Flexible display device and touch detection display device

Abstract

A flexible display device and a touch detection display device are provided. The flexible display device includes: a flexible substrate including a display area and a bending area outside the display area, the bending area being bent around a bending axis; an inorganic insulating layer located on the flexible substrate; a cutting unit located in the inorganic insulating layer in the bending area; a stress relaxation layer filling the cutting unit and extending into the display area; a wiring portion located on the stress relaxation layer in the bending area; a planarization layer covering the wiring portion and located on the stress relaxation layer; and a display located on the planarization layer in the display area and electrically connected to the wiring portion.

Description

[0001] Korean Patent Application No. 10-2018-0013437, filed on February 2, 2018 in the Korean Intellectual Property Office and entitled “Flexible Display Device and Touch Detection Display Device” is hereby incorporated by reference in its entirety. Technical Field

[0002] One or more embodiments relate to a flexible display device, and more particularly, to a flexible display device having a bending area. Background Art

[0003] The organic light emitting display device has a self-emission characteristic, and thus does not require a separate light source, so that its thickness and weight are reduced. In addition, the organic light emitting display device has high-level characteristics such as low power consumption, high brightness, and fast response speed.

[0004] An organic light emitting display device includes a substrate, a thin film transistor on the substrate, an organic light emitting device whose emission is controlled by the thin film transistor, and a plurality of insulating layers disposed between electrodes forming the thin film transistor. Recently, an organic light emitting display device including a flexible substrate and having a bent region has been developed. Summary of the invention

[0005] According to one or more embodiments, a flexible display device includes: a flexible substrate, including a display area and a bending area located outside the display area, which is to bend around a bending axis; an inorganic insulating layer located on the flexible substrate; a cutting unit located in the inorganic insulating layer in the bending area; a stress relaxation layer filling the cutting unit and extending into the display area; a wiring portion located on the stress relaxation layer in the bending area; a planarization layer covering the wiring portion and located on the stress relaxation layer; and a display located on the planarization layer in the display area and electrically connected to the wiring portion.

[0006] The inorganic insulating layer may include a plurality of inorganic films.

[0007] In the display area, the planarization layer may be located on the stress relaxation layer.

[0008] The cutting unit may extend in a direction parallel to the bending axis.

[0009] The stress relaxation layer may include an organic insulating material.

[0010] The thickness of the stress relaxation layer in the cutting unit may be greater than the depth of the cutting unit.

[0011] A lower surface of the stress relaxation layer in the cutting unit may be in direct contact with an upper surface of the flexible substrate.

[0012] The flexible display device may further include a thin film transistor that electrically connects the display to the wiring portion and is located in the display area, wherein a distance from an upper surface of the planarization layer to the flexible substrate in an area overlapping with the thin film transistor may be substantially the same as a distance from an upper surface of the planarization layer to the flexible substrate in an area overlapping with the cutting unit.

[0013] The planarization layer may include an organic insulating material.

[0014] The flexible display device may further include a thin film transistor electrically connecting the display to the wiring portion and located in the display region, wherein an upper surface of an uppermost electrode of the thin film transistor is higher than an upper surface of the stress relaxation layer.

[0015] The wiring portion may include the same material as that of the uppermost electrode of the thin film transistor.

[0016] The flexible display device may further include a thin film transistor in the display region electrically connecting the display to the wiring portion, wherein an upper surface of an uppermost electrode of the thin film transistor is lower than or equal to an upper surface of the stress relaxation layer.

[0017] The wiring portion may include the same material as that of the uppermost electrode of the thin film transistor.

[0018] The stress relaxation layer may have an opening, and an uppermost electrode of the thin film transistor may be located in the opening.

[0019] The flexible substrate may include: a first substrate including a polymer resin; a second substrate located on the first substrate and including the polymer resin; and a barrier film located between the first substrate and the second substrate.

[0020] In the cutting unit, a lower surface of the stress relaxation layer may be in direct contact with an upper surface of the second substrate.

[0021] The flexible display device may further include an encapsulation portion covering the display and including at least one inorganic film and at least one organic film.

[0022] According to one or more embodiments, a touch detection display device includes: a flexible substrate, including a display area and a bending area located outside the display area, which is to bend around a bending axis; an inorganic insulating layer located on the flexible substrate; a stress relaxation layer, which fills the cutting unit in the inorganic insulating layer in the bending area and extends into the display area; a wiring portion, which is located on the stress relaxation layer in the bending area; a planarization layer, which covers the wiring portion and is located on the stress relaxation layer; a display, which is located on the planarization layer in the display area and is electrically connected to the wiring portion; a flexible packaging portion, which covers the display; a touch detection layer, which is located on the flexible packaging portion; a color filter, which is located on the touch detection layer; and a black matrix, which is located between the color filters.

[0023] The display may include a first electrode, an organic light emitting layer, and a second electrode, and an inclination angle of the first electrode to a plane parallel to the flexible substrate may be less than 1.0°.

[0024] The color filter and the black matrix may share an overlapping area.

[0025] In the display area, the planarization layer may be located on the stress relaxation layer.

[0026] A pad electrode electrically connected to the wiring portion may be located at an edge of the flexible substrate, and when the bending region is folded, the pad electrode may overlap the display region.

