Display device

Abstract

A display device (90a) can be folded along a folding part (B) and has a sealing film (40) that includes: a display-sealing film (40d) that is a laminate of a first inorganic sealing film (41), an organic sealing film (42), and a second inorganic sealing film (43); and a frame-sealing film (40f) that is a laminate of the first inorganic sealing film (41) and the second inorganic sealing film (43). At at least the folding part (B), an organic step reduction film (SP) that reduces a step (Sb) that corresponds to the film thickness (t42) of the organic sealing film (42) or eliminates the step (Sb) is provided from the boundary (b) of a display region (D) and a frame region (F) to an end part of a display panel (70a) so as to cover the boundary (b).

Description

display device

[0001] This invention relates to a display device.

[0002] In recent years, self-emissive organic electroluminescent (EL) displays, which use organic electroluminescent (EL) elements, have attracted attention as an alternative to liquid crystal displays. Organic EL displays employ display panels with a structure (laminated) in which organic EL elements and various films are laminated on a flexible resin substrate.

[0003] The display panel (and its backplane substrate) is provided with a sealing structure consisting of a laminated film containing an inorganic film and an organic film to suppress the degradation of the organic EL element due to moisture ingress. This sealing structure covers the display area (active area) where the organic EL element is located. In this sealing structure, when the organic film is formed by an inkjet method, a wall (bank) is provided in the frame area (non-display area) surrounding the display area to block the ink that will become the organic film. Furthermore, functional films such as touch panels (on-cell touch panels) and polarizing plates are laminated on the display panel via an adhesive layer called OCA (optical clear adhesive).

[0004] In organic EL display devices equipped with the above-mentioned display panel, a foldable display, an organic EL display device that can be repeatedly folded, has been proposed. However, if a foldable display is left in a folded state or subjected to repeated bending, delamination or cracking may occur at the OCA interface between the films or inside the display panel (such as the sealing film or backplane substrate). As a result, foldable displays may suffer from defects in appearance or lighting malfunctions.

[0005] For example, Patent Document 1 proposes a display device having a structure in which a delta (reverse taper) shaped peeling prevention pattern is arranged on the bank in order to prevent peeling of the sealing film caused by compressive or tensile stress during bending.

[0006] U.S. Patent No. 11417860

[0007] Incidentally, peeling and cracking often occur at the edges of the display panel, specifically at the boundary between the display area and the frame area. These peeling and cracking start at the aforementioned boundary and spread in the planar direction of the display panel (from the edges inward, from the frame area to the display area), and also expand vertically.

[0008] However, Patent Document 1 describes only a structure for preventing the peeling of the sealing film, and is not a measure to prevent the peeling or cracking of the various functional films at the boundary. At the boundary, the various functional films peel off from the OCA, which causes the peeling or cracking of the sealing film.

[0009] The present invention has been made in view of the above, and its purpose is to suppress the occurrence of peeling, cracking, etc., at the edges of the display panel in a display device that can be repeatedly folded.

[0010] To achieve the above objective, the present invention provides a display device comprising a display area for displaying an image and a frame area surrounding the display area, and a display panel configured to be foldable around a folding portion provided to extend in one direction, wherein the display panel comprises a base substrate, a thin-film transistor layer provided on the base substrate, a light-emitting layer provided on the thin-film transistor layer and constituting the display area, and a sealing film, wherein the sealing film comprises a display sealing film provided in the display area and having a first inorganic sealing film, an organic sealing film, and a second inorganic sealing film laminated in order, and a frame sealing film provided in the frame area and having the first inorganic sealing film and the second inorganic sealing film constituting the display sealing film laminated in order, wherein at least in the folding portion, an organic step-reducing film is provided from the boundary to the edge of the display panel so as to cover the boundary between the display area and the frame area, reducing or eliminating the step according to the thickness of the organic sealing film.

[0011] According to the present invention, in a display device that can be repeatedly folded, the occurrence of peeling, cracks, and the like at the edges of the display panel can be suppressed.

[0012] Figure 1 is a plan view showing a schematic configuration of an organic EL display device according to the first embodiment of the present invention. Figure 2 is a plan view of the display area of ​​the organic EL display device according to the first embodiment of the present invention. Figure 3 is a cross-sectional view of the display area of ​​the organic EL display device according to the first embodiment of the present invention. Figure 4 is an equivalent circuit diagram of the TFT layer constituting the organic EL display device according to the first embodiment of the present invention. Figure 5 is a cross-sectional view of the organic EL layer constituting the organic EL display device according to the first embodiment of the present invention. Figure 6 is a cross-sectional view along the line VI-VI in Figure 1, showing the cross-sectional structure near the boundary between the display area and the frame area in the bent portion of the organic EL display device according to the first embodiment of the present invention. Figure 7 is a schematic plan view showing the base substrate of the display panel constituting the organic EL display device according to the first embodiment of the present invention. Figure 8 is a cross-sectional view along the line VIII-VIII in Figure 1, showing the cross-sectional structure near the panel-to-panel separation line of the base substrate of the display panel constituting the organic EL display device according to the first embodiment of the present invention. Figure 9 is a cross-sectional view showing the cross-sectional structure near the boundary between the display area and the frame area in the bent portion of the organic EL display device according to the first embodiment of the present invention, and corresponds to Figure 6. Figure 10 is a cross-sectional view showing the cross-sectional structure near the boundary between the display area and the frame area in the folded portion of an organic EL display device according to the second embodiment of the present invention, and corresponds to Figure 6. Figure 11 is a cross-sectional view showing a modified example of the organic EL display device according to the second embodiment of the present invention, and corresponds to Figure 6. Figure 12 is a cross-sectional view showing the cross-sectional structure near the boundary between the display area and the frame area in the folded portion of an organic EL display device according to the third embodiment of the present invention, and corresponds to Figure 6. Figure 13 is a cross-sectional view showing a modified example of the organic EL display device according to the third embodiment of the present invention, and corresponds to Figure 6. Figure 14 is a cross-sectional view showing the cross-sectional structure near the boundary between the display area and the frame area in the folded portion of an organic EL display device according to the fourth embodiment of the present invention, and corresponds to Figure 6.

[0013] Embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to the following embodiments.

[0014] 《First Embodiment》 Figures 1 to 9 show a first embodiment of the display device according to the present invention. In the following embodiments, an organic EL display device equipped with an organic EL element is exemplified as a display device equipped with a light-emitting element. Here, Figure 1 is a plan view showing the schematic configuration of the organic EL display device 90a of this embodiment. Figure 2 is a plan view of the display area D of the organic EL display device 90a. Figure 3 is a cross-sectional view of the display area D of the organic EL display device 90a. Figure 4 is an equivalent circuit diagram of the TFT layer 20 constituting the organic EL display device 90a. Figure 5 is a cross-sectional view of the organic EL layer 33 constituting the organic EL display device 90a. Figure 6 is a cross-sectional view along the line VI-VI in Figure 1, showing the cross-sectional structure near the boundary b between the display area D and the frame area F in the bent portion B of the organic EL display device 90a. This is a schematic plan view showing the base substrate M70a of the display panel 70a constituting the organic EL display device 90a. Figure 8 is a cross-sectional view along line VIII-VIII in Figure 1 of Figure 7, showing the cross-sectional structure near the panel-to-panel separation line C of the base substrate M70a of the display panel 70a constituting the organic EL display device 90a. Figure 9 is a cross-sectional view showing the cross-sectional structure near the boundary b between the display area D and the frame area F at the bent portion B of the organic EL display device 90a, and corresponds to Figure 6. Note that the upper layer of the sealing film 40 is omitted in Figure 3. The upper layer of the touch panel layer 50 is omitted in Figures 6 and 8.

