Patent Publication Number: US-2022223647-A1

Title: Light emitting element array

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a continuation of U.S. patent application Ser. No. 17/018,437, filed on Sep. 11, 2020, which application claims priority from Japanese Application No. 2019-166539, filed on Sep. 12, 2019, the contents of which are incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     1. Technical Field 
     What is disclosed herein relates to a display device. 
     2. Description of the Related Art 
     Displays with micro light emitting diodes (micro LEDs) serving as display elements have recently attracted attention (refer to Japanese Translation of PCT International Application Publication No. 2017-529557 (JP-T-2017-529557), for example). A plurality of LEDs are mounted on an array substrate (or a driver backplane in JP-T-2017-529557). WO 2015/111523 describes an anisotropic optical film used for a liquid crystal display panel. 
     Such a display with micro LEDs is expected to provide higher relative luminance of light in a direction in which an observer highly frequently observes the display, that is, in the normal direction of the array substrate. If the anisotropic optical film to be applied for a liquid crystal display panel is used for a display with LEDs without any change, the display property may possibly deteriorate. 
     SUMMARY 
     According to an aspect, a display device includes: a substrate; a plurality of pixels provided to the substrate; a plurality of light emitting elements provided to the pixels; a first anisotropic diffusion layer facing the substrate with the light emitting elements interposed between the first anisotropic diffusion layer and the substrate; and a second anisotropic diffusion layer. The first anisotropic diffusion layer and the second anisotropic diffusion layer are layered. The first anisotropic diffusion layer and the second anisotropic diffusion layer each include a region in an in-plane direction including a high refractive index region and a low refractive index region in a mixed manner. An absolute value of a first angle formed by a boundary between the high refractive index region and the low refractive index region of the first anisotropic diffusion layer and a direction perpendicular to the substrate is different from an absolute value of a second angle formed by a boundary between the high refractive index region and the low refractive index region of the second anisotropic diffusion layer and the direction perpendicular to the substrate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view schematically illustrating a display device according to a first embodiment; 
         FIG. 2  is a plan view of a plurality of sub-pixels; 
         FIG. 3  is a circuit diagram of a pixel circuit; 
         FIG. 4  is a timing chart of exemplary operations of the display device; 
         FIG. 5  is a sectional view along line V-V of  FIG. 2 ; 
         FIG. 6  is a partially enlarged sectional view of a light emitting element illustrated in  FIG. 5 ; 
         FIG. 7  is a plan view schematically illustrating a first anisotropic diffusion layer included in an optical member according to the first embodiment; 
         FIG. 8  is a sectional view along line VIII-VIII′ of  FIG. 7 ; 
         FIG. 9  is a graph schematically illustrating a relation between the relative luminance of light scattered by the first anisotropic diffusion layer and the polar angle; 
         FIG. 10  is a sectional view schematically illustrating the optical member according to the first embodiment; 
         FIG. 11  is a graph schematically illustrating a relation between the relative luminance of light emitted from the display device according to the first embodiment and the polar angle; 
         FIG. 12  is a sectional view schematically illustrating an optical member according to a second embodiment; 
         FIG. 13  is a view for explaining azimuth angles of the optical member according to the second embodiment; 
         FIG. 14  is a graph schematically illustrating a relation between the relative luminance of light emitted from a display device according to the second embodiment and the polar angle; 
         FIG. 15  is a sectional view schematically illustrating an optical member according to a modification of the second embodiment; 
         FIG. 16  is a view for explaining azimuth angles of an optical member according to a third embodiment; 
         FIG. 17  is a graph schematically illustrating a relation between the relative luminance of light emitted from a display device according to the third embodiment and the polar angle; 
         FIG. 18  is a sectional view schematically illustrating a display device according to a fourth embodiment; 
         FIG. 19  is a graph schematically illustrating a relation between the relative luminance of light from a light emitting element that emits red light and the polar angle; 
         FIG. 20  is a graph schematically illustrating a relation between the relative luminance of light from a light emitting element that emits green light and the polar angle; and 
         FIG. 21  is a graph schematically illustrating a relation between the relative luminance of light from a light emitting element that emits blue light and the polar angle. 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary aspects (embodiments) to embody the present disclosure are described below in greater detail with reference to the accompanying drawings. The contents described in the embodiments are not intended to limit the present disclosure. Components described below include components easily conceivable by those skilled in the art and components substantially identical therewith. Furthermore, the components described below may be appropriately combined. What is disclosed herein is given by way of example only, and appropriate changes made without departing from the spirit of the present disclosure and easily conceivable by those skilled in the art naturally fall within the scope of the disclosure. To simplify the explanation, the drawings may possibly illustrate the width, the thickness, the shape, and other elements of each unit more schematically than the actual aspect. These elements, however, are given by way of example only and are not intended to limit interpretation of the present disclosure. In the present specification and the figures, components similar to those previously described with reference to previous figures are denoted by the same reference numerals, and detailed explanation thereof may be appropriately omitted. 
     In the present specification and the accompanying claims, to express an aspect where a first structure is disposed on a second structure, the term “on” includes both of the following cases if not specially defined: the case where the first structure is disposed directly on the second structure so as to be in contact with the second structure and the case where the first structure is disposed on the second structure with another structure interposed therebetween. 
     First Embodiment 
       FIG. 1  is a plan view schematically illustrating a display device according to a first embodiment. As illustrated in  FIG. 1 , a display device  1  includes an array substrate  2 , pixels Pix, drive circuits  12 , a drive integrated circuit (IC)  210 , and cathode wiring  60 . The array substrate  2  is a drive circuit board for driving the pixels Pix and is also called a backplane or an active matrix substrate. The array substrate  2  includes a substrate  21 , a plurality of transistors, a plurality of capacitances, and various kinds of wiring, for example. 
     As illustrated in  FIG. 1 , the display device  1  has a display region AA and a peripheral region GA. The display region AA is disposed overlapping the pixels Pix and displays an image. The peripheral region GA does not overlap the pixels Pix and is disposed outside the display region AA. 
     The pixels Pix are arrayed in a first direction Dx and a second direction Dy in the display region AA of the substrate  21 . The first direction Dx and the second direction Dy are parallel to the surface of the substrate  21 . The first direction Dx is orthogonal to the second direction Dy. The first direction Dx may intersect the second direction Dy without being orthogonal thereto. A third direction Dz is orthogonal to the first direction Dx and the second direction Dy. The third direction Dz corresponds to the normal direction of the substrate  21 , for example. In the following description, planar view indicates the positional relation when viewed in the third direction Dz. 
     The drive circuits  12  drive a plurality of gate lines (e.g., a light emission control scanning line BG, a reset control scanning line RG, an initialization control scanning line IG, and a writing control scanning line SG (refer to  FIG. 3 )) based on various control signals received from the drive IC  210 . The drive circuits  12  sequentially or simultaneously select a plurality of gate lines and supply gate drive signals to the selected gate lines. As a result, the drive circuits  12  select a plurality of pixels Pix coupled to the gate lines. 
     The drive IC  210  is a circuit that controls display on the display device  1 . The drive IC  210  is mounted on the peripheral region GA of the substrate  21  as a chip-on-glass (COG) IC. The mounting form of the drive IC  210  is not limited thereto, and the drive IC  210  may be mounted on FPCs or a rigid substrate coupled to the peripheral region GA of the substrate  21  as a chip-on-film (COF) IC. 
     The cathode wiring  60  is provided in the peripheral region GA of the substrate  21 . The cathode wiring  60  is provided surrounding the pixels Pix in the display region AA and the drive circuits  12  in the peripheral region GA. Cathodes of a plurality of light emitting elements  3  are electrically coupled to the common cathode wiring  60  and supplied with a fixed potential (e.g., a ground potential). More specifically, a cathode terminal  32  (refer to  FIG. 5 ) of the light emitting element  3  is coupled to the cathode wiring  60  via a cathode electrode  22 . 
       FIG. 2  is a plan view of a plurality of sub-pixels. As illustrated in  FIG. 2 , one pixel Pix includes a plurality of sub-pixels  49 . The pixel Pix includes a first sub-pixel  49 R, a second sub-pixel  49 G, and a third sub-pixel  49 B, for example. The first sub-pixel  49 R displays a primary color of red as the first color. The second sub-pixel  49 G displays a primary color of green as the second color. The third sub-pixel  49 B displays a primary color of blue as the third color. As illustrated in  FIG. 2 , the first sub-pixel  49 R and the third sub-pixel  49 B in one pixel Pix are aligned in the first direction Dx. The second sub-pixel  49 G and the third sub-pixel  49 B are aligned in the second direction Dy. The first color, the second color, and the third color are not limited to red, green, and blue, respectively, and may be any desired colors, such as complementary colors. In the following description, the first sub-pixel  49 R, the second sub-pixel  49 G, and the third sub-pixel  49 B are referred to as sub-pixels  49  when they need not be distinguished from one another. 
