Patent Publication Number: US-2022221644-A1

Title: Display device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation Application of PCT Application No. PCT/JP2020/029798, filed Aug. 4, 2020 and based upon and claiming the benefit of priority from Japanese Patent Application No. 2019-181999, filed Oct. 2, 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 modulating element exhibiting scattering property or transparency to light have been proposed. In an example, the light modulating element includes a polymer dispersed liquid crystal layer as a light modulating layer. The light modulating element is disposed behind a light guide and scatters incident light from a side surface of the light guide. 
     The light emitted from a plurality of light emitting elements arranged at intervals propagates inside the light guide while diffusing. In an area near the light emitting element in the light guide, the light from each light emitting element may not sufficiently mix with each other. In this case, brightness and darkness of light may be visually recognized as non-uniformity in stripe. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view illustrating a configuration example of a display device DSP according to an embodiment. 
         FIG. 2  is a cross-sectional view illustrating a configuration example of a display panel PNL illustrated in  FIG. 1 . 
         FIG. 3  is a perspective view illustrating a configuration example of a first light emitting module  100  illustrated in  FIG. 1 . 
         FIG. 4  is a perspective view illustrating a configuration example of a first light source  111  and a second light source  112  illustrated in  FIG. 3 . 
         FIG. 5  is a plan view illustrating a state of propagation of light emitted from each light source  110  of the first light emitting module  100 . 
         FIG. 6  is a diagram for explaining local dimming drive of the first light emitting module  100 . 
         FIG. 7  is a diagram for explaining local dimming drive of a color screen. 
         FIG. 8  is a diagram for explaining another local dimming drive of the color screen. 
         FIG. 9  is a diagram for explaining another local dimming drive of the first light emitting module  100 . 
         FIG. 10  is a cross-sectional view illustrating a configuration example of the display device DSP including the first light emitting module  100  and a second light emitting module  200 . 
         FIG. 11  is a cross-sectional view illustrating another configuration example of the display device DSP including the first light emitting module  100  and the second light emitting module  200 . 
     
    
    
     DETAILED DESCRIPTION 
     According to one embodiment, a display device includes: a display panel having a first side surface extending along a first direction and including a polymer dispersed liquid crystal layer; and a first light emitting module provided along the first side surface, wherein the first light emitting module includes: a plurality of first light sources arranged in the first direction; a plurality of second light sources arranged in the first direction; a first light guide provided between the plurality of first light sources and the first side surface; and a second light guide provided between the plurality of second light sources and the first side surface, and an end surface of the first light guide and an end surface of the second light guide face each other with an air layer interposed therebetween. 
     According to an embodiment, it is possible to provide a display device capable of suppressing deterioration in display quality. 
     Embodiments will be described hereinafter with reference to the accompanying drawings. The disclosure is merely an example, and proper changes within the spirit of the invention, which are easily conceivable by a skilled person, are included in the scope of the invention as a matter of course. In addition, in some cases, in order to make the description clearer, the widths, thicknesses, shapes, etc., of the respective parts are schematically illustrated in the drawings, compared to the actual modes. However, the schematic illustration is merely an example, and adds no restrictions to the interpretation of the invention. Besides, in the specification and drawings, the same or similar elements as or to those described in connection with preceding drawings or those exhibiting similar functions are denoted by like reference numerals, and a detailed description thereof is omitted unless otherwise necessary. 
       FIG. 1  is a plan view illustrating a configuration example of a display device DSP of the present embodiment. In an example, the first direction X, the second direction Y, and the 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. In the present embodiment, viewing an X-Y plane defined by the first direction X and the second direction Y is referred to as a planar view. 
     The display device DSP includes a display panel PNL including a polymer dispersed liquid crystal layer (hereinafter, simply referred to as a liquid crystal layer LC), a wiring substrate  1 , an IC chip  2 , a first light emitting module  100 , and a second light emitting module  200 . The display panel PNL has a pair of side surfaces Ell and Ell extending along the first direction X and a pair of side surfaces E 13  and E 14  extending along the second direction Y. In the example illustrated in  FIG. 1 , the side surfaces Ell and Ell are side surfaces formed along a long side of the display panel PNL, and the side surfaces E 13  and E 14  are side surfaces formed along a short side of the display panel PNL. 
