KR102609540B1 - Flexible display device - Google Patents

Abstract

This specification discloses a flexible display device. The flexible display device includes a first portion in which an organic light emitting element is disposed on a first side, and a second portion outside the first portion having a curved section bent toward a second side opposite the first side. A base layer made of a flexible substrate including; and a protective coating layer covering at least a portion of the second portion, wherein a polarizing layer is positioned on the organic light emitting device of the first portion without a barrier film, and the protective coating layer has a portion adjacent to the polarizing layer. It is laminated thicker than other parts.

Description

Flexible display device {FLEXIBLE DISPLAY DEVICE}

This specification relates to a flexible display device.

Video display devices, which display various information on a screen, are a core technology of the information and communication era and are developing to be thinner, lighter, more portable, and more high-performance. Accordingly, organic light emitting display devices that display images by controlling the amount of light emitted from organic light emitting elements are receiving attention.

Organic light-emitting devices are self-luminous devices that use a thin light-emitting layer between electrodes and have the advantage of being able to be made into thin films. A typical organic light emitting display device has a structure in which a pixel driving circuit and an organic light emitting element are formed on a substrate, and the light emitted from the organic light emitting element passes through the substrate or 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 display device. At this time, flexible materials such as plastic and thin metal foil are used as substrates for organic light emitting display devices.

Meanwhile, when an organic light emitting display device is implemented as a flexible display device, research is being conducted to bend or curve various parts of the display device using its flexible properties. These studies are mainly conducted for new designs and UI/UX, and in some cases, such studies are also conducted to reduce the area of the corners of display devices.

The purpose of this specification is to propose a bending structure for a flexible display device and a protective coating layer used therein. The tasks of this specification are not limited to the tasks mentioned above, and other tasks not mentioned will be clearly understood by those skilled in the art from the description below.

A flexible display device is provided according to an embodiment of the present specification. The flexible display device includes a first portion in which an organic light emitting element is disposed on a first side, and a second portion outside the first portion having a curved section bent toward a second side opposite the first side. A base layer made of a flexible substrate including; and a protective coating layer covering at least a portion of the second portion, wherein a polarizing layer is positioned on the organic light emitting device of the first portion without a barrier film, and the protective coating layer has a portion adjacent to the polarizing layer. It is laminated thicker than other parts.

The polarizing layer may have a higher moisture resistance than a polarizing layer included in a flexible display device with a barrier film on the organic light emitting device. For example, the polarizing layer may have a water vapor transmission rate (WVTR) of 1.0x10 ^-3 to 1.0x10 ^-4 g/m ² 24hr.

The portion adjacent to the polarizing layer may be a portion between the side surface of the polarizing layer and the curved section, and the other portion may be a portion to which the protective coating layer is applied in a substantially flat manner.

The portion adjacent to the polarizing layer may be a portion of the upper portion of the support layer attached to the second surface of the base layer, and the other portion may be an upper portion of the bent section.

The thickness of the protective coating layer applied to the portion adjacent to the polarizing layer may be 20% to 60% thicker than the thickness of the protective coating layer applied to the other portion.

The thickness of the protective coating layer applied to the other portion is substantially 100 μm, and the thickness of the protective coating layer applied to the portion adjacent to the polarizing layer is 20 to 60 μm thicker than the thickness of the protective coating layer applied to the other portion. You can.

The maximum thickness of the protective coating layer may be less than the thickness of the polarizing layer.

A driver IC chip may be located outside the protective coating layer in the second portion.

A conductive wire connecting the driving circuit chip and the organic light emitting device is disposed in the second portion, and the protective coating layer may cover the conductive wire.

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

Embodiments of the present specification can provide a structure that minimizes defects occurring in curved portions of a flexible display device. More specifically, embodiments of the present specification can provide a coating layer that has excellent adhesion and can uniformly protect the bent section. Accordingly, product reliability of the flexible display device according to an embodiment of the present specification can be improved. The effects according to the embodiments of the present specification are not limited to the contents exemplified above, and further various effects are included in the present specification.

1 shows an example flexible display device that may be included in an electronic device.
Figure 2 shows an exemplary arrangement of flat and curved portions.
3A and 3B show the arrangement of a display area of a flexible display device according to an embodiment of the present specification.
Figure 4 is a cross-sectional view schematically showing the stacked structure of a flexible display device according to an embodiment of the present specification.
Figure 5 is a plan view and a cross-sectional view of a curved pattern according to an embodiment of the present specification.
6A to 6C are schematic cross-sectional views showing exemplary arrangements of components in a flexible display device.
7A and 7B show exemplary structures of multilayer conductors.
Figure 8 shows some examples of strain reduction designs.
9A and 9B show schematic diagrams of a wiring structure with multiple sub-wirings.
10 shows several example interconnection structures with a diamond interconnection design.
11A and 11B show schematic cross-sectional views of example wiring structures.
12A and 12B show schematic views of an exemplary strain-reducing interconnection structure with modified portions.
13A to 13C are diagrams showing the configuration of a protective coating layer used in a flexible display device.
FIGS. 14A and 14B are exemplary diagrams showing a flexible display device to which a protective coating layer is applied.
Figure 15 is a diagram showing part of the manufacturing process of a protective coating layer used in a flexible display device.
Figure 16 is a diagram showing a protective coating layer used in a flexible display device according to an embodiment of the present specification.
Figure 17 is a graph showing the defect rate according to the structure of the protective coating layer.

The advantages and features of the present specification and methods for achieving them will become clear by referring to the embodiments described in detail below along with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and will be implemented in various different forms. The present embodiments only serve to ensure that the disclosure of the present invention is complete and that common knowledge in the technical field to which the present invention pertains is not limited. It is provided to fully inform those who have the scope of the invention, and the present invention is only defined by the scope of the claims.

The shape, size, ratio, angle, number, etc. disclosed in the drawings for explaining the embodiments of the present specification are illustrative, and the present specification is not limited to the matters shown. Like reference numerals refer to like elements throughout the specification. Additionally, in describing the present invention, if it is determined that a detailed description of related known technologies may unnecessarily obscure the gist of the present invention, the detailed description will be omitted. When 'includes', 'has', 'consists of', etc. mentioned in this specification are used, other parts may be added unless 'only' is used. When a component is expressed in the singular, the plural is included unless specifically stated otherwise. When interpreting a component, it is interpreted to include the margin of error even if there is no separate explicit description.

In the case of a description of a positional relationship, for example, if the positional relationship of two parts is described as 'on top', 'on the top', 'on the bottom', 'next to', etc., 'immediately' Alternatively, there may be one or more other parts placed between the two parts, unless 'directly' is used. When an element or layer is referred to as “on” another element or layer, it includes instances where the other layer or other element is directly on top of or interposed between the other elements. When a component is described as being “connected,” “coupled,” or “connected” to another component, that component may be directly connected or connected to that other component, but there are no other components between each component. It should be understood that may be “interposed” or that each component may be “connected,” “combined,” or “connected” through other components.

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

The size and thickness of each component shown in the drawings are shown for convenience of explanation, and the present invention is not necessarily limited to the size and thickness of the components shown. Hereinafter, various embodiments of the present invention will be described in detail with reference to the attached drawings.

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

The flexible display device refers to a display device with flexibility, including a bendable display device, a rollable display device, an unbreakable display device, and a foldable display device. It can be used in the same sense as a foldable display device, etc. Referring to FIG. 1, the flexible display device 100 includes at least one active area, and an array of pixels is formed in the display area. One or more non-display areas (in-display areas) may be arranged around the display area. That is, the non-display area may be adjacent to one or more sides of the display area. In Figure 1, the non-display area surrounds a rectangular display area. However, the shape of the display area and the shape/arrangement of the non-display area adjacent to the display area are not limited to the example shown in FIG. 1. The display area and the non-display area may have a shape suitable for the design of an electronic device equipped with the flexible display device 100. Exemplary shapes of the display area include pentagon, hexagon, circle, oval, etc.

Each pixel within 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.

As shown in FIG. 1, the driving circuit may be implemented as a thin film transistor (TFT) in the non-display area. This driving circuit may be referred to as a gate-in-panel (GIP). Additionally, some components, such as data driver ICs, are mounted on separate printed circuit boards and circuit films such as FPCB (flexible printed circuit board), COF (chip-on-film), TCP (tape-carrier-package), etc. It can be combined with a connection interface (pad/bump, pin, etc.) placed in the non-display area. The non-display area is bent along with the connection interface, so that the printed circuit (COF, PCB, etc.) can be located behind the flexible display device 100.

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

Various parts of the flexible display device 100 may be bent along the bend line BL. The curved line BL may extend horizontally (e.g., the Based on the design, it can be bent in any combination of horizontal, vertical, and diagonal directions.

As mentioned, one or more edges of the flexible display device 100 may be bent away from the central portion 101 along the curved line BL. Although the curved line BL is shown to be located close to the edge of the flexible display device 100, the curved line BL extends across the central portion 101 or It may extend diagonally from one or more corners of . This structure allows the flexible display device 100 to be a foldable display device or a display device that displays displays on both folded sides.

Since one or more portions of the flexible display device 100 may be bent, the flexible display device 100 may be defined as a substantially flat portion and a curved portion. A portion of the flexible display device 100 may be referred to as a central portion 101 that is substantially flat. A portion of the flexible display device 100 is bent at a predetermined angle, and this portion may be referred to as a bent portion 102. The bent portion 102 includes a bent section that is actually bent to a predetermined bending radius.

The term “substantially flat” includes areas that are not perfectly flat. For example, the concave central portion 101a and convex central portion 101b depicted in Figure 2 may also be described as substantially flat portions in some embodiments. 2, one or more bending portions 102 are present next to the concave central portion 101a or convex central portion 101b and are bent inward or outward with an angle to the bending axis along the bending line BL. all. The bending radius of the bending portion 102 is smaller than the bending radius of the central portions 101a and 101b. In other words, the term “substantially flat portion” refers to a portion that has less curvature than adjacent sections.

Depending on the location of the bend line BL, the portion on one side of the bend line is located toward the center of the flexible display device 100, while the portion on the other side of the bend line is located toward the corner of the flexible display device 100. . The portion placed toward the center of the flexible display device 100 may be referred to as a central portion, and the portion located toward the corners of the flexible display device 100 may be referred to as a corner portion. Although this is not always the case, the central portion of the flexible display device 100 may be substantially flat, and the corner portions may be curved portions. It should be mentioned that substantially flat parts can also be located at corners. And, in some shapes of the flexible display device 100, the curved section may lie between two substantially flat portions.

As mentioned, if you bend the non-display area, the non-display area becomes invisible or only minimally visible from the front of the display device. Among the non-display areas, a portion visible from the front of the display device may be obscured by a bezel. The bezel may be a stand-alone structure, or may be formed from a housing or other suitable element. Some of the non-display areas visible from the front of the display may be hidden under an opaque mask layer such as black ink (e.g., a polymer filled with carbon black). This opaque mask layer may be provided on various layers (touch sensor layer, polarizing layer, cover layer, etc.) included in the flexible display device 100.

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

3A and 3B each show the arrangement of the display area of the flexible display device 100 according to an embodiment of the present specification.

In the configuration of Figure 3A, the pixel matrix in the second display area may extend continuously from the display area of the central portion 101. Alternatively, in the shape of FIG. 3B, the second display area in the curved portion 102 and the display area in the central portion 101 may be separated from each other with a curved section in between. Some components of the central portion 101 and the curved portion 102 may be electrically connected through one or more conductors 120 laid across the curved section.

The pixels of the second display area and the pixels of the central display area may be driven by a driving circuit (eg, gate driver, data driver, etc.) as if they were in the same matrix. At this time, the pixels of the second display area and the central display area may be operated by the same driving circuits. For example, the N-th row pixel of the central display area and the N-th row pixel of the second display area may be configured to receive a gate signal from the same gate driver. As shown in FIG. 3B, a portion of the gate wire crossing the curved section or a bridge connecting the gate wires of the two display areas may have a shape to reduce strain.

Depending on the function of the second display area, pixels in the second display area may be driven separately from pixels in the central display area. That is, the pixels of the second display area can be recognized by the driving circuit as an independent matrix separate from the pixel matrix of the display area. In this case, the pixels in the second display area may receive signals from one or more separate driving circuits that are different from the driving circuits that supply signals to the pixels in the central display area.

Regardless of its shape, the second display area of the curved portion may function as a secondary display area of the flexible display device 100. Additionally, the size of the second display area is not particularly limited. The size of the second display area may depend on functions built into the electronic device. For example, the second display area may be used to present images and/or text, such as a graphical user interface (GUI), buttons, text messages, etc. In some cases, the second display area may be used to provide different colors of light for various purposes (eg, status indication), where the size of the second display area need not be as large as the display area within the central portion.

Figure 4 is a cross-sectional view schematically showing the stacked structure of a flexible display device according to an embodiment of the present specification.

In FIG. 4 , for convenience of explanation, the central portion 101 is shown to be substantially flat and the curved portion 102 is shown to be at a corner of the flexible display device 100. As shown, one or more bending portions 102 may bend outward from the central portion 101 with a bending angle θ about the bending axis and a bending radius R. The size of each curved portion 102 need not be the same. That is, the length from the bend line BL to the outer edge of the base layer 106 in each curved portion 102 may be different. Additionally, the bending angle θ around the bending axis and the radius of curvature R from the bending axis may vary for each bending portion 102.

In the example shown in Figure 4, the right side of the curved portion 102 has a bending angle θ of 90°, and the curved portion 102 includes a substantially planar section. The curved portion 102 is bent at a larger bending angle θ, such that a portion of the curved portion 102 can go under the central portion 101, such as the left curved portion 102 of the flexible display device 100. there is. Additionally, the bent portion 102 may be bent at a bending angle θ of 90° or less.

In some embodiments, the radius of curvature of the curved portion 102 may be between about 0.1 mm and about 10 mm, preferably between about 0.1 mm and about 5 mm, or between about 0.1 mm and about 5 mm. It may be between 1 mm, or between about 0.1 mm and about 0.5 mm. In some embodiments, the radius of curvature at curved portion 102 may be less than 0.5 mm.

To increase the strength and/or rigidity of a specific portion of the flexible display device 100, one or more support layers 108 may be provided below the base layer 106. For example, the support layer 108 may be provided on the lower side of the central portion 101. The support layer 108 may not be provided in curved sections where greater flexibility is required. The support layer 108 may be provided on the curved portion 102 located below the central portion 101. Increasing the strength of a specific part helps to accurately configure and place various components in the flexible display device 100. When the base layer 106 has greater elasticity than the support layer 108, the support layer 108 may contribute to suppressing the occurrence of cracks in the base layer 106.

The base layer 106 and the support layer 108 may be made of a thin plastic film composed of a combination of polyimide, polyethylene naphthalate (PEN), polyethylene tereplate, or other suitable polymers. Other suitable materials that can be used to form the base layer 106 and the support layer 108 include thin glass, dielectrically shielded metal foil, multilayer polymers, and polymeric materials in combination with nanoparticles or microparticles. It may be an included polymer film, etc. The support layers 108 provided in various parts of the flexible display device 100 do not all need to be made of the same material. For example, a thin glass layer may be used as the support layer 108 for the central portion 101, while a plastic film may be used as the support layer 108 for the corner portion.

The thickness of the base layer 106 and the support layer 108 are also matters to be considered in the design of the flexible display device 100. From one perspective, if the base layer 106 has excessive thickness, it is difficult for the base layer 106 to bend to a small radius of curvature. Additionally, excessive thickness of the base layer 106 adds mechanical stress to components placed thereon during bending. However, from another perspective, if the base layer 106 is too thin, it is too weak as a substrate to support components placed thereon.

To meet these requirements, the base layer 106 can have a thickness of about 5 μm to about 50 μm, preferably, the base layer 106 ranges from about 5 μm to about 30 μm, or has a thickness of about 5 μm. It can have a thickness ranging from about 16μm. The support layer 108 may have a thickness of about 100 μm to about 125 μm, about 50 μm to about 150 μm, about 75 μm to 200 μm, 150 μm or less, or 100 μm or more.

In one embodiment, a polyimide layer having a thickness between about 10 μm and about 16 μm is used as the base layer 106, and a polyethylene terephthalate (PET) layer having a thickness between about 50 μm and about 125 μm is used as the support layer 108. ) is used. In another embodiment, a polyimide layer having a thickness between about 10 μm and about 16 μm is used as the base layer 106, and a thin glass layer having a thickness between about 50 μm and about 200 μm is used as the support layer 108. In another embodiment, thin glass is used as the base layer 106, which has a polyimide layer serving as the support layer 108 to avoid breakage.

During the manufacturing process, some parts of the flexible display device 100 may be exposed to external light. Materials used to manufacture the components or the components themselves undergo unwanted state changes (e.g., threshold voltage transition in TFT, etc.) due to exposure to light during manufacturing of the flexible display device 100. Some parts of the flexible display device 100 are excessively exposed to external light compared to other parts. And this can cause display unevenness (e.g. mura, shadow defects, etc.). To minimize this problem, the base layer 106 and/or the support layer 108 may include one or more materials that can reduce the amount of external light.

For example, the light blocking material is carbon chloride black mixed with the constituent materials (polyimide, other polymers) of the base layer 106. In this way, the base layer 106 may be formed from polyimide with a shade that provides a light blocking function. This base layer 106 can improve visibility by reducing reflection of external light incident on the front of the flexible display device 100.

Instead of the base layer 106, the support layer 108 is made of a light-blocking material to reduce the amount of light incident from the rear side of the flexible display device 100 (i.e., the side to which the support layer 108 is attached). It may also be included. The constituent materials of the support layer 108 may be mixed with one or more light blocking materials, similar to those described above. Furthermore, both the base layer 106 and the support layer 108 may include one or more light blocking materials. Here, the light blocking materials used for the base layer 106 and the support layer 108 do not need to be the same.

Making the base layer 106 and the support layer 108 block unwanted external light improves display uniformity and reduces reflections, but also creates alignment marks for accurately positioning components, or as part of the manufacturing process. Recognizing alignment marks for performance can become difficult. For example, since the arrangement of the layers is determined by comparing the outline of the overlapping portion, the components are accurately placed on the base layer 106 or aligned during bending of the flexible display device 100. may be more difficult. In addition, if the base layer 106 and/or the support layer 108 blocks an excessive range of light spectrum (i.e., wavelengths of visible light, ultraviolet light, and infrared spectrum), debris or foreign matter within the flexible display device 100 may be removed. Checking can be problematic.

Accordingly, in some embodiments, the light blocking material included in the base layer 106 and/or the support layer 108 blocks light of a specific polarization and/or within a specific wavelength range used in one or more manufacturing/inspection processes. It is configured to pass. As an example, the support layer 108 may pass light (eg, UV, IR) used in quality inspection and/or alignment processes, but may block light in the visible light wavelength range. The limited range of wavelengths is possible when the base layer 106 includes a light blocking material. This helps reduce display non-uniformity problems caused by shading caused by the printed circuit film attached to the base layer 106.

The base layer 106 and the support layer 108 can work together to block or pass a specific type of light. For example, the support layer 108 may change the polarization of light to prevent the light from passing through the base layer 106. As such, certain types of light may pass through the support layer 108 for various purposes during manufacturing of the flexible display device 100, but may not be transmitted to components disposed on the opposite side of the base layer 106. To avoid unnecessary influence, it cannot pass through the base layer 106.

A backplane of the flexible display device 100 is implemented on the base layer 106. In some embodiments, the backplane of the flexible 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 circuits and driving circuits (eg, GIPs) on the base layer 106 may be implemented with NMOS LTPS TFTs. In another example, the backplane of the flexible display device 100 may be implemented as a combination of NMOS LTPS TFTs and PMOS LTPS TFTs. For example, the driving circuit (eg, GIP) on the base layer 106 may include one or more CMOS circuits to reduce the number of wires for controlling the scan signal on the gate line.

And, in some embodiments, the flexible display device 100 may employ various types of TFTs to implement driving circuits in pixel circuits in the non-display area and/or the display area. That is, to implement the backplane of the flexible display device 100, a combination of oxide semiconductor TFT and LTPS TFT can be used. In the backplane, the type of TFT may be selected depending on the operating conditions and/or TFT requirements in the relevant circuitry.

LTPS TFTs generally exhibit excellent carrier mobility even with a small profile, making them suitable for implementing integrated driving circuits. The excellent carrier mobility makes LTPS TFTs ideal for components requiring fast operating speeds. Despite the above-mentioned advantages, the initial threshold voltage may differ between LTPS TFTs due to the grain boundary of the polycrystalline silicon semiconductor layer.

A TFT employing an oxide-based semiconductor layer, such as an indium-gallium-zinc-oxide (IGZO) semiconductor layer (hereinafter referred to as an oxide TFT), differs from the LTPS TFT in many aspects. Despite lower mobility compared to the LTPS TFT, the oxide TFT is generally more advantageous than the LTPS TFT in power efficiency. The low leakage current of the oxide TFT in the off state allows the active state to last longer. This can be a significant advantage for driving pixels at reduced frame rates when high frame rates are not needed to drive the pixels.

As an example, the flexible display device 100 may have a characteristic in which all or part of the pixels of the display area are driven at a reduced frame rate under certain conditions. In this setting, the pixels may be refreshed at a reduced rate depending on the content displayed on the flexible display device 100. Additionally, parts of the display area that display static image data (e.g., user interface, text) may refresh at a lower rate than other parts of the display area that display rapidly changing image data (e.g., movies). there is. Pixels running at reduced refresh rates may experience increased blank periods during which data signals are not provided to the pixels. This will minimize the power consumed by providing the same image data to the pixels. In this embodiment, several TFTs implementing the pixel circuit and/or the driving circuit may be formed of oxide TFTs to minimize leakage current during the blank period leakage in the pixel circuit and/or the driving circuit. By reducing current, the pixel can achieve more stable brightness levels even when the display refreshes at a reduced rate.

Another characteristic of the oxide TFT is that it does not suffer from the problem of initial threshold voltage change between transistors as much as the LTPS TFT. This aspect can be a significant advantage when the size of the flexible display device 100 increases. Additionally, the threshold shift between LTPS TFTs and oxide TFTs under bias stress is different.

Considering the above-mentioned characteristics of LTPS TFT and oxide TFT, some embodiments of the flexible display device 100 can be applied by combining LTPS TFT and oxide TFT on one backplane. In particular, some embodiments of the flexible display device 100 may employ an LTPS TFT to implement a driving circuit (e.g., GIP) in the non-display area and apply an oxide TFT to implement a pixel circuit in the display area. You can. Because of the excellent carrier mobility of LTPS TFTs, compared to driving circuits implemented with oxide TFTs, driving circuits implemented with LTPS TFTs can operate at faster speeds. In addition, a more integrated driving circuit can be provided by the LTPS TFT, thereby reducing the size of the non-display area. Due to the excellent voltage retention ratio of the oxide TFT used in the pixel circuit, leakage current in the pixel can be reduced. This also allows pixels to be driven at reduced frame rates in specific parts of the display area or under preset conditions (e.g. when displaying still images), while minimizing display defects caused by leakage current.

In some embodiments, the pixel circuit may be implemented with an oxide TFT, while the driving circuit may be implemented with a combination of N-type LTPS TFT and P-type LTPS TFT. For example, N-type LTPS TFT and P-type LTPS TFT can be used to implement CMOS gate drivers (e.g. CMOS GIP, data driver). On the other hand, oxide TFT may be applied to at least some parts of the pixel circuit. Unlike GIPs formed entirely of P-type or N-type LTPS TFTs, the gate output signal from the CMOS gate driver can be controlled by DC signals or logic high/low signals. This allows the gate line to be more reliably controlled during blank periods, suppressing current leakage from the pixel circuit and unintentional activation of pixels.

The CMOS gate driver or inverter circuit on the backplane may be implemented with a combination of LTPS TFTs and oxide TFTs. For example, P-type LTPS TFT and N-type oxide TFT can be used to implement CMOS circuits. Additionally, the pixel circuit of the display area may be implemented using both LTPS TFT and oxide TFT. When applying two types of TFTs to the pixel circuit and/or driving circuit, in order to eliminate the bias remaining in the node between the oxide TFTs during the off state and minimize bias stress (e.g. PBTS, NBTS), LTPS TFT Can be strategically placed inside a circuit. Additionally, the TFT connected to the storage capacitor in the circuit may be formed of an oxide TFT to minimize leakage current.

An organic light emitting device (OLED) layer is disposed on the base layer 106. The organic light emitting device layer 150 includes a plurality of OLED devices. The OLED device is controlled by a pixel circuit and a driving circuit implemented on the base layer 106, and another external driving circuit connected to a connection interface on the base layer 106. The OLED layer includes an organic light emitting material layer that emits light of a specific color (eg, red, green, blue). In some embodiments, the organic light-emitting material layer may have a layered structure capable of emitting white light (essentially a combination of light of several colors).

The encapsulation layer 104 is provided to protect the organic light emitting device layer 150 from air and moisture. The encapsulation layer 104 may include several layers of materials to reduce the infiltration of air and moisture. In some embodiments, the encapsulation layer 104 may be provided in the form of a thin film.

The flexible display device 100 may include a polarization layer 110 to control display characteristics (eg, external light reflection, color accuracy, luminance, etc.). Additionally, the cover layer 114 may be used to protect the flexible display device 100.

An electrode for detecting a user's touch input may be formed inside one side of the cover layer 114 and/or at least one side of the polarization layer 110. If necessary, an independent layer (hereinafter referred to as touch sensor layer 112) equipped with touch sensing electrodes and/or other components associated with touch input sensing may be provided in the flexible display device 100. The touch sensing electrode (e.g., touch driving/sensing electrode) is made of indium tin oxide, carbon-based materials such as graphene, carbon nanotubes, conductive polymers, hybrid materials made of mixtures of various conductive/non-conductive materials, etc. It may be formed of a transparent conductive material. Additionally, a metal mesh, such as aluminum mesh or silver mesh, may be used as the touch sensing electrode.

The touch sensor layer 112 may include one or more modified dielectric materials. One or more electrodes may be interfaced with the touch sensor layer 112 or may be located near the touch sensor layer 112, and may read signals measuring electrical changes on the electrodes. The measurement is analyzed and the amount of pressure input to the flexible display device 100 is evaluated in several levels.

In some embodiments, the touch sensing electrode may be utilized to determine the location of user input and evaluate the pressure of the user input. The touch input location confirmation and touch pressure measurement may be performed by measuring the change in capacitance of the touch sensing electrode on one side of the touch sensor layer 112. The touch sensing electrode and/or other electrodes may be used to measure a signal representing pressure on the flexible display device 100 due to a touch input. These signals are obtained from the touch sensing electrode simultaneously with the touch signal or at a different timing.

The deformable material included in the touch sensor layer 112 may be an electrically active material, and the amplitude and/or frequency of the material is controlled by an electric signal and/or an electric field. This deformable material includes piezo ceramic, Includes electro-active-polymer, etc. Accordingly, the touch sensing electrode and/or a separate electrode may activate the deformable material to bend the flexible display device 100 in a desired direction. Additionally, the electrically active material is activated and vibrates at a desired frequency to provide tactile and/or texture feedback on the flexible display device 100. The flexible display device 100 may employ a plurality of electrically active materials so that bending or vibration of the flexible display device 100 may be provided simultaneously or at different timings. This combination can be used to create a sound wave from the flexible display device 100.

Some components may make it difficult to bend the flexible display device 100 along the bend line BL. Some components, such as the support layer 108, the touch sensor layer 112, and the polarization layer 110, may add strength to the flexible display device 100. Additionally, the thickness of the components shifts the neutral plane of the flexible display device 100, thereby creating greater bending stress in some of the components than in other components.

For easier bending and improved reliability of the flexible display device 100, the configuration of components in the curved portion 102 is different from that in the central portion 101. Some components present in the central portion 101 are not disposed in the curved portion 102 or are provided with different thicknesses. The support layer 108, the polarization layer 110, the touch sensor layer 112, the color filter layer, and/or other components that interfere with the bending of the flexible display device 100 may not be in the curved portion 102. there is. If the curved portion 102 is not visible or accessible to the user, such components are not necessary.

To provide information to the user, a second display area is located in the curved portion 102, but depending on the purpose and/or type of information provided by the second display area, some of the above components may not be necessary. . For example, if the second display area only emits colors or displays text or a simple GUI with only a combination of light and dark (e.g., black text or icons on a white background), the polarization layer 110 and/or the color filter layer It is unnecessary for the bent portion 102. Additionally, the curved portion 102 may not have a touch sensor layer 112 if a touch function is not required. Even if an auxiliary display area for displaying information is not provided in the curved portion 102, if necessary, the curved portion 102 may include a touch sensor layer 112 and/or an electrically active material layer.

Since the bending section is most affected by bending stress, various stress reduction structures are applied to parts on the bending section. For this purpose, some of the components in the central part 101 are not present in at least one part of the curved part 102 . By selectively removing components from the bent section, separation is achieved between the parts in the central portion 101 and the bent section 102, thereby freeing the bent section from each component.

As shown in FIG. 4, the support layer 108 in the central portion 101 and the support layer 108 in the curved portion 102 are due to the absence of the support layer 108 in the curved section 102b. may be separated from each other. Instead of the support layer 108 attached to the base layer 106, a support member 116 with rounded ends may be disposed in the curved section below the base layer 106. Various other components, for example, the polarization layer 110, the touch sensor layer 112, etc., may not be present in the curved section. Removal of the components may be accomplished through cutting, etching (wet etching, dry etching), scribing, or other suitable methods. Instead of cutting or other removal, split pieces of the component may be formed in selected portions (e.g., central portion and curved portion), leaving the curved section free of the component. Instead of being completely removed from the flexure portion 102, some components may have a flexure pattern along a portion of the flexure line and/or flexure section to reduce flexure stress.

Figure 5 is a plan view and a cross-sectional view of a curved pattern according to an embodiment of the present specification.

The curved pattern 300 can be applied to several components. The curved pattern 300 can be used for the support layer 108, polarization layer 110, touch sensor layer 112, etc.

The flexible display device 100 may utilize one or more curved patterns 300. The number of bending patterns used in the parts and the shape of the bending patterns are not limited. If desired, the depth of the pattern 300 may be such that it completely passes through the component but only partially penetrates each layer. In order to reduce bending stress, a bending pattern may be provided not only in the passivation layer covering the conductive line but also in the buffer layer between the base layer 106 and the TFT.

As mentioned, the support layer 108 is not present in the bending section to facilitate bending of the base layer 106. However, due to the absence of the support layer 108, the curvature of the bent section is easily deformed by external force. To support the base layer 106 and maintain the curvature of the bent section, the flexible display device 100 may include a support member 116, which may be referred to as a mandrel. there is. The support member 116 shown in FIG. 2 includes a body portion and an end portion. The base layer 106 and the support member 116 are arranged so that rounded ends are located on the lower surface of the base layer 106 corresponding to the curved section.

In an embodiment in which the curved portion 102 is at a corner of the flexible display device 100, the support member 116 may be located at a corner of the flexible display device 100. In this setup, a portion of the base layer 106 surrounds the end of the support member 116 and is located on the underside of the support member 116, as shown in FIG. 2 . Various circuits and components (driver IC, connection interface with COF (connecting chip-on-flex), printed circuit board, etc.) in the non-display area are located on the base layer 106 located behind the flexible display device 100. ) can be provided on the table. In this way, even if it is not a soft part, it can be located below the display area.

The support member 116 may be formed of a plastic material such as polycarbonate (PC), polyimide (PI), polyethylene naphthalate (PEN), or polyethylene terephthalate (PET). The strength of the support member 116 made of the plastic material can be controlled by additives that increase the thickness and/or strength of the support member 116. The support member 116 may be formed in a desired color (eg, black, white, etc.). Additionally, the support member 116 may be made of a hard material such as glass, ceramic, or metal, or a combination thereof.

The size and shape of the end portion of the support member 116 may vary depending on the lowest desired curvature in the curved section. In some embodiments, the thickness of the tip portion and the body portion may be substantially the same. In another embodiment, the planar body portion may be thinner than the tip portion. With a thinner body portion, the support member 116 can support the curved section 102b while avoiding unnecessary increase in the thickness of the flexible display device 100.

Since the bent section is supported by the end portion of the support member 116, the body portion extending toward the central portion 101 of the flexible display device 100 does not need to extend to the display area. If the body portion can extend below the display area for various reasons, the length of the body portion from the end toward the opposite end to the surface area to support the support member 116 is sufficient.

In order to secure the support member 116 within the flexible display device 100, an adhesive layer 118 may be provided on the surface of the support member 116. The adhesive layer 118 may include pressure-sensitive adhesive, foam-type adhesive, liquid adhesive, light-cured adhesive, or other suitable adhesive material. there is. In some embodiments, the adhesive layer 118 is formed of or includes a compressible material and may function as a cushioning material for the portion adhered by the adhesive layer 118. As an example, the adhesive layer 118 The constituent materials of may be compressible. The adhesive layer 118 may be formed in a multi-layer structure, and the multi-layer structure includes a buffer layer (eg, polyolefin foam) disposed between the upper and lower layers of the adhesive material layer.

The adhesive layer 118 may be located on one or more of the upper and lower surfaces of the body portion of the support member 116. When the curved portion 102 of the flexible display device 100 wraps the end of the support member, the adhesive layer 118 is applied to the lower surface (i.e., the side facing the back) and the upper surface (i.e., the front side) of the body portion. (face facing) can be provided on both sides. If desired, an adhesive layer 118 may be provided between the end of the support member 116 and the inner surface of the base layer 106.

During bending, a portion of the flexible display device 100 on one side of the support member 116 may be pulled toward the support member 116, and the base layer 106 may be positioned at the top of the end portion. and may be impacted by the bottom edge. Accordingly, the height of the adhesive layer 118 and the height of the support layer 108 between the support member 116 and the base layer 106 are between the uppermost edge of the end portion and the surface of the body portion where the adhesive layer 118 is located. is more than the vertical distance of In other words, the height of the space created by the difference in thickness between the end portion and the body portion is less than or equal to the combined thickness of the support layer 108 and the adhesive layer 118.

Depending on the shape of the support member 116, the thickness of the adhesive layer 118 on the upper and lower surfaces of the body portion may vary. For example, a body portion that is thinner than the tip may not exist at the center of the tip. In this case, the space on one side of the support member 116 may be larger than the space on the opposite side.

In another example, the lowest edge of the end portion is inside the bottom line of the body portion, creating space only on one side of the body portion. In this case, the adhesive layer 118 on one side of the body portion may be thicker than on the opposite side.

FIGS. 6A, 6B, and 6C are schematic cross-sectional views showing exemplary arrangements of components in various embodiments of the flexible display device 100.

As one configuration example, in FIG. 6A, the thickness of the rounded end portion and the elongated body portion of the support member 116A may be substantially the same. This support member 116A may be formed of a plastic material. The support member 116A may be formed of a folded thin metal sheet (eg, SUS). At this time, the folded edge of the metal sheet may function as a rounded end portion of the support member 116A. Even when metal sheets are used to form the support member, the end portion may be thicker than the body portion. For example, pressure may be applied to a portion of a folded metal sheet such that the body portion becomes thinner than the folded edges.

In Figure 6A, adhesive layer 118A is shown applied to the top, bottom and rounded end surfaces of support member 116A. Since the thickness of the support member 116A in the round portion and the body portion is approximately the same, the adhesive layer 118A has a substantially uniform thickness on the surface of the support member 116A. However, adhesive layer 118A may be thinner or thicker in selected portions of support member 116A.

As another configuration example, the thickness of the elongated body portion of the support member 116 may be thinner than the rounded end portion. In this case, if the support member 116B has a flat bottom as in Figure 6B, the lower surface of the body portion is aligned with the lowest edge of the end portion. In this example configuration, support member 116B may be formed of the previously mentioned plastic materials (eg, polycarbonate, etc.) or a combination thereof. Additionally, the adhesive layer 118B provided on the upper surface of the body portion is thicker than the adhesive layer 118B provided on the lower surface of the body portion. The adhesive layer 118B on the upper surface of the body portion may include a buffer layer, while the adhesive layer 118B on the lower surface may not.

In another configuration shown in Figure 6, neither the top nor bottom surfaces of the body portion of support member 116C are aligned with the top/bottom edges of the rounded portion. The support member 116C may be formed of the previously mentioned plastic materials (eg, polycarbonate, etc.) or a combination thereof. In this example, the body portion is not symmetrical (i.e., closer to the bottom edge of the round portion), and the adhesive layer 118C on the upper surface of the body portion is thicker than the adhesive layer 118C on the lower surface.

The adhesive layer 118C on the surface above the body portion may include the buffer described above, while the adhesive layer 118B on the lower surface may not.

6A to 6C, the support layer 108 above the support member 116 may extend further than the encapsulation layer 114 toward the bend section. In other words, the part of the base layer 106 facing the curved section is not covered by the encapsulation layer 114, but the support layer 108 is provided underneath it. The remaining length of the support layer 108 can help maintain curvature in the bending section. The edge of the support layer 108 below the support member 116 may move away from the curved section. In some embodiments, a flange may be provided at an edge of the support layer 108 facing the curved section. The border may extend further toward the curved section as shown in FIG. 6A. As an example, the edge may be made by cutting or patterning so that the support layer 108 has sharp edges. As another example, the border may be prepared by stacking at least two or more support layers so that the edges are offset from each other. Although omitted in FIGS. 6B and 6C, the border may also be provided in the corresponding embodiment.

The configurations described in FIGS. 6A to 6C are exemplary only. An adhesive layer having the same thickness can be provided on the upper and lower surfaces of the support member regardless of the position of the body portion. And, the adhesive layer on the upper or lower surface of the support member may include a buffer layer.

A plurality of conductors are included in the flexible display device 100 for electrical connection between various components. Circuits manufactured in the display area and non-display area can provide various functions by transmitting various signals through one or more conductors. Several conductors may be used for interconnection between circuits and/or other components in the central and curved sections.

A conductive line refers to a conductive path that transmits electrical signals, power, and/or voltage from one point in the flexible display device 100 to another point. The conductive wire may include a gate line/data line that transfers a signal from a display driving circuit (eg, gate driver, data driver) in the non-display area to a pixel circuit in the display area, and source/drain electrodes of the TFT. Likewise, conductors such as touch sensing electrodes, pressure sensing electrodes, and fingerprint sensing electrodes can provide signals for detecting touch input or fingerprint recognition on the flexible display device 100. Additionally, the conductors are connected to components in the central display area and curved portions. Interconnection between components of the second display area may be provided.

The conductors of the flexible display device 100 must be carefully designed to satisfy electrical and non-electrical requirements. For example, a conductor may have a certain minimum resistance level, which may vary depending on the type of signal to be transmitted through the conductor. Some conductors may be routed from a substantially flat section to a curved section. These conductors must exhibit sufficient flexibility to maintain mechanical/electrical robustness. To this end, some conductors of the flexible display device 100 have a multi-layered structure.

7A and 7B each show an exemplary stacked structure of multilayer conductors.

Referring to FIG. 7A, the conductive wire 120 has a multi-layer structure in which the first conductive layer 122 is sandwiched between the second conductive layers 124. The first conductive layer 122 may be formed of a material having lower electrical resistance than the second conductive layer 124. The first conductive layer 122 includes materials such as copper, aluminum, transparent conductive oxide, and other flexible conductors, but is not limited thereto.

The second conductive layer 124 is formed of a conductive material that exhibits sufficiently small ohmic contact resistance when laminated on the first conductive layer 122. Low contact resistance between the conductive layers in the multilayer conductor 120 is not the only factor to consider when selecting the conductive layer material. While meeting stringent electrical and thermal requirements (e.g., resistance, heat generation, etc.), the conductor 120 material must also meet minimum mechanical strength requirements (e.g., Young's modulus), i.e., the first conductive layer 122 and the second conductive layer 122. The conductive layer 124 must be formed of a material that exhibits sufficient flexibility.

Accordingly, in some embodiments, at least some of the conductors 120 of the flexible display device 100 may be formed of two or more layers selected from aluminum (Al), titanium (Ti), molybdenum (Mo), and copper (Cu) layers. . Examples of such combinations include aluminum layers sandwiched between titanium layers (Ti/Al/Ti), aluminum layers sandwiched between upper and lower molybdenum layers (Mo/Al/Mo), and copper layers sandwiched between titanium layers (Ti/Cu/Ti). , a copper layer (Mo/Cu/Mo) between the upper and lower molybdenum layers, etc. Of course, other conductive materials can also be used as the first/second layer.

Electronic devices employing the flexible display device 100, such as wearable electronic devices or underwater electronic devices, may expose the flexible display device 100 to a humid environment. In some cases, moisture may reach the conductor 120. Dissimilar metals and alloys have different electrode potentials, and when two or more come into contact in an electrolyte, one metal acts as an anode and the other acts as a cathode. The potential difference between dissimilar metals promotes corrosion of the anode member, which may be the first conductive layer 122 of the multilayer conductor 120 (eg, the Al layer of a Ti/Al/Ti stack). The anode metal melts into electrolyte and accumulates on the cathode metal.

When using the multilayer conductor 120 described above, surfaces exposing both the first conductive layer 122 and the second conductive layer 124 may become the starting point of galvanic corrosion. Accordingly, in some embodiments of the flexible display device 100, at least some of the conductors 120 have a structure in which the outer surface of the first conductive layer 122 is surrounded by the second conductive layer 124, as shown in FIG. 7B. This shape prevents the electrolyte from contacting both the first conductive layer 122 and the second conductive layer 124, thereby minimizing loss of the first conductive layer 122 due to galvanic corrosion.

This multilayer conductor 120 may be manufactured by laminating a material for the first conductive layer 122 (e.g., Al) on the second conductive layer 124 (e.g., Ti). Here, the first conductive layer ( 122) The second conductive layer 124 below may have a larger width. An etch-blocking material is formed on the two layers, and then etched (eg, dry etch, wet etch, etc.) to form conductive wires in a desired wiring shape. After stripping off the etch stop material, a second conductive layer 124 (e.g. Ti) is deposited over the structure (e.g. Ti/Al). The width of the second conductive layer 124 laminated on the first conductive layer 122 is larger than the width of the first conductive layer 122 so as to cover the outer surface of the first conductive layer 122. You can. The following etching and etch stop material removal steps are performed to form multilayer conductors according to the desired conductor layout design. The above-described multilayer conductor formation process is merely illustrative. Accordingly, some processes may be added and/or omitted in the manufacturing of the multilayer conductor.

The trace design of a conductor is an important factor that can affect the electrical/mechanical properties of the conductor. To meet electrical/mechanical requirements, some parts of the conductor may be configured differently than other parts. A structure for controlling bending stress is provided on a portion of the conductor in or near the bending section of the flexible display device 100.

Controlling the bending stress of the insulating layer near the conductor is as important as controlling the deformation of the conductor itself. Various insulating layers, such as buffer layer 126, protective layer 128, gate insulating layer (GI), and interlayer insulating layer (ILD), placed above and/or below conductor 120, may include inorganic materials. Layers made of materials, such as silicon oxide or silicon nitride, are generally more prone to cracking than the metal layers of the conductors. Even when the conductor has sufficient flexibility to withstand bending stress without cracking, cracks occurring in the insulation layer can propagate into the conductor, creating a poor electrical connection.

As a wiring design that reduces bending stress on the conductors, some of the insulating layers above and/or below the conductors 120 may be patterned to minimize cracking. Various insulating layer patterning techniques, such as wet etching and/or dry etching, may be used to create a shape of the insulating layer corresponding to the wiring structure. The omission of insulating layers, especially insulating layers based on inorganic materials around the conductors, not only reduces the chances of cracks occurring, but also eliminates their propagation path. For convenience of explanation, the arrangement of the conductive wire 120 and the insulating layer covering at least a portion of the conductive wire 120 is hereinafter referred to as a “wire trace.”

As mentioned, the design of the conductors and the insulating layer covering them plays an important role in increasing the robustness of the wiring structure. Many factors are involved in the design of the wiring structure, from thickness and width to the unfolding angle of the wiring pieces for each bend direction. In addition, many other factors related to conductor 120 and insulating layer placement are specifically tuned based on the installation and orientation of the wires.

The more the direction in which the wiring structure extends is aligned with the tangent vector of curvature, the greater the deformation of the wiring due to bending stress will be. In other words, if the length of the wire segment parallel to the tangent vector of curvature is reduced, the wire structure will better withstand bending stress. Regardless of the direction in which the wiring structure extends, there is always a portion within the wiring structure that is measured in the direction of bending. However, by applying a strain reduction design to the wiring structure, the length of each successive measurable portion (i.e., piece) aligned parallel to the bending direction can be reduced.

Figure 8 shows several examples of strain-reducing wiring designs.

One or more of the sine-wave, square-wave, sawtooth, wavy, and hatched designs shown in FIG. 8 may be used in the wiring structure. When this strain reduction design is applied, the portion of the wiring aligned in a direction oblique to the tangent vector of curvature is increased. This limits the length of the wire strip extending in a straight line parallel to the direction of bending.

Since cracks within the wiring structure due to bending of the flexible display device typically start at the inorganic insulation layer, it is important that the length of the insulation layer aligned with the tangent vector of curvature is also minimized. Within a single-wire strain reduction design, the width and shape of the conductor as well as the width of the patterned inorganic insulation layer that meets the surface of the conductor must be kept to a minimum.

The strain reduction arrangement design shown in FIG. 8 is merely exemplary, and other arrangement designs may be used to reduce wire fragments parallel to the bending direction in various embodiments of the flexible display device 100. In addition, some wiring structures may adopt a strain reduction arrangement design that is different from other wiring structures in the flexible display device 100, depending on electrical and/or mechanical requirements. For example, the strain reduction layout design used for data signal lines may be different from the strain reduction layout design for power lines.

To further improve robustness, the wiring structure may use a layout design in which the wiring structures are divided and clustered repeatedly at specific intervals. In other words, the wiring structure includes at least two sub-traces to form a wiring resembling a chain of connecting links. The angles at which it divides and converges define the shape of each link, and the shape of each link limits the length of a piece of wire that can be measured in a straight line parallel to the direction of bend.

Referring to FIG. 9A, the conductor 120 includes sub-wiring A and sub-wiring B that are divided and gathered at each joint X. Between the first node extends in the second direction. Subwire B bends in a similar way to subwire A, but in the opposite direction with respect to the tangent vector of curvature. The distance and direction in which subwires are arranged between two adjacent nodes defines the shape and size of the links in the chain as well as the open area surrounded by the subwires. In this example, the shape of the conductor 120 between the first node Together with the additional nodes

Compared to the strain-reducing wiring design without splitting shown in FIG. 8, the strain-reducing wiring design shown in FIG. 9A can provide significant advantages in electrical characteristics. For example, a wiring structure with a split/gathered wiring design has a much lower electrical resistance compared to a wiring structure with a strain reduction design such as the acid wiring of FIG. 8, a sinusoidal wiring, or other single conductor type strain reduction designs. In addition, the auxiliary wiring can function as a spare passage in case one wiring is damaged.

The insulating layer covering the surface of the conductor 120 is also patterned with an arrangement design corresponding to the wiring structure of the conductor 120. At this time, the open area surrounded by sub-wiring A and sub-wiring B does not have an inorganic insulating layer or has a conductive wire (120). ) has a thinner inorganic insulating layer compared to the areas below and/or above the structure. At this time, the length of the insulating layer that can be measured in a straight line parallel to the bending direction may be limited to reduce the occurrence and propagation of cracks.

For strain reduction designs based on multiple subwirings, a variety of additional factors must be considered. The split/join angle and the length of the subwire between two adjacent nodes Should be. In other words, the open area surrounded by the sub-wiring between the two nodes

In the diamond interconnection design illustrated in FIG. 9A, the buffer layer 126 and protection layer 128 covering the conductor 120 have a predetermined margin from the outer structure (i.e., the outer edge) of the conductor 120. It is patterned. Except for the remaining insulating layer covering the conductor 120 with a predetermined margin, there is no insulating layer in the open area FA2 surrounded by sub-wirings A and B. In this way, the arrangement structure of the insulating layer is formed to correspond to the arrangement design of the conductive wire 120. The length of the open area without insulating layer, measured in the direction perpendicular to the direction of bending, is: It is larger than the width of the inorganic insulating layer structure at node X measured in the same direction. In this setup, the open area FA2 surrounded by sub-wires A and B, as well as the area next to node

Referring to FIG. 9A, the area FA1 without an insulating layer prevents the insulating layers of the sub-wiring A and sub-wiring B between the two nodes X(1) and X(2) from extending in a continuous straight line. Likewise, the region FA2 without an insulating layer prevents the insulating layer between the two nodes X(1) and X(2) from extending into a continuous straight line. Accordingly, the length of each insulating layer array piece aligned with respect to the tangent vector of curvature is minimized. Further reducing the length of each insulating layer array piece aligned to the tangent vector of curvature is achieved by reducing the width of the conductor 120 and the margin of the insulating layer beyond the edges of the conductor 120 .

Since the reduction in the conductor width makes the electrical resistance very large compared to the specific application within the flexible display device 100, the amount of reduction in the width of the conductor 120 in the single conductor strain reduction wiring design described in FIG. 8 is limited. However, in the divided/gathered wiring design of FIG. 9A, the width of the conductors 120 and the insulating layer structure can be reduced while satisfying the required electrical characteristics.

A larger split/join angle with respect to the bending direction of the subwiring greatly reduces the length of the conductor 120 and the insulating layer structure extending along the tangent vector of curvature. Therefore, by selectively increasing the splitting/gathering angle of the sub-wiring in the high bending stress region, the possibility of cracks occurring in the wiring structure is lowered.

The split angle of the subwire can affect the distance between two adjacent nodes The distance between nodes X need not be uniform across the entire wire. The spacing at which wires are divided and gathered can vary within a wire based on the degree of bending stress applied to a particular portion of the wire structure. The distance between nodes Conversely, towards areas where smaller bending stresses are applied, the distance between nodes X can gradually increase.

Even with a strain-reducing wiring design, unavoidable bending stress remains at some points (i.e., stress points) of the wiring. The location of the stress point is highly dependent on the bending direction and shape of the wire. Accordingly, for a given bending direction, the wiring structure can be designed so that the remaining bending stress is concentrated in the desired portion. Knowing the stress points within the wiring, crack-stopping regions can be provided at those stress points so that the wiring structure can withstand bending stress longer.

Referring back to Figure 9A, when a wiring structure with a diamond wiring design is bent in the bending direction, the bending stress tends to be concentrated at the angled vertices (i.e., the vertices of each diamond-shaped link), which are referred to as stress point A and stress. It is marked as point B. As such, cracks are likely to start and expand between the inside and outside of the wiring structure. For example, at stress point A, splitting may begin at inner wire 120 (IN) and progress to outer wire 120 (OUT). Similarly, at stress point B, splitting may begin on the outer wire 120 (OUT) and progress to the inner wire 120 (IN).

Accordingly, the width of the conductor 120 at stress point A may be selectively increased to serve as a crack prevention region. As illustrated in FIG. 9A, the width (WA, WB) of conductor 120 at stress points A and B, measured perpendicular to the bending direction, is the width (W) of conductor 120 at the portion between stress points A and B. It can be bigger than The additional width at the stress point can cause the conductor 120 to hold longer before the crack at the stress point grows larger and is completely severed.

The length of continuous parts of the insulating layer structure aligned in the direction of bending should be kept to a minimum. Increasing the width of the conductor 120 at stress points A and B inevitably increases the width of each insulating layer structure, which makes the insulating layer structure aligned parallel to the bending direction elongate.

Accordingly, in some embodiments, the width of conductor 120, measured perpendicular to the tangent vector of curvature at stress point A, is between about 2.5 micrometers (μm) and about 8 μm, preferably between about 3.5 μm and about 3.5 μm. It may be between 6 ㎛, more preferably between about 4.5 ㎛ and about 8.5 ㎛, and even more preferably about 4.0 ㎛. The width of conductor 120 at stress point B should be maintained similar to the width of conductor 120 at stress point A. As such, the width of conductor 120 at stress point B may be between about 2.5 μm and about 8 μm, preferably between about 3.5 μm and about 6 μm, and more preferably between about 4.5 μm and about 8.5 μm. , more preferably about 4.0 ㎛. Because sub-wiring A and sub-wiring B come together at stress point B, the width of conductor 120 at stress point B may be longer than the width at stress point A.

In some embodiments, one of the inner wires 120 (IN) and the outer wires 120 (OUT) may not be bent as sharply as the other wires at stress point A to minimize the chance that splitting will occur on both sides. In the embodiment illustrated in FIG. 9A, the inner wire 120(IN) is bent more sharply than the outer wire 120(OUT) at stress point A. However, in other embodiments, the outer wire 120(OUT) may be bent more sharply than the inner wire 120(IN) at stress point A. In both cases in the depiction of Figure 9A, the less sharply curved wires may be more rounded than straight, such as the outer wire 120(OUT). And, at stress point A, both the inner wire 120 (IN) and the outer wire 120 (OUT) can be rounded.

The wiring structure can be divided into a larger number of sub-wires, resulting in continuous links arranged like a grid. As an example, the wiring structure may be configured like a spiderweb of diamond wiring, as shown in FIG. 9B. This wiring design is particularly useful when the wiring carries a common signal to multiple points, or when the wiring requires very low electrical resistance. For example, in the flexible display device 100, the VSS line and the VDD line are, in particular, the lines When they are arranged to cross a bending section, they can have the grid wiring structure. Neither the number nor the shape of sub-wiring in the grid wiring structure is limited by the example of FIG. 9B.

In some embodiments, the width of the grid may decrease or increase between both ends within the flexible display device 100. Additionally, the grid interconnection structure shown in FIG. 9B may be converged again to form the diamond interconnection of FIG. 9A or to form a strain-reducing interconnection without division. In some cases, the size of each diamond-interconnect in a grid-like interconnect structure may be larger than the size of each diamond interconnect in a diamond interconnect chain to reduce resistance.

Because of the portion bending away from the bending direction, a wiring structure with a strain-reducing wiring design may require a larger routing area within the flexible display device 100. In an embodiment in which the non-display area at the edge of the flexible display device 100 is bent, increasing the routing area to accommodate the wiring structure increases the size of the non-display area to be hidden.

Therefore, a wiring structure using a strain reduction design must be arranged with tight spacing between adjacent wirings. For example, two adjacent interconnections having a strain reduction design may each include a non-linear section with a convex side and a concave side. The two adjacent interconnections may be arranged such that the convex side of the non-linear section of the first interconnection structure is located next to the concave side of the non-linear section of the second interconnection structure. Because the gap between the two interconnections is limited by the shape and size of the interconnection structure, the non-linear section in the strain reduction design of the first interconnection structure may be larger than the nonlinear section in the strain reduction design of the second interconnection structure. Of course, one of the first interconnection structure and the second interconnection structure may have a different strain reduction design to better accommodate the non-linear section of the other interconnection structure.

For example, two or more wiring structures arranged side by side may each have a strain reduction design, and each wiring structure may have a plurality of indented sections and a plurality of distended sections. In this case, the expansion zone of one wiring structure may be arranged so that it lies next to the shrinking region of the adjacent wiring structure.

10 shows an example arrangement of several interconnect structures with a diamond interconnect design.

The division of sub-wiring creates an expansion zone and widens the layout of the wiring structure, while the gathering of sub-wiring creates a contraction zone and narrows the layout of the wiring structure. Therefore, from a layout perspective, the contraction zone of the wiring structure is at node

As shown in FIG. 10, nodes X of the first wiring structure and nodes X of the second wiring structure are arranged in staggered positions. In this arrangement, the diamond-shaped vertex in the expansion zone of the first interconnection structure lies next to the node X in the contraction zone of the adjacent interconnection structure. The staggered arrangement of these wiring structures can help lower electrical noise due to the proximity of the wiring, thus reducing the distance between the wiring. Tight spacing between wires can be achieved by locating the expansion region of one wiring structure close to the contraction region of an adjacent wiring structure. For example, a vertex in a wide portion of an interconnection structure may lie in an open area FA1, which is created by the length and split/join angle of subinterconnections in an adjacent interconnection structure. This staggered arrangement maintains a certain minimum distance between the wires while reducing the total space occupied by the wire structures.

11A and 11B show a schematic cross-sectional view of an exemplary wiring structure used in a flexible display device according to an embodiment of the present specification.

As mentioned, cracks mainly initiate from the inorganic insulating layer. Therefore, by selectively removing the inorganic insulating layer from areas where cracks are prone to occur, the propagation of cracks can be suppressed. To this end, a pile of insulating layers including one or more inorganic insulating layers and/or inorganic layers may be selectively etched in various portions of the flexible display device 100.

For example, the insulating layer beneath the conductive wire 120 may be etched. The insulating layer under the conductive wire 120 may be a buffer layer 126, which may include one or more inorganic layers. The buffer layer 126 may be formed of one or more silicon nitride (SiNx) layers and/or silicon oxide (SiO2) layers. As one configuration, the buffer layer 126 may be formed by alternately stacking SiNx layers and SiO2 layers. The buffer layer 126 is disposed above the base layer 106 and below the TFT.

To facilitate easier bending of the flexible display device 100, a portion of the buffer layer 126 may be etched at the curved portion. Accordingly, the buffer layer 126 in the substantially flat portion may be thicker than the buffer layer 126 in the curved portion. When the buffer layer 126 is formed of a plurality of sub-layers, the buffer layer 126 in a substantially flat portion may include one or more additional sub-layers compared to the buffer layer in the curved portion.

For example, buffer layer 126 in a substantially flat portion may include multiple layers of SiNx and SiO2, and buffer layer 126 in a curved portion may include one layer of SiNx and SiO2. It is also possible to have only one layer of SiNx or SiO2 in one part of the curved portion. As one configuration example, each layer in the buffer layer 126 may have a thickness of approximately 1000 ÅA. As such, the thickness of the buffer layer 126 at the curved portion may range from about 100 ÅA to about 2000 ÅA.

In a substantially flat portion of the flexible display device 100, an additional inorganic layer may be provided directly beneath the semiconductor layer of the TFT, which may be referred to as an active buffer. In some embodiments, the inorganic layer closest to the semiconductor layer of the TFT may be thicker than the individual inorganic layers within buffer layer 126.

The buffer layer 126 within the curved section may be further etched to expose the base layer 106 while leaving the buffer layer 126 under the conductive wire 120 intact. In other words, a recessed area and a protruding area are provided in the curved portion. The protruding areas include the buffer layer 126 disposed on the base layer 106, while the recessed areas have the base layer 106 exposed without the buffer layer 126 disposed thereon.

In the example configuration shown in FIG. 11A, conductor 120 is located on the raised area and protective layer 128 is located over conductor 120 on the raised area. Even if the protective layer 128 is not deposited over the depressed area, the protective layer 128 can be removed from the depressed area by dry or wet etching. As such, the recessed areas may be substantially free of protective layer 128. When etching the protective layer 128 from the recessed areas, a portion of the base layer 106 may also be etched away. Accordingly, the thickness of base layer 106 in recessed areas may be less than the thickness of base layer 106 elsewhere. When the buffer layer 126 is etched as shown in FIG. 11A, propagation of cracks from one part of the buffer layer 126 to another part is prevented by the space of the recessed area. Similarly, crack propagation by the protective layer 128 is also inhibited by the spacing of the recessed areas. Accordingly, damage to the conductor 120 due to crack propagation is reduced.

In another configuration shown in FIG. 11B, the recessed area includes a base layer 106 etched to a certain depth, and conductors 120 are deposited on the base layer 106 of the recessed area. In this setup, portions of conductors 120 are disposed within base layer 106. Additionally, a portion of the conductive wire 120 is deposited on a portion of the buffer layer 126 provided in the protruding area. A protective layer 128 may be deposited over conductor 120 and etched away to expose conductor 120 within the recessed area.

Accordingly, protective layer 128 remains on conductor 120 located over the protruding area. In this configuration, the protective layer 128 remaining on the buffer layer 126 can inhibit galvanic corrosion by covering the cross-section of the side of the multilayer conductor 120. Although cracks generated in the buffer layer 126 may penetrate into the conductors 120 located on the walls of the voids in the buffer layer 126, it is difficult to reach the conductors 120 located within the base layer 106.

When the conductor 120 has the multilayer structure described above, the portion of the conductor 120 in the recessed area does not need to be covered with the protective layer 128. If the protective layer 128 is removed from the surface of the conductor 120 in the recessed areas, crack propagation from the protective layer 128 can be prevented. And, generally, galvanic corrosion starts at the edge of the conductor 120 on the buffer layer 126, so if the conductor 120 on the buffer layer 126 and the conductor 120 on the base layer 106 are sufficiently far away from each other, A protective layer 128 covering the edge of the conductive wire 120 above the buffer layer 126 may not be necessary. The configuration shown in FIGS. 11A and 11B can be used together with the strain reduction wiring patterns of FIGS. 8, 9A, and 9B for the wiring structure in the curved section. In addition to the curved section, in some embodiments the patterned insulating layer may also be provided between the COF attachment area and the routing area between the curved section and in the routing area between the display area and the curved section.

And, the above-described patterned insulating layer may be provided in the display area. However, removing the inorganic insulating layer near the TFT may affect the electrical properties of the component. For example, removal of a portion of the buffer layer 126 may result in an unwanted shift in the threshold voltage of the TFT. To maintain the stability of the TFT, an additional shield metal may be formed under the semiconductor layer of the TFT. The capping metal layer may be below the buffer layer 126 or between the inorganic layers of the buffer layer 126. In some embodiments, the shield metal layer may be electrically connected to the source electrode or gate electrode of the TFT.

In addition to patterning the insulating layer in various places of the flexible display device 100, other structural elements may be removed or simplified in some areas of the flexible display device 100 for bending. For example, the touch sensor layer 112, the polarization layer 110, etc. may be absent in the curved section. Removing or simplifying these elements will create multiple non-planar surfaces over which the wiring structure may pass.

When the interconnection structure is on such a non-flat surface, some portions of the interconnection structure may lie in a different plane than other portions. Because the parts lie in different planes, the amount and direction of bending stress and resulting strain may vary within the wiring structure. To accommodate this difference, the strain reduction design of the wiring structure may include a modified layout design for the wiring structure on a non-flat surface.

FIG. 12A is an enlarged cross-sectional view showing an exemplary backplane of the flexible display device 100.

In the display device, a number of insulating layers were removed from the curved portion to ensure reliable bending.

A plurality of organic and inorganic layers may be formed between the base layer 106 and the organic light emitting device layer 150. In this example, SiNx and SiO2 layers may be alternately stacked on base layer 106 to serve as buffer layer 126. The semiconductor layer 151 of the TFT may be sandwiched between the active buffer layer 127 and the gate insulating layer 152 made of a SiO2 layer. The gate 152 of the TFT is disposed on the gate insulating layer 152, and a metal layer with a multilayer structure (the same metal as the source/drain of the TFT) is placed between the interlayer insulating layer 154 and the protective layer 128. Here, the interlayer insulating layer 154 may be formed by stacking SiNx and SiO2, and the protective layer 128 (passivation layer) may be formed of SiNx. Afterwards, a planarization layer is placed over the protective layer 128 and the anode of the OLED is placed thereon.

As mentioned above, the use of strain reduction designs is not limited to those portions of the wiring structure that are in curved portions. Additionally, the strain reduction design can be applied to the wiring structure in the routing area outside the bend section. The use of strain-reducing designs for the wiring structures in these routing areas can result in improved protection against flexural stress of the wiring structures.

However, multiple organic and/or inorganic layers between the base layer 106 and the organic light emitting device layer 150 in the routing area may be removed to facilitate bending of the flexible display device 100. These organic and/or inorganic layers may be included in the interlayer insulating layer 154, gate insulating layer 152, buffer layers 126 and 127, protective layer 128, polarizing layer, etc. of the flexible display device 100. It may not be present in curved areas. Some of these layers can be removed in specific areas by an etching process.

As an example, a plurality of insulating layers on the buffer layer 126 may be removed through the first etching process (EB1). The first etching process (EB1) is followed by a second etching process (EB2) in which the active buffer 127 and a portion of the buffer layer 126 (eg, a stack of the SiNx layer and the SiO2 layer) are removed. This etching process creates multiple step areas as shown in FIG. 12A. The stepped area has one or more vertically inclined surfaces and one horizontally flat surface, on which conductive wires are disposed. Conductors lying on vertically inclined surfaces and horizontally flat surfaces may have a number of bending points, such as the areas between high and low steps provided by the insulating layer.

When the flexible display device 100 is bent in the bending direction, the conductive wire experiences greater deformation in and around the step area. In various studies and experiments, it has been pointed out that the possibility of splitting is particularly high in wiring that crosses the step area between the EB1 region and the EB2 region. Accordingly, in some embodiments the strain relief design has reinforcing portions in and near the step area between the high and low steps created by the insulating layer.

In the example shown in Figure 12b, the wiring structure has simple straight wiring at both ends. However, a portion of the conductor 120 crossing the bend sections EB1 and EB2 is strengthened with the modified wiring design. In the modified part, the conductor 120 has a wider width with an additional width WR, to ensure protection of the conductor 120 even against cracks originating from the insulating layer near the EB1 and EB2 regions. The distance DR provided in the modified interconnect design depends on the distance between the first height plane (e.g. height of region EB1) and the second height plane (e.g. height of region EB2) as well as the thickness of the insulating layer that is etched during the etching process. do.

The strain reduction design of the wiring structure to which the modified portion is applied is not limited to the design illustrated in FIG. 12B. Various embodiments of strain reduction designs may include modified interconnect designs for specific portions of the interconnects corresponding to stepped areas of different heights.

Although not always the case, the routing area adjacent to the curved section may be a substantially flat portion of the flexible display device 100. In this case, the EB1 and EB2 regions may be located at the beginning or just outside the bend section in the bend section, and the wiring structure may have a reinforced portion.

The increased width WR of the strengthened conductor 120 serves this purpose at the beginning and end of the bend section and its vicinity where the curvature is relatively small. The wider width WR of the wiring structure and the length to which the modified wiring portion is applied can increase the length of the wiring aligned parallel to the bending direction. This will make the wiring structure more rigid to withstand bending stresses in larger bend radius areas.

For this reason, the distance DR over which the reinforced section is located should be limited so that the reinforced conductor section does not extend too far into the bend section. Accordingly, the distance DR of the reinforced conductor portion may be limited so as not to extend beyond a bending section in which the wiring of the reinforced conductor portion is bent more than a predetermined critical bending angle. As an example, the reinforcing conductor portion may not extend beyond a 30° bend from the tangent plane. The critical bending angle may be less than 20°, and may be less than 10° or 7°.

The wiring structure provided with a reinforced portion in the step area may extend across the curved section and connect to pads or other components of the COF. In this example, an additional step region (similar to EB1 and EB2) may be present at or near the opposite end of the bend section. The conductor at or near this bend point may be strengthened at the opposite end in a manner similar to a modified portion of the wiring structure, as shown in FIG. 12B. If desired, the conductor reinforcement portion at or near the step area at the opposite end of the bend section may have a different shape than that illustrated in FIG. 12B.

13A to 13C are diagrams showing a protective coating layer used in a flexible display device.

If there are no layers in the curved portion of the flexible display device 100, a protective layer may be needed for the conductors, especially the wiring structures in the curved section. Additionally, because the inorganic insulating layers may be etched from the curved portion of the flexible display device 100, the conductors in the curved portion may be vulnerable to moisture and other foreign substances. In particular, during the manufacturing process of the flexible display device 100, various pads and conductors for testing components may be chamfered, which may leave conductors extending to the hollow edges of the flexible display device 100. . These conductors can be easily corroded by moisture, and the corrosion can extend to nearby conductors. Accordingly, a protective coating layer, which may be referred to as a “micro-coating layer”, may be provided on the conductor and/or wiring structure in the bent portion.

The protective coating layer 132 may be coated on the curved section with a thickness determined to adjust the neutral plane of the flexible display device 100 at the curved portion. More specifically, the thickness added to the protective coating layer 132 at the curved portion may move the plane of the conductor and/or wiring structure closer to the neutral plane.

In some embodiments, the thickness of the micro coating layer 132, measured from the surface of the base layer 106 in the area between the barrier film 104 and the printed circuit board 134, is the thickness of the barrier film 104 (base layer 132). layer 106 to the top surface of barrier film 104).

The protective coating layer 132 must have sufficient flexibility to be used in the curved portion of the flexible display device 100. Additionally, the protective coating layer 132 is preferably a material that cures with low energy within a limited time so that the components underneath it are not damaged during the curing process. The protective coating layer 132 may be formed of an acrylic resin that is curable by light (eg, UV light, visible light, etc.). In order to suppress the penetration of moisture through the protective coating layer 132, one or more moisture absorbing materials (getter) may be mixed into the protective coating layer 132.

Various resin application methods, for example, slit coating, jetting, etc., may be used to apply the protective coating layer 132 to a designated surface. As another example, protective coating layer 132 may be applied using a spray valve. The application rate from the spray valve may be adjusted during the coating process for precise control of the thickness and spread of the protective coating layer 132. Additionally, the number of injection valves for applying the protective coating layer 132 is not limited and may be varied to adjust the diffusion amount and application time before the protective coating layer 132 is cured.

Figure 13A shows an example configuration of protective coating layer 132. As mentioned, the protective coating layer 132 may be coated on the area between the barrier film 104 and the printed circuit board 134 attached to the non-display area. However, depending on the adhesive properties of the protective coating layer 132 and the magnitude of the stress, the protective coating layer 132 may separate from the barrier film 104 and/or the printed circuit board 134. The open space between the protective coating layer 132 and the barrier film 104 or the printed circuit board 134 can be a defect area through which moisture can penetrate.

Accordingly, in some embodiments, the protective coating layer 132 may partially overlie the barrier film 104, as shown in FIGS. 13A-13C. That is, a portion of the upper corner surface of the barrier film 104 may be covered with the protective coating layer 132. The area in contact with the surface of the barrier film 104 prevents the protective coating layer 132 from separating from the barrier film 104 due to bending stress. The improved sealing provided by the protective coating layer 132 at the edges of the barrier film 104 may reduce corrosion of the conductors at bends. Similarly, the protective coating layer 132 may be over-applied over at least a portion of the printed circuit board 134 to improve edge sealing of the printed circuit board 134.

13B and 13C, the width of the area covered with the protective coating layer 132 on the barrier film 104 is denoted as “W1”, and the width of the area covered with the protective coating layer 132 on the printed circuit board 134 is denoted as “W1”. is indicated as “W2”. The size (area) of the protective coating layer 132 covering the barrier film 104 and the printed circuit board 134 is not particularly limited and may vary depending on the adhesiveness of the protective coating layer 132.

As shown in FIG. 13B, the flexible display device 100 may include a portion where the protective coating layer 132 on the barrier film 104 is spaced apart from the edge of the polarizing layer 110. However, in some embodiments, the flexible display device 100 may include a portion where the protective coating layer 132 on the barrier film 104 contacts the polarizing layer 110, as shown in FIG. 13C.

The spreading power of the applied protective coating layer 132 is determined not only by viscosity but also by the surface energy where the protective coating layer 132 is applied. The protective coating layer 132 overflowing onto the barrier film 104 may reach the polarizing layer 110. Protective coating layer 132 in contact with the sidewall of polarizing layer 110 may help secure polarizing layer 110 in place. However, the protective coating layer 132 that reaches the side of the polarization layer 110 may rise above the side wall of the polarization layer 110. This sidewall wetting of the protective coating layer 132 may create uneven edges on the surface of the polarizing layer 110, which may cause various problems when placing another layer thereon. Accordingly, the amount of protective coating layer 132 applied on a particular surface can be adjusted to control its width. Additionally, the protective coating layer 132 may be applied so that only some of the selected areas of the polarizing layer 110 are in contact with the protective coating layer 132.

In one configuration, the protective coating layer 132 may contact the polarizing layer 110 at two opposing vertices (“POL_CT” in FIG. 13A), but between the two vertices the protective coating layer 132 may contact the polarizing layer ( 110) does not reach the edge. The protective coating layer 132 between the two opposing peaks (POL_CT) covers only a portion of the barrier film 104. After the bending process, the portion of the flexible display device 100 in which the protective coating layer 132 is spaced apart from the polarizing layer 110 may be configured as shown in FIG. 14A. In a region where the protective coating layer 132 is configured to contact the polarization layer 110, the flexible display device 100 may be configured as shown in FIG. 14B.

Figure 15 is a diagram showing part of the manufacturing process of a protective coating layer used in a flexible display device.

The protective coating layer 132 shown in FIGS. 13 and 14 had a structure in which a specific resin was applied to the curved portion of the base layer 106. In the above structure, when the protective coating layer touches the side wall of the polarizing layer 110, a wetting phenomenon due to surface tension may occur, so the protective coating layer is applied in a shape that slightly covers the barrier film 104. The above structure was easy to secure coating surface uniformity.

On the other hand, the flexible display device shown in FIG. 15 may be implemented in a structure in which the polarizing layer 110 is stacked on the base layer 106 (i.e., on top of the organic light emitting device) without a barrier film. These structures include the use of a polarizing layer with high moisture resistance (e.g., water vapor transmission rate (WVTR) of approximately 1.0x10 ^-3 to 1.0x10 ^-4 g/m ² 24hr), application of a new encapsulation structure, and/or thickness This is in accordance with the development trend of omitting barrier films for reduction.

15 , when the protective coating layer 132 is applied as before in a structure in which the barrier film between the base layer 106 and the polarizing layer 110 is excluded, the polarizing layer 110 and/or the upper surface of the polarizing layer are protected. Thickness unevenness (132_A, 132_B) may occur on the side wall of the protective film (110_PF) due to the surface tension effect. The relatively thicker portion (132_A) of the coating layer 132 may cause problems such as clumping when bent as shown in Figures 14a or 14b. Additionally, the protruding portion (burr, 132_B) remaining after the protective film 110_PF is removed may adversely affect the process of laminating a specific layer (eg, cover glass) on the upper surface of the polarizing layer 110. Accordingly, the inventors of the present invention derived the optimal conditions for the protective coating layer to be applied to the curved portion of the flexible display device.

Figure 16 is a diagram showing a protective coating layer used in a flexible display device according to an embodiment of the present specification.

The flexible display device may include a base layer 106, a polarizing layer 110, a protective coating layer 132, a printed circuit board, etc. If necessary, the flexible display device may further include a support layer 108, a support member (eg, mandrel), etc. When the base layer 106 is made of plastic, it may be referred to as a plastic film or a plastic substrate. For example, the base layer 106 may be in the form of a film containing one selected from the group consisting of polyimide-based polymer, polyester-based polymer, silicone-based polymer, acrylic polymer, polyolefin-based polymer, and copolymers thereof. Among these materials, polyimide is widely used as a plastic substrate because it can be applied to high-temperature processes and can be coated.

The base layer 106 of the flexible display device may include a first part 101 and a second part 102, as shown in FIGS. 3A and 4. 3A and 4 illustrate that the second part 102 extends outward from the first part 101, but the spirit of the present specification is not limited thereto. The first part 101 is a substantially flat part where an organic light emitting device, a polarizing layer 110, etc. are disposed. At this time, the organic light emitting device, the polarizing layer 110, etc. are disposed on the first surface (upper surface) of the first part 101. The organic light-emitting device may have a first electrode, an organic light-emitting layer, and a second electrode arranged sequentially. That is, the organic light-emitting device may be composed of a first electrode electrically connected to a driving thin-film transistor (Driving TFT), an organic light-emitting layer located on the first electrode, and a second electrode located on the organic light-emitting layer. An encapsulation layer may be placed on the organic light emitting device, and a polarizing layer 110 may be positioned on the encapsulation layer without a barrier film. There is an adhesive layer 113 on the polarizing layer 110, and a cover layer (eg, cover glass) may be placed on it.

Meanwhile, the second part 102 is an outer part of the first part, and is a part (bending section) bent toward the second surface (lower surface, opposite to the first surface) of the first part 101. ) has. At this time, the second part 102 may be provided to start (extend) from the outside of the first part 101. The second part 102 may include a curved section 102b that is bent at a predetermined curvature and a flat section that is not bent (a section supported by the support layer 108).

The protective coating layer 132 covers at least a portion of the first surface (upper surface) of the second portion 102. The protective coating layer 132 has a structure that ensures thickness uniformity and adhesion even when applied to a display device without a barrier film on the encapsulation layer. As mentioned above, in a flexible display device without a barrier film, research was needed to determine what standard the protective coating layer should be applied to prevent problems during bending. Accordingly, the inventors of the present specification analyzed the force applied to each part of the protective coating layer, the correlation between the thickness of each part and the defect rate, and derived the optimal protective coating layer application conditions. Figure 17 shows experimental data for this.

FIG. 17 shows the product defect rate according to the difference between the height (H+α) of the portion of the protective coating layer 132 adjacent to the polarizing layer 110 and the height (H) of the substantially flat portion (eg, curved section 102b). At this time, H was 100 μm.

If the height (or thickness) difference is -20 μm or less, that is, if the height (H+α) of the portion adjacent to the polarizing layer 110 is 20 μm or more lower than the height (H) of the substantially flat portion, all products A defect occurred. The above defects include phenomena such as abnormal curved surface shape, insufficient adhesion, and resin clumping. In addition, when the height difference is -20 to 0 μm, that is, when the height (H+α) of the portion adjacent to the polarization layer 110 is 0 to 20 μm lower than the height (H) of the substantially flat portion, the entire product Among them, defects occurred in 60% of cases. Accordingly, if the height (H+α) of the portion adjacent to the polarization layer 110 is lower than the height (H) of the substantially flat portion, the defect rate is analyzed to be very high.

On the other hand, when the height difference is 0 to +20 μm, that is, when the height (H+α) of the portion adjacent to the polarization layer 110 is 0 to 20 μm higher than the height (H) of the substantially flat portion, the entire Defects occurred in 33% of products. In addition, when the height difference is +60 to +80 μm, that is, when the height (H+α) of the portion adjacent to the polarization layer 110 is 60 to 80 μm higher than the height (H) of the substantially flat portion, the entire Defects occurred in 33% of products, and when the height difference was more than +80 μm, defects occurred in all products.

However, when the difference between the height (H+α) of the portion adjacent to the polarizing layer 110 and the height (H) of the substantially flat portion (e.g., curved section 102b) is +20 to +40 μm and +40 to + If it is 60 μm, that is, if the height (H+α) of the portion adjacent to the polarizing layer 110 is 20 to 40 μm higher than the height (H) of the substantially flat portion, or if it is 40 to 60 μm higher, the defect is It didn't happen.

Considering these experimental results, ① the height (H+α) of the portion adjacent to the polarization layer 110 must be greater than the height (H) of the substantially flat portion, and ② (if H is 100 μm) the height It can be seen that the difference is preferably +20 to +60 μm.

Accordingly, the flexible display device according to an embodiment of the present specification includes a first portion 101 in which an organic light emitting element is disposed on a first surface; a base layer (106) made of a flexible substrate including a second portion (102) outside the first portion, the second portion (102) having a curved section (102b) bent toward a second side opposite the first side; and a protective coating layer 132 covering at least a portion of the second portion 102. At this time, a polarizing layer 110 is positioned on the organic light emitting device of the first portion without a barrier film, and the protective coating layer 132 is laminated thicker in the portion adjacent to the polarizing layer 110 than in other portions. . That is, H+α > H.

Here, the portion adjacent to the polarization layer 110 is a portion between the side surface and the curved section of the polarization layer 110, and the other portion may be a portion to which the protective coating layer 132 is applied in a substantially flat manner. there is. In other words, it may be advantageous in process management for the protective coating layer 132 to be applied to all parts with a uniform thickness (H), but the part that faces the polarizing layer 110 should be applied to a certain degree thicker than H. It is more helpful in reducing product defects caused by bending.

For example, as shown in FIG. 16, the portion adjacent to the polarizing layer, that is, the portion where the protective coating layer 132 is applied thicker, is between the side of the polarizing layer 110 and the curved section, and is located between the upper portion of the support layer 108. It may be part of it. In addition, the other part, that is, the part where the protective coating layer 132 is uniformly applied at a specific height (H), may be other parts including the bent section 102b. At this time, the height (thickness) H may be the average height (thickness) or the maximum height (thickness) of the portion excluding the adjacent portion of the polarization layer. As an example, H may be 100 μm (±5 μm). Additionally, H+α may be the average height (thickness) or maximum height (thickness) of adjacent parts.

The thickness (H+α) of the thicker applied portion (the portion adjacent to the polarizing layer) may be 20% to 60% thicker than the thickness (H) of the uniformly applied portion. For example, if the thickness of the protective coating layer 132 applied to the uniformly applied portion (the other portion) is substantially 100 μm, the thickness of the protective coating layer applied to the portion adjacent to the polarizing layer is equal to the thickness of the protective coating layer applied to the other portion. It may be 20 to 60 μm thicker compared to the thickness of the protective coating layer.

Meanwhile, the maximum thickness of the protective coating layer 132 is preferably smaller than the thickness of the polarizing layer 110. This is to prevent insufficient adhesion between the polarizing layer and its upper layer due to burrs of the protective coating layer on the side walls of the polarizing layer.

A printed circuit board may be connected to the second portion 102 on the right outside of the protective coating layer 132. Components related to the operation of the organic light emitting device, such as a driver IC chip, may be mounted on the printed circuit board. These printed circuit boards may be referred to as COF (chip on film). Meanwhile, a driver IC chip may be located on the outer base layer 106 of the protective coating layer in the second portion. That is, the driving circuit chip may be formed directly on the base layer 106. A conductive wire connecting the driving circuit chip and the organic light emitting device is disposed in the second portion, and the protective coating layer covers the conductive wire.

Although embodiments of the present specification have been described in detail with reference to the attached drawings, the present specification is not necessarily limited to these embodiments, and various modifications may be made without departing from the technical spirit thereof. Accordingly, the embodiments disclosed in this specification are not intended to limit the technical idea of the present invention, but rather to explain it, and the scope of the technical idea of the present invention is not limited by these embodiments. Each feature of the various embodiments of the present invention can be partially or entirely combined or combined with each other, and can be technically linked and driven in various ways by those skilled in the art, and each embodiment can be performed independently of each other or together in a related relationship. It may be implemented. The scope of protection of the present invention should be interpreted in accordance with the claims below, and all technical ideas within the equivalent scope should be construed as being included in the scope of rights of the present invention.

Claims (10)

a first portion in which an organic light emitting element is disposed on the first side, and
a base layer made of a flexible substrate including a second portion outside the first portion, the base layer having a curved section bent toward a second side opposite the first side; and
It includes a protective coating layer covering at least a portion of the second portion,
A polarizing layer is positioned on the organic light emitting device of the first portion,
The protective coating layer is laminated to a uniform thickness in the curved section and becomes thicker as it approaches the polarizing layer from the outside of the curved section to the side of the polarizing layer. According to claim 1,
The polarizing layer is a flexible display device with a higher moisture resistance than a polarizing layer included in a flexible display device having a barrier film on the organic light emitting device. According to clause 2,
The polarizing layer is a flexible display device with a water vapor transmission rate (WVTR) of 1.0x10 ^-3 to 1.0x10 ^-4 g/m ² 24hr. According to claim 1,
A flexible display device wherein the upper surface of the protective coating is inclined at a portion adjacent to the polarization layer and is flat at other portions. According to clause 4,
The portion adjacent to the polarizing layer is a portion of the upper portion of the support layer attached to the second side of the base layer,
The other portion is an upper portion of the curved section of the flexible display device. According to clause 4,
The thickness of the protective coating layer applied to the portion adjacent to the polarizing layer is,
A flexible display device that is 20% to 60% thicker than the thickness of the protective coating layer applied to the other parts. According to clause 4,
The thickness of the protective coating layer applied to the other portion is substantially 100 μm,
A flexible display device wherein the thickness of the protective coating layer applied to the portion adjacent to the polarizing layer is 20 to 60 μm thicker than the thickness of the protective coating layer applied to the other portion. According to claim 1,
A flexible display device wherein the maximum thickness of the protective coating layer is smaller than the thickness of the polarizing layer. According to claim 1,
A flexible display device where a driver IC chip is located outside the protective coating layer in the second portion. According to clause 9,
A flexible display device wherein a conductive wire connecting the driving circuit chip and the organic light emitting device is disposed in the second portion, and the protective coating layer covers the conductive wire.

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