     The sub-pixels  49  each include the light emitting element  3  and an anode electrode  23 . The display device  1  displays an image by emitting different light (e.g., red, green, and blue light) from light emitting elements  3 R,  3 G, and  3 B in the first sub-pixel  49 R, the second sub-pixel  49 G, and the third sub-pixel  49 B, respectively. The light emitting elements  3  are provided in the respective sub-pixels  49 . The light emitting element  3  is a light emitting diode (LED) chip having a size of approximately 3 μm to 300 μm in planar view. An LED chip having a chip size smaller than 100 μm is called a micro LED, which is not strictly defined. The display device  1  including the micro LEDs in the respective pixels is also called a micro LED display device. The term “micro” of the micro LED is not intended to limit the size of the light emitting element  3 . 
     The light emitting elements  3  may emit different light in four or more colors. The positions of the sub-pixels  49  are not limited to the configuration illustrated in  FIG. 2 . The first sub-pixel  49 R, for example, may be adjacent to the second sub-pixel  49 G in the first direction Dx. The first sub-pixel  49 R, the second sub-pixel  49 G, and the third sub-pixel  49 B may be repeatedly arrayed in this order in the first direction Dx. 
       FIG. 3  is a circuit diagram of a pixel circuit. A pixel circuit PICA illustrated in  FIG. 3  is provided to each of the first sub-pixel  49 R, the second sub-pixel  49 G, and the third sub-pixel  49 B. The pixel circuit PICA is provided on the substrate  21  to supply a drive signal (electric current) to the light emitting element  3 . The explanation of the pixel circuit PICA with reference to  FIG. 3  is applicable to the respective pixel circuits PICA included in the first sub-pixel  49 R, the second sub-pixel  49 G, and the third sub-pixel  49 B. 
     As illustrated in  FIG. 3 , the pixel circuit PICA includes the light emitting element  3 , five transistors, and two capacitances. Specifically, the pixel circuit PICA includes a light emission control transistor BCT, an initialization transistor IST, a writing transistor SST, a reset transistor RST, and a drive transistor DRT. Some of the transistors may be shared by adjacent sub-pixels  49  of the sub-pixels  49 . The light emission control transistor BCT, for example, may be shared by three sub-pixels  49  via common wiring. The reset transistors RST may be provided in the peripheral region GA and provided for respective rows of the sub-pixels  49 , for example. In this case, the reset transistor RST is coupled to the sources of a plurality of drive transistors DRT via common wiring. 
     The transistors included in the pixel circuit PICA are n-type thin film transistors (TFTs). The present embodiment is not limited thereto, and the transistors may be p-type TFTs. To use p-type TFTs, the coupling form of power supply potential, capacitance Cs 1 , and capacitance Cs 2  may be appropriately adapted. 
     The light emission control scanning line BG is coupled to the gate of the light emission control transistor BCT. The initialization control scanning line IG is coupled to the gate of the initialization transistor IST. The writing control scanning line SG is coupled to the gate of the writing transistor SST. The reset control scanning line RG is coupled to the gate of the reset transistor RST. 
     The light emission control scanning line BG, the initialization control scanning line IG, the writing control scanning line SG, and the reset control scanning line RG are coupled to the drive circuits  12  (refer to  FIG. 1 ) provided in the peripheral region GA. The drive circuits  12  supply a light emission control signal Vbg, an initialization control signal Vig, a writing control signal Vsg, and a reset control signal Vrg to the light emission control scanning line BG, the initialization control scanning line IG, the writing control scanning line SG, and the reset control scanning line RG, respectively. 
     The drive IC  210  (refer to  FIG. 1 ) supplies video signals Vsig to the respective pixel circuits PICA of the first sub-pixel  49 R, the second sub-pixel  49 G, and the third sub-pixel  49 B in a time-division manner. A switching circuit, such as a multiplexer, is provided between each row of the first sub-pixels  49 R, the second sub-pixels  49 G, and the third sub-pixels  49 B and the drive IC  210 . The video signal Vsig is supplied to the writing transistor SST via a video signal line L 2 . The drive IC  210  supplies reset power supply potential Vrst to the reset transistor RST via a reset signal line L 3 . The drive IC  210  supplies initialization potential Vini to the initialization transistor IST via an initialization signal line L 4 . 
     The light emission control transistor BCT, the initialization transistor IST, the writing transistor SST, and the reset transistor RST each function as a switching element that selects electrical continuity and discontinuity between two nodes. The drive transistor DRT functions as an electric current control element that controls an electric current flowing through the light emitting element  3  depending on voltage between the gate and the drain. 
     The cathode (cathode terminal  32 ) of the light emitting element  3  is coupled to a cathode power supply line L 10 . The anode (anode terminal  33 ) of the light emitting element  3  is coupled to an anode power supply line L 1  via the drive transistor DRT and the light emission control transistor BCT. The anode power supply line L 1  is supplied with anode power supply potential PVDD. The cathode power supply line L 10  is supplied with cathode power supply potential PVSS. The anode power supply potential PVDD is higher than the cathode power supply potential PVSS. The cathode power supply line L 10  includes the cathode wiring  60 . Light emission operations of the light emitting element  3  will be described later. 
     The pixel circuit PICA includes the capacitance Cs 1  and the capacitance Cs 2 . The capacitance Cs 1  is holding capacitance formed between the gate and the source of the drive transistor DRT. The capacitance Cs 2  is additional capacitance formed between the cathode power supply line L 10  and both the source of the drive transistor DRT and the anode of the light emitting element  3 . 
       FIG. 4  is a timing chart of exemplary operations of the display device. Periods G 1  to G 4  illustrated in  FIG. 4  each correspond to one horizontal period. While  FIG. 4  illustrates the operations for driving the sub-pixels  49  of the first row to the sub-pixels  49  of the fourth row, the sub-pixels  49  of the fifth row to the sub-pixels  49  of the last row are subsequently driven. In the following description, a frame period  1 F indicates the period for driving the sub-pixels  49  of the first row to the sub-pixels  49  of the last row. 
     The following describes exemplary operations from period t 0  to period t 5  illustrated in  FIG. 4  in greater detail. The period t 0  is a pervious frame light emission period. In other words, in the period t 0  before processing in a certain frame period  1 F is started, the sub-pixels  49  maintain the light emission state of the previous frame. 
     The subsequent period t 1  is a source initialization period for the drive transistor DRT. Specifically, in the period t 1 , the electric potential of a light emission control scanning line BG 1  is switched to an L (low) level, and the electric potential of a reset control scanning line RG 1  is switched to an H (high) level by the control signals supplied from the drive circuits  12 . As a result, the light emission control transistor BCT is turned off (electrically discontinuous state), and the reset transistor RST is turned on (electrically continuous state). 
     The light emission control scanning line BG 1  indicates the light emission control scanning line BG coupled to the sub-pixels  49  of the first row. A light emission control scanning line BG 2  indicates the light emission control scanning line BG coupled to the sub-pixels  49  of the second row. A light emission control scanning line BG 3  indicates the light emission control scanning line BG coupled to the sub-pixels  49  of the third row. A light emission control scanning line BG 4  indicates the light emission control scanning line BG coupled to the sub-pixels  49  of the fourth row. Similarly, other scanning lines, such as the reset control scanning lines RG 1 , RG 2 , RG 3 , and RG 4 , indicate the scanning lines of the respective rows. 
     In the period t 1 , an electric current from the anode power source line L 1  is cut off by the light emission control transistor BCT in the sub-pixels  49  of the first row. Light emission from the light emitting elements  3  stops, and residual electric charges in the sub-pixels  49  flow outside through the reset transistor RST. As a result, the electric potential of the source of the drive transistor DRT is fixed at the reset power supply potential Vrst. The reset power supply potential Vrst is set so as to have a predetermined potential difference with respect to the cathode power supply potential PVSS. In this case, the potential difference between the reset power supply potential Vrst and the cathode power supply potential PVSS is smaller than the potential difference at which the light emitting element  3  starts to emit light. 
     The subsequent period t 2  is a gate initialization period for the drive transistor DRT. Specifically, in the period t 2 , the electric potential of an initialization control scanning line IG 1  is switched to the H level by the control signals supplied from the drive circuits  12 . The initialization transistor IST is turned on. In the sub-pixels  49  belonging to the first row, the electric potential of the gate of the drive transistor DRT is fixed at the initialization potential  Vini  by the initialization transistor IST. The initialization potential  Vini  has an electric potential higher than a threshold of the drive transistor DRT with respect to the reset power supply potential Vrst. As a result, the drive transistor DRT is turned on. In the period t 2 , no electric current flows through the drive transistor DRT because the light emission control transistor BCT remains off. 
     The subsequent period t 3  is an offset cancel operation period. Specifically, in the period t 3 , the electric potential of the light emission control scanning line BG 1  is switched to the H level, and the electric potential of the reset control scanning line RG 1  is switched to the L level by the control signals supplied from the drive circuits  12 . As a result, the light emission control transistor BCT is turned on, and the reset transistor RST is turned off. 