     The display panel PNL includes a first substrate SUB 1 , a second substrate SUB 2 , a liquid crystal layer LC, and a seal SE. The first substrate SUB 1  and the second substrate SUB 2  overlap each other in a planar view. The first substrate SUB 1  and the second substrate SUB 2  are adhered by the seal 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 seal SE. 
     As schematically shown in an enlarged manner in  FIG. 1 , the liquid crystal layer LC contains a polymer  31  and a liquid crystal molecule  32 . In an example, the polymer  31  is a liquid crystalline polymer. The polymers  31  are formed in a streak shape extending along the first direction X and are arranged in the second direction Y. The liquid crystal molecules  32  are dispersed in the gaps between the polymers  31 , and are aligned so that their long axes are along the first direction X. Each of the polymer  31  and the liquid crystal molecule  32  has optical anisotropy or refractive anisotropy. The responsiveness of the polymer  31  to the electric field is lower than the responsiveness of the liquid crystal molecule  32  to the electric field. 
     In an example, an alignment direction of the polymer  31  hardly changes regardless of the presence or absence of the electric field. On the other hand, an alignment direction of the liquid crystal molecule  32  changes according to the electric field in a state where 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, the optical axes of the polymer  31  and the liquid crystal molecule  32  are parallel to each other, and the 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 polymer  31  and the liquid crystal molecule  32  cross 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 portion DA that displays an image, and a frame-shaped non-display portion NDA that surrounds the display portion DA. The seal SE is located in the non-display portion NDA. The display portion 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 a scanning line G and a signal line 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 a plurality of pixel electrodes PE. The liquid crystal layer LC (in particular, liquid crystal molecule  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 potential as the common electrode CE and an electrode having the same 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 substrate  1  or the IC chip  2 . 
     In the display panel PNL, the second substrate SUB 2  has a first side surface E 21  and a second side surface E 22  opposite to the first side surface E 21 . The first side surface E 21  and the second side surface E 22  extend along the first direction X. In the example illustrated in  FIG. 1 , the first side surface E 21  and the second side surface E 22  are side surfaces formed along the long side of the second substrate SUB 2 , but may be side surfaces formed along the short side of the second substrate SUB 2 . 
     The first substrate SUB 1  includes a first extending portion Ex 1  and a second extending portion Ex 2  on the opposite side of the first extending portion Ex 1  as portions not being superimposed on the second substrate SUB 2 . The first extending portion Ex 1  corresponds to a portion of the first substrate SUB 1  extending in the second direction Y from the first side surface E 21 . The second extending portion Ex 2  corresponds to a portion of the first substrate SUB 1  extending in the second direction Y from the second side surface E 22 . In a planar view, the display portion DA and the second substrate SUB 2  are located between the first extending portion Ex 1  and the second extending portion Ex 2 . 
     The wiring substrate  1  and the IC chip  2  are mounted on the first extending portion Ex 1 . The wiring substrate  1  is, for example, a bendable flexible printed circuit board. The IC chip  2  incorporates, for example, a display driver that outputs a signal necessary for image display. Note that the IC chip  2  may be mounted on the wiring substrate  1 . In the example illustrated in  FIG. 1 , a plurality of wiring substrates  1  are applied, but a single wiring substrate  1  may be applied. In addition, although a plurality of IC chips  2  are applied, a single IC chip  2  may be applied. 
     Although details of the first light emitting module  100  and the second light emitting module  200  will be described later, each of the first light emitting module  100  and the second light emitting module  200  is provided along a side surface (or an end portion) of the display panel PNL. In the example illustrated in  FIG. 1 , the first light emitting module  100  overlaps the first extending portion Ex 1  in a planar view, is provided along the first side surface E 21  of the second substrate SUB 2 , and emits light toward the first side surface E 21 . The second light emitting module  200  overlaps the second extending portion Ex 2  in a planar view, is provided along the second side surface E 22  of the second substrate SUB 2 , and emits light toward the second side surface E 22 . 
     Note that the first light emitting module  100  and the second light emitting module  200  may be provided along other side surfaces of the display panel PNL, for example, may be provided along other side surfaces E 13  and E 14 . The side surfaces E 13  and E 14  include a side surface of the first substrate SUB 1  and a side surface of the second substrate SUB 2 . In this case, the first light emitting module  100  may emit light toward any of the side surfaces of the first substrate SUB 1  and the second substrate SUB 2 , or may emit light toward both the side surfaces of the first substrate SUB 1  and the second substrate SUB 2 . However, when the first light emitting module  100  and the second light emitting module  200  are provided along the side surfaces E 13  and E 14 , respectively, the polymer  31  of the liquid crystal layer LC is formed in a streak shape extending along the second direction Y, and the liquid crystal molecule  32  is aligned so that its long axis is along the second direction Y. 
