Display device

Abstract

According to the present invention, a TFT layer (30a) includes: a drain electrode (18d), a first inorganic insulating film (19), a first planarizing film (20), a second inorganic insulating film (21), and a relay electrode (22a) which are provided in the stated order; and a contact hole (Ha) which is for electrically connecting the relay electrode (22a) to the drain electrode (18d) and in which first, second, and third contact holes (H19, H20, H21) respectively formed on the first inorganic insulating film (19), the first planarizing film (20), and the second inorganic insulating film (21) are arranged in an overlapping manner. In a plan view, the opening (O21) of the third contact hole (H21) and the opening (O19) of the first contact hole (H19) partially overlap each other.

Description

display device

[0001] The present invention relates to a display device.

[0002] In recent years, self-luminous organic electroluminescence (EL) display devices using organic electroluminescence (EL) elements have been attracting attention as a display device alternative to liquid crystal display devices. In an organic EL display device, a display area for displaying an image is formed, and multiple thin film transistors (TFTs) are provided for each subpixel, which is the smallest unit of an image. For example, in a TFT having a stacked structure in which a lower conductive layer, a stacked film made of multiple interlayer films, and an upper conductive layer are stacked in this order, contact holes for electrically connecting the lower conductive layer and the upper conductive layer are formed in each of the multiple interlayer films. In a stacked contact hole structure in which multiple contact holes from different layers are stacked, there is a risk of discontinuities in the conductive layer at the boundary between the contact holes.

[0003] For example, Patent Document 1 proposes a stacked contact hole structure (upper layer side > lower layer side) in which multiple contact holes are formed such that the contact holes on the upper layer side are larger than the contact holes on the lower layer side in order to prevent discontinuities in the conductive layer at the boundary between the contact holes.

[0004] JP 2008-122758 A

[0005] In the structure of Patent Document 1 (upper layer side > lower layer side), when forming the contact hole on the upper layer side, the upper conductive layer covering the contact hole on the upper layer side may be cut off at the dug-in portion of the underlayer film due to the multiple interlayer films (underlayer films) located below it being dug.

[0006] On the other hand, if a stacked contact hole structure (upper layer side < lower layer side) is used in which the contact hole on the upper layer side is smaller than the contact hole on the lower layer side, there is a risk of poor opening if the contact hole on the upper layer side has a fine pattern.

[0007] The present invention has been made in consideration of these points, and its purpose is to suppress discontinuity of the conductive layer at the boundary of the contact holes in a stacked contact hole structure in which multiple contact holes in different layers are arranged on top of each other.

[0008] In order to achieve the above object, the display device of the present invention comprises a base substrate and a thin film transistor layer provided on the base substrate, the thin film transistor layer having, in order, a lower conductive layer, a first inorganic insulating film, a planarization film, a second inorganic insulating film and an upper conductive layer, and a contact hole for electrically connecting the upper conductive layer to the lower conductive layer, the contact hole being formed in a stacked contact hole structure in which a first contact hole formed in the first inorganic insulating film, a second contact hole formed in the planarization film and a third contact hole formed in the second inorganic insulating film are arranged in a stacked manner, and is characterized in that, in a planar view, the opening of the third contact hole and the opening of the first contact hole partially overlap each other.

[0009] According to the present invention, in a stacked contact hole structure in which a plurality of contact holes in different layers are arranged one on top of the other, it is possible to suppress discontinuities in the conductive layer at the boundary between the contact holes.

[0010] FIG. 1 is a plan view showing a schematic configuration of an organic EL display device according to a first embodiment of the present invention. FIG. 2 is a plan view of a display region of the organic EL display device according to the first embodiment of the present invention. FIG. 3 is a cross-sectional view of a display region of the organic EL display device according to the first embodiment of the present invention. FIG. 4 is a schematic plan view showing the positional relationship of a first contact hole, a second contact hole, and a third contact hole constituting a contact hole formed in a TFT layer of the organic EL display device according to the first embodiment of the present invention. FIG. 5 is an enlarged cross-sectional view taken along line V-V in FIG. 4 , showing the vicinity of a contact hole formed in a TFT layer of the organic EL display device according to the first embodiment of the present invention. FIG. 6 is an equivalent circuit diagram of a TFT layer constituting the organic EL display device according to the first embodiment of the present invention. FIG. 7 is a cross-sectional view of an organic EL layer constituting the organic EL display device according to the first embodiment of the present invention. FIG. 8 is an enlarged cross-sectional view corresponding to FIG. 5 , showing the vicinity of a contact hole formed in a TFT layer of an organic EL display device according to a second embodiment of the present invention.

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments.

[0012] First Embodiment FIGS. 1 to 7 illustrate a first embodiment of a display device according to the present invention. In the following embodiments, an organic EL display device including organic EL elements will be exemplified as a display device including light-emitting elements. FIG. 1 is a plan view showing a schematic configuration of an organic EL display device 50a according to this embodiment. FIG. 2 is a plan view of a display region D of the organic EL display device 50a. FIG. 3 is a cross-sectional view of the display region D of the organic EL display device 50a. FIG. 4 is a schematic plan view showing the positional relationship of a first contact hole H19, a second contact hole H20, and a third contact hole H21 that constitute a contact hole Ha formed in a TFT layer 30a (thin-film transistor layer) of the organic EL display device 50a. FIG. 5 is an enlarged cross-sectional view taken along line V-V in FIG. 4 , showing the vicinity of the contact hole Ha formed in the TFT layer 30a of the organic EL display device 50a. FIG. 6 is an equivalent circuit diagram of the TFT layer 30a that constitutes the organic EL display device 50a. FIG. 7 is a cross-sectional view of an organic EL layer 33 that constitutes the organic EL display device 50a. 4, layers other than the drain electrode 18d and the contact hole Ha are omitted. In FIG. 5, the lower layer of the second interlayer insulating film 17 and the upper layer of the second planarizing film 24 are omitted.