[0027] In the cutting unit, the thickness of the stress relaxation layer may be greater than the depth of the cutting unit.

[0028] The touch detection display device also includes a thin film transistor in the display area that electrically connects the display to the wiring portion, wherein a distance from an upper surface of the planarization layer to the flexible substrate in an area overlapping with the thin film transistor may be substantially the same as a distance from an upper surface of the planarization layer to the flexible substrate in an area overlapping with the cutting unit.

[0029] In addition to the aspects, features and advantages described above, other aspects, features and advantages will become apparent from the detailed description, claims and drawings to implement the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Features will become apparent to those skilled in the art by describing exemplary embodiments in detail with reference to the accompanying drawings, in which:

[0031] Figure 1 shows a schematic perspective view of a flexible display device according to a first embodiment;

[0032] Figure 2 Shows Figure 1 A schematic cross-sectional view of a flexible display device shown in ;

[0033] Figure 3 Shows Shows Figure 1 A schematic perspective view of an unfolded state of a flexible display device shown in ;

[0034] Figure 4 Shows Shows Figure 1 A schematic cross-sectional view of a display area DA and a bending area BA of a flexible display device shown in FIG.

[0035] Figure 5 shows a schematic cross-sectional view showing a display area DA and a bending area BA of a flexible display device according to a comparative example;

[0036] Figure 6 shows the degree of color separation of external light according to the tilt angle when the pixel electrode of the green light emitting pixel is tilted from a surface parallel to the flexible substrate;

[0037] Fig. 7A An image showing a phenomenon in which reflected colors of external light are separated when the tilt angle of the pixel electrode exceeds 1.0° is shown;

[0038] Figure 7B An image showing a phenomenon in which reflected colors of external light are separated when the tilt angle of the pixel electrode is less than 1.0° is shown;

[0039] Figure 8 shows a schematic cross-sectional view showing a display area DA and a bending area BA of a flexible display device according to a second embodiment;

[0040] Fig. 9 shows a schematic cross-sectional view showing a display area DA and a bending area BA of a flexible display device according to a third embodiment; and

[0041] Fig.10 A schematic cross-sectional view showing a display area DA and a bending area BA of a flexible display device according to a fourth embodiment is shown. DETAILED DESCRIPTION

[0042] Reference will now be made in detail to embodiments, examples of which are shown in the accompanying drawings, wherein like reference numerals represent like elements throughout. In this regard, the embodiments may have different forms and should not be construed as being limited to the description set forth herein. Therefore, embodiments are described below only by reference to the accompanying drawings to explain aspects of this specification.

[0043] When a specific element (such as a layer, film, region, or substrate) is described as being "located on" another element through an embodiment, it is understood that the specific element may be "located on" another element directly or via another intermediate element. In addition, for ease of description, the size of the component may be exaggerated or reduced in the drawings. For example, the size and thickness of each component shown in the drawings are arbitrarily shown for ease of description, and the present disclosure is not necessarily limited thereto.

[0044] In an embodiment, the x-axis, y-axis, and z-axis are not limited to the three axes of a rectangular coordinate system, but can be analyzed in a broad sense including the x-axis, y-axis, and z-axis. For example, the x-axis, y-axis, and z-axis can be orthogonal to each other, or can represent different directions that are not orthogonal to each other.

[0045] Figure 1 is a schematic perspective view of a flexible display device 100 according to a first embodiment. Figure 2 yes Figure 1 Schematic cross-sectional view of a flexible display device 100 is shown in FIG. Figure 3 It is shown Figure 1 Schematic perspective view of the unfolded state of the flexible display device 100 shown in FIG. Figure 4 It is shown Figure 1 Schematic cross-sectional view of a display area DA and a bending area BA of a flexible display device 100 shown in FIG.

[0046] Reference Figures 1 to 4 According to the embodiment, the flexible display device 100 may include a flexible substrate 110, a display 120 formed on the flexible substrate 110, an inorganic insulating layer 130, a stress relaxation layer 140, a wiring portion 150, a planarization layer 160, and an encapsulation portion 210. In addition, the flexible display device 100 may further include a pad electrode 170, a chip on film (COF) 180, and a printed circuit board (PCB) 190.

[0047] In the present embodiment, the flexible substrate 110 includes a display area DA in which the display 120 is formed, and includes a bending area BA extending in a first direction (+y direction) and bending about a bending axis BAX in a non-display area NDA outside the display area DA.

[0048] The flexible substrate 110 may include various materials having flexible or bendable properties, for example, polymer resins such as polyethersulfone, polyacrylate, polyetherimide, polyethylene naphthalate, polyethylene terephthalate, polyphenylene sulfide, polyarylate, polyimide, polycarbonate, cellulose acetate propionate, etc. Various modifications may also be made to the flexible substrate 110 so that the flexible substrate 110 may have a multilayer structure including two layers including such a polymer resin and a barrier layer (for example, an inorganic material such as silicon oxide, silicon nitride, or silicon oxynitride) between the two layers.

[0049] The display 120 includes a plurality of pixels and displays an image by combining light emitted from the plurality of pixels. Each pixel may include a pixel circuit and an organic light emitting device. The pixel circuit may include at least two thin film transistors and at least one capacitor to control the light emission of the organic light emitting device. The detailed structure of the display 120 will be described later.

