KR20180121256A - Foldable display device - Google Patents

Abstract

Disclosed is a foldable display device. The foldable display device comprises: a base layer having a first display region, a second display region and a folding region between the first display region and the second display region and locating an organic light emitting diode on a first surface; and a support layer attached to a second surface opposite to the first surface of both surfaces of the base layer. The organic light emitting diode is not located on the folding region. Also, the present invention provides a support member minimizing a defect generated in a folding part of the foldable display device.

Description

FOLDABLE DISPLAY DEVICE}

The present disclosure relates to a folderable display device.

The image display device that realizes various information on the screen is a core technology of the information communication age and it is becoming thinner, lighter, more portable and higher performance. Accordingly, an organic light emitting display device for displaying an image by controlling the amount of light emitted from the organic light emitting device has attracted attention.

The organic light emitting device is advantageous in that it can be made thin as a self-luminous device using a thin light emitting layer between electrodes. A general organic light emitting display has a structure in which a pixel driving circuit and an organic light emitting element are formed on a substrate, and light emitted from the organic light emitting element passes through a substrate or a barrier layer to display an image.

Since the organic light emitting display device is implemented without a separate light source device, it is easy to be implemented as a flexible, bendable, or foldable display device. At this time, a flexible material such as plastic or metal foil is used as the substrate of the organic light emitting display device.

On the other hand, the structure of the display device of the present invention can increase the thickness twice or more as compared with the unfolded state. In order to reduce the thickness of the entire display device in a folded state, the thickness of various components must be minimized, and furthermore, how much the display device can be folded is also important. In addition, the foldable display device is required to be sophisticated in terms of the degree of folding because cracks or the like may occur at a specific radius of curvature or less due to the characteristics of the organic film / inorganic film formed through the thin film process.

It is an object of the present disclosure to propose a folding structure of a foldable display device and a support film used therefor. The problems of the present invention are not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those skilled in the art from the following description.

According to one embodiment of the present disclosure, a display device is provided. The display device according to any one of claims 1 to 3, wherein the display device has a first display area, a second display area, and a folding area between the first display area and the second display area, layer; And a support layer attached to a second surface of the base layer opposite to the first surface, wherein the organic light emitting device is not disposed in the folded region.

The details of other embodiments are included in the detailed description and drawings.

Embodiments of the present invention can provide a support member that minimizes defects that occur at the folding portion of the display device. Furthermore, embodiments of the present disclosure can provide a support member that enhances the structural robustness of the display device. The effects according to the embodiments of the present invention are not limited by the contents exemplified above, and more various effects are included in the specification.

Figure 1 shows an exemplary flexible display device that may be included in an electronic device.
2 is a cross-sectional view illustrating a portion of a display region of an organic light emitting display panel according to an embodiment of the present invention.
FIG. 3 is a plan view showing a folderable display device according to an embodiment of the present invention.
4 is a cross-sectional view of a display device according to an embodiment of the present invention.
5A and 5B are a top view and a cross-sectional view of a support layer according to an embodiment of the present disclosure.
6 is an enlarged view of the portion X in Fig.

Brief Description of the Drawings The advantages and features of the present disclosure, and how to accomplish them, will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims.

The shapes, sizes, ratios, angles, numbers and the like disclosed in the drawings for describing the embodiments of the present invention are illustrative, and thus the present invention is not limited thereto. Like reference numerals refer to like elements throughout the specification. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. Where the terms "comprises", "having", "done", and the like are used in this specification, other portions may be added unless "only" is used. Unless the context clearly dictates otherwise, including the plural unless the context clearly dictates otherwise. In interpreting the constituent elements, it is construed to include the error range even if there is no separate description.

In the case of a description of the positional relationship, for example, if the positional relationship between two parts is described as 'on', 'on top', 'under', and 'next to' Or " direct " is not used, one or more other portions may be located between the two portions. An element or layer is referred to as being another element or layer "on ", including both intervening layers or other elements directly on or in between. When a component is described as being "connected", "coupled", or "connected" to another component, the component may be directly connected or connected to the other component, Quot; intervening "or that each component may be" connected, "" coupled, "or " connected" through other components.