     The drive transistor DRT is in the ON state by the operations performed in the period t 2 . As a result, an electric current is supplied to the drive transistor DRT from the anode power supply line L 1  (anode power supply potential PVDD) via the light emission control transistor BCT. 
     At this stage, no electric current flows because voltage between the anode and the cathode of the light emitting element  3  is lower than light emission start voltage. Consequently, the source of the drive transistor DRT is charged by the anode power supply potential PVDD, whereby the electric potential of the source increases. The gate potential of the drive transistor DRT is the initialization potential Vini. When the source potential of the drive transistor DRT is equal to (Vini−Vth), the drive transistor DRT is turned off, and the increase in the electric potential stops. Vth indicates a threshold voltage Vth for the drive transistor DRT. 
     The threshold voltage Vth varies depending on the sub-pixels  49 . Consequently, the source potential of the drive transistor DRT when the increase in the electric potential stops varies depending on the sub-pixels  49 . In other words, voltage corresponding to the threshold voltage Vth of the drive transistor DRT is obtained in each of the sub-pixels  49  by the operations performed in the period t 3 . At this time, the light emitting element  3  is supplied with a voltage of ((Vini−Vth)−PVSS). No electric current flows through the light emitting element  3  because this voltage is lower than the light emission start voltage of the light emitting element  3 . 
     The subsequent period t 4  is a video signal writing operation period. Specifically, in the period t 4 , the electric potential of the light emission control scanning line BG 1  is switched to the L level, the electric potential of the initialization control scanning line IG 1  is switched to the L level, and the electric potential of a writing control scanning line SG 1  is switched to the H level by the control signals supplied from the drive circuits  12 . 
     As a result, the light emission control transistor BCT is turned off, the initialization transistor IST is turned off, and the writing transistor SST is turned on. In the period t 4 , the video signals Vsig are input to the gates of the drive transistors DRT in the sub-pixels  49  belonging to the first row. The gate potential of the drive transistor DRT changes from the initialization potential Vini to the electric potential of the video signal Vsig. By contrast, the source potential of the drive transistor DRT remains at (Vini−Vth). As a result, the voltage between the gate and the source of the drive transistor DRT is equal to (Vsig−(Vini−Vth)) and reflects variations in the threshold voltage Vth between the sub-pixels  49 . 
     The video signal line L 2  extends in the second direction Dy (refer to  FIG. 1 ) and is coupled to the sub-pixels  49  of a plurality of rows belonging to the same column. Consequently, the period t 4  for performing the video writing operation is carried out row by row. 
     The subsequent period t 5  is a light emission operation period. Specifically, in the period t 5 , the electric potential of the light emission control scanning line BG 1  is switched to the H level, and the electric potential of the writing control scanning line SG 1  is switched to the L level by the control signals supplied from the drive circuits  12 . As a result, the light emission control transistor BCT is turned on, and the writing transistor SST is turned off. An electric current is supplied to the drive transistor DRT from the anode power supply line L 1  (anode power supply potential PVDD) via the light emission control transistor BCT. 
     The drive transistor DRT supplies, to the light emitting element  3 , an electric current corresponding to the voltage between the gate and the source set until the period t 4 . The light emitting element  3  emits light at the luminance corresponding to the electric current. At this time, the voltage between the anode and the cathode of the light emitting element  3  is a voltage corresponding to the value of the voltage supplied via the drive transistor DRT. As a result, the electric potential of the anode of the light emitting element  3  increases. The voltage between the gate and the source of the drive transistor DRT is held by the capacitance Cs 1 . Consequently, the gate potential of the drive transistor DRT also increases in association with the increase in the electric potential of the anode of the light emitting element  3  due to coupling of the capacitance Cs 1 . 
     In an actual operation, the increase in the gate potential of the drive transistor DRT is slightly smaller than the increase in the electric potential of the anode because additional capacitance, such as the capacitance Cs 2 , is present in the gate of the drive transistor DRT besides the capacitance Cs 1 . Because this value is already known, the electric potential of the video signal Vsig can be determined so as to obtain a desired current value at the final voltage between the gate and the source of the drive transistor DRT. 
     After the operations described above are completed from the first row to the last row, an image of one frame is displayed. The reset operation for the sub-pixels  49  belonging to the second row is performed in a period overlapping the periods t 2  and t 3 . The offset cancel operation for the sub-pixels  49  belonging to the second row is performed in a period overlapping the periods t 3  and t 4 . The video signal writing operation for the sub-pixels  49  belonging to the second row is performed in a period overlapping the period t 5 . Subsequently, the operations described above are repeated, thereby displaying video. 
     While the sub-pixels  49  of one row are driven from the period t 1  to the period t 5  in the exemplary operations illustrated in  FIG. 4 , the present embodiment is not limited thereto. The drive circuits  12  may simultaneously drive the sub-pixels  49  of two rows or three or more rows. 
     The configuration of the pixel circuit PICA illustrated in  FIG. 3  and the exemplary operations illustrated in  FIG. 4  are given by way of example only and may be appropriately modified. The number of wiring lines and the number of transistors in one sub-pixel  49 , for example, may be different from those described above. The pixel circuit PICA may have a configuration of a current mirror circuit, for example. 
     The following describes a sectional configuration of the display device  1 .  FIG. 5  is a sectional view along line V-V of  FIG. 2 . As illustrated in  FIG. 5 , the light emitting elements  3  are provided on the array substrate  2 . The array substrate  2  includes the substrate  21 , the anode electrodes  23 , mounting electrodes  24 , counter electrodes  25 , coupling electrodes  26   a , various transistors, various kinds of wiring, and various insulating films. 
     The substrate  21  is an insulating substrate and is a glass substrate made of quartz or non-alkali glass or a resin substrate made of polyimide, for example. If the substrate  21  is a flexible resin substrate, the display device  1  may be provided as a sheet display. The substrate  21  is not necessarily made of polyimide and may be made of other resin materials. 
     In the following descriptions, the direction from the substrate  21  toward the light emitting element  3  in the direction perpendicular to the surface of the substrate  21  is referred to as “on the upper side” or simply as “on”. The direction from the light emitting element  3  toward the substrate  21  is referred to as “on the lower side” or simply as “under”. 
     An undercoat film  91  is provided on the substrate  21 . The undercoat film  91  has a three-layered structure including insulating films  91   a ,  91   b , and  91   c , for example. The insulating film  91   a  is a silicon oxide film, the insulating film  91   b  is a silicon nitride film, and the insulating film  91   c  is a silicon oxide film. The lower insulating film  91   a  is provided to improve adhesion between the substrate  21  and the undercoat film  91 . The middle insulating film  91   b  is provided as a block film that restrains water and impurities from entering from outside. The upper insulating film  91   c  is provided as a block film that restrains hydrogen atoms contained in the silicon nitride film of the insulating film  91   b  from diffusing toward a semiconductor layer  61 . 
     The structure of the undercoat film  91  is not limited to that illustrated in  FIG. 5 . The undercoat film  91  may be a single-layered film or a two-layered film, for example, or may be a multilayered film having four or more layers. If the substrate  21  is a glass substrate, the silicon nitride film may be formed directly on the substrate  21  because silicon nitride films have relatively high adhesion. 
     A light shielding film  65  is provided on the insulating film  91   a . The light shielding film  65  is provided between the semiconductor layer  61  and the substrate  21 . The light shielding film  65  can restrain light from entering into a channel region  61   a  of the semiconductor layer  61  from the substrate  21 . Alternatively, the light shielding film  65  may be made of conductive material and supplied with a predetermined electric potential. As a result, the light shielding film  65  may have a back-gate effect on a drive transistor DRT. The light shielding film  65  may be provided on the substrate  21 , and the insulating film  91   a  may be provided covering the light shielding film  65 . 
     The drive transistor DRT is provided on the undercoat film  91 . While the drive transistor DRT out of the transistors is illustrated in  FIG. 5 , the light emission control transistor BCT, the initialization transistor IST, the writing transistor SST, and the reset transistor RST included in the pixel circuit PICA also have the same multilayered structure as that of the drive transistor DRT. 
     The drive transistor DRT includes the semiconductor layer  61 , a source electrode  62 , a drain electrode  63 , and a gate electrode  64 . The semiconductor layer  61  is provided on the undercoat film  91 . The semiconductor layer  61  is made of polysilicon, for example. The material of the semiconductor layer  61  is not limited thereto, and the semiconductor layer  61  may be made of a microcrystalline oxide semiconductor, an amorphous oxide semiconductor, or low-temperature polysilicon, for example. While only an n-type TFT is provided as the drive transistor DRT, a p-type TFT may be formed in addition to the n-type TFT. In the n-type TFT, the semiconductor layer  61  includes a channel region  61   a , a source region  61   b , a drain region  61   c , and a low-concentration impurity region  61   d . The low-concentration impurity region  61   d  is provided between the channel region  61   a  and the source region  61   b  and between the channel region  61   a  and the drain region  61   c.    