[0050] The bending area BA may be a portion of the non-display area NDA. A plurality of pad electrodes 170 may be formed at the edge of the flexible substrate 110 extending in the second direction (+x direction) from the bending area BA. A wiring portion 150 is electrically connected to the pad electrode 170, and includes signal lines such as scan lines and data lines electrically connected to a plurality of pixels and power lines such as driving voltage lines.

[0051] The pad electrode 170 may be connected to the COF 180. The COF 180 may be replaced by a flexible printed circuit (FPC). The COF 180 may be connected to the PCB 190.

[0052] The COF 180 may include an output wiring portion 181, a driving chip 183, and an input wiring portion 182. The PCB 190 is connected to the input wiring portion 182 of the COF 180, and inputs a control signal for controlling the driving chip 183 of the COF 180 to the COF 180. The output wiring portion 181 of the COF 180 is connected to the pad electrode 170, and outputs power and various signals for controlling the display of the flexible display device 100 to the pad electrode 170.

[0053] When the non-display area NDA including the wiring portion 150 and the pad electrode 170 is located beside the display area DA without being bent (see Figure 3 ), the area of ​​the dead space outside the display 120 increases. The flexible display device 100 according to the present embodiment has a bending area BA formed by bending a portion of the non-display area NDA, wherein the wiring portion 150 extends in this portion of the non-display area NDA. As a result of the bending, the edge of the flexible substrate 110 on which the pad electrode 170 is formed overlaps the display area DA at the rear of the display area DA. Therefore, the dead space outside the display 120 is minimized.

[0054] The bending area BA is bent around the bending axis BAX. The center of curvature of the bending area BA is located on the bending axis BAX. Figure 1 and Figure 2 , the bending axis BAX is parallel to the y-axis.

[0055] The inorganic insulating layer 130 includes at least one inorganic film of a barrier film 131, a buffer film 132, a gate insulating film 133, a first interlayer insulating film 134, and a second interlayer insulating film 135 on the flexible substrate 110. The inorganic insulating layer 130 may be located between electrodes and wirings included in the display 120 to insulate the electrodes and wirings included in the display 120.

[0056] In the present embodiment, the inorganic insulating layer 130 in the bending area BA may have a cutting unit CU extending in a direction (y-axis direction) parallel to the bending axis BAX. The cutting unit CU may be filled with a stress relaxation layer 140 including an organic insulating material. The stress relaxation layer 140 extends into the display area DA. For example, as in Figure 4As can be seen in FIG. 1 , the stress relaxation layer 140 is located on the inorganic insulating layer 130 in the display area DA, that is, between the inorganic insulating layer 130 and the planarization layer 160. Specifically, in the display area DA, the planarization layer 160 may be located on the stress relaxation layer 140, for example, in direct contact with the stress relaxation layer 140.

[0057] The wiring portion 150 may be located on the stress relaxation layer 140 in the non-display area NDA. The wiring portion 150 may include a metal material. The inorganic insulating layer 130 has a flexibility much smaller than that of the wiring portion 150, for example, it may be brittle enough that it may be damaged by an external force. Therefore, if the inorganic insulating layer 130 is located in the bending area BA, cracks may appear therein due to the tension caused by bending. These cracks may propagate to other areas of the inorganic insulating layer 130. Cracks in the inorganic insulating layer 130 may cause the wiring portion 150 to be disconnected, thereby causing abnormal display of the flexible display device 100.

[0058] In the present embodiment, the stress relaxation layer 140 is formed of a material having a lower brittleness than the inorganic insulating layer 130 and a higher flexibility than the inorganic insulating layer 130. For example, the stress relaxation layer 140 may be formed of an organic insulating material (e.g., acryl, epoxy, acrylate, polyimide, benzocyclobutene (BCB), or hexamethyldisiloxane (HMDSO). The stress relaxation layer 140 may be formed by filling the cutting unit CU and closely adhering to the sidewall of the cutting unit CU so that there is no gap between the stress relaxation layer 140 and the inorganic insulating layer 130.

[0059] In addition, in the present embodiment, the stress relaxation layer 140 may have a lower surface that directly contacts not only the sidewall of the cutting unit CU but also the upper surface of the flexible substrate 110 that is the lower surface of the cutting unit CU. Therefore, adhesion with the flexible substrate 110 is also improved.

[0060] Therefore, the flexible display device 100 according to the present embodiment can suppress cracks caused by bending stress in the inorganic insulating layer 130 and prevent disconnection of the wiring portion 150 by forming a cutting unit CU in the inorganic insulating layer 130 in the bending area BA and forming a stress relaxation layer 140 with low brittleness in the cutting unit CU.

[0061] In more detail, the barrier film 131 may be located on the flexible substrate 110. The barrier film 131 blocks the penetration of moisture and oxygen through the flexible substrate 110, and may be composed of silicon oxide (SiO 2 ) and silicon nitride (SiN x ) is formed by alternately and repeatedly stacking a plurality of layers of films.

[0062] The buffer film 132 may be located on the blocking film 131. The buffer film 132 provides a flat surface for forming a pixel circuit thereon, and may include SiO 2 or SiN x .

