illustrating a luminance distribution and an alignment state of the liquid crystal molecules in the pixel PX 1  illustrated in  FIG.  9   . A luminance distribution B 1  in the drawing corresponds to a distribution of scattering intensity of light propagated from the light emitting element to the pixel PX 1  when a voltage is applied to the pixel PX 1 . Luminance BB higher than the luminance BA of the pixel PX 3  is obtained in the vicinity of the boundaries between the first electrode portion EL 1  and the second electrode portion EL 2 . For example, the luminance BB is 1.3 to 1.5 times the luminance BA. Such an increase in the luminance is caused by the liquid crystal molecules LM obliquely aligned with respect to the third direction Z in the vicinity of the boundaries between the first electrode portion EL 1  and the second electrode portion EL 2 . 
     In a region in which the liquid crystal molecules LM are aligned along the third direction Z between the pixel electrode PE 1  and the first electrode portion EL 1  and between the pixel electrode PE 1  and the second electrode portion EL 2 , the luminance BA equal to that of the pixel PX 3  is obtained. 
     Accordingly, when light of the same luminance propagates to the pixel PX 1  and the pixel PX 3 , the luminance of the scattered light in the pixel PX 1  is larger than the luminance of the scattered light in the pixel PX 3 . 
       FIG.  12    is a schematic diagram illustrating an electric field distribution and an alignment state of the liquid crystal molecules in the pixel PX 2 . When a voltage is applied to the pixel PX 2 , electric fields are formed between the pixel electrode PE 2  and the third electrode portion EL 3  of the first common electrode CE 1 , and between the pixel electrode PE 2  and the fourth electrode portion EL 4  of the second common electrode CE 2 . In the vicinity of boundaries between the third electrode portion EL 3  and the fourth electrode portion EL 4 , equi-electric potential surfaces are inclined with respect to the X-Y plane. In the vicinity of the boundaries between the third electrode portion EL 3  and the fourth electrode portion EL 4 , the liquid crystal molecules LM are obliquely aligned with respect to the third direction Z under the influence of the inclined equi-electric potential surfaces. The liquid crystal molecules LM are aligned along the third direction Z between the pixel electrode PE 2  and the third electrode portion EL 3  and between the pixel electrode PE 2  and the fourth electrode portion EL 4 . 
     As described with reference to  FIG.  7   , the number of third openings AP 3  in the pixel PX 2  is larger than the number of first openings AP 1  in the pixel PX 1 . That is, the number of boundaries between the third electrode portion EL 3  and the fourth electrode portion EL 4  is larger than the number of boundaries between the first electrode portion EL 1  and the second electrode portion EL 2 . Thus, a region in which the luminance increases in the pixel PX 2  is larger than a region in which the luminance increases in the pixel PX 1 . Accordingly, when light of the same luminance propagates to the pixel PX 1  and the pixel PX 2 , the luminance of the scattered light in the pixel PX 2  is larger than the luminance of the scattered light in the pixel PX 1 . 
     The display device DSP of the present embodiment is a system in which the light L 1  from the light emitting element LD is incident from the side surface  20 C of the second substrate SUB 2  and propagates through the display panel PNL. Focusing on the luminance distribution in such a display device DSP, the luminance tends to decrease as a distance from the light emitting element LD increases. 
     The luminance of the light propagated to the pixel PX 1  is referred to as first luminance, and the luminance of the light propagated to the pixel PX 3  closer to the light emitting element LD than the pixel PX 1  is referred to as third luminance. The first luminance is lower than the third luminance. On the other hand, the luminance of the scattered light in the pixel PX 1  is larger than the luminance of the scattered light in the pixel PX 3 . Thus, in the pixel PX 1  and the pixel PX 3 , the amount of light contributing to display can be equalized. 