Although the first, second, etc. are used to describe various components, these components are not limited by these terms. These terms are used only to distinguish one component from another. Therefore, the first component mentioned below may be the second component within the technical spirit of the present invention.

The sizes and thicknesses of the individual components shown in the figures are shown for convenience of explanation and the present invention is not necessarily limited to the size and thickness of the components shown. Various embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

Figure 1 shows an exemplary flexible display device that may be included in an electronic device.

The flexible display device refers to a display device provided with flexibility, and includes a display device such as a foldable display device, a bendable display device, a rollable display device, Unbreakable display, etc. < / RTI > Referring to FIG. 1, the display device 100 may include at least one active area. For example, the display device of the present invention may have a plurality of display areas divided into right and left (or up and down) on the basis of a folding line. An array of pixels is formed in the display area. One or more inactive areas may be disposed around the display area. That is, the non-display area may be adjacent to one or more sides of the display area. In Fig. 1, the non-display area surrounds a display area of a rectangular shape. However, the shape of the display region and the shape / arrangement of the non-display region adjacent to the display region are not limited to the example shown in Fig. The display area and the non-display area may be in a form suitable for the design of the electronic device on which the display device 100 is mounted. Illustrative forms of the display area are pentagonal, hexagonal, circular, oval, and the like.

Each pixel in the display area may be associated with a pixel circuit. The pixel circuit may include one or more switching transistors and one or more driving transistors on a backplane. Each pixel circuit may be electrically connected to a gate line and a data line to communicate with one or more driving circuits such as a gate driver and a data driver located in the non-display area.

The driving circuit may be implemented with a thin film transistor (TFT) in the non-display region, as shown in FIG. This driving circuit may be referred to as a gate-in-panel (GIP). In addition, some components, such as a data driver IC, are mounted on a separate printed circuit board, and circuit films such as flexible printed circuit boards (FPCB), chip-on-film (COF), tape- (Pad / bump, pin, etc.) disposed in the non-display area.

The flexible display device 100 may include various additional elements for generating various signals or driving pixels in the display area. An additional element for driving the pixel may include an inverter circuit, a multiplexer, an electrostatic discharge circuit, and the like. The display device 100 may also include additional elements associated with functions other than pixel driving. For example, the display device 100 may include additional elements that provide a touch sensing function, a user authentication function (e.g., fingerprint recognition), a multi-level pressure sensing function, a tactile feedback function, and the like. The above-mentioned additional elements may be located in the non-display area and / or an external circuit connected to the connection interface.

Various portions of the display device 100 can be bent along the bending line BL. The curved line BL may extend horizontally (e.g., in the X direction in FIG. 1), vertically (e.g., in the Y direction in FIG. 1), or diagonally. Based on the design, it can be bent in a combination of horizontal, vertical, and diagonal directions.

As mentioned, one or more edges of the display device 100 may be bent away from the central portion 100-1 along the bend line BL. Although the bent line BL is shown to be positioned close to the edge of the display device 100, the bent line BL may extend across the center portion 100-1, And may extend diagonally at one or more corners of the frame. Such a structure may be such that the display device 100 becomes a foldable display device or a display device on which folding is performed on both sides.

In some embodiments, the curved portion of the flexible display device 100 may include a display area capable of displaying an image. Such a display area is hereinafter referred to as an auxiliary display area. That is, the curved line BL may be placed in the display area such that at least some pixels of the display area are included in the curved part.

2 is a cross-sectional view showing a part of a display area of a display device according to an embodiment of the present invention.

Hereinafter, the flexible display device of FIG. 1 and its display area will be described by taking an organic light emitting display as an example. The OLED display 100 includes thin film transistors 102, 104, 106 and 108, organic light emitting devices 112, 114 and 116, and various functional layers on a base layer 101.