[0063] The semiconductor layer 121 and the first capacitor electrode 125 are located on the buffer film 132. The semiconductor layer 121 may be polysilicon or an oxide semiconductor, and the semiconductor layer 121 may be an oxide semiconductor that may be covered by a separate protective film. The semiconductor layer 121 may include an undoped channel region and a source region and a drain region located at both sides of the channel region and doped with impurities. The first capacitor electrode 125 may include the same material as that of the semiconductor layer 121.

[0064] The gate insulating film 133 is located on the semiconductor layer 121 and the first capacitor electrode 125. The gate insulating film 133 may be made of SiO 2 or SiN x A single film or a stacked film thereof is formed.

[0065] The gate electrode 122 and the second capacitor electrode 126 are formed on the gate insulating film 133. The gate electrode 122 overlaps the channel region of the semiconductor layer 121. The second capacitor electrode 126 may include the same material as that of the gate electrode 122.

[0066] The first interlayer insulating film 134 is formed on the gate electrode 122 and the second capacitor electrode 126, and the third capacitor electrode 127 may be formed on the first interlayer insulating film 134. The third capacitor electrode 127 may include the same material as that of the gate electrode 122.

[0067] The gate insulating film 133 forms a first dielectric film between the first capacitor electrode 125 and the second capacitor electrode 126 , and the first interlayer insulating film 134 forms a second dielectric film between the second capacitor electrode 126 and the third capacitor electrode 127 , thereby forming the storage capacitor 202 .

[0068] The second interlayer insulating film 135 may be located on the third capacitor electrode 127, and the source electrode 123 and the drain electrode 124 may be located on the second interlayer insulating film 135. The first interlayer insulating film 134 and the second interlayer insulating film 135 may be made of SiO 2 or SiN x A single film or a stacked film thereof is formed.

[0069] The source electrode 123 and the drain electrode 124 in the display area DA are respectively connected to the source region and the drain region of the semiconductor layer 121 through contact holes formed in the gate insulating film 133, the first interlayer insulating film 134, the second interlayer insulating film 135, and the stress relaxation layer 140. Therefore, the source electrode 123 and the drain electrode 124 may be located (e.g., directly located) on the stress relaxation layer 140. Therefore, the source electrode 123 and the drain electrode 124 are higher than the upper surface of the stress relaxation layer 140.

[0070] The wiring portion 150 in the bending area BA may be formed of the same material as the source electrode 123 and the drain electrode 124. The source electrode 123, the drain electrode 124, and the wiring portion 150 may be formed of a metal multilayer film (e.g., molybdenum (Mo) / aluminum (Al) / Mo or titanium (Ti) / Al / Ti).

[0071] The pixel electrode 141 is formed on the planarization layer 160 for each pixel and is connected to the drain electrode 124 of the driving thin film transistor 201 through a via hole VH formed in the planarization layer 160. The driving thin film transistor 201 includes a semiconductor layer 121, a gate electrode 122, a source electrode 123, and a drain electrode 124.

[0072] In addition to the driving thin film transistor 201 and the storage capacitor 202 , the pixel circuit may further include a switching thin film transistor.

[0073] The planarization layer 160 is disposed on the driving thin film transistor 201 and the wiring portion 150. The driving thin film transistor 201 is connected to the organic light emitting device 203 and drives the organic light emitting device 203. The planarization layer 160 may include an organic insulating material or an inorganic insulating material, or may be a composite form of an organic insulating material and an inorganic insulating material.

[0074] The organic light emitting device 203 may include a pixel electrode 141 , an emission layer 142 , and a common electrode 143 .

[0075] The pixel electrode 141 is formed on the planarization layer 160 for each pixel, and is connected to the drain electrode 124 of the driving thin film transistor 201 through a via hole VH formed in the planarization layer 160 .

[0076] The pixel defining film 204 is formed on the upper portion of the planarization layer 160 and the edge of the pixel electrode 141. The pixel defining film 204 defines a pixel having an opening through which the central portion of the pixel electrode 141 is exposed. In addition, the pixel defining film 204 prevents arcing, etc., from occurring at the edge of the pixel electrode 141 by increasing the distance between the edge of the pixel electrode 141 and the common electrode 143 located on the upper portion of the pixel electrode 141. The pixel defining film 204 may be formed of an organic material such as polyimide or HMDSO.

[0077] The emission layer 142 may be located on the pixel electrode 141 , and the common electrode 143 may be over the entire display area DA regardless of the pixel.

[0078] Figure 4 Only the emission layer 142 located on the upper part of the pixel electrode 141 is shown, but an intermediate layer other than the emission layer 142 may be further included between the pixel electrode 141 and the common electrode 143. The intermediate layer of the organic light-emitting device 203 may include a low-molecular material or a high-molecular material. When the intermediate layer includes a low-molecular material, the intermediate layer may have a structure in which a hole injection layer (HIL), a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL), an electron injection layer (EIL), etc. are stacked in a single or composite structure, and may include, for example, copper phthalocyanine (CuPc), N, N'-di(naphthalene-1-yl)-N, N'-diphenyl-benzidine (NPB), tri-8-hydroxyquinoline aluminum (Alq 3 ) etc. These layers can be formed by a vacuum deposition method.

[0079] When the intermediate layer includes a polymer material, the intermediate layer may mainly have a structure including HTL and EML. In this case, the HTL may include polyethylene dioxythiophene (PEDOT), and the EML may include a polymer material of polyphenylene vinylene (PPV), polyfluorene, etc. The intermediate layer may be formed by screen printing, inkjet printing, laser induced thermal imaging (LITI), etc.