     Although  FIG. 1  illustrates an example in which the display device DSP includes the first light emitting module  100  and the second light emitting module  200 , the display device DSP may include any one of the first light emitting module  100  and the second light emitting module  200 . 
       FIG. 2  is a cross-sectional view illustrating a configuration example of the display panel PNL illustrated in  FIG. 1 . 
     The first substrate SUB 1  includes a transparent substrate  10 , insulating films  11  and  12 , a capacitive electrode  13 , a switching element SW, a pixel electrode PE, and an alignment film AL 1 . The transparent substrate  10  includes a main surface (outer surface)  10 A and a main surface (inner surface)  10 B opposite to the main surface  10 A. The switching element SW is provided on the main surface  10 B side. The insulating film  11  is provided on the main surface  10 B and covers the switching element SW. Note that the scanning line G and the signal line S illustrated in  FIG. 1  are provided between the transparent substrate  10  and the insulating film  11 , but are not illustrated here. The capacitive electrode  13  is provided between the insulating films  11  and  12 . The pixel electrode PE is provided for each pixel PX between the insulating film  12  and the alignment film AL 1 . That is, the capacitive electrode  13  is provided between the transparent substrate  10  and the pixel electrode PE. The pixel electrode PE is electrically connected to the switching element SW via an opening OP of the capacitive electrode  13 . The pixel electrode PE overlaps the capacitive electrode  13  with the insulating film  12  interposed therebetween to form a 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 transparent substrate  20 , a common electrode CE, and an alignment film AL 2 . The transparent substrate  20  includes a main surface (inner surface)  20 A and a main surface (outer surface)  20 B opposite to the main surface  20 A. The main surface  20 A of the transparent substrate  20  faces the main surface  10 B of the transparent substrate  10 . The common electrode CE is provided on the main surface  20 A. The alignment film AL 2  covers the common electrode CE. The alignment film AL 2  is in contact with the liquid crystal layer LC. In the second substrate SUB 2 , a light-shielding layer may be provided directly above the switching element SW, the scanning line G, and the signal line S. A transparent insulating film may be provided between the transparent substrate  20  and the common electrode CE or between the common electrode CE and the alignment film AL 2 . The common electrode CE is disposed over a plurality of pixels PX and faces the plurality of pixel electrodes PE in the third direction Z. The common electrode CE is electrically connected to the capacitive electrode  13 , and has the same potential as the capacitive electrode  13 . 
     The liquid crystal layer LC is located between the pixel electrode PE and the common electrode CE. 
     The transparent substrates  10  and  20  are, for example, glass substrates, but may be insulating substrates such as plastic substrates. The insulating film  11  contains, for example, a transparent inorganic insulating film such as silicon oxide, silicon nitride, or silicon oxynitride, and a transparent organic insulating film such as acrylic resin. The insulating film  12  is a transparent inorganic insulating film such as silicon nitride. The capacitive electrode  13 , the pixel electrode PE, and the common electrode CE are transparent electrodes formed of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO). The alignment films AL 1  and AL 2  are horizontal alignment films having an alignment restriction force substantially parallel to the X-Y plane. In an example, the alignment films AL 1  and AL 2  are subjected to alignment treatment along the first direction X. The alignment treatment may be rubbing treatment or photo-alignment treatment. 
     Next, the first light emitting module  100  and the second light emitting module  200  will be described. The first light emitting module  100  and the second light emitting module  200  are configured substantially similarly, and the first light emitting module  100  will be described below, and the description of the second light emitting module  200  will be omitted. 
       FIG. 3  is a perspective view illustrating a configuration example of the first light emitting module  100  illustrated in  FIG. 1 . The first light emitting module  100  includes a wiring substrate  101 , an adhesive layer  102 , a plurality of light sources  110 , and a plurality of light guides (prism lenses)  120 . Note that the number of light sources  110  and the number of light guides  120  included in the first light emitting module  100  are not limited to the illustrated example. A part of the display panel PNL is indicated by one-dot chain line. 
