DISPLAY DEVICE

A flexible display panel including a display region including a pair of flat portions held in a flat manner and a bendable portion disposed between the pair of flat portions and held in a bendable manner and a frame region provided in a periphery of the display region, a support substrate supporting the display panel in a flat manner, and a housing supporting the support substrate are provided, and in the display region, the display panel and the support substrate are not fixed to each other and a gap is formed between the support substrate and the housing.

TECHNICAL FIELD

The disclosure relates to a display device.

BACKGROUND ART

In recent years, self-luminous organic electroluminescence (hereinafter also referred to as EL) display devices using organic EL elements have attracted attention as display devices that can replace liquid crystal display devices. As the organic EL display device, a display panel having a structure (a layered body) in which an organic EL element, a variety of films, and the like are layered on a flexible resin substrate has been adopted, and an organic EL display device which can be repeatedly folded, a so-called foldable display has been proposed.

In the foldable display, since it is necessary to maintain flexibility, a rigid member such as an inflexible (rigid) cover cannot be provided on a surface. Thus, the flexible display panel may be locally deformed by a drop impact or the like when an object is dropped on the surface of the flexible display panel or when the foldable display itself is dropped. When a crack or the like occurs in an inorganic film of a thin film transistor (hereinafter, also referred to as “TFT”) layer constituting the display panel due to the local deformation of the display panel, a bright spot, a black spot (a point defect) or the like occurs in the foldable display to cause a display defect. As described above, the foldable display has a problem of low impact resistance against dropping.

With respect to the above problem, a variety of methods for reducing the possibility of occurrence of the display defect have been studied. For example, PTL 1 discloses a foldable display including an impact absorption layer provided between a flexible display layer (a first display region, a second display region, and a third display region) and an inflexible first support substrate supporting the first display region and between the flexible display layer and an inflexible second support substrate supporting the second display region. The impact absorption layer includes a metal film for improving the impact resistance of the foldable display.

CITATION LIST

Patent Literature

SUMMARY

Technical Problem

In the foldable display described in PTL 1, the metal film constituting the impact absorption layer is adhered to the entirety of a display region as a part (one layer) of the layered body constituting the flexible display layer (the display panel). Thus, for example, in a case where a large point impact such as pen drop in which a pen tip having a small ball diameter is dropped on the display panel is received, the metal film may not be sufficiently bent and the point impact may not be sufficiently alleviated.

In addition, in the foldable display described in PTL 1, although a first and a second support substrates supporting the first and the second display regions (non-bendable region, range X illustrated inFIG.1), respectively, are provided, a support substrate is not present on the lower side of the third display region (bendable region, range Y illustrated inFIG.1) located between the first display region and the second display region. Thus, when the large point impact such as the pen drop is applied to the bendable region, the display panel may be locally deformed in the vicinity of the bendable region. In addition, even in a case where a relatively thick adhesive layer is present between the first display region and the first support substrate and between the second display region and second support substrate, when the large point impact is applied to the non-bendable region, the adhesive layer having flexibility is locally deformed, and thus the display panel may be locally deformed also in the non-bendable region.

Furthermore, in the foldable display described in PTL 1, since the panel configuration is largely different between the non-bendable region and the bendable region, there is a concern about problems such as undulation of the display panel and folding habit at the time of bending in the bendable region. When these problems are attempted to be solved, the flexibility of the display panel may not be maintained.

The disclosure has been made in view of the above, and an object of the disclosure is to achieve both the impact resistance against the large point impact and the flexibility of the display panel.

Solution to Problem

In order to achieve the above object, a display device according to the disclosure includes a flexible display panel including a display region including a pair of flat portions held in a flat manner and a bendable portion disposed between the pair of flat portions and held in a bendable manner and a frame region provided in a periphery of the display region, a support substrate supporting the display panel in a flat manner, and a housing supporting the support substrate, in which in the display region, the display panel and the support substrate are not fixed to each other and a gap is formed between the support substrate and the housing.

Advantageous Effects of Disclosure

According to the disclosure, both impact resistance against a large point impact and flexibility of a display panel can be achieved.

DESCRIPTION OF EMBODIMENTS

Embodiments of a technique according to the disclosure will be described below in detail with reference to the drawings. Note that the technique according to the disclosure is not limited to the embodiments to be described below.

First Embodiment

FIG.1toFIG.13illustrate a first embodiment of a display device and a method for manufacturing the display device according to the disclosure. Note that, in each of the following embodiments, an organic EL display device including an organic EL element will be exemplified as a display device including a light-emitting element.FIG.1is a perspective view illustrating a deployed state of an organic EL display device70aaccording to the present embodiment.FIG.2is a plan view illustrating the deployed state of the organic EL display device70a.FIG.3is a cross-sectional view, taken along a line III-III inFIG.2, illustrating a deployed state of the organic EL display device70a.FIG.4is a plan view illustrating the deployed state of a first modification example of the organic EL display device70a, and is a view corresponding toFIG.2.FIG.5is an enlarged cross-sectional view, taken along a line V-V inFIG.4, illustrating a folded state in which the first modification example of the organic EL display device70ais folded in a U-shape.FIG.6is a plan view illustrating a deployed state of a second modification example of the organic EL display device70a, and is a view corresponding toFIG.2.FIG.7is an enlarged cross-sectional view, taken along a line VII-VII inFIG.6, illustrating a folded state in which the second modification example of the organic EL display device70ais folded in a U-shape, and is a view corresponding toFIG.5.FIG.8is a plan view illustrating a deployed state of a third modification example of the organic EL display device70a, and is a view corresponding toFIG.2.FIG.9is an enlarged cross-sectional view, taken along a line IX-IX inFIG.8, illustrating a folded state in which the third modification example of the organic EL display device70ais folded in the U-shape, and is a view corresponding toFIG.5.FIG.10is a plan view of a display region D of the organic EL display device70a.FIG.11is a cross-sectional view of the display region D of the organic EL display device70a.FIG.12is an equivalent circuit diagram of a TFT layer20constituting the organic EL display device70a.FIG.13is a cross-sectional view of an organic EL layer23constituting the organic EL display device70a. Note that, in the organic EL display device70a, a direction X parallel to a substrate surface of an organic EL display panel40described below, a direction Y perpendicular to the direction X and parallel to the substrate surface of the organic EL display panel40, and a direction Z perpendicular to the direction X and the direction Y are defined.

As illustrated inFIG.1toFIG.3, the organic EL display device70aincludes at least an organic EL display panel40, a support substrate50, and a housing60.

As illustrated inFIG.1andFIG.2, the organic EL display panel40includes, for example, the display region (active area) D provided in a rectangular shape and configured to display an image, and a frame region (non-display region) N provided in a frame-like shape in a periphery of the display region D. Note that, in the present embodiment, the display region D having the rectangular shape is exemplified, but the rectangular shape includes a substantial rectangular shape such as a shape whose sides are arc-shaped, a shape whose corners are arc-shaped, and a shape in which a part of a side has a notch. Note that one end of the frame region N in the X direction inFIG.1toFIG.3is provided with a terminal portion (not illustrated) in which a plurality of terminals are arrayed.

As illustrated inFIG.1toFIG.3, the display region D includes a pair of flat portions (a part of a non-bendable region RFdescribed later) Fa and Fb held in a flat manner (flat surface) and a bendable portion (a part of a bendable region RBdescribed later) B disposed between the pair of flat portions Fa and Fb and held in a bendable manner. As illustrated inFIG.1andFIG.2, in the bendable portion B (bendable region RB), a bending axis (bending center) C that is bendable to 180° (U-shape) is possible so that the pair of flat portions Fa and Fb face each other is provided to extend in the direction Y. Note that, in the side view, a bent shape of the organic EL display panel40is not limited to the U-shape (seeFIG.5,FIG.7,FIG.9, andFIG.17), and may be, for example, a droplet shape (seeFIG.18).

