KR20220090183A - Flexible Display Appratus - Google Patents

Abstract

The present invention relates to a flexible display device. In order to solve a problem in which peeling occurs between layers of a display panel due to stress generated when the flexible display device is folded around a virtual folding axis, a reverse tapered shape is used. Although the spacer is provided, the tape having a reverse tapered shape is formed in both the display area and the non-display area, and has an effect of preventing peeling by selectively forming the tape in the non-folding area where stress does not occur.

Description

Flexible Display Appratus

The present application relates to a flexible display device that can be folded or bent. In particular, when the display panel is folded or bent, cracks occur between a plurality of layers constituting the display panel, thereby improving the problem of delamination between layers deposited on the substrate. It relates to a flexible light emitting display device comprising:

Among the display devices, the electroluminescent display device is a self-luminous type, has excellent viewing angle, contrast ratio, etc., does not require a separate backlight, can be lightweight and thin, and can be driven with little power. In particular, among the electroluminescent display devices, the organic light emitting display device can be driven with a low DC voltage, has a fast response speed, and has advantages of low manufacturing cost.

An electroluminescent display device includes a plurality of electroluminescent elements. Each electroluminescent element constitutes a light emitting diode. The light emitting diode includes an anode electrode, a cathode electrode, and a light emitting layer formed therebetween. When a high potential voltage is applied to the anode electrode and a low potential voltage is applied to the cathode electrode, holes in the anode electrode and electrons in the cathode electrode move to the emission layer, respectively. Then, the electrons and holes that have moved, respectively, combine in the light emitting layer to form excitons, and light energy is generated from these excitons.

In the electroluminescent display device, each pixel is divided by a bank, and an image is displayed by electrically controlling the amount of light generated from a light emitting layer formed in each pixel.

The electroluminescent display device can be implemented as an ultra-thin device, and has the advantage of maximizing the flexibility characteristic of organic materials. Accordingly, it is easy to develop a flexible display device in which the display panel can be freely bent and unfolded. However, even if the flexibility is excellent, if the bending and stretching operation is repeated repeatedly, cracking or breakage may occur due to the bending stress. In particular, cracks are generated in each of the layers constituting the flexible electroluminescent display by bending stress and the cracks propagate laterally, resulting in a defect that the layers are peeled from each other. In particular, an encapsulation layer that protects the electroluminescent display device from an external moisture environment is peeled off from the light emitting device, resulting in a problem in that the light emitting device is deteriorated from moisture.

An object of the present application is to provide a flexible electroluminescent display device having a structure in which cracking or damage of a light emitting layer does not occur due to bending stress even when bending or folding a display panel is repeated. Another object of the present application is to provide a flexible electroluminescent display capable of preventing display quality from being deteriorated by a structure that robustly responds to bending stress in the light emitting layer.

A display device according to an exemplary embodiment of the present application is a flexible display device including a display area and a non-display area surrounding the display area, and includes a virtual folding axis when the flexible display device is bent or folded around the virtual folding axis. A substrate including a folding region to be used, a driving element layer formed on the substrate and including a driving element for driving a unit pixel, an insulating layer formed on the driving element layer, an insulating layer formed on the insulating layer and defining a plurality of light emitting regions a bank layer, a light emitting device formed in the light emitting region and connected to the driving device, a light emitting device and an encapsulation layer formed on the bank layer to encapsulate the display area, and first and second spacers formed between the bank layer and the encapsulation layer; and the second spacer prevents the encapsulation layer from being peeled off from the first spacer and the second spacer.

The second spacer may be further formed in the non-display area. In addition, the second spacer is characterized in that it is distributed in the folding area.

On the other hand, the second spacer is characterized in that it does not exist in the non-folding area that does not include the folding axis. In addition, the second spacer is characterized in that the length of the bottom side is smaller than the length of the upper side in the shape of an inverted tape.

The folding area and the non-folding area may include a display area and a non-display area. That is, the folding area is a concept including both the display area and the non-display area in which the folding axis is located when the virtual folding axis crosses the display device, and the non-folding area refers to the remaining area of the display device except for the folding area. Concept.

In addition, the second spacer is formed in the non-folding area that does not include the folding axis, and the second spacer is formed in the non-folding area at a density lower than that formed in the folding area.

The second spacer formed in the non-display area may have an inverted taper shape in which a length of a bottom side is smaller than a length of an upper side, and has a polygonal shape in a plan view.

In addition, the second spacer is characterized in that the plurality of second spacers form a group, and the second spacers of each group are symmetrical with the second spacers facing each other.

In addition, the second spacer is characterized in that the plane in a plan view is a triangle. In addition, it is characterized in that the second spacer is formed only in the folding area.

In addition, it is characterized in that the distribution density of the second spacer decreases in the form of a normal distribution as it moves away from the center of the folding axis.

According to the present application, it is possible to prevent peeling between a plurality of layers constituting the display panel when the display device is folded or bent by adding a spacer having a reverse tapered shape to the upper surface of the display panel. In particular, since spacers having a reverse tapered shape are formed on the bank layer and are formed in both the display area and the non-display area, bonding strength between the spacer and the encapsulation layer is strengthened. In addition, by making the formation density of the reverse-tapered spacer high in the folding region and low in the non-folding region, it can withstand the stress of folding or bending well in the folding region. Propagation to this non-folding area can be delayed.