[0013] 1 , the organic EL display device 50a includes, for example, a rectangular display area D for displaying images, and a frame area F provided in a frame shape around the display area D. While the present embodiment illustrates a rectangular display area D, this rectangular shape also includes substantially rectangular shapes such as shapes with arc-shaped sides, shapes with arc-shaped corners, and shapes with notches in some of the sides. In the organic EL display device 50a, a direction X parallel to the substrate surface of a resin substrate 10 (described later), and a direction Y perpendicular to the direction X and parallel to the substrate surface, are defined.

[0014] In the display region D, a plurality of sub-pixels P are arranged in a matrix, as shown in Fig. 2. In the display region D, for example, a sub-pixel P having a red light-emitting region Lr for displaying red, a sub-pixel P having a green light-emitting region Lg for displaying green, and a sub-pixel P having a blue light-emitting region Lb for displaying blue are arranged adjacent to one another, as shown in Fig. 2. In the display region D, one pixel is formed by, for example, three adjacent sub-pixels P each having a red light-emitting region Lr, a green light-emitting region Lg, and a blue light-emitting region Lb. The arrangement of the sub-pixels P is not particularly limited, and examples thereof include a pentatile arrangement and a stripe arrangement.

[0015] A terminal portion T is provided at one end (the right end in FIG. 1 ) of the frame region F so as to extend in one direction (direction Y, the vertical direction in FIG. 1 ). A folding portion (not shown) that can be folded, for example, 180° (in a U-shape) with direction X as the folding axis may be provided in the frame region F between the display region D and the terminal portion T so as to extend in one direction (direction Y).

[0016] As shown in FIG. 3, the organic EL display device 50a includes a resin substrate 10 provided as a base substrate, a TFT layer 30a provided on the resin substrate 10, an organic EL element layer 40 provided as a light-emitting element layer that constitutes the display area D, and a sealing film 45 provided on the organic EL element layer 40.

[0017] The resin substrate 10 is made of an organic resin material such as polyimide resin.

[0018] As shown in FIG. 3, the TFT layer 30a includes a base coat film 11 provided on a resin substrate 10, a plurality of first TFTs 9a, a plurality of second TFTs 9b, a plurality of third TFTs 9c, and a plurality of capacitors 9d provided on the base coat film 11 for each subpixel P, and a first inorganic insulating film 19, a first planarization film 20, a second inorganic insulating film 21, and a second planarization film 24 provided on each of the first TFTs 9a, each of the second TFTs 9b, each of the third TFTs 9c, and each of the capacitors 9d.

[0019] As shown in FIG. 3 , in the TFT layer 30 a, a base coat film 11, a semiconductor film that will become the semiconductor layers 12 a, 12 b, etc., a gate insulating film 13, a first metal film that will become the gate electrodes 14 a, 14 b, the lower conductive layer 14 c, the gate line 14 g (see FIGS. 2 and 6 ), the light-emitting control line 14 e (see FIGS. 2 and 6 ), etc., a first interlayer insulating film 15, a second metal film that will become the upper conductive layer 16 c, etc., a second interlayer insulating film 17, a third metal film that will become the source line 18 f (see FIGS. 2 and 6 ), the power supply line 18 g (see FIGS. 2 and 6 ), the source electrodes 18 a, 18 c, the drain electrodes 18 b, 18 d, etc., a first inorganic insulating film 19, a first planarization film 20, a second inorganic insulating film 21, a fourth metal film that will become the relay electrode 22 a, the metal layer 22 b, etc., and a second planarization film 24 are laminated in this order on a resin substrate 10.

[0020] The base coat film 11, the gate insulating film 13, the first interlayer insulating film 15, the second interlayer insulating film 17, the first inorganic insulating film 19, and the second inorganic insulating film 21 may be made of, for example, silicon nitride (SiNx (x is a positive number)), silicon oxide (SiO ２ The semiconductor layers 12a and 12b are each composed of a single layer or a stacked layer of an inorganic insulating film such as silicon oxynitride (SiON). The semiconductor layers 12a and 12b are composed of, for example, a low-temperature polysilicon film or an In—Ga—Zn—O-based oxide semiconductor film. The first metal film, the second metal film, the third metal film, and the fourth metal film are each composed of, for example, a metal single layer film of molybdenum (Mo), titanium (Ti), aluminum (Al), copper (Cu), tungsten (W), or the like, or a metal stacked layer film of Mo (upper layer) / Al (middle layer) / Mo (lower layer), Ti / Al / Ti, Al (upper layer) / Ti (lower layer), Cu / Mo, Cu / Ti, or the like.

[0021] As shown in FIG. 2 , the TFT layer 30a is provided with a plurality of gate lines 14g extending parallel to one another in the X direction in the figure. The TFT layer 30a is also provided with a plurality of light-emitting control lines 14e extending parallel to one another in the X direction in the figure. Each light-emitting control line 14e is provided adjacent to a corresponding gate line 14g. The TFT layer 30a is also provided with a plurality of source lines 18f extending parallel to one another in the Y direction in the figure. The TFT layer 30a is also provided with a plurality of power supply lines 18g extending parallel to one another in the Y direction in the figure. Each power supply line 18g is provided adjacent to a corresponding source line 18f. As shown in FIG. 6 , the TFT layer 30a includes a first TFT 9a, a second TFT 9b, a third TFT 9c, and a capacitor 9d in each sub-pixel P. The first TFT 9a, the second TFT 9b, and the third TFT 9c are p-type TFTs in which the semiconductor layers 12a, 12b, etc. are doped with impurities such as boron.