     A gate insulating film  92  is provided on the undercoat film  91  to cover the semiconductor layer  61 . The gate insulating film  92  is a silicon oxide film, for example. The gate electrode  64  is provided on the gate insulating film  92 . First wiring  66  is provided in the same layer as the gate electrode  64 . The gate electrode  64  and the first wiring  66  are made of molybdenum tungsten (MoW), for example. While the drive transistor DRT in the example illustrated in  FIG. 5  has a top-gate structure in which the gate electrode  64  is provided on the upper side of the semiconductor layer  61 , the structure of the drive transistor DRT is not limited thereto. The drive transistor DRT may have a bottom-gate structure in which the gate electrode  64  is provided on the lower side of the semiconductor layer  61  or a dual-gate structure in which the gate electrodes  64  are provided on both the upper side and the lower side of the semiconductor layer  61 . 
     An interlayer insulating film  93  is provided on the gate insulating film  92  to cover the gate electrode  64 . The interlayer insulating film  93  has a multilayered structure of a silicon nitride film and a silicon oxide film, for example. The source electrode  62  and the drain electrode  63  are provided on the interlayer insulating film  93 . The source electrode  62  is coupled to the source region  61   b  through a contact hole formed in the gate insulating film  92  and the interlayer insulating film  93 . The drain electrode  63  is coupled to the drain region  61   c  through a contact hole formed in the gate insulating film  92  and the interlayer insulating film  93 . The source electrode  62  is coupled to second wiring  67  serving as routing wiring. The source electrode  62 , the drain electrode  63 , and the second wiring  67  may have a three-layered structure of titanium (Ti), aluminum (Al), and titanium (Ti), for example. 
     Part of the second wiring  67  is provided in a region overlapping the first wiring  66 . The first wiring  66  and the second wiring  67  facing each other with the interlayer insulating film  93  interposed therebetween form capacitance Cs 1 . The first wiring  66  is provided in a region overlapping part of the semiconductor layer  61 . The capacitance Cs 1  includes capacitance formed by the semiconductor layer  61  and the first wiring  66  facing each other with the gate insulating film  92  interposed therebetween. 
     A first flattening film  94  is provided on the interlayer insulating film  93  to cover the drive transistor DRT and the second wiring  67 . The first flattening film  94  is made of organic material, such as photosensitive acrylic. Organic material, such as photosensitive acrylic, is excellent in coverage property for difference in level of wiring as well as in surface flatness, compared with inorganic insulating material formed by CVD, for example. 
     The counter electrode  25 , a capacitance insulating film  95 , and the anode electrode  23  are layered in the order as listed, on the first flattening film  94 . The counter electrode  25  is made of translucent conductive material, such as indium tin oxide (ITO). The coupling electrode  26   a  is provided in the same layer as the counter electrode  25 . The coupling electrode  26   a  is provided covering the inside of a contact hole H 1  formed in the first flattening film  94  and is coupled to the second wiring  67  at the bottom of the contact hole H 1 . 
     The capacitance insulating film  95  is provided covering the counter electrode  25  and the coupling electrode  26   a  and has an opening in a region overlapping the contact hole H 1 . The capacitance insulating film  95  is a silicon nitride film, for example. The anode electrode  23  faces the counter electrode  25  with the capacitance insulating film  95  interposed therebetween. The anode electrode  23  is electrically coupled to the coupling electrode  26   a  and the second wiring  67  through the contact hole H 1 . As a result, the anode electrode  23  is electrically coupled to the drive transistor DRT. The anode electrode  23  has a multilayered structure of Ti and Al. The material of the anode electrode  23  is not limited thereto, and the anode electrode  23  may be made of material including at least one of metals of Mo and Ti. Alternatively, the anode electrode  23  may be made of alloy including at least one of Mo and Ti or translucent conductive material. 
     Capacitance Cs 2  is formed between the anode electrode  23  and the counter electrode  25  facing each other with the capacitance insulating film  95  interposed therebetween. The counter electrode  25  made of ITO also serves as a barrier film that protects various kinds of wiring, such as the second wiring  67 , in forming the anode electrode  23 . In patterning the anode electrode  23 , the counter electrode  25  is partially exposed to etching environment. By annealing performed between formation of the counter electrode  25  and formation of the anode electrode  23 , the counter electrode  25  has sufficient resistance to etching for the anode electrode  23 . 
     A second flattening film  97  is provided on the anode electrode  23 . The second flattening film  97  has a contact hole H 2  reaching the anode electrode  23 . The mounting electrode  24  is provided on the second flattening film  97  and electrically coupled to the anode electrode  23  through the contact hole H 2 . The mounting electrode  24  has a multilayered structure of Ti and Al like the anode electrode  23 . The mounting electrode  24  may be made of conductive material different from that of the anode electrode  23 . 
     The light emitting elements  3 R,  3 G, and  3 B are mounted on the respective mounting electrodes  24 . The light emitting elements  3  are each mounted such that the anode terminal  33  is in contact with the mounting electrode  24 . Connection between the anode terminal  33  of the light emitting element  3  and the mounting electrode  24  is not particularly restricted as long as the connection can secure excellent electrical continuity between the anode terminal  33  and the mounting electrode  24  and does not damage objects formed on the array substrate  2 . Examples of the method for connecting the anode terminal  33  and the mounting electrode  24  include, but are not limited to, reflowing using low-temperature melting soldering material, a method of placing the light emitting element  3  on the array substrate  2  with conductive paste interposed therebetween and burning and bonding them, etc. 
     The light emitting element  3  may be mounted directly on the anode electrode  23  without the second flattening film  97  or the mounting electrode  24  on the array substrate  2 . Providing the second flattening film  97  and the mounting electrode  24  can restrain the capacitance insulating film  95  from being damaged by force applied in mounting the light emitting element  3 . In other words, the second flattening film  97  and the mounting electrode  24  can restrain dielectric breakdown that would otherwise be caused between the anode electrode  23  and the counter electrode  25  that form the capacitance Cs 2 . 
     The light emitting element  3  includes a semiconductor layer  31 , the cathode terminal  32 , and the anode terminal  33 . The semiconductor layer  31  is made of a compound semiconductor, such as gallium nitride (GaN) and aluminum indium phosphorous (AlInP). The semiconductor layer  31  may be made of different materials between the light emitting elements  3 R,  3 G, and  3 B. The active layer may have a multi-quantum well structure (MQW structure) in which well layers and barrier layers composed of several atomic layers are cyclically layered for high efficiency. The semiconductor layer  31  may be formed on a semiconductor substrate as the light emitting element  3 . The light emitting element  3  is not necessarily mounted alone on the array substrate  2 , and an LED chip including the light emitting element  3  may be mounted on the array substrate  2 . 
     An element insulating film  98  is provided between the plurality of light emitting elements  3 . The element insulating film  98  is made of resin material. The element insulating film  98  covers the side surfaces of each light emitting element  3 , and the cathode terminal  32  of the light emitting element  3  is exposed from the element insulating film  98 . The element insulating film  98  is flattened such that the upper surface of the element insulating film  98  and the upper surface of the cathode terminal  32  form a single plane. The position of the upper surface of the element insulating film  98  may be different from that of the upper surface of the cathode terminal  32 . 
     The cathode electrode  22  covers the plurality of light emitting elements  3  and the element insulating film  98  and is electrically coupled to the light emitting elements  3 . More specifically, the cathode electrode  22  is provided across the upper surface of the element insulating film  98  and the upper surface of the cathode terminal  32 . The cathode electrode  22  is made of translucent conductive material, such as ITO. With this configuration, the light emitted from the light emitting elements  3  can be efficiently extracted to the outside. The cathode electrode  22  is electrically coupled to the cathode terminals  32  of the light emitting elements  3  mounted on the display region AA. The cathode electrode  22  is coupled to the cathode wiring  60  provided on the array substrate  2 , at a cathode contact portion provided outside the display region AA. 
     An overcoat layer OC and an optical member OE are layered on the cathode electrode  22 . The overcoat layer OC is a multilayered structure of a silicon nitride film having a thickness of 200 nm and an organic insulating film having a thickness of 10 μm. The optical member OE is an optical functional layer that scatters light emitted from the light emitting element  3  to shift the direction of the maximum of light emission distribution in the third direction Dz. The optical member OE includes a first anisotropic diffusion layer AD 1  and a second anisotropic diffusion layer AD 2 . The first anisotropic diffusion layer AD 1  faces the substrate  21  (array substrate  2 ) with the plurality of light emitting elements  3  interposed therebetween. The second anisotropic diffusion layer AD 2  is layered on the first anisotropic diffusion layer AD 1 . The configuration of the optical member OE will be described later in greater detail. 