As illustrated inFIG.1andFIG.2, the organic EL display panel40includes the bendable region RBalong the bending axis C and a pair of the non-bendable regions RFand RFlocated at both ends of the bendable region RBin the direction X. As illustrated inFIG.1andFIG.2, the bendable region RBis a region linearly extending along the bending axis C (direction Y) and including the bendable portion B (a part of the display region D) and both end portions (a part of the frame region N) in the direction Y of the bendable portion B. The non-bendable region RFis a region other than the bendable region RB, and is a rectangular region in a plan view including the pair of flat portions Fa and Fb (parts of the display region D) and each peripheral portion (a part of the frame region N) of a respective one of the pair of flat portions Fa and Fb.

The size of the organic EL display panel40is, for example, about 10 cm in width (vertical direction inFIG.2, length in the direction Y), about 18 cm in length (horizontal direction inFIG.1toFIG.3, length in the direction X), and about several hundred μm in thickness (vertical direction inFIG.1andFIG.3, length in the direction Z). A specific configuration of the organic EL display panel40will be described below.

As illustrated inFIG.3, the support substrate50is provided on a back surface (lower side inFIG.3) of the organic EL display panel40, and is configured to support the organic EL display panel40in a flat manner. The support substrate50is flexible and includes a flexible metal film. The support substrate50may be formed of (only) a single flexible metal film. The metal film is preferably a member having a large elastic modulus such as a metal thin film, and is formed of, for example, a material containing at least one selected from stainless steel, titanium, aluminum, and copper. The thickness (length in the direction Z) of the metal film is, for example, 20 μm and more and 45 μm or less, and preferably 25 μm or more and 35 μm or less. The elastic modulus of the metal film layer is, for example, 60 GPa or more and 210 GPa or less.

The support substrate50further includes a flexible resin film, and may be a layered body (metal film/resin film) including a resin film and a metal film. In addition, the support substrate50may be a layered body (metal film/adhesive layer/resin film) in which an adhesive layer is provided between the metal film and the resin film. The resin film is formed of, for example, an acrylonitrile-butadiene-styrene copolymer (ABS) resin, a polystyrene (PS) resin, a polycarbonate (PC) resin, or a polymethyl methacrylate (PMMA) resin. The thickness (length in the direction Z) of the resin film is, for example, 25 μm and more and 300 μm or less, and preferably 50 μm or more and 150 μm or less. The elastic modulus of the resin film is, for example, 30 MPa or more and 5 GPa or less.

In addition to the metal film and the resin film, the support substrate50may further include an elastomer layer formed of an elastomer (for example, silicon rubber), and may be a layered body including the elastomer layer, the resin film, and the metal film. The support substrate50may be formed of (only) a single elastomer layer. The thickness (length in the direction Z) of the elastomer layer is, for example, 100 μm or more and 500 μm or less. The elastic modulus of the elastomer layer is, for example, 1 MPa or more and 10 MPa or less.

The thickness (in a case of the layered body, the thickness of the entire layered body) of the support substrate50is, for example, 20 μm and more and 500 μm or less, and preferably 30 μm or more and 300 μm or less. From the viewpoint of keeping the shape of the organic EL display panel40flat and preventing undulation, the elastic modulus of the support substrate50is preferably relatively large and is, for example, 1 MPa or more and 210 GPa or less, and preferably 30 MPa or more and 200 GPa or less.

As illustrated inFIG.3, in the organic EL display device70a, the support substrate50is formed of one substrate over the entirety of the organic EL display panel40. In other words, the support substrate50has the same configuration in the non-bendable region RF(flat portions Fa and Fb) and in the bendable region RB(bendable portion B). That is, the support substrate50is also provided (present) on the lower side of the bendable region RB(a portion overlapping the bendable portion B in a plan view). As a result, the support substrate50on the lower side of the bendable portion B is bent in response to the point impact to the bendable portion B or its vicinity, and thus the local deformation of the organic EL display panel40is suppressed. In addition, in the bendable region RB, problems such as undulation of the organic EL display panel40and folding habit at the time of bending are also reduced.

As illustrated inFIG.1andFIG.3, the housing60is a box (case) that accommodates the organic EL display panel40and the support substrate50. As illustrated inFIG.3, the housing60is provided on the lower side of the support substrate50, and is configured to support the support substrate50. The housing60is inflexible (rigid) and is formed of a rigid member such as a metal or a resin. As illustrated inFIG.3, in the housing60, a thickness of a portion overlapping the bendable portion B in a plan view is thin, and a hinge mechanism61is provided in the thin portion. By the hinge mechanism61, the organic EL display device70afunctions as a foldable display that is foldable. Note that the hinge mechanism61is not particularly limited as long as it is a bendable mechanism. The housing60may be provided with a battery, a circuit substrate, and the like.

In the organic EL display device70ahaving the above-described configuration, for example, the organic EL display panel40and the support substrate50are accommodated in the housing60having the hinge mechanism61, and the organic EL display device70ais deformable between a deployed state (seeFIG.1toFIG.3,FIG.4,FIG.6, andFIG.8) in which one flat portion Fa, the bendable portion B, and the other flat portion Fb of the organic EL display panel40are disposed on the same plane and a folded state (seeFIG.5,FIG.7, andFIG.9) in which the bendable portion B is bent and the pair of flat portions Fa and Fb are disposed to face each other.

As illustrated inFIG.3, in the organic EL display device70a, the organic EL display panel40and the support substrate50are not fixed to each other in the entirety of the display region D. Thus, even when the large point impact such as the pen drop is applied, the organic EL display panel40is gently deformed. A non-fixed region between the organic EL display panel40and the support substrate50may not be the entirety of the display region D and may be at least a partial region of the display region D. However, from a viewpoint of the impact resistance, the non-fixed region is preferably provided in the entirety of the display region D.

In the display region D (preferably, its entirety thereof), the organic EL display panel40and the support substrate50may be simply not fixed to each other, and a gap (air gap, space) need not be formed therebetween, or the gap may be formed therebetween.

In addition, as illustrated inFIG.3, in the organic EL display device70a, a gap (air gap) G is formed between the support substrate50and the housing60in the entirety of a region (hereinafter also simply referred to as “display region D”) overlapping the display region D in a plan view. The gap G is a space defined by the support substrate50and the housing60. That is, as illustrated inFIG.3, the support substrate50and the housing60are not fixed to each other in the entirety of the display region D. As a result, the support substrate50can be sufficiently bent toward the lower side (in the direction in which the gap G is present), and thus even the large point impact can be alleviated. Note that the gap G may not be the entirety of the display region D and may be at least a part of the display region D. However, from a viewpoint of the impact resistance, the non-fixed region is preferably provided in the entirety of the display region D.

The gap G may be filled with a gas such as air or an inert gas, or may contain a gas such as air that may be contained in a normal manufacturing process. The gap G may be a completely closed space (a space where air or the like cannot enter and exit) or may be an incompletely closed space (a space where air or the like can enter and exit).

The thickness (length in the direction Z) of the gap G is, for example, about 300 μm, and is preferably 200 μm or more and 750 μm or less, and more preferably 300 μm or more and 450 μm or less from a viewpoint that the support substrate50is sufficiently bent and even the large point impact is alleviated.

As illustrated inFIG.3, examples of a method of forming the gap G include a method of fixing the support substrate50and the housing60via, for example, a fixing member55or the like in a region overlapping the frame region N in a plan view (hereinafter, also simply referred to as “frame region N”). That is, as illustrated inFIG.3, the support substrate50and the housing60are fixed to each other in the frame region N. Specifically, the support substrate50and the housing60are fixed to each other only at a portion overlapping the frame region N in a plan view.