[0022] As shown in FIG. 6 , the first TFT 9a is electrically connected to the corresponding gate line 14g, source line 18f, and second TFT 9b in each subpixel P. As shown in FIG. 3 , the first TFT 9a includes a semiconductor layer 12a provided on a base coat film 11, a gate electrode 14a provided on the semiconductor layer 12a via a gate insulating film 13, and a source electrode 18a and a drain electrode 18b provided spaced apart on a second interlayer insulating film 17. The semiconductor layers 12a and 12b are semiconductor films made of, for example, an In—Ga—Zn—O-based oxide semiconductor, and are provided in island shapes on the base coat film 11 as shown in FIG. 3 . The semiconductor layers 12a and 12b include source and drain regions defined spaced apart from each other and a channel region defined between the source and drain regions. The gate electrode 14a is provided so as to overlap the channel region of the semiconductor layer 12a and is configured to control conduction between the source electrode 18a and the drain electrode 18b. As shown in FIG. 3, the source electrode 18a and the drain electrode 18b are electrically connected to the source region and the drain region of the semiconductor layer 12a, respectively, through contact holes formed in the stacked film of the gate insulating film 13, the first interlayer insulating film 15, and the second interlayer insulating film 17.

[0023] 6, the second TFT 9b is electrically connected to the corresponding first TFT 9a, power supply line 18g, and third TFT 9c in each subpixel P. The second TFT 9b has substantially the same structure as the first TFT 9a and the third TFT 9c.

[0024] As shown in FIG. 6 , in each subpixel P, the third TFT 9c is electrically connected to the corresponding second TFT 9b, a first electrode 31 of an organic EL element 35 (described later), and an emission control line 14e. As shown in FIG. 3 , the third TFT 9c includes a semiconductor layer 12b provided on the base coat film 11, a gate electrode 14b provided on the semiconductor layer 12b via a gate insulating film 13, and a source electrode 18c and a drain electrode 18d provided spaced apart from each other on the second interlayer insulating film 17. The gate electrode 14b is provided to overlap a channel region of the semiconductor layer 12b and is configured to control conduction between the source electrode 18c and the drain electrode 18d. As shown in FIG. 3 , the source electrode 18c and the drain electrode 18d are electrically connected to the source region and the drain region of the semiconductor layer 12b, respectively, via contact holes formed in the stacked film of the gate insulating film 13, the first interlayer insulating film 15, and the second interlayer insulating film 17.

[0025] In this embodiment, the first TFT 9a, the second TFT 9b, and the third TFT 9c are illustrated as being of a top gate type, but the first TFT 9a, the second TFT 9b, and the third TFT 9c may be of a bottom gate type.

[0026] 6, the capacitor 9d is electrically connected to the corresponding first TFT 9a and power supply line 18g in each subpixel P. Here, as shown in FIG. 3, the capacitor 9d includes a lower conductive layer 14c formed of a first metal film, a first interlayer insulating film 15 provided so as to cover the lower conductive layer 14c, and an upper conductive layer 16c formed of a second metal film on the first interlayer insulating film 15 so as to overlap the lower conductive layer 14c. The upper conductive layer 16c is electrically connected to the power supply line 18g via a contact hole (not shown) formed in the second interlayer insulating film 17.

[0027] The first planarization film 20 and the second planarization film 24 have flat surfaces in the display region D and are made of, for example, an organic resin material such as polyimide resin or acrylic resin, or a polysiloxane-based SOG (spin on glass) material.

[0028] 3, a relay electrode 22a (an upper conductive layer, described later) and a metal layer 22b, which are formed in the same layer and from the same material as the fourth metal film, are provided between the first planarization film 20 and the second planarization film 24. The metal layer 22b is configured to be electrically connected to the source line 18f and the power supply line 18g via contact holes (not shown) formed in the stacked film of the first inorganic insulating film 19, the first planarization film 20, and the second inorganic insulating film 21, for example, for each subpixel P, thereby reducing the electrical resistance of the source line 18f and the power supply line 18g.

[0029] The TFT layer 30a configured as described above has a lower conductive layer, a first inorganic insulating film 19, a planarizing film, a second inorganic insulating film 21, and an upper conductive layer, which are provided in this order on the second interlayer insulating film 17, as shown in Figures 3 and 5.

[0030] The lower conductive layer refers to a conductive layer located below the upper conductive layer. Examples of the lower conductive layer include electrodes formed in the same layer and made of the same material as the third metal film, such as the source electrode 18a and drain electrode 18b of the first TFT 9a and the source electrode 18c and drain electrode 18d of the third TFT 9c. The lower conductive layer will be described below using the drain electrode 18d as an example.

[0031] 3 and 5 , the first inorganic insulating film 19 is provided on the second interlayer insulating film 17 and the lower conductive layer. The first inorganic insulating film 19 is provided so as to cover the lower conductive layer. The peripheral edge of the drain electrode 18d (lower conductive layer) is covered with the first inorganic insulating film 19. As shown in FIG. 5 , a plurality of first contact holes H19 are formed in the first inorganic insulating film 19 for each sub-pixel P.

[0032] 3 and 5, the planarization film is provided on the first inorganic insulating film 19. The planarization film will be described below using the first planarization film 20 as an example. As shown in FIG. 5, a plurality of second contact holes H20 are formed in the first planarization film 20 for each sub-pixel P.

[0033] 3 and 5, the second inorganic insulating film 21 is provided on the first planarization film 20. As shown in Fig. 5, a plurality of third contact holes H21 are formed in the second inorganic insulating film 21 for each sub-pixel P.