[0015] As shown in Figure 1, the organic EL display device 90a includes a display panel 70a which defines, for example, a rectangular display area D for displaying images and a frame-shaped frame area (non-display area) F around the display area D. In this embodiment, a rectangular display area D is used as an example, but 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 part of the sides. In the organic EL display device 90a, a first direction X parallel to the substrate surface of the resin substrate 10, which will be described later, a second direction Y perpendicular to the first direction X and parallel to the substrate surface, and a third direction Z perpendicular to the first direction X and the second direction Y (see Figure 6, etc.) are defined.

[0016] In the display area D, as shown in Figure 2, multiple subpixels P are arranged in a matrix. In the display area D, as shown in Figure 2, for example, subpixels P having a red light-emitting region Lr for displaying red, subpixels P having a green light-emitting region Lg for displaying green, and subpixels P having a blue light-emitting region Lb for displaying blue are arranged adjacent to each other. In the display area D, for example, one pixel is composed of three adjacent subpixels P having a red light-emitting region Lr, a green light-emitting region Lg, and a blue light-emitting region Lb. The arrangement of the subpixels P is not particularly limited, and examples include pentile arrangements and stripe arrangements.

[0017] As shown in Figure 1, a terminal portion T is provided at one end of the frame region F (the upper end in Figure 1) so as to extend in one direction (first direction X, the horizontal direction in Figure 1).

[0018] The display panel 70a is configured to be foldable, for example, 180° (in a U-shape) around a bendable portion B that is provided approximately midway in one direction (the second direction Y in Figure 1, the vertical direction in Figure 1) and extends in a direction perpendicular to that direction (the first direction X in Figure 1, the horizontal direction in Figure 1). The display panel 70a is defined as having a bendable portion B that indicates a foldable area and two non-foldable portions N that indicate areas other than the bendable portion B. An organic EL display device 90a equipped with the display panel 70a can be called a foldable display.

[0019] As shown in Figure 3, the display panel 70a includes a resin substrate 10 provided as a base substrate, a thin film transistor (hereinafter also referred to as "TFT") layer 20 provided on the resin substrate 10, an organic EL element layer 30 provided as a light-emitting element layer constituting the display area D, and a sealing film 40 provided on the organic EL element layer 30. Hereinafter, the sealing film 40 provided in the display area D will be referred to as the "display sealing film 40d," and the sealing film 40 provided in the frame area F will be referred to as the "frame sealing film 40f."

[0020] The resin substrate 10 is made of, for example, polyimide resin.

[0021] As shown in Figure 3, the TFT layer 20 comprises a base coat film 11 provided on a resin substrate 10, a plurality of first TFTs 9a, a plurality of second TFTs 9b, and a plurality of capacitors 9c provided on the base coat film 11 for each subpixel P, and a planarization film 19 provided on each first TFT 9a, each second TFT 9b, and each capacitor 9c. In the TFT layer 20, as shown in Figure 3, a base coat film 11, semiconductor layers 12a and 12b, a gate insulating film 13, a first wiring layer including gate lines 14 (see Figure 2), gate electrodes 14a and 14b, and a lower conductive layer 14c, a first interlayer insulating film 15, a second wiring layer including an upper conductive layer 16, a second interlayer insulating film 17, a third wiring layer including source lines 18f (see Figure 2), source electrodes 18a and 18c, drain electrodes 18b and 18d, and power lines 18g, and a planarization film 19 are sequentially laminated on the resin substrate 10. Furthermore, as shown in Figures 2 and 4, the TFT layer 20 is provided with a plurality of gate lines 14 that extend parallel to each other in the horizontal direction in the figures. Furthermore, as shown in Figures 2 and 4, the TFT layer 20 is provided with a plurality of source lines 18f that extend parallel to each other in a direction that intersects (orthogonal to) the plurality of gate lines 14, i.e., in the vertical direction in the figures. Furthermore, in the TFT layer 20, as shown in Figures 2 and 4, a plurality of power lines 18g are provided so as to extend parallel to each other in the vertical direction in the figures. Each power line 18g is provided adjacent to each source line 18f, as shown in Figure 2. Also, in the TFT layer 20, as shown in Figure 4, a first TFT 9a, a second TFT 9b, and a capacitor 9c are provided in each subpixel P.

[0022] The base coat film 11, gate insulating film 13, first interlayer insulating film 15, and second interlayer insulating film 17 are, for example, silicon nitride (SiNx (where x is a positive number)), silicon oxide (SiO ２The semiconductor layers 12a and 12b are composed of, for example, a single layer or a multilayer film 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, second, and third wiring layers are composed of, for example, a single layer of metal such as molybdenum (Mo), titanium (Ti), aluminum (Al), copper (Cu), or tungsten (W), or a multilayer metal film such as Mo (upper layer) / Al (middle layer) / Mo (lower layer), Ti / Al / Ti, Al (upper layer) / Ti (lower layer), Cu / Mo, or Cu / Ti. It is preferable that the second and third wiring layers are formed of a multilayer metal film such as Ti / Al / Ti.

[0023] The first TFT 9a and the second TFT 9b are p-type TFTs in which the semiconductor layers 12a and 12b, described later, are doped with impurities such as boron.

[0024] As shown in Figure 4, the first TFT 9a is electrically connected to the corresponding gate line 14 and source line 18f at each sub-pixel P. Furthermore, as shown in Figure 3, the first TFT 9a comprises a semiconductor layer 12a, a gate insulating film 13, a gate electrode 14a, a first interlayer insulating film 15, a second interlayer insulating film 17, and a source electrode 18a and a drain electrode 18b, all arranged sequentially on the base coat film 11. Here, as shown in Figure 3, the semiconductor layer 12a is provided in an island-like manner on the base coat film 11 and has, for example, a channel region, a source region, and a drain region. The gate insulating film 13 is provided so as to cover the semiconductor layer 12a, as shown in Figure 3. The gate electrode 14a is provided on the gate insulating film 13 so as to overlap the channel region of the semiconductor layer 12a, as shown in Figure 3. The first interlayer insulating film 15 and the second interlayer insulating film 17 are provided sequentially so as to cover the gate electrode 14a, as shown in Figure 3. Furthermore, as shown in Figure 3, the source electrode 18a and the drain electrode 18b are provided spaced apart from each other on the second interlayer insulating film 17. Also, as shown in Figure 3, the source electrode 18a and the drain electrode 18b are electrically connected to the source region and drain region of the semiconductor layer 12a, respectively, through contact holes formed in the laminated film of the gate insulating film 13, the first interlayer insulating film 15, and the second interlayer insulating film 17.

