Patent Publication Number: US-2021181816-A1

Title: Display device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation Application of PCT Application No. PCT/JP2019/023385, filed Jun. 12, 2019 and based upon and claiming the benefit of priority from Japanese Patent Application No. 2018-161676, filed Aug. 30, 2018, the entire contents of all of which are incorporated herein by reference. 
    
    
     FIELD 
     Embodiments described herein relate generally to a display device. 
     BACKGROUND 
     Recently, in a lateral electric field type liquid crystal display device, from the perspective of static buildup prevention or the like, a technology of electrically connecting a transparent conductive film disposed on a surface of one substrate and an electrode of a ground potential disposed in the other substrate by a conductive member has been known. A polarizer is disposed on the transparent conductive film. When the polarizer expands, the polarizer and the conductive member contact each other, and the contact area between the conductive member and the transparent conductive film may be reduced. In particular, in association with the demand for a narrower frame, the polarizer and the conductive member tend to be disposed close to each other, and are affected easily even by slight expansion of the polarizer. 
     SUMMARY 
     The present disclosure relates generally to a display device. 
     According to one embodiment, a display device includes a first insulating substrate including a first substrate end, a second insulating substrate including an outer surface and a second substrate end, an electrode located between the first substrate end and the second substrate end, and a transparent conductive layer disposed on a side on which the outer surface is located. The outer surface includes a flat portion and a sloping portion. A thickness on a side on which the second substrate end is located is less than a thickness on a side on which the flat portion is located. The transparent conductive layer overlaps the sloping portion and is electrically connected to the electrode. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view showing the external appearance of a display device DSP. 
         FIG. 2A  is a cross-sectional view of a display panel PNL in the first embodiment along line A-B shown in  FIG. 1 . 
         FIG. 2B  is another cross-sectional view of the display panel PNL along line A-B shown in  FIG. 1 . 
         FIG. 3  is another cross-sectional view of the display panel PNL along line A-B shown in  FIG. 1 . 
         FIG. 4  is a cross-sectional view of a display panel PNL in the second embodiment. 
         FIG. 5  is another cross-sectional view of the display panel PNL in the second embodiment. 
         FIG. 6  is a cross-sectional view of a display panel PNL in the third embodiment. 
         FIG. 7  is another cross-sectional view of the display panel PNL in the third embodiment. 
         FIG. 8  is a cross-sectional view of a display panel PNL in the fourth embodiment. 
         FIG. 9  is another cross-sectional view of the display panel PNL in the fourth embodiment. 
         FIG. 10  is a plan view of a display panel PNL in the fifth embodiment. 
         FIG. 11  is a cross-sectional view of the display panel PNL along line C-D shown in  FIG. 10 . 
         FIGS. 12A to 12D  are illustrations for explaining the first formation method of a sloping portion  22 . 
         FIG. 13  is an illustration showing a formation example of the sloping portion  22 . 
         FIG. 14  is an illustration showing another formation example of the sloping portion  22 . 
         FIG. 15  is an illustration showing another formation example of the sloping portion  22 . 
     
    
    
     DETAILED DESCRIPTION 
     In general, according to one embodiment, there is provided a display device comprising: a first insulating substrate comprising a first substrate end; a second insulating substrate comprising an inner surface opposed to the first insulating substrate, an outer surface on an opposite side to the inner surface, and a second substrate end; an electrode located between the first substrate end and the second substrate end and maintained at a predetermined potential; and a transparent conductive layer disposed on a side on which the outer surface is located. The outer surface comprises a flat portion and a sloping portion formed from the flat portion to the second substrate end. The sloping portion slopes such that a thickness on a side on which the second substrate end is located is less than a thickness on a side on which the flat portion is located. The transparent conductive layer overlaps the sloping portion and is electrically connected to the electrode. 
     Embodiments will be described hereinafter with reference to the accompanying drawings. The disclosure is merely an example, and proper changes in keeping with the spirit of the invention, which are easily conceivable by a person of ordinary skill in the art, come within 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 and the like, of the respective parts are illustrated schematically in the drawings, rather than as an accurate representation of what is implemented. However, such schematic illustration is merely exemplary, and in no way restricts the interpretation of the invention. In addition, in the specification and drawings, constituent elements which function in the same or a similar manner to those described in connection with preceding drawings are denoted by the same reference numbers, and detailed description of them which is considered redundant may be arbitrarily omitted. 