       FIG. 6  is a partially enlarged sectional view of the light emitting element illustrated in  FIG. 5 . As illustrated in  FIG. 6 , the light emitting element  3  includes an n-type clad layer NC, a light emission layer EM, a p-type clad layer PC, and the anode terminal  33 . The p-type clad layer PC, the light emission layer EM, and the n-type clad layer NC are layered in this order on the anode terminal  33 . The anode terminal  33  is provided between the p-type clad layer PC and the mounting electrode  24 . 
     In the light emitting element  3 B that emits blue light, the light emission layer EM is made of indium gallium nitride (InGaN). The composition ratio of indium to gallium is 0.2:0.8, for example. The p-type clad layer PC and the n-type clad layer NC are made of gallium nitride (GaN). 
     In the light emitting element  3 G that emits green light, the light emission layer EM is made of indium gallium nitride (InGaN). The composition ratio of indium to gallium is 0.45:0.55, for example. The p-type clad layer PC and the n-type clad layer NC are made of gallium nitride (GaN). 
     In the light emitting element  3 R that emits red light, the light emission layer EM is made of aluminum gallium indium (AlGaIn). The composition ratio among aluminum, gallium, and indium is 0.225:0.275:0.5, for example. The p-type clad layer PC and the n-type clad layer NC are made of aluminum indium phosphide (AlInP). 
     The anode terminals  33  of the light emitting elements  3 R,  3 G, and  3 B are made of aluminum. The maximum emission wavelengths of the light emitting elements  3 R,  3 G, and  3 B are 645 nm, 530 nm, and 450 nm, respectively. 
     As described above, the display device  1  with the light emitting elements  3  serving as display elements is provided. The display device  1  may include a circularly polarizing plate, a cover glass, a touch panel, and other components on the upper sides of the cathode electrode  22  and the optical member OE as needed. In this case, a filler made of resin or the like may be provided between the display device  1  and the member, such as a cover glass. The display device  1  does not necessarily have a face-up structure in which the upper part of the light emitting element  3  is coupled to the cathode electrode  22 . The display device  1  may have what is called a face-down structure in which the lower part of the light emitting element  3  is coupled to the anode electrode  23  and the cathode electrode  22 . 
     The following describes distribution of light emitted from the light emitting element  3 . A refractive index n LED  of the light emitting element  3  is 2.4, for example. A refractive index n CD  of the cathode electrode  22  disposed close to the upper part of the light emitting element  3  is 1.9, for example. A refractive index n DC  of the overcoat layer OC is 1.5, for example. The refractive indexes n CD  and n DC  are lower than the refractive index n LED . As a result, the traveling direction of light emitted from the light emitting element  3  is directed in an oblique direction inclining with respect to the third direction Dz when the light is passing through the cathode electrode  22  and the overcoat layer OC. The component of light having a large incident angle may possibly be totally reflected on the interface between the light emitting element  3  and the cathode electrode  22  and travel in a direction parallel to the array substrate  2 . 
       FIG. 19  is a graph schematically illustrating a relation between the relative luminance of light from the light emitting element that emits red light and the polar angle.  FIG. 20  is a graph schematically illustrating a relation between the relative luminance of light from the light emitting element that emits green light and the polar angle.  FIG. 21  is a graph schematically illustrating a relation between the relative luminance of light from the light emitting element that emits blue light and the polar angle. 
     The graphs illustrated in  FIGS. 19 to 21  indicate the light emission properties of light emitting elements  3 R,  3 G, and  3 B in a display device according to a comparative example not provided with the optical member OE. The abscissas of the graphs illustrated in  FIGS. 19 to 21  indicate the polar angle, that is, the inclination angle with respect to the third direction Dz. The ordinates of the graphs indicate the relative luminance of light emitted from the respective light emitting elements  3 R,  3 G, and  3 B. 
     As illustrated in  FIGS. 19 to 21 , none of the light emitting elements  3 R,  3 G, and  3 B has the peak of the relative luminance at a polar angle of 0°, that is, in the third direction Dz. The light emitting elements  3 R,  3 G, and  3 B have the polar angle dependence that the relative luminance is higher at a polar angle of 45° than at a polar angle of 0°, for example. The light emitting elements  3 R,  3 G, and  3 B have different polar angle dependences of relative luminance. 
     The light emitting element  3 R illustrated in  FIG. 19 , for example, has polar angle dependence relatively broader than those of the light emitting elements  3 G and  3 B. The difference between the relative luminance at a polar angle of 0° and at a polar angle of 45° in the light emitting element  3 R is smaller than the difference between the relative luminance at a polar angle of 0° and at a polar angle of 45° in the light emitting element  3 G. As illustrated in  FIG. 21 , the difference between the relative luminance at a polar angle of 0° and at a polar angle of 45° in the light emitting element  3 B is smaller than those in the light emitting elements  3 R and  3 G. The light emitting element  3 B has the peaks of the relative luminance in a direction near the direction of a polar angle of 90°, that is, near the horizontal direction orthogonal to the third direction Dz. As described above, if the optical member OE is not provided, the light emitting element  3  has smaller polar angle dependence or has the peak of relative luminance in a direction of a larger polar angle. The light emission properties of the light emitting elements  3  illustrated in  FIGS. 19 to 21  are given by way of example only.  FIGS. 19 to 21  illustrate the relative luminance of the light emitting elements  3 R,  3 G, and  3 B, respectively, and do not illustrate the luminance of the light emitting elements  3 R,  3 G, and  3 B in a comparative manner. 
     The following describes the configuration of the optical member OE in greater detail. To facilitate the reader&#39;s understanding,  FIGS. 7 to 9  illustrate the first anisotropic diffusion layer AD 1  serving as one of the anisotropic diffusion layers included in the optical member OE.  FIG. 7  is a plan view schematically illustrating the first anisotropic diffusion layer included in the optical member according to the first embodiment. 
     The first anisotropic diffusion layer AD 1  is a sheet member that scatters light. As illustrated in  FIG. 7 , the first anisotropic diffusion layer AD 1  includes first regions PST and a second region IPST. The region, in the in-plane direction, of the first anisotropic diffusion layer AD 1  includes the first regions PST (high refractive index regions) and the second region IPST (low refractive index region) in a mixed manner. Specifically, the first regions PST each have a columnar structure, have a circular shape in planar view, and are arrayed away from each other. The second region IPST is provided between the first regions PST in a manner surrounding the first regions PST. 
     The first region PST and the second region IPST have different refractive indexes. The refractive index of the first region PST is higher than that of the second region IPST. In other words, the first region PST is a high refractive index region, that is, a region having a relatively high refractive index in the first anisotropic diffusion layer AD 1 . The second region IPST is a low refractive index region, that is, a region having a relatively low refractive index in the first anisotropic diffusion layer AD 1 . 
     While the first regions PST are arrayed in a triangular lattice or a hound&#39;s-tooth pattern in  FIG. 7 , the present embodiment is not limited thereto. The first regions PST may be arrayed in a matrix (row-column configuration) or at random. 
       FIG. 8  is a sectional view along line VIII-VIII′ of  FIG. 7 . As illustrated in  FIG. 8 , the first regions PST extend inclining in the second direction Dy (+Dy direction) with respect to the third direction Dz. The first anisotropic diffusion layer AD 1  has anisotropy for light scattering and has a property of scattering light traveling in a specific incident direction out of incident light. In other words, the first anisotropic diffusion layer AD 1  scatters light traveling in an incident direction within a range of approximately ±20° with respect to the extension direction of the first region PST and causes light traveling in an incident direction out of a range of ±20° with respect to the extension direction of the first region PST to pass therethrough. 
     Specifically, the extension direction of the first region PST inclines with respect to the third direction Dz by 20° or more. When a first angle θ 1  is the angle formed by the extension direction of the first region PST and the third direction Dz, 01&gt;20° is satisfied. Light La parallel to the extension direction of the first region PST is scattered, and light Lb parallel to the third direction Dz is not scattered. 
     Out of scattered lights S 1 , S 2 , S 3 , and S 4  of the light La, the scattered lights S 1  and S 2  are directed toward a lower polar angle side than a scattering central axis S 0 , that is, in a direction (−Dy direction) closer to the third direction Dz. By contrast, the scattered lights S 3  and S 4  are directed toward a higher polar angle side than the scattering central axis S 0 , that is, in a direction (+Dy direction) away from the third direction Dz. Light of the component of the scattering central axis S 0  may be referred to as the maximum of the scattered light components. 
     The scattering central axis S 0  is an axis about which the anisotropic scattering properties of incident light are substantially symmetrical. In other words, the scattering central axis S 0  extends in the incident direction of the most scattered light. An angle θ formed by the axial direction of the scattering central axis S 0  and the normal direction (third direction Dz) of the surface of the first anisotropic diffusion layer AD 1  is referred to as a polar angle of the scattering central axis S 0 . The scattering central axis S 0  inclines with respect to the third direction Dz. In other words, the first region PST inclines with respect to the third direction Dz. An azimuth angle SP 1  of the scattering central axis S 0  is a direction obtained by projecting the scattering central axis S 0  on a plane defined by the first direction Dx and the second direction Dy and is directed in the +Dy direction. 