[0025] As shown in Figure 4, the second TFT 9b is electrically connected to the corresponding first TFT 9a and power line 18g at each subpixel P. Furthermore, as shown in Figure 3, the second TFT 9b comprises a semiconductor layer 12b, a gate insulating film 13, a gate electrode 14b, a first interlayer insulating film 15, a second interlayer insulating film 17, and a source electrode 18c and a drain electrode 18d, all arranged sequentially on the base coat film 11. Here, the semiconductor layer 12b is provided in an island-like manner on the base coat film 11, as shown in Figure 3, and has, for example, a channel region, a source region, and a drain region. The gate insulating film 13 is provided so as to cover the semiconductor layer 12b, as shown in Figure 3. The gate electrode 14b is provided on the gate insulating film 13 so as to overlap the channel region of the semiconductor layer 12b, as shown in Figure 3. The first interlayer insulating film 15 and the second interlayer insulating film 17 are provided sequentially so as to cover the gate electrode 14b, as shown in Figure 3. Furthermore, as shown in Figure 3, the source electrode 18c and the drain electrode 18d are provided spaced apart from each other on the second interlayer insulating film 17. Also, as shown in Figure 3, the source electrode 18c and the drain electrode 18d are electrically connected to the source region and drain region of the semiconductor layer 12b, respectively, through contact holes formed in the laminated film of the gate insulating film 13, the first interlayer insulating film 15, and the second interlayer insulating film 17.

[0026] In this embodiment, top-gate type first TFT 9a and second TFT 9b are used as examples, but the first TFT 9a and second TFT 9b may be bottom-gate type TFTs.

[0027] As shown in Figure 4, the capacitor 9c is electrically connected to the corresponding first TFT 9a and power line 18g at each sub-pixel P. Here, as shown in Figure 3, the capacitor 9c comprises a lower conductive layer 14c formed in the same layer as the gate electrodes 14a and 14b using the same material, a first interlayer insulating film 15 provided to cover the lower conductive layer 14c, and an upper conductive layer 16 provided on the first interlayer insulating film 15 so as to overlap the lower conductive layer 14c. The upper conductive layer 16 is electrically connected to the power line 18g via a contact hole formed in the second interlayer insulating film 17, as shown in Figure 3.

[0028] The planarized film 19 has a flat surface in the display area D and is composed of, for example, an organic resin material such as polyimide resin or acrylic resin, or a polysiloxane-based SOG (spin-on-glass) material.

[0029] As shown in Figure 3, the organic EL element layer 30 comprises a plurality of organic EL elements 35, which are multiple light-emitting elements arranged in a matrix corresponding to a plurality of subpixels P.

[0030] As shown in Figure 3, the organic EL element 35 comprises a plurality of first electrodes 31 arranged sequentially on the planarization film 19, a plurality of organic EL layers 33 provided on each subpixel P on the first electrodes 31, and a second electrode 34 provided on the organic EL layer 33 in common to the plurality of subpixels P. The organic EL element 35 is covered with a display encapsulation film 40d.

[0031] As shown in Figure 3, the first electrode 31 is arranged in a matrix on the planarization film 19 to correspond to a plurality of subpixels P. Each first electrode 31 is electrically connected to the drain electrode 18d (or source electrode 18c) of each second TFT 9b via a contact hole formed in the planarization film 19. The first electrode 31 also has the function of injecting holes into the organic EL layer 33. Furthermore, it is more preferable to form the first electrode 31 from a material with a large work function in order to improve the hole injection efficiency into the organic EL layer 33. Here, examples of materials that constitute the first electrode 31 include metallic 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). Furthermore, examples of materials that constitute the first electrode 31 include astatine (At) / astatine oxide (AtO). ２It may also be an alloy such as ). Furthermore, the material constituting the first electrode 31 may be a conductive oxide such as tin oxide (SnO), zinc oxide (ZnO), indium tin oxide (ITO), or indium zinc oxide (IZO). The first electrode 31 may also be formed by stacking multiple layers made of the above material. Examples of compound materials with a large work function include indium tin oxide (ITO) and indium zinc oxide (IZO).

[0032] The peripheral edge of the first electrode 31 is covered by an edge cover 32 that is provided in a grid pattern in common to multiple subpixels P. Examples of materials that make up the edge cover 32 include positive-type photosensitive resin materials such as polyimide resin, acrylic resin, polysiloxane resin, and novolac resin, or polysiloxane-based SOG materials. A part of the surface of the edge cover 32 protrudes upward in the figure and is provided as an island-like pixel photospacer, as shown in Figure 3.

[0033] As shown in Figure 3, the organic EL layer 33 is arranged on each first electrode 31 and is provided in a matrix shape to correspond to a plurality of subpixels P. As shown in Figure 5, each organic EL layer 33 comprises 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 order on the first electrode 31.

[0034] The hole injection layer 1, also called the anode buffer layer, has the function of bringing the energy levels of the first electrode 31 and the organic EL layer 33 closer together, thereby improving the hole injection efficiency from the first electrode 31 to the organic EL layer 33. Examples of materials that constitute 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.

[0035] The hole transport layer 2 has the function of improving the efficiency of hole transport 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, zinc selenide, and the like.

[0036] The light-emitting layer 3 is a region in which holes and electrons are injected from the first electrode 31 and the second electrode 34, respectively, when a voltage is applied by the first electrode 31 and the second electrode 34, and where holes and electrons recombine. Here, the light-emitting layer 3 is formed of a material with high luminescence efficiency. Examples of materials constituting the light-emitting layer 3 include metal oxynoide compounds [8-hydroxyquinoline metal complex], 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, polysilane, and the like.

[0037] The electron transport layer 4 has a function of efficiently moving electrons to the light-emitting layer 3. Here, examples of the material constituting the electron transport layer 4 include, as organic compounds, oxadiazole derivatives, triazole derivatives, benzoquinone derivatives, naphthoquinone derivatives, anthraquinone derivatives, tetracyanoanthraquinodimethane derivatives, diphenoquinone derivatives, fluorenone derivatives, silole derivatives, metal oxynoid compounds, and the like.

[0038] 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 injecting electrons from the second electrode 34 into the organic EL layer 33. By this function, the driving voltage of the organic EL element 35 can be lowered. The electron injection layer 5 is also called a cathode buffer layer. Here, examples of the material constituting the electron injection layer 5 include, for example, inorganic alkali compounds such as lithium fluoride (LiF), magnesium fluoride (MgF ２ ), calcium fluoride (CaF ２ ), strontium fluoride (SrF ２ ), barium fluoride (BaF ２ ), aluminum oxide (Al ２ O ３ ), strontium oxide (SrO), and the like.

[0039] As shown in FIG. 3, the second electrode 34 is provided to cover each organic EL layer 33 and the edge cover 32. Further, the second electrode 34 has a function of injecting electrons into the organic EL layer 33. Also, the second electrode 34 is more preferably made of a material with a small work function in order to improve the electron injection efficiency into the organic EL layer 33. Here, examples of the material constituting 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), lithium fluoride (LiF), etc. Further, the second electrode 34 may be formed of an alloy such as magnesium (Mg) / copper (Cu), magnesium (Mg) / silver (Ag), sodium (Na) / potassium (K), astatine (At) / astatine oxide (AtO ２ ), lithium (Li) / aluminum (Al), lithium (Li) / calcium (Ca) / aluminum (Al), lithium fluoride (LiF) / calcium (Ca) / aluminum (Al), etc. Also, the second electrode 34 may be formed of a conductive oxide such as tin oxide (SnO), zinc oxide (ZnO), indium tin oxide (ITO), indium zinc oxide (IZO), etc. Further, the second electrode 34 may be formed by laminating a plurality of layers made of the above materials. Note that examples of the material with a small 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), lithium fluoride (LiF) / calcium (Ca) / aluminum (Al), etc.