     The plurality of light sources  110  are arranged at intervals along the first direction X and electrically connected to the wiring substrate  101 . Preferably, the plurality of light sources  110  are arranged at regular intervals. The light source  110  basically has the same specification, and is, for example, a white light source that emits white light. Examples of the light source applicable to the present embodiment include a light emitting element incorporating a red light emitting chip, a green light emitting chip, and a blue light emitting chip, and a light emitting element incorporating a blue light emitting chip and a yellow phosphor. The light emitting chip of each color is, for example, a light emitting diode. The light-emitting chip emits light in a point shape as referred to as a point source. The presence of the light emitting chip can be recognized as a light emitting point that emits light in a point shape when light is emitted. 
     The plurality of light guides  120  are made of resin, for example, are each formed in a transparent rod shape, and extend along the first direction X. The light guides  120  basically have the same shape, and have the same length L along the first direction X. The plurality of light guides  120  are arranged along the first direction X and adhered to the wiring substrate  101  by the adhesive layer  102 . The two adjacent light guides  120  are not adhered, and are arranged so that their end surfaces face each other with an air layer AR interposed therebetween. 
     The plurality of light sources  110  and one light guide  120  constitute one segment. The number of light sources  110  facing one light guide  120  is the same in each segment. In each segment, the number of light sources  110  facing one light guide  120  is 2 to 4. 
     The plurality of light sources  110  include a first light sources  111  and a second light sources  112 . The plurality of light guides  120  include a first light guide  121  and a second light guide  122 . In the example illustrated in  FIG. 3 , the two first light sources  111  face the first light guide  121  in the second direction Y. In addition, the first light guide  121  is located between the first side surface E 21  of the display panel PNL and the plurality of first light sources  111  in the second direction Y. The two second light sources  112  face the second light guide  122  in the second direction Y. In addition, the second light guide  122  is located between the first side surface E 21  of the display panel PNL and the plurality of second light sources  112  in the second direction Y. The end surface  121 A of the first light guide  121  and the end surface  122 B of the second light guide  122  face each other with the air layer AR interposed therebetween. 
     An interval D 1  between the two first light sources  111  is equal to an interval D 2  between the two second light sources  112 . An interval D 3  between the first light source  111  and the second light source  112  adjacent to each other in the first direction X is equal to or less than the interval D 1 . An interval D 4  between the end surface  121 A and the end surface  122 B, that is, a thickness of the air layer AR along the first direction X is smaller than any of the intervals D 1  to D 3 . Here, the interval is a distance along the first direction X. For example, the interval D 4  is 1 mm or less. 
     Although the illustrated first light guide  121  is separated from the second light guide  122 , it is considered that the air layer AR is substantially interposed between the first light guide  121  and the second light guide  122  even when the first light guide  121  and the second light guide  122  are arranged so as to be in contact with each other without an adhesive interposed therebetween. 
       FIG. 4  is a perspective view illustrating a configuration example of the first light source  111  and the second light source  112  illustrated in  FIG. 3 . In  FIG. 4 , the first light guide  121  and the second light guide  122  are indicated by dotted lines, and the display panel PNL is indicated by one-dot chain lines. The first light source  111  has a light-emitting surface EM 1  surrounded by a frame F 1  in an X-Z plane defined by the first direction X and the third direction Z. The first light source  111  has a red light emitting point R 1 , a green light emitting point G 1 , and a blue light emitting point B 1  on the light-emitting surface EM 1 . In the example illustrated in  FIG. 4 , the red light emitting point R 1 , the green light emitting point G 1 , and the blue light emitting point B 1  are arranged so as to correspond to vertices of a triangle in the X-Z plane, but may be arranged on the same straight line along the first direction X. The second light source  112  is also configured similarly to the first light source  111 , and the second light source  112  has a red light emitting point R 2 , a green light emitting point G 2 , and a blue light emitting point B 2  on a light-emitting surface EM 2  surrounded by a frame F 2 . 
     The first light guide  121  is provided between the first light sources  111  and the first side surface E 21  of the display panel PNL. The second light guide  122  is provided between the second light sources  112  and the first side surface E 21 . 
     In the first light source  111 , the red light emitted from the red light emitting point R 1 , the green light emitted from the green light emitting point G 1 , and the blue light emitted from the blue light emitting point B 1  are incident on the first light guide  121 . The light incident on the first light guide  121  is appropriately diffused in the first light guide  121 , and is incident on the display panel PNL. Similarly, the light emitted from the second light source  112  is incident on the display panel PNL via the second light guide  122 . 