[0034] The upper conductive layer refers to a conductive layer located above the lower conductive layer. The upper conductive layer will be described below using the relay electrode 22a formed in the same layer and made of the same material as the fourth metal film as an example. As shown in FIG. 3 , the relay electrode 22a is electrically connected to the first electrode 31 of the organic EL element 35 (described later). As shown in FIGS. 3 and 5 , the relay electrode 22a is also formed to cover at least a portion of the inner wall surface of the contact hole Ha (described later). The relay electrode 22a is electrically connected to the drain electrode 18d (lower conductive layer) of the third TFT 9c exposed through the contact hole Ha. Therefore, the relay electrode 22a electrically connects the drain electrode 18d and the first electrode 31.

[0035] As shown in FIG. 5 , the TFT layer 30a includes a first contact hole H19, a second contact hole H20, and a third contact hole H21, which form a single contact hole Ha. The contact hole Ha is formed in a stacked film of the first inorganic insulating film 19, the first planarization film 20, and the second inorganic insulating film 21. Therefore, the contact hole Ha has a stacked contact hole structure in which three contact holes (the first contact hole H19, the second contact hole H20, and the third contact hole H21) from different layers are stacked. The contact hole Ha is formed to expose at least a portion of the drain electrode 18d (lower conductive layer). The contact hole Ha electrically connects the lower conductive layer and the upper conductive layer.

[0036] In a conventional stacked contact hole structure (upper layer < lower layer) in which the contact hole formed in the upper inorganic insulating film is smaller than the contact hole formed in the lower inorganic insulating film, if the upper contact hole has a fine pattern, there is a concern that the opening of the upper contact hole will be insufficient due to poor exposure resolution of the upper contact hole. Specifically, in a structure in which an even smaller upper contact hole is formed within a lower contact hole, the resist film becomes thick, which makes the opening of the upper contact hole more likely to be insufficient.

[0037] In contrast to the above structure, in a conventional stacked contact hole structure (upper layer > lower layer) in which the contact hole formed in the upper inorganic insulating film is larger than the contact hole formed in the lower inorganic insulating film, when the upper inorganic insulating film is etched, the taper of the planarizing film interposed between the upper inorganic insulating film and the lower inorganic insulating film becomes steep, which raises concerns about step disconnection of the upper conductive layer.

[0038] In contrast, in the organic EL display device 50a, in the stacked contact hole structure, the third contact hole H21 on the upper layer and the first contact hole H19 on the lower layer are not different in size (opening diameter). Instead, as shown in FIG. 4 , the opening O21 of the third contact hole H21 and the opening O19 of the first contact hole H19 partially overlap each other in a planar view. Note that the opening O19 of the first contact hole H19 refers to the opening of a through-hole in the first inorganic insulating film 19 that exposes at least a portion of the drain electrode 18d, as shown in FIG. 5 . The opening O21 of the third contact hole H21 refers to the opening of a through-hole in the second inorganic insulating film 21 that exposes at least a portion of the drain electrode 18d, the first contact hole H19, and the first planarization film 20, as shown in FIG. 4 . In other words, as shown in FIG. 4 , the opening O21 of the third contact hole H21 does not entirely overlap the opening O19 of the first contact hole H19 in a planar view. In plan view, the opening O21 of the third contact hole H21 does not entirely (completely) overlap with the opening O19 of the first contact hole H19, but only partially. In other words, the center of the opening O21 of the third contact hole H21 is located at a different position from the center of the opening O19 of the first contact hole H19 (the centers are misaligned). In this way, in the organic EL display device 50a, the upper third contact hole H21 and the lower first contact hole H19 form a half-overlap structure in the stacked contact hole structure.

[0039] In the organic EL display device 50a, as shown in Fig. 5, by using the half-hanging structure for the stacked contact hole structure, a step C22a is formed on at least a portion of the inner wall surface of the contact hole Ha, where the relay electrode 22a (upper conductive layer) is not provided. As shown in Figs. 4 and 5, the step C22a is a portion of the contact hole Ha where the periphery of the opening O19 of the first contact hole H19 (and the opening O20 of the second contact hole H20) is located inside the periphery of the opening O21 of the third contact hole H21. Meanwhile, a current path CP electrically connecting the relay electrode 22a (upper conductive layer) and the drain electrode 18d (lower electrode) is secured on the inner wall surface of the contact hole Ha on the side opposite (opposite) the step C22a. 4 and 5, the inner wall surface portion on the opposite side to the step discontinuity C22a is the portion of the contact hole Ha where the periphery of the opening O19 of the first contact hole H19 (and the opening O20 of the second contact hole H20) is located outside the periphery of the opening O21 of the third contact hole H21. In this way, in the organic EL display device 50a, by intentionally shifting the position of the opening O21 of the third contact hole H21 with respect to the opening O19 of the first contact hole H19, problems such as poor opening of the upper contact hole and step discontinuity in the upper conductive layer, which are concerns in conventional stacked contact hole structures, are reduced.

[0040] The size (opening diameter) of the opening O21 of the third contact hole H21 and the opening O19 of the first contact hole H19 may be equal to each other or may be different within a range that does not impede the object of the present invention.

[0041] 5, the periphery of the opening O20 of the second contact hole H20 is located outside the periphery of the opening O19 of the first contact hole H19. The opening O20 of the second contact hole H20 refers to the opening of a through-hole in the first planarization film 20 that exposes at least a portion of the drain electrode 18d and the first contact hole H19, as shown in FIG. 5. In other words, as shown in FIG. 4, the entire opening O19 of the first contact hole H19 overlaps with the opening O20 of the second contact hole H20 in a planar view. Furthermore, due to the above-described half-overlap structure, the opening O21 of the third contact hole H21 and the opening O20 of the second contact hole H20 partially overlap with each other in a planar view. In other words, the entire opening O21 of the third contact hole H21 does not overlap with the opening O20 of the second contact hole H20 in a planar view. In plan view, the opening O21 of the third contact hole H21 does not entirely (completely) overlap with the opening O20 of the second contact hole H20, but only partially. In other words, the center of the opening O21 of the third contact hole H21 is located at a different position from the center of the opening O20 of the second contact hole H20 (the centers are misaligned). The opening O21 of the third contact hole H21 and the opening O20 of the second contact hole H20 may have the same size (opening diameter) or may differ from each other as long as the object of the present invention is not impaired.