The base layer 101 supports various components of the organic light emitting diode display 100. The base layer 101 may be formed of a transparent insulating material, for example, an insulating material such as glass, plastic, or the like. The substrate (array substrate) may also be referred to as a concept including an element and a functional layer formed thereon, for example, a switching TFT, a driving TFT connected to the switching TFT, an organic light emitting element connected to the driving TFT,

A buffer layer may be located on the base layer 101. The buffer layer is a functional layer for protecting a thin film transistor (TFT) from an impurity such as alkali ions or the like, which flows out from the base layer 101 or the lower layers. The buffer layer may be formed of silicon oxide (SiOx), silicon nitride (SiNx), or a multilayer thereof.

A thin film transistor is placed on the base layer 101 or the buffer layer. The thin film transistor may have a configuration in which a semiconductor layer 102, a gate insulating film 103, a gate electrode 104, an interlayer insulating film 105, and source and drain electrodes 106 and 108 are sequentially arranged. The semiconductor layer 102 is located on the base layer 101 or the buffer layer. The semiconductor layer 102 may be made of polysilicon (p-Si), in which case a predetermined region may be doped with an impurity. Further, the semiconductor layer 102 may be made of amorphous silicon (a-Si), or may be made of various organic semiconductor materials such as pentacene. Further, the semiconductor layer 102 may be made of oxide. The gate insulating film 103 may be formed of an insulating inorganic material such as silicon oxide (SiOx) or silicon nitride (SiNx), or may be formed of an insulating organic material or the like. The gate electrode 104 may be formed of various conductive materials such as Mg, Al, Ni, Cr, Mo, W, Au, Or the like.

The interlayer insulating film 105 may be formed of an insulating material such as silicon oxide (SiOx) or silicon nitride (SiNx), or may be formed of an insulating organic material or the like. A contact hole through which the source and drain regions are exposed may be formed by selective removal of the interlayer insulating film 105 and the gate insulating film 103.

The source and drain electrodes 106 and 108 are formed on the interlayer insulating film 105 in the form of a single layer or a multi-layered structure as an electrode material.

The planarizing layer 107 may be located on the thin film transistor. The planarizing layer 107 protects the thin film transistor and flattenes the top surface thereof. The planarization layer 107 may be formed in various shapes and may be formed of an organic insulating film such as BCB (benzocyclobutene) or acrylic or an inorganic insulating film such as a silicon nitride film (SiNx) or a silicon oxide film (SiOx) It may be formed as a single layer, or it may be composed of a double layer or a multi layer.

The organic light emitting device may have a structure in which a first electrode 112, an organic light emitting layer 114, and a second electrode 116 are sequentially arranged. That is, the organic light emitting device includes a first electrode 112 formed on the planarization layer 107, an organic light emitting layer 114 disposed on the first electrode 112, and a second electrode (not shown) disposed on the organic light emitting layer 114 116).

The first electrode 112 is electrically connected to the drain electrode 108 of the driving thin film transistor through the contact hole. When the organic light emitting display 100 is a top emission type, the first electrode 112 may be made of an opaque conductive material having high reflectance. For example, the first electrode 112 may be formed of silver (Ag), aluminum (Al), gold (Au), molybdenum (Mo), tungsten (W), chromium (Cr) .

The bank 110 is formed in the remaining region except for the light emitting region. Accordingly, the bank 110 has a bank hole for exposing the first electrode 112 corresponding to the light emitting region. The bank 110 may be made of an inorganic insulating material such as a silicon nitride film (SiNx), a silicon oxide film (SiOx), or an organic insulating material such as BCB, acrylic resin or imide resin.

The organic light emitting layer 114 is positioned on the first electrode 112 exposed by the bank 110. [ The organic light emitting layer 114 may include a light emitting layer, an electron injection layer, an electron transport layer, a hole transport layer, a hole injection layer, and the like. The organic light emitting layer may have a single light emitting layer structure that emits a single light or may include a plurality of light emitting layers to emit white light.