Examples of the fixing member55include a resin or a metal frame provided in a frame shape along the periphery of the display region D so as to overlap the frame region N in a plan view, and a resin or a metal block provided in a rectangular shape, a circular shape, an elliptical shape, or the like in a plan view. For example, a fixing member55having a frame shape may be provided along the entire periphery of the organic EL display panel40along the frame region N. In this case, the gap G defined by the fixing member55having the frame shape, the support substrate50, and the housing60is formed in the above-described completely closed space. In addition, a fixing member55having a block shape may be disposed in an island shape along the frame region N. In this case, the gap G defined by the fixing member55having the block shape, the support substrate50, and the housing60is formed in the above-described incompletely closed space.

The thickness (length in the direction Z) of the fixing member55is not particularly limited, and may be appropriately determined according to the thickness of the gap G described above. The support substrate50and the housing60may be fixed to the fixing member55by adhesive fixing by providing an adhesive layer (an optical clear adhesive (OCA), an adhesive tape, a sponge cushion, or the like), or by screwing fixing using a screw or the like. In a case where the gap G is formed between the support substrate50and the housing60by adopting the adhesive fixing using a thick adhesive tape, a sponge cushion, or the like or the screw fixing, the fixing member55need not be used.

Similarly to the above, as illustrated inFIG.3, the organic EL display panel40and the support substrate50are fixed to each other in the frame region N. Specifically, the organic EL display panel40and the support substrate50are fixed to each other only in the frame region N.

The organic EL display panel40and the support substrate50may be fixed to each other by the adhesive fixing by providing the adhesive layer (the optical clear adhesive (OCA), the adhesive tape, the sponge cushion, or the like), or by the screwing fixing using the screw or the like. When the adhesive fixing is adopted, as illustrated inFIG.3, an adhesive layer48having a frame shape along the periphery of the display region D may be provided between the organic EL display panel40and the support substrate50so as to overlap the frame region N in a plan view. In this case, the adhesive layer48is provided along the entire periphery of the organic EL display panel40along the frame region N. In other words, the adhesive layer48is provided with an opening in a portion overlapping the display region D in a plan view. That is, the adhesive layer48includes an opening (hereinafter also referred to as “display region opening”)48a(seeFIGS.4,6, and8) formed in the portion overlapping the display region D in a plan view. The thickness (length in the direction Z) of the adhesive layer48may be relatively thick, and is preferably 15 μm or more and 100 μm or less. The elastic modulus of the adhesive layer48is preferably 2.0×104[Pa] or more and 1.0×106[Pa] or less, and more preferably 3.0×104[Pa] or more and 1.5×105[Pa] or less.

As described above, as illustrated inFIG.3, in the organic EL display device70a, in a portion (a portion corresponding to the frame region N) overlapping the frame region N in a plan view, the upper face of the support substrate50is fixed to the lower face of the organic EL display panel40and the lower face of the support substrate50is fixed to the upper face of the housing60. On the other hand, in the entirety of a portion (portion corresponding to the display region D) overlapping the display region D in a plan view, the support substrate50is not fixed to any of the organic EL display panel40and the housing60, and the gap G is present on the lower side of the support substrate50. As a result, in the organic EL display device70a, the impact resistance against the large point impact is improved while maintaining excellent flexibility.

First Modification Example of First Embodiment

As illustrated inFIG.4andFIG.5, the adhesive layer48may also be provided with an opening in a portion overlapping the frame region N in a plan view. That is, the adhesive layer48may include, in addition to the display region opening48a, a pair of openings (hereinafter also referred to as “frame region openings”)48band48bformed in portions, respectively, where the bendable region RBextending along the bendable portion B and the frame region N overlap each other in a plan view. In this case, as illustrated inFIG.4, the adhesive layer48is divided (separated) into two parts by the pair of frame region openings48band48band the two parts are disposed to be separated from each other. InFIG.4, the organic EL display panel40is omitted. InFIG.6, the housing60is omitted.

In the first modification example, as illustrated inFIG.4, each of the pair of frame region openings48band48bis formed in the entirety of a portion where the frame region N and the bendable portion B (bendable region RB) overlap each other in a plan view, and is provided in a rectangular shape in a plan view. That is, as illustrated inFIG.4andFIG.5, the organic EL display panel40and the support substrate50are not fixed to each other in a portion overlapping the entirety of the bendable region RBincluding the bendable portion B in a plan view. As a result, even when there is a difference in the amount of deflection due to the difference in elastic modulus between the organic EL display panel40and the support substrate50, the organic EL display panel40and the support substrate50are less likely to affect each other. In this case, the adhesive layer48may be thin, and is, for example, about 2 μm or more and about 50 μm or less.

Second Modification Example of First Embodiment

As illustrated inFIG.6andFIG.7, the adhesive layer48may include, in addition to the display region opening48a, a pair of frame region openings48cand48cformed in a portion where the bendable region RBextending along the bendable portion B and the frame region N overlap each other in a plan view. In this case, as illustrated inFIG.6, the adhesive layer48is divided (separated) into two parts by the pair of frame region openings48cand48c, respectively, and the two parts are disposed to be separated from each other. InFIG.6, the organic EL display panel40is omitted. InFIG.7, the housing60is omitted.

As illustrated inFIG.6andFIG.7, in the second modification example, the pair of frame region openings48cand48care different in shape, size, and the like from the pair of frame region openings48band48bin the first modification example. Specifically, as illustrated inFIG.6, each of the pair of frame region openings48cand48cis formed in a slit shape extending along the bending axis C (direction Y) of the bendable portion B (bendable region RB). That is, as illustrated inFIG.6andFIG.7, the organic EL display panel40and the support substrate50are not fixed to each other in a portion of the bendable region RBincluding the bendable portion B, which overlaps a region in the vicinity of the bending axis C in a plan view. As a result, even when there is a difference in the amount of deflection due to the difference in elastic modulus between the organic EL display panel40and the support substrate50, the organic EL display panel40and the support substrate50are less likely to affect each other. In this case, the adhesive layer48may be thin, and is, for example, about 2 μm or more and about 50 μm or less.

Third Modification Example of First Embodiment

As illustrated inFIG.8andFIG.9, the adhesive layer48may include, in addition to the display region opening48a, a pair of frame region openings48dand48dformed in portions overlapping a pair of the frame regions N and N provided in peripheries of the pair of flat portions Fa and Fb, respectively, in a plan view. In this case, as illustrated inFIG.8, the adhesive layer48is divided (separated) into four parts by the pair of frame region openings48dand48d, and the four parts are disposed to be separated from each other. InFIG.8, the organic EL display panel40is omitted. InFIG.9, the housing60is omitted.

As illustrated inFIG.8andFIG.9, in the third modification example, the pair of frame region openings48dand48dare different in position, number, and the like from the pair of frame region openings48cand48cin the second modification example. Specifically, as illustrated inFIG.8, in the adhesive layer48, two pairs (four in total) of frame region openings48dand48dare formed in portions closer to the bendable portion B in the pair of frame regions N and N provided in the peripheries of the pair of flat portions Fa and Fb, respectively. More specifically, each of the pair of frame region openings48dand48dis formed in the slit shape extending along the bending axis C (direction Y) of the bendable portion B similarly to the second modification example in the vicinity of the bendable region RB(bendable portion B) which is a portion where the non-bendable region RFand the frame region N overlap each other in a plan view. That is, as illustrated inFIG.8andFIG.9, the organic EL display panel40and the support substrate50are not fixed to each other in portions of the non-bendable region RFincluding the pair of flat portions Fa and Fb, which overlap regions in the vicinity of both ends in the direction X of the bendable region RBincluding the bendable portion B in a plan view. As a result, even when there is a difference in the amount of deflection due to the difference in elastic modulus between the organic EL display panel40and the support substrate50, the organic EL display panel40and the support substrate50are less likely to affect each other. In this case, the adhesive layer48may be thin, and is, for example, about 2 μm or more and about 50 μm or less.