     The extension direction of the first region PST according to the first embodiment is parallel to the extension direction of the boundary between the first region PST and the second region IPST. In other words, the angle θ of the scattering central axis S 0  is equal to the first angle θ 1  of the boundary between the first region PST and the second region IPST. While  FIG. 8  is a sectional view of the first anisotropic diffusion layer AD 1  cut along a plane defined by the second direction Dy and the third direction Dz, the light La is scattered also in the plane. In other words, when the second direction Dy is an azimuth angle of 0°, the light La is also scattered in the azimuth angle direction. 
       FIG. 9  is a graph schematically illustrating a relation between the relative luminance of light scattered by the first anisotropic diffusion layer and the polar angle.  FIG. 9  illustrates the relative luminance of light obtained when the first anisotropic diffusion layer AD 1  is provided at the front surface of the light emitting elements  3  having the light emission distribution properties illustrated in  FIGS. 19 to 21 .  FIG. 9  indicates the polar angle dependence in the azimuth angle direction (second direction Dy) including the extension direction of the first region PST. 
     As illustrated in  FIG. 9 , light scattered by the first anisotropic diffusion layer AD 1  has the minimum LM and the maximum LP of the relative luminance in the polar angle direction of the +Dy direction in the second direction Dy. The angle indicating the minimum LM is substantially equal to the first angle θ 1  (refer to  FIG. 8 ) corresponding to the extension direction of the first region PST. Scattering the light La incident at the first angle θ 1  increases the relative luminance at the polar angles around the first angle θ 1 . The maximum LP is formed by the scattered lights S 1  and S 2  being directed toward the lower polar angle side than the first angle θ 1 . Consequently, the first anisotropic diffusion layer AD 1  can improve the relative luminance of light in the normal direction of the array substrate  2 . 
       FIG. 10  is a sectional view schematically illustrating the optical member according to the first embodiment. As illustrated in  FIG. 10 , the optical member OE includes the first anisotropic diffusion layer AD 1  and the second anisotropic diffusion layer AD 2 . The second anisotropic diffusion layer AD 2  is layered on the first anisotropic diffusion layer AD 1 . More specifically, the first anisotropic diffusion layer AD 1  and the second anisotropic diffusion layer AD 2  are layered in this order on the upper side of the array substrate  2  in the third direction Dz. The second anisotropic diffusion layer AD 2  is provided farther away from the array substrate  2  (substrate  21 ) than the first anisotropic diffusion layer AD 1  is. 
     As with the first anisotropic diffusion layer AD 1 , the second anisotropic diffusion layer AD 2  includes the first regions PST and the second region IPST. The azimuth angle SP 1  (first azimuth angle) of the scattering central axis S 0  of light of the first anisotropic diffusion layer AD 1  is equal to an azimuth angle SP 2  (second azimuth angle) of a scattering central axis S 10  of light of the second anisotropic diffusion layer AD 2 . In other words, both the first region PST (high refractive index region) of the first anisotropic diffusion layer AD 1  and the first region PST (high refractive index region) of the second anisotropic diffusion layer AD 2  extend inclining in the same direction (+Dy direction) with respect to the third direction Dz. The azimuth angles SP 1  and SP 2  indicate directions in planar view obtained by projecting the scattering central axes S 0  and S 10 , respectively, on a plane defined by the first direction Dx and the second direction Dy. 
     A second angle θ 2  is the angle formed by the extension direction of the first region PST of the second anisotropic diffusion layer AD 2  and the third direction Dz. The second angle θ 2  is different from the first angle θ 1 . More specifically, the absolute value of the first angle θ 1  formed by the boundary between the first region PST (high refractive index region) and the second region IPST (low refractive index region) of the first anisotropic diffusion layer AD 1  and the third direction Dz is different from the absolute value of the second angle θ 2  formed by the boundary between the first region PST (high refractive index region) and the second region IPST (low refractive index region) of the second anisotropic diffusion layer AD 2  and the third direction Dz. More preferably, the absolute value of the first angle θ 1  is larger than that of the second angle θ 2 . 
     The arrangement pitch of the first regions PST of the second anisotropic diffusion layer AD 2  in the second direction Dy is smaller than that of the first regions PST of the first anisotropic diffusion layer AD 1  in the second direction Dy. The present embodiment is not limited thereto, and the arrangement pitch of the first regions PST of the second anisotropic diffusion layer AD 2  may be equal to that of the first regions PST of the first anisotropic diffusion layer AD 1 . 
     As described above, the first anisotropic diffusion layer AD 1  scatters the incident light La. The following explanation is made focusing on, out of the scattered lights S 1 , S 2 , S 3 , and S 4  (refer to  FIG. 8 ) of the light La, the scattered light S 1  on the high polar angle side. The scattered light S 1  is parallel to the extension direction of the first region PST of the second anisotropic diffusion layer AD 2 . In other words, the scattered light S 1  is scattered by the second anisotropic diffusion layer AD 2  because it travels in a direction parallel to the second angle θ 2 . 
     The components of the scattered light S 1  scattered by the second anisotropic diffusion layer AD 2  are referred to as scattered lights S 11 , S 12 , S 13 , and S 14 . The scattered lights S 11  and S 12  are directed toward the lower polar angle side than the scattering central axis S 10 , that is, in a direction (−Dy direction) closer to the third direction Dz. The scattered lights S 11  and S 12  are directed in a direction substantially parallel to the third direction Dz. By contrast, the scattered lights S 13  and S 14  are directed toward the higher polar angle side than the scattering central axis S 10 , that is, in a direction (+Dy direction) away from the third direction Dz. 
     The second angle θ 2  is larger than 20°. Consequently, the light Lb parallel to the third direction Dz passes through the first anisotropic diffusion layer AD 1  and is not scattered by the second anisotropic diffusion layer AD 2 . 
       FIG. 11  is a graph schematically illustrating a relation between the relative luminance of light emitted from the display device according to the first embodiment and the polar angle. As illustrated in  FIG. 11 , the maximum LP of the relative luminance of light emitted from the display device  1  is positioned near a polar angle of 0°, that is, near the third direction Dz. The light has the minimum LM in the +Dy direction and the relative luminance of the light decreases on the high polar angle side. In other words, light on the high polar angle side out of the light emitted from the light emitting element  3  is collected by the optical member OE in the third direction Dz. Consequently, the display device  1  can improve the relative luminance in the third direction Dz in which an observer highly frequently observes the display device  1 . 
     As described above, the first angle θ 1  of the first anisotropic diffusion layer AD 1  according to the present embodiment is different from the second angle θ 2  of the second anisotropic diffusion layer AD 2 . The azimuth angle SP 1  of the first region PST of the first anisotropic diffusion layer AD 1  is equal to the azimuth angle SP 2  of the first region PST of the second anisotropic diffusion layer AD 2 . As a result, the light diffusion function of the first anisotropic diffusion layer AD 1  and the light diffusion function of the second anisotropic diffusion layer AD 2  are combined, thereby increasing the light scattering angle of the optical member OE as a whole. 
     More preferably, the first angle θ 1  of the first anisotropic diffusion layer AD 1  is larger than the second angle θ 2  of the second anisotropic diffusion layer AD 2 . With this structure, the first anisotropic diffusion layer AD 1  can scatter the light La incident at an angle larger than the second angle θ 2  and cause part of the components of the light La to be incident on the second anisotropic diffusion layer AD 2 . The second anisotropic diffusion layer AD 2  can further scatter the scattered lights S 1  and S 2  of the light La. Consequently, the display device of the present embodiment can more effectively direct the incident light in the third direction Dz than in a case where any one of the first anisotropic diffusion layer AD 1  and the second anisotropic diffusion layer AD 2  is provided. 
     The configuration of the optical member OE is given by way of example only and may be appropriately modified. While the second anisotropic diffusion layer AD 2  is layered in contact with the first anisotropic diffusion layer AD 1 , the present embodiment is not limited thereto. The second anisotropic diffusion layer AD 2  may be layered in a manner separated from the first anisotropic diffusion layer AD 1 , and another optical functional layer may be provided between the second anisotropic diffusion layer AD 2  and the first anisotropic diffusion layer AD 1 . 
     While the first region PST has a columnar structure, the present embodiment is not limited thereto. The first region PST may have a louver structure having a plate shape inclining with respect to the third direction Dz. 
     Second Embodiment 
       FIG. 12  is a sectional view schematically illustrating an optical member according to a second embodiment. In the following description, the same components as those described in the embodiment above are denoted by the same reference numerals, and overlapping explanation thereof is omitted. 