       FIG. 5  is a plan view illustrating a state of propagation of light emitted from each light source  110  of the first light emitting module  100 . Here, the description will be given focusing on three segments SG 1  to SG 3  of the first light emitting module  100 . The segments SG 1  to SG 3  are arranged in this order in the first direction X. The segment SG 1  includes first light sources  111  and a first light guide  121 , the segment SG 2  includes second light sources  112  and a second light guide  122 , and the segment SG 3  includes third light sources  113  and a third light guide  123 . The display portion DA includes an area DA 1  mainly illuminated by the segment SG 1 , an area DA 2  mainly illuminated by the segment SG 2 , and an area DA 3  mainly illuminated by the segment SG 3 . The areas DA 1  to DA 3  are arranged in this order in the first direction X. 
     For example, when attention is paid to the segment SG 1 , the light beams emitted from the adjacent first light sources  111 , respectively, are incident on the first light guide  121 , appropriately mixed in the first light guide  121 , diffused, incident on the display panel PNL, and reach the area DA 1 . The light reached the end surfaces  121 A and  121 B of the first light guide  121  is totally reflected and reaches the area DA 1 . Also in the segment SG 2  and the segment SG 3 , similarly to the segment SG 1 , the light emitted from the second light source  112  reaches the area DA 2 , and the light emitted from the third light source  113  reaches the area DA 3 . 
       FIG. 6  is a diagram for explaining local dimming drive of the first light emitting module  100 . Here, it is assumed that the areas DA 1  and DA 3  are non-illumination areas, the area DA 2  includes an illumination area DA 21 , and a bright image is displayed in the illumination area DA 21 . In this case, in the first light emitting module  100 , the segments SG 1  and SG 3  are set to a non-lighting state (OFF), and the segment SG 2  is set to a lighting state (ON). 
     In the segment SG 2 , the light beams emitted from the adjacent second light sources  112 , respectively, are incident on the second light guide  122 , appropriately mixed in the second light guide  122 , diffused, incident on the display panel PNL, and reach the illumination area DA 21  of the area DA 2 . At this time, the light reached the end surfaces  122 A and  122 B of the second light guide  122  is totally reflected and reaches the illumination area DA 21 . Therefore, the spread of the light emitted from the second light source  112  to the adjacent areas DA 1  and DA 3  is suppressed. 
     In order to compare with the present embodiment, a first comparative example and a second comparative example will be examined. In the first comparative example, a first light guide  121 , a second light guide  122 , and a third light guide  123  are replaced with a single light guide. In the second comparative example, an end surface  121 A and an end surface  122 B are adhered by an adhesive, an end surface  122 A and an end surface  123 B are adhered by an adhesive, and the adhesive has a refractive index equivalent to that of each light guide. In the first comparative example and the second comparative example, the light reached the vicinity of the end surfaces  122 A and  122 B of the present embodiment is diffused while traveling straight without being totally reflected. That is, the light reached the vicinity of the end surface  122 A of the present embodiment reaches the area DA 3 , and the light reached the vicinity of the end surface  122 B of the present embodiment reaches the area DA 1 . Therefore, the light emitted from the second light source  112  reaches not only the illumination area DA 21  but also the periphery thereof, leading to a decrease in the contrast ratio. 
     According to the present embodiment, since the spread of the light emitted from the second light source  112  is suppressed, the amount of light reached the illumination area DA 21  can be increased, the amount of light reached the periphery of the illumination area DA 21  can be reduced, and a decrease in the contrast ratio can be suppressed. Therefore, degradation of display quality can be suppressed. 
     In addition, the light emitted from the second light source  112  can be guided to the illumination area DA 21 , and the utilization efficiency of the light can be improved. 
       FIG. 7  is a diagram for explaining local dimming drive of a color screen. Here, it is assumed that areas DA 2  and DA 4  are non-illumination areas, an area DA 1  includes an illumination area DA 11 , an area DA 3  includes an illumination area DA 31 , a green image is displayed in the illumination area DA 11 , and a red image is displayed in the illumination area DA 31 . In this case, in the first light emitting module  100 , the segments SG 2  and SG 4  are set to the non-lighting state (OFF), and the segments SG 1  and SG 3  are set to the lighting state (ON). In the segment SG 1 , only the green light-emitting chip of the first light source  111  emits light, and in the segment SG 3 , only the red light-emitting chip of the third light source  113  emits light. 