1 is a block diagram of an electroluminescent display device according to an embodiment of the present specification.
2 is a circuit diagram of a pixel included in an electroluminescence display according to an embodiment of the present specification.
3 is a plan view of an electroluminescent display device according to an embodiment of the present specification.
4 is an enlarged plan view of area A of FIG. 3 and is a plan view illustrating some pixels.
5 is a cross-sectional view taken along the cutting line I-I' of FIG.
FIG. 6 is a cross-sectional view of region B of FIG. 3 .
7 is a conceptual diagram illustrating a spacer formed in a region B of FIG. 3 .
FIG. 8 is an enlarged plan view of FIG. 7 .
FIG. 9 is a plan view showing a form of forming the spacer of FIG. 8 .

Advantages and features of the present application, and methods for achieving them will become apparent with reference to examples described in detail in conjunction with the accompanying drawings. However, the present application is not limited to the examples disclosed below, but will be implemented in a variety of different forms, and only examples of the present application allow the disclosure of the present application to be complete, and it is common in the technical field to which the invention of the present application belongs. It is provided to fully inform those with knowledge of the scope of the invention, and the invention of the present application is only defined by the scope of the claims.

The shape, size, ratio, angle, number, etc. disclosed in the drawings for explaining an example of the present application are exemplary, and thus the present application is not limited to the illustrated matters. Like reference numerals refer to like elements throughout. In addition, in describing an example of the present application, if it is determined that a detailed description of a related known technology may unnecessarily obscure the subject matter of the present application, the detailed description thereof will be omitted.

When 'including', 'having', 'consisting', 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 case in which the plural is included is included unless otherwise explicitly stated.

In interpreting the components, it is construed as including an error range even if there is no separate explicit description.

In the case of a description of the positional relationship, for example, when the positional relationship of two parts is described as 'on', 'on', 'on', 'beside', etc., 'right' Alternatively, one or more other parts may be positioned between two parts unless 'directly' is used.

In the case of a description of a temporal relationship, for example, 'immediately' or 'directly' when a temporal relationship is described with 'after', 'following', 'after', 'before', etc. It may include cases that are not continuous unless this is used.

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

The term “at least one” should be understood to include all possible combinations of one or more related items. For example, the meaning of “at least one of the first, second, and third items” means that each of the first, second, or third items as well as two of the first, second and third items It may mean a combination of all items that can be presented from more than one.

Each feature of the various examples of the present application may be partially or wholly combined or combined with each other, technically various interlocking and driving are possible, and each example may be implemented independently of each other or may be implemented together in a related relationship. .

Hereinafter, an example of a flexible electroluminescent display according to the present application will be described in detail with reference to the accompanying drawings. In adding reference numerals to components of each drawing, the same components may have the same reference numerals as much as possible even though they are indicated in different drawings.

1 is a block diagram of an electroluminescent display device 100 according to an embodiment of the present specification.

Referring to FIG. 1 , the electroluminescent display device 100 includes an image processing unit 110 , a timing controller 120 , a data driver 130 , a gate driver 140 , and a display area 150 .

The image processing unit 110 outputs a data enable signal DE along with the data signal DATA supplied from the outside. The image processing unit 110 may output one or more of a vertical synchronization signal, a horizontal synchronization signal, and a clock signal in addition to the data enable signal DE.

The timing controller 120 receives the data signal DATA from the image processing unit 110 as well as a driving signal including a data enable signal DE or a vertical synchronization signal, a horizontal synchronization signal, and a clock signal. The timing controller 120 includes a gate timing control signal GDC for controlling the operation timing of the gate driver 140 and a data timing control signal DDC for controlling the operation timing of the data driver 130 based on the driving signal. to output

The data driver 130 samples and latches the data signal DATA supplied from the timing controller 120 in response to the data timing control signal DDC supplied from the timing controller 120 , and converts it into a gamma reference voltage and outputs it. . The data driver 130 outputs the data signal DATA through the data lines DL1 to DLn.

The gate driver 140 outputs a gate signal while shifting the level of the gate voltage in response to the gate timing control signal GDC supplied from the timing controller 120 . The gate driver 140 outputs a gate signal through the gate lines GL1 to GLm.

The display panel 150 displays an image while the pixel 160 emits light in response to the data signal DATA and the gate signal supplied from the data driver 130 and the gate driver 140 . The detailed structure of the pixel 160 will be described with reference to FIGS. 4 and 5 .

2 is a circuit diagram of a pixel included in an electroluminescence display according to an embodiment of the present specification.

Referring to FIG. 2 , the pixel of the electroluminescent display device 200 includes a switching transistor 240 , a driving transistor 250 , a compensation circuit 260 , and a light emitting device 270 .

The light emitting device 270 emits light according to a driving current formed by the driving transistor 250 .

The switching transistor 240 performs a switching operation so that the data signal supplied through the data line 230 is stored as a data voltage in the capacitor in response to the gate signal supplied through the gate line 220 .

The driving transistor 250 operates so that a constant driving current flows between the high potential power line VDD and the low potential power line GND in response to the data voltage stored in the capacitor.