     As illustrated in  FIG. 12 , an optical member OEA according to the second embodiment includes the first anisotropic diffusion layer AD 1 , the second anisotropic diffusion layer AD 2 , a third anisotropic diffusion layer AD 3 , and a fourth anisotropic diffusion layer AD 4 . The first anisotropic diffusion layer AD 1 , the third anisotropic diffusion layer AD 3 , the second anisotropic diffusion layer AD 2 , and the fourth anisotropic diffusion layer AD 4  are layered in this order in the third direction Dz. In other words, the third anisotropic diffusion layer AD 3  is provided between the first anisotropic diffusion layer AD 1  and the second anisotropic diffusion layer AD 2  in the third direction Dz. The fourth anisotropic diffusion layer AD 4  is provided farther away from the substrate  21  (array substrate  2 ) in the third direction Dz than the third anisotropic diffusion layer AD 3  is. 
     The third anisotropic diffusion layer AD 3  and the fourth anisotropic diffusion layer AD 4  each include the first regions PST and the second region IPST in a manner similar to the first anisotropic diffusion layer AD 1  and the second anisotropic diffusion layer AD 2 . The first regions PST of the third anisotropic diffusion layer AD 3  and the fourth anisotropic diffusion layer AD 4  also have a columnar structure. 
     As illustrated in  FIG. 12 , the first regions PST of the third anisotropic diffusion layer AD 3  and the fourth anisotropic diffusion layer AD 4  incline opposite to the first regions PST of the first anisotropic diffusion layer AD 1  and the second anisotropic diffusion layer AD 2  with respect to the third direction Dz. In other words, the first regions PST of the first anisotropic diffusion layer AD 1  and the second anisotropic diffusion layer AD 2  incline in the +Dy direction with respect to the third direction Dz. The first regions PST of the third anisotropic diffusion layer AD 3  and the fourth anisotropic diffusion layer AD 4  incline in the −Dy direction with respect to the third direction Dz. 
     A third angle θ 3  is the angle formed by the extension direction of the first region PST of the third anisotropic diffusion layer AD 3  and the third direction Dz. A fourth angle θ 4  is the angle formed by the extension direction of the first region PST of the fourth anisotropic diffusion layer AD 4  and the third direction Dz. The absolute value of the third angle θ 3  is different from the absolute value of the fourth angle θ 4 . More specifically, the absolute value of the third angle θ 3  formed by the boundary between the first region PST (high refractive index region) and the second region IPST (low refractive index region) of the third anisotropic diffusion layer AD 3  and the third direction Dz is different from the absolute value of the fourth angle θ 4  formed by the boundary between the first region PST (high refractive index region) and the second region IPST (low refractive index region) of the fourth anisotropic diffusion layer AD 4  and the third direction Dz. More preferably, the absolute value of the third angle θ 3  is larger than that of the fourth angle θ 4 . 
     In the sectional structure, the third anisotropic diffusion layer AD 3  is symmetrical to the first anisotropic diffusion layer AD 1  about a virtual line parallel to the second direction Dy. In other words, the absolute value of the third angle θ 3  is equal to that of the first angle θ 1 . In the sectional structure, the fourth anisotropic diffusion layer AD 4  is symmetrical to the second anisotropic diffusion layer AD 2  about a virtual line parallel to the second direction Dy. In other words, the absolute value of the fourth angle θ 4  is equal to that of the second angle θ 2 . 
     As described above, the first anisotropic diffusion layer AD 1  scatters the incident light La. The following explanation is made focusing on the scattered light S 1 , which is on the high polar angle side, out of the scattered lights S 1 , S 2 , S 3 , and S 4  (refer to  FIG. 8 ) of the light La. The third anisotropic diffusion layer AD 3  is provided between the first anisotropic diffusion layer AD 1  and the second anisotropic diffusion layer AD 2 . The scattered light S 1 , however, does not fall within the light diffusion angle range of the third anisotropic diffusion layer AD 3  (the traveling direction of the scattered light S 1  is different from the third angle θ 3  by approximately ±20° or greater, for example). As a result, the scattered light S 1  passes through the third anisotropic diffusion layer AD 3  without being scattered. The scattered light S 1  is parallel to the extension direction of the first region PST of the second anisotropic diffusion layer AD 2 . In other words, the scattered light S 1  is scattered by the second anisotropic diffusion layer AD 2  because it travels in a direction parallel to the second angle θ 2 . 
     The scattered lights S 11 , S 12 , S 13 , and S 14  scattered by the second anisotropic diffusion layer AD 2  are incident on the fourth anisotropic diffusion layer AD 4 . The scattered lights S 11 , S 12 , S 13 , and S 14 , however, do not fall within the light diffusion angle range of the fourth anisotropic diffusion layer AD 4  (the traveling directions of the scattered lights S 11 , S 12 , S 13 , and S 14  are different from the fourth angle θ 4  by approximately ±20° or greater, for example). As a result, the scattered lights S 11 , S 12 , S 13 , and S 14  pass through the fourth anisotropic diffusion layer AD 4  without being scattered. 
     Similarly, light incident at the third angle θ 3  in the −Dy direction with respect to the third direction Dz is scattered by the third anisotropic diffusion layer AD 3  and the fourth anisotropic diffusion layer AD 4 . Part of the components of the scattered light scattered by the fourth anisotropic diffusion layer AD 4  is directed in a direction parallel to the third direction Dz. The light incident at the third angle θ 3  passes through the first anisotropic diffusion layer AD 1  and the second anisotropic diffusion layer AD 2  without being scattered. 
     The third angle θ 3  and the fourth angle θ 4  are larger than 20°. Consequently, the light Lb parallel to the third direction Dz passes through the first anisotropic diffusion layer AD 1  to the fourth anisotropic diffusion layer AD 4  without being scattered. 
       FIG. 13  is a view for explaining the azimuth angles of the optical member according to the second embodiment. The azimuth angles SP 1  and SP 2  illustrated in  FIG. 13  indicate the azimuth angles of the first anisotropic diffusion layer AD 1  and the second anisotropic diffusion layer AD 2 , respectively. Azimuth angles SP 3  and SP 4  indicate the azimuth angles of the third anisotropic diffusion layer AD 3  and the fourth anisotropic diffusion layer AD 4 , respectively. The azimuth angles SP 1 , SP 2 , SP 3 , and SP 4  are the directions of the scattering central axes of the first anisotropic diffusion layer AD 1  to the fourth anisotropic diffusion layer AD 4 , respectively, in planar view, that is, the extension direction of the first regions PST having a columnar structure. 
     As illustrated in  FIG. 13 , the azimuth angles SP 1  and SP 2  are directed in the +Dy direction. The azimuth angle SP 3  (third azimuth angle) is directed in a direction equal to that of the azimuth angle SP 4  (fourth azimuth angle). The azimuth angles SP 3  and SP 4  are directed in a direction different from that of the azimuth angles SP 1  and SP 2 , that is, the −Dy direction opposite to the direction of the azimuth angles SP 1  and SP 2 . 
     In the optical member OEA of a display device  1 A, the first anisotropic diffusion layer AD 1  and the second anisotropic diffusion layer AD 2  can scatter light having an incident angle inclining in the +Dy direction with respect to the third direction Dz. The third anisotropic diffusion layer AD 3  and the fourth anisotropic diffusion layer AD 4  can scatter light having an incident angle inclining in the −Dy direction with respect to the third direction Dz. 
       FIG. 14  is a graph schematically illustrating a relation between the relative luminance of light emitted from the display device according to the second embodiment and the polar angle. The polar angles illustrated in  FIG. 14  are polar angles on a plane defined by the azimuth angles SP 1 , SP 2 , SP 3 , and SP 4  along the second direction Dy and the third direction Dz. 
     As illustrated in  FIG. 14 , the maximum LP of the relative luminance of light emitted from the display device  1 A coincides with a polar angle of 0°, that is, the third direction Dz. The polar angle dependence of the relative luminance is substantially symmetrical about the direction of a polar angle of 0°. The absolute value of the polar angle indicating the minimum LM in the +Dy direction is equal to that of the polar angle indicating the minimum LM in the −Dy direction. This is because the third anisotropic diffusion layer AD 3  and the fourth anisotropic diffusion layer AD 4  have sectional structures symmetrical to the sectional structures of the first anisotropic diffusion layer AD 1  and the second anisotropic diffusion layer AD 2 , respectively. 
     The relative luminance in the direction of a polar angle of 0° is higher than that in the graph of the polar angle dependence according to the first embodiment illustrated in  FIG. 11 . In other words, the difference between the minimum LM and the maximum LP according to the second embodiment is larger, and the half width of the relative luminance is smaller. This is because the optical member OEA according to the second embodiment changes the traveling directions of the light having an incident angle inclining in the +Dy direction and the light having an incident angle inclining in the −Dy direction with respect to the third direction Dz and directs the light in the third direction Dz, thereby increasing the relative luminance in the third direction Dz. As described above, the display device  1 A according to the second embodiment can effectively improve the relative luminance of light in the normal direction of the array substrate  2 . 