[0080] Either one of the pixel electrode 141 and the common electrode 143 injects holes into the emission layer 142, and the other of the pixel electrode 141 and the common electrode 143 injects electrons into the emission layer 142. The electrons and holes combine in the emission layer 142 to generate excitons, and light is emitted by energy generated when the excitons transition from an excited state to a ground state.

[0081] The pixel electrode 141 may be formed of a reflective film, and the common electrode 143 may be formed of a transparent film or a semi-transparent film. Light emitted from the emission layer 142 is reflected from the pixel electrode 141, transmitted through the common electrode 143, and then output to the outside. When the common electrode 143 is formed of a semi-transparent film, a portion of the light reflected from the pixel electrode 141 is re-reflected from the common electrode 143, and the pixel electrode 141 and the common electrode 143 may form a resonant structure, thereby improving light extraction efficiency.

[0082] The organic light emitting device 203 is covered by the encapsulation portion 210. The encapsulation portion 210 may seal the organic light emitting device 203, thereby suppressing degradation of the organic light emitting device 203 caused by moisture and oxygen contained in the external air. The encapsulation portion 210 may have a stacked structure of an inorganic material and an organic material, and may include, for example, a first inorganic film 211, an organic film 212, and a second inorganic film 213.

[0083] Again refer to Figure 4 In the embodiment, the stress relaxation layer 140 fills the cutting unit CU and extends into the display area DA. Therefore, the thickness T of the stress relaxation layer 140 filling the cutting unit CU of the inorganic insulating layer 130 may be greater than the depth D of the cutting unit CU. Therefore, the wiring portion 150 may be in direct contact with the stress relaxation layer 140 without being in direct contact with the inorganic insulating layer 130.

[0084] Figure 5 2 is a schematic cross-sectional view showing a display area DA and a bending area BA of a flexible display device 10 according to a comparative example. Figure 5 Unlike the present embodiment, in the flexible display device 10 according to the comparative example, the stress relaxation layer 140' including the organic insulating material fills the cutting unit CU, but the stress relaxation layer 140' does not extend to the display area DA. Figure 5 As shown in FIG, the planarization layer 160 and the inorganic insulating layer 130 directly contact each other in the bending area BA outside the cutting unit CU. Therefore, the thickness T of the stress relaxation layer 140' in the cutting unit CU of the inorganic insulating layer 130 may not be greater than the depth D of the cutting unit CU.

[0085] In accordance with Figure 5 In the flexible display device 10 of the comparative example, the stress relaxation layer 140' filling the cutting unit CU in the bending area BA does not extend to the display area DA, and the planarization layer 160' may be Figure 4 The planarization layer 160 is different. Figure 5 The stress relaxation layer 140' is not located in the display area DA, so the source electrode 123 and the drain electrode 124 are respectively connected to the source region and the drain region of the semiconductor layer 121 through the contact holes in the first and second interlayer insulating films 134 and 135 and the gate insulating film 133. Figure 5 The components and Figure 4 The elements are the same as those of FIG. 1 and their description will not be repeated.

[0086] As described above, unlike the comparative example, in the flexible display device 100 according to the present embodiment, as described in detail below, the difference between the thickness T of the stress relaxation layer 140 filling the cutting unit CU and the depth D of the cutting unit CU can prevent the color separation of the reflected light reflected from the light-emitting device of the display 120.

[0087] External light incident to the organic light emitting device 203 from the outside of the flexible display device 10 is emitted by being reflected from various electrodes and wirings located inside the flexible display device 10. The reflected external light may be mixed with the light emitted from the emission layer 142, thereby causing noise. Specifically, depending on the flatness of the pixel electrode 141 used as a reflective electrode, the color separation phenomenon of the reflected external light is affected.

[0088] The flatness of the pixel electrode 141 depends on the flatness of the planarization layer 160 directly contacting the pixel electrode 141. The flatness of the planarization layer 160 may depend on the design of thin film transistors, capacitors, and wirings arranged at the lower portion of the planarization layer 160.

[0089] In the flexible display device 10 according to the comparative example, the planarization layer 160 is formed to flatten the display 120. However, due to the height difference caused by the structure of the thin film transistor, the capacitor, and the wiring arranged at the lower portion of the planarization layer 160, the inclination angle θ (see FIG. 1 ) of the pixel electrode 141 with respect to the plane parallel to the flexible substrate 110 is θ. Figure 6 ) exceeds 1.0°.

[0090] However, referring to Figure 4 , the flexible display device 100 according to the present embodiment has a stress relaxation layer 140 including an organic insulating material at the lower portion of the planarization layer 160 and also extending to the display area DA. Therefore, the height difference of the structures of the thin film transistor, the capacitor, and the wiring arranged at the lower portion of the planarization layer 160 is alleviated. Since the planarization layer 160 is formed in a state where the height difference is alleviated, the inclination angle θ of the pixel electrode 141 with the plane parallel to the flexible substrate 110 does not exceed 1.0°. That is, the upper surface of the planarization layer 160 is substantially flat.