     In the embodiments, a liquid crystal display device will be described as an example of a display device DSP. The main configuration disclosed in the embodiments can also be applied to a self-luminous display device comprising an organic electroluminescent display element or the like, an electronic paper display device comprising an electrophoretic element or the like, a display device employing micro-electromechanical systems (MEMS), a display device employing electrochromism, and the like. 
     First Embodiment 
       FIG. 1  is a plan view showing the external appearance of a display device DSP. In one example, a first direction X, a second direction Y and a third direction Z are orthogonal to one another. However, they may cross one another at an angle other than 90 degrees. The first direction X and the second direction Y correspond to directions parallel to the main surface of a substrate constituting the display device DSP, and the third direction Z corresponds to the thickness direction of the display device DSP. For example, the first direction X corresponds to the short side direction of the display device DSP, and the second direction Y corresponds to the long side direction of the display device DSP. In the specification, an observation position from which the display device DSP is observed is assumed to be located on a side on which the tip of an arrow indicating the third direction Z is located, and viewing toward an XY-plane defined by the first direction X and the second direction Y from this observation position is referred to as planar view. 
     The display device DSP comprises a display panel PNL, a flexible printed circuit board  1 , an IC chip  2  and a circuit board  3 . 
     The display panel PNL is, for example, a liquid crystal display panel, and comprises a first substrate SUB 1 , a second substrate SUB 2 , and a liquid crystal layer LC which will be described later. The display panel PNL comprises a display portion DA which displays an image, and a frame-shaped non-display portion NDA which surrounds the display portion DA. The first substrate SUB 1  comprises a first region A 1  and a second region A 2  which are arranged in the second direction Y. The second substrate SUB 2  overlaps the first substrate SUB 1  in the first region A 1  but does not overlap the second region A 2 . The display portion DA is included in the first region A 1 . 
     The display portion DA comprises a plurality of pixels PX disposed in a matrix in the first direction X and the second direction Y. The pixel PX here indicates a minimum unit which can be individually controlled according to a pixel signal, and is referred to also as a sub-pixel. The pixel PX is, for example, any of a red pixel which displays red, a green pixel which displays green, a blue pixel which displays blue, and a white pixel which displays white. 
     The flexible printed circuit board  1  is mounted on the second region A 2  and is electrically connected to the circuit board  3 . The IC chip  2  is mounted on the flexible printed circuit board  1 . However, the IC chip  2  may be mounted on the second region A 2 . The IC chip  2  includes a built-in display driver DD. The display driver DD outputs a signal required for image display in an image display mode of displaying an image. In the example shown in  FIG. 1 , the IC chip  2  includes a built-in touch controller TC. The touch controller TC controls a touch sensing mode of detecting approach an object to or contact of an object with the display device DSP. 
     The first substrate SUB 1  comprises an electrode EL in the second region A 2 . The electrode EL is, for example, grounded via the flexible printed circuit board  1  but only has to be maintained at a predetermined potential. The predetermined potential is supplied to the electrode by a DC current having a ground potential or a fixed potential of several volts or an AC current having a predetermined amplitude. In the example shown in  FIG. 1 , the electrode EL is disposed in two places across the flexible printed circuit board  1 . However, the electrode EL may be disposed in only one place or three or more places. 
     The second substrate SUB 2  comprises a transparent conductive film CL as an example of a transparent conductive layer. The transparent conductive film CL is disposed over substantially the entire surface of the second substrate SUB 1  and overlaps the display portion DA. The transparent conductive film CL is formed of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO). 
     An optical element OD 2  overlaps the transparent conductive film CL. In addition, the optical element OD 2  overlaps the display portion DA and extends to the non-display portion NDA. 
     A connection member CN is located in the non-display portion NDA and electrically connects the electrode EL and the transparent conductive film CL. The connection member CN is formed of, for example, a resin material having conductivity. 