     In the segment SG 1 , the green light emitted from each of the first light sources  111  reaches an illumination area DA 11  via the first light guide  121 . At this time, the green light reached the end surface  121 A of the first light guide  121  is totally reflected and reaches the illumination area DA 11 . Therefore, the spread of the green light emitted from the first light source  111  to the areas DA 1  to DA 4  is suppressed. 
     In the segment SG 3 , the red light emitted from each of the third light sources  113  reaches the illumination area DA 31  via the third light guide  123 . At this time, the red light reached the end surface  123 B of the third light guide  123  is totally reflected and reaches the illumination area DA 31 . Therefore, the spread of the red light emitted from the third light source  113  to the areas DA 1  and DA 2  is suppressed. 
     In the first comparative example and the second comparative example described above, when the green light of the first light source  111  reaches the vicinity of the end surface  121 A of the present embodiment, the green light is diffused while traveling straight without being totally reflected. Such green light may reach the illumination area DA 31 . In the illumination area DA 31 , the green light of the first light source  111  and the red light of the third light source  113  are mixed, and a color purity of a red image in the illumination area DA 31  decreases. Similarly, the red light of the third light source  113  may reach the illumination area DA 11 . In the illumination area DA 11 , the green light of the first light source  111  and the red light of the third light source  113  are mixed, and a color purity of a green image in the illumination area DA 11  decreases. 
     According to the present embodiment, the spread of the green light emitted from the first light source  111  is suppressed, and the spread of the red light emitted from the third light source  113  is suppressed. Therefore, color mixing in the illumination areas DA 11  and DA 31  is suppressed, and a decrease in color purity of an image displayed in each illumination area can be suppressed. In addition, since a decrease in the color purity of each of the red image, the green image, and the blue image is suppressed, a color reproduction range of the color image that can be displayed on the display portion DA can be expanded. Therefore, the display quality can be improved. 
       FIG. 8  is a diagram for explaining another local dimming drive of the color screen. The display portion DA is located between the first light emitting module  100  and the second light emitting module  200 . The first light emitting module  100  includes segments SG 101  to SG 104 , and the second light emitting module  200  includes segments SG 201  to SG 204 . 
     As illustrated in detail, in the first light emitting module  100 , the segment SG 101  includes the light sources  111  and the light guide  121 , the segment SG 102  includes the light sources  112  and the light guide  122 , the segment SG 103  includes the light sources  113  and the light guide  123 , and the segment SG 104  includes the light sources  114  and the light guide  124 . In the second light emitting module  200 , the segment SG 201  includes the light sources  211  and the light guide  221 , the segment SG 202  includes the light sources  212  and the light guide  222 , the segment SG 203  includes the light sources  213  and the light guide  223 , and the segment SG 204  includes the light sources  214  and the light guide  224 . 
     Here, it is assumed that areas DA 2  and DA 4  are non-illumination areas, an area DA 1  includes illumination areas DA 11  and DA 12 , an area DA 3  includes illumination areas DA 31  and DA 32 , a green image is displayed in each of the illumination areas DA 11  and DA 12 , and a red image is displayed in each of the illumination areas DA 31  and DA 32 . 
     In the first light emitting module  100 , the segments SG 102  and SG 104  are set to a non-lighting state (OFF), the segment SG 101  is set to a lighting state (ON) in which green light is emitted, and the segment SG 103  is set to a lighting state (ON) in which red light is emitted. In the second light emitting module  200 , the segments SG 202  and SG 204  are set to the non-lighting state (OFF), the segment SG 201  is set to the lighting state (ON) in which green light is emitted, and the segment SG 203  is set to the lighting state (ON) in which red light is emitted. 
     In the segment SG 101 , the green light emitted from each of the light sources  111  reaches the illumination area DA 11  via the light guide  121 , and further travels toward the illumination area DA 12 . However, the green light from the light sources  111  attenuates as it travels in the second direction Y. Therefore, among the green light from the light sources  111 , the green light reaching the illumination area DA 12  is less than the green light reaching the illumination area DA 11 . 
     On the other hand, in the segment SG 201 , the green light emitted from each of the light sources  211  reaches the illumination area DA 12  via the light guide  221 , and further travels toward the illumination area DA 11 . That is, the illumination area DA 11  is mainly illuminated with green light from the light sources  111 , and the illumination area DA 12  is mainly illuminated with green light from the light sources  211 . Therefore, the luminance difference accompanying the attenuation of the green light from each light source is alleviated, and the display quality can be improved. 