[0091] Therefore, according to the present embodiment, the distance from the upper surface of the planarization layer 160 to the flexible substrate 110 in the region overlapping with the driving thin film transistor 201 may be substantially the same as the distance from the upper surface of the planarization layer 160 to the flexible substrate 110 in the region overlapping with the cutting unit CU.

[0092] Fig. 7AAn image showing a phenomenon that reflected colors of external light are separated when the tilt angle of the pixel electrode 141 exceeds 1.0° is shown. That is, reflected external light is not mixed to emit white light but is separated into respective unique colors, thereby generating noise.

[0093] Figure 7B An image showing a phenomenon that the reflected colors of external light are separated when the tilt angle of the pixel electrode 141 is less than 1.0° is shown. Although the color separation of the reflected external light does not completely disappear, when the pixel electrode 141 is tilted at a tilt angle less than 1.0°, the reflected colors of the external light are separated. Fig. 7A Color separation is significantly reduced when compared.

[0094] Figure 6 The degree of color separation of external light according to the tilt angle θ when the pixel electrode 141 of the green light emitting pixel is tilted from a surface parallel to the flexible substrate 110 is shown.

[0095] Figure 6 (a) shows the red band R and green band G of the reflected external light when the tilt angle θ is 0.5° a The relative position of Figure 6 (b) shows the red band R and green band G of the reflected external light when the tilt angle θ is 1.0°. b The relative position of Figure 6 (c) shows the red band R and green band G of the reflected external light when the tilt angle θ is 1.9°. c relative position.

[0096] Green Band G a based on Figure 6 The difference of the red band R in (a) is Δa, and the difference of the green band G b based on Figure 6 The difference of the red band R in (b) is Δb, and the difference of the green band G c based on Figure 6 The difference of the red band R in (c) is Δc. The color separation phenomenon is Figure 6 (a) to Figure 6 (c) increases, that is, it increases as the inclination angle θ increases.

[0097] In the present embodiment, since the stress relaxation layer 140 extends into the display area DA, roughness caused by thin film transistors, capacitors, and wirings arranged at the lower portion of the pixel electrode 141 can be reduced. Since the planarization layer 160 is located on the stress relaxation layer 140, the tilt angle of the pixel electrode 141 can be reduced.

[0098] Therefore, the flexible display device 100 according to the present embodiment may have a bending area BA to reduce the dead space. In addition, by forming a cutting unit CU in the bending area BA and filling the stress relaxation layer 140 in the cutting unit CU, cracks in the inorganic insulating layer and disconnection of the wiring can be prevented. In addition, by extending the stress relaxation layer 140 into the display area DA to reduce the tilt angle of the pixel electrode 141, color separation of external light can be prevented, thereby improving display quality.

[0099] In the following, reference will be made to Figures 8 to 10 Various embodiments of the present disclosure are described.

[0100] Figure 8 1 is a schematic cross-sectional view showing a display area DA and a bending area BA of a flexible display device 200 according to a second embodiment. Figure 4 Describe the differences when compared with Figure 4 The same reference numerals as those in the reference numerals in FIG. Figure 4 The same elements as the elements in .

[0101] The flexible display device 200 according to the second embodiment is different from the flexible display device 100 according to the first embodiment in the pattern of the stress relaxation layer 140 in the display area DA. According to the present embodiment, the stress relaxation layer 140a fills the cutting unit CU in the bending area BA and extends into the display area DA at the same time, but the opening OP1 is located in the stress relaxation layer 140a to expose the positions where the source electrode 123 and the drain electrode 124 are formed.

[0102] The source electrode 123 and the drain electrode 124 are formed in the opening OP1 so that the upper surfaces of the source electrode 123 and the drain electrode 124 are not higher than the upper surface of the stress relaxation layer 140a, for example, may be lower than the upper surface of the stress relaxation layer 140a. Therefore, the source electrode 123 and the drain electrode 124 are not located on the stress relaxation layer 140a. When the source electrode 123 and the drain electrode 124 are formed, the wiring portion 150 may also be formed on the stress relaxation layer 140a at the same time.

[0103] The planarization layer 160 is formed on the source electrode 123 , the drain electrode 124 , and the wiring portion 150 , and the drain electrode 124 is connected to the pixel electrode 141 through a via hole VH formed in the planarization layer 160 .

[0104] Since the source electrode 123 and the drain electrode 124 are formed in the opening OP1, roughness due to the source electrode 123 and the drain electrode 124 disposed at the lower portion of the pixel electrode 141 is small. Therefore, the tilt angle of the pixel electrode 141 can be further reduced when compared with the first embodiment.

[0105] Fig. 9 1 is a schematic cross-sectional view showing a display area DA and a bending area BA of a flexible display device 300 according to a third embodiment. Figure 4 Describe the differences when compared with Figure 4 The same reference numerals as those in the reference numerals in FIG. Figure 4 The same elements as the elements in .

[0106] The flexible display device 300 according to the third embodiment is different from the flexible display device 100 according to the first embodiment in that the flexible display device 300 further includes a touch layer 220 , a color filter 240 , a black matrix 230 , and a protective layer 250 on an encapsulation portion 210 .

[0107] The touch layer 220 includes a first insulating layer 221 formed on the encapsulation part 210, a second insulating layer 222 formed on the first insulating layer 221, and a plurality of touch electrodes 223 formed between the first insulating layer 221 and the second insulating layer 222. Alternatively, the touch layer 220 may include various electrode structures, such as a mesh electrode pattern and a transparent segment electrode.