       FIG. 2A  is a cross-sectional view of the display panel PNL in the first embodiment along line A-B shown in  FIG. 1 . Note that only the configuration required for explanation is illustrated here, and the first substrate SUB 1  and the second substrate SUB 2  are simplified. In the specification, a direction from the first substrate SUB 1  toward the second substrate SUB 2  is referred to as an upper side (or simply as above), and a direction from the second substrate SUB 2  toward the first substrate SUB 1  is referred to as a lower side (or simply as below). When described as the second member above the first member and the second member below the first member, the second member may be in contact with the first member or apart from the first member. 
     In the display panel PNL, the liquid crystal layer LC is located between the first substrate SUB 1  and the second substrate SUB 2 . The first substrate SUB 1  comprises a first insulating substrate  10 , a circuit element  11 , the electrode EL and the like. The second substrate SUB 2  comprises a second insulating substrate  20  opposed to the first insulating substrate  10 , a light-shielding layer LS and the like. The first insulating substrate  10  and the second insulating substrate  20  are transparent substrates such as glass substrates or flexible resin substrates. 
     The first insulating substrate  10  comprises an inner surface  10 A opposed to the second insulating substrate  20 , an outer surface  10 B on an opposite side to the inner surface  10 A, and a first substrate end  10 C. The circuit element  11  is disposed on the inner surface  10 A, and includes a scanning line, a signal line, a switching element, a pixel electrode, a common electrode, an inorganic insulating film, an organic insulating film, an alignment film and the like. 
     The second insulating substrate  20  comprises an inner surface  20 A opposed to the first insulating substrate  10  in the first region A 1 , an outer surface  20 B on an opposite side to the inner surface  20 A, and a second substrate end  20 C. The second substrate end  20 C is located at the boundary between the first region A 1  and the second region A 2 . The light-shielding layer LS is disposed on the inner surface  20 A and is located in the non-display portion NDA. The boundary between the display portion DA and the non-display portion NDA is defined by, for example, an inner circumferential portion LSI of the light-shielding layer LS. A sealant SE is located in the non-display portion NDA, and bonds the first substrate SUB 1  and the second substrate SUB 2  together and seals in the liquid crystal layer LC. The sealant SE is disposed at a position overlapping the light-shielding layer LS. 
     The electrode EL is located between the first substrate end  10 C and the second substrate end  20 C. In addition, the electrode EL is located on the first insulating substrate  10  in the second region A 2 . The second substrate SUB 2  is not disposed on the electrode EL. 
     The transparent conductive film CL is disposed on the outer surface  20 B and is disposed over the display portion DA and the non-display portion NDA. The optical element OD 2  including a polarizer PL 2  is bonded to the transparent conductive film CL by a transparent adhesive layer AD. An optical element OD 1  including a polarizer PL 1  is bonded to the outer surface  10 B, but illustration of an adhesive layer is omitted. Each of the optical elements OD 1  and DO 2  may comprise a retarder, a scattering layer, an antireflective layer or the like as needed. 
     The connection member CN is superposed above the light-shielding layer LS in the second substrate SUB 2  and is in contact with the transparent conductive film CL. The connection member CN is in contact with the electrode EL in the first substrate SUB 1 . The connection member CN is in contact with the second substrate end  20 C and is disposed continuously between the transparent conductive film CL and the electrode EL. Accordingly, the transparent conductive film CL and the electrode EL are electrically connected via the connection member CN. 
     Now, attention is focused on the outer surface  20 B. The outer surface  20 B comprises a flat portion  21  and a sloping portion  22 . The flat portion  21  overlaps the display portion DA and is a flat surface formed along the XY-plane. The sloping portion  22  overlaps the non-display portion NDA and is located between the flat portion  21  and the second substrate end  20 C. The sloping portion  22  has a thickness T 1  in the vicinity of the flat portion  21  and a thickness T 2  in the vicinity of the second substrate end  20 C. Note that a thickness in the specification is a length along the third direction Z. 
     The thickness T 2  is less than the thickness T 1 . In addition, the difference between a thickness T 0  in the flat portion  21  and the thickness T 2  is, for example, greater than or equal to 0.1 mm, and the thickness T 2  is less than or equal to ½ of the thickness T 0 . In other words, the second insulating substrate  20  comprises a tapered portion in which the thickness decreases toward the second substrate end  20 C (or the electrode EL) in the non-display portion NDA. 