And the second electrode 116 is located on the organic light emitting layer 114. When the OLED display 100 is a top emission type, the second electrode 116 may be a transparent conductive layer such as indium tin oxide (ITO) or indium zinc oxide (IZO) Thereby emitting the light generated in the organic light emitting layer 114 to the upper portion of the second electrode 116.

The protective layer 118 and the encapsulation layer 120 are located on the second electrode 116. The protective layer 118 and the sealing layer 120 prevent oxygen and moisture penetration from the outside in order to prevent oxidation of the light emitting material and the electrode material. When the organic light emitting device is exposed to moisture or oxygen, a pixel shrinkage phenomenon in which the light emitting region is reduced or a dark spot in the light emitting region may occur. The passivation layer and / or the encapsulation layer may be composed of an inorganic film made of glass, metal, aluminum oxide (AlOx), or silicon (Si) material, or alternatively, It may be a laminated structure. The inorganic film serves to block penetration of moisture or oxygen, and the organic film serves to flatten the surface of the inorganic film. The reason why the encapsulation layer is formed of a plurality of thin film layers is to make the movement path of water or oxygen longer and more complicated than in the case of a single layer so as to make penetration of moisture / oxygen into the organic light emitting element difficult.

FIG. 3 is a plan view showing a folderable display device according to an embodiment of the present invention.

Conventional foldable display devices have many parts to be improved in terms of repeatability of folding due to material characteristics and limitations, and flatness in long-term storage in a folded state. Specifically, although the folding curvature is relatively different depending on a large number of inorganic substances or metal materials constituting the display device, the folding can not be performed with a curvature of less than 1 mm. Thus, the conventional foldable display device is implemented with a folding curvature of about 3 mm, but the problem of thickness increase after folding is a disadvantage.

As another embodiment, there is a foldable display device using two or more display panels. However, since the width of the bezel is increased and a single display device is assembled with a plurality of panels, there is a problem such as a surface step difference and a screen misalignment .

Thus, the foldable display device of the present invention employs a structure that can be made of a single panel and can further reduce the curvature of the folding and reduce the problems caused by repeated folding-spreading. The foldable display may include at least two display areas A-1 and A-2 and a folded area B between the display areas A-1 and A-2. The folded region includes a structure for reducing deformation due to repetitive folding.

Although only two display areas are shown in Fig. 3, actual implementation products can be composed of two or more display areas. The pixel matrix in the second display area A-2 can be continuously extended from the first display area A-1. Alternatively, in Fig. 3, the first display area and the second display area may be separated from each other with the folded area in between. Some parts of the second display area and the second display area may be electrically connected via one or more leads laid across the folded area.

The pixels of the first display area A-1 and the pixels of the second display area A-2 can be driven as if they are in the same matrix by a driving circuit (e.g., gate driver, data driver, etc.). At this time, the pixels of the first display area A-1 and the pixels of the second display area A-2 can be operated by the same driving circuits. For example, the N-th row pixel of the first display area A-1 and the N-th row pixel of the second display area A-2 may be provided to receive the gate signal from the same gate driver. Depending on the implementation, the pixels of the second display area A-2 may be driven separately from the pixels of the first display area A-1. That is, the pixels of the second display area A-2 can be recognized by the driving circuit as an independent matrix separated from the pixel matrix of the display area. In this case, the pixels of the second display area A-2 can receive signals from one or more separate driving circuits that are different from the driving circuits that supply signals to the pixels of the first display area A-1 .

On the other hand, the second display area A-2 can function as the secondary display area of the flexible display device 100 regardless of its shape. The size ratio of the first display area A-1 to the second display area A-2 is not particularly limited.

4 is a cross-sectional view of a display device according to an embodiment of the present invention.