     The luminance of the light propagated to the pixel PX 2  farther away from the light emitting element LD than the pixel PX 1  is referred to as second luminance. The second luminance is lower than the first luminance. On the other hand, the luminance of the scattered light in the pixel PX 2  is larger than the luminance of the scattered light in the pixel PX 1 . Thus, in the pixel PX 1  and the pixel PX 2 , the amount of light contributing to display can be equalized. Accordingly, it is possible to suppress a decrease in display quality due to the decrease in the luminance. 
     According to the present embodiment, the second common electrode CE 2  includes the second opening AP 2  overlapping the first electrode portion EL 1 . Thus, even though the second common electrode CE 2  is a transparent electrode having light absorbency, an electrode area can be reduced as compared with the case where the second opening AP 2  is not provided, and light absorption can be suppressed. 
     Second Configuration Example 
       FIG.  13    is a cross-sectional view illustrating a second configuration example. A second substrate SUB 2  of the second configuration example illustrated in  FIG.  13    is different from the second substrate SUB 2  of the first configuration example illustrated in  FIG.  2    in that a transparent layer TL is provided. In  FIG.  13   , the second substrate SUB 2  and the liquid crystal layer LC are illustrated, and the first substrate is not illustrated. 
     The transparent layer TL is provided between the second electrode portion EL 2  and the second transparent substrate  20 . The transparent layer TL is in contact with the second transparent substrate  20  and the second electrode portion EL 2 . Although not illustrated, the same transparent layer TL is also provided between another electrode portion of the second common electrode CE 2  and the second transparent substrate  20 . Another member may be interposed between the second electrode portion EL 2  and the transparent layer TL. The insulating film  21  covers the second electrode portion EL 2  and the transparent layer TL. 
     The transparent layer TL is, for example, an insulating layer made of a transparent organic material such as a siloxane-based resin or a fluorine-based resin. Regarding a refractive index, a refractive index nTL of the transparent layer TL is lower than a refractive index n 20  of the second transparent substrate  20 . A refractive index n 10  of the first transparent substrate  10  is equal to the refractive index n 20 . For example, the refractive indexes n 10  and n 20  are about 1.5, and the refractive index nTL is 1.0 or more and 1.5 or less. 
     Of the light incident on the second transparent substrate  20 , light L 11  directed to the second electrode portion EL 2  is reflected at an interface between the second transparent substrate  20  and the transparent layer TL and does not reach the second electrode portion EL 2 . Light L 12  directed toward the second opening AP 2  is transmitted through the insulating film  21  and is incident on the liquid crystal layer LC. 
     According to such a second configuration example, the same effects as those of the first configuration example are obtained. Even when the light absorbency of the second common electrode CE 2  is higher than the light absorbency of the insulating film  21 , the absorption of the light L 11  by the second common electrode CE 2  can be suppressed, and a decrease in utilization efficiency of the light from the light emitting element LD can be suppressed. 
     Third Configuration Example 
       FIG.  14    is a cross-sectional view illustrating a third configuration example. A second substrate SUB 2  of the third configuration example illustrated in  FIG.  14    is different from the second substrate SUB 2  of the second configuration example illustrated in  FIG.  13    in that the transparent layer TL is provided between the insulating film  21  and the second transparent substrate  20  in the second opening AP 2 . In  FIG.  14   , the second substrate SUB 2  and the liquid crystal layer LC are illustrated, and the first substrate is not illustrated. The transparent layer TL is in contact with the insulating film  21  and the second transparent substrate  20 . Although not illustrated, the same transparent layer TL is also provided in other openings of the second common electrode CE 2 . As a material of the transparent layer TL, the same material as that described in the second configuration example can be applied. A refractive index of the transparent layer TL is lower than a refractive index of the second transparent substrate  20 . 
     Of the light incident on the second transparent substrate  20 , light L 21  directed to the second opening AP 2  is reflected at an interface between the second transparent substrate  20  and the transparent layer TL, and does not reach the insulating film  21  via the second opening AP 2 . Light L 22  directed toward the second electrode portion EL 2  is transmitted through the second electrode portion EL 2  and is incident on the liquid crystal layer LC. 