[0108] The touch layer 220 can detect the touch input based on the change of mutual capacitance caused by the touch input. That is, when the touch input is applied, the mutual capacitance is changed by the touch input, and the touch detector connected to the touch layer 220 can detect the position where the mutual capacitance changes, thereby detecting the touch input.

[0109] Color filter 240 and black matrix 230 are arranged on touch layer 220. Black matrix 230 overlaps with the non-emission area of ​​the pixel, and color filter 240 overlaps with the emission area, respectively. Color filter 240 may include red filter 242, green filter 241, and blue filter 243.

[0110] The black matrix 230 includes a material capable of blocking light. For example, the black matrix 230 may include an organic material having a high light absorptivity. The black matrix 230 may include a black pigment or a black dye. The black matrix 230 includes a photosensitive organic material, for example, a colorant such as a pigment or a dye may be included. The black matrix 230 may have a single layer or a multilayer structure.

[0111] although Fig. 9 The color filter 240 is shown to cover a portion of the black matrix 230 , but the black matrix 230 may cover a portion of the color filter 240 or the color filter 240 may cover a portion of the black matrix 230 according to the formation order of the black matrix 230 and the color filter 240 .

[0112] The color filter 240 can not only transmit the light generated by the organic light emitting device 203 to the outside, but also reduce the reflectivity of the light incident from the outside. When the external light passes through the color filter 240, the light intensity of the external light is reduced to about one third thereof.

[0113] Part of the light that has passed through the color filter 240 is extinguished, and the remaining part of the light is reflected by components arranged below the color filter 240 (e.g., a thin film transistor arranged at a lower portion of the pixel electrode 141, a capacitor, wiring, the packaging portion 210, etc.).

[0114] The reflected light is incident on the color filter 240, and the brightness of the reflected light is reduced while passing through the color filter 240. As a result, since only a portion of the external light is reflected and emitted by the flexible display device 300, external light reflection can be reduced.

[0115] In addition, according to the present embodiment, since not only the external light reflection is reduced by using the color filter 240 and the black matrix 230, but also it is not necessary to use a polarizing film generally used to reduce the external light reflection, the thickness of the flexible display device 300 can be reduced. In addition, a thin display device can be manufactured, and the present embodiment can be used for a foldable or bendable display device.

[0116] As mentioned above, according to Figure 4 Compared with the flexible display device 100 of the first embodiment in the embodiment of the present invention, the flexible display device 300 including the color filter 240 and the black matrix 230 can reduce external light reflection, but the tilt angle of the pixel electrode 141 used as a reflective electrode still affects the external light reflection of the flexible display device 300. According to the present embodiment, since the stress relaxation layer 140 extends into the display area DA, the roughness caused by the thin film transistor, the capacitor, and the wiring arranged at the lower portion of the pixel electrode 141 is small, and since the planarization layer 160 is formed again on the stress relaxation layer 140, the tilt angle of the pixel electrode 141 can be reduced, thereby more effectively reducing external light reflection.

[0117] Fig.10 4 is a schematic cross-sectional view showing a display area DA and a bending area BA of a flexible display device 400 according to a fourth embodiment. Fig. 9 The same reference numerals denote the same elements.

[0118] The flexible display device 400 according to the fourth embodiment is different from the flexible display device 300 according to the third embodiment in the pattern of the stress relaxation layer 140 formed in the display area DA. According to the present embodiment, the stress relaxation layer 140a fills the cutting unit CU of the bending area BA and extends to the display area DA at the same time, but the opening OP1 is located in the stress relaxation layer 140a to expose the positions where the source electrode 123 and the drain electrode 124 are formed.

[0119] The source electrode 123 and the drain electrode 124 are formed in the opening OP1 so that the upper surfaces of the source electrode 123 and the drain electrode 124 are not higher than the upper surface of the stress relaxation layer 140a. When the source electrode 123 and the drain electrode 124 are formed, the wiring portion 150 is also formed together on the stress relaxation layer 140a.

[0120] The planarization layer 160 is formed on the source electrode 123, the drain electrode 124, and the wiring portion 150, and the drain electrode 124 is connected to the pixel electrode 141 through the via hole VH formed in the planarization layer 160. Since the source electrode 123 and the drain electrode 124 are formed in the opening OP1, the roughness caused by the source electrode 123 and the drain electrode 124 arranged at the lower portion of the pixel electrode 141 is small, and thus the tilt angle of the pixel electrode 141 can be further reduced when compared with the third embodiment.

[0121] The flexible display device according to the embodiment may have a bending area formed outside the display area, thereby reducing the dead space. The cutting unit filled with the stress relaxation layer may be located in the bending area. Therefore, cracks in the inorganic insulating layer and disconnection of the wiring can be prevented.

[0122] In addition, the flexible display device according to the embodiment may have a stress relaxation layer extending into the display area to reduce the tilt angle of the pixel electrode, so that color separation of external light is prevented, thereby improving display quality.