[0040] It is shown that the display sealing film 40d is provided in the display area D as shown in FIGS. 3, 6, 8, and 9. The display sealing film 40d is a TFE (Thin Film Encapsulation) film having a function of protecting the organic EL layer 33 from moisture, oxygen, etc. Therefore, the display sealing film 40d is provided so as to cover the organic EL element layer 30 (each organic EL element 35 constituting the same) constituting the display area D. The display sealing film 40d includes a first inorganic sealing film 41 provided so as to cover the second electrode 34 or the planarization film 19, 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, which are sequentially laminated. As shown in FIGS. 6, 8, and 9, in the display area D, the first inorganic sealing film 41 is provided on the second interlayer insulating film 17 or the planarization film 19. The organic sealing film 42 is provided so as to reach the dam wall Wa formed of a laminated film in which the planarization film 19a and the bank 36a are sequentially laminated.

[0041] The first inorganic sealing film 41 and the second inorganic sealing film 43 are made of, for example, inorganic materials such as silicon oxide (SiO ２ ), aluminum oxide (Al ２ O ３ ), silicon nitride (SiNx (x is a positive number)) such as silicon nitride (Si ３ N ４ ), silicon carbonitride (SiCN). The organic sealing film 42 is made of, for example, organic materials such as acrylic resin, epoxy resin, silicone resin, polyurea resin, parylene resin, polyimide resin, and polyamide resin.

[0042] The frame sealing film 40f is provided in the frame region F, as shown in Figures 6, 8, and 9. The frame sealing film 40f is a TFE film that has the function of protecting against the intrusion of moisture, oxygen, etc. from the edges of the display panel 70a. Therefore, the frame sealing film 40f is provided up to the edges of the display panel 70a so as to cover the frame region F. The frame sealing film 40f is composed of a laminated film formed in the same layer using the same material as the first inorganic sealing film 41 and the second inorganic sealing film 43 that constitute the display sealing film 40d. In other words, the first inorganic sealing film 41 and the second inorganic sealing film 43 are provided in common to the display sealing film 40d and the frame sealing film 40f. On the other hand, the organic sealing film 42 is not provided in the frame sealing film 40f. That is, the frame sealing film 40f does not have an organic sealing film 42. The frame sealing film 40f is composed of an inorganic laminated film including the first inorganic sealing film 41 and the second inorganic sealing film 43. As shown in Figures 6, 8, and 9, the frame sealing film 40f is provided so as to reach the upper surface of the damming wall Wc, which is configured such that an island-shaped laminated film, in which the gate insulating film 13, the first interlayer insulating film 15, and the second interlayer insulating film 17 are sequentially stacked, is covered with a planarization film 19. In the frame region F, the first inorganic sealing film 41 is provided on the second interlayer insulating film 17 or the damming walls Wa to Wc.

[0043] In the organic EL display device 90a, as shown in Figures 6, 8, and 9, the film configuration of the sealing film 40 constituting the display panel 70a differs at the boundary b between the display area D and the frame area F. The organic sealing film 42 is provided in the display area D (its display sealing film 40d), while it is not provided in the frame area F (frame sealing film 40f).

[0044] Therefore, in conventional organic EL display devices (and the conventional display panels that constitute them), depending on the presence or absence of the organic encapsulation film 42, a step (approximately 5 μm to 10 μm) is created at the boundary b between the display area D and the frame area F (display encapsulation film 40d and frame encapsulation film 40f), corresponding to the thickness t42 of the organic encapsulation film 42 (see Figures 6, 8, and 9). Hereinafter, the step between the display encapsulation film 40d and the frame encapsulation film 40f in a conventional display panel will be referred to as the "step (Sb)". In conventional display panels, functional films such as touch panels (on-cell touch panels) and polarizing plates are laminated on the encapsulation film 40 having the step (Sb) via an OCA (adhesive layer). Therefore, when a conventional display panel is bent, stress is placed on the various functional films and OCA at the boundary b with the step (Sb) in the bent portion B, and there is a risk of delamination or cracking at the OCA interface. Once delamination or cracking occurs, repeated folding causes it to extend not only to the frame area F but also to the display area D. As a result, in conventional display panels, delamination or cracking occurs in the internal sealing film and backplane substrate, leading to display defects. Thus, in organic EL display devices (foldable displays) that can be repeatedly folded, the boundary area b of the display panel is considered to be a likely starting point for display defects due to the step (Sb).

[0045] In contrast, in the organic EL display device 90a, as shown in Figures 6, 8, and 9, an organic step reduction film SP is provided at the bent portion B so as to cover the boundary b between the display area D and the frame area F of the display panel 70a. The organic step reduction film SP is provided from the boundary b to the end of the display panel 70a. The organic step reduction film SP is an organic film that reduces (reduces) or eliminates the step (Sb) between the display sealing film 40d and the frame sealing film 40f, depending on the thickness t42 of the organic sealing film 42 that occurs depending on the presence or absence of the organic sealing film 42. In the display panel 70a, the step (Sb) has been reduced to the extent of the step Sf shown in Figures 6, 8, and 9. In other words, the organic step reduction film SP can be said to be an organic film that fills in the step (Sb) and flattens the boundary b. The organic step reduction film SP reduces the load on the various functional films and OCA at the boundary b in the bent portion B when the display panel 70a is bent. This suppresses the occurrence of peeling and cracking at the OCA interface between the various functional films. As a result, even with repeated bending of the display panel 70a, peeling and cracking of the sealing film 40 and backplane substrate inside the display panel 70a become less likely, and display defects are suppressed. In the folded portion B, the ratio of the step difference Sf at the edge of the display panel 70a (frame region F) to the step difference (Sb) (100%) at the boundary portion b of the display region D and the frame region F [step reduction rate, Sf / (Sb)] is preferably 50% or less, more preferably 30% or less, and most preferably 0% (no step difference Sf, flattened) from the viewpoint of reducing (reducing) the step difference (Sb) between the display sealing film 40d and the frame sealing film 40f, or eliminating the step difference (Sb).

[0046] In the folded portion B, the ratio of the film thickness tSPf of the organic step reduction film SP at the edge of the display panel 70a (frame region F) to the film thickness t42 (100%) of the organic sealing film 42 (tSPf / t42) is preferably 50% or more, more preferably 70% or more, and most preferably 100% (film thickness tSPf is about the same as or greater than t42), from the viewpoint of reducing (reducing) the step difference (Sb) between the display sealing film 40d and the frame sealing film 40f, or eliminating the step difference (Sb).

[0047] In the folded portion B, the ratio of the thickness tSPd of the organic step reduction film SP in the display area D to the thickness tSPf of the organic step reduction film SP in the frame area F (tSPd:tSPf) is, for example, about 1:10 to 3:10.

[0048] It is preferable that the organic step reduction film SP has the same hardness (Young's modulus, etc.) as the organic sealing film 42. Therefore, it is preferable that the organic step reduction film SP is formed from the same material as the organic sealing film 42.

[0049] As shown in Figure 6, the organic step reduction film SP is provided in the first direction X from the boundary b between the display area D and the frame area F to the end of the display panel 70a (end of the frame area F). In other words, the organic step reduction film SP overlaps with the boundary b in a plan view. The organic step reduction film SP only needs to be provided in the area of ​​the boundary b of the display panel 70a that overlaps with the folded portion B in a plan view, and may be provided over the entire area (edge) along the direction (second direction Y) intersecting the folded portion B.