The compensation circuit 260 is a circuit for compensating the threshold voltage of the driving transistor 250 , and the compensation circuit 260 includes one or more thin film transistors and a capacitor. The configuration of the compensation circuit may be very diverse depending on the compensation method.

That is, the pixel of the flexible display device 200 basically has a 2T (Transistor) 1C (Capacitor) structure including a switching transistor 240 , a driving transistor 250 , a capacitor, and a light emitting device 270 , but a compensation circuit When 260 is added, it may have various forms such as 3T1C, 4T2C, 5T2C, 6T1C, 6T2C, 7T1C, 7T2C, and the like.

3 is a plan view of an electroluminescent display device according to an embodiment of the present specification.

At this time, FIG. 3 is a state in which the flexible substrate 310 of the flexible electroluminescent display 300 is not folded or bent.

Referring to FIG. 3 , the flexible electroluminescence display 300 has an active area (A) in which pixels that actually emit light through a thin film transistor and a light emitting device are disposed on a substrate 310 that can be folded or bent. /A) and a non-active area (N/A) surrounding the edge of the display area A/A.

In the non-display area N/A, a driving circuit unit such as a gate driving unit 390 for driving the flexible electroluminescent display 300 and various signal wirings such as a scan line (S/L) may be disposed. can In addition, the driving circuit unit for driving the flexible electroluminescence display 300 is disposed on the substrate 310 in the form of a gate in panel (GIP), or a flexible substrate using a tape carrier package (TCP) or a chip on film (COF) method. It may be connected to 310 .

A pad 395 is disposed on one side of the non-display area N/A of the substrate 310 . The pad 395 is a metal pattern to which an external module is bonded.

The flexible electroluminescent display 300 having a foldable or bendable function can be folded by configuring one area of the substrate 310 as the folding area FA. For example, the electroluminescent display 300 in a folded state may be implemented by folding about a virtual folding axis crossing the central portion of the display area A/A of the substrate 310 . Accordingly, the flexible electroluminescent display 300 according to the embodiment of the present specification includes a folding area FA in which the outermost folding axis is located and a non-folding area NFA except for the folding area. The folding area FA means that the substrate 310 has a curvature at an arbitrary point of the substrate 310 while the substrate 310 is folded around an imaginary folding axis. An area is defined as a non-folding area (NFA).

Hereinafter, a configuration of a pixel according to an exemplary embodiment of the present specification will be described in detail with further reference to FIGS. 4 and 5 . 4 is a plan view illustrating a pixel structure by magnifying a partial area A of the folding area FA of the display area of FIG. 3 . FIG. 5 is a cross-sectional view taken along line A-A' of FIG. 4 .

The flexible electroluminescent display device according to the preferred embodiment of the present specification may include a substrate 501, a driving device layer DP, a light emitting device layer EP, spacers 420 and 421, and an encapsulation layer Encap.

The substrate 501 includes a plastic material or a glass material. The substrate 501 may include a transparent, opaque, or colored polyimide material. For example, the polyimide substrate 501 may be a cured polyimide resin coated to a predetermined thickness with a release layer interposed therebetween on a relatively thick carrier substrate. In this case, the carrier substrate is separated from the substrate 501 through a laser release process. Since the polyimide substrate 501 separated from the carrier substrate is very thin, a back plate may be further coupled to the rear surface of the substrate 501 . The back plate maintains the substrate 501 in a planar state. The back plate according to an example of the present specification may include a plastic material, for example, a polyethylene terephthalate material.

Meanwhile, the substrate 501 according to another example may be a flexible glass substrate. For example, the glass substrate 501 is a thin glass substrate having a thickness of 100 micrometers (㎛) or less, or a carrier glass substrate etched to have a thickness of 100 micrometers (㎛) or less by a substrate etching process can be

The substrate 501 is preferably made of a material having excellent flexibility that can be freely folded or unfolded. The substrate 501 may include a display area AA and a non-display area IA surrounding the display area AA.

A buffer layer 502 may be formed on the upper surface of the substrate 501 . The buffer layer 502 functions to prevent moisture, etc. from penetrating into the driving device layer DP from the outside. The buffer layer 502 is deposited on one surface of the substrate 501 . The buffer layer 502 may be formed of a plurality of inorganic layers alternately stacked. For example, the buffer layer 502 may be formed as a multilayer in which an inorganic layer selected from among a silicon oxide layer (SiOx), a silicon nitride layer (SiNx), and a silicon oxynitride layer (SiON) is alternately stacked. The buffer layer may be omitted if necessary.

The driving device layer DP is a layer in which driving devices constituting the pixel are formed. The driving device layer DP may include a gate electrode constituting the thin film transistor, source/drain electrodes, an active layer, and an insulating layer insulating therebetween.

The thin film transistor is provided in each of the plurality of pixels formed in the display area A/A of the substrate 501 and the gate driver 390 formed in the non-display area N/A of the substrate 501 .

In the thin film transistor according to an example, the active layer 503 , the gate insulating film 504 , the gate electrode 505 formed on the gate insulating film 504 , the interlayer insulating film 506 and the interlayer insulating film formed on the gate electrode 505 . and source/drain electrodes 507a and 507b formed on 506 . Here, the thin film transistor shown in FIG. 5 may be a driving thin film transistor electrically connected to the light emitting device.