As illustrated inFIG.3, the organic EL display panel40includes a flexible display layer41, a function layer42, and a cover43, which are layered in this order.

As illustrated inFIG.10, a plurality of subpixels P are disposed in a matrix shape in the display region D of the flexible display layer41(organic EL display panel40). In addition, as illustrated inFIG.10, in the display region D, for example, a subpixel P including a red light-emitting region Lr for displaying a red color, a subpixel P including a green light-emitting region Lg for displaying a green color, and a subpixel P including a blue light-emitting region Lb for displaying a blue color are provided adjacent to one another. Note that one pixel is configured by, for example, three adjacent subpixels P including the red light-emitting region Lr, the green light-emitting region Lg, and the blue light-emitting region Lb in the display region D.

As illustrated inFIG.11, in the flexible display layer41(organic EL display panel40), the organic EL display device70aincludes a resin substrate layer10provided as a base substrate, the TFT layer20provided on the resin substrate layer10, an organic EL element layer30provided as a light-emitting element layer on the TFT layer20, and a sealing film35provided on the organic EL element layer30.

The resin substrate layer10is formed, for example, of a polyimide resin.

As illustrated inFIG.11, the TFT layer20includes a base coat film11provided on the resin substrate layer10, a plurality of first TFTs9a, a plurality of second TFTs9b, and a plurality of capacitors9cprovided on the base coat film11, and a flattening film19provided on each of the first TFTs9a, each of the second TFTs9b, and each of the capacitors9c. Here, as illustrated inFIG.11, on the TFT layer20, the base coat film11, semiconductor layers12aand12b, a gate insulating film13, a first wiring line layer such as a gate line14(seeFIG.10), gate electrodes14aand14b, and a lower conductive layer14c, a first interlayer insulating film15, an upper conductive layer16, a second interlayer insulating film17, a second wiring line layer such as a source line18f(seeFIG.10), source electrodes18aand18c, drain electrodes18band18d, and a power source line18g, and the flattening film19are layered in this order on the resin substrate layer10. In addition, as illustrated inFIG.10andFIG.12, on the TFT layer20, a plurality of the gate lines14are provided extending in parallel to one another in the lateral direction in the figures. In addition, as illustrated inFIG.10andFIG.12, on the TFT layer20, a plurality of the source lines18fare provided extending in parallel to one another in the longitudinal direction in the figures. In addition, as illustrated inFIG.10andFIG.12, on the TFT layer20, a plurality of the power source lines18gare provided extending in parallel to one another in the longitudinal direction in the figures. Note that, as illustrated inFIG.10, each of the power source lines18gis provided in a state of being adjacent to each of the source lines18f. In the TFT layer20, as illustrated inFIG.12, each of the subpixels P is provided with the first TFT9a, the second TFT9b, and the capacitor9c.

For example, each of the base coat film11, the gate insulating film13, the first interlayer insulating film15, and the second interlayer insulating film17is composed of a single-layer film or a layered film of an inorganic insulating film of silicon nitride, silicon oxide, silicon oxynitride, or the like.

The first TFT9aand the second TFT9bare p-type TFTs in which the semiconductor layers12aand12b(described later) are doped with a dopant such as boron, for example.

As illustrated inFIG.12, the first TFT9ais electrically connected to the corresponding gate line14and source line18fin each of the subpixels P. Additionally, as illustrated inFIG.11, the first TFT9aincludes a semiconductor layer12a, a gate insulating film13, a gate electrode14a, a first interlayer insulating film15, a second interlayer insulating film17, and a source electrode18aand a drain electrode18b, which are sequentially provided on the base coat film11. Here, as illustrated inFIG.11, the semiconductor layer12ais provided in an island shape on the base coat film11, and has, for example, a channel region, a source region, and a drain region. In addition, as illustrated inFIG.11, the gate insulating film13is provided so as to cover the semiconductor layer12a. Additionally, as illustrated inFIG.11, the gate electrode14ais provided on the gate insulating film13so as to overlap the channel region of the semiconductor layer12a. Additionally, as illustrated inFIG.11, the first interlayer insulating film15and the second interlayer insulating film17are sequentially provided so as to cover the gate electrode14a. Additionally, as illustrated inFIG.11, the source electrode18aand the drain electrode18bare separated from each other on the second interlayer insulating film17. Additionally, as illustrated inFIG.11, the source electrode18aand the drain electrode18bare electrically connected to the source region and the drain region of the semiconductor layer12a, respectively, via each contact hole formed in a layered film including the gate insulating film13, the first interlayer insulating film15, and the second interlayer insulating film17.

As illustrated inFIG.12, the second TFT9bis electrically connected to the corresponding first TFT9aand power source line18gin each of the subpixels P. As illustrated inFIG.11, the second TFT9bincludes the semiconductor layer12b, the gate insulating film13, the gate electrode14b, the first interlayer insulating film15, the second interlayer insulating film17, and the source electrode18cand the drain electrode18d, which are provided in this order on the base coat film11. Here, as illustrated inFIG.11, the semiconductor layer12bis provided in an island shape on the base coat film11and has, for example, a channel region, a source region, and a drain region. Additionally, as illustrated inFIG.11, the gate insulating film13is provided so as to cover the semiconductor layer12b. Additionally, as illustrated inFIG.11, the gate electrode14bis provided on the gate insulating film13so as to overlap the channel region of the semiconductor layer12b. Additionally, as illustrated inFIG.11, the first interlayer insulating film15and the second interlayer insulating film17are sequentially provided so as to cover the gate electrode14b. Additionally, as illustrated inFIG.11, the source electrode18cand the drain electrode18dare separated from each other on the second interlayer insulating film17. Additionally, as illustrated inFIG.11, the source electrode18cand the drain electrode18dare electrically connected to the source region and the drain region of the semiconductor layer12b, respectively, via each contact hole formed in a layered film including the gate insulating film13, the first interlayer insulating film15, and the second interlayer insulating film17.

Note that, in the present embodiment, the first TFT9aand the second TFT9bare exemplified as being of a top-gate type TFT, but the first TFT9aand the second TFT9bmay be a bottom-gate type TFT.

As illustrated inFIG.12, the capacitor9cis electrically connected to the corresponding first TFT9aand power source line18gin each of the subpixels P. Here, as illustrated inFIG.11, the capacitor9cincludes the lower conductive layer14c, the first interlayer insulating film15provided to cover the lower conductive layer14c, and the upper conductive layer16provided on the first interlayer insulating film15to overlap the lower conductive layer14c. Note that, as illustrated inFIG.11, the upper conductive layer16is electrically connected to the power source line18gvia a contact hole formed in the second interlayer insulating film17.

The flattening film19has a flat surface in the display region D, and is formed of an organic resin material such as a polyimide resin, for example.

As illustrated inFIG.11, the organic EL element layer30includes a plurality of organic EL elements25as a plurality of light-emitting elements arrayed in a matrix shape corresponding to the plurality of subpixels P.

As illustrated inFIG.11, the organic EL element25includes a first electrode21provided on the flattening film19in each of the subpixels P, the organic EL layer23provided in each of the subpixels P on the first electrode21, and a second electrode24provided on the organic EL layer23commonly to the plurality of subpixels P.