     Modifications 
       FIG. 15  is a sectional view schematically illustrating an optical member according to a modification of the second embodiment. As illustrated in  FIG. 15 , in an optical member OEB according to the modification of the second embodiment, the first anisotropic diffusion layer AD 1 , the second anisotropic diffusion layer AD 2 , the third anisotropic diffusion layer AD 3 , and the fourth anisotropic diffusion layer AD 4  are layered in this order in the third direction Dz. 
     The structures of the first anisotropic diffusion layer AD 1  to the fourth anisotropic diffusion layer AD 4  are the same as those according to the second embodiment. In other words, the light La having an incident angle inclining in the +Dy direction with respect to the third direction Dz is scattered by the first anisotropic diffusion layer AD 1 . The scattered light S 1  out of the components of the scattered light of the light La is diffused by the second anisotropic diffusion layer AD 2 . The traveling directions of the scattered lights S 11  and S 12  are directed toward the lower polar angle side than the scattering central axis S 10  of the scattered light S 1 . The scattered lights S 11 , S 12 , S 13 , and S 14  pass through the third anisotropic diffusion layer AD 3  and the fourth anisotropic diffusion layer AD 4  without being scattered. 
     Light having an incident angle inclining in the −Dy direction with respect to the third direction Dz is not scattered by the first anisotropic diffusion layer AD 1  or the second anisotropic diffusion layer AD 2  and is incident on the third anisotropic diffusion layer AD 3 . The light having an incident angle inclining in the −Dy direction with respect to the third direction Dz is scattered by the third anisotropic diffusion layer AD 3  and the fourth anisotropic diffusion layer AD 4 . The travelling direction of part of the scattered light scattered by the fourth anisotropic diffusion layer AD 4  is directed toward the low polar angle side. 
     The layering order from the first anisotropic diffusion layer AD 1  to the fourth anisotropic diffusion layer AD 4  is not limited to those in the examples illustrated in  FIGS. 12 and 15 . The second anisotropic diffusion layer AD 2  having the second angle θ 2  simply needs to be positioned farther away from the substrate  21  (in the third direction Dz) than the first anisotropic diffusion layer AD 1  having the first angle θ 1  is, and the fourth anisotropic diffusion layer AD 4  having the fourth angle θ 4  simply needs to be positioned farther away from the substrate  21  (in the third direction Dz) than the third anisotropic diffusion layer AD 3  having the third angle θ 3  is. For example, the third anisotropic diffusion layer AD 3 , the fourth anisotropic diffusion layer AD 4 , the first anisotropic diffusion layer AD 1 , the second anisotropic diffusion layer AD 2  may be layered in this order in the third direction Dz. Alternatively, at least one of the third anisotropic diffusion layer AD 3  and the fourth anisotropic diffusion layer AD 4  may be disposed between the first anisotropic diffusion layer AD 1  and the second anisotropic diffusion layer AD 2  in the third direction Dz. 
     Third Embodiment 
       FIG. 16  is a view for explaining azimuth angles of an optical member according to a third embodiment. As illustrated in  FIG. 16 , an optical member OEC of a display device  1 C according to the third embodiment has an eight-layered structure from the first anisotropic diffusion layer AD 1  to an eighth anisotropic diffusion layer AD 8 . The structures of the first anisotropic diffusion layer AD 1  to the fourth anisotropic diffusion layer AD 4  are the same as those according to the second embodiment. 
     Similarly to the first anisotropic diffusion layer AD 1  to the fourth anisotropic diffusion layer AD 4 , the fifth anisotropic diffusion layer AD 5  to the eighth anisotropic diffusion layer AD 8  each include the first regions PST having a columnar structure and the second region IPST provided around the first regions PST. In the fifth anisotropic diffusion layer AD 5  to the eighth anisotropic diffusion layer AD 8 , the extension direction of the first region PST is positioned in a plane defined by the first direction Dx and the third direction Dz in the same section. In the fifth anisotropic diffusion layer AD 5  to the eighth anisotropic diffusion layer AD 8 , the extension direction of the first region PST inclines in the +Dx direction or the −Dx direction with respect to the third direction Dz. 
     The sectional structure of the fifth anisotropic diffusion layer AD 5  to the eighth anisotropic diffusion layer AD 8  cut along the first direction Dx can be the same as the sectional structure of the first anisotropic diffusion layer AD 1  to the fourth anisotropic diffusion layer AD 4  illustrated in  FIG. 12 or 15 . The angles formed by the extension direction of the first region PST of the fifth anisotropic diffusion layer AD 5  to the eighth anisotropic diffusion layer AD 8  and the third direction Dz may be different from the first angle θ 1  to the fourth angle θ 4  of the first anisotropic diffusion layer AD 1  to the fourth anisotropic diffusion layer AD 4 . 
     As illustrated in  FIG. 16 , an azimuth angle SP 5  (fifth azimuth angle) and an azimuth angle SP 6  (sixth azimuth angle) of the fifth anisotropic diffusion layer AD 5  and the sixth anisotropic diffusion layer AD 6  are the same direction and directed in the −Dx direction. In other words, the azimuth angles SP 5  and SP 6  are orthogonal to the azimuth angles SP 1  and SP 2 . Azimuth angles SP 7  and SP 8  of the seventh anisotropic diffusion layer AD 7  and the eighth anisotropic diffusion layer AD 8  are directed in the +Dx direction opposite to the direction of the azimuth angles SP 5  and SP 6 . 
     In the optical member OEC of the display device  1 C, the fifth anisotropic diffusion layer AD 5  and the sixth anisotropic diffusion layer AD 6  can scatter light having an incident angle inclining in the −Dx direction with respect to the third direction Dz. The seventh anisotropic diffusion layer AD 7  and the eighth anisotropic diffusion layer AD 8  can scatter light having an incident angle inclining in the +Dx direction with respect to the third direction Dz. 
       FIG. 17  is a graph schematically illustrating a relation between the relative luminance of light emitted from the display device according to the third embodiment and the polar angle. The polar angles illustrated in  FIG. 17  are polar angles on a plane defined by the azimuth angles SP 1 , SP 2 , SP 3 , and SP 4  along the second direction Dy and the third direction Dz. The optical member OEC according to the third embodiment also has a symmetric property in the first direction Dx. For this reason, a graph indicating polar angles on a plane defined by the azimuth angles SP 5 , SP 6 , SP 7 , and SP 8  along the first direction Dx and the third direction Dz shows the same polar angle dependence as that illustrated in  FIG. 17 . 
     As illustrated in  FIG. 17 , the maximum LP of the relative luminance of light emitted from the display device  1 C coincides with a polar angle of 0°, that is, the third direction Dz. The polar angle dependence of the relative luminance is substantially symmetrical about the direction of a polar angle of 0°. The absolute value of the polar angle indicating the minimum LM in the +Dy direction is equal to that of the polar angle indicating the minimum LM in the −Dy direction. The absolute value of the polar angle indicating the minimum LM in the +Dx direction is equal to that of the polar angle indicating the minimum LM in the −Dx direction. 
     The relative luminance in the direction of a polar angle of 0° according to the third embodiment is higher than the polar angle dependence of the relative luminance according to the second embodiment illustrated in  FIG. 14 . In other words, the difference between the minimum LM and the maximum LP according to the third embodiment is larger, and the half width of the relative luminance is smaller. This is because the optical member OEC changes the traveling directions of the light having incident angles inclining in four azimuth angle directions, that is, the +Dy direction, the −Dy direction, the +Dx direction, and the −Dx direction with respect to the third direction Dz and directs the light in the third direction Dz. As described above, the display device  1 C according to the third embodiment can increase the relative luminance of light in the normal direction of the array substrate  2 . 
     Fourth Embodiment 
       FIG. 18  is a sectional view schematically illustrating a display device according to a fourth embodiment. As illustrated in  FIG. 18 , the optical member OE of a display device  1 D according to the fourth embodiment is provided on the cathode electrode  22 . In other words, the optical member OE is provided directly on the cathode electrode  22  without the overcoat layer OC (refer to  FIG. 5 ) interposed therebetween. Without the overcoat layer OC, the display device of the present embodiment can increase the amount of light incident on the optical member OE compared with the first embodiment. 
     The optical members OE, OEA, OEB, and OEC according to the first to the third embodiments and the modification described above can be used as the optical member OE illustrated in  FIG. 18 . 
     While exemplary embodiments according to the present disclosure have been described, the embodiments are not intended to limit the disclosure. The contents disclosed in the embodiments are given by way of example only, and various changes may be made without departing from the spirit of the present disclosure. Appropriate changes made without departing from the spirit of the present disclosure naturally fall within the scope of the disclosure. At least one of various omissions, substitutions, and changes of the components may be made without departing from the spirit of the embodiments above and the modification thereof.