     Similarly, in the segment SG 103 , the red light from the light sources  113  reaches the illumination area DA 31  via the light guide  123 . In the segment SG 203 , the red light from the light sources  213  reaches the illumination area DA 32  via the light guide  223 . Therefore, the luminance difference accompanying the attenuation of the red light from each light source is alleviated. Consequently, the display quality can be improved. 
       FIG. 9  is a diagram for explaining another local dimming drive of the first light emitting module  100 . The first light emitting module  100  includes segments SG 1  to SG 23 . As described above, each segment includes a plurality of light sources and one light guide, but detailed illustration is omitted. Note that the first light emitting module  100  may include a plurality of light sources provided for each segment and a light guide continuous over a plurality of segments. 
     In the local dimming drive described below, a light source control unit LCT controls the current value of each light source according to the illumination area DAW of the display portion DA. 
     In the example illustrated in  FIG. 9 , the illumination area DAW corresponds to an area mainly illuminated by the segments SG 11  to SG 13 . For example, the light source of the segment SG 12  is driven with a current value at which the luminance becomes a first luminance, and each of the light sources of the segments SG 11  and SG 13  is driven with a current value at which the luminance becomes a second luminance smaller than the first luminance. Each of the light sources of the other segments SG 1  to SG 10  and SG 14  to SG 23  is driven with a current value at which the luminance becomes smaller than the second luminance. 
     In this way, by controlling the current value of each light source, it is possible to make the illumination area DAW bright and the periphery of the illumination area DAW dark, and to suppress the decrease in the contrast ratio. 
       FIG. 10  is a cross-sectional view illustrating a configuration example of a display device DSP including the first light emitting module  100  and the second light emitting module  200 . Note that only the main part of the display panel PNL is illustrated in a simplified manner. 
     The display device DSP further includes a first cover member  30 , a second cover member  40 , a first adhesive layer AD 1  that adheres the first substrate SUB 1  and the first cover member  30 , and a second adhesive layer AD 2  that adheres the second substrate SUB 2  and the second cover member  40 . In the example illustrated in  FIG. 10 , the first cover member  30  overlaps the second extending portion Ex 2  but does not overlap the first extending portion Ex 1 . The second cover member  40  does not overlap any of the first extending portion Ex 1  and the second extending portion Ex 2 . 
     The first cover member  30  includes a main surface (outer surface)  30 A and a main surface (inner surface)  30 B opposite to the main surface  30 A. The main surface  30 B faces the main surface  10 A of the transparent substrate  10 . The first adhesive layer AD 1  adheres the transparent substrate  10  and the first cover member  30 . The second cover member  40  includes a main surface (inner surface)  40 A and a main surface (outer surface)  40 B opposite to the main surface  40 A. The main surface  40 A faces the main surface  20 B of the transparent substrate  20 . The second adhesive layer AD 2  adheres the transparent substrate  20  and the second cover member  40 . The transparent substrate  10 , the transparent substrate  20 , the first cover member  30 , and the second cover member  40  have substantially the same thickness along the third direction Z. 
     The first cover member  30  and the second cover member  40  are, for example, glass substrates, but may be insulating substrates such as plastic substrates. The first cover member  30  has a refractive index equivalent to that of the transparent substrate  10 . The first adhesive layer AD 1  has a refractive index equivalent to that of each of the transparent substrate  10  and the first cover member  30 . The second cover member  40  has a refractive index equivalent to that of the transparent substrate  20 . The second adhesive layer AD 2  has a refractive index equivalent to that of each of the transparent substrate  20  and the second cover member  40 . Note that “equivalent” here is not limited to a case where the refractive index difference is 0, and includes a case where the refractive index difference is 0.03 or less. 
     In the second substrate SUB 2 , the transparent substrate  20  has side surfaces  20 C and  20 D. The side surface  20 C substantially corresponds to the first side surface E 21  illustrated in  FIG. 1 . The side surface  20 D substantially corresponds to the second side surface E 22  illustrated in  FIG. 1 . The second cover member  40  has a third side surface  40 C and a fourth side surface  40 D. The third side surface  40 C is located directly above the first side surface  20 C, and the fourth side surface  40 D is located directly above the second side surface  20 D. 