As illustrated inFIG.11, the first electrode21is electrically connected to the drain electrode18dof the second TFT9bof each of the subpixels P via a contact hole formed in the flattening film19. In addition, the first electrode21has a function of injecting holes (positive holes) into the organic EL layer23. In addition, the first electrode21is preferably formed of a material with a high work function to improve the efficiency of hole injection into the organic EL layer23. Here, examples of a material constituting the first electrode21include 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 the material constituting the first electrode21may include alloys such as astatine (At)/astatine oxide (AtO2). Furthermore, the material constituting the first electrode21may be an electrically conductive oxide, for example, tin oxide (SnO), zinc oxide (ZnO), indium tin oxide (ITO), or indium zinc oxide (IZO). In addition, the first electrode21may be formed by layering a plurality of layers formed of any of the materials described above. Note that examples of compound materials having a high work function include indium tin oxide (ITO) and indium zinc oxide (IZO). Furthermore, a peripheral end portion of the first electrode21is covered with an edge cover22provided in a lattice shape commonly to the plurality of subpixels P. Here, examples of a material constituting the edge cover22include a positive-working photosensitive resin such as a polyimide resin, an acrylic resin, a polysiloxane resin, and a novolac resin.

As illustrated inFIG.13, the organic EL layer23includes a hole injection layer1, a hole transport layer2, a light-emitting layer3, an electron transport layer4, and an electron injection layer5that are sequentially provided on the first electrode21.

The hole injection layer1is also referred to as an anode electrode buffer layer, and has a function of reducing an energy level difference between the first electrode21and the organic EL layer23to thereby improve the efficiency of hole injection into the organic EL layer23from the first electrode21. Here, examples of materials constituting the hole injection layer1include triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, phenylenediamine derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, and stilbene derivatives.

The electron injection layer5has a function of reducing an energy level difference between the second electrode24and the organic EL layer23to thereby improve the efficiency of electron injection into the organic EL layer23from the second electrode24, and the electron injection layer5can lower the drive voltage of the organic EL element25by this function. Note that the electron injection layer5is also referred to as a cathode electrode buffer layer. Here, examples of materials constituting the electron injection layer5include inorganic alkaline compounds, such as lithium fluoride (LiF), magnesium fluoride (MgF2), calcium fluoride (CaF2), strontium fluoride (SrF2), and barium fluoride (BaF2), aluminum oxide (Al2O3), and strontium oxide (SrO).

As illustrated inFIG.11, the second electrode24is provided to cover the organic EL layer23of each of the subpixels P and the edge cover22. In addition, the second electrode24has a function of injecting electrons into the organic EL layer23. In addition, the second electrode24is preferably formed of a material with a low work function to improve the efficiency of electron injection into the organic EL layer23. Here, examples of materials constituting the second electrode24include 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 electrode24may also be formed of an alloy such as magnesium (Mg)/copper (Cu), magnesium (Mg)/silver (Ag), sodium (Na)/potassium (K), astatine (At)/astatine oxide (AtO2), lithium (Li)/aluminum (Al), lithium (Li)/calcium (Ca)/aluminum (Al), and lithium fluoride (LiF)/calcium (Ca)/aluminum (Al), for example. In addition, the second electrode24may be formed of electrically conductive oxide, for example, tin oxide (SnO), zinc oxide (ZnO), indium tin oxide (ITO), indium zinc oxide (IZO), or the like. In addition, the second electrode24may be formed by layering a plurality of layers formed of any of the materials described above. Note that examples of materials having 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).

As illustrated inFIG.11, the sealing film35is provided on the organic EL element layer30to cover each of the organic EL elements25. Here, as illustrated inFIG.11, the sealing film35includes a first inorganic sealing film31provided to cover the second electrode24, an organic sealing film32provided on the first inorganic sealing film31, and a second inorganic sealing film33provided to cover the organic sealing film32, and has a function of protecting the organic EL layer23from moisture, oxygen, and the like. Here, the first inorganic sealing film31and the second inorganic sealing film33are formed of an inorganic material such as, for example, silicon oxide (SiO2), aluminum oxide (Al2O3), silicon nitride (SiNx (where x is a positive number)) such as trisilicon tetranitride (Si3N4), or silicon carbonitride (SiCN). The organic sealing film32is formed of an organic material such as an acrylic resin, a polyurea resin, a parylene resin, a polyimide resin, or a polyamide resin.

As illustrated inFIG.3, the function layer42is provided on the flexible display layer41so as to cover the flexible display layer41. Examples of the function layer42include a functional film having a various functions such as an optical compensation function, a touch panel sensor function, and a protection function. The function layer42has flexibility in order to ensure flexibility of the organic EL display panel. If necessary, the adhesive layer (OCA) may be provided between the flexible display layer41and the function layer42.

As illustrated inFIG.3, the cover43is provided on the function layer42so as to cover the function layer42. The cover43protects the flexible display layer41(and the function layer42). The cover43is flexible in order to ensure the flexibility of the organic EL display panel. The flexible cover43is formed of, for example, a UV-curable organosilicon resin. Specific examples of the cover43include a known window film that has been subjected to a hardcoating process. If necessary, the adhesive layer (OCA) may be provided between the function layer42and the cover43.

The above-described organic EL display device70a, in each of the subpixels P, inputs a gate signal to the first TFT9avia the gate line14to turn on the first TFT9a, writes a voltage corresponding to a source signal to the gate electrode14band the capacitor9cof the second TFT9bvia the source line18f, and supplies the organic EL layer23with a current from the power source line18gdefined based on the gate voltage of the second TFT9b, whereby the light-emitting layer3of the organic EL layer23emits light to display an image. Note that, in the organic EL display device70a, even when the first TFT9ais turned off, the gate voltage of the second TFT9bis held by the capacitor9c. Thus, the light emission by the light-emitting layer3is maintained until the gate signal of the next frame is input.

EXAMPLE

The disclosure will be described below based on examples. Note that the disclosure is not limited to the following examples, the following examples can be modified and changed based on the gist of the disclosure, and they are not intended to be excluded from the scope of the disclosure.

Comparative Example 1

A flexible organic EL display panel was manufactured in which a flexible display layer, a function layer, and a cover were layered in order. By using the organic EL display device (foldable display) including only the flexible organic EL display panel, a drop impact test and a bending test were performed based on a method described below. As a result, according to the organic EL display device of a comparative example 1, the bending test was passed, but the drop impact test was failed because a point defect caused by breakage of the TFT layer occurred.

Drop Impact Test

The flexible organic EL display panel was placed on a plastic underlayer (thickness was 50 mm). In this state, a ballpoint pen was dropped from a height 10 cm away from the panel surface so that a pen tip of the ballpoint pen dropped (pen drop) on the panel surface.

Bending Test

Test Preparation

The non-bendable region RFof the flexible organic EL panel (seeFIG.1andFIG.2) was fixed to a fixing plate formed of plastic. A double-sided adhesive tape was used as a method for fixing to the fixing plate. The fixing plate may be formed of a metal, and may be fixed to the panel by using an adhesive, and in this case, the test result is less likely to be affected.

Subsequently, the organic EL panel fixed to the fixing plate was set in a bending test apparatus (manufactured by Yuasa System Co., Ltd., product number: DMLHP) via the fixing plate so that a bending radius R of the bendable region RFwas from 2.0 mm to 3.0 mm. At this time, the cover43(seeFIG.3) of the organic EL display panel was set to be on the inner side of the bend.

Test Procedure

The organic EL panel was bent 200000 times at a bending speed 30 rpm at room temperature (about 25° C.) by alternately repeating a non-bent state (0°) in which the organic EL panel was not bent and a bent state (180°) in which the organic EL panel was bent.