Although the thin film transistor shown in FIG. 5 illustrates a top gate (top gate) structure in which the gate electrode 505 is positioned on the active layer 503 , the present invention is not limited thereto. As another example, the thin film transistor has a lower gate (bottom gate) structure in which the gate electrode 505 is located below the active layer 503 or the gate electrode 505 is located both above and below the active layer 503. It may have a double gate structure.

The active layer 503 may be formed on the substrate 501 or the buffer layer 502 . The active layer 503 is made of a semiconductor material, and may include a silicon-based, oxide-based, or organic-based semiconductor material, and may have a single-layer or multi-layer structure. The active layer 503 is an intrinsic semiconductor layer formed between the source/drain regions 503a and 503c having improved conductivity by doping the semiconductor material with impurity ions and the source and drain regions 503a and 503c. A channel layer 503b is formed. may include

A light blocking layer (not shown) for blocking external light incident to the active layer 503 may be added between the substrate 501 and the active layer 503 .

A gate insulating film 504 is formed over the entire substrate 501 to cover the active layer 503 . The gate insulating layer 504 may be formed of, for example, a single layer or multiple layers of an inorganic layer such as a silicon oxide layer (SiOx) or a silicon nitride layer (SiNx).

The gate electrode 505 is formed on the gate insulating film 504 to overlap the active layer 503 . The gate electrode 505 may be formed together with the gate line GL. The gate electrode 505 according to an exemplary embodiment may include one of molybdenum (Mo), aluminum (Al), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium (Nd), and copper (Cu). It may be formed as a single layer or multiple layers made of any one or an alloy thereof.

An interlayer insulating film 506 is formed over the entire substrate 501 to cover the gate electrode 505 and the gate insulating film 504 . The interlayer insulating film 506 provides a flat surface on the gate electrode 505 and the gate insulating film 504 .

The source electrode 507a and the drain electrode 507b are formed on the interlayer insulating film 506 to overlap the active layer 503 with the gate electrode 505 interposed therebetween. The source electrode 507a and the drain electrode 507b are formed together with the data line DL. In addition, a pixel driving power supply line VDD (not shown) providing a driving voltage to the pixels and a common power supply wiring VSS (not shown) providing a common voltage to each pixel may be formed together with the source/drain electrodes. . That is, each of the source/drain electrodes 507a and 507b, the data line DL, the pixel driving power line VDD, and the common power line VSS may be simultaneously formed when the source/drain electrode material is patterned.

Of course, the pixel driving power wiring VDD and the common power supply wiring VSS may be formed of different materials on a layer different from that of the source/drain electrodes.

Each of the source electrode 507a and the drain electrode 507b is connected to the active layer 503 through an electrode contact hole penetrating the interlayer insulating film 506 and the gate insulating film 504 .

The source electrode 507a and the drain electrode 507b include molybdenum (Mo), aluminum (Al), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium (Nd), and copper (Cu). ) may be formed as a single layer or multiple layers made of any one or an alloy thereof. Here, the source electrode 507a may be electrically connected to the pixel driving power line VDD.

As described above, the thin film transistor formed on the substrate 501 constitutes a driving circuit for driving a unit pixel. Also, the gate driver 390 disposed in the non-display area of the substrate 501 may include a thin film transistor identical to or similar to a thin film transistor provided in a pixel.

The planarization layer 508 is an organic layer that covers the driving device layer DP including the thin film transistor formed on the substrate 501 and planarizes the surface of the driving device layer. The planarization layer 508 according to an example may include an organic material such as an acrylic resin, an epoxy resin, a phenolic resin, a polyamide resin, or a polyimide resin. It can be formed into a film.

The planarization layer 508 is formed to be much thicker than the plurality of inorganic thin films constituting the driving device layer DP to planarize the driving device layer DP, and the driving device layer DP and the light emitting device layer formed thereon. It also serves to suppress parasitic capacitors that may occur between (EP).

The planarization layer 508 may include a pixel contact hole PH for exposing the drain electrode 507b of the thin film transistor provided in the driving device layer DP.

A light emitting device layer EP may be disposed on the planarization layer 508 . The light emitting device layer EP includes a bank defining a light emitting device and an area in which the light emitting device is to be formed, and a plurality of spacers positioned on the bank.

A bank layer 510, also called a pixel defining layer, is disposed on the planarization layer 508 to define a light emitting area of a pixel in the display area A/A.

The light emitting device includes a pixel driving electrode 509 , a common electrode 512 opposed thereto, and a light emitting layer 511 interposed between the two layers.

The pixel driving electrode 509 is formed on the planarization layer 508 and is electrically connected to the drain electrode 507b of the driving thin film transistor through the pixel contact hole PH provided in the planarization layer 508 . In this case, the bank layer 510 covers the edge of the pixel driving electrode 509 , and the central portion of the pixel driving electrode 509 is opened as an open region from which the bank layer 510 is removed, so that the pixel driving electrode 509 is exposed. . That is, the bank layer 510 made of an organic layer defines a light emitting region as an open region in which the middle portion of the pixel driving electrode 509 is removed, and charges the light emitting layer formed in the region where the pixel driving electrode 509 is exposed. can be authorized.