     Now, attention is focused on the relationship between a width LY of the sloping portion  22  and a height LZ of the sloping portion  22 . The width LY corresponds to the length along the second direction Y of the sloping portion  22 . The height LZ corresponds to the length LZ along the third direction Z of the sloping portion  22 . In one example, in the sloping portion  22  shown by a solid line, the width LY is equal to the height LZ or greater than the height LZ (LY≥LZ). In addition, in another example, the sloping portion  22  may be formed in a shape shown by a dashed double-dotted line. In this case, the width LY is less than the height LZ (LY&lt;LZ). 
     In the illustrated example, the sloping portion  22  is a flat surface crossing both the second direction Y and the third direction Z and hardly comprise projections and depressions. However the sloping portion  22  may be a surface having projections and depressions along the third direction Z. In addition, the sloping portion  22  may be a curved surface. Furthermore, the sloping portion  22  may be a flat surface crossing all the first direction X, the second direction Y and the third direction Z. 
     The inner surface  20 A is a flat surface formed along the XY-plane in the display portion DA and the non-display portion NDA, and is opposed to the flat portion  21  and the sloping portion  22 . 
     The transparent conductive film CL is disposed continuously in contact with both the flat portion  21  and the sloping portion  22 . In the illustrated example, the transparent conductive film CL is located between the sloping portion  22  and the connection member CN. In the first embodiment, the transparent conductive film CL is electrically connected to the electrode EL via the connection member CN. However, as will be described later, the transparent conductive film CL may be directly in contact with the electrode EL and electrically connected to the electrode EL. In addition, the transparent conductive film CL may be apart from the sloping portion  22 , and the transparent conductive film CL only has to be superposed above the sloping portion  22  in the third direction Z. 
     An end ODE of the optical element OD 2  and an end ADE of the adhesive layer AD are located in the non-display portion NDA. In the illustrated example, the end ODE and the end ADE are superposed above the flat portion  21 . However, they may be superposed above the sloping portion  22 , above the second substrate end  20 C, or between the first substrate end  10 C and the second substrate end  20 C. However, the adhesive layer AD is apart from the transparent conductive film CL above the sloping portion  22  and does not interfere with the contact between the connection member CN and the transparent conductive film CL. 
       FIG. 2B  is another cross-sectional view of the display panel PNL along line A-B shown in  FIG. 1 . The example shown in  FIG. 2B  is different from the example shown in  FIG. 2A  in that a thickness T 10  of the first insulating substrate  10  is greater than the thickness T 0  in the flat portion  21  of the second insulating substrate  20  (T 10 &gt;T 0 ). The other configuration is the same as that of the example shown in  FIG. 2A , and the constituent elements are denoted by the same reference numbers, and detailed description of them is omitted. 
       FIG. 3  is another cross-sectional view of the display panel PNL along line A-B shown in  FIG. 1 . The illustrated cross-sectional view shows a state where the optical element OD 2  and the adhesive layer AD shown in  FIG. 2A  expand along the second direction Y, for example. As indicated by an arrow YA in  FIG. 3 , when the optical element OD 2  and the adhesive layer AD expand along the second direction Y, the optical element OD 2  and the adhesive layer AD may be superposed above the sloping portion  22 . 
     In a comparative example where the second insulating substrate  20  does not comprise the sloping portion  22 , when the optical element OD 2  and the adhesive layer AD expand in the direction of the arrow YA, the connection member CN is pushed out in the direction of the arrow YA, and the contact area between the transparent conductive film CL and the connection member CN may be reduced. 
     On the other hand, according to the first embodiment, even when the optical element OD 2  and the adhesive layer AD expand in the direction of the arrow YA, the connection member CN contacting the transparent conductive film CL in the sloping portion  22  hardly moves. Therefore, the reduction of the contact area between the transparent conductive film CL and the connection member CN is suppressed. Accordingly, poor connection associated with the reduction of the contact area between the transparent conductive film CL and the connection member CN can be suppressed. Consequently, the reduction of reliability can be suppressed. 
     In addition, the transparent conductive film CL is disposed in the sloping portion  22  in which the thickness decreases toward the electrode EL, and the difference in level along the third direction Z between the transparent conductive film CL and the electrode EL is reduced. Therefore, the disconnection due to level difference of the connection member CN disposed over the transparent conductive film CL and the electrode EL can be suppressed. 