Comparative Example 2

An adhesive layer having thickness of 50 μm was provided on the back surface (back surface of the flexible display layer) of the flexible organic EL display panel obtained in the comparative example 1, and a support substrate (stainless steel plate, thickness: 30 μm, elastic modulus: about 193 GPa) was adhesively fixed via the adhesive layer. The entirety region (the entire organic EL display panel) including the display region D and the frame region N (the bendable region RBand the non-bendable region RF) was adhesively fixed between the support substrate and the organic EL display panel. The drop impact test and the bending test were performed in the same manner as described above using an organic EL display device (foldable display) including a layered body in which the support substrate was adhesively fixed to the entire back surface of the organic EL display panel. As a result, according to the organic EL display device of a comparative example 2, the bending test was passed, but the drop impact test was failed because a point defect caused by breakage of the TFT layer occurred. The reason why the organic EL display panel passed the bending test is considered as follows: the relatively thick adhesive layer was provided in the comparative example 2, and thus the adhesive layer slipped (the adhesive layer was deformed in the thickness direction), and breakage of the organic EL display panel due to bending was prevented.

Comparative Example 3

In the same manner as in the comparative example 2 except that the adhesive layer having a thickness of 5 μm or less was used, the organic EL display device (foldable display) including the layered body in which the support substrate was adhesively fixed to the entire back surface of the organic EL display panel was manufactured, and the drop impact test and the bending test were performed in the same manner as described above. As a result, according to the organic EL display device of a comparative example 3, the drop impact test was passed, but the bending test was failed because a display defect caused by breakage of the TFT layer occurred.

Comparative Example 4

An adhesive layer having a thickness of 50 μm and formed in a frame shape so as to overlap the frame region N of the organic EL display panel in a plan view was provided on the back surface (back surface of the flexible display layer) of the flexible organic EL display panel obtained in the comparative example 1, and the same support substrate as that of the comparative example 2 was adhesively fixed via the adhesive layer. Subsequently, an adhesive layer having a thickness of 50 μm was provided on the entire back surface of the support substrate, and a pseudo housing (formed of metal, hereinafter simply referred to as “housing”) having a pseudo hinge mechanism was adhesively fixed via the adhesive layer. The housing and the support substrate were adhesively fixed to each other in the entire region (entire organic EL display panel) including the display region D and the frame region N (the bendable region RBand the non-bendable region RF).

In a comparative example 4, the support substrate and the organic EL display panel are adhesively fixed to each other only in the frame region N (the entirety of the frame region N, the entire periphery along the peripheral edge of the frame region N), while they are not adhesively fixed to each other in the display region D. A gap having a thickness of about 50 μm (hereinafter referred to as “upper gap” in the examples) is formed between the support substrate and the organic EL display panel.

By using the organic EL display device obtained above (the foldable display, a layered body in which the support substrate was not adhesively fixed in the display region D of the back surface of the organic EL display panel), the drop impact test and the bending test were performed in the same manner as described above. As a result, according to the organic EL display device of a comparative example 4, the bending test was passed, but the drop impact test was failed because a point defect caused by breakage of the TFT layer occurred. Not that no improvement in the impact resistance was observed even when the thickness of the upper gap was increased to 1200 μm.

In the same manner as in the comparative example 4, the same support substrate as that of the comparative example 2 was adhesively fixed on the back surface of the flexible organic EL display panel via the adhesive layer having a frame shape along the periphery of the display region D so that the thickness of the upper gap was about 50 μm. Subsequently, a fixing member (a resin frame having a thickness of 300 μm) formed in a frame shape so as to overlap the frame region N of the organic EL display panel in a plan view was provided on the back surface of the support substrate, and the same housing as that of the comparative example 4 was adhesively fixed via the fixing member. Note that a double-sided adhesive tape was used to fix the support substrate and the housing to the fixing member.

In the example 1, in the display region D, not only the support substrate and the organic EL display panel are not adhesively fixed to each other, but also the support substrate and the housing are not adhesively fixed to each other, and a gap having a thickness of about 300 μm (hereinafter referred to as “lower gap” in the examples) is formed between the support substrate and the housing. As described above, in the example 1, in the display region D, the lower gap and the upper gap are formed on the back surface (lower face) and the front surface (upper face) of the support substrate, respectively, and the total thickness of the two gaps is about 350 μm.

By using the organic EL display device obtained above (the foldable display, the layered body in which the display panel and the support substrate were not fixed to each other and the gap was formed between the support substrate and the housing in the display region D), the drop impact test and the bending test were performed in the same manner as described above. As a result, according to the organic EL display device of the example 1, both the drop impact test and the bending test were passed. Thus, it was found that in the organic EL display device of the example 1, both the impact resistance against the large point impact and the flexibility of the display panel can be achieved. Specifically, by further providing the gap (lower gap) having the thickness of about 300 μm between the support substrate and the housing, the impact resistance was improved even when the total thickness of the gaps was 400 μm or less in the entire device.

Effect

As described above, according to the organic EL display device70aof the present embodiment, the following effects can be obtained.

As described above, in the organic EL display device such as the foldable display that is foldable, since it is necessary to maintain flexibility, the organic EL display panel includes only a flexible member, and in this respect, the followings are required to be improved.

(A) Impact resistance is poor.

(B) It is relatively difficult to keep the organic EL display panel in a flat shape due to occurrence of undulation, warping, or the like.

(C) Depending on a method or means for solving the problems (A) and (B), the flexibility of the organic EL display panel may not be maintained.

(1) Regarding the above points, in the organic EL display device70a, the support substrate50is provided on the lower side of the flexible organic EL display panel40. The support substrate50is formed of a single plate so as to cover the entire organic EL display panel40and a member being flexible but having a large elastic modulus (for example, about 193 GPa) is used, and thus the shape of the organic EL display panel40can be kept flat and the undulation can be prevented (the point (B) can be improved).

(2) In the organic EL display device70a, in the display region D, the organic EL display panel40and the support substrate50are not fixed to each other, and the gap G defined by the support substrate50and the housing60is formed. Specifically, in the display region D, the adhesive layer or the like is not present between the organic EL display panel40and the support substrate50, and the organic EL display panel40and the support substrate50can bend independently of each other. That is, even when there is a difference in the amount of deflection due to the difference in elastic modulus, the organic EL display panel40and the support substrate50are less likely to affect each other. Furthermore, there is a sufficient gap G that can be an air cushion on the lower side of the support substrate50. As a result, even when the surface of the organic EL display panel40receives the large point impact such as the pen drop, the support substrate50can be gently and sufficiently bent, and thus, a local impact is less likely to occur, and the impact can be dispersed and alleviated (the point (A) can be improved). As a result, a crack is less likely to occur in the inorganic film constituting the TFT layer20of the organic EL display panel40, and the occurrence of the display defect can be reduced.

(3) In the organic EL display device70a, the flexibility of the organic EL display panel40is also maintained (the point (C) can be improved).

(4) Thus, in the organic EL display device70a, both the impact resistance against the large point impact and the flexibility of the organic EL display panel40can be achieved (the points (A), (B), and (C) can be simultaneously solved).

(5) In addition, when any one of the above-described first to third modification examples is applied to the organic EL display device70a, in the adhesive layer48provided between the organic EL display panel40and the support substrate50, the pair of frame region openings48b,48c, and48dare formed in the vicinity of the bendable region RBincluding the bendable portion B which is the portion overlapping the frame region N in a plan view. In the frame region openings48b,48c, and48d, the organic EL display panel40and the support substrate50are not adhesively fixed to each other, and thus even when there is a difference in the amount of deflection due to the difference in elastic modulus between the organic EL display panel40and the support substrate50, the organic EL display panel40and the support substrate50are less likely to affect each other. Thus, the flexibility of the organic EL display panel40can be further improved. In this case, the adhesive layer48can be made relatively thin (for example, about 2 μm or more and about 50 μm or less).

Second Embodiment

Next, a second embodiment of the disclosure will be described.FIG.14andFIG.15illustrate a second embodiment of the display device according to the disclosure.FIG.14is a cross-sectional view illustrating a deployed state of an organic EL display device70baccording to the present embodiment, and is a view corresponding toFIG.3.FIG.15is a cross-sectional view illustrating the deployed state of a modification example of the organic EL display device70b, and is a view corresponding toFIG.3.