In a top emission type electroluminescent display device in which the light emission direction faces the upper surface of the substrate, the pixel driving electrode 509 may include a metal material having a high reflectance. For example, the pixel driving electrode 509 may have a stacked structure of aluminum (Al) and titanium (Ti) (Ti/Al/Ti), a stacked structure of aluminum (Al) and ITO (ITO/Al/ITO), and APC ( Ag/Pd/Cu) alloy, and a multilayer structure such as an APC alloy and a laminate structure of ITO (ITO/APC/ITO), or silver (Ag), aluminum (Al), molybdenum (Mo), gold (Au) , magnesium (Mg), calcium (Ca), and barium (Ba) may have a single-layer structure made of any one material or two or more alloy materials.

The light emitting layer 511 is deposited in the open area defined by the bank layer 510 . That is, the emission layer 511 may cover the pixel driving electrode 509 exposed by the open area and side banks of the open area. In some cases, the emission layer 511 may be deposited on the pixel driving electrode 509 , the side surface of the bank layer 510 near the open region, and a portion of the top surface of the bank layer 510 .

In this case, a fine metal mask (FMM) may be used to deposit the emission layer 511 in the open region of the bank. That is, the organic light emitting layer 511 is deposited on the open area of the bank by a deposition method. At this time, in order to accurately define the deposition position of the light emitting layer 511, a metal fine mask having a hole corresponding to the open area of the bank is used. It is aligned with the bank layer 510 and a light emitting organic material is deposited.

The process of aligning the fine metal mask (FMM) and the bank layer 510 and depositing the light emitting layer is a very precise process. A spacer 420 is formed thereon. The spacer 420 serves to support the fine metal mask FMM when the fine metal mask FMM is aligned on the bank layer 510 . The spacer 420 will be described in more detail below.

The light emitting layer 511 according to an example may include any one of a blue light emitting unit, a green light emitting unit, and a red light emitting unit for emitting color light corresponding to a color set in the pixel. Meanwhile, the emission layer 511 may include any one of an organic emission layer, an inorganic emission layer, and a quantum dot emission layer, or a stacked or mixed structure of an organic emission layer (or an inorganic emission layer) and a quantum dot emission layer.

Additionally, the light-emitting layer 511 may further include a functional layer for improving the light-emitting efficiency and/or lifespan of the light-emitting layer 511 .

The common electrode 512 is formed to be electrically connected to the emission layer 511 . The common electrode 512 is formed over the entire display area AA of the substrate 501 to be commonly connected to the emission layer 511 provided in each sub-pixel.

The common electrode 512 according to an example may include a transparent conductive material capable of transmitting light or a semi-transmissive conductive material. When the common electrode 512 is formed of a transflective conductive material, emitting efficiency of light emitted from the light emitting device may be increased through a micro-cavity structure. The transflective conductive material according to an example may include magnesium (Mg), silver (Ag), or an alloy of magnesium (Mg) and silver (Ag). Additionally, a capping layer may be further formed on the common electrode 512 to improve light output efficiency by adjusting the refractive index of light emitted from the light emitting device.

A spacer according to an example of the present specification will be described with reference to FIG. 4 . The spacer includes a first spacer 420 and a second spacer 421 . The first spacer 420 and the second spacer 421 are disposed between sub-pixels constituting the unit pixel.

In each of the sub-pixels, sub-pixels of red 410R, blue 410B, and green 410G constitute one unit pixel. The unit pixel may be configured by adding white sub-pixels in addition to red, green, and blue.

A formation region of the sub-pixels is defined by the bank layer 430 defining an open region, respectively. A pixel driving electrode, which may be an anode electrode, is disposed on a bottom surface of each sub-pixel.

Referring to FIG. 4 , a first spacer 420 is disposed between sub-pixels. The first spacer 420 forms a fine metal mask so that when the red, green, and blue light emitting layers are deposited in the open area defined by the bank layer, the light emitting layer corresponding to each color is precisely aligned with the open area and deposited. It serves to align and support. That is, before the light emitting layer is deposited, the fine metal mask is first aligned with the bank in which the open region is formed. At this time, the first spacer 420 supports the fine metal mask so that the bank and the fine metal mask can be aligned while maintaining a constant distance. do.

The first spacer 420 has a positively tapered organic material protrusion pattern in which the length of the bottom side is longer than the length of the top side.

The first spacer 420 is usually made of the same material as the material constituting the bank layer 430 . Therefore, after depositing a material constituting the bank layer, it can be patterned and formed through a photolithography process using a halftone mask.

The first spacers 420 may be disposed on the bank layer at a constant density. That is, one or more may be formed while being formed between the red, green, and blue sub-pixels.

A second spacer 421 may be disposed between each sub-pixel. The second spacer 421 may be the same as that of the first spacer 421 in material, but have different functions. That is, when the foldable display device is folded, the second spacer 421 is used to prevent the layers from being peeled off due to the stress generated between the layers constituting the display device.