The display device of claim 1, wherein the foldable display device includes at least two display areas and a folded area between the display areas, wherein the folded area reduces deformation due to repeated folding. The display device of the present invention may have a structure in which a base layer 101, an organic light emitting device (TFT / OLED), a cover layer 140, and a support layer 180 are stacked. An organic light emitting device (TFT / OLED) and a cover layer 140 may be disposed on the base layer 101. An encapsulation layer may be disposed on the organic light emitting diode (OLED). The cover layer 140 may be a cover glass. An adhesive layer 160-1 may be disposed between the organic light emitting diode (TFT / OLED) and the cover layer 140. The support layer 180 may be located under the base layer 101. An adhesive layer 160-2 may be disposed between the base layer 101 and the support layer 180. [ The adhesive layer may be a thermosetting or natural curing adhesive. For example, the adhesive layer may be formed of a material such as OCA or B-PSA (Barrier pressure sensitive adhesive).

The base layer 101 includes a first display area A-1; A second display area A-2; And a folded area (B) between the first display area and the second display area. Since the width of the center bezel correlates with the folding radius, it can be determined based on this, and it is desirable to design the center bezel considering the encapsulation margin (E). The folded region B may be understood as the sum of the actual folded portion C and the encapsulation margin E. [

An organic light emitting element is disposed on one surface (first surface) of the base layer 101. When the base layer 101 is made of plastic, it may be referred to as a plastic film or a plastic substrate. For example, the base layer 101 may be in the form of a film including one selected from the group consisting of a polyimide-based polymer, a polyester-based polymer, a silicone-based polymer, an acrylic polymer, a polyolefin-based polymer, and copolymers thereof. Of these materials, polyimide can be applied to a high-temperature process and is widely used as a plastic substrate because it is a material that can be coated.

A TFT backplane of the above-described display device 100 is implemented on the base layer 101. In some embodiments, the backplane of the display device 100 is implemented with a TFT using a low temperature poly silicon (LTPS) semiconductor layer as an active layer. In one example, the pixel circuit and driving circuit (e.g., GIP) on the base layer 101 may be implemented with NMOS LTPS TFTs. In another example, the backplane of the display device 100 may be implemented as a combination of an NMOS LTPS TFT and a PMOS LTPS TFT. For example, the driving circuit (e.g., GIP) on the base layer 101 may include one or more CMOS circuits to reduce the number of wires for controlling the scan signals on the gate lines.

And, in some embodiments, the above-described display device 100 may employ various kinds of TFTs to implement driving circuits in a pixel circuit in a non-display area and / or a display area. That is, in order to implement the backplane of the display device 100, a combination of an oxide semiconductor TFT and an LTPS TFT may be used. In the backplane, the type of the TFT may be selected according to operating conditions and / or TFT requirements in the associated circuit

An organic light emitting diode is disposed on the TFT. The organic light emitting diode is controlled by a pixel circuit and a driving circuit implemented on the base layer 101 and another external driving circuit connected to the connection interface on the base layer 101. The organic light emitting diode includes a layer of an organic light emitting material that emits light of a specific color (e.g. red, green, blue). In some embodiments, the layer of organic emissive material may have a laminated structure capable of emitting white light (essentially a combination of light of different colors).

At least one support layer 180 may be provided at the bottom of the base layer 101 to increase the strength and / or firmness at a particular portion of the display device 100. The support layer 180 is attached to the opposite surface (second surface) of the surface (first surface) on which the organic light emitting element is present on both surfaces of the base layer 101. The support layer 180 may be formed of a material selected from the group consisting of polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polyethylene ether phthalate, polycarbonate, polyarylate, For example, a thin plastic film composed of a combination of polyether imide, polyether sulfonate, polyimide polyacrylate, and other suitable polymers. Other suitable materials that can be used to form the support layer 180 include thin films, dielectric foil, metal foil, polymer films including polymeric materials in combination with nanoparticles or microparticles, have.