[0050] Furthermore, as shown in Figures 7 and 8, the organic step reduction film SP may be provided so as to cover the area between adjacent boundary portions b of the base substrate M70a before it is divided into each display panel 70a in the first direction X. The organic step reduction film SP only needs to be provided in the area between adjacent boundary portions b of the base substrate M70a that overlaps with the bent portion B in a plan view, and may be provided over the entire area (edge) along the direction (second direction Y) intersecting the bent portion B. In this case, although a relatively thick organic step reduction film SP is also formed in the part that overlaps with the panel-to-panel division line C of the base substrate M70a in a plan view, cracks are less likely to occur when the base substrate M70a is divided because it is composed of an organic film. Therefore, when the base substrate M70a is divided along the panel-to-panel division line C, problems such as disconnection or shrinkage of the backplane substrate due to cracks in the organic step reduction film SP are less likely to occur.

[0051] Furthermore, the organic step reduction film SP not only has the advantage of reducing the step (Sb) to the extent of step Sf, or eliminating the step (Sb), but also has the advantage of bringing the film structure of the sealing film 40 closer to the boundary b between the display area D and the frame area F.

[0052] In conventional display panels with a step (Sb), when using relatively thin OCA (Optical Cover) with a thickness of, for example, 15 μm to 25 μm, due to the recent trend towards thinner panels, it is difficult to make this OCA conform to a step (Sb) of about 5 μm to 10 μm. As a result, there is a risk that air bubbles may form at the boundary b because the OCA is not properly adhered to the surface of the display panel. If the display panel is repeatedly bent in this bonded state, delamination or cracking is likely to occur at the OCA interface, resulting in display defects.

[0053] In contrast, in the organic EL display device 90a, as shown in Figure 9, the step height is reduced to Sf or less by the organic step height reduction film SP, and the boundary portion b is flattened. By flattening the boundary portion b, when a functional film 82, such as a polarizing plate, is provided on the surface of the display panel 70a (touch panel layer 50, which will be described later in Figure 9) via the OCA 81, the step height tracking ability at the boundary portion b of the OCA 81 and the functional film 82 is improved. Furthermore, because the bending edges of the OCA 81 and the functional film 82 are bent uniformly due to the flattening of the boundary portion b, peeling and cracking are less likely to occur at the OCA 81 interface.

[0054] In the organic EL display device 90a, as shown in Figures 6, 8, and 9, the organic step reduction film SP is formed in the same layer as the overcoat organic film 53 that constitutes the touch panel layer 50, using the same material. That is, the display panel 70a that constitutes the organic EL display device 90a has a touch panel layer 50 on its upper surface. The touch panel layer 50 can be described as an on-cell type touch panel (TP) placed on the display panel 70a.

[0055] The touch panel layer 50 is a laminated film in which a TP base coat film 51 is provided on the second inorganic encapsulation film 43 that constitutes the encapsulation film 40, a TP interlayer insulating film 52 is provided on the TP base coat film 51, and a TP overcoat organic film 53 is provided so as to cover the TP interlayer insulating film 52 are sequentially laminated. The TP base coat film 51 and the TP interlayer insulating film 52 are inorganic films made of the same inorganic material as the first inorganic encapsulation film 41 and the second inorganic encapsulation film 43. The TP overcoat organic film 53 is an organic film made of the same organic material as the organic encapsulation film 42. Various wirings (not shown) for the touch panel are provided between the TP base coat film 51 and the TP interlayer insulating film 52, and between the TP interlayer insulating film 52 and the TP overcoat organic film 53.

[0056] Thus, in the organic EL display device 90a, the TP overcoat organic film 53 that constitutes the touch panel layer 50 is left as an organic step reduction film SP at the boundary b (step (Sb) portion) between the display area D and the frame area F. As shown in Figures 6, 8, and 9, the TP overcoat organic film 53 may also be left to the edge of the display panel 70a including the boundary b.

[0057] The organic EL display device 90a described above is configured such that, at each subpixel P, a gate signal is input to the first TFT 9a via the gate line 14, thereby turning on the first TFT 9a, writing a data signal to the gate electrode 14b and capacitor 9c of the second TFT 9b via the source line 18f, and supplying a current from the power line 18g corresponding to the gate voltage of the second TFT 9b to the organic EL layer 33, causing the light-emitting layer 3 of the organic EL layer 33 to emit light and display an image. In addition, in the organic EL display device 90a, even if the first TFT 9a is turned off, the gate voltage of the second TFT 9b is maintained by the capacitor 9c, so the light emission from the light-emitting layer 3 is maintained until the gate signal for the next frame is input.

[0058] Next, a method for manufacturing the organic EL display device 90a of this embodiment will be described. The method for manufacturing the organic EL display device 90a of this embodiment comprises a TFT layer formation step, an organic EL element layer formation step, a encapsulation film formation step, a touch panel layer formation step, and a mounting step.

[0059] <TFT layer formation process> For example, a TFT layer 20 is formed on the surface of a resin substrate 10 formed on a glass substrate by forming a base coat film 11, a first TFT 9a, a second TFT 9b, a capacitor 9c, a planarization film 19, etc., using a well-known method.

[0060] <Organic EL Element Layer Formation Process> In the display area 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 on the planarized film 19 of the TFT layer 20 using a well-known method to form an organic EL element 35 and an organic EL element layer 30.

[0061] <Encapsulation Film Formation Process> First, on the substrate surface on which the organic EL element layer 30 is formed, an inorganic insulating film such as a silicon nitride film, silicon oxide film, or silicon oxynitride film is deposited using a plasma CVD (Chemical Vapor Deposition) method, covering each organic EL element 35, to form a first inorganic encapsulation film 41. Next, an organic resin material such as acrylic resin is deposited on the first inorganic encapsulation film 41, for example, by an inkjet method, to form an organic encapsulation film 42. At this time, the organic encapsulation film 42 is formed so as to reach the dam wall Wa located on the display area D side. After that, an inorganic insulating film such as a silicon nitride film, silicon oxide film, or silicon oxynitride film is deposited using a plasma CVD method, covering the first inorganic encapsulation film 41 or the organic encapsulation film 42, to form a second inorganic encapsulation film 43. Through the above process, a display sealing film 40d is formed in the display region D by sequentially stacking the first inorganic sealing film 41, the organic sealing film 42, and the second inorganic sealing film 43. Meanwhile, in the frame region F, a frame sealing film 40f is formed by sequentially stacking the first inorganic sealing film 41 and the second inorganic sealing film 43, excluding the organic sealing film 42.

[0062] <Touch Panel Layer Formation Process> On the substrate surface on which the second inorganic sealing film 43 constituting the display sealing film 40d and the frame sealing film 40f is formed, an inorganic insulating film such as a silicon nitride film, silicon oxide film, or silicon oxynitride film is deposited and patterned by plasma CVD to sequentially form a TP base coat film 51 and a TP interlayer insulating film 52. Subsequently, a TP overcoat organic film 53 is formed on the TP interlayer insulating film 52. For example, a photosensitive resin material such as acrylic resin is deposited over the entire display panel 70a (up to the edges of the display panel 70a) with a film thickness (equivalent to film thickness tSPd) corresponding to the film thickness t42 of the organic sealing film 42 [and the corresponding step (Sb) (approximately 5 μm to 10 μm)]. When patterning the deposited organic film, a gray tone mask or halftone mask is used to adjust the film thickness tSPd in ​​the display area D to be thinner (approximately 1 μm to 3 μm) than the film thickness tSPf at the edge (frame area F) of the display panel 70a. This leaves the TP overcoat organic film 53 as an organic step reduction film SP at the boundary b [step (Sb) portion]. Through the above steps, a touch panel layer 50 can be formed on the display panel 70a (and the sealing film 40 that constitutes it) in which a TP basecoat film 51, a TP interlayer insulating film 52, and a TP overcoat organic film 53 that functions as an organic step reduction film SP are sequentially laminated.