When the foldable display device is folded, peeling occurs easily between the bank layer and the encapsulation layer formed thereon. In order to prevent this, the second spacer 421 has a reverse tapered shape in which the length of the bottom side is smaller than the length of the top side, thereby increasing the bonding force when the encapsulation layer is coupled to the second spacer 421 . That is, the second spacer 421 is engaged with the encapsulation layer (Encap) as if locking a zipper to prevent peeling.

Like the first spacer 420 , the second spacer 421 may be formed of an organic material layer such as a bank layer. Accordingly, the bank layer and the first and second spacers may be formed at a time by a halftone process after depositing one organic layer.

Referring to FIG. 4 , the second spacer 421 is integrally formed between the red sub-pixel 410R and the blue sub-pixel 410B and between the green sub-pixel 410G and the blue sub-pixel 410B. It is formed in a truncated shape. However, the formation position and shape of the second spacer 421 is not limited to the example of FIG. 4 .

Referring to FIG. 5 , the second spacer 421 represents the cross-sectional shape of the second spacer 421 of FIG. 4 , and is formed on the bank layer 510 in a reverse tapered shape.

The second spacer 421 serves to prevent the encapsulation layer Encap from being peeled off from the bank layer 510 by stress generated when the flexible display device is folded by bonding with the encapsulation layer Encap formed thereon. do.

On the other hand, the second spacer 421 also serves as a path through which cracks propagate once peeling occurs. That is, the reverse tapered spacer serves to prevent peeling between adjacent layers, but once peeling occurs, the cracks easily propagate laterally through the inverted tape-shaped spacer. Accordingly, it is not desirable to increase the density of the second spacer 421 to be formed in order to prevent separation between two adjacent layers.

Accordingly, in the exemplary embodiment of the present specification, the second spacers 421 are formed with different densities in the folding area FA and the non-folding area NFA. That is, the second spacer 421 makes the density formed in the folding area FA higher than the density formed in the non-folding area NFA to better withstand the folding stress in the folding area FA. Nevertheless, if cracks occur in the folding area FA, it is possible to prevent the generated cracks from spreading to the non-folding area NFA.

Non-folding area Since the folding area NFA is an area in which stress is not generated due to the folding of the display panel, it is also possible that the second spacer 421 having an inversely tapered shape may not be formed in the non-folding area NFA.

Meanwhile, in the case of a rollable display device as another modified example of the foldable display device, the entire display area may be a folding region. Accordingly, in this case, the non-folding area NFA may not exist in the rollable display device, and thus the second spacer 421 may be formed in the entire display area of the rollable display device.

In the flexible display device of the present embodiment, the second spacer 421 is added to counteract the stress generated when the display substrate is folded, and the second spacer 421 is formed not only in the display area but also in the non-display area. lose That is, the encapsulation layer (Encap) is formed not only in the display area but also in the non-display area. In order to prevent peeling between the encapsulation layer and the bank layer, a second spacer is provided in the entire area where the bank layer and the encapsulation layer are combined as much as possible. In addition, peeling is suppressed when the display device is folded.

Hereinafter, the encapsulation layer Encap and the second spacer formed in the non-display area will be described in detail with reference to FIGS. 5 and 6 .

The encapsulation layer (Encap) is a layer that encapsulates the light emitting device layer to prevent external moisture or oxygen from penetrating into the light emitting device layer (EP). Accordingly, the encapsulation layer Encap is formed to cover both the upper surface and the side surface of the light emitting device layer EP.

The encapsulation layer (Encap) according to an example may be formed by alternately depositing an inorganic layer and an organic layer. 5 and 6 illustrate examples in which the first inorganic encapsulation layer PAS1, the organic encapsulation layer PCL, and the second inorganic encapsulation layer PAS2 are sequentially deposited.

The first inorganic encapsulation layer PAS1 and the second inorganic encapsulation layer PAS2 according to an example may include silicon nitride, aluminum nitride, zirconium nitride, titanium nitride, hafnium nitride, tantalum nitride, silicon oxide, aluminum oxide, or titanium oxide. It may consist of inorganic substances of

The organic encapsulation layer PCL is surrounded by the first inorganic encapsulation layer PAS1 and the second inorganic encapsulation layer PAS2 . The organic encapsulation layer PCL is relatively thicker than the first inorganic encapsulation layer PAS1 and/or the second inorganic encapsulation layer PAS2 to adsorb and/or block particles that may be generated during the manufacturing process. can be formed with The organic encapsulation layer PCL may be formed of an organic material such as silicon oxycarbon (SiOCz) acrylic or epoxy-based resin. The organic encapsulation layer PCL may be formed by a coating process, for example, an inkjet coating process or a slit coating process.

Since the encapsulation layer Encap is deposited on the light emitting device layer EP, the first inorganic encapsulation layer PAS1 is deposited while making contact with the common electrode layer 512 .

Since the encapsulation layer (Encap) functions to seal the light emitting device layer (EP) to protect the light emitting device layer from external moisture or oxygen, the first inorganic encapsulation layer (PAS1) in direct contact with the common electrode layer 512 is It is necessary to precisely and strongly bond with the common electrode layer 512 .