[0042] As shown in FIG. 3, the organic EL element layer 40 includes a plurality of organic EL elements 35 as a plurality of light-emitting elements arranged in a matrix corresponding to a plurality of sub-pixels P.

[0043] 3, the organic EL element 35 includes a plurality of first electrodes 31 provided in order on the second planarization film 24, a plurality of organic EL layers 33 provided on the first electrodes 31 in respective sub-pixels P, and a second electrode 34 provided on the organic EL layer 33 in common to the plurality of sub-pixels P. In addition, the organic EL element 35 is covered with a sealing film 45 as shown in FIG.

[0044] As shown in FIG. 3 , the first electrodes 31 are provided in a matrix on the second planarization film 24 so as to correspond to the plurality of subpixels P. As shown in FIG. 3 , the first electrodes 31 are electrically connected to the relay electrodes 22 a of each subpixel via contact holes Hb formed in the second planarization film 24. The first electrodes 31 are electrically connected to the drain electrodes 18 d (or source electrodes 18 c) of each third TFT 9 c via the relay electrodes 22 a. The first electrodes 31 also have the function of injecting holes (positive holes) into the organic EL layer 33. It is preferable that the first electrodes 31 be made of a material with a large work function in order to improve the efficiency of hole injection into the organic EL layer 33. Here, examples of materials constituting the first electrode 31 include metal materials such as silver (Ag), aluminum (Al), vanadium (V), cobalt (Co), nickel (Ni), tungsten (W), gold (Au), titanium (Ti), ruthenium (Ru), manganese (Mn), indium (In), ytterbium (Yb), lithium fluoride (LiF), platinum (Pt), palladium (Pd), molybdenum (Mo), iridium (Ir), and tin (Sn). Examples of materials constituting the first electrode 31 include astatine (At) / astatine oxide (AtO ２ The first electrode 31 may be made of an alloy of tin oxide (SnO), zinc oxide (ZnO), indium tin oxide (ITO), indium zinc oxide (IZO), or another conductive oxide. The first electrode 31 may be formed by stacking multiple layers made of the above materials. Examples of compound materials with a large work function include indium tin oxide (ITO) and indium zinc oxide (IZO).

[0045] The peripheral edge of the first electrode 31 is covered with an edge cover 32 provided in a lattice pattern and shared by multiple sub-pixels P. Examples of materials that form the edge cover 32 include positive photosensitive resin materials such as polyimide resin, acrylic resin, polysiloxane resin, and novolac resin, as well as polysiloxane-based SOG materials. As shown in FIG. 3 , a portion of the surface of the edge cover 32 protrudes upward in the drawing to form island-shaped pixel photospacers.

[0046] 3, the organic EL layer 33 is disposed on each first electrode 31 and is provided in a matrix so as to correspond to a plurality of sub-pixels P. Here, each organic EL layer 33 includes a hole injection layer 1, a hole transport layer 2, a light-emitting layer 3, an electron transport layer 4, and an electron injection layer 5, which are provided in this order on the first electrode 31, as shown in FIG.

[0047] The hole injection layer 1 is also called an anode buffer layer, and has the function of bringing the energy levels of the first electrode 31 and the organic EL layer 33 closer to each other, thereby improving the efficiency of hole injection from the first electrode 31 to the organic EL layer 33. Examples of materials constituting the hole injection layer 1 include triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, phenylenediamine derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, and stilbene derivatives.

[0048] The hole transport layer 2 has a function of improving the efficiency of transporting holes from the first electrode 31 to the organic EL layer 33. Examples of materials constituting the hole transport layer 2 include porphyrin derivatives, aromatic tertiary amine compounds, styrylamine derivatives, polyvinylcarbazole, poly-p-phenylenevinylene, polysilane, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amine-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, hydrogenated amorphous silicon, hydrogenated amorphous silicon carbide, zinc sulfide, and zinc selenide.

[0049] The light-emitting layer 3 is a region into which holes and electrons are injected from the first electrode 31 and the second electrode 34, respectively, and where the holes and electrons recombine when a voltage is applied between the first electrode 31 and the second electrode 34. The light-emitting layer 3 is made of a material with high luminous efficiency. Examples of materials that can be used for the light-emitting layer 3 include metal oxinoid compounds (8-hydroxyquinoline metal complexes), naphthalene derivatives, anthracene derivatives, diphenylethylene derivatives, vinylacetone derivatives, triphenylamine derivatives, butadiene derivatives, coumarin derivatives, benzoxazole derivatives, oxadiazole derivatives, oxazole derivatives, benzimidazole derivatives, thiadiazole derivatives, benzthiazole derivatives, styryl derivatives, styrylamine derivatives, bisstyrylbenzene derivatives, trisstyrylbenzene derivatives, perylene derivatives, perinone derivatives, aminopyrene derivatives, pyridine derivatives, rhodamine derivatives, aquidin derivatives, phenoxazone, quinacridone derivatives, rubrene, poly-p-phenylenevinylene, and polysilane.

[0050] The electron transport layer 4 has a function of efficiently transferring electrons to the light-emitting layer 3. Examples of materials constituting the electron transport layer 4 include organic compounds such as oxadiazole derivatives, triazole derivatives, benzoquinone derivatives, naphthoquinone derivatives, anthraquinone derivatives, tetracyanoanthraquinodimethane derivatives, diphenoquinone derivatives, fluorenone derivatives, silole derivatives, and metal oxinoid compounds.