[0063] <Assembly Process> Finally, after attaching a protective sheet (not shown) to the surface of the substrate, the glass substrate is peeled off from the bottom surface of the resin substrate 10 by irradiating the resin substrate 10 with laser light from the glass substrate side, and a protective sheet (not shown) is attached to the bottom surface of the resin substrate 10 from which the glass substrate has been peeled off. In this way, the display panel 70a can be manufactured. If necessary, a functional film 82, such as a polarizing plate, is attached to the front and back surfaces of the display panel 70a via an OCA 81. In addition, a COF (Chip On Film), COG (Chip On Glass), etc. are mounted to the terminal portion T of the display panel 70a via an OCA. In this way, the organic EL display device 90a can be manufactured.

[0064] <Effects> As described above, the following effects can be obtained with the organic EL display device 90a of this embodiment. (1) The organic EL display device 90a is a foldable display that can be repeatedly folded and equipped with a display panel 70a configured to be foldable. At least in the folding portion B, the organic EL display device 90a is provided with an organic step reduction film SP that covers the boundary portion b of the display area D and the frame area F, from the boundary portion b to the edge of the display panel 70a, reducing the step (Sb) corresponding to the thickness t42 of the organic sealing film 42 to about a step Sf, or eliminating the step (Sb). Because the boundary portion b is flattened to a step Sf or less by the organic step reduction film SP, the film structure of the sealing film 40 at the boundary portion b becomes closer, and the load on the boundary portion b at the folding portion B when the display panel 70a is folded is reduced. As a result, at the boundary b, the occurrence of peeling and cracks at the OCA interface between the various functional films 82 provided on the display panel 70a via the OCA 81 is suppressed. Therefore, in the organic EL display device 90a, the occurrence of peeling and cracks at the edges of the display panel 70a can be suppressed. (2) In the organic EL display device 90a, as described in (1) above, the occurrence of peeling and cracks in the sealing film 40 and backplane substrate inside the display panel 70a can be suppressed even by repeated bending of the display panel 70a. (3) In the organic EL display device 90a, as described in (1) and (2) above, display defects caused by repeated bending are suppressed, thereby improving the reliability of the display device. (4) In the organic EL display device 90a, the organic step reduction film SP is formed in the same layer as the TP overcoat organic film 53 which constitutes the touch panel layer 50 provided on the display panel 70a, using the same material. In this configuration, when forming the touch panel layer 50, the TP overcoat organic film 53 is left up to the edge (frame region F) of the display panel 70a including the boundary b, and the film thickness tSPd of the display region D is adjusted to be thinner than the film thickness tSPf of the frame region F. Therefore, since there is no need to add steps or change the order of steps in order to form the organic step reduction film SP, the organic EL display device 90a can be easily manufactured.

[0065] 《Second Embodiment》 Next, a second embodiment of the present invention will be described using Figures 10 and 11. Figure 10 is a cross-sectional view showing the cross-sectional structure near the boundary b between the display area D and the frame area F in the folded portion B of the organic EL display device 90b of this embodiment, and corresponds to Figure 6. Figure 11 is a cross-sectional view showing a modified example 90b' of the organic EL display device 90b, and corresponds to Figure 6. Note that the upper layer of the color filter layer 60 is omitted in Figures 10 and 11. The overall configuration of the organic EL display device 90b and its modified example 90b' (hereinafter collectively referred to as "90b") is the same as in the first embodiment described above, except for the configuration of the upper layer of the sealing film 40, so a detailed explanation will be omitted here. Also, the same reference numerals are used for components that are the same as in the first embodiment described above, and their explanations will be omitted.

[0066] The display panel 70b constituting the organic EL display device 90b shown in Figure 10 and the modified example 90b' of the organic EL display device 90b shown in Figure 11 further have a color filter layer 60 provided on the touch panel layer 50. The color filter layer 60 can be described as an on-cell type color filter (CF) placed on the display panel 70a. By providing a color filter, in addition to improving the luminous efficiency of the organic EL element 35, the ambient light reflection performance is also improved, thus eliminating the need for a polarizing plate.

[0067] The color filter layer 60 is composed of a laminated film in which a color filter organic film 61 (see Figure 11) provided on the TP overcoat organic film 53 constituting the touch panel layer 50 and a CF overcoat organic film 62 (see Figures 10 and 11) provided to cover the color filter organic film 61 are sequentially laminated. The color filter organic film 61 can be any of the hue color filters, such as the red filter organic film 61r, the green filter organic film 61g, and the blue filter organic film 61b, or the black filter organic film 61br, which is called the black matrix. The color filter organic film 61 and the CF overcoat organic film 62 are composed of the same organic material as the organic sealing film 42.

[0068] Here, as shown in Figure 10, in the organic EL display device 90b, the organic step reduction film SP is formed in the same layer as the CF overcoat organic film 62 that constitutes the color filter layer 60, using the same material.

[0069] (Modified Version) As shown in modified version 90b' of the organic EL display device 90b in Figure 11, the organic step reduction film SP may be formed using a color filter organic film 61 and a CF overcoat organic film 62. That is, the organic step reduction film SP may be configured as a laminated film in which a first organic step reduction film SP1 formed in the same layer as the color filter organic film 61 using the same material, and a second organic step reduction film SP2 formed in the same layer as the CF overcoat organic film 62 using the same material, are sequentially laminated. In this case, the first organic step reduction film SP1 may consist of one single layer film of the red filter organic film 61r, green filter organic film 61g, blue filter organic film 61b, and black filter organic film 61br, or it may consist of a laminated film containing two or more of these.

[0070] Thus, in the organic EL display device 90b, as an organic step reduction film SP, the CF overcoat organic film 62 constituting the color filter layer 60 is left at the boundary portion b [step (Sb) portion] between the display area D and the frame area F, instead of the TP overcoat organic film 53 constituting the touch panel layer 50. If the CF overcoat organic film 62 alone is insufficient to flatten the boundary portion b, both the color filter organic film 61 and the CF overcoat organic film 62 are left. As shown in Figures 10 and 11, the CF overcoat organic film 62, and optionally the color filter organic film 61, may be left up to the edges of the display panels 70b and 70b' including the boundary portion b.

[0071] The panel configuration of the organic EL display device 90b is not particularly limited to display panels 70b and 70b' in which a color filter layer 60 is formed on a touch panel layer 50. If a touch panel is not required, the display panels 70b and 70b' do not need to have a touch panel layer 50. In this configuration, the color filter layer 60 is provided directly above the display panels 70b and 70b'. Specifically, the color filter organic film 61 constituting the color filter layer 60 is provided on a second inorganic sealing film 43 constituting the sealing film 40.

[0072] The organic EL display device 90b can be manufactured by further performing a color filter layer formation step after the touch panel layer formation step in the manufacturing method of the organic EL display device 90a described above.