     According to such a third configuration example, the same effects as those of the first configuration example are obtained. Even when the light absorbency of the insulating film  21  is higher than the light absorbency of the second common electrode CE 2 , the absorption of the light L 21  by the insulating film  21  can be suppressed, and a decrease in utilization efficiency of the light from the light emitting element LD can be suppressed. 
     Fourth Configuration Example 
       FIG.  15    is a cross-sectional view illustrating a fourth configuration example. A display panel PNL of a fourth configuration example illustrated in  FIG.  15    is different from the display panel PNL of the first configuration example illustrated in  FIG.  2    in that the second common electrode CE 2  does not have the opening. That is, the second common electrode CE 2  overlaps the first opening AP 1  and the first electrode portion EL 1 . 
     Similarly to the first configuration example, in such a fourth configuration example, when a voltage is applied to the pixel PX, the luminance of the scattered light increases in the vicinity of the edge E 1  of the first electrode portion EL 1 . Accordingly, in the fourth configuration example, the same effects as those of the first configuration example are obtained. 
     [Power Supply Structure] 
       FIG.  16    is a cross-sectional view illustrating a power supply structure for applying a voltage to the first common electrode CE 1  and the second common electrode CE 2 . 
     The first substrate SUB 1  includes a power supply line FL that supplies a common voltage (Vcom) and a power supply pad PD electrically connected to the power supply line FL. The power supply line FL is made of, for example, the same material as the scanning line G or the signal line S. The power supply pad PD is made of, for example, the same material as the pixel electrode PE. The power supply line FL and the power supply pad PD are provided in the non-display area NDA. In the example illustrated in  FIG.  16   , the power supply line FL is provided in the extension portion Ex. The power supply pad PD is in contact with the power supply line FL in a through-hole CH 1  penetrating the insulating films  11  and  12 . The power supply pad PD is exposed from the alignment film AL 1 . 
     In the second substrate SUB 2 , the first common electrode CE 1  includes a first connection portion CN 1  overlapping the power supply pad PD. The first connection portion CN 1  is integrally formed with each electrode portion such as the first electrode portion EL 1 . The second common electrode CE 2  includes a second connection portion CN 2  overlapping with the first connection portion CN 1 . The second connection portion CN 2  is integrally formed with each electrode portion such as the second electrode portion EL 2 . The first connection portion CN 1  is in contact with the second connection portion CN 2  in a through-hole CH 2  penetrating the insulating film  21 . Accordingly, the first connection portion CN 1  and the second connection portion CN 2  are electrically connected to each other. 
     A connection member CM is in contact with each of the power supply pad PD and the first connection portion CN 1 . Accordingly, the power supply pad PD and the first connection portion CN 1  are electrically connected to each other. Such a connection member CM is, for example, a conductive particle on which gold plating or the like is performed, and is included in the sealant SE. That is, the power supply pad PD and the first connection portion CN 1  are arranged in a region in which the sealant SE is provided, and are electrically connected to each other by the connection member CM when the first substrate SUB 1  and the second substrate SUB 2  are bonded. 
     According to such a power supply structure, when the common voltage is supplied to the power supply line FL, the common voltage can be applied to the first common electrode CE 1  via the power supply pad PD, the connection member CM, and the first connection portion CN 1 , and the same common voltage can also be applied to the second common electrode CE 2  via the second connection portion CN 2 . 
     Fifth Configuration Example 
       FIG.  17    is a cross-sectional view illustrating a fifth configuration example. A display panel PNL of the fifth configuration example illustrated in  FIG.  17    is different from the display panel PNL of the first configuration example illustrated in  FIG.  7    in that pixel electrodes are formed in two layers. The common electrode CE is a single layer, and is provided between the alignment film AL 2  and the insulating film  21  in the example illustrated in  FIG.  17   . However, in the fifth configuration example, the first common electrode CE 1  and the second common electrode CE 2  may also be provided as illustrated in  FIG.  7   . 