[0051] The electron injection layer 5 has a function of bringing the energy levels of the second electrode 34 and the organic EL layer 33 closer to each other and improving the efficiency of electron injection from the second electrode 34 to the organic EL layer 33, and this function can reduce the driving voltage of the organic EL element 35. The electron injection layer 5 is also called a cathode buffer layer. Here, examples of materials constituting the electron injection layer 5 include lithium fluoride (LiF), magnesium fluoride (MgF ２ ), calcium fluoride (CaF ２ ), strontium fluoride (SrF ２ ), barium fluoride (BaF ２ ), inorganic alkali compounds such as aluminum oxide (Al ２ O ３ ), strontium oxide (SrO), etc.

[0052] 3 , the second electrode 34 is provided to cover each organic EL layer 33 and the edge cover 32. The second electrode 34 has a function of injecting electrons into the organic EL layer 33. The second electrode 34 is preferably made of a material with a small work function to improve the efficiency of electron injection into the organic EL layer 33. Examples of materials that can be used for the second electrode 34 include silver (Ag), aluminum (Al), vanadium (V), cobalt (Co), nickel (Ni), tungsten (W), gold (Au), calcium (Ca), titanium (Ti), yttrium (Y), sodium (Na), ruthenium (Ru), manganese (Mn), indium (In), magnesium (Mg), lithium (Li), ytterbium (Yb), and lithium fluoride (LiF). The second electrode 34 may be made of, for example, magnesium (Mg) / copper (Cu), magnesium (Mg) / silver (Ag), sodium (Na) / potassium (K), or astatine (At) / astatine oxide (AtO ２ The second electrode 34 may be formed of an alloy such as lithium (Li) / aluminum (Al), lithium (Li) / calcium (Ca) / aluminum (Al), or lithium fluoride (LiF) / calcium (Ca) / aluminum (Al). The second electrode 34 may be formed of a conductive oxide such as tin oxide (SnO), zinc oxide (ZnO), indium tin oxide (ITO), or indium zinc oxide (IZO). The second electrode 34 may be formed by stacking multiple layers made of the above materials. Examples of materials with a low work function include magnesium (Mg), lithium (Li), lithium fluoride (LiF), magnesium (Mg) / copper (Cu), magnesium (Mg) / silver (Ag), sodium (Na) / potassium (K), lithium (Li) / aluminum (Al), lithium (Li) / calcium (Ca) / aluminum (Al), and lithium fluoride (LiF) / calcium (Ca) / aluminum (Al).

[0053] As shown in Fig. 3, a sealing film 45 (Thin Film Encapsulation, TFE film) is provided on the organic EL element layer 40 so as to cover each organic EL element 35. As shown in Fig. 3, the sealing film 45 includes a first inorganic sealing film 41 provided so as to cover the second electrode 34, an organic sealing film 42 provided on the first inorganic sealing film 41, and a second inorganic sealing film 43 provided so as to cover the organic sealing film 42, and has a function of protecting the organic EL layer 33 from moisture, oxygen, etc. The first inorganic sealing film 41 and the second inorganic sealing film 43 are made of, for example, silicon oxide (SiO ２ ) and aluminum oxide (Al ２ O ３ ), trisilicon tetranitride (Si ３ N ４ The organic sealing film 42 is made of an inorganic material such as silicon nitride (SiNx (x is a positive number)) or silicon carbonitride (SiCN). The organic sealing film 42 is made of an organic material such as acrylic resin, polyurea resin, parylene resin, polyimide resin, or polyamide resin.

[0054] In the organic EL display device 50a described above, in each subpixel P, a gate signal is input to the first TFT 9a via the gate line 14g, turning the first TFT 9a on, a predetermined voltage corresponding to the source signal is written to the gate electrode of the second TFT 9b and the capacitor 9d via the source line 18f, and when a light-emission control signal is input to the third TFT 9c via the light-emission control line 14e, the third TFT 9c is turned on, and a current corresponding to the gate voltage of the second TFT 9b is supplied from the power supply line 18g to the organic EL layer 33, causing the light-emitting layer 3 of the organic EL layer 33 to emit light, thereby displaying an image. Note that in the organic EL display device 50a, even if the first TFT 9a is turned off, the gate voltage of the second TFT 9b is held by the capacitor 9d, so that light emission by the light-emitting layer 3 is maintained in each subpixel P until a gate signal for the next frame is input.

[0055] Next, a method for manufacturing the organic EL display device 50a of this embodiment will be described. The method for manufacturing the organic EL display device 50a of this embodiment includes a TFT layer forming step, an organic EL element layer forming step, and a sealing film forming step.

[0056] <TFT Layer Formation Process> For example, on the surface of a resin substrate 10 formed on a glass substrate, a base coat film 11, a first TFT 9 a, a second TFT 9 b, a third TFT 9 c (their drain electrodes 18 d and the like (lower conductive layer)), a capacitor 9 d, a first inorganic insulating film 19, a first planarization film 20, a second inorganic insulating film 21, contact holes Ha (first contact hole H19, second contact hole H20, and third contact hole H21), an upper conductive layer (relay electrode 22 a and the like), a second planarization film 24, and the like are formed in this order using a well-known method, thereby forming a TFT layer 30 a.

[0057] In the manufacturing method of the organic EL display device 50a, when forming the contact holes Ha having the stacked contact hole structure, the third contact hole H21 is formed in a half-hanging structure with respect to the first contact hole H19 so that the opening O19 of the first contact hole H19 and the opening O21 of the third contact hole H21 partially overlap each other in a plan view. Note that the second contact hole H20 is formed so that the periphery of its opening O20 is positioned outside the periphery of the opening O19 of the first contact hole H19.