[0123] Example embodiments have been disclosed herein, and although specific terms are employed, these terms are used and interpreted in a general and descriptive sense only, and not for purposes of limitation. In some cases, as will be apparent to one of ordinary skill in the art upon filing this application, features, characteristics, and / or elements described in conjunction with a specific embodiment may be used alone or in combination with features, characteristics, and / or elements described in conjunction with other embodiments, unless expressly stated otherwise. Therefore, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the spirit and scope of the invention as set forth in the claims.

Claims

1. A flexible display device, comprising: A flexible substrate comprising a display area and a bending area located outside the display area, wherein the bending area is to bend around a bending axis; An inorganic insulating layer, located on the flexible substrate; a cutting unit, wherein the inorganic insulating layer is completely etched away in the bending region; A stress relaxation layer filling the cutting unit and extending into the display area; a wiring portion located on the stress relaxation layer in the bending region; a planarization layer covering the wiring portion and located on the stress relaxation layer; a display located on the planarization layer in the display region and electrically connected to the wiring portion; as well as a thin film transistor electrically connecting the display to the wiring portion, Wherein, an upper surface of the uppermost electrode of the thin film transistor is higher than an upper surface of the stress relaxation layer.

2. A flexible display device, comprising: A flexible substrate comprising a display area and a bending area located outside the display area, wherein the bending area is to bend around a bending axis; An inorganic insulating layer, located on the flexible substrate; a cutting unit located in the inorganic insulating layer in the bending region; A stress relaxation layer filling the cutting unit and extending into the display area; a wiring portion located on the stress relaxation layer in the bending region; a planarization layer covering the wiring portion and located on the stress relaxation layer; a display located on the planarization layer in the display region and electrically connected to the wiring portion; as well as A thin film transistor electrically connects the display to the wiring portion, wherein the stress relaxation layer has an opening, and an uppermost electrode of the thin film transistor is located in the opening.

3. The flexible display device according to claim 1 or 2, wherein: In the display area, the planarization layer is located on the stress relaxation layer.

4. The flexible display device according to claim 1 or 2, wherein: The cutting unit extends in a direction parallel to the bending axis.

5. The flexible display device according to claim 1 or 2, wherein: The stress relaxation layer includes an organic insulating material.

6. The flexible display device according to claim 1 or 2, wherein: The thickness of the stress relaxation layer in the cutting unit is greater than the depth of the cutting unit.

7. The flexible display device according to claim 1 or 2, wherein: A lower surface of the stress relaxation layer in the cutting unit is in direct contact with an upper surface of the flexible substrate.

8. The flexible display device according to claim 1 or 2, wherein: The planarization layer includes an organic insulating material.

9. The flexible display device according to claim 1 or 2, wherein: A distance from an upper surface of the planarization layer to the flexible substrate in a region overlapping the thin film transistor is the same as a distance from an upper surface of the planarization layer to the flexible substrate in a region overlapping the cutting unit.

10. The flexible display device according to claim 1 or 2, wherein: The wiring portion includes the same material as that of the uppermost electrode of the thin film transistor.

11. The flexible display device according to claim 2, wherein: An upper surface of the uppermost electrode of the thin film transistor is lower than an upper surface of the stress relaxation layer or is at the same height as an upper surface of the stress relaxation layer.

12. The flexible display device according to claim 1 or 2, wherein: The flexible substrate comprises: a first substrate comprising a polymer resin; a second substrate located on the first substrate and comprising a polymer resin; and The barrier film is located between the first substrate and the second substrate.

13. The flexible display device according to claim 12, wherein: In the cutting unit, a lower surface of the stress relaxation layer is in direct contact with an upper surface of the second substrate.

14. A touch detection display device, the touch detection display device comprising: A flexible substrate comprising a display area and a bending area located outside the display area, wherein the bending area is bent around a bending axis; An inorganic insulating layer, located on the flexible substrate; A stress relaxation layer filling the cutting units in the inorganic insulating layer in the bending region and extending into the display region; a wiring portion located on the stress relaxation layer in the bending region; a planarization layer covering the wiring portion and located on the stress relaxation layer; a display located on the planarization layer in the display region and electrically connected to the wiring portion; a thin film transistor electrically connecting the display to the wiring portion in the display region, the upper surface of the uppermost electrode of the thin film transistor being higher than the upper surface of the stress relaxation layer; A flexible packaging portion covering the display; A touch detection layer, located on the flexible packaging part; a color filter, located on the touch detection layer; as well as The black matrix is ​​located between the color filters.

15. The touch detection display device according to claim 14, wherein: The display comprises a first electrode, an organic light emitting layer, and a second electrode, and The first electrode has an inclination angle with respect to a plane parallel to the flexible substrate that is less than 1.0°.

16. The touch detection display device according to claim 14, wherein: In the display area, the planarization layer is located on the stress relaxation layer.

17. The touch detection display device according to claim 14, wherein: The color filter shares an overlapping area with the black matrix.

18. The touch detection display device according to claim 14, wherein: A pad electrode electrically connected to the wiring portion is located at an edge of the flexible substrate, and when the bending region is bent, the pad electrode overlaps the display region.

19. The touch detection display device according to claim 14, wherein: The thickness of the stress relaxation layer is greater than the depth of the cutting unit.

20. The touch detection display device according to claim 14, in, A distance from an upper surface of the planarization layer to the flexible substrate in a region overlapping the thin film transistor and a distance from the upper surface of the planarization layer to the flexible substrate in a region overlapping the cutting unit are the same.

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