     Furthermore, a discharge path can be formed from the transparent conductive film CL to the electrode EL of the ground potential via the connection member CN, and the static buildup of the second substrate SUB 2  can be suppressed. Accordingly, the reduction of display quality due to static buildup can be suppressed. 
     Other embodiments will be described below. In each of the embodiments, only the configuration required for explanation will be illustrated and explained. 
     Second Embodiment 
       FIG. 4  is a cross-sectional view of the display panel PNL in the second embodiment. The second embodiment is different from the first embodiment in that the end ODE of the optical element OD 2  projects more toward the electrode EL than the end ADE of the adhesive layer AD. That is, a space SP is formed between the transparent conductive film CL and the optical element OD 2 . The space SP is filled with the connection member CN, and the connection member CN is in contact with the transparent conductive film CL directly below the optical element OD 2 . The ends ODE and ADE are both located in the non-display portion NDA. 
     As compared with the first embodiment in which the end ADE is located directly below the end ODE, the contact area between the connection member CN and the transparent conductive film CL is increased. 
       FIG. 5  is another cross-sectional view of the display panel PNL in the second embodiment. Even when the optical element OD 2  and the adhesive layer AD expand, the end ODE projects more toward the electrode EL than the end ADE. Therefore, the connection member CN remains between the end ODE and the end ADE, and the reduction of the volume of the connection member CN contacting the transparent conductive film CL is suppressed, and the increase of the electrical resistance of the connection member CN is suppressed. 
     Third Embodiment 
       FIG. 6  is a cross-sectional view of the display panel PNL in the third embodiment. The third embodiment is different from the first embodiment in comprising a low expansion layer LE between the adhesive layer AD and the optical element OD 2 . The thermal expansion coefficient of the low expansion layer LE is less than the thermal expansion coefficient of the optical element OD 2 . The low expansion layer LE is transparent and has optical isotropy (the retardation in the XY-plane is zero). For example, the low expansion layer LE is a support which supports a polarization layer and a retardation layer constituting the optical element OD 2 . 
     As compared with the first embodiment which does not comprise the low expansion layer LE, the optical element OD 2  is disposed more upward, and the contact area between the end ODE and the connection member CN is reduced. 
       FIG. 7  is another cross-sectional view of the display panel PNL in the third embodiment. Even when the optical element OD 2  expands, the amount of expansion of the low expansion layer LE and the adhesive layer AD is less than the amount of expansion of the optical element OD 2 . In addition, since the contact area between the end ODE and the connection member CN is reduced, the amount of pushing out of the connection member CN associated with expansion of the optical element OD 2  is reduced. 
     Fourth Embodiment 
       FIG. 8  is a cross-sectional view of the display panel PNL in the fourth embodiment. The fourth embodiment is different from the first embodiment in that the optical element OD 2  comprises a conductive adhesive agent CA which is another example of a transparent conductive layer. The adhesive agent CA contacts the flat portion  21  and bonds the optical element OD 2  to the flat portion  21 . In addition, the adhesive agent CA is apart from the sloping portion  22  above the sloping portion  22 . The connection member CN is located between the sloping portion  22  and the adhesive agent CA. That is, the adhesive agent CA of the fourth embodiment has the functions of both the transparent conductive film CL and the adhesive layer AD in the first embodiment. The adhesive agent CA is a conductive adhesive agent obtained by dispersing particles in an adhesive agent or the like. The adhesive agent CA is in contact with a lower surface ODB of the optical element OD 2 . The end ODE and an end CAE of the adhesive agent CA overlap the sloping portion  22  across the connection member CN. 
       FIG. 9  is another cross-sectional view of the display panel PNL in the fourth embodiment. When the optical element OD 2  and the adhesive agent CA expand, in particular, in a region overlapping the sloping portion  22 , an area in which the adhesive agent CA overlaps the sloping portion  22  increases according to the expansion. At this time, the connection member CN disposed in the sloping portion  22  hardly moves. Therefore, when the optical element OD 2  and the adhesive agent CA expand, the contact area between the adhesive agent CA and the connection member CN increases, and reliability improves. 