[0058] <Organic EL element layer forming process> In the display region D, a first electrode 31, an edge cover 32, an organic EL layer 33 (hole injection layer 1, hole transport layer 2, light-emitting layer 3, electron transport layer 4, electron injection layer 5), and a second electrode 34 are formed by using a well-known method on the second planarization film 24 of the TFT layer 30 a formed in the TFT layer forming process, thereby forming an organic EL element 35 and an organic EL element layer 40.

[0059] <Sealing Film Forming Process> First, an inorganic insulating film such as a silicon nitride film, a silicon oxide film, or a silicon oxynitride film is formed by plasma chemical vapor deposition (CVD) using a CMM as a deposition mask on the substrate surface on which the organic EL element layer 40 formed in the organic EL element layer forming process is formed, covering each organic EL element 35, to form a first inorganic sealing film 41. Subsequently, an organic resin material such as an acrylic resin is deposited on the first inorganic sealing film 41 by, for example, an inkjet method to form an organic sealing film 42. Thereafter, an inorganic insulating film such as a silicon nitride film, a silicon oxide film, or a silicon oxynitride film is formed by plasma CVD using the CMM as a deposition mask, covering the organic sealing film 42, to form a second inorganic sealing film 43. Through the above processes, a sealing film 45 is formed in which the first inorganic sealing film 41, the organic sealing film 42, and the second inorganic sealing film 43 are sequentially stacked.

[0060] Finally, a protective sheet (not shown) is attached to the surface of the substrate, and then laser light is irradiated from the glass substrate side of the resin substrate 10 to peel the glass substrate from the underside of the resin substrate 10, and a protective sheet (not shown) is attached to the underside of the resin substrate 10 from which the glass substrate has been peeled. In this manner, the organic EL display device 50a can be manufactured.

[0061] <Effects> As described above, the organic EL display device 50a of this embodiment can provide the following effects. (1) The organic EL display device 50a includes a TFT layer 30a having a lower conductive layer (such as the drain electrode 18d of the third TFT 9c), a first inorganic insulating film 19, a planarization film (such as the first planarization film 20), a second inorganic insulating film 21, an upper conductive layer (such as the relay electrode 22a), and a contact hole Ha for electrically connecting the lower conductive layer and the upper conductive layer. The contact hole Ha has a stacked contact hole structure in which three contact holes in different layers, namely a first contact hole H19, a second contact hole H20, and a third contact hole H21, are stacked and formed in the first inorganic insulating film 19, the planarization film, and the second inorganic insulating film 21, respectively. In the organic EL display device 50a, in the above-described stacked contact hole structure, the opening O19 of the first contact hole H19 on the lower layer and the opening O21 of the third contact hole H21 on the upper layer partially overlap each other in a plan view. By forming a half-overhanging structure between the third contact hole H21 and the first contact hole H19, the opening O21 of the third contact hole H21 is secured, and although the upper conductive layer is partially disconnected (such as the disconnected portion C22a of the relay electrode 22a), the current path CP from the lower conductive layer to the upper conductive layer is secured in other portions. (2) In the organic EL display device 50a, the above-described (1) reduces problems with conventional stacked contact hole structures, such as poor opening of the upper contact hole and disconnection of the upper conductive layer. (3) In the organic EL display device 50a, the above-described (1) and (2) improve the reliability of the display device.

[0062] Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG. 8 . FIG. 8 is an enlarged cross-sectional view showing the vicinity of a contact hole Ha formed in the TFT layer 30b of an organic EL display device 50b of this embodiment, and corresponds to FIG. 5 . Note that the lower layer of the second interlayer insulating film 17 and the upper layer of the second planarization film 24 are omitted from FIG. 8 . The overall configuration of the organic EL display device 50b is the same as that of the first embodiment described above, except for the configuration of the TFT layer 30b, and therefore a detailed description thereof will be omitted here. Furthermore, components similar to those of the first embodiment described above will be assigned the same reference numerals and their description will be omitted.

[0063] As shown in FIG. 8 , the TFT layer 30b constituting the organic EL display device 50b further includes a third inorganic insulating film 23 as an upper layer on the upper conductive layer (e.g., relay electrode 22a). The third inorganic insulating film 23 is provided so as to cover the contact hole Ha (the third contact hole H21 constituting it). Therefore, the relay electrode 22a formed on the inner wall surface of the contact hole Ha and the step C22a on the inner wall surface are covered with the third inorganic insulating film 23. This prevents moisture from penetrating and being transmitted to the first planarization film 20 exposed from the step C22a. In other words, the third inorganic insulating film 23 functions to protect the first planarization film 20 exposed from the step C22a from moisture and the like.

[0064] Due to the above-mentioned function, the third inorganic insulating film 23 may be provided in at least a region along the periphery of the contact hole Ha so as to cover the contact hole Ha, or may be provided over the entire display area D (on the second inorganic insulating film 21 and the upper conductive layer (relay electrode 22a, etc.)). Note that, as shown in FIG. 8, a second planarization film 24 is provided on the third inorganic insulating film 23.

[0065] The third inorganic insulating film 23 is made of, for example, silicon nitride (SiNx (x is a positive number)), silicon oxide (SiO ２ ), silicon oxynitride (SiON), or other inorganic insulating films, may be used as a single layer or multilayer film.

[0066] The organic EL display device 50b can be obtained by modifying the TFT layer formation process of the organic EL display device 50a described above as follows: In the TFT layer formation process, after forming the upper conductive layer (relay electrode 22a, etc.), and before forming the second planarization film 24, a third inorganic insulating film 23 is formed using a well-known method.