[0073] <Color Filter Layer Formation Process> A color filter organic film 61 and a CF overcoat organic film 62 are formed sequentially on the substrate surface on which the TP overcoat organic film 53 constituting the touch panel layer 50 is formed, or on the substrate surface on which the second inorganic encapsulation film 43 constituting the encapsulation film 40 is formed. For example, a color filter organic film 61 is formed by depositing a photosensitive resin material such as acrylic resin having each hue and then patterning it. Subsequently, a photosensitive resin material such as acrylic resin is deposited on the color filter organic film 61 to a film thickness (equivalent to film thickness tSPd) corresponding to the film thickness t42 of the organic encapsulation film 42 [with a corresponding step difference (Sb) (approximately 5 μm to 10 μm)] over the entire display panel 70b (up to the edges of the display panel 70b). When patterning the deposited organic film, a gray tone mask or halftone mask is used to adjust the film thickness tSPd in ​​the display area D to be thinner (approximately 1 μm to 3 μm) than the film thickness tSPf at the edge (frame area F) of the display panel 70a. This leaves a CF overcoat organic film 62 as an organic step reduction film SP at the boundary b [step (Sb) portion]. Thus, an organic EL display device 90b can be manufactured, which has a display panel 70b having a color filter layer 60 in which a color filter organic film 61 and a CF overcoat organic film 62 functioning as an organic step reduction film SP are sequentially laminated.

[0074] In the modified form 90b' of the organic EL display device 90b, when forming the color filter organic film 61, one or all of the red filter organic film 61r, green filter organic film 61g, blue filter organic film 61b, and black filter organic film 61br may be formed in the same manner as the CF overcoat organic film 62. At this time, the film thickness of each of the color filter organic film 61 and the CF overcoat organic film 62 may be adjusted as appropriate. As a result, an organic EL display device 90b' equipped with a display panel 70b' having a color filter layer 60 that functions as an organic step reduction film SP can be manufactured.

[0075] <Effects> According to the organic EL display device 90b and its modified example 90b' described above, the same effects as (1) to (4) above can be obtained. (4) In the organic EL display device 90b, the organic step reduction film SP is formed in the same layer as the CF overcoat organic film 62 which constitutes the color filter layer 60 provided on the display panel 70b, using the same material. In the organic EL display device 90a', the organic step reduction film SP is formed in a laminated film of a first organic step reduction film SP1 which is formed in the same layer as the color filter organic film 61 which constitutes the color filter layer 60, using the same material, and a first organic step reduction film SP2 which is formed in the same layer as the CF overcoat organic film 62, using the same material. In these configurations, when forming the color filter layer 60, the CF overcoat organic film 62 is left up to the edge (frame region F) of the display panel 70a including the boundary b, and the color filter organic film 61 is left as needed, and the film thickness in the display region D is adjusted to be thinner than in the frame region F. Therefore, since there is no need to add steps or change the order of steps in order to form the organic step reduction film SP, the organic EL display device 90b and its modified example 90b' can be easily manufactured.

[0076] <Third Embodiment> Next, a third embodiment of the present invention will be described using Figures 12 and 13. Figure 12 is a cross-sectional view showing the cross-sectional structure near the boundary b between the display area D and the frame area F in the folded portion B of the organic EL display device 90c of this embodiment, and corresponds to Figure 6. Figure 13 is a cross-sectional view showing a modified example 90c' of the organic EL display device 90c, and corresponds to Figure 6. Note that the upper layer of the color filter layer 60 is omitted in Figures 12 and 13. The overall configuration of the organic EL display device 90c and its modified example 90c' (hereinafter collectively referred to as "90c") is the same as in the first embodiment described above, except for the configuration of the upper layer of the sealing film 40, so a detailed explanation will be omitted here. Also, the same reference numerals are used for components similar to those in the first embodiment described above, and their explanations will be omitted.

[0077] The display panel 70c constituting the organic EL display device 90c has a touch panel layer 50 and a color filter layer 60 provided on the touch panel layer 50 on its upper surface.

[0078] In the organic EL display device 90c, the organic step reduction film SP is composed of a TP overcoat organic film 53 that constitutes the touch panel layer 50 and a CF overcoat organic film 62 that constitutes the color filter layer 60. Specifically, the organic step reduction film SP is formed as a laminated film in which a first organic step reduction film SP1, formed in the same layer using the same material as the TP overcoat organic film 53, and a second organic step reduction film SP2, formed in the same layer using the same material as the CF overcoat organic film 62, are sequentially stacked.

[0079] (Modified Version) As shown in modified version 90c' of the organic EL display device 90c in Figure 13, an organic step reduction film SP may be formed using a color filter organic film 61 that constitutes the color filter layer 60, in addition to the TP overcoat organic film 53 and the CF overcoat organic film 62. That is, the organic step reduction film SP may be formed as a laminated film in which a first organic step reduction film SP1 formed in the same layer as the TP overcoat organic film 53 using the same material, a second organic step reduction film SP2 formed in the same layer as the color filter organic film 61 using the same material, and a third organic step reduction film SP3 formed in the same layer as the CF overcoat organic film 62 using the same material are sequentially laminated. In this case, the second organic step reduction film SP2 may consist of one single layer film of any of the red filter organic film 61r, green filter organic film 61g, blue filter organic film 61b, and black filter organic film 61br, or it may consist of a laminated film containing two or more of these.

[0080] Thus, in the organic EL display device 90c, both the TP overcoat organic film 53 (first organic step reduction film SP1) and the CF overcoat organic film 62 (second organic step reduction film SP2) are left at the boundary b (step (Sb) portion) between the display area D and the frame area F as organic step reduction films SP. If the flattening of the boundary b is insufficient with only the TP overcoat organic film 53 and the CF overcoat organic film 62, then three films are left: the TP overcoat organic film 53 (first organic step reduction film SP1), the color filter organic film 61 (second organic step reduction film SP2), and the CF overcoat organic film 62 (third organic step reduction film SP3). As shown in Figures 12 and 13, the TP overcoat organic film 53 and the CF overcoat organic film 62, and optionally the color filter organic film 61, may be left up to the edges of the display panels 70c, 70c' including the boundary b.

[0081] The organic EL display device 90c can be manufactured by combining the manufacturing methods of the organic EL display devices 90a and 90b described above. In this case, the film thickness of the TP overcoat organic film 53, the CF overcoat organic film 62, and, if necessary, the color filter organic film 61 can be appropriately adjusted.

[0082] <Effects> The organic EL display device 90c described above can be used to obtain the same effects as described in (1) to (4) above. Specifically, since the organic step reduction film SP is formed by including both the TP overcoat organic film 53 and the CF overcoat organic film 62, and optionally the color filter organic film 61, the step (Sb) is eliminated (the step Sf is eliminated), and the boundary portion b can be made even flatter.

[0083] 《Fourth Embodiment》 Next, a fourth embodiment of the present invention will be described with reference to Figure 14. Figure 14 is a cross-sectional view showing the cross-sectional structure near the boundary b between the display area D and the frame area F in the folded portion B of the organic EL display device 90d of this embodiment, and corresponds to Figure 6. Note that the upper layer of the sealing film 40 is omitted in Figure 14. The overall configuration of the organic EL display device 90d is the same as in the first embodiment described above, except for the configuration of the upper layer of the sealing film 40, so a detailed explanation will be omitted here. Also, the same reference numerals are used for components that are the same as in the first embodiment described above, and their explanations will be omitted.

[0084] As shown in Figure 14, the organic EL display device 90d includes a coating film 55 as an organic step reduction film SP that fills the step (Sb). In the organic EL display device 90d, planarization is performed by post-coating with resin, rather than by patterning, as in the organic EL display devices 90a to 90c described above. The coating film 55 is composed of the same organic material as the organic encapsulation film 42. The coating film 55 may be a single layer film or a laminated film.

[0085] The display panel 70d constituting the organic EL display device 90d may or may not have at least one or both of the touch panel layer 50 and the color filter layer 60.