     A pixel PX 1  includes a switching element SW 1 , and a first pixel electrode PE 11  and a second pixel electrode PE 12  electrically connected to the switching element SW 1 . The first pixel electrode PE 11  is provided between the insulating film  12  and the liquid crystal layer LC, and is covered with the alignment film AL 1 . The second pixel electrode PE 12  is provided between the first transparent substrate  10  and the insulating film  12 . The second pixel electrode PE 12  is electrically connected to the switching element SW 1  in a through-hole CH 11  of the insulating film  11 . The first pixel electrode PE 11  is in contact with the second pixel electrode PE 12  in a through-hole CH 12  of the insulating film  12 . Thus, the first pixel electrode PE 11  and the second pixel electrode PE 12  have the same electric potential. 
     Similarly in the pixel PX 2 , a third pixel electrode PE 13  is provided between the insulating film  12  and the liquid crystal layer LC, and a fourth pixel electrode PE 14  is provided between the first transparent substrate  10  and the insulating film  12 . The third pixel electrode PE 13  and the fourth pixel electrode PE 14  are electrically connected to the switching element SW 2  and have the same electric potential. 
     Similarly in the pixel PX 3 , a fifth pixel electrode PE 15  is provided between the insulating film  12  and the liquid crystal layer LC, and a sixth pixel electrode PE 16  is provided between the first transparent substrate  10  and the insulating film  12 . The fifth pixel electrode PE 15  and the sixth pixel electrode PE 16  are electrically connected to the switching element SW 3  and have the same electric potential. 
     In the pixel PX 1 , the first pixel electrode PE 11  includes a first opening AP 11  and a first electrode portion EL 11  that defines the first opening AP 11 . The first opening AP 11  has a width W 31  along the second direction Y. The first electrode portion EL 11  has a width W 32  along the second direction Y. The second pixel electrode PE 12  includes a second opening AP 12  and a second electrode portion EL 12  that defines the second opening AP 12 . The second opening AP 12  overlaps the first electrode portion EL 11 , and the second electrode portion EL 12  overlaps the first opening AP 11 . A width of the second opening AP 12  is equal to a width W 32 , and a width of the second electrode portion EL 12  is equal to a width W 31 . The common electrode CE overlaps the first electrode portion EL 11  and the second electrode portion EL 12 . 
     In the pixel PX 2 , the third pixel electrode PE 13  includes a third opening AP 13  and a third electrode portion EL 13  that defines the third opening AP 13 . The third opening AP 13  has a width W 41  different from the width W 31  along the second direction Y. The third electrode portion EL 13  has a width W 42  different from the width W 32  along the second direction Y. 
     The fourth pixel electrode PE 14  includes a fourth opening AP 14  and a fourth electrode portion EL 14  that defines the fourth opening AP 14 . The fourth opening AP 14  overlaps the third electrode portion EL 13 , and the fourth electrode portion EL 14  overlaps the third opening AP 13 . A width of the fourth opening AP 14  is equal to the width W 42 , and a width of the fourth electrode portion EL 14  is equal to the width W 41 . The common electrode CE overlaps the third electrode portion EL 13  and the fourth electrode portion EL 14 . 
     The first pixel electrode PE 11  is provided between the light emitting element LD and the third pixel electrode PE 13  along the second direction Y. The first opening AP 11  is provided between the light emitting element LD and the third opening AP 13  along the second direction Y. The width W 41  of the third opening AP 13  is smaller than the width W 31  of the first opening AP 11 . The first electrode portion EL 11  is provided between the light emitting element LD and the third electrode portion EL 13  along the second direction Y. The width W 42  of the third electrode portion EL 13  is smaller than the width W 32  of the first electrode portion EL 11 . 