The supporting layer 180 may be a porous film having a through hole 180-H provided in a vertical direction (a direction parallel to the stacking direction of the base layer 101 and the supporting layer). 5A is a plan view of the through hole 180-H, and FIG. 5B is a cross-sectional view. The through hole 180-H corresponds to at least one of the first display area and the second display area as another embodiment (Figs. 5 and 6) This structure can prevent permanent deformation due to repeated folding.

The cover layer 140 may be used to protect the display device 100. On one side of the cover layer 140, an electrode for sensing a user's touch input may be formed. If desired, a separate layer with touch sensitive electrodes and / or other components associated with touch input sensing may be provided within the foldable display device 100. The touch sensing electrode (e.g., the touch driving / sensing electrode) may be formed of a conductive material such as indium tin oxide, a carbon based material such as graphene, a carbon nanotube, a conductive polymer, or a hybrid material made of a mixture of various conductive / non- May be formed of a transparent conductive material. In addition, a metal mesh such as an aluminum mesh or a silver mesh may be used as the touch sensing electrode. Since the folded area is most affected by bending stress, various stress reduction structures are applied to the part in the folded area. To this end, some of the components in the central part (100-1) are not present in at least part of the folded area (B). For example, organic light emitting devices (e.g., pixel circuits and organic light emitting diodes) may not be disposed in the folded region. Also, only a minimum number of layers may be disposed in the folded region. For example, only the base layer 101, the support layer 180, the organic layer 170 on the base layer, and the cover film 140 on the organic layer may be disposed in the folded region B. [ (170) may be a layer for flattening the organic light emitting element and the top of the sealing layer in the display area. 6, an inorganic layer 109 patterned between the base layer 101 and the organic layer 170 may be further formed in the folded region B. The inorganic layer 109 contributes to prevention of moisture permeation. In one embodiment, the inorganic layer 109 may be a buffer layer. The patterning may be implemented through a series of etching processes. The pattern may be in the form of a stripe parallel to the folding axis, and the pitch is designed in consideration of the folding curvature.

While the embodiments of the present invention have been described in detail with reference to the accompanying drawings, it is to be understood that the present invention is not limited to these embodiments, and various modifications may be made without departing from the scope of the present invention. Therefore, the embodiments disclosed herein are for the purpose of describing rather than limiting the technical spirit of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. It is to be understood that each of the features of the various embodiments of the present invention may be combined or combined with each other, partially or wholly, and may be technically variously interlocked and driven by one of ordinary skill in the art and that each embodiment may be implemented independently of one another, . The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

Claims (11)

A base layer having a first display area, a second display area, and a folding area between the first display area and the second display area, the organic light emitting device being disposed on the first surface; And
And a support layer attached to a second side of the base layer opposite the first side of the base layer,
Wherein the organic light emitting element is not disposed in the folded region. The method according to claim 1,
Wherein the base layer is a flexible substrate made of at least one of a polyimide-based polymer, a polyester-based polymer, a silicon-based polymer, an acrylic polymer, and a polyolefin-based polymer. The method according to claim 1,
Wherein the organic light emitting device comprises a pixel circuit and an organic light emitting diode. The method according to claim 1,
Wherein the folded region has the base layer, the support layer under the base layer, the organic layer over the base layer, and the cover layer over the organic layer. 5. The method of claim 4,
Wherein the folded region further includes a patterned inorganic layer between the base layer and the organic material layer. 6. The method of claim 5,
Wherein the inorganic layer is a buffer layer. The method according to claim 1,
Wherein the folding region has a predetermined width based on a folding curvature of the folding-flat display device. The method according to claim 1,
Wherein the supporting layer includes a through hole provided in a direction parallel to the stacking direction of the base layer and the supporting layer. 9. The method of claim 8,
Wherein the through hole is located only in a portion corresponding to the folded region. 9. The method of claim 8,
And the through hole is also in a portion corresponding to at least one of the first display region and the second display region. At least two display areas; And a folded area between the display areas,
Wherein the folding region includes a structure for reducing deformation due to repetitive folding.

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