     The first light emitting module  100  overlaps the first extending portion Ex 1 . In the first light emitting module  100 , the light source  110  is provided between the transparent substrate  10  and the wiring substrate  101  in the third direction Z. The light guide  120  is provided between the light source  110  and the first side surface  20 C and between the light source  110  and the third side surface  40 C in the second direction Y. The light guide  120  is adhered to the wiring substrate  101  by the adhesive layer  102 , and is adhered to the first substrate SUB 1  by the adhesive layer  103 . 
     The second light emitting module  200  overlaps the second extending portion Ex 2 . In the second light emitting module  200 , the light source  210  is provided between the transparent substrate  10  and the wiring substrate  201  in the third direction Z. The light guide  220  is provided between the light source  210  and the second side surface  20 D and between the light source  210  and the fourth side surface  40 D in the second direction Y. The light guide  220  is adhered to the wiring substrate  201  by the adhesive layer  202 , and is adhered to the first substrate SUB 1  by the adhesive layer  203 . 
     Next, light L 1  emitted from the light source  110  and light L 2  emitted from the light source  210  will be described. 
     The first light emitting module  100  emits light toward the first side surface  20 C and the third side surface  40 C. The light L 1  emitted from the light source  110  propagates along the direction of the arrow indicating the second direction Y, passes through the light guide  120 , enters the transparent substrate  20  from the first side surface  20 C, and enters the second cover member  40  from the third side surface  40 C. 
     Similarly, the second light emitting module  200  emits light toward the second side surface  20 D and the fourth side surface  40 D. The light L 2  emitted from the light source  210  propagates along the direction opposite to the arrow indicating the second direction Y, passes through the light guide  220 , enters the transparent substrate  20  from the second side surface  20 D, and enters the second cover member  40  from the fourth side surface  40 D. 
     The light L 1  and the light L 2  incident on the transparent substrate  20  and the second cover member  40  propagate inside the display panel PNL while being repeatedly reflected. The light L 1  and the light L 2  incident on the liquid crystal layer LC to which no voltage is applied are transmitted through the liquid crystal layer LC without being almost scattered. In addition, the light L 1  and the light L 2  incident on the liquid crystal layer LC to which the voltage is applied are scattered by the liquid crystal layer LC. The display device DSP can be observed from the main surface  30 A side and can also be observed from the main surface  40 B side. In addition, even when the display device DSP is observed from the main surface  30 A side or the main surface  40 B side, the background of the display device DSP can be observed via the display device DSP. 
       FIG. 11  is a cross-sectional view illustrating another configuration example of the display device DSP including the first light emitting module  100  and the second light emitting module  200 . Note that only the main part of the display panel PNL is illustrated in a simplified manner. 
     The configuration example illustrated in  FIG. 11  is different from the configuration example illustrated in  FIG. 10  in that the first cover member  30  includes the third extending portion Ex 3  instead of the second extending portion Ex 2  of the first substrate SUB 1 . The second cover member  40  does not overlap any of the first extending portion Ex 1  and the third extending portion Ex 3 . 
     In the first substrate SUB 1 , the transparent substrate  10  has the fifth side surface  10 D. The second side surface  20 D is located directly above the fifth side surface  10 D, and the fourth side surface  40 D is located directly above the second side surface  20 D. 
     The second light emitting module  200  overlaps the third extending portion Ex 3 . In the second light emitting module  200 , the light source  210  is provided between the first cover member  30  and the wiring substrate  201  in the third direction Z. The light guide  220  is provided between the light source  210  and the second side surface  20 D and between the light source  210  and the fifth side surface  10 D in the second direction Y. The light guide  220  is adhered to the wiring substrate  201  by the adhesive layer  202 , and is adhered to the first cover member  30  by the adhesive layer  203 . 
     Such a second light emitting module  200  emits light toward the second side surface  20 D and the fifth side surface  10 D. The light L 2  emitted from the light source  210  propagates along the direction opposite to the arrow indicating the second direction Y, passes through the light guide  220 , enters the transparent substrate  20  from the second side surface  20 D, and enters the transparent substrate  10  from the fifth side surface  10 D. The light L 1  incident on the transparent substrate  20  and the second cover member  40  and the light L 2  incident on the transparent substrates  10  and  20  propagate inside the display panel PNL while being repeatedly reflected. 
     Even in such a configuration example, observation can be performed similarly to the configuration example illustrated in  FIG. 10 . 
     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.