     The number of third openings AP 13  in the third pixel electrode PE 13  is larger than the number of first openings AP 11  in the first pixel electrode PE 11 . The number of edges of the third electrode portion EL 13  that defines the third opening AP 13  is larger than the number of edges of the first electrode portion EL 11  that defines the first opening AP 11 . That is, the third pixel electrode PE 13  is more subdivided than the first pixel electrode PE 11 . 
     In such a fifth configuration example, the same effects as those of the above-described first configuration example are also obtained. 
     [Power Supply Structure] 
       FIG.  18    is a cross-sectional view illustrating a power supply structure for applying a voltage to the common electrode CE illustrated in  FIG.  17   . 
     The first substrate SUB 1  includes the power supply line FL that supplies the common voltage (Vcom), a connection portion CN electrically connected to the power supply line FL, and the power supply pad PD electrically connected to the connection portion CN. The power supply line FL is made of, for example, the same material as the scanning line G or the signal line S. The connection portion CN is made of, for example, the same material as the second pixel electrode PE 12 , but is electrically insulated from the second pixel electrode PE 12 . The power supply pad PD is made of, for example, the same material as the first pixel electrode PE 11 , but is electrically insulated from the first pixel electrode PE 11 . The power supply line FL, the connection portion CN, and the power supply pad PD are provided in the non-display area NDA. The connection portion CN is in contact with the power supply line FL, and the power supply pad PD is in contact with the connection portion CN in a through-hole CH 3  penetrating the insulating film  12 . The power supply pad PD is exposed from the alignment film AL 1 . 
     The common electrode CE overlaps the power supply pad PD in the non-display area NDA. The connection member CM included in the sealant SE is in contact with each of the power supply pad PD and the common electrode CE. Accordingly, the power supply pad PD and the common electrode CE are electrically connected to each other. 
     According to such a power supply structure, when the common voltage is supplied to the power supply line FL, the common voltage can be applied to the common electrode CE via the connection portion CN, the power supply pad PD, and the connection member CM. 
     In the present embodiment, in the above-described first configuration example, the second transparent substrate  20  corresponds to a transparent substrate, the first common electrode CE 1  corresponds to a first transparent electrode, and the second common electrode CE 2  corresponds to a second transparent electrode. In the fifth configuration example, the first transparent substrate  10  corresponds to a transparent substrate, the first pixel electrode PE 11  corresponds to a first transparent electrode, and the second pixel electrode PE 12  corresponds to a second transparent electrode. 
     As described above, according to the present embodiment, it is possible to provide a display device capable of suppressing deterioration in display quality. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions. 
     An example of the display device obtained from the configurations disclosed in the specification will be appended below. 
     (1) A display device including: 
     a first substrate including a first transparent substrate, a switching element, and a pixel electrode electrically connected to the switching element; 
     a second substrate including a second transparent substrate, a first common electrode, a second common electrode having the same electric potential as the first common electrode, and an insulating film disposed between the first common electrode and the second common electrode; and 
     a liquid crystal layer that is disposed between the first substrate and the second substrate, and contains polymers and liquid crystal molecules, 
     wherein the first common electrode is disposed between the liquid crystal layer and the insulating film, and includes a first opening and a first electrode portion, and 
     the second common electrode is disposed between the insulating film and the second transparent substrate, and includes a second electrode portion overlapping the first opening. 
     (2) The display device according to (1), wherein the second common electrode includes a second opening overlapping the first electrode portion.
 
(3) The display device according to any one of (1) and (2),
 
     wherein the first common electrode includes a third opening and a third electrode portion, 
     the second common electrode includes a fourth electrode portion overlapping the third opening, and 
     a width of the third opening is different from a width of the first opening. 
     (4) The display device according to (3), wherein the second common electrode includes a fourth opening overlapping the third electrode portion.