     In addition, the adhesive agent CA has the functions of both the transparent conductive film for static buildup prevention and the adhesive layer of the optical element OD 2 . Therefore, the display panel PNL is made thinner, and the number of components can be reduced. Furthermore, as compared with when the transparent conductive film is formed separately by depositing a transparent conductive material, the formation cost of the transparent conductive film can be reduced. 
     Furthermore, although the first embodiment shown in  FIG. 3  requires the region for disposing the connection member CN between the end ODE of the optical element OD 2  and the second substrate end  20 C along the second direction Y, the fourth embodiment does not require the region for disposing the connection member CN between the end ODE and the second substrate end  20 C. Therefore, as compared with the first embodiment, the fourth embodiment can achieve an even narrower frame. 
     Fifth Embodiment 
       FIG. 10  is a plan view of the display panel PNL in the fifth embodiment. The optical element OD 2  applied to the fifth embodiment comprises a main body MP and an extension portion EP. The main body MP is superposed above the second substrate SUB 2 . The extension portion EP extends between the first substrate end  10 C and the second substrate end  20 C and is superposed above the electrode EL. 
       FIG. 11  is a cross-sectional view of the display panel PNL along line C-D shown in  FIG. 10 . Similarly to the fourth embodiment, the adhesive agent CA bonds the optical element OD 2  to the second substrate SUB 2  and the electrode EL. The adhesive agent CA is disposed continuously in contact with the flat portion  21 , the sloping portion  22  and the electrode EL. The adhesive agent CA bonds the main body MP to the flat portion  21  and the sloping portion  22 . In addition, the adhesive agent CA bonds the extension portion EP to the electrode EL between the first substrate end  10 C and the second substrate end  20 C. 
     Even when the optical element OD 2  expands, the contact area between the adhesive agent CA and the electrode EL hardly changes. 
     In addition, the adhesive agent CA has the functions of the transparent conductive film for static buildup prevention, the adhesive layer of the optical element OD 2 , and the connection member connected to the electrode EL. Therefore, the number of components can be reduced. Furthermore, as compared with when the transparent conductive material and the connection member are formed separately, the cost can be reduced. 
     &lt;&lt;First Formation Method of Sloping Portion&gt;&gt; 
     Now, the first formation method of the sloping portion  22  will be described with reference to  FIGS. 12A to 12D . Only the main parts of the first substrate SUB 1  and the second substrate SUB 2  are illustrated here. 
     As shown in  FIG. 12A , in a mother substrate MSUB composed of the first substrate SUB 1  and the second substrate SUB 2  bonded together, laser light is emitted from the outer surface  20 B side of the second insulating substrate  20 , and the laser light is condensed inside the second insulating substrate  20 . As the light source at this time, from the perspective of hardly damaging the periphery of a condensing part  20 X of laser light either thermally or chemically, a femtosecond laser device which emits laser light having a pulse width of femtoseconds is preferable. As the laser light is emitted, the condensing part  20 X is modified. In addition, the condensing part  20 X is formed in a plurality of places, and for example, from the liquid crystal layer LC toward the electrode EL along the second direction Y, the condensing part  20 X is formed such that it recedes from the first substrate SUB 1  along the third direction Z. 
     Then, as shown in  FIG. 12B , the first insulating substrate  10  and the second insulating substrate  20  are reduced in thickness. For example, the first insulating substrate  10  and the second insulating substrate  20  are glass substrates, and are reduced in thickness by dissolution by an etching solution such as a hydrofluoric acid (HF) solution. In addition, the condensing part  20 X shown in  FIG. 12A  is dissolved by the etching solution more easily than a part of glass in which the laser light is not condensed. Therefore, when the condensing part  20  is exposed to the etching solution in association with the reduction of the thickness of the second insulating substrate  20 , a concave portion CC depressed toward the first insulating substrate  10  is formed on the outer surface  20 B. 
     Then, as shown in  FIG. 12C , the transparent conductive film CL is formed by depositing a transparent conductive material on the entire surface of the outer surface  20 B including the concave portion CC. 
     Then, as shown in  FIG. 12D , a part of the second insulating substrate  20  which is opposed to the electrode EL is removed. Accordingly, the second insulating substrate  20  comprising the flat portion  21  and the sloping portion  22  is formed. 