In general, the first inorganic encapsulation layer PAS1 is deposited by a chemical vapor deposition method, but may also be deposited by an atomic layer deposition method. According to the atomic layer lamination method, since the first inorganic encapsulation layer PAS1 can be deposited on the common electrode layer in atomic units, the common electrode layer 512 and the first inorganic encapsulation layer PAS1 can be combined very precisely.

The first inorganic encapsulation layer PAS1 is deposited while in direct contact with the common electrode layer 512 .

Meanwhile, since the common electrode layer 512 is deposited on the bank layer on which the spacers are formed, the common electrode 512 may cover the spacers. However, although the first spacer 420 is covered by the common electrode layer 512 , the second spacer 421 has a reverse tapered shape, so that the common electrode layer 512 does not completely cover the second spacer 421 . That is, while the common electrode layer 521 is deposited on the spacer and bank layer 510 , it cannot be completely deposited on the second spacer 421 having an inverted taper shape, but may be deposited while being cut off on the side and top surfaces of the second spacer 421 . have. As a result, the first inorganic encapsulation layer PAS1 deposited on the common electrode layer 512 may be directly contacted with and coupled to the second spacer 421 having an inverse tapered shape. The first inorganic encapsulation layer PAS1 made of an inorganic material is more strongly coupled to the organic second spacer 421 than the metallic common electrode layer 512 . Therefore, it is possible to prevent the encapsulation layer Encap from being peeled from the light emitting device layer EP due to the stress generated when the foldable display device is folded by the coupling of the first inorganic encapsulation layer PAS1 and the second spacer 421. can

An organic encapsulation layer PCL and a second inorganic encapsulation layer PAS2 are sequentially deposited on the first inorganic encapsulation layer PAS1 to complete the encapsulation layer Encap.

Referring to FIG. 6 , in the present embodiment, the second spacer 421 is further formed in the non-display area of the folding area.

The display panel includes a display area A/A and a non-display area N/A surrounding the display area while being disposed outside the display area, including a planarization layer 508 , a bank layer 510 , and an encapsulation layer ( Encap) extends beyond the display area to the non-display area.

Referring to FIG. 6 , the display area is substantially the same as that shown in FIG. 5 . However, FIG. 6 further discloses the configuration of the non-display area.

A gate driver that transmits a gate signal to driving devices of the display area is disposed in the non-display area N/A, and reference numeral T-gip indicates one transistor disposed in the gate driver.

On the gate driver, a planarization layer 508 extending from the display area, a bank layer 510 formed on the planarization layer 508 , a second spacer 421 formed on the bank layer 510 , and a second spacer 421 , An encapsulation layer Encap including the first inorganic encapsulation layer PAS1 directly contacted and bonded is formed. The encapsulation layer Encap includes a first inorganic encapsulation layer PAS1 , a second inorganic encapsulation layer PAS2 , and an organic encapsulation layer PCL interposed therebetween.

The first inorganic encapsulation layer PAS1 and the second inorganic encapsulation layer PAS2 are formed to extend to the ends of the substrate.

A dam for preventing the organic encapsulation layer PCL from spreading is further formed at the edge of the substrate. The dam 630 surrounds the display area at the edge of the substrate by overlapping one or more of the planarization layer, the bank layer, and the spacer layer.

Also, referring to FIG. 6 , a common power wiring (VSS) 620 that can be formed simultaneously with the source and drain electrodes is formed on the interlayer insulating layer 506 in the non-display area. The common power wiring (VSS) 620 is a wiring that applies a common voltage to the common electrode 512 and is connected to the common electrode (VSS) through a common electrode connection wiring 610 that may be formed of the same material as the pixel driving electrode 509 at the same time. 512) are connected.

Referring to FIG. 6 , a second spacer 421 is formed on the bank layer 510 in the non-display area of the folding area. The second spacer 421 may be formed over the gate driver or at any point in the non-display area.

The second spacer 421 is made of the same material as the bank layer 510 and may be formed together when the bank layer 510 is formed. Of course, it is also possible to form the second spacer 421 of a material different from that of the bank layer 510 through a separate process.

The second spacer 421 formed in the non-display area will be described in more detail with reference to FIGS. 7 to 9 .

In this embodiment, the second spacer 421 may be further formed in the non-display area N/A of the folding area FA. The second spacer 421 has a reverse tapered shape and is combined with an encapsulation layer formed in the non-display area to prevent separation between layers constituting the display panel.

The stress generated when the display panel is folded is concentrated around the virtual folding axis. That is, the closer to the folding axis, the greater the folding stress, so that the second spacer 421 is concentrated in the non-display area of the folding area. In particular, distribution is possible to decrease toward the non-folding area around the folding axis. It can be arranged to achieve a normal distribution around the folding axis. In general, since stress is applied to the substrate while forming a normal distribution about the folding axis, if the second spacer 421 is disposed to achieve a normal distribution, the folding stress can be effectively counteracted.

The second spacer 421 is disposed to improve a problem that various layers constituting the display panel may be peeled off due to the folding stress. When the folding stress does not act, the second spacer 421 is disposed. may not Accordingly, the second spacer 421 may not be installed in the non-folding area NFA.