The entire configuration of the organic EL display device70bis the same as the case of the first embodiment described above other than the configuration between the organic EL display panel40and the support substrate50, and thus detailed description thereof will be omitted. Note that constituent portions similar to those in the first embodiment are denoted by the same reference signs, and a description thereof will be omitted.

As illustrated inFIG.14, in the organic EL display device70b, a metal film layer45is provided between the organic EL display panel40and the support substrate50. The metal film layer45is disposed on the back surface of the organic EL display panel40, and thus the point impact received by the surface of the organic EL display panel40is converted into a surface impact. The metal film layer45is preferably a member having a large elastic modulus (for example, about 193 GPa) such as a metal thin film, and is formed of, for example, a material containing at least one selected from stainless steel, titanium, aluminum, and copper. The thickness of the metal film layer45is, for example, 20 μm and more and 45 μm or less, and preferably 25 μm or more and 35 μm or less. The elastic modulus of the metal film layer45is, for example, 100 GPa or more and 210 GPa or less, and preferably 120 GPa or more and 200 GPa or less.

As illustrated inFIG.14, in the organic EL display device70b, the organic EL display panel40and the support substrate50are fixed to each other via the metal film layer45in the frame region N of the organic EL display panel40.

Specifically, as illustrated inFIG.14, an adhesive layer44is provided between the organic EL display panel40and the metal film layer45, and the organic EL display panel40and the metal film layer45are adhesively fixed to each other via the adhesive layer44. Examples of the adhesive layer44include the OCA, the adhesive tape, and the sponge cushion. From the viewpoint of flexibility, the adhesive layer44is preferably relatively thick and soft, and, for example, has a thickness of 15 μm or more and 100 μm or less and a shear modulus of 500 kPa or less at 25° C. The adhesive layer44may be provided on the entire surface of the organic EL display panel40or the metal film layer45(entire surface adhesion), or may be provided on at least a part thereof (partial adhesion). In addition, the adhesive layer44need not be provided (non-adhesion).

The metal film layer45may be fix to the support substrate50by adopting a method similar to the method of fixing the organic EL display panel40to the support substrate50in the organic EL display device70aaccording to the first embodiment (including above-described first to third modification examples). Specifically, as illustrated inFIG.14, the metal film layer45and the support substrate50are not fixed to each other in the region (preferably, the entirety thereof) overlapping the display region D in a plan view. In the region (preferably, the entirety thereof) overlapping the display region D in a plan view, it is sufficient that the metal film layer45and the support substrate50are simply not fixed to each other, and a gap need not be formed or may be formed between the metal film layer45and the support substrate50.

Modification Example of Second Embodiment

As illustrated inFIG.15, in the organic EL display device70b, a cushion layer (shock absorption layer)47may be provided between the metal film layer45and the support substrate50. The cushion layer47is disposed on a lower side of the metal film layer45(on the back surface of the organic EL display panel40), and thus an impact received by the surface of the organic EL display panel40is absorbed by the cushion layer47.

The cushion layer47is formed of a single layer or a plurality of layers including at least one layer selected from a flexible resin film layer, a graphite sheet layer, and a foam layer (foam). A preferred form of the cushion layer47includes the flexible resin film layer. Examples of the flexible resin film layer include a urethane resin-based film and the like, and Young's modulus is preferably 1 GPa or less, and more preferably 100 MPa or less. The cushion layer47may be a layered body including, in addition to the flexible resin film layer, the graphite sheet layer and/or the foam layer. When the graphite sheet layer is present, a soaking effect of the organic EL display panel40is obtained. The thickness of the cushion layer47is, for example, 25 μm or more and 500 μm or less, and preferably 50 μm or more and 200 μm or less.

As illustrated inFIG.15, in the modification example, the organic EL display panel40and the support substrate50are fixed to each other via the metal film layer45and the cushion layer47in the frame region N of the organic EL display panel40.

Specifically, as illustrated inFIG.15, an adhesive layer46is provided between the metal film layer45and the cushion layer47, and the metal film layer45and the cushion layer47are adhesively fixed to each other via the adhesive layer46. Examples of the adhesive layer46include the OCA, the adhesive tape, and the sponge cushion. From the viewpoint of flexibility, the adhesive layer46is preferably relatively thick and soft, and, for example, has a thickness of 15 μm or more and 50 μm or less and a shear modulus of 100 kPa or less at 25° C. The adhesive layer46may be provided on the entire surface of the metal film layer45or the cushion layer47(entire surface adhesion), or may be provided on at least a part thereof (partial adhesion). In addition, the adhesive layer46need not be provided, and the cushion layer47may be formed as a layered body further including the adhesive layer46. In addition, the metal film layer45and the cushion layer47need not be adhesively fixed to each other.

The cushion layer47may be fix to the support substrate50by adopting a method similar to the method of fixing the organic EL display panel40to the support substrate50in the organic EL display device70aaccording to the first embodiment (including the first to third modification examples). That is, as illustrated inFIG.15, the cushion layer47and the support substrate50are not fixed to each other in the region (preferably, the entirety thereof) overlapping the display region D in a plan view. In the region (preferably, the entirety thereof) overlapping the display region D in a plan view, it is sufficient that the cushion layer47and the support substrate50are simply not fixed to each other, and a gap need not be formed or may be formed between the cushion layer47and the support substrate50.

As described above, according to the organic EL display device70baccording to the present embodiment, the following effects can be obtained in addition to the above-described effects (1) to (5).

(6) In the organic EL display device70b, the metal film layer45is provided on the lower side of the organic EL display panel40, and the metal film layer45and the support substrate50are not fixed to each other in the region overlapping the display region D in a plan view. Thus, the point impact can be converted into the surface impact. As a result, the metal film layer45and the support substrate50are gently bent, and thus the impact resistance against the large point impact can be further improved.

(7) The organic EL display device70bincludes the metal film layer45having a high elastic modulus on the lower side of the organic EL display panel40, and thus the undulation or the warping of the organic EL display panel40can be further prevented.

(8) In the organic EL display device70b, even in a case where the thickness of the gap G between the support substrate50and the housing60is small, the impact resistance is as excellent as that of an organic EL display device (for example, the above-described organic EL display device70a) that does not include the metal film layer45. That is, in the organic EL display device70b, the thickness of the gap G can be made small.

(9) In addition, when the above-described modification example is applied to the organic EL display device70b, the cushion layer47serving as the impact absorption layer is provided on the lower side of the metal film layer45, and the cushion layer47and the support substrate50are not fixed to each other in the region overlapping the display region D in a plan view. As a result, even when the large impact is applied, the impact applied to the support substrate50disposed on the lower side of the cushion layer47is alleviated. Thus, the impact resistance can be further improved. In this case, the thickness of the gap G can be further made small.

Third Embodiment

Next, a third embodiment of the disclosure will be described.FIG.16toFIG.18illustrate a third embodiment of the display device according to the disclosure.FIG.16is a cross-sectional view illustrating a deployed state of an organic EL display device70caccording to the present embodiment, and is a view corresponding toFIG.3.FIG.17is an enlarged cross-sectional view illustrating a folded state in which the organic EL display device70cis folded in the U-shape, and is a view corresponding toFIG.5.FIG.18is an enlarged cross-sectional view illustrating a folded state in which the organic EL display device70cis folded in the droplet shape, and is a view corresponding toFIG.5.

The entire configuration of the organic EL display device70cis the same as the case of the second embodiment described above other than the configuration of the metal film layer45, and detailed description thereof will be omitted. Constituent portions similar to those in the first and the second embodiments are denoted by the same reference signs, and a description thereof will be omitted.