     After that, although not illustrated, the optical element OD 2  is bonded to the transparent conductive film CL by the adhesive layer AD. After that, a resin material having conductivity is applied continuously from the transparent conductive film CL above the sloping portion  22  to the electrode EL. The cured resin material corresponds to the connection member CN described above. Accordingly, the transparent conductive film CL and the electrode EL are electrically connected by the connection member CN. The display panels PNL of the first to third embodiments described above are obtained by applying the first formation method described here. 
     In addition, the deposition process of the transparent conductive material described in  FIG. 12C  may be omitted, and the optical element OD 2  may be bonded to the flat portion  21  by the adhesive agent CA, and the connection member CN may be formed between the adhesive agent CA and the electrode EL. The display panel PNL of the fourth embodiment described above can be obtained by applying this formation method. 
     Furthermore, not only the deposition process of the transparent conductive material described in  FIG. 12C  but also the formation process of the connection member CN may be omitted, and the main body MP of the optical element OD 2  may be bonded to the flat portion  21  and the sloping portion  22  and the extension portion EP may be bonded to the electrode EL by the adhesive agent CA. The display panel PNL of the fifth embodiment described above can be obtained by applying this formation method. 
     The sloping portion  22  is a portion sloping downward from the flat portion  21  toward the second substrate end  20 C in the second insulating substrate  22 , and includes not only a sloping portion having a flat sloping surface but also a sloping portion having a sloping surface which is made slightly bumpy or uneven by the first formation method or the like. 
     &lt;&lt;Second Formation Method of Sloping Portion&gt;&gt; 
     In the second formation method, the sloping portion  22  is formed by mechanically grinding the second insulating substrate  20  by a grindstone or the like. This sloping portion  22  is formed such that it is adjacent to the electrode EL in the second direction Y. 
     In the example shown in  FIG. 13 , the sloping portion  22  is formed in a substantially rectangular shape. This sloping portion  22  is a surface crossing both the second direction Y and the third direction Z and extending parallel to the first direction X. A boundary B between the flat portion  21  and the sloping portion  22  extends along the first direction X in the XY-plane. A thickness T along the third direction Z of the sloping portion  22  decreases from the flat portion  21  toward the electrode EL along the second direction Y. Note that the thickness T of the sloping portion  22  is substantially constant along the first direction X. 
     In the example shown in  FIG. 14 , the sloping portion  22  is formed in a substantially triangular shape. This sloping portion  22  is a surface crossing all the first direction X, the second direction Y and the third direction Z. The boundary B between the flat portion  21  and the sloping portion  22  crosses both the first direction X and the second direction Y in the XY-plane. The thickness T of the sloping portion  22  decreases from the flat portion  21  toward the electrode EL along the first direction X and the second direction Y. 
     In the example shown in  FIG. 15 , the first insulating substrate  10  and the second insulating substrate  20  comprise concave portions C 1  and C 2 , respectively. The concave portions C 1  and C 2  are formed in a region different from a region in which the flexible printed circuit board  1  is mounted. The sloping portion  22  is disposed in the concave portion C 2 . This sloping portion  22  is formed, for example, in a grinding process of forming the concave portions C 1  and C 2 . 
     After the sloping portion  22  described with reference to  FIGS. 13 to 15  is formed, the display panels PNL of the first to third embodiments described above are obtained by forming the transparent conductive film CL on the flat portion  21  and the sloping portion  22 , bonding the optical element OD 2  to the transparent conductive film CL by the adhesive layer AD, and electrically connecting the transparent conductive film CL and the electrode EL by the connection member CN. 
     In addition, after the sloping portion  22  is formed, the display panel PNL of the fourth embodiment described above is obtained by bonding the optical element OD 2  to the flat portion  21  by the adhesive agent CA, and forming the connection member CN between the adhesive agent CA and the electrode EL. 
     Furthermore, after the sloping portion  22  is formed, the display panel PNL of the fifth embodiment described above is obtained by bonding the main body MP of the optical element OD 2  to the flat portion  21  and the sloping portion  22 , and bonding the extension portion EP to the end portion EL. 
     As described above, according to the embodiments, a display device which can suppress reduction of reliability can be provided. 
     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.