[0086] Thus, in the organic EL display device 90d, a resin is applied as an organic step reduction film SP to the boundary portion b (step (Sb) portion) between the display area D and the frame area F. As shown in Figure 14, the applied film 55 may be formed up to the edge of the display panel 70d, including the boundary portion b.

[0087] The organic EL display device 90d can be manufactured by further performing a coating film formation step in the manufacturing method of the organic EL display devices 90a, 90b, and 90c described above. The coating film formation step is performed between the time the base substrate (M70a shown in Figures 7 and 8) is divided and the time the various functional films are attached to the display panel 70d. The coating film formation step may be performed as a separate step or within the mounting step described above. For example, in the mounting step, when applying the protective resin after mounting the COF or COG, the resin may be additionally applied to the boundary portion b [step portion (Sb)] to form a coating film 55. In this case, the additional coating film formation step becomes unnecessary.

[0088] <Coating Film Formation Process> A coating film 55 is formed on the substrate surface on which the TP overcoat organic film 53 constituting the touch panel layer 50 is formed, on the substrate surface on which the CF overcoat organic film 62 constituting the color filter layer 60 is formed, or on the substrate surface on which the sealing film 40 is formed without the touch panel layer 50 or the color filter layer 60, by applying a UV-curing resin material such as epoxy resin to at least the portion of the boundary portion b of the display panel 70a that overlaps with the folded portion B in a plan view, for example, by an inkjet method or a dispenser. At this time, the thickness of the coating film 55 may be adjusted as appropriate. By doing so, an organic EL display device 90d equipped with a display panel 70d having a coating film 55 that functions as an organic step reduction film SP can be manufactured.

[0089] <Effects> The organic EL display device 90d described above can be used to obtain the same effects as described in (1) to (4) above.

[0090] 《Other Embodiments》 In each of the above embodiments, the inorganic multilayer film is composed of four layers, in which a gate insulating film, a first interlayer insulating film, and a second interlayer insulating film are stacked in that order on a base coat film. However, it may also be composed of one layer of base coat film, or of two layers, a base coat film and a gate insulating film.

[0091] In the embodiments described above, an organic EL layer with a five-layer stacked structure consisting of a hole injection layer, a hole transport layer, an emissive layer, an electron transport layer, and an electron injection layer was exemplified. However, the organic EL layer may also have a three-layer stacked structure consisting of, for example, a hole injection layer / hole transport layer, an emissive layer, and an electron transport layer / electron injection layer.

[0092] Furthermore, while the above embodiments illustrate organic EL display devices in which the first electrode is the anode and the second electrode is the cathode, the present invention can also be applied to organic EL display devices in which the laminated structure of the organic EL layer is reversed, with the first electrode being the cathode and the second electrode being the anode.

[0093] In the embodiments described above, an organic EL display device was shown in which the electrode of the TFT connected to the first electrode is used as the drain electrode. However, 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.

[0094] In the embodiments described above, an organic EL display device was used as the display device, but the present invention can also be applied to display devices such as active matrix driven liquid crystal displays.

[0095] In the embodiments described above, an organic EL display device was used as an example of a display device. However, the present invention is not limited to organic EL display devices and can be applied to any flexible display device. For example, it can be applied to a flexible display device equipped with a QLED (Quantum-dot light-emitting diode), which is a light-emitting element using a quantum dot-containing layer.

[0096] As described above, the present invention is useful for flexible display devices.

[0097] b Boundary between display encapsulation film and frame encapsulation film C Panel-to-panel separation line B Folded portion D Display area F Frame area M17a Base substrate N Non-folded portion P Subpixel (Sb) Step difference between display encapsulation film and frame encapsulation film Sf Step difference at the edge of the display panel (frame area) SP Organic step reduction film SP1 First organic step reduction film SP2 Second organic step reduction film SP3 Third organic step reduction film t42 Film thickness of organic encapsulation film tSPd Film thickness of organic step reduction film in the display area tSPf Film thickness of organic step reduction film in the frame area T Terminal portion Wa-Wc Damping wall 10 Resin substrate (base substrate) 19, 19a-19c Planarization film 20 TFT (thin film transistor) layer 30 Organic EL element layer (light-emitting element layer) 35 Organic EL element (light-emitting element) 36a-36b Bank 40d (40) Display encapsulation film 40f (40) Frame encapsulation film 41 First inorganic encapsulation film 42 Organic encapsulation film 43 Second inorganic encapsulation film 50 Touch panel layer 51 Base coat film 52 Interlayer insulating film 53 Overcoat organic film, first overcoat organic film 55 Coating film 60 Color filter layer 61 Color filter organic film 61b Blue filter organic film 61br Black filter organic film 61g Green filter organic film 61r Red filter organic film 62 Overcoat organic film, second overcoat organic film 70a-70d Display panel 81 OCA 82 Functional film 90a-90d Organic EL display device

Claims

1. A display device comprising a display panel having a display area for displaying an image and a frame area around the display area, and configured to be foldable around a folding portion provided to extend in one direction, wherein the display panel comprises a base substrate, a thin film transistor layer provided on the base substrate, a light-emitting layer provided on the thin film transistor layer and constituting the display area, and a sealing film provided to cover the light-emitting layer, wherein the sealing film comprises a display sealing film provided in the display area and having a first inorganic sealing film, an organic sealing film, and a second inorganic sealing film laminated in order, and a frame sealing film provided in the frame area and having the first inorganic sealing film and the second inorganic sealing film constituting the display sealing film laminated in order, wherein at least in the folding portion, an organic step-reducing film is provided from the boundary to the end of the display panel so as to cover the boundary between the display area and the frame area, reducing or eliminating the step according to the thickness of the organic sealing film.

2. A display device according to claim 1, wherein the display panel is provided on the sealing film and has a touch panel layer in which a base coat film, an interlayer insulating film, and an overcoat organic film are sequentially laminated, and the organic step reduction film is formed in the same layer as the overcoat organic film using the same material.

3. A display device according to claim 1, wherein the display panel is provided on the sealing film and has a color filter layer in which a color filter organic film and an overcoat organic film are sequentially laminated, and the organic step reduction film is formed in the same layer as at least one of the color filter organic film and the overcoat organic film using the same material.

4. A display device according to claim 3, characterized in that the organic step reduction film is formed by a laminated film in which a first organic step reduction film formed in the same layer as the color filter organic film using the same material and a second organic step reduction film formed in the same layer as the overcoat organic film are sequentially laminated.

5. A display device according to claim 1, wherein the display panel comprises a touch panel layer provided on the sealing film, in which a base coat film, an interlayer insulating film, and a first overcoat organic film are sequentially laminated; a color filter layer provided on the touch panel layer, in which a color filter organic film and a second overcoat organic film are sequentially laminated; and the organic step reduction film is formed by a laminated film in which a first organic step reduction film formed in the same layer using the same material as the first overcoat organic film and a second organic step reduction film formed in the same layer using the same material as the second overcoat organic film are sequentially laminated.

6. A display device according to claim 5, characterized in that the organic step reduction film is formed by a laminated film in which a first organic step reduction film formed in the same layer as the first overcoat organic film using the same material, a second organic step reduction film formed in the same layer as the color filter organic film using the same material, and a third organic step reduction film formed in the same layer as the second overcoat organic film are sequentially laminated.

7. A display device according to claim 1, characterized in that the organic step reduction film is formed by a coating film coated with an organic material.

8. A display device according to any one of claims 1 to 7, characterized in that the organic step reduction film has the same hardness as the organic sealing film.

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