As illustrated inFIG.16toFIG.18, in the organic EL display device70c, the metal film layer45is provided between the organic EL display panel40and the support substrate50similarly to the organic EL display device70baccording to the second embodiment described above, but the organic EL display device70cis different in that the metal film layer45includes openings. InFIG.17andFIG.18, the adhesive layer44and46and the housing60are omitted.

Specifically, as illustrated inFIG.16toFIG.18, the metal film layer45includes a pair of openings (hereinafter also referred to as “metal openings”)45aand45aformed in portions closer to the bendable portion B in the frame regions N and N provided in the peripheries of the pair of flat portions Fa and Fb, respectively. Each of the pair of metal openings45aand45ais formed in a slit shape extending along the bending axis C (direction Y) of the bendable portion B. Each of the metal openings45ahaving the slit shape may be formed up to both ends in the direction Y, or may be formed up to the vicinity of both ends in the direction Y. In addition, each of the metal openings45ais not limited to the slit shape linearly extending along the direction Y, and may be formed in an island shape (dotted line shape) along the direction Y.

As illustrated inFIG.17, in the case where the bent shape of the organic EL display panel40is the U-shape, the pair of metal openings45aand45aare disposed at portions corresponding to the vicinity of the bendable portion B (bendable region RB) in the pair of flat portions Fa and Fb (non-bendable region RF), respectively. As illustrated inFIG.18, in a case where the bent shape of the organic EL display panel40is a droplet shape, the pair of metal openings45aand45aare disposed at portions corresponding to the vicinities of inflection points of an outward bending region and an inward bending region in the pair of flat portions Fa and Fb, respectively. As illustrated inFIG.16, the metal film layer45is divided (separated) into a plurality of parts (three parts inFIG.16) by the pair of metal openings45aand45a, and the parts are disposed to be separated from each other. As a result, a decrease in flexibility of the organic EL display panel40due to the metal film layer45is suppressed.

As illustrated inFIG.16toFIG.18, in the organic EL display device70c, the cushion layer47(and the adhesive layer46) is provided on the lower side of the metal film layer45, but the cushion layer47(and the adhesive layer46) need not be provided.

As described above, according to the organic EL display device70caccording to the present embodiment, the following effects can be obtained in addition to the above-described effects (1) to (9).

(10) In the organic EL display device70c, the metal film layer45provided on the lower side of the organic EL display panel40includes the pair of metal openings45aand45aformed in the portions corresponding to the vicinity of the bendable region RBin the non-bendable region RF. Thus, the flexibility of the organic EL display panel40is further improved. In this case, even in a case where the adhesive layer44provided between the organic EL display panel40and the metal film layer45is thin (for example, about 5 μm or more and about 45 μm or less), flexibility can be ensured.

Fourth Embodiment

Next, a fourth embodiment of the disclosure will be described.FIG.19andFIG.20illustrate a fourth embodiment of a display device according to the disclosure.FIG.19is a cross-sectional view illustrating a deployed state of an organic EL display device70daccording to the present embodiment, and is a view corresponding toFIG.3.FIG.20is a plan view illustrating a deployed state of the support substrate50constituting the organic EL display device70d.

The entire configuration of the organic EL display device70dis the same as that of the first to third embodiments described above other than the configuration of the support substrate50, and thus detailed description thereof will be omitted. Note that constituent portions similar to those in the first to the third embodiments are denoted by the same reference signs, and a description thereof will be omitted.

As illustrated inFIG.19andFIG.20, in the organic EL display device70d, openings are formed in the support substrate50. Specifically, the support substrate50includes at least one (five inFIG.19andFIG.20) openings (hereinafter also referred to as “substrate openings”)50aformed in a portion (bendable region RBincluding the bendable portion B) overlapping the bendable portion B in a plan view. The substrate openings50acommunicate with (connected to) the gap G defined on the lower side of the support substrate50.

In a case where the support substrate50is thin (for example, less than 100 μm (preferably 20 μm or more and 45 μm or less)) or in a case where the support substrate50is formed of the same material as the metal film layer45, the substrate openings50amay be formed in a shape of a plurality of (five inFIG.20) slits so as to extend along the bending axis C (direction Y) of the bendable portion B up to the vicinities of both ends in the bending axis C direction as illustrated inFIG.20. Each of the substrate openings50ais not limited to the slit shape linearly extending along the direction Y, and may be formed in an island shape (dotted line shape) along the direction Y. In this case, as illustrated inFIG.20, in the bendable portion B, the support substrate50is connected (not divided (separated)) in a direction (direction X) substantially orthogonal to the bending axis C direction outside both ends in the direction Y of each of the substrate openings50a.

In addition, in the support substrate50including the substrate openings50a, a portion overlapping the bendable portion B in a plan view may be formed in, for example, a slotted shape, a lattice shape, a chain shape, a living hinge shape (a lot shape), or the like.

On the other hand, in a case where the support substrate50is thick (for example, about 100 μm or more and about 200 μm or less), the substrate opening50amay be formed as one opening over the entire portion overlapping the bendable portion B in a plan view. In this case, the support substrate50may be divided (separated) into two parts by the substrate opening50a, and the two parts may be disposed to be separated from each other. In other words, the support substrates50and50may be disposed in portions corresponding to the flat portions Fa and Fb, respectively, of the organic EL display panel40.

As illustrated inFIG.19, in the organic EL display device70d, the metal film layer45and the cushion layer47(further, the adhesive layers44and46) are provided between the organic EL display panel40and the support substrate50, but only the metal film layer45(and the adhesive layer44) may be provided, and the metal film layer45and the cushion layer47(further, the adhesive layers44and46) need not be provided. In addition, a cushion layer configured similarly to the cushion layer47may be provided on the lower side of the support substrate50in which the substrate openings50aare formed.

As described above, according to the organic EL display device70daccording to the present embodiment, the following effects can be obtained in addition to the above-described effects (1) to (10).

(11) In the organic EL display device70d, at least one substrate opening50ais formed in the support substrate50in the portion overlapping the bendable portion B in a plan view, and thus even when the support substrate50is relatively thick (for example, about 100 μm or more and about 200 μm or less), the support substrate50can be slightly bent by the gap G present on the lower side of the substrate opening50aand the support substrate50. In the case where the support substrate50is thick, the undulation of the organic EL display panel40can be prevented.

OTHER EMBODIMENTS

The configurations in the above-described embodiments can be appropriately combined and applied.

In each of the embodiments described above, the organic EL layer having a five-layer structure including the hole injection layer, the hole transport layer, the light-emitting layer, the electron transport layer, and the electron injection layer is exemplified, but the organic EL layer may have a three-layer structure including a hole injection-cum-transport layer, a light-emitting layer, and an electron transport-cum-injection layer, for example.

In each of the embodiments described above, the organic EL display device including the first electrode as an anode and the second electrode as a cathode is exemplified. The disclosure is also applicable to an organic EL display device in which the layered structure of the organic EL layer is reversed with the first electrode being a cathode and the second electrode being an anode.

In each of the embodiments described above, the organic EL display device in which the electrode of the TFT connected to the first electrode serves as the drain electrode is exemplified. However, the disclosure is also applicable to an organic EL display device in which the electrode of the TFT connected to the first electrode is referred to as the source electrode.

In addition, in each of the embodiments described above, the organic EL display device is exemplified and described as a display device. The disclosure is also applicable to a display device including a plurality of light-emitting elements that are driven by an electrical current. For example, the disclosure is applicable to a display device including quantum-dot light emitting diodes (QLEDs) that are light-emitting elements using a quantum dot-containing layer.

INDUSTRIAL APPLICABILITY

As described above, the disclosure is useful for the flexible display device, particularly the foldable display.