[0067] <Effects> In addition to the effects of the organic EL display device 50a described above, the organic EL display device 50b can achieve the following effects. (4) The organic EL display device 50b includes a TFT layer 30b that further includes a third inorganic insulating film 23 that is provided so as to cover the contact hole Ha (the third contact hole H21 that constitutes the contact hole Ha). In the organic EL display device 50b, the first planarization film 20 exposed from the discontinuity C22a on the inner wall surface of the contact hole Ha is covered with the third inorganic insulating film 23, thereby preventing moisture from penetrating and being transmitted to the first planarization film 20. As a result, the organic EL display device 50b can further improve the reliability of the display device.

[0068] Other Embodiments In each of the above embodiments, a TFT layer having a drain electrode formed of a third metal film as a lower conductive layer and a relay electrode formed of a fourth metal film as an upper conductive layer has been exemplified. However, the metal films forming the lower conductive layer and the upper conductive layer are not particularly limited to those described above, as long as the TFT layer has a laminated structure in which a lower conductive layer, a lower inorganic insulating film, a planarizing film, an upper inorganic insulating film, and an upper conductive layer are laminated in this order.

[0069] In each of the above embodiments, an organic EL layer having a five-layer stacked structure of a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, and an electron injection layer has been exemplified. However, the organic EL layer may have a three-layer stacked structure of, for example, a hole injection layer / hole transport layer, a light-emitting layer, and an electron transport layer / electron injection layer.

[0070] In addition, in each of the above embodiments, an organic EL display device in which the first electrode is an anode and the second electrode is a cathode is exemplified. However, the present invention can also be applied to an organic EL display device in which the stacked structure of the organic EL layer is reversed, and the first electrode is a cathode and the second electrode is an anode.

[0071] In each of the above embodiments, an organic EL display device is exemplified in which the electrode of the TFT connected to the first electrode is used as the drain electrode, but the present invention can also be applied to an organic EL display device in which the electrode of the TFT connected to the first electrode is called the source electrode.

[0072] In the above embodiments, an organic EL display device is used as the display device, but the present invention can also be applied to display devices such as an active matrix driving liquid crystal display device.

[0073] In the above embodiments, an organic EL display device has been described as an example of a display device, but the present invention is not limited to organic EL display devices and can be applied to any flexible display device. For example, the present invention can be applied to a flexible display device including a quantum-dot light emitting diode (QLED), which is a light emitting element using a quantum dot-containing layer.

[0074] As described above, the present invention is useful for flexible display devices.

[0075] C22a Step discontinuity D Display area F Frame area Ha Contact hole H19 First contact hole H20 Second contact hole H21 Third contact hole O19 Opening of first contact hole O20 Opening of second contact hole O21 Opening of third contact hole 9c Third TFT (thin film transistor) 10 Resin substrate (base substrate) 18d Drain electrode (lower conductive layer) 19 First inorganic insulating film 20 First planarization film (planarization film) 21 Second inorganic insulating film 22a Relay electrode (upper conductive layer) 23 Third inorganic insulating film 24 Second planarization film 30a, 30b TFT (thin film transistor) layer 40 Organic EL element layer (light emitting element layer) 35 Organic EL element (light emitting element) 45 Sealing film 50a, 50b Organic EL display device

Claims

1. A display device comprising a base substrate and a thin film transistor layer provided on the base substrate, wherein the thin film transistor layer has a lower conductive layer, a first inorganic insulating film, a planarizing film, a second inorganic insulating film, and an upper conductive layer, which are provided in this order, and a contact hole for electrically connecting the upper conductive layer to the lower conductive layer, wherein the contact hole is formed in a stacked contact hole structure in which a first contact hole formed in the first inorganic insulating film, a second contact hole formed in the planarizing film, and a third contact hole formed in the second inorganic insulating film are arranged in a stacked manner, and wherein the opening of the third contact hole and the opening of the first contact hole partially overlap each other in a planar view.

2. A display device according to claim 1, wherein the center of the opening of said third contact hole is located at a position different from the center of the opening of said first contact hole.

3. A display device according to claim 1 or 2, wherein a step portion formed by cutting the upper conductive layer is formed on at least a part of the inner wall surface of the contact hole.

4. A display device according to claim 3, characterized in that a current path electrically connecting the upper conductive layer to the lower conductive layer is formed on the inner wall surface of the contact hole on the side opposite to the step discontinuity.

5. A display device according to any one of claims 1 to 4, wherein the thin film transistor layer further comprises a third inorganic insulating film provided so as to cover the contact hole.

6. A display device according to claim 5, wherein a step portion formed by cutting the upper conductive layer is formed on at least a part of the inner wall surface of the contact hole, and the planarizing film exposed from the step portion is covered with the third inorganic insulating film.

7. A display device according to any one of claims 1 to 6, characterized in that the periphery of the opening of the second contact hole is located outside the periphery of the opening of the first contact hole.

8. A display device according to any one of claims 1 to 7, characterized in that the opening of the third contact hole and the opening of the second contact hole partially overlap each other in plan view.

9. A display device according to any one of claims 1 to 8, wherein the lower conductive layer is a source electrode or a drain electrode of a thin film transistor arranged in the thin film transistor layer in correspondence with a plurality of sub-pixels constituting the display area.

10. A display device according to any one of claims 1 to 9, further comprising a light emitting element layer provided on the thin film transistor layer, in which light emitting elements are arranged corresponding to a plurality of sub-pixels constituting the display area, the light emitting elements having a first electrode, and the upper conductive layer being electrically connected to the first electrode.

11. The display device according to claim 10, wherein the light-emitting element is an organic electroluminescence element.

12. A display device according to claim 10 or 11, characterized in that it comprises a sealing film provided so as to cover the light emitting element layer, and in which a first inorganic sealing film, an organic sealing film and a second inorganic sealing film are laminated in this order.

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