 
(5) The display device according to any one of (3) and (4), further including a light emitting element,
 
     wherein the second transparent substrate includes a side surface facing the light emitting element, 
     the first opening is disposed between the light emitting element and the third opening, and 
     the width of the third opening is smaller than the width of the first opening. 
     (6) The display device according to any one of (1) to (5), 
     wherein the second substrate includes a transparent layer disposed between the second electrode portion and the second transparent substrate, and 
     the transparent layer is in contact with the second transparent substrate, and has a refractive index lower than the second transparent substrate. 
     (7) The display device according to (2), 
     wherein the second substrate includes a transparent layer disposed between the insulating film and the second transparent substrate in the second opening, and 
     the transparent layer is in contact with the second transparent substrate, and has a refractive index lower than the second transparent substrate. 
     (8) The display device according to any one of (1) to (7), further including a connection member, 
     wherein the first substrate includes a power supply pad, 
     the first common electrode includes a first connection portion overlapping the power supply pad, 
     the second common electrode includes a second connection portion overlapping the first connection portion, 
     the first connection portion is in contact with the second connection portion in a through-hole of the insulating film, and 
     the connection member electrically connects the power supply pad and the first connection portion. 
     (9) The display device according to (8), further including a sealant that bonds the first substrate and the second substrate, 
     wherein the connection member is included in the sealant. 
     (10) A display device including: 
     a first substrate including a first transparent substrate, a switching element, a first pixel electrode and a second pixel electrode electrically connected to the switching element, and an insulating film disposed between the first pixel electrode and the second pixel electrode; 
     a second substrate including a second transparent substrate, and a common electrode; and 
     a liquid crystal layer that is disposed between the first substrate and the second substrate, and contains polymers and liquid crystal molecules, 
     wherein the first pixel electrode is disposed between the insulating film and the liquid crystal layer, and includes a first opening and a first electrode portion, and 
     the second pixel electrode is disposed between the first transparent substrate and the insulating film, and includes a second electrode portion overlapping the first opening. 
     (11) The display device according to (10), wherein the second pixel electrode includes a second opening overlapping the first electrode portion.
 
(12) The display device according to any one of (10) and (11),
 
     wherein the first substrate includes a third pixel electrode disposed between the insulating film and the liquid crystal layer, and a fourth pixel electrode that is disposed between the first transparent substrate and the insulating film and has the same electric potential as the third pixel electrode, 
     the third pixel electrode includes a third opening and a third electrode portion, 
     the fourth pixel electrode includes a fourth electrode portion overlapping the third opening, and 
     a width of the third opening is different from a width of the first opening. 
     (13) The display device according to (12), wherein the fourth pixel electrode includes a fourth opening overlapping the third electrode portion.
 
(14) The display device according to any one of (12) and (13), further including a light emitting element,
 
     wherein the second transparent substrate includes a side surface facing the light emitting element, 
     the first opening is disposed between the light emitting element and the third opening, and 
     the width of the third opening is smaller than the width of the first opening. 
     (15) The display device according to any one of (10) to (14), wherein the second pixel electrode is in contact with the first pixel electrode in a through-hole of the insulating film.
 
(16) A display device including:
 
     a first substrate; 
     a second substrate; 
     a liquid crystal layer that is disposed between the first substrate and the second substrate, and contains polymers and liquid crystal molecules; and 
     a light emitting element facing a side surface of the second substrate, 
     wherein the first substrate or the second substrate includes a transparent substrate, a first transparent electrode, a second transparent electrode having the same electric potential as the first transparent electrode, and an insulating film disposed between the first transparent electrode and the second transparent electrode, 
     each of the first transparent electrode and the second transparent electrode includes a plurality of openings, 
     the openings of the first transparent electrode and the openings of the second transparent electrode do not overlap each other, and 
     the first transparent electrode includes a first opening and a third opening, and 
     the first opening is disposed between the light emitting element and the third opening, and has a width larger than the third opening.