However, the second spacer 421 may be installed in the non-folding area, and may have the following purposes and effects. The second spacer 421 strengthens the bonding force between the bank layer and the encapsulation layer to prevent peeling against the folding stress. can have a preventive effect. Accordingly, the second spacers 421 are formed in both the folding area and the non-folding area, but have different distribution densities. That is, the density of the distribution of the second spacers 421 per unit area is made higher in the folding area than in the non-folding area to counteract the stress acting around the folding axis, and the bonding force between the encapsulation layer and the bank layer is improved over the entire substrate. .

However, as in a rollable display, when the entire display panel is a folding area, the second spacers 421 may be evenly distributed over the entire display area and the non-display area with different densities.

The cross-sectional structure of the second spacer 421 may have a trapezoidal shape and an inverted taper shape in which the length of the bottom side is smaller than the length of the top side, but the shape of the plan view may vary.

8 and 9 , in the second spacer 421, a plurality of triangular-shaped unit spacers are gathered to form a group. The embodiment of FIG. 8 illustrates that four triangular-shaped unit spacers are gathered to form one group. The unit spacers are arranged so that the vertices are gathered toward the center of each group. This is to effectively block propagation of cracks to neighboring regions when cracks occur. That is, the second spacer 421 has a reverse tapered shape and can strengthen bonding with the encapsulation layer, but when cracks occur, they easily propagate to neighboring regions. However, if a group is formed with spacers having a triangular shape in plan view and the triangular spacers are configured to gather toward the center of each group, the lateral propagation path of the crack can be dispersed.

9 shows the configuration of the second spacer 421 of various types. 9A to 9D illustrate that a plurality of second spacers 421 are gathered to form one group. 9(a) to 9(c) are configured such that a plurality of spacers are symmetrical with each other facing each other. 9( d ) is a case in which the spacers facing each other are not symmetrical, but the vertices gather toward the center of the group.

The embodiments of FIG. 9 are only exemplary embodiments, and when cracks are generated due to peeling of respective layers of the display panel, a configuration is possible to block propagation of the cracks. Propagation of cracks is possible by randomly distributing possible second spacers 421 . In addition, since the side surfaces of the second spacer 421 are configured such that a specific path does not occur with each other, propagation of cracks may be blocked.

Although the embodiments of the present invention have been described in more detail with reference to the accompanying drawings, the present invention is not necessarily limited to these embodiments, and various modifications may be made within the scope without departing from the spirit of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical spirit of the present invention, but to explain, and the scope of the technical spirit of the present invention is not limited by these embodiments. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. The protection scope of the present invention should be construed by the claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

100, 200, 300: electroluminescent display device
110: image processing unit
120: timing controller
130: data driver
140: gate driver
150: display panel
160: pixel
220: gate line
230: data line
240: switching transistor
250: drive transistor
260: compensation circuit
270, 410R, 410G, 410B: light emitting device
420: first spacer
421: second spacer
310, 501: substrate
370: link wiring
390: gate driver
395: pad
502: buffer layer
503: active layer
504: gate insulating layer
505: gate electrode
506: interlayer insulating layer
507a, 507b: source/drain electrodes
508: planarization layer
509: pixel driving electrode
510: bank layer
511: light emitting layer
512: common electrode
530: cover window
610: pixel connection wiring
620: common electrode connection wiring
630: dam

Claims (12)

A flexible display device comprising: a display area and a non-display area surrounding the display area;
a substrate including a folding area including a virtual folding axis when the flexible display device is bent or folded about the virtual folding axis;
a driving element layer formed on the substrate and including a driving element for driving a pixel;
an insulating layer formed on the driving device layer;
a bank layer formed on the insulating layer and defining a plurality of light emitting regions;
a light emitting device formed in the light emitting region and connected to the driving device;
an encapsulation layer formed on the light emitting device and the bank layer to encapsulate the display area; and
a first spacer and a second spacer formed between the bank layer and the encapsulation layer;
The second spacer prevents the encapsulation layer from peeling off the bank layer. The flexible display device of claim 1 , wherein the second spacer is further formed in the non-display area. The flexible display device of claim 2 , wherein the second spacers are distributed in the folding area. The flexible display device of claim 3 , wherein the second spacer does not exist in a non-folding area that does not include the folding axis. The flexible display device of claim 1 , wherein the second spacer has an inverted taper shape in which a length of a bottom side is smaller than a length of an upper side. The flexible display device of claim 3 or 4, wherein the folding area and the non-folding area include the display area and the non-display area. 4. The method of claim 3, wherein the second spacer is formed in a non-folding area that does not include the folding axis, and the second spacer is formed in the non-folding area at a density lower than a density formed in the folding area. flexible display device. The flexible display device of claim 2 , wherein the second spacer formed in the non-display area has an inverted taper shape having a bottom side shorter than an upper side length and has a polygonal shape in plan view. The flexible display device of claim 8 , wherein a plurality of second spacers form a group in the second spacer, and the second spacers of each group are symmetrical with second spacers facing each other. The flexible display device of claim 9 , wherein the second spacer has a triangular shape in a plan view. The flexible display device of claim 8 , wherein the second spacer is formed only in the folding area. The flexible display device of claim 8 , wherein the distribution density of the second spacer decreases in a normal distribution as it moves